This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by van der Eerden, B. C. J. Articles by Wit, J. M. Search for Related Content PubMed PubMed Citation Articles by van der Eerden, B. C. J. Articles by Wit, J. M.

Systemic and Local Regulation of the Growth Plate

Departments of Pediatrics (B.C.J.v.d.E., M.K., J.M.W.) and Endocrinology and Metabolic Diseases (M.K.), Leiden University Medical Center, 2300 RC Leiden, The Netherlands

Correspondence: Address all correspondence and requests for reprints to: Prof. Dr. J. M. Wit, Department of Pediatrics, Leiden University Medical Center, J6-S, P.O. Box 9600, 2300 RC Leiden, The Netherlands. E-mail: J.M.Wit{at}lumc.nl

	Abstract

Top Abstract I. The Growth Plate II. Longitudinal Growth III. Hormonal Regulation IV. Local Regulation V. Growth Plate Regulation... VI. Conclusions and Perspectives References

 
The growth plate is the final target organ for longitudinal growth and results from chondrocyte proliferation and differentiation. During the first year of life, longitudinal growth rates are high, followed by a decade of modest longitudinal growth. The age at onset of puberty and the growth rate during the pubertal growth spurt (which occurs under the influence of estrogens and GH) contribute to sex difference in final height between boys and girls. At the end of puberty, growth plates fuse, thereby ceasing longitudinal growth. It has been recognized that receptors for many hormones such as estrogen, GH, and glucocorticoids are present in or on growth plate chondrocytes, suggesting that these hormones may influence processes in the growth plate directly. Moreover, many growth factors, i.e., IGF-I, Indian hedgehog, PTHrP, fibroblast growth factors, bone morphogenetic proteins, and vascular endothelial growth factor, are now considered as crucial regulators of chondrocyte proliferation and differentiation. In this review, we present an update on the present perception of growth plate function and the regulation of chondrocyte proliferation and differentiation by systemic and local regulators of which most are now related to human growth disorders.

I. The Growth Plate

A. Structural organization

B. Extracellular matrix proteins

II. Longitudinal Growth

A. Growth disorders

B. Catch-up growth

III. Hormonal Regulation

A. GH-IGF-I system

B. Thyroid hormone

C. Glucocorticoids

D. Estrogens

E. Androgens

F. Intracrinology

IV. Local Regulation

A. Indian hedgehog

B. PTH-related peptide

C. Fibroblast growth factors

D. Bone morphogenetic proteins/transforming growth factor ß

E. Vascular endothelial growth factor

V. Growth Plate Regulation after Birth and Interactions between Hormonal and Local Mechanisms

A. Local growth plate regulation after birth

B. Interactions between hormonal and local regulation

VI. Conclusions and Perspectives

	I. The Growth Plate

Top Abstract I. The Growth Plate II. Longitudinal Growth III. Hormonal Regulation IV. Local Regulation V. Growth Plate Regulation... VI. Conclusions and Perspectives References

 
THE GROWTH PLATE is a highly organized cartilage structure entrapped between the epiphyseal and metaphyseal bone at the distal ends of the long bones. Longitudinal growth takes place by a process called endochondral ossification, in which a cartilaginous scaffold is replaced by bone in a coordinated fashion. The growth plate can be divided into horizontal zones of chondrocytes at different stages of differentiation (Fig. 1) (Ref. 1).

View larger version (58K): [in this window] [in a new window]   FIG. 1. Functional organization of the growth plate. See text for details.

At the epiphyseal end of the growth plate, the reserve zone, also called germinal or stem cell zone, contains the resting chondrocytes. These cells have recently been shown to be crucial for orientation of the underlying columns of chondrocytes and therefore unidirectional bone growth, probably by secreting a growth plate-orienting factor (6). Upon some unknown trigger, the stem cells enter into the proliferating zone. In this matrix-rich zone, the flattened chondrocytes undergo cell divisions in a longitudinal direction and organize in a typical columnwise orientation. They synthesize substantial amounts of extracellular matrix (ECM) proteins, which are essential for the structure of the growth plate matrix. At a given moment, either by a finite number of cell divisions or by changes in exposure to a local growth factor (for example PTHrP; see Section IV.B) (7, 8), proliferating chondrocytes lose their capacity to divide and start to differentiate and become prehypertrophic, coinciding with an increase in size. Their location is called the transition zone. They then further progress in the differentiation pathway to become hypertrophic chondrocytes, which have a round appearance and secrete large amounts of matrix proteins. This stage is characterized by an increase in intracellular calcium concentration. This is essential for the production of matrix vesicles, which are small membrane-enclosed particles that are released from chondrocytes (9, 10). They contain large amounts of annexins, which mediate calcium uptake into the matrix vesicles (11, 12). The vesicles secrete calcium-phosphates, hydroxyapatite, and matrix metalloproteinases (MMPs), resulting in mineralization of the vesicles and their surrounding matrix. The mineralization process, in combination with low oxygen tension, attracts blood vessels from the underlying primary spongiosum (13). Subsequently, the mineralized chondrocytes undergo programmed cell death (apoptosis), leaving a scaffold for new bone formation. The apoptotic process is, among other factors, regulated by elevated intracellular calcium levels (leading to activation of proteases, lipases, and nucleases), retinoic acids, and vitamin D (12, 14, 15, 16, 17). In particular, vitamin D deficiency resulting in childhood rickets is associated with failure of growth plate calcification, vascularization, and subsequent decrease in bone formation, phenomena that have also been observed in rachitic mice (18, 19). Longitudinal and transverse septae, which keep the chondrocytes in a columnwise orientation, are resorbed by chondroclasts or osteoclasts from the underlying primary spongiosum (20, 21). At the same time, osteoblasts enter the area to lay down new metaphyseal trabecular bone. The combination of chondrocyte proliferation, the enlargement of maturing chondrocytes in the hypertrophic zone, and the production of ECM are the major contributors to longitudinal bone growth.

B. Extracellular matrix proteins
The chondrocytes are embedded in a surrounding matrix (ECM), which provides support to the chondrocytes and consists of ECM molecules, ECM remodeling enzymes, and various growth factors. The first group of ECM molecules consists of the collagens, of which types II, IX, and X are expressed predominantly in the proliferating, prehypertrophic, and hypertrophic zones, respectively, and are pivotal for the integrity of the ECM (22). Additionally, they play an essential role in sequestering various growth factors involved in the regulation of chondrocyte proliferation and differentiation. Gene mutations in type II, IX, or X collagens have been associated with disturbances of the cartilage matrix causing spondyloepiphyseal dysplasia and hypochondriasis, multiple epiphyseal dysplasia, or Schmid metaphyseal chondrodysplasia, respectively (23, 24, 25, 26). These dysplasias are all associated with short stature (Table 1).

Communication exists between the ECM and cellular responses within the chondrocyte through cell surface adhesion receptors, known as integrins. They mediate the attachment of the chondrocytes to the surrounding ECM macromolecules, thereby increasing the integrity of the growth plate (28).

Furthermore, there is a group of ECM-remodeling enzymes, known as MMPs and their inhibitors (tissue inhibitor of MMP). These play a crucial role in the remodeling and degradation of the ECM and are involved in the preservation of the ECM integrity and the initiation of angiogenesis (29, 30). Mice lacking MMP-9, for instance, display abnormal growth plate vascularization and bone formation (31), whereas disruption of tissue inhibitor of MMP-1 in mice increases basement membrane invasiveness of primitive mesenchyme (precursor of chondrocyte) cells in vitro (32). Moreover, MMP-13 (collagenase-3) has been shown to be crucial for remodeling of the matrix in the transition zone of the growth plate (33). Inhibition of MMP-13 inhibits degradation of collagen II, which is predominant in the proliferating zone and suppresses the expression of collagen X, which is the major collagen of the hypertrophic zone (33). The ECM also functions as a reservoir of various growth factors that may be released and may influence chondrocyte function when the ECM is degraded. Moreover, the ECM may control the diffusion capacity of growth factors, including fibroblast growth factors (FGFs) and hedgehogs, which will be discussed later.

The role of the ECM is crucial for the integrity of cartilage and for normal longitudinal growth, but the interaction between collagens, MMPs, integrins, and the multitude of growth factors within the ECM is still far from understood.

	II. Longitudinal Growth

Top Abstract I. The Growth Plate II. Longitudinal Growth III. Hormonal Regulation IV. Local Regulation V. Growth Plate Regulation... VI. Conclusions and Perspectives References

 
Longitudinal bone growth is the result of chondrocyte proliferation and subsequent differentiation in the epiphyseal growth plates of the long bones. It is regulated by a multitude of genetic and hormonal factors, growth factors, environment, and nutrition (34, 35, 36, 37, 38). All of these contribute to establishing the final height of an individual. There are at least three distinct endocrine phases of linear growth during postnatal life in man. A high growth rate is observed from fetal life, with a rapid deceleration up to about 3 yr of age. The second phase is characterized by a period of lower, slowly decelerating growth velocity up to puberty. The last phase, puberty, is characterized by an increased rate of longitudinal growth until the age of peak height velocity has been reached. Then, growth velocity rapidly decreases due to growth plate maturation in long bones and spine, leading to growth plate fusion and cessation of longitudinal growth (39, 40). Recently, the process and moment of growth plate fusion has been elegantly studied by Turner and co-workers (41), who determined the number of bony bridges between the epiphysis and metaphysis by microcomputed tomography in rats between 2 and 25 months of age. Although it is generally believed that cessation of growth succeeds growth plate fusion, this has recently been disputed by Parfitt (42). He observed cessation of growth of a metacarpal in a patient with pseudohypoparathyroidism, which was followed later by fusion of the growth plate. In support of this, a recent study in aged rats has shown that, despite cessation of growth, growth plates still exist with sporadic chondrocyte proliferation (43). Many studies, including those with transgenic mice models, have provided useful information concerning growth velocity and timing of puberty in humans and sexual maturation in rodents, which will be mentioned in the sections dealing with the various hormones and growth factors influencing these processes.

A. Growth disorders
Disturbances of longitudinal bone growth occur quite frequently with a high diversity in etiology. In Table 1, causes of short and tall stature are summarized, some of which are discussed here. Both short and tall stature disorders are divided into primary (defect presumed in bone/cartilage), secondary (defect located outside bone/cartilage), or idiopathic (cause unknown) growth disorders (44).

Short or tall stature does not necessarily lead to clinical problems during childhood and puberty, but psychosocial problems may occur in this vulnerable period of life. Examples are social withdrawal, practical problems relating to clothing and shoes, fear about future compatible partners and career planning, and (only in case of tall stature) a kyphotic posture (45).

B. Catch-up growth
Many systemic diseases impair longitudinal bone growth. Interestingly, after remission, growth often accelerates beyond the normal growth rate for that particular age, a phenomenon called catch-up growth (reviewed in Ref. 46). This has been observed in many growth-retarding conditions such as Cushing syndrome (47), hypothyroidism (48), celiac disease (49), anorexia nervosa/malnutrition (47), and GH deficiency (46).

To explain catch-up growth, it was originally believed that a mechanism exists in the brain that compares the actual body size with an age-appropriate set point and adjusts the growth rate accordingly, and this is termed "sizo-stat" (50). This neuroendocrine hypothesis was challenged by an experimental study in the rabbit. In this experiment, dexamethasone was infused by an osmotic minipump directly in the tibial growth plate, which slowed bone growth of the treated leg but not of the contralateral vehicle-treated leg (51). When dexamethasone infusion was abrogated, tibial bone growth was not just normalized but even increased compared with the contralateral leg, thereby demonstrating catch-up growth (51). Based on these findings, Gafni and Baron (52) proposed that the underlying mechanism for catch-up growth was intrinsic to the growth plate, also termed growth plate hypothesis. A mechanism explaining catch-up growth may be that a maximum number of cell divisions exist for growth plate chondrocytes and that at each cell division the proliferation rate decreases, a process termed senescence. Growth retardation reduces chondrocyte proliferation, leaving them less senescent; when remission takes place, these cells have a greater proliferating potential, explaining the increased growth rate compared with the unaffected growth plate. This was recently supported by im estrogen injections in rabbits resulting in a more rapid senescence of growth plate chondrocytes, causing proliferative exhaustion and earlier growth plate fusion compared with nontreated rabbits (53). Still, these studies have all been performed in animals, and their pattern of catch-up growth is quite different from that of humans. For example, in a child who catches up, height velocity can be four times that of normal growth, whereas in rats and rabbits the growth velocity increment is minimal. To date, additional studies are required in humans to generate a more solid and satisfactory hypothesis for the process of catch-up growth (46, 54).

	III. Hormonal Regulation

Top Abstract I. The Growth Plate II. Longitudinal Growth III. Hormonal Regulation IV. Local Regulation V. Growth Plate Regulation... VI. Conclusions and Perspectives References

 
The major systemic hormones that regulate longitudinal bone growth during childhood are GH and IGF-I, thyroid hormone (T₃ and T₄), and glucocorticoids (GC), whereas during puberty the sex steroids (androgens and estrogens) contribute a great deal to this process. For most hormones the effects on longitudinal growth and final height have been accurately described, but many of the molecular mechanisms underlying these effects have remained unclarified to date. In this review, the focus lies on the hormonal effects on longitudinal growth during childhood and puberty. For each hormone, important clinical data will be presented, followed by crucial in vitro and in vivo data from animal studies. The role of genetic factors, environmental influences, and nutrition on longitudinal bone growth should not be underestimated, but they will not be discussed here.

A. GH-IGF-I system
Before birth, IGF-I and -II are believed to be the key regulators of growth, and largely independent of GH. This is based on findings in knockout mice, as well as on experiments of nature in the human; in congenital GH deficiency, birth length is only mildly diminished, whereas in the boy with congenital IGF deficiency birth size was severely diminished (55). After birth, GH is an important modulator of longitudinal bone growth and appears, together with IGF-I, the central player of the hypothalamus-pituitary-growth plate axis. GH secretion from the pituitary is tightly controlled by the activity of GHRH (stimulator) and somatostatin (inhibitor), which are released by the hypothalamus. With the discovery of ghrelin, the endogenous ligand with similar actions as the synthetic GH secretagogues (GHS) developed earlier, and the GHS receptor, a new physiological dimension in the regulation of GH secretion has arisen (56). Despite the increased complexity, it has become apparent that GHS acts synergistically with GHRH on GH release, making it a promising therapeutic strategy for GH-deficiency disorders (57). GH is secreted in a pulsatile fashion, which is more regular with higher peak levels in boys, whereas in girls GH secretion is more irregular (58). A pituitary adenoma in childhood or adulthood causes enhanced GH secretion, leading to pituitary gigantism or acromegaly, respectively (Table 1) (59, 60). Conversely, defects in the formation of GH-secretory cells (e.g., by Prop-1 or Pit-1 mutations), synthesis or release of GH (e.g., by GHRH-receptor or Pit-1 mutations, GH-gene deletions, and other forms of GH deficiency), or GH insensitivity, including defects in the GH receptor (GHR) and IGF-I deletion, all result in severe dwarfism (Table 1) (61, 62, 63, 64, 65).

1. Hypotheses for the action of GH and IGF-I on longitudinal growth.
GH acts on its target tissue either directly or through two intermediates: IGF-I and IGF-II. They were called insulin-like due to their similarity in structure and activity compared with insulin. IGF-II is essential for normal embryonic growth (66), whereas IGF-I is a ligand that has a continuous function throughout development and adulthood (67). The role of IGF-II after birth remains less clear, especially because there are clear species differences in IGF-II expression after birth in bone. There is now substantial evidence that both IGFs have a unique and complementary role in regulating bone growth (68). According to the somatomedin-hypothesis by Salmon and Daughaday (69) in 1957, GH stimulates somatomedin (IGF-I) synthesis in the liver, which in turn activates chondrocyte proliferation in the growth plate, thereby achieving longitudinal growth. It was not until the mid-1980s that several studies challenged this view, including the finding that local GH injection stimulates tibial bone growth significantly, whereas the contralateral tibia did not show this increase (70). The findings by Isaksson et al.(70) were corroborated by two additional studies in rats, demonstrating increased tibial bone growth after local GH or IGF-I injection compared with the contralateral vehicle-injected tibia (71, 72). Interestingly, it was demonstrated that local injection of GH regulates the number of chondrocytes expressing IGF-I in rats (73).

In analogy to the proposed dual-effector theory in adipocytes by Green et al. (74), Isaksson and co-workers used cultured growth plate chondrocytes to show that GH acts on resting zone chondrocytes and is responsible for local IGF-I production, which stimulates clonal expansion of proliferating chondrocytes in an autocrine/paracrine manner (75). Partly in agreement with the dual-effector theory but also contradictory to it, Hunziker et al. (76) showed that in hypophysectomized rats, stem cell cycle times reduced with either GH or IGF-I administration. In addition, proliferating cell cycle time and the duration of the hypertrophic phase were reduced. It was concluded that besides GH, IGF-I was also capable of stimulating growth plate stem cells, albeit to a lesser extent (76, 77).

In support of direct effects of GH on the growth plate, GHR was demonstrated on chondrocytes in rabbit and human growth plates (78, 79). Only very recently, both GHR and GH binding protein (GHBP) were also found in rat growth plate chondrocytes during postnatal development (80). Interestingly, the expression of GHR and GHBP in the growth plate was regulated by hypophysectomy, GH, T₃, T₄, and dexamethasone, which all affect longitudinal growth (80). Another interesting finding was that administration of GH increased the width of the germinal zone in mice deficient for IGF-I (igf-1 null mice), further substantiating a direct role for GH on the growth plate (81).

Besides GH, IGF-I plays an important role in longitudinal bone growth during prenatal and postnatal life because knockout mice for IGF-I show, among other phenotypes, severe dwarfism (67, 82), and a child with a homozygous IGF-I deletion had extremely short stature (Table 1) (55). GH treatment had no effect on longitudinal growth and body weight in IGF-I deficiency in both humans and mice (55, 83). In addition, mice with an inactivated GHR gene, a potential model for Laron syndrome (Table 1), and a double knockout mouse for GHR and IGF-I were generated (84, 85). The GHR/IGF-I double mutants were smaller than either GHR or IGF-I single mutant, indicating that both GH and IGF-I contribute significantly to longitudinal growth. Further analysis of these mice demonstrated that IGF-I is the major determinant of both embryonic and postnatal growth and that IGF-I expression is modulated by GH in the postnatal period (83, 84, 85). In support of this, using IGF-I and IGF-II knockout as well as GH-deficient lit/lit mice, Mohan et al. (86) elegantly showed that GH/IGF-I but not IGF-II was critical for puberty-induced bone growth. In addition, it was demonstrated that during prepuberty the effect of IGF-I on bone accretion was mediated via GH-dependent mechanisms, whereas during puberty IGF-I exerts both GH-dependent and independent effects on bone accretion.

2. Contribution of systemic vs. local IGF-I to longitudinal growth.
Recent molecular approaches have been used to further examine the relative contribution of systemically and locally produced IGF-I on longitudinal growth. Using the LoxP-Cre recombination system, liver-specific igf-1 gene-deleted mice were generated, resulting in mRNA levels for IGF-I less than 1% of the levels in wild-type animals (87). These mice had greatly reduced serum IGF-levels as expected (25% of normal), but surprisingly they demonstrated similar growth rates compared with wild-type mice, despite elevated GH levels (88, 89). Based on these findings, the "Somatomedin hypothesis 2000" was proposed in which the liver was excluded from the somatotrophic axis (68). Still, challenges can be made against this model, because 25% of normal serum IGF-I, unaltered free IGF-I, and elevated GH serum levels may be sufficient to maintain normal growth (90). In addition, the liver-specific knockout of IGF-I may have been incomplete during the earliest time period when growth rates were still high (4 wk of age), whereas body growth had almost come to an end by the time the knockout was complete (89). In a recent study, double gene disrupted mice for liver IGF-I and the acid-labile subunit were generated, resulting in even lower serum IGF-I levels (91). These mice revealed reduced linear growth and decreased bone mineral density, suggesting that a threshold concentration of IGF-I is necessary for normal bone growth and bone density (91).

3. Localization of the IGF system in the growth plate.
It remains unclear to what extent local IGF-I contributes to longitudinal growth. A few reports have demonstrated IGF-II, but not IGF-I in growth plate chondrocytes (92, 93). Interestingly, igf-1 null mice show a 30% decrease in linear dimension of the terminal hypertrophic chondrocytes, suggesting a role for IGF-I in the regulation of chondrocyte hypertrophy but not in proliferation (81). From these findings, Le Roith et al. (68) proposed a working mechanism in which IGF-II, controlled by GH, was involved in the regulation of chondrocyte proliferation, whereas IGF-I was responsible for chondrocyte differentiation. However, there is still debate about IGF-I localization in the growth plate. IGF-I and -II mRNA have been demonstrated in hypertrophic chondrocytes in mice postnatally (94), but in growth plates of fetal cows both mRNAs were detected in proliferating chondrocytes 5- to 32-fold higher than in hypertrophic chondrocytes (95). In another report, IGF-I mRNA has been demonstrated in proliferating chondrocytes of mouse growth plates (85). Finally, in rats, IGF-I was detected in all zones of the growth plate, with the highest expression levels in the proliferating and the prehypertrophic chondrocytes (73, 96). Adding to the complexity of IGF action in the growth plate, the expression of IGF-IR and -IIR as well as IGF binding proteins (IGFBP)-1 to -6 have also been studied in chondrocytes. In fetal cows, transcripts were detected for IGF-IR and IGFBP-2 to -5, with reduced expression of IGFBP-3 to -5 in hypertrophic chondrocytes (95). Furthermore, IGF-II, both IGF receptors, and IGFBP-5 and -6 are coexpressed during early murine chondrogenesis, suggesting functional interactions between them (93). Moreover, IGFBP-3 and -5 have been demonstrated in rabbit costal chondrocytes (97). In another study, IGFBP-2 and -5 were present in developing chicken limbs, of which IGFBP-2 was proposed to be an inducer of chondrocyte maturation in vitro (98).

These findings in combination with the data from the knockout studies necessitate further research to delineate the exact working mechanism of the somatotrophic axis in the regulation of longitudinal growth.

B. Thyroid hormone
Besides GH, T₃ and, to a lesser extent, its precursor T₄ are crucial for normal bone maturation (36, 99). Both congenital hypothyroidism and T₃ deficiency are associated with severe growth retardation in rodents and humans (Table 1) (100, 101, 102, 103). Hyperthyroidism causes an increased growth velocity in children but also leads to premature growth plate fusion and short stature (104, 105). These findings were recently underscored in thyroid hormone receptor (TR)ß mutant mice harboring a targeted resistance to thyroid hormone (106). In agreement with these observations, double knockout mice for both TRs (TR1 and ß) display retarded growth and bone maturation (107). However, the single knockouts for TR1 or ß do not show this phenotype, indicating rescue effects in the single knockout mice, in which loss of one receptor can be compensated by the other (108, 109). Despite affected longitudinal growth, the phenotype of the double knockout is much milder compared with that in mice with severe hypothyroidism. This might be explained by the ability of TRs to bind thyroid hormone response elements and modulate gene transcription, even in the absence of ligand (107).

Besides indirect effects of thyroid hormones on longitudinal growth, for example by influencing GH secretion (100, 107), actions of T₃ are at least partially direct, because TR1 and ß proteins have both been demonstrated in stem cells and early proliferating chondrocytes of rat and human growth plates (110, 111). T₃ seems to stimulate the recruitment of cells to the proliferating zone from the germinal zone and facilitate the differentiation of growth plate chondrocytes, in chicken chondrocytes, and in rat mandibular condyle and femur organ cultures (112, 113, 114). Its precursor, T₄, has been shown to increase the number of [³H]methylthymidine-labeled chondrocyte nuclei and [³⁵S] incorporation in Snell dwarf mice growth plates, suggesting a stimulatory role on both chondrocyte proliferation and differentiation (115). Recent data have confirmed that T₄ induces the expression of both type II and X collagen, the activity of the differentiation marker alkaline phosphatase, and chondrocyte hypertrophy (116). Furthermore, T₄ but not GH is capable of completely reverting reduced widths of the proliferating and hypertrophic zone, as well as a disturbed growth plate architecture and vascular invasion of the growth plate in hypothyroid rats (117), further establishing a unique role for thyroid hormones in the regulation of bone growth and maturation.

Besides influencing GH secretion, thyroid hormones have been shown to interact with the GH-IGF-I pathway at the level of the growth plate. In the 1980s, T₃ was shown to promote proliferation of embryonic chicken chondrocytes by enhancing IGF-I mRNA expression. Also in cultured rat epiphyseal chondrocytes, T₃ stimulated IGF-I mRNA expression (112, 118). In addition, we have recently shown that T₃/T₄ can regulate GHR expression, in vivo in rat growth plates (80). In summary, thyroid hormones act through chondrocytes bearing TRs to modulate growth plate proliferation, differentiation, and vascular invasion. Part of these effects appear to be mediated by modulating local GH and/or IGF-I actions.

C. Glucocorticoids
Various clinical conditions, such as juvenile rheumatoid arthritis, chronic asthma, and post renal transplantation, require prolonged GC therapy, leading among other phenomena to decreased bone volume and growth retardation (119). In contrast, familial GC deficiency is associated with tall stature (Table 1) (120).

Dexamethasone treatment inhibited chondrocyte proliferation and matrix synthesis, suggesting that GC is a potent negative regulator of chondrogenesis (121). Early evidence for a direct effect of GC in the growth plate came from a study in which local dexamethasone infusion considerably reduced tibial growth compared with the contralateral vehicle-injected leg (51).

A few studies have now localized the GC receptor (GR) in rat bone cells, including chondrocytes (122), and in human growth plates, especially in hypertrophic chondrocytes, suggesting direct effects of GC on the growth plate (123).

Recently, GR was demonstrated in the proliferating and hypertrophic zone of rat growth plates, and treatment with high doses of corticosterone in rats caused a reduced growth plate width in long bones, concomitant with growth retardation (124). These findings are most likely explained by reduced chondrocyte proliferation, already demonstrated by Annefeld (121) but recently also in prepubertal mice (125), in combination with increased apoptosis in terminal hypertrophic chondrocytes (126, 127).

GC have been shown to suppress growth by modifying the GH-IGF-I pathway at different levels. Besides inhibiting the release of GH from the pituitary, GC reduce IGF-I, GHR, and IGF-IR mRNA in growth plates but also inhibit basal and IGF-I induced DNA synthesis (125, 128, 129, 130). In addition, dexamethasone induced an increase in the number of IGF-IR expressing chondrocytes in mice growth plates (131). In rabbit costal chondrocytes, dexamethasone suppressed IGFBP-5 expression, a mediator of mitogenic activity of IGF-I, but up-regulated IGFBP-3, a growth inhibitor, at the same time, suggesting that differential regulation of IGFBPs could account in part for dexamethasone-induced growth arrest (97). Only very recently was it shown in rats that dexamethasone down-regulates GHR and GHBP expression in the tibial growth plate (80). GC are also capable of modulating (local) thyroid hormone levels. It has been shown that GC regulate deiodinase activity in rat kidney and liver (132, 133), and based on the expression of deiodinase in the growth plate (134), GC may contribute to the control of T₃ levels within the growth plate. Apparently, GC cause growth retardation, not only through direct effects via the GR but also by interference with other growth-modulating pathways.

D. Estrogens
It has long been established that sex steroids are important for longitudinal growth, especially during puberty. It was generally assumed that in girls, estrogen was the primary sex steroid regulating pubertal growth, whereas in boys this was achieved primarily by androgen. The finding of a unique male patient with an inactivating mutation in the classical estrogen receptor (ER) fundamentally changed this view (135). This patient, who was resistant to the actions of estrogens, demonstrated longitudinal growth into adulthood resulting in tall stature due to absence of growth plate fusion as well as severe osteoporosis, despite high levels of testosterone (T) (Table 1) (135). In support of these findings, a similar phenotype was found in two male patients with an aromatase p450 deficiency (Table 1) (136, 137). Aromatase, encoded by the CYP19 gene, catalyzes the conversion of androgens into estrogens. Moreover, although data are limited, the pubertal growth spurt seemed to be absent in all three patients (135, 136, 137). For the estrogen-resistant patient, no suitable treatment was available, but administration of conjugated estrogen (Premarin) to the patients with aromatase deficiency led to growth plate fusion and enhanced accrual of bone mass within 6 months (138). These findings have led to the assumption that in both boys and girls, estrogen is the main determinant for the puberty-associated phenomena related to longitudinal growth and bone quality (139, 140).

1. In vivo studies.
Whereas in humans an obvious growth spurt occurs during puberty and growth plate fusion at the end of it, rodents do not clearly demonstrate these phenomena during sexual maturation. Still, after sexual maturation in rats and mice, longitudinal growth diminishes resulting in growth rates approaching zero. In humans, the growth spurt is probably caused by low estrogen levels (in combination with elevated GH secretion), whereas growth plate fusion is mediated by the exclusive action of higher levels of estrogen, demonstrating that estrogen (above a certain concentration) is an inhibitor of longitudinal growth. This became evident from findings in patients with a mutation in the ER and aromatase genes (135, 136, 137).

Rats tend to respond in a similar fashion to estrogen: removal of estrogen by ovariectomy (OVX) stimulates longitudinal growth, whereas estrogen treatment inhibits this, although rats do not close their growth plate until late in life (141, 142, 143). In support of this role for estrogen, ovariectomized immature rabbits treated with either estrogen or the selective ER modulator raloxifene showed reduced chondrocyte proliferation and growth plate height and accelerated growth plate senescence (144). This study also showed that raloxifene acts as an estrogen antagonist on the growth plate in rabbits. In contrast, OVX in mice causes no change in nose-to-tail length compared with their sham-operated controls (145). Still, in both rats and mice a decrease in bone density, cancellous bone area, and bone strength is observed, whereas increases are observed in bone turnover and radial bone growth (141, 145). Interestingly, several studies in hypophysectomized rats have shown that estrogen can inhibit longitudinal growth in the absence of GH (142, 146, 147). This suggests that in rats estrogen can inhibit growth independently of GH, possibly by directly influencing the activity of growth plate chondrocytes. In agreement with these data, patients with Laron syndrome demonstrate a pubertal growth spurt and epiphyseal fusion, despite having a defect in the GHR (148).

A number of studies have now demonstrated both ER and ERß in growth plate chondrocytes during development and in several species, indicating that estrogens can have direct effects on chondrocytes (149, 150, 151, 152, 153, 154, 155, 156, 157). Slight species differences in ER/ß distribution in the growth plate might explain the observed discrepancies in growth responses and growth plate fusion to estrogen.

The actual longitudinal growth of an individual is achieved through activity of chondrocyte proliferation and differentiation within the growth plate. Indeed, after OVX in rats, bone length and growth plate thickness increased (143, 158), which was associated with an increased immunostaining for proliferating cell nuclear antigen, a marker for dividing cells (143). The opposite occurred in orchidectomized mice and rats (143, 159, 160). There is conflicting evidence on the role of estrogen during chondrocyte differentiation. In one study, it was reported that estrogen decreased matrix synthesis, contributing to the age-related decline in longitudinal growth (161). On the other hand, chondrocyte differentiation was shown to be increased by estrogen, as determined by [³⁵S] uptake in rabbit and human cultured chondrocytes (162, 163). In summary, besides indirect effects, estrogen exerts direct effects on growth plate morphology and physiology through ER and ERß, but their exact role in chondrocyte proliferation and (terminal) differentiation necessitates further clarification.

2. Knockout models.
In the last decade, a number of animal models have been developed to study the regulation of longitudinal growth by sex steroids, including the ovariectomized rat, knockout mice for ER (ERKO), ERß (BERKO), and both ERs (DERKO), and the aromatase knockout mouse (141, 164, 165, 166). However, in ovariectomized as well as female estrogen-resistant ERKO mice, longitudinal growth is either unaffected or inhibited, which is contrary to the patient with the ER mutation (145, 167). Similar to the ERKO mouse, the male aromatase knockout mouse is also stunted in its longitudinal growth, which does not fit with the increased longitudinal growth in patients with aromatase deficiency (136, 137, 168). Vidal et al. (165) have extensively studied skeletal growth and maturation in male ERKO, BERKO, and DERKO mice. In this study, all parameters studied in the various ER knockouts, i.e., longitudinal growth, growth plate width, radial skeletal growth, serum levels of osteocalcin and IGF-I were decreased in the ERKO and DERKO mice but were unaltered in the BERKO mice (165). In two other studies (169, 170), however, female BERKO mice demonstrated increased femur lengths compared with wild type, which correlated with increased serum IGF-I levels. Apparently, ERß is involved in abrogating the effects on longitudinal growth mediated by ER. Furthermore, species differences may account for discrepancies between findings in the human and rat and those in mice.

E. Androgens
Despite the established role for estrogen as the primary modulator of pubertal growth, androgens also play a specific role. A few studies have assessed the effect of the administration of nonaromatizable androgens [dihydrotestosterone (DHT), a metabolite of T and the synthetic androgens fluoxymesterone and oxandrolone] on longitudinal growth in boys with constitutionally delayed growth. Longitudinal growth and ulnar length significantly increased without advancement of bone age, suggesting that androgen specifically stimulated longitudinal growth (171, 174). Moreover, DHT has been shown to increase longitudinal bone growth in 3-month-old rats (173) and increased [³⁵S] incorporation in cartilage of growing rabbits during sexual maturation (162). T has also been described to increase body weight gain, body length, and growth plate width in mice, rats, and humans but it remains difficult to distinguish between the androgenic and estrogenic (after conversion) effect of T on these parameters (145, 174). However, local injection of supraphysiological amounts of T increased growth plate width compared with the vehicle-injected contralateral leg (175). These findings were corroborated in the mandibular condyle in vitro and in hypophysectomized and castrated rats, in which administration of T caused increased IGF and IGF-IR expression but also tibial growth plate width (176, 177). Thus, androgen appears to have stimulatory effects on longitudinal growth, independently of estrogen action and by influencing local mechanisms in chondrocytes.

Using a cre-lox conditional knockout strategy, Yeh et al. (178) reported the generation of androgen-receptor (AR) knockout (ARKO) mice. Besides other androgen-dependent phenotypes, the osteopenic phenotype of male ARKO mice strongly supports an important role of AR signaling in bone metabolism. By generating a bone-specific ARKO mouse, valuable information can be gathered about the precise role of androgens in bone.

Androgens are thought to play a pivotal role in the masculinization of the skeleton and may do so by influencing the somatotrophic axis (58, 179). However, direct effects on cartilage are likely, because a high-affinity AR has been detected in rat costochondral chondrocytes (180). Furthermore, AR has been localized in hypertrophic chondrocytes of the human costochondral junction and in growth plates from human tibiae derived from surgery for corrective osteotomy (181, 182). AR mRNA and protein were recently demonstrated in the tibial growth plate of the rat (183). The differences in subcellular AR expression between males and females around sexual maturation suggests a role for T in establishing sex differences in longitudinal growth during sexual maturation (183). Taken together, these studies suggest that, besides estrogens, androgens also can directly influence processes in the growth plate and that they may account for some skeletal differences between males and females.

F. Intracrinology
Originally, it was thought that peripheral organs obtained their sulfated and nonsulfated sex steroids from the circulation. Both androgens and estrogens are derived from cholesterol by a series of enzymatic steps taking place in the gonads and to a lesser extent in the adrenals (Fig. 2) (184, 185). Among the steroidogenic enzymes are steroid sulfatase, which catalyzes the formation of dihydroepiandrosterone (DHEA) and estrone (E₁) from the sulfated precursors, DHEA sulfate and E₁-S, and sulfotransferase, which catalyzes the opposite direction. DHEA is converted into androstenedione (A) by 3ß-hydroxysteroid dehydrogenase (HSD). Furthermore, type I 17ß-HSD converts A into T and E₁ into 17ß-estradiol (E₂), whereas type II catalyzes the conversion in the opposite direction. Aromatase mediates the conversion of the androgens A and T into the estrogens, E₁ and E₂. Finally, type I 5-reductase irreversibly converts T into DHT (Fig. 2).

View larger version (25K): [in this window] [in a new window]   FIG. 2. Enzymes involved in the synthesis of sex steroids. See text for details.

There is some evidence that steroidogenic enzymes are also present in bone cells. In primary cultures of rat osteoblasts, rat and human osteoblastic cell lines, and spongiosa obtained from patients undergoing orthopedic surgery, mRNA expression and bioactivity of the enzymes aromatase, type I and II 17ß-HSD, steroid sulfatase, and type I 5-reductase have been demonstrated (188, 189, 190, 191, 192, 193). Moreover, using in situ hybridization and immunohistochemistry, Sasano et al. (194) have localized aromatase mRNA and protein and type I 17ß-HSD immunoreactivity in lining cells and osteoblasts in sections of 16 human tibiae. This finding was confirmed for aromatase in a study by Oz et al. (195). In the same study, aromatase immunopositive chondrocytes were detected in the femoral growth plate. In a recent study, aromatase, type I 17ß-HSD, steroid sulfatase, type II 17ß-HSD, and 5-reductase mRNA and bioactivity of the former three enzymes were detected in rat tibial growth plates (196). The data indicated that sex steroid metabolism occurs in the growth plate, especially around sexual maturation and thereafter. Perhaps during puberty in humans aromatase is up-regulated within the growth plate, thereby providing a mechanism to increase local estrogen levels, which may contribute to growth plate fusion at the end of puberty. Summarizing, these studies indicate that intracrinology may occur in the growth plate, thereby providing an additional mechanism to modulate local estrogen levels within the growth plate.

	IV. Local Regulation

Top Abstract I. The Growth Plate II. Longitudinal Growth III. Hormonal Regulation IV. Local Regulation V. Growth Plate Regulation... VI. Conclusions and Perspectives References

 
New insights into local regulation of chondrocyte activity in the growth plate mostly come from studies in transgenic mice revealing crucial roles of various growth factors in growth regulation in the embryonic growth plate (reviewed in Ref. 38). Besides IGF-I, the most important locally acting growth factors influencing longitudinal growth that have been identified are Indian hedgehog (Ihh), PTHrP, FGFs, bone morphogenetic proteins (BMPs), and vascular endothelial growth factor (VEGF). Many other factors such as vitamin D metabolites (197, 198, 199), retinoids (200), leptin (201, 202, 203, 204, 205), chondromodulin (206), C-type natriuretic protein (207), prostaglandins (198), hepatocyte growth factor (208), and Wnt proteins (209) contribute to local processes in the growth plate but are not discussed here. It has become increasingly clear that the same factors are also operational in growth plate regulation after birth with slight modifications. As such, these mechanisms are prime targets for regulation by hormones involved in longitudinal growth regulation, which will be discussed in Section V.

A. Indian hedgehog
Ihh belongs to the family of hedgehog proteins, which are morphogens that play crucial roles in embryonic patterning and development. Hedgehogs bind to a receptor called patched (Ptc), thereby releasing smoothened (Smo), a membrane protein with an intrinsic intracellular activity that is abrogated by Ptc in the absence of hedgehogs. Releasing Smo results in its conformational change and a downstream signal to activate its intracellular targets (210, 211, 212). Ihh was found to be expressed in prehypertrophic chondrocytes of chicken and mouse fetal long bones (213, 214). Ihh has been recognized as a regulator of the pace of chondrocyte differentiation. Misexpression of Ihh in chicken long bones blocked chondrocyte differentiation (213). In a more recent study using Ihh-null mutant mice, apart from reduced chondrocyte differentiation as judged by histology and reduced collagen X expression, two additional roles for Ihh in endochondral ossification were revealed (215). The knockout mice showed dwarfism and exhibited markedly reduced chondrocyte proliferation but also failure of osteoblast development (215). Although Ihh regulated the pace of chondrocyte differentiation through the activity of PTHrP signaling (see Section IV.B), PTHrP was not able to rescue the effect on chondrocyte proliferation in mice with an Ihh null mutation. This indicated that Ihh regulation of chondrocyte proliferation occurs independently of PTHrP signaling (216). These data identify Ihh as a coordinator of endochondral ossification, regulating chondrocyte proliferation and differentiation and osteoblast differentiation, and coupling chondrogenesis to osteogenesis (Fig. 3) (215, 216).

View larger version (60K): [in this window] [in a new window]   FIG. 3. Interaction of Ihh, PTHrP, BMP, and FGF signaling in modulating chondrocyte proliferation and differentiation during prenatal endochondral bone formation. Ihh is expressed by chondrocytes making the transition from a proliferating into a hypertrophic phenotype. Expression of Ihh at this stage is up-regulated by BMPs but inhibited by FGFs. Ihh activates adjacent chondrocytes and diffuses toward the lateral perichondrium, where it can bind to its receptor Ptc. Via an as yet unknown mechanism, PTHrP production is stimulated in the periarticular perichondrium. Then, PTHrP diffuses toward the prehypertrophic zone, which expresses high levels of PTH/PTHrP receptors and inhibits the differentiation of proliferating chondrocytes to cells capable of synthesizing Ihh. Besides modulating chondrocyte differentiation, Ihh also stimulates chondrocyte proliferation, both directly and indirectly (through BMP signaling). FGFs are able to inhibit chondrocyte proliferation independently of the two stimulatory pathways. BMP signaling inhibits terminal differentiation of chondrocytes, a process that FGFs can promote. The balance between BMP and FGF signaling seems to be crucial in regulating proliferation, Ihh expression, and terminal differentiation of chondrocytes.

PTHrP is expressed abundantly in the embryonic periarticular perichondrium in mouse, rat, and chicken (213, 227, 228). Its receptor at that stage is detected in late proliferating and early hypertrophic chondrocytes (213, 229). As mentioned before, Ihh misexpression causes inhibition of chondrocyte differentiation but also induces PTHrP expression in the perichondrium, suggesting that Ihh is an upstream positive regulator of PTHrP (216). Indeed, in Ihh knockout mice, PTHrP expression in cartilage is virtually absent (215). Based on these findings, Vortkamp et al. and Lanske et al. (213, 221) proposed a model for a locally acting growth-restraining feedback loop, which controls the level of PTHrP in the growth plate. In this model, Ihh is expressed by chondrocytes making the transition from a proliferating into a hypertrophic phenotype. Ihh activates adjacent chondrocytes and diffuses toward the lateral perichondrium, where it can bind to its receptor Ptc. Via an as yet unknown mechanism, PTHrP production is stimulated in the periarticular perichondrium. Then, PTHrP diffuses toward the prehypertrophic zone, which expresses high levels of PTH/PTHrP receptors and inhibits differentiation of proliferating chondrocytes to cells capable of synthesizing Ihh (Fig. 3). Because Ihh and PTHrP are not expressed in close proximity to each other and the ECM surrounding chondrocytes allows only limited diffusion of growth factors, intermediates may play a role between Ihh and PTHrP signaling and vice versa.

C. Fibroblast growth factors
The family of FGFs constitutes at least 22 members that interact with at least four receptors (FGFR) and are major regulators of embryonic bone development (230, 231). Both FGF1 and -2 as well as FGFR1, -2, and -3 are expressed in chondrocytes (232, 233, 234, 235). In humans, activating mutations in the FGFR3 cause achondroplasia (Table 1), the most common type of human dwarfism (97% of mutations have a Gly to Arg mutation in codon 380) (236, 237, 238). Other forms of chondrodysplasia due to mutations in the FGFR3 gene include hypochondroplasia, a milder form of dwarfism and two severe types, SADDAN (severe achondroplasia with developmental delay and acanthosis nigricans), and thanatophoric dysplasia (Table 1) (239, 240). Conversely, mice with an inactivating mutation in the FGFR3 gene demonstrate increased longitudinal growth (241, 242). In addition, overexpression of FGF2 slows longitudinal growth (243). Only very recently, mice lacking FGF18 have been generated. These mice demonstrated a phenotype similar to that observed in mice lacking FGFR3, including expanded proliferating and hypertrophic zones, increased proliferation, differentiation, and Ihh signaling (244). In addition, FGF18 deficiency leads to delayed ossification and decreased expression of osteogenic markers, not seen in the FGFR3 knockout phenotype, which prompted the authors to suggest that FGF18 coordinates chondrogenesis and osteogenesis through FGFR3 and -2, respectively (244). In addition, FGF18 appeared to act as a physiological ligand for FGFR3 in the growth plate. These studies indicate that FGFR signaling reduces growth by inhibiting proliferation and differentiation (Fig. 3).

Mancilla et al. (245) studied the effects of FGF2 on chondrocyte differentiation in a metatarsal organ culture system and found three growth-inhibiting mechanisms for FGF2: decreased growth plate chondrocyte proliferation, decreased cellular hypertrophy, and at high concentrations, decreased synthesis of cartilage matrix. Recently, a mouse model for thanatophoric dysplasia characterized by severe dwarfism was used to study the relationship between FGF signaling and the Ihh/PTHrP feedback loop (246). In these newborn mice with an activated FGFR3, Ihh and PTHrP mRNA expression were both down-regulated. In the same study, embryonic metatarsals from wild-type mice were cultured in the presence of FGF2, and similar results were found. Interestingly, FGF inhibited chondrocyte proliferation by down-regulating Ihh expression. Moreover, FGF and PTHrP signals independently inhibited chondrocyte differentiation. It was concluded that FGFR3 and PTHrP/Ihh signals act through two integrated parallel pathways that mediate both overlapping and distinct functions during longitudinal bone growth (246). In a recent study by Minina et al. (8), using a limb culture system, it was found that FGF and BMP signaling are antagonistic in the regulation of chondrocyte proliferation and in Ihh expression and the process of hypertrophic differentiation. The balance between the two adjusts the pace of the differentiation process to the proliferation rate (Fig. 3) (8).

D. Bone morphogenetic proteins/transforming growth factor ß
The family of BMPs is comprised of at least 15 members, which are all part of the TGFß superfamily. BMPs were originally identified as stimulators of bone formation but are now recognized as important regulators of growth, differentiation, and morphogenesis during embryology (247). Within the developing limb cartilage elements, BMP2, -4, and -7 have been detected in the perichondrium, whereas BMP6 was found in prehypertrophic and hypertrophic chondrocytes (248, 249, 250, 251, 252, 253). In addition, BMP7 was detected in chick sternal prehypertrophic and mice metatarsal proliferating chondrocytes (252, 253).

The effects of BMPs are mediated by two type I receptors, BMPRIA and -IB, which heterodimerize with the type II receptor, BMPRII. The type I receptors are differentially localized in embryonic limbs; BMPRIB is detected in early mesenchymal condensations and is involved in early cartilage formation, whereas BMPRIA expression is confined to prehypertrophic chondrocytes (254). Constitutive active and/or dominant negative forms of BMPRIA and -IB revealed that the type IA receptor controls the pace of chondrocyte differentiation, whereas the type IB receptor is involved in cartilage formation and cell death (apoptosis) (254).

Because various BMPs are expressed in chondrocytes, cartilage defects may be anticipated in BMP-related disorders in mice (255). Mice bred with homozygous null mutations in BMP2 and -4 are not compatible with life (256, 257), whereas other family members such as growth and differentiation factor 5 (GDF5) and BMP5 are important mediators of chondrocyte differentiation in mesenchymal condensations at various sites (258, 259, 260, 261). In addition, mice carrying a targeted disruption of BMPRIB show defects in proliferation of prechondrogenic cells and chondrocyte differentiation in the phalangeal region (262). Additional BMPRIB/GDF5 and BMPRIB/BMP7 double knockout studies revealed that GDF5 is a ligand for BMPRIB and that in the absence of BMPRIB, BMP7 plays an essential role in appendicular skeletal development (262). In humans, only a few mutations in members of the TGFß superfamily cause cartilage disorders. Genomic mutations in the human GDF5 gene have been shown to cause chondrodysplasia Grebe type, acromesomelic chondrodysplasia Hunter Thompson type, and brachydactyly type C, all of which are mainly characterized by defects of the limbs, with increasing severity toward the distal regions (263, 264, 265). Several mutations in the BMP antagonist noggin result in proximal symphalangism and multiple synostoses syndrome (266).

Recently, BMP6 was introduced as a possible mediator in the growth-restraining feedback loop involving Ihh and PTHrP (252). The fact that BMPRIA is expressed in the same region and that it has been shown to be critical for chondrocyte hypertrophy further strengthens an autocrine/paracrine role for BMP6 in prehypertrophic chondrocytes (254, 267). Still, the BMP6 knockout mouse hardly has any phenotype, leaving little evidence for an important physiological role for BMP6 in chondrocyte differentiation (268). This was underscored by Minina et al. (269), who elegantly showed that BMPs do not act as a secondary signal of Ihh to induce PTHrP expression or to delay the onset of hypertrophic differentiation (Fig. 3). Despite this, they showed that normal chondrocyte proliferation requires parallel signaling of both Ihh and BMPs and that BMPs are capable of inhibiting chondrocyte differentiation independently of the Ihh/PTHrP pathway (269).

In another study, inhibition of chondrocyte differentiation by TGFß was shown to be at least partly mediated by induction of PTHrP expression (270). In a second study by the same group, it was established that Shh, a functional substitute for Ihh, stimulates expression of TGFß2 and -3 in mouse metatarsals and that TGFß2 signaling is required for inhibition of differentiation and regulation of PTHrP expression by Shh (271). They concluded that TGFß2 acts as a signal relay between Ihh and PTHrP in the regulation of chondrocyte differentiation (274). These data imply that the BMPs/TGFß and their receptors act as a signaling system, both dependently and independently of the Ihh/PTHrP feedback loop, at different levels during embryonic bone formation (Fig. 3).

E. Vascular endothelial growth factor
VEGF is a chemoattractant for endothelial cells and is one of the most important growth factors for endothelial cells (272). During chondrocyte hypertrophy, ECM surrounding the hypertrophic cells becomes calcified, which triggers the invasion of blood vessels from the underlying metaphyseal bone. This is preceded by the expression of VEGF in hypertrophic chondrocytes (31, 273). Inactivation of VEGF by systemic administration of a soluble receptor to 24-d-old mice suppressed blood vessel invasion and trabecular bone formation concomitant with an increased width of the hypertrophic zone (31). Moreover, recruitment of chondroclasts expressing MMP-9 and resorption of terminally differentiated chondrocytes were inhibited (31). In this context, MMP-9 knockout mice show a wider hypertrophic zone along with delayed chondrocyte apoptosis, vascularization, and ossification (21). These data indicate that VEGF and MMP-9 are key players in the events that take place during the endstage of endochondral bone formation such as terminal differentiation of chondrocytes, vascular invasion, chondrocyte apoptosis, and their subsequent replacement by bone (21, 31, 274). Other promotors or inhibitors of angiogenesis have been described in the literature, including transferrin (promotor) (275), chondromodulin (inhibitor) (276), and FGFs (promotor) (277).

In embryonic growth plates, Schipani et al. (13) described the role of hypoxia inducible factor (HIF)-1, which is a transcription factor that regulates VEGF expression (13, 278). Growth plate-specific targeted deletion of HIF-1 caused increased cell death and reduced VEGF expression (13). At the same time, cells surrounding the area of increased cell death contained enhanced VEGF levels, which was secondary to their altered redox status. This suggests that VEGF expression is regulated in an HIF-1-dependent and -independent manner (13).

Recently, a member of the runt family of transcription factors, Cbfa1/Runx2, was demonstrated in hypertrophic chondrocytes (279). Constitutive expression in proliferating chondrocytes induced hypertrophic chondrocyte differentiation but also Ihh expression (280). In contrast, in primary chondrocytes from newborn mice, hedgehog signaling enhanced the expression of Cbfa1 (281). Apparently, a regulatory loop exists, in which Cbfa1 and Ihh regulate each other, involving hypertrophic chondrocytes and mesenchymal cells of the bone collar (282). Furthermore, Cbfa1 was shown to play a role in the expression of VEGF in growth plate chondrocytes (283). These data provide a link between Ihh and VEGF in regulating the pace of hypertrophic and terminal differentiation of growth plate chondrocytes (Fig. 3).

	V. Growth Plate Regulation after Birth and Interactions between Hormonal and Local Mechanisms

Top Abstract I. The Growth Plate II. Longitudinal Growth III. Hormonal Regulation IV. Local Regulation V. Growth Plate Regulation... VI. Conclusions and Perspectives References

 
A. Local growth plate regulation after birth
All growth factors mentioned above are expressed in embryonic growth plates, suggesting that they fulfill a crucial role in longitudinal growth before birth. However, evidence is gathering that they also play a role after birth. A number of papers have now localized Ihh, PTHrP, and their receptors in mammalian growth plates and fracture calluses, suggesting that these factors play a role in local regulation of longitudinal bone growth and fracture repair after birth as well (214, 228, 284, 285, 286, 287, 288, 289). We were among the first to demonstrate Ihh, PTHrP, Ptc, and the PTH/PTHrP receptor in female and male rat growth plates during development (290). Interestingly, all genes studied within the postnatal growth plate were predominantly expressed in the transition zone and to a lesser extent in the growth plate stem cells. Because the distance from the growth plate chondrocytes to the periarticular perichondrium considerably increases during embryonic bone development, due to the appearance of a secondary ossification center, diffusion of growth factors between these two areas will be seriously hampered. The localized expression of all players in the Ihh/PTHrP feedback loop predominantly in the transition zone of the growth plate suggests that diffusion over long distances is not required after birth and that the feedback loop may be in part autocrine (293).

Besides Ihh, PTHrP, and their receptors, BMP2, -4, -6, and -7 are also expressed in proliferating and maturing chondrocytes of growth plates after birth (284, 291, 292, 293). Moreover, their receptors, BMPRIA, -IB and -II, were found throughout the growth plate, albeit at a lower level in hypertrophic chondrocytes (293). Also, FGFs and VEGF are found in the postnatal growth plate (294, 295, 296), adding to the concept that the complete regulatory array of growth factors found in embryonic bones is present after birth as well and may play a similar role in the regulation of chondrocyte proliferation and differentiation.

Functional evidence for effects of growth factors in the growth plate after birth is still limited. A regulatory role for Ihh in chondrocyte differentiation comes from findings in a human condition known as hereditary multiple exostoses, which becomes manifest after birth and in which mutations in genes encoding exostosins (EXTs) have been identified (297, 298, 299). Mutations in EXT 1 and 2 led to an absence of the proteoglycan heparan sulfate, which is an important signaling molecule involved in transport of growth factors in cartilage, including Ihh and FGFs (300, 301, 302). Absent or undersulfated heparan sulfate may therefore result in disturbed Ihh and FGF transport through the growth plate, leading to disorganization of growth plate chondrocytes, further establishing Ihh as a central player in chondrocyte proliferation and differentiation (27, 302). In this respect, it is worthwhile mentioning that a recently identified mutation of the PTH/PTHrP receptor gene in human enchondromatosis signals abnormally in vitro and causes enchondroma-like lesions in transgenic mice. The mutant receptor constitutively activates hedgehog signaling, most likely causing formation of enchondroma-like lesions (303). In a more recent study, reduced growth plate Ihh and PTHrP expression was suggested to contribute to the observed growth delay and disturbed growth plate architecture in irradiated tibiae of young rats (304).

An important finding for a crucial role of PTHrP in growth plates after birth comes from a study by Schipani et al. (305). Targeted expression of a Jansen receptor (a constitutively active PTH/PTHrP receptor) in the growth plate of PTHrP-ablated mice rescued these mice from perinatal death and caused, among other phenomena, a reduction in longitudinal growth. Surprisingly, premature epiphyseal closure was observed in 3-wk-old mice. Growth plate closure does usually not occur until late in life. These observations suggest a role for PTHrP and its receptor in growth plate fusion (305).

B. Interactions between hormonal and local regulation
Increasing evidence is gathering for interactions between hormonal regulation and local factors at the level of the growth plate. Receptors for GH, T₃/T₄, GC, estrogens, and androgens have all been detected in growth plates from various species, indicating that most, if not all, hormones can have direct effects on processes in the growth plate after birth (80, 110, 111, 122, 154, 155, 181, 183).

Stevens et al. (287) studied PTHrP and PTH/PTHrP receptor expression in hypothyroid, thyrotoxic, and hypothyroid-T₄-treated rat growth plates. They found that thyroid status greatly influenced the expression of both proteins; hypothyroidism caused, in addition to disorganized growth plates, enhanced PTHrP expression, whereas in thyrotoxic rats the PTH/PTHrP receptor was undetectable. These data indicate that disturbed Ihh/PTHrP feedback loop activity may be a mechanism that underlies growth disorders in childhood thyroid disease (287). Only very recently, Kindblom et al. (306) examined the expression of Ihh and PTHrP in growth plates from patients subjected to epiphyseal surgery. It appeared that immunostaining for both Ihh and PTHrP was present predominantly in early hypertrophic chondrocytes and that its level of expression was higher during early stages and lower during later stages of puberty. These data are suggestive for the assumption that both Ihh and PTHrP are involved in the regulation of pubertal growth in humans and combined with the observations in the Jansen mice suggesting a role for this system in growth plate closure (287, 305). Whether the Ihh/PTHrP feedback loop can be regulated by estrogens in the growth plate is, however, not clear. Interestingly, ERs are expressed in zones of the growth plate that also express Ihh and/or PTHrP, suggesting that the expression of these genes may be regulated by this sex steroid. That this might be the case comes from observations in the rat uterus, where E₂ induces PTHrP expression (307). Summarizing, it seems likely that systemic hormones involved in the regulation of longitudinal growth exert their effects on growth plate chondrocytes by influencing the expression and/or activity of locally acting growth factors, such as Ihh, PTHrP, BMPs, FGFs, and VEGF.

	VI. Conclusions and Perspectives

Top Abstract I. The Growth Plate II. Longitudinal Growth III. Hormonal Regulation IV. Local Regulation V. Growth Plate Regulation... VI. Conclusions and Perspectives References

 
Over the last decade, much knowledge has been gained regarding local mechanisms regulating chondrocyte proliferation and differentiation in the embryonic growth plate. There is increasing evidence that these local regulatory systems are also functional after birth. The effects of hormones on longitudinal growth and final height are well known, and it is now recognized that these hormones exert a large part of their effects by acting directly on the growth plate. Still, the molecular mechanisms that underlie these effects are largely unknown. Intensive research focusing on the interaction of systemic hormones with locally acting mechanisms such as the Ihh/PTHrP feedback loop in the coming years will undoubtedly provide additional data that will shed light on the molecular regulation of longitudinal growth at the level of the epiphyseal plate.

	Footnotes

 
Present address for B.C.J.v.d.E.: Department of Internal Medicine, Erasmus Medical Center, Room Ee569, Dr. Molewaterplein 50, 3015 GE Rotterdam, The Netherlands.

Abbreviations: A, Androstenedione; AR, androgen receptor; ArKO, aromatase knockout; ARKO, AR knockout; BERKO, knockout mice for ERß; BMP, bone morphogenetic protein; BOCD, Blomstrand lethal osteochondrodysplasia; DERKO, knockout mice for ER and ERß; DHEA, dihydroepiandrosterone; DHT, dihydrotestosterone; E₁, estrone; E₂, 17ß-estradiol; ECM, extracellular matrix; ER, estrogen receptor; ERKO, knockout mice for ER; FGF, fibroblast growth factor; FGFR, FGF receptor; GC, glucocorticoid(s); GDF, growth and differentiation factor; GHBP, GH binding protein; GHR, GH receptor; GHS, GH secretagogues; GR, GC receptor; HIF, hypoxia inducible factor; HSD, hydroxysteroid dehydrogenase; IGFBP, IGF binding protein; Ihh, Indian hedgehog; MMP, matrix metalloproteinases; OVX, ovariectomy; Ptc, patched; T, testosterone; TR, thyroid hormone receptor; VEGF, vascular endothelial growth factor.

	References

Top Abstract I. The Growth Plate II. Longitudinal Growth III. Hormonal Regulation IV. Local Regulation V. Growth Plate Regulation... VI. Conclusions and Perspectives References

 

1. Hunziker EB 1994 Mechanism of longitudinal bone growth and its regulation by growth plate chondrocytes. Microsc Res Tech 28:505–519[CrossRef][Medline]
2. Kember NF 1993 Cell kinetics and the control of bone growth. Acta Paediatr Suppl 82 Suppl 391:61–65
3. Horton Jr WE, Feng L, Adams C 1998 Chondrocyte apoptosis in development, aging and disease. Matrix Biol 17:107–115[CrossRef][Medline]
4. Kember NF, Sissons HA 1976 Quantitative histology of the human growth plate. J Bone Joint Surg Br 58-B:426–435
5. Sissons HA, Kember NF 1977 Longitudinal bone growth of the human femur. Postgrad Med J 53:433–437[Abstract/Free Full Text]
6. Abad V, Meyers JL, Weise M, Gafni RI, Barnes KM, Nilsson O, Bacher JD, Baron J 2002 The role of the resting zone in growth plate chondrogenesis. Endocrinology 143:1851–1857[Abstract/Free Full Text]
7. Gafni RI, Weise M, Robrecht DT, Meyers JL, Barnes KM, De Levi S, Baron J 2001 Catch-up growth is associated with delayed senescence of the growth plate in rabbits. Pediatr Res 50:618–623[Medline]
8. Minina E, Kreschel C, Naski MC, Ornitz DM, Vortkamp A 2002 Interaction of FGF, Ihh/Pthlh, and BMP signaling integrates chondrocyte proliferation and hypertrophic differentiation. Dev Cell 3:439–449[CrossRef][Medline]
9. Wang W, Kirsch T 2002 Retinoic acid stimulates annexin-mediated growth plate chondrocyte mineralization. J Cell Biol 157:1061–1069[Abstract/Free Full Text]
10. Anderson HC 2003 Matrix vesicles and calcification. Curr Rheumatol Rep 5:222–226[Medline]
11. Kirsch T, Harrison G, Golub EE, Nah HD 2000 The roles of annexins and types II and X collagen in matrix vesicle-mediated mineralization of growth plate cartilage. J Biol Chem 275:35577–35583[Abstract/Free Full Text]
12. Wang W, Xu J, Kirsch T 2003 Annexin-mediated Ca2+ influx regulates growth plate chondrocyte maturation and apoptosis. J Biol Chem 278:3762–3769[Abstract/Free Full Text]
13. Schipani E, Ryan HE, Didrickson S, Kobayashi T, Knight M, Johnson RS 2001 Hypoxia in cartilage: HIF-1 is essential for chondrocyte growth arrest and survival. Genes Dev 15:2865–2876[Abstract/Free Full Text]
14. Waring P, Beaver J 1996 Cyclosporin A rescues thymocytes from apoptosis induced by very low concentrations of thapsigargin: effects on mitochondrial function. Exp Cell Res 227:264–276[CrossRef][Medline]
15. Escargueil-Blanc I, Meilhac O, Pieraggi MT, Arnal JF, Salvayre R, Negre-Salvayre A 1997 Oxidized LDLs induce massive apoptosis of cultured human endothelial cells through a calcium-dependent pathway. Prevention by aurintricarboxylic acid. Arterioscler Thromb Vasc Biol 17:331–339[Abstract/Free Full Text]
16. Srinivasan S, Stevens MJ, Sheng H, Hall KE, Wiley JW 1998 Serum from patients with type 2 diabetes with neuropathy induces complement-independent, calcium-dependent apoptosis in cultured neuronal cells. J Clin Invest 102:1454–1462[Medline]
17. Boyan BD, Sylvia VL, Dean DD, Schwartz Z 2001 24,25-(OH)(2)D(3) Regulates cartilage and bone via autocrine and endocrine mechanisms. Steroids 66:363–374[CrossRef][Medline]
18. Malloy PJ, Pike JW, Feldman D 1999 The vitamin D receptor and the syndrome of hereditary 1,25-Dihydroxyvitamin D-resistant rickets. Endocr Rev 20:156–188[Abstract/Free Full Text]
19. Lin R, Amizuka N, Sasaki T, Aarts MM, Ozawa H, Goltzman D, Henderson JE, White JH 2002 1,25-Dihydroxyvitamin D3 promotes vascularization of the chondro-osseous junction by stimulating expression of vascular endothelial growth factor and matrix metalloproteinase 9. J Bone Miner Res 17:1604–1612[CrossRef][Medline]
20. Lewinson D, Silbermann M 1992 Chondroclasts and endothelial cells collaborate in the process of cartilage resorption. Anat Rec 233:504–514[CrossRef][Medline]
21. Vu TH, Shipley JM, Bergers G, Berger JE, Helms JA, Hanahan D, Shapiro SD, Senior RM, Werb Z 1998 MMP-9/gelatinase B is a key regulator of growth plate angiogenesis and apoptosis of hypertrophic chondrocytes. Cell 93:411–422[CrossRef][Medline]
22. Horton WA 1993 Morphology of connective tissue: cartilage. In: McCusick V, ed. Connective tissue and its heritable disorders. New York: Wiley-Liss, Inc.; 641–675
23. Spranger J, Winterpacht A, Zabel B 1994 The type II collagenopathies: a spectrum of chondrodysplasias. Eur J Pediatr 153:56–65[Medline]
24. Horton Jr WE, Wang L, Bradham D, Precht P, Balakir R 1992 The control of expression of type II collagen: relevance to cartilage disease. DNA Cell Biol 11:193–198[Medline]
25. Muragaki Y, Mariman EC, van Beersum SE, Perala M, van Mourik JB, Warman ML, Hamel BC, Olsen BR 1996 A mutation in COL9A2 causes multiple epiphyseal dysplasia (EDM2). Ann NY Acad Sci 785:303–306[Medline]
26. Wallis GA, Rash B, Sykes B, Bonaventure J, Maroteaux P, Zabel B, Wynne-Davies R, Grant ME, Boot-Handford RP 1996 Mutations within the gene encoding the 1 (X) chain of type X collagen (COL10A1) cause metaphyseal chondrodysplasia type Schmid but not several other forms of metaphyseal chondrodysplasia. J Med Genet 33:450–457[Abstract/Free Full Text]
27. Rossi A, Superti-Furga A 2001 Mutations in the diastrophic dysplasia sulfate transporter (DTDST) gene (SLC26A2): 22 novel mutations, mutation review, associated skeletal phenotypes, and diagnostic relevance. Hum Mutat 17:159–171[CrossRef][Medline]
28. Ruoslahti E 1991 Integrins. J Clin Invest 87:1–5
29. Werb Z 1997 ECM and cell surface proteolysis: regulating cellular ecology. Cell 91:439–442[CrossRef][Medline]
30. Ortega N, Behonick D, Stickens D, Werb Z 2003 How proteases regulate bone morphogenesis. Ann NY Acad Sci 995:109–116[Medline]
31. Gerber HP, Vu TH, Ryan AM, Kowalski J, Werb Z, Ferrara N 1999 VEGF couples hypertrophic cartilage remodeling, ossification and angiogenesis during endochondral bone formation. Nat Med 5:623–628[CrossRef][Medline]
32. Alexander CM, Werb Z 1992 Targeted disruption of the tissue inhibitor of metalloproteinases gene increases the invasive behavior of primitive mesenchymal cells derived from embryonic stem cells in vitro. J Cell Biol 118:727–739[Abstract/Free Full Text]
33. Wu CW, Tchetina EV, Mwale F, Hasty K, Pidoux I, Reiner A, Chen J, Van W, Poole AR 2002 Proteolysis involving matrix metalloproteinase 13 (collagenase-3) is required for chondrocyte differentiation that is associated with matrix mineralization. J Bone Miner Res 17:639–651[CrossRef][Medline]
34. Cancedda R, Descalzi Cancedda F, Castagnola P 1995 Chondrocyte differentiation. Int Rev Cytol 159:265–358[Medline]
35. Hering TM 1999 Regulation of chondrocyte gene expression. Front Biosci 4:D743–D761
36. Stevens DA, Williams GR 1999 Hormone regulation of chondrocyte differentiation and endochondral bone formation. Mol Cell Endocrinol 151:195–204[CrossRef][Medline]
37. Robson H, Siebler T, Shalet SM, Williams GR 2002 Interactions between GH, IGF-I, glucocorticoids, and thyroid hormones during skeletal growth. Pediatr Res 52:137–147[CrossRef][Medline]
38. Kronenberg HM 2003 Developmental regulation of the growth plate. Nature 423:332–336[CrossRef][Medline]
39. Tanner JM 1962 The adolescent spurt in animals. In: Thomas CC, ed. Growth at adolescence. Oxford, UK: Blackwell; 223–239
40. Drop SL, De Waal WJ, Muinck Keizer-Schrama SM 1998 Sex steroid treatment of constitutionally tall stature. Endocr Rev 19:540–558[Abstract/Free Full Text]
41. Martin EA, Ritman EL, Turner RT 2003 Time course of epiphyseal growth plate fusion in rat tibiae. Bone 32:261–267[Medline]
42. Parfitt AM 2002 Misconceptions (1): epiphyseal fusion causes cessation of growth. Bone 30:337–339[Medline]
43. Roach HI, Mehta G, Oreffo RO, Clarke NM, Cooper C 2003 Temporal analysis of rat growth plates: cessation of growth with age despite presence of a physis. J Histochem Cytochem 51:373–383[Abstract/Free Full Text]
44. Drop SL, Greggio N, Cappa M, Bernasconi S 2001 Current concepts in tall stature and overgrowth syndromes. J Pediatr Endocrinol Metab 14(Suppl 2):975–984
45. Lecointre C, Toublanc JE 1997 Psychological indications for treatment of tall stature in adolescent girls. J Pediatr Endocrinol Metab 10:529–531[Medline]
46. Boersma B, Wit JM 1997 Catch-up growth. Endocr Rev 18:646–661[Abstract/Free Full Text]
47. Prader A, Tanner JM, von Harnack G 1963 Catch-up growth following illness or starvation. J Pediatr 62:646–659[CrossRef][Medline]
48. Boersma B, Rikken B, Wit JM, Dutch Growth Hormone Working Group 1995 Catch-up growth in early treated patients with growth hormone deficiency. Arch Dis Child 72:427–431[Abstract/Free Full Text]
49. Damen GM, Boersma B, Wit JM, Heymans HSA 1997 Catch-up growth in 60 children with celiac disease. J Pediatr Gastroenterol Nutr 19:394–400[CrossRef]
50. Tanner JM 1978 Foetus into man: physical growth from conception to maturity. Cambridge, MA: Harvard University Press; 156–157
51. Baron J, Klein KO, Colli MJ, Yanovski JA, Novosad JA, Bacher JD, Cutler Jr GB 1994 Catch-up growth after glucocorticoid excess: a mechanism intrinsic to the growth plate. Endocrinology 135:1367–1371[Abstract]
52. Gafni RI, Baron J 2000 Catch-up growth: possible mechanisms. Pediatr Nephrol 14:616–619[CrossRef][Medline]
53. Weise M, De Levi S, Barnes KM, Gafni RI, Abad V, Baron J 2001 Effects of estrogen on growth plate senescence and epiphyseal fusion. Proc Natl Acad Sci USA 98:6871–6876[Abstract/Free Full Text]
54. Wit JM, Boersma B 2002 Catch-up growth: definition, mechanisms, and models. J Pediatr Endocrinol Metab 15(Suppl 5):1229–1241
55. Woods KA, Camacho-Hubner C, Savage MO, Clark AJ 1996 Intrauterine growth retardation and postnatal growth failure associated with deletion of the insulin-like growth factor I gene. N Engl J Med 335:1363–1367[Free Full Text]
56. Root AW, Root MJ 2002 Clinical pharmacology of human growth hormone and its secretagogues. Curr Drug Targets Immune Endocr Metabol Disord 2:27–52[CrossRef][Medline]
57. Baldelli R, Otero XL, Camina JP, Gualillo O, Popovic V, Dieguez C, Casanueva FF 2001 Growth hormone secretagogues as diagnostic tools in disease states. Endocrine 14:95–99[CrossRef][Medline]
58. Veldhuis JD 1998 Neuroendocrine control of pulsatile growth hormone release in the human: relationship with gender. Growth Horm IGF Res 8(Suppl B):49–59
59. Daughaday WH 1992 Pituitary gigantism. Endocrinol Metab Clin North Am 21:633–647[Medline]
60. Ezzat S 1997 Acromegaly. Endocrinol Metab Clin North Am 26:703–723[CrossRef][Medline]
61. Wit JM, Drayer NM, Jansen M, Walenkamp MJ, Hackeng WH, Thijssen JH, Van den Brande JL 1989 Total deficiency of growth hormone and prolactin, and partial deficiency of thyroid stimulating hormone in two Dutch families: a new variant of hereditary pituitary deficiency. Horm Res 32:170–177[Medline]
62. Pfaffle RW, Parks JS, Brown MR, Heimann G 1993 Pit-1 and pituitary function. J Pediatr Endocrinol 6:229–233[Medline]
63. Rosenfeld R, Allen DB, MacGillivray MH, Alter C, Saenger P, Anhalt H, Hintz R, Katz HP 2000 Growth hormone use in pediatric growth hormone deficiency and other pediatric growth disorders. Am J Manag Care 6:S805–S816
64. Savage MO, Burren CP, Blair JC, Woods KA, Metherell L, Clark AJ, Camacho-Hubner C2001 Growth hormone insensitivity: pathophysiology, diagnosis, clinical variation and future perspectives. Horm Res 55(Suppl 2):32–35
65. Woods KA, Savage MO 1996 Laron syndrome: typical and atypical forms. Baillieres Clin Endocrinol Metab 10:371–387[CrossRef][Medline]
66. DeChiara TM, Robertson EJ, Efstratiadis A 1991 Parental imprinting of the mouse insulin-like growth factor II gene. Cell 64:849–859[CrossRef][Medline]
67. Liu JP, Baker J, Perkins AS, Robertson EJ, Efstratiadis A 1993 Mice carrying null mutations of the genes encoding insulin-like growth factor I (Igf-1) and type 1 IGF receptor (Igf1r). Cell 75:59–72[Medline]
68. Le Roith D, Bondy C, Yakar S, Liu JL, Butler A 2001 The somatomedin hypothesis: 2001. Endocr Rev 22:53–74[Abstract/Free Full Text]
69. Salmon Jr WD, Daughaday WH 1957 A hormonally controlled serum factor which stimulates sulfate incorporation by cartilage in vitro. J Lab Clin Med 49:825–836[Medline]
70. Isaksson OG, Jansson JO, Gause IA 1982 Growth hormone stimulates longitudinal bone growth directly. Science 216:1237–1239[Abstract/Free Full Text]
71. Russell SM, Spencer EM 1985 Local injections of human or rat growth hormone or of purified human somatomedin-C stimulate unilateral tibial epiphyseal growth in hypophysectomized rats. Endocrinology 116:2563–2567[Abstract/Free Full Text]
72. Schlechter NL, Russell SM, Greenberg S, Spencer EM, Nicoll CS 1986 A direct growth effect of growth hormone in rat hindlimb shown by arterial infusion. Am J Physiol 250:E231–E235
73. Nilsson A, Isgaard J, Lindahl A, Dahlstrom A, Skottner A, Isaksson OG 1986 Regulation by growth hormone of number of chondrocytes containing IGF-I in rat growth plate. Science 233:571–574[Abstract/Free Full Text]
74. Green H, Morikawa M, Nixon T 1985 A dual effector theory of growth-hormone action. Differentiation 29:195–198[CrossRef][Medline]
75. Isaksson OGP, Lindahl A, Nilsson A, Isgaard J 1987 Mechanism of the stimulatory effect of growth hormone on longitudinal bone growth. Endocr Rev 8:426–438[Abstract/Free Full Text]
76. Hunziker EB, Wagner J, Zapf J 1994 Differential effects of insulin-like growth factor I and growth hormone on developmental stages of rat growth plate chondrocytes in vivo. J Clin Invest 93:1078–1086
77. Ohlsson C, Nilsson A, Isaksson O, Lindahl A 1992 Growth hormone induces multiplication of the slowly cycling germinal cells of the rat tibial growth plate. Proc Natl Acad Sci USA 89:9826–9830[Abstract/Free Full Text]
78. Barnard R, Haynes KM, Werther GA, Waters MJ 1988 The ontogeny of growth hormone receptors in the rabbit tibia. Endocrinology 122:2562–2569[Abstract/Free Full Text]
79. Werther GA, Haynes K, Edmonson S, Oakes S, Buchanan CJ, Herington AC, Waters MJ 1993 Identification of growth hormone receptors on human growth plate chondrocytes. Acta Paediatr Suppl 82 Suppl 391:50–53
80. Gevers EF, van der Eerden BC, Karperien M, Raap AK, Robinson IC, Wit JM2002 Localization and regulation of the growth hormone receptor and growth hormone-binding protein in the rat growth plate. J Bone Miner Res 17:1408–1419
81. Wang J, Zhou J, Bondy CA 1999 Igf1 promotes longitudinal bone growth by insulin-like actions augmenting chondrocyte hypertrophy. FASEB J 13:1985–1990[Abstract/Free Full Text]
82. Powell-Braxton L, Hollingshead P, Warburton C, Dowd M, Pitts-Meek S, Dalton D, Gillett N, Stewart TA 1993 IGF-I is required for normal embryonic growth in mice. Genes Dev 7:2609–2617[Abstract/Free Full Text]
83. Liu JL, Leroith D 1999 Insulin-like growth factor I is essential for postnatal growth in response to growth hormone. Endocrinology 140:5178–5184[Abstract/Free Full Text]
84. Zhou Y, Xu BC, Maheshwari HG, He L, Reed M, Lozykowski M, Okada S, Cataldo L, Coschigamo K, Wagner TE, Baumann G, Kopchick JJ 1997 A mammalian model for Laron syndrome produced by targeted disruption of the mouse growth hormone receptor/binding protein gene (the Laron mouse). Proc Natl Acad Sci USA 94:13215–13220[Abstract/Free Full Text]
85. Lupu F, Terwilliger JD, Lee K, Segre GV, Efstratiadis A 2001 Roles of growth hormone and insulin-like growth factor 1 in mouse postnatal growth. Dev Biol 229:141–162[CrossRef][Medline]
86. Mohan S, Richman C, Guo R, Amaar Y, Donahue LR, Wergedal J, Baylink DJ 2003 Insulin-like growth factor regulates peak bone mineral density in mice by both growth hormone-dependent and -independent mechanisms. Endocrinology 144:929–936[Abstract/Free Full Text]
87. Yakar S, Liu JL, Stannard B, Butler A, Accili D, Sauer B, Leroith D 1999 Normal growth and development in the absence of hepatic insulin-like growth factor I. Proc Natl Acad Sci USA 96:7324–7329[Abstract/Free Full Text]
88. Yakar S, Liu JL, Le Roith D2000 The growth hormone/insulin-like growth factor-I system: implications for organ growth and development. Pediatr Nephrol 14:544–549
89. Sjogren K, Liu JL, Blad K, Skrtic S, Vidal O, Wallenius V, Leroith D, Tornell J, Isaksson OG, Jansson JO, Ohlsson C 1999 Liver-derived insulin-like growth factor I (IGF-I) is the principal source of IGF-I in blood but is not required for postnatal body growth in mice. Proc Natl Acad Sci USA 96:7088–7092[Abstract/Free Full Text]
90. Butler AA, Yakar S, LeRoith D 2002 Insulin-like growth factor-I: compartmentalization within the somatotropic axis? News Physiol Sci 17:82–85[Abstract/Free Full Text]
91. Yakar S, Rosen CJ, Beamer WG, Ackert-Bicknell CL, Wu Y, Liu JL, Ooi GT, Setser J, Frystyk J, Boisclair YR, Leroith D 2002 Circulating levels of IGF-1 directly regulate bone growth and density. J Clin Invest 110:771–781[CrossRef][Medline]
92. Shinar DM, Endo N, Halperin D, Rodan GA, Weinreb M 1993 Differential expression of insulin-like growth factor-I (IGF-I) and IGF-II messenger ribonucleic acid in growing rat bone. Endocrinology 132:1158–1167[Abstract/Free Full Text]
93. Wang E, Wang J, Chin E, Zhou J, Bondy CA 1995 Cellular patterns of insulin-like growth factor system gene expression in murine chondrogenesis and osteogenesis. Endocrinology 136:2741–2751[Abstract]
94. Smink JJ, Koster JG, Gresnigt MG, Rooman R, Koedam JA, Buul-Offers SC 2002 IGF and IGF-binding protein expression in the growth plate of normal, dexamethasone-treated and human IGF-II transgenic mice. J Endocrinol 174:343–352[Abstract]
95. Olney RC, Mougey EB 1999 Expression of the components of the insulin-like growth factor axis across the growth-plate. Mol Cell Endocrinol 156:63–71[CrossRef][Medline]
96. Reinecke M, Schmid AC, Heyberger-Meyer B, Hunziker EB, Zapf J 2000 Effect of growth hormone and insulin-like growth factor I (IGF-I) on the expression of IGF-I messenger ribonucleic acid and peptide in rat tibial growth plate and articular chondrocytes in vivo. Endocrinology 141:2847–2853[Abstract/Free Full Text]
97. Koedam JA, Hoogerbrugge CM, Buul-Offers SC 2000 Differential regulation of IGF-binding proteins in rabbit costal chondrocytes by IGF-I and dexamethasone. J Endocrinol 165:557–567[Abstract]
98. McQueeney K, Dealy CN 2001 Roles of insulin-like growth factor-I (IGF-I) and IGF-I binding protein-2 (IGFBP2) and -5 (IGFBP5) in developing chick limbs. Growth Horm IGF Res 11:346–363[CrossRef][Medline]
99. Underwood LE, van Wijk JJ 1992 Normal and abberant growth. In: Wilson JD, Foster DW, eds. Textbook of endocrinology. Philadelphia: WB Saunders Company; 1079–1138
100. Ohlsson C, Isgaard J, Nilsson A, Isaksson OGP, Lindahl A 1993 Endocrine regulation of longitudinal bone growth. Acta Paediatr Suppl 391:33–40
101. Snyder P 1996 The pituitary in hypothyroidism. In: Braverman L, Utiger R, eds. Werner and Ingbar’s the thyroid. Philadelphia: Lippincott-Raven; 836–840
102. Letarte J, LaFranchi S 1983 Congenital hypothyroidism. In: Dussault JH, Walker P, eds. Basic and clinical endocrinology. New York: Butterworths; 351–383
103. Schlesinger S, MacGillivray MH, Munschauer RW 1973 Acceleration of growth and bone maturation in childhood thyrotoxicosis. J Pediatr 83:233–236[CrossRef][Medline]
104. Rivkees SA, Bode HH, Crawford JD 1988 Long-term growth in juvenile acquired hypothyroidism: the failure to achieve normal adult stature. N Engl J Med 318:599–602[Abstract]
105. Segni M, Leonardi E, Mazzoncini B, Pucarelli I, Pasquino AM 1999 Special features of Graves’ disease in early childhood. Thyroid 9:871–877[Medline]
106. O’Shea PJ, Harvey CB, Suzuki H, Kaneshige M, Kaneshige K, Cheng SY, Williams GR 2003 A thyrotoxic skeletal phenotype of advanced bone formation in mice with resistance to thyroid hormone. Mol Endocrinol 17:1410–1424[Abstract/Free Full Text]
107. Gothe S, Wang Z, Ng L, Kindblom JM, Barros AC, Ohlsson C, Vennstrom B, Forrest D 1999 Mice devoid of all known thyroid hormone receptors are viable but exhibit disorders of the pituitary-thyroid axis, growth, and bone maturation. Genes Dev 13:1329–1341[Abstract/Free Full Text]
108. Forrest D, Hanebuth E, Smeyne RJ, Everds N, Stewart CL, Wehner JM, Curran T 1996 Recessive resistance to thyroid hormone in mice lacking thyroid hormone receptor ß: evidence for tissue-specific modulation of receptor function. EMBO J 15:3006–3015[Medline]
109. Wikstrom L, Johansson C, Salto C, Barlow C, Campos BA, Baas F, Forrest D, Thoren P, Vennstrom B 1998 Abnormal heart rate and body temperature in mice lacking thyroid hormone receptor 1. EMBO J 17:455–461[CrossRef][Medline]
110. Robson H, Siebler T, Stevens DA, Shalet SM, Williams GR 2000 Thyroid hormone acts directly on growth plate chondrocytes to promote hypertrophic differentiation and inhibit clonal expansion and cell proliferation. Endocrinology 141:3887–3897[Abstract/Free Full Text]
111. Abu EO, Bord S, Horner A, Chatterjee VK, Compston JE 1997 The expression of thyroid hormone receptors in human bone. Bone 21:137–142[Medline]
112. Burch WM, van Wyk JJ 1987 Triiodothyronine stimulates cartilage growth and maturation by different mechanisms. Am J Physiol 252:E176–E182
113. Lewinson D, Bialik GM, Hochberg Z 1994 Differential effects of hypothyroidism on the cartilage and the osteogenic process in the mandibular condyle: recovery by growth hormone and thyroxine. Endocrinology 135:1504–1510[Abstract]
114. Wakita R, Izumi T, Itoman M 1998 Thyroid hormone-induced chondrocyte terminal differentiation in rat femur organ culture. Cell Tissue Res 293:357–364[CrossRef][Medline]
115. Smeets T, Buul-Offers S 1986 Influence of growth hormone and thyroxine on cell kinetics in the proximal tibial growth plate of Snell dwarf mice. Cell Tissue Kinet 19:161–170[Medline]
116. Okubo Y, Hari RA 2003 Thyroxine downregulates Sox9 and promotes chondrocyte hypertrophy. Biochem Biophys Res Commun 306:186–190[CrossRef][Medline]
117. Lewinson D, Harel Z, Shenzer P, Silbermann M, Hochberg Z 1989 Effect of thyroid hormone and growth hormone on recovery from hypothyroidism of epiphyseal growth plate cartilage and its adjacent bone. Endocrinology 124:937–945[Abstract/Free Full Text]
118. Ohlsson C, Nilsson A, Isaksson O, Bentham J, Lindahl A 1992 Effects of tri-iodothyronine and insulin-like growth factor-I (IGF-I) on alkaline phosphatase activity, [³H]thymidine incorporation and IGF-I receptor mRNA in cultured rat epiphyseal chondrocytes. J Endocrinol 135:115–123[Abstract/Free Full Text]
119. Bello CE, Garrett SD 1999 Therapeutic issues in oral glucocorticoid use. Lippincotts Prim Care Pract 3:333–341[Medline]
120. Elias LL, Huebner A, Metherell LA, Canas A, Warne GL, Bitti ML, Cianfarani S, Clayton PE, Savage MO, Clark AJ 2000 Tall stature in familial glucocorticoid deficiency. Clin Endocrinol (Oxf) 53:423–430[CrossRef][Medline]
121. Annefeld M 1992 Changes in rat epiphyseal cartilage after treatment with dexamethasone and glycosaminoglycan-peptide complex. Pathol Res Pract 188:649–652[Medline]
122. Silvestrini G, Mocetti P, Ballanti P, Di Grezia R, Bonucci E 1999 Cytochemical demonstration of the glucocorticoid receptor in skeletal cells of the rat. Endocr Res 25:117–128[Medline]
123. Abu EO, Horner A, Kusec V, Triffitt JT, Compston JE 2000 The localization of the functional glucocorticoid receptor in human bone. J Clin Endocrinol Metab 85:883–889[Abstract/Free Full Text]
124. Silvestrini G, Ballanti P, Patacchioli FR, Mocetti P, Di Grezia R, Wedard BM, Angelucci L, Bonucci E 2000 Evaluation of apoptosis and the glucocorticoid receptor in the cartilage growth plate and metaphyseal bone cells of rats after high-dose treatment with corticosterone. Bone 26:33–42[Medline]
125. Smink JJ, Gresnigt MG, Hamers N, Koedam JA, Berger R, Buul-Offers SC 2003 Short-term glucocorticoid treatment of prepubertal mice decreases growth and IGF-I expression in the growth plate. J Endocrinol 177:381–388[Abstract]
126. Mocetti P, Silvestrini G, Ballanti P, Patacchioli FR, Di Grezia R, Angelucci L, Bonucci E 2001 Bcl-2 and Bax expression in cartilage and bone cells after high-dose corticosterone treatment in rats. Tissue Cell 33:1–7[CrossRef][Medline]
127. Chrysis D, Ritzen EM, Savendahl L 2003 Growth retardation induced by dexamethasone is associated with increased apoptosis of the growth plate chondrocytes. J Endocrinol 176:331–337[Abstract]
128. Allen DB 1996 Growth suppression by glucocorticoid therapy. Endocrinol Metab Clin North Am 25:699–717[CrossRef][Medline]
129. Luo JM, Murphy LJ 1989 Dexamethasone inhibits growth hormone induction of insulin-like growth factor-I (IGF-I) messenger ribonucleic acid (mRNA) in hypophysectomized rats and reduces IGF-I mRNA abundance in the intact rat. Endocrinology 125:165–171[Abstract/Free Full Text]
130. Itagane Y, Inada H, Fujita K, Isshiki G 1991 Interactions between steroid hormones and insulin-like growth factor-I in rabbit chondrocytes. Endocrinology 128:1419–1424[Abstract/Free Full Text]
131. Smink JJ, Koster JG, Gresnigt MG, Rooman R, Koedam JA, Buul-Offers SC 2002 IGF and IGF-binding protein expression in the growth plate of normal, dexamethasone-treated and human IGF-II transgenic mice. J Endocrinol 175:143–153[Abstract]
132. Heyma P, Larkins RG 1982 Glucocorticoids decrease in conversion of thyroxine into 3, 5, 3'-tri-iodothyronine by isolated rat renal tubules. Clin Sci (Lond) 62:215–220[Medline]
133. Cavalieri RR, Castle JN, McMahon FA 1984 Effects of dexamethasone on kinetics and distribution of triiodothyronine in the rat. Endocrinology 114:215–221[Abstract/Free Full Text]
134. Miura M, Tanaka K, Komatsu Y, Suda M, Yasoda A, Sakuma Y, Ozasa A, Nakao K 2002 Thyroid hormones promote chondrocyte differentiation in mouse ATDC5 cells and stimulate endochondral ossification in fetal mouse tibias through iodothyronine deiodinases in the growth plate. J Bone Miner Res 17:443–454[CrossRef][Medline]
135. Smith EP, Boyd J, Frank GR, Takahashi H, Cohen RM, Specker B, Williams TC, Lubahn DB, Korach KS 1994 Estrogen resistance caused by a mutation in the estrogen-receptor gene in a man. N Engl J Med 331:1056–1060[Abstract/Free Full Text]
136. Morishima A, Grumbach MM, Simpson ER, Fisher C, Qin K 1995 Aromatase deficiency in male and female siblings caused by a novel mutation and the physiological role of estrogens. J Clin Endocrinol Metab 80:3689–3698[Abstract]
137. Carani C, Qin K, Simoni M, Faustini-Fustini M, Serpente S, Boyd J, Korach KS, Simpson ER 1997 Effect of testosterone and estradiol in a man with aromatase deficiency. N Engl J Med 337:91–95[Free Full Text]
138. Bilezikian JP, Morishima A, Bell J, Grumbach MM 1998 Increased bone mass as a result of estrogen therapy in a man with aromatase deficiency. N Engl J Med 339:599–603[Free Full Text]
139. Grumbach MM 2001 Estrogen, bone, growth and sex: a sea change in conventional wisdom. J Pediatr Endocrinol Metab 13 Suppl 6:1439–1455
140. Juul A 2001 The effects of oestrogens on linear bone growth. Hum Reprod Update 7:303–313[Abstract/Free Full Text]
141. Turner RT, Riggs BL, Spelsberg TC 1994 Skeletal effects of estrogen. Endocr Rev 15:275–300[Abstract/Free Full Text]
142. Gevers EF, Wit JM, Robinson ICAF 1995 Effect of gonadectomy on growth and GH responsiveness in dwarf rats. J Endocrinol 145:69–79[Abstract/Free Full Text]
143. van der Eerden BCJ, Emons J, Ahmed S, van Essen HW, Wit JM, Karperien M 2002 Evidence for genomic and non-genomic actions of estrogens in growth plate regulation in female and male rats at the onset of sexual maturation. J Endocrinol 175:277–288[Abstract]
144. Nilsson O, Falk J, Ritzen EM, Baron J, Savendahl L 2003 Raloxifene acts as an estrogen agonist on the rabbit growth plate. Endocrinology 144:1481–1485[Abstract/Free Full Text]
145. Ornoy A, Giron S, Aner R, Goldstein M, Boyan BD, Schwartz Z 1994 Gender dependent effects of testosterone and 17ß-estradiol on bone growth and remodeling in young mice. Bone Miner 24:43–58[Medline]
146. Strickland AL, Sprinz H 1973 Studies of the influence of estradiol and growth hormone on the hypophysectomized immature rat epiphyseal cartilage growth plate. Am J Obstet Gynecol 115:471–477[Medline]
147. Jansson JO, Eden S, Isaksson O 1983 Sites of action of testosterone and estradiol on longitudinal bone growth. Am J Physiol 244:E135–E140
148. Laron Z, Sarel R, Pertzelan A 1980 Puberty in Laron type dwarfism. Eur J Pediatr 134:79–83[CrossRef][Medline]
149. Braidman IP, Davenport LK, Carter DH, Selby PL, Mawer EB, Freemont AJ 1995 Preliminary in situ identification of estrogen target cells in bone. J Bone Miner Res 10:74–80[Medline]
150. Kusec V, Virdi AS, Prince R, Triffitt JT 1998 Localization of estrogen receptor- in human and rabbit skeletal tissues. J Clin Endocrinol Metab 83:2421–2428[Abstract/Free Full Text]
151. Kennedy J, Baris C, Hoyland JA, Selby PL, Freemont AJ, Braidman IP 1999 Immunofluorescent localization of estrogen receptor- in growth plates of rabbits, but not in rats, at sexual maturity. Bone 24:9–16[Medline]
152. Nilsson LO, Boman A, Savendahl L, Grigelioniene G, Ohlsson C, Ritzen EM, Wroblewski J 1999 Demonstration of estrogen receptor-ß immunoreactivity in human growth plate cartilage. J Clin Endocrinol Metab 84:370–373[Abstract/Free Full Text]
153. Braidman IP, Hainey L, Batra G, Selby PB, Saunders PT, Hoyland JA 2001 Localization of estrogen receptor ß protein expression in adult human bone. J Bone Miner Res 16:214–220[CrossRef][Medline]
154. van der Eerden BCJ, Karperien M, Wit JM 2001 The estrogen receptor in the growth plate: implications for pubertal growth. J Pediatr Endocrinol Metab 14:1527–1533
155. van der Eerden BCJ, Gevers EF, Lowik CW, Karperien M, Wit JM 2002 Expression of estrogen receptor and ß in the epiphyseal plate of the rat. Bone 30:478–485[Medline]
156. Nilsson O, Abad V, Chrysis D, Ritzen EM, Savendahl L, Baron J 2002 Estrogen receptor- and -ß are expressed throughout postnatal development in the rat and rabbit growth plate. J Endocrinol 173:407–414[Abstract]
157. Nilsson O, Chrysis D, Pajulo O, Boman A, Holst M, Rubinstein J, Martin RE, Savendahl L 2003 Localization of estrogen receptors- and -ß and androgen receptor in the human growth plate at different pubertal stages. J Endocrinol 177:319–326[Abstract]
158. Turner RT, Evans GL, Wakley GK 1994 Reduced chondroclast differentiation results in increased cancellous bone volume in estrogen-treated growing rats. Endocrinology 134:461–466[Abstract/Free Full Text]
159. Turner RT, Hannon KS, Demers LM, Buchanan J, Bell NH 1989 Differential effects of gonadal function on bone histomorphometry in male and female rats. J Bone Miner Res 4:557–563[Medline]
160. Sandstedt J, Ohlsson C, Norjavaara E, Nilsson J, Tornell J 1994 Disproportional bone growth and reduced weight gain in gonadectomized male bovine growth hormone transgenic and normal mice. Endocrinology 135:2574–2580[Abstract]
161. Hunziker EB 1988 Growth plate structure and function. Pathol Immunopathol Res 7:9–13[Medline]
162. Corvol MT, Carrascosa A, Tsagris L, Blanchard O, Rappaport R 1987 Evidence for a direct in vitro action of sex steroids on rabbit cartilage cells during skeletal growth: influence of age and sex. Endocrinology 120:1422–1429[Abstract/Free Full Text]
163. Blanchard O, Tsagris L, Rappaport R, Duval-Beaupere G, Corvol M 1991 Age-dependent responsiveness of rabbit and human cartilage cells to sex steroids in vitro. J Steroid Biochem Mol Biol 40:711–716[CrossRef][Medline]
164. Couse JF, Curtis SW, Washburn TF, Lindzey J, Golding TS, Lubahn DB, Smithies O, Korach KS 1995 Analysis of transcription and estrogen insensitivity in the female mouse after targeted disruption of the estrogen receptor gene. Mol Endocrinol 9:1441–1454[Abstract/Free Full Text]
165. Vidal O, Lindberg MK, Hollberg K, Baylink DJ, Andersson G, Lubahn DB, Mohan S, Gustafsson JA, Ohlsson C 2000 Estrogen receptor specificity in the regulation of skeletal growth and maturation in male mice. Proc Natl Acad Sci USA 97:5474–5479[Abstract/Free Full Text]
166. Robertson KM, O’Donnell L, Jones ME, Meachem SJ, Boon WC, Fisher CR, Graves KH, McLachlan RI, Simpson ER 1999 Impairment of spermatogenesis in mice lacking a functional aromatase (cyp 19) gene. Proc Natl Acad Sci USA 96:7986–7991[Abstract/Free Full Text]
167. Korach KS, Taki M, Kimbro K 1997 The effects of estrogen receptor disruption on bone. In: Paoletti R, eds. Women’s health and menopause. Amsterdam: Kluwer Academic Publishers and Fonadanzione Giovanni Lorenzini; 69–73
168. Oz OK, Zerwekh JE, Fisher C, Graves K, Nanu L, Millsaps R, Simpson ER 2000 Bone has a sexually dimorphic response to aromatase deficiency. J Bone Miner Res 15:507–514[CrossRef][Medline]
169. Windahl SH, Vidal O, Andersson G, Gustafsson JA, Ohlsson C 1999 Increased cortical bone mineral content but unchanged trabecular bone mineral density in female ERß(-/-) mice. J Clin Invest 104:895–901[Medline]
170. Lindberg MK, Alatalo SL, Halleen JM, Mohan S, Gustafsson JA, Ohlsson C 2001 Estrogen receptor specificity in the regulation of the skeleton in female mice. J Endocrinol 171:229–236[Abstract]
171. Cassorla FG, Skerda MC, Valk IM, Hung W, Cutler Jr GB, Loriaux DL 1984 The effects of sex steroids on ulnar growth during adolescence. J Clin Endocrinol Metab 58:717–720[Abstract/Free Full Text]
172. Hopwood NJ, Kelch RP, Zipf WB, Hernandez RJ 1979 The effect of synthetic androgens on the hypothalamic-pituitary-gonadal axis in boys with constitutionally delayed growth. J Pediatr 94:657–662[CrossRef][Medline]
173. Coxam V, Bowman BM, Mecham M, Roth CM, Miller MA 1996 Effects of dihydrotestosterone alone and combined with estrogen on bone mineral density, bone growth, and formation rates in ovariectomized rats. Bone 19:107–114[Medline]
174. Zung A, Phillip M, Chalew SA, Palese T, Kowarski AA, Zadik Z 1999 Testosterone effect on growth and growth mediators of the GH-IGF-I axis in the liver and epiphyseal growth plate of juvenile rats. J Mol Endocrinol 23:209–221[Abstract]
175. Ren SG, Malozowski S, Sanchez P, Sweet DE, Loriaux DL, Cassorla F 1989 Direct administration of testosterone increases rat tibial epiphyseal growth plate width. Acta Endocrinol (Copenh) 121:401–405[Abstract/Free Full Text]
176. Maor G, Segev Y, Phillip M 1999 Testosterone stimulates insulin-like growth factor-I and insulin-like growth factor-I-receptor gene expression in the mandibular condyle–a model of endochondral ossification. Endocrinology 140:1901–1910[Abstract/Free Full Text]
177. Phillip M, Maor G, Assa S, Silbergeld A, Segev Y 2001 Testosterone stimulates growth of tibial epiphyseal growth plate and insulin-like growth factor-1 receptor abundance in hypophysectomized and castrated rats. Endocrine 16:1–6[CrossRef][Medline]
178. Yeh S, Tsai MY, Xu Q, Mu XM, Lardy H, Huang KE, Lin H, Yeh SD, Altuwaijri S, Zhou X, Xing L, Boyce BF, Hung MC, Zhang S, Gan L, Chang C, Hung MC 2002 Generation and characterization of androgen receptor knockout (ARKO) mice: an in vivo model for the study of androgen functions in selective tissues. Proc Natl Acad Sci USA 99:13498–13503[Abstract/Free Full Text]
179. Metzger DL, Kerrigan JR 1993 Androgen receptor blockade with flutamide enhances growth hormone secretion in late pubertal males: evidence for independent actions of estrogen and androgen. J Clin Endocrinol Metab 76:1147–1152[Abstract]
180. Nasatzky E, Schwartz Z, Soskolne WA, Brooks BP, Dean DD, Boyan BD, Ornoy A 1994 Evidence for receptors specific for 17 ß-estradiol and testosterone in chondrocyte cultures. Connect Tissue Res 30:277–294[Medline]
181. Abu EO, Horner A, Kusec V, Triffitt JT, Compston JE 1997 The localization of androgen receptors in human bone. J Clin Endocrinol Metab 82:3493–3497[Abstract/Free Full Text]
182. Noble B, Routledge J, Stevens H, Hughes I, Jacobson W 1999 Androgen receptors in bone-forming tissue. Horm Res 51:31–36[CrossRef][Medline]
183. van der Eerden BCJ, van Til NP, Brinkmann AO, Lowik CWGM, Wit JM, Karperien M 2002 Sex differences in the expression of the androgen receptor in the tibial growth plate and metaphyseal bone of the rat. Bone 30:891–896[Medline]
184. Labrie F, Luu-The V, Lin SX, Simard J, Labrie C, El Alfy M, Pelletier G, Belanger A 2000 Intracrinology: role of the family of 17 ß-hydroxysteroid dehydrogenases in human physiology and disease. J Mol Endocrinol 25:1–16[Abstract]
185. Simpson E, Rubin G, Clyne C, Robertson K, O’Donnell L, Jones M, Davis S 2000 The role of local estrogen biosynthesis in males and females. Trends Endocrinol Metab 11:184–188[CrossRef][Medline]
186. Labrie C, Belanger A, Labrie F 1988 Androgenic activity of dehydroepiandrosterone and androstenedione in the rat ventral prostate. Endocrinology 123:1412–1417[Abstract/Free Full Text]
187. Labrie F 1991 Intracrinology. Mol Cell Endocrinol 78:C113–C118
188. Schweikert HU, Wolf L, Romalo G 1995 Oestrogen formation from androstenedione in human bone. Clin Endocrinol (Oxf) 43:37–42[Medline]
189. Dong Y, Qiu QQ, Debear J, Lathrop WF, Bertolini DR, Tamburini PP 1998 17ß-Hydroxysteroid dehydrogenases in human bone cells. J Bone Miner Res 13:1539–1546[CrossRef][Medline]
190. Saito H, Yanaihara T 1998 Steroid formation in osteoblast-like cells. J Int Med Res 26:1–12[Medline]
191. Eyre LJ, Bland R, Bujalska IJ, Sheppard MC, Stewart PM, Hewison M 1998 Characterization of aromatase and 17 ß-hydroxysteroid dehydrogenase expression in rat osteoblastic cells. J Bone Miner Res 13:996–1004[CrossRef][Medline]
192. Janssen JM, Bland R, Hewison M, Coughtrie MW, Sharp S, Arts J, Pols HA, van Leeuwen JP 1999 Estradiol formation by human osteoblasts via multiple pathways: relation with osteoblast function. J Cell Biochem 75:528–537[CrossRef][Medline]
193. Feix M, Wolf L, Schweikert HU 2001 Distribution of 17ß-hydroxysteroid dehydrogenases in human osteoblast-like cells. Mol Cell Endocrinol 171:163–164[CrossRef][Medline]
194. Sasano H, Uzuki M, Sawai T, Nagura H, Matsunaga G, Kashimoto O, Harada N 1997 Aromatase in human bone tissue. J Bone Miner Res 12:1416–1423[CrossRef][Medline]
195. Oz OK, Millsaps R, Welch R, Welch R, Birch J, Birch J, Zerwekh JE 2001 Expression of aromatase in the human growth plate. J Mol Endocrinol 27:249–253[Abstract]
196. van der Eerden BCJ, van de Ven J, Lowik CWGM, Wit JM, Karperien M 2002 Sex steroid formation in the growth plate of the rat. Endocrinology 143:4048–4053[Abstract/Free Full Text]
197. Schwartz Z, Ehland H, Sylvia VL, Larsson D, Hardin RR, Bingham V, Lopez D, Dean DD, Boyan BD 2002 1,25-dihydroxyvitamin D(3) and 24R,25-dihydroxyvitamin D(3) modulate growth plate chondrocyte physiology via protein kinase C-dependent phosphorylation of extracellular signal-regulated kinase 1/2 mitogen-activated protein kinase. Endocrinology 143:2775–2786[Abstract/Free Full Text]
198. Boyan BD, Sylvia VL, Dean DD, Pedrozo H, Del Toro F, Nemere I, Posner GH, Schwartz Z 1999 1,25-(OH)2D3 modulates growth plate chondrocytes via membrane receptor-mediated protein kinase C by a mechanism that involves changes in phospholipid metabolism and the action of arachidonic acid and PGE2. Steroids 64:129–136[CrossRef][Medline]
199. Krohn K, Haffner D, Hugel U, Himmele R, Klaus G, Mehls O, Schaefer F2003 1,25(OH)(2)D(3) And dihydrotestosterone interact to regulate proliferation and differentiation of epiphyseal chondrocytes. Calcif Tissue Int 73:400–410
200. De Luca F, Barnes KM, Uyeda JA, De Levi S, Abad V, Palese T, Mericq V, Baron J 2001 Regulation of growth plate chondrogenesis by bone morphogenetic protein-2. Endocrinology 142:430–436[Abstract/Free Full Text]
201. Steppan CM, Crawford DT, Chidsey-Frink KL, Ke H, Swick AG 2000 Leptin is a potent stimulator of bone growth in ob/ob mice. Regul Pept 92:73–78[CrossRef][Medline]
202. Phillip M, Moran O, Lazar L 2002 Growth without growth hormone. J Pediatr Endocrinol Metab 15(Suppl 5):1267–1272
203. Maor G, Rochwerger M, Segev Y, Phillip M 2002 Leptin acts as a growth factor on the chondrocytes of skeletal growth centers. J Bone Miner Res 17:1034–1043[CrossRef][Medline]
204. Cornish J, Callon KE, Bava U, Lin C, Naot D, Hill BL, Grey AB, Broom N, Myers DE, Nicholson GC, Reid IR 2002 Leptin directly regulates bone cell function in vitro and reduces bone fragility in vivo. J Endocrinol 175:405–415[Abstract]
205. Nakajima R, Inada H, Koike T, Yamano T 2003 Effects of leptin to cultured growth plate chondrocytes. Horm Res 60:91–98[CrossRef][Medline]
206. Suzuki F 1996 Roles of cartilage matrix proteins, chondromodulin-I and -II, in endochondral bone formation: a review. Connect Tissue Res 35:303–307[Medline]
207. Chusho H, Tamura N, Ogawa Y, Yasoda A, Suda M, Miyazawa T, Nakamura K, Nakao K, Kurihara T, Komatsu Y, Itoh H, Tanaka K, Saito Y, Katsuki M, Nakao K 2001 Dwarfism and early death in mice lacking C-type natriuretic peptide. Proc Natl Acad Sci USA 98:4016–4021[Abstract/Free Full Text]
208. Grumbles RM, Howell DS, Wenger L, Altman RD, Howard GA, Roos BA 1996 Hepatocyte growth factor and its actions in growth plate chondrocytes. Bone 19:255–261[Medline]
209. Yang Y, Topol L, Lee H, Wu J 2003 Wnt5a and Wnt5b exhibit distinct activities in coordinating chondrocyte proliferation and differentiation. Development 130:1003–1015[Abstract/Free Full Text]
210. Stone DM, Hynes M, Armanini M, Swanson TA, Gu Q, Johnson RL, Scott MP, Pennica D, Goddard A, Phillips H, Noll M, Hooper JE, de Sauvage F, Rosenthal A 1996 The tumour-suppressor gene patched encodes a candidate receptor for Sonic hedgehog. Nature 384:129–134[CrossRef][Medline]
211. van den Heuvel M, Ingham PW 1996 Smoothened encodes a receptor-like serpentine protein required for hedgehog signalling. Nature 382:547–551[CrossRef][Medline]
212. Ingham PW, McMahon AP 2001 Hedgehog signaling in animal development: paradigms and principles. Genes Dev 15:3059–3087[Free Full Text]
213. Vortkamp A, Lee K, Lanske B, Segre GV, Kronenberg HM, Tabin CJ 1996 Regulation of rate of cartilage differentiation by Indian hedgehog and PTH-related protein. Science 273:613–622[Abstract]
214. Vortkamp A, Pathi S, Peretti GM, Caruso EM, Zaleske DJ, Tabin CJ 1998 Recapitulation of signals regulating embryonic bone formation during postnatal growth and in fracture repair. Mech Dev 71:65–76[CrossRef][Medline]
215. St Jacques B, Hammerschmidt M, McMahon AP 1999 Indian hedgehog signaling regulates proliferation and differentiation of chondrocytes and is essential for bone formation. Genes Dev 13:2072–2086[Abstract/Free Full Text]
216. Karp SJ, Schipani E, St Jacques B, Hunzelman J, Kronenberg H, McMahon AP 2000 Indian hedgehog coordinates endochondral bone growth and morphogenesis via parathyroid hormone related-protein-dependent and -independent pathways. Development 127:543–548[Abstract]
217. Suva LJ, Winslow GA, Wettenhall RE, Hammonds RG, Moseley JM, Diefenbach-Jagger H, Rodda CP, Kemp BE, Rodriguez H, Chen EY, Hudson PJ, Martin TJ, Wood WI 1987 A parathyroid hormone-related protein implicated in malignant hypercalcemia: cloning and expression. Science 237:893–896[Abstract/Free Full Text]
218. Jüppner H, Abou-Samra A-B, Freeman M, Kong XF, Schipani E, Richards J, Kolakowski Jr LF, Hock J, Potts Jr JT, Kronenberg HM, Segre GV 1991 A G protein-linked receptor for parathyroid hormone and parathyroid hormone-related peptide. Science 254:1024–1026[Abstract/Free Full Text]
219. Karaplis AC, Luz A, Glowacki J, Bronson RT, Tybulewicz VL, Kronenberg HM, Mulligan RC 1994 Lethal skeletal dysplasia from targeted disruption of the parathyroid hormone-related peptide gene. Genes Dev 8:277–289[Abstract/Free Full Text]
220. Weir EC, Philbrick WM, Amling M, Neff LA, Baron R, Broadus AE 1996 Targeted overexpression of parathyroid hormone-related peptide in chondrocytes causes chondrodysplasia and delayed endochondral bone formation. Proc Natl Acad Sci USA 93:10240–10245[Abstract/Free Full Text]
221. Lanske B, Karaplis AC, Lee K, Luz A, Vortkamp A, Pirro A, Karperien M, Defize LHK, Ho C, Mulligan RC, Abou-Samra AB, Juppner H, Segre GV, Kronenberg HM 1996 PTH/PTHrP receptor in early development and Indian hedgehog-regulated bone growth. Science 273:663–666[Abstract]
222. Jansen M 1934 Uber atypische chondrodystrophie (achondroplasie). Z Orthop Chir 61:253–286
223. Schipani E, Kruse K, Jüppner H 1995 A constitutively active mutant PTH-PTHrP receptor in Jansen-type metaphyseal chondrodysplasia. Science 268:98–100[Abstract/Free Full Text]
224. Jobert AS, Zhang P, Couvineau A, Bonaventure J, Roume J, Le Merrer M, Silve C 1998 Absence of functional receptors for parathyroid hormone and parathyroid hormone-related peptide in Blomstrand chondrodysplasia. J Clin Invest 102:34–40[Medline]
225. Karperien M, van der Harten HJ, van Schooten R, Farih-Sips H, den Hollander NS, Kneppers SL, Nijweide P, Papapoulos SE, Lowik CW 1999 A frame-shift mutation in the type I parathyroid hormone (PTH)/PTH-related peptide receptor causing Blomstrand lethal osteochondrodysplasia. J Clin Endocrinol Metab 84:3713–3720[Abstract/Free Full Text]
226. Oostra RJ, van der Harten JJ, Rijnders WP, Scott RJ, Young MP, Trump D 2000 Blomstrand osteochondrodysplasia: three novel cases and histological evidence for heterogeneity. Virchows Arch 436:28–35[CrossRef][Medline]
227. Karperien M, Lanser P, de Laat SW, Boonstra J, Defize LH 1996 Parathyroid hormone related peptide mRNA expression during murine postimplantation development: evidence for involvement in multiple differentiation processes. Int J Dev Biol 40:599–608[Medline]
228. Lee K, Deeds JD, Segre GV 1995 Expression of parathyroid hormone-related peptide and its messenger ribonucleic acids during fetal development of rats. Endocrinology 136:453–463[Abstract]
229. Karperien M, van Dijk TB, Hoeijmakers T, Cremers F, Abou-Samra AB, Boonstra J, de Laat SW, Defize LH 1994 Expression pattern of parathyroid hormone/parathyroid hormone related peptide receptor mRNA in mouse postimplantation embryos indicates involvement in multiple developmental processes. Mech Dev 47:29–42[CrossRef][Medline]
230. Szebenyi G, Fallon JF 1999 Fibroblast growth factors as multifunctional signaling factors. Int Rev Cytol 185:45–106[Medline]
231. Ornitz DM, Marie PJ 2002 FGF signaling pathways in endochondral and intramembranous bone development and human genetic disease. Genes Dev 16:1446–1465[Free Full Text]
232. Leach Jr RM, Sokol C, McMurtry JP 1997 Immunolocalization of basic fibroblast growth factor in porcine epiphyseal growth plate. Domest Anim Endocrinol 14:129–132[CrossRef][Medline]
233. Jingushi S, Scully SP, Joyce ME, Sugioka Y, Bolander ME 1995 Transforming growth factor-ß 1 and fibroblast growth factors in rat growth plate. J Orthop Res 13:761–768[CrossRef][Medline]
234. Peters KG, Werner S, Chen G, Williams LT 1992 Two FGF receptor genes are differentially expressed in epithelial and mesenchymal tissues during limb formation and organogenesis in the mouse. Development 114:233–243[Abstract]
235. Peters K, Ornitz D, Werner S, Williams L 1993 Unique expression pattern of the FGF receptor 3 gene during mouse organogenesis. Dev Biol 155:423–430[CrossRef][Medline]
236. Shiang R, Thompson LM, Zhu Y-Z, Church DM, Fielder TJ, Bocian M, Winokur ST, Wasmuth JJ 1994 Mutations in the transmembrane domain of FGFR3 cause the most common genetic form of dwarfism, achondrodysplasia. Cell 78:335–342[CrossRef][Medline]
237. Rousseau F, Bonaventure J, Legeai-Mallet L, Pelet A, Rozet JM, Maroteaux P, Le Merrer M, Munnich A 1994 Mutations in the gene encoding fibroblast growth factor receptor-3 in achondroplasia. Nature 371:252–254[CrossRef][Medline]
238. Vajo Z, Francomano CA, Wilkin DJ 2000 The molecular and genetic basis of fibroblast growth factor receptor 3 disorders: the achondroplasia family of skeletal dysplasias, Muenke craniosynostosis, and Crouzon syndrome with acanthosis nigricans. Endocr Rev 21:23–39[Abstract/Free Full Text]
239. Spranger J 1988 Bone dysplasia ‘families’. Pathol Immunopathol Res 7:76–80[Medline]
240. Francomano CA, McIntosh I, Wilkin DJ 1996 Bone dysplasias in man: molecular insights. Curr Opin Genet Dev 6:301–308[CrossRef][Medline]
241. Deng C, Wynshaw-Boris A, Zhou F, Kuo A, Leder P 1996 Fibroblast growth factor receptor 3 is a negative regulator of bone growth. Cell 84:911–921[CrossRef][Medline]
242. Colvin JS, Bohne BA, Harding GW, McEwen DG, Ornitz DM 1996 Skeletal overgrowth and deafness in mice lacking fibroblast growth factor receptor 3. Nat Genet 12:390–397[CrossRef][Medline]
243. Coffin JD, Florkiewicz RZ, Neumann J, Mort-Hopkins T, Dorn GW, Lightfoot P, German R, Howles PN, Kier A, O’Toole BA 1995 Abnormal bone growth and selective translational regulation in basic fibroblast growth factor (FGF-2) transgenic mice. Mol Biol Cell 6:1861–1873[Abstract]
244. Liu Z, Xu J, Colvin JS, Ornitz DM 2002 Coordination of chondrogenesis and osteogenesis by fibroblast growth factor 18. Genes Dev 16:859–869[Abstract/Free Full Text]
245. Mancilla EE, De Luca F, Uyeda JA, Czerwiec FS, Baron J 1998 Effects of fibroblast growth factor-2 on longitudinal bone growth. Endocrinology 139:2900–2904[Abstract/Free Full Text]
246. Chen L, Li C, Qiao W, Xu X, Deng C 2001 A Ser(365) Cys mutation of fibroblast growth factor receptor 3 in mouse downregulates Ihh/PTHrP signals and causes severe achondroplasia. Hum Mol Genet 10:457–465[Abstract/Free Full Text]
247. Reddi AH 2001 Bone morphogenetic proteins: from basic science to clinical applications. J Bone Joint Surg Am 83-A Suppl 1:S1–S6
248. Lyons KM, Pelton RW, Hogan BLM 1989 Patterns of expression of murine Vgr-1 and BMP-2a RNA suggests that transforming growth factor-ß-like genes coordinately regulate aspects of embryonic development. Genes Dev 3:1657–1668[Abstract/Free Full Text]
249. Lyons KM, Pelton RW, Hogan BL 1990 Organogenesis and pattern formation in the mouse: RNA distribution patterns suggest a role for bone morphogenetic protein-2A (BMP-2A). Development 109:833–844[Abstract/Free Full Text]
250. Jones CM, Lyons KM, Hogan BL 1991 Involvement of bone morphogenetic protein-4 (BMP-4) and Vgr-1 in morphogenesis and neurogenesis in the mouse. Development 111:531–542[Abstract]
251. Macias D, Ganan Y, Sampath TK, Piedra ME, Ros MA, Hurle JM 1997 Role of BMP-2 and OP-1 (BMP-7) in programmed cell death and skeletogenesis during chick limb development. Development 124:1109–1117[Abstract]
252. Grimsrud CD, Romano PR, D’Souza M, Puzas JE, Reynolds PR, Rosier RN, O’Keefe RJ 1999 BMP-6 is an autocrine stimulator of chondrocyte differentiation. J Bone Miner Res 14:475–482[CrossRef][Medline]
253. Haaijman A, Karperien M, Lanske B, Hendriks J, Lowik CW, Bronckers AL, Burger EH 1999 Inhibition of terminal chondrocyte differentiation by bone morphogenetic protein 7 (OP-1) in vitro depends on the periarticular region but is independent of parathyroid hormone-related peptide. Bone 25:397–404[Medline]
254. Zou H, Wieser R, Massagué J, Niswander L 1997 Distinct roles of type I bone morphogenetic protein receptors in the formation and differentiation of cartilage. Genes Dev 11:2191–2203[Abstract/Free Full Text]
255. Chubinskaya S, Kuettner KE 2003 Regulation of osteogenic proteins by chondrocytes. Int J Biochem Cell Biol 35:1323–1340[CrossRef][Medline]
256. Zhang H, Bradley A 1996 Mice deficient for BMP2 are nonviable and have defects in amnion/chorion and cardiac development. Development 122:2977–2986[Abstract]
257. Winnier G, Blessing M, Labosky PA, Hogan BL 1995 Bone morphogenetic protein-4 is required for mesoderm formation and patterning in the mouse. Genes Dev 9:2105–2116[Abstract/Free Full Text]
258. King JA, Storm EE, Marker PC, Dileone RJ, Kingsley DM 1996 The role of BMPs and GDFs in development of region-specific skeletal structures. Ann NY Acad Sci 785:70–79[Medline]
259. Bailon-Plaza A, Lee AO, Veson EC, Farnum CE, van der Meulen MC 1999 BMP-5 deficiency alters chondrocytic activity in the mouse proximal tibial growth plate. Bone 24:211–216[Medline]
260. Storm EE, Kingsley DM 1999 GDF5 coordinates bone and joint formation during digit development. Dev Biol 209:11–27[CrossRef][Medline]
261. Buxton P, Edwards C, Archer CW, Francis-West P 2001 Growth/differentiation factor-5 (GDF-5) and skeletal development. J Bone Joint Surg Am 83-A Suppl 1:S23–S30
262. Yi SE, Daluiski A, Pederson R, Rosen V, Lyons KM 2000 The type I BMP receptor BMPRIB is required for chondrogenesis in the mouse limb. Development 127:621–630[Abstract]
263. Thomas JT, Lin K, Nandedkar M, Camargo M, Cervenka J, Luyten FP 1996 A human chondrodysplasia due to a mutation in a TGF-ß superfamily member. Nat Genet 12:315–317[CrossRef][Medline]
264. Polinkovsky A, Robin NH, Thomas JT, Irons M, Lynn A, Goodman FR, Reardon W, Kant SG, Brunner HG, van der Burgt I, Chitayat D, McGaughran J, Donnai D, Luyten FP, Warman ML 1997 Mutations in CDMP1 cause autosomal dominant brachydactyly type C. Nat Genet 17:18–19[CrossRef][Medline]
265. Thomas JT, Kilpatrick MW, Lin K, Erlacher L, Lembessis P, Costa T, Tsipouras P, Luyten FP 1997 Disruption of human limb morphogenesis by a dominant negative mutation in CDMP1. Nat Genet 17:58–64[CrossRef][Medline]
266. Gong Y, Krakow D, Marcelino J, Wilkin D, Chitayat D, Babul-Hirji R, Hudgins L, Cremers CW, Cremers FP, Brunner HG, Reinker K, Rimoin DL, Cohn DH, Goodman FR, Reardon W, Patton M, Francomano CA, Warman ML 1999 Heterozygous mutations in the gene encoding noggin affect human joint morphogenesis. Nat Genet 21:302–304[CrossRef][Medline]
267. Leboy PS, LuValle P, Volk SW 1998 BMP regulation of type X collagen gene transcription during chondrocyte hypertrophy. Bone 23:S243
268. Solloway MJ, Dudley AT, Bikoff EK, Lyons KM, Hogan BL, Robertson EJ 1998 Mice lacking Bmp6 function. Dev Genet 22:321–339[CrossRef][Medline]
269. Minina E, Wenzel HM, Kreschel C, Karp S, Gaffield W, McMahon AP, Vortkamp A 2001 BMP and Ihh/PTHrP signaling interact to coordinate chondrocyte proliferation and differentiation. Development 128:4523–4534
270. Serra R, Karaplis A, Sohn P 1999 Parathyroid hormone-related peptide (PTHrP)-dependent and -independent effects of transforming growth factor ß (TGF-ß) on endochondral bone formation. J Cell Biol 145:783–794[Abstract/Free Full Text]
271. Alvarez J, Sohn P, Zeng X, Doetschman T, Robbins DJ, Serra R 2002 TGFß2 mediates the effects of hedgehog on hypertrophic differentiation and PTHrP expression. Development 129:1913–1924
272. Ferrara N, Davis-Smyth T 1997 The biology of vascular endothelial growth factor. Endocr Rev 18:4–25[Abstract/Free Full Text]
273. Haigh JJ, Gerber HP, Ferrara N, Wagner EF 2000 Conditional inactivation of VEGF-A in areas of collagen2a1 expression results in embryonic lethality in the heterozygous state. Development 127:1445–1453[Abstract]
274. Gerber HP, Ferrara N 2000 Angiogenesis and bone growth. Trends Cardiovasc Med 10:223–228[CrossRef][Medline]
275. Carlevaro MF, Albini A, Ribatti D, Gentili C, Benelli R, Cermelli S, Cancedda R, Cancedda FD 1997 Transferrin promotes endothelial cell migration and invasion: implication in cartilage neovascularization. J Cell Biol 136:1375–1384[Abstract/Free Full Text]
276. Hiraki Y, Inoue H, Iyama K, Kamizono A, Ochiai M, Shukunami C, Iijima S, Suzuki F, Kondo J 1997 Identification of chondromodulin I as a novel endothelial cell growth inhibitor. Purification and its localization in the avascular zone of epiphyseal cartilage. J Biol Chem 272:32419–32426[Abstract/Free Full Text]
277. Baron J, Klein KO, Yanovski JA, Novosad JA, Bacher JD, Bolander ME, Cutler Jr GB 1994 Induction of growth plate cartilage ossification by basic fibroblast growth factor. Endocrinology 135:2790–2793[Abstract]
278. Semenza GL, Agani F, Iyer N, Kotch L, Laughner E, Leung S, Yu A 1999 Regulation of cardiovascular development and physiology by hypoxia-inducible factor 1. Ann NY Acad Sci 874:262–268[CrossRef][Medline]
279. Takeda S, Bonnamy JP, Owen MJ, Ducy P, Karsenty G 2001 Continuous expression of Cbfa1 in nonhypertrophic chondrocytes uncovers its ability to induce hypertrophic chondrocyte differentiation and partially rescues Cbfa1-deficient mice. Genes Dev 15:467–481[Abstract/Free Full Text]
280. Ueta C, Iwamoto M, Kanatani N, Yoshida C, Liu Y, Enomoto-Iwamoto M, Ohmori T, Enomoto H, Nakata K, Takada K, Kurisu K, Komori T 2001 Skeletal malformations caused by overexpression of Cbfa1 or its dominant negative form in chondrocytes. J Cell Biol 153:87–100[Abstract/Free Full Text]
281. Takamoto M, Tsuji K, Yamashita T, Sasaki H, Yano T, Taketani Y, Komori T, Nifuji A, Noda M 2003 Hedgehog signaling enhances core-binding factor 1 and receptor activator of nuclear factor-B ligand (RANKL) gene expression in chondrocytes. J Endocrinol 177:413–421[Abstract]
282. Karsenty G, Wagner EF 2002 Reaching a genetic and molecular understanding of skeletal development. Dev Cell 2:389–406[CrossRef][Medline]
283. Zelzer E, Glotzer DJ, Hartmann C, Thomas D, Fukai N, Soker S, Olsen BR 2001 Tissue specific regulation of VEGF expression during bone development requires Cbfa1/Runx2. Mech Dev 106:97–106[CrossRef][Medline]
284. Iwasaki M, Le AX, Helms JA 1997 Expression of Indian hedgehog, bone morphogenetic protein 6 and gli during skeletal morphogenesis. Mech Dev 69:197–202[CrossRef][Medline]
285. Kartsogiannis V, Moseley J, McKelvie B, Chou ST, Hards DK, Ng KW, Martin TJ, Zhou H 1997 Temporal expression of PTHrP during endochondral bone formation in mouse and intramembranous bone formation in an in vivo rabbit model. Bone 21:385–392[Medline]
286. Murakami S, Noda M 2000 Expression of Indian hedgehog during fracture healing in adult rat femora. Calcif Tissue Int 66:272–276[CrossRef][Medline]
287. Stevens DA, Hasserjian RP, Robson H, Siebler T, Shalet SM, Williams GR 2000 Thyroid hormones regulate hypertrophic chondrocyte differentiation and expression of parathyroid hormone-related peptide and its receptor during endochondral bone formation. J Bone Miner Res 15:2431–2442[CrossRef][Medline]
288. Farquharson C, Jefferies D, Seawright E, Houston B 2001 Regulation of chondrocyte terminal differentiation in the postembryonic growth plate: the role of the PTHrP-Indian hedgehog axis. Endocrinology 142:4131–4140[Abstract/Free Full Text]
289. Nakase T, Miyaji T, Kuriyama K, Tamai N, Horiki M, Tomita T, Myoui A, Shimada K, Yoshikawa H 2001 Immunohistochemical detection of parathyroid hormone-related peptide, Indian hedgehog, and patched in the process of endochondral ossification in the human. Histochem Cell Biol 116:277–284[Medline]
290. van der Eerden BCJ, Karperien M, Gevers EF, Lowik CW, Wit JM 2000 Expression of Indian hedgehog, parathyroid hormone-related protein, and their receptors in the postnatal growth plate of the rat: evidence for a locally acting growth restraining feedback loop after birth. J Bone Miner Res 15:1045–1055[CrossRef][Medline]
291. Bostrom MP, Lane JM, Berberian WS, Missri AA, Tomin E, Weiland A, Doty SB, Glaser D, Rosen VM 1995 Immunolocalization and expression of bone morphogenetic proteins 2 and 4 in fracture healing. J Orthop Res 13:357–367[CrossRef][Medline]
292. Houston B, Thorp BH, Burt DW 1994 Molecular cloning and expression of bone morphogenetic protein-7 in the chick epiphyseal growth plate. J Mol Endocrinol 13:289–301[Abstract/Free Full Text]
293. Yazaki Y, Matsunaga S, Onishi T, Nagamine T, Origuchi N, Yamamoto T, Ishidou Y, Imamura T, Sakou T 1998 Immunohistochemical localization of bone morphogenetic proteins and the receptors in epiphyseal growth plate. Anticancer Res 18:2339–2344[Medline]
294. Praul CA, Ford BC, Leach RM 2002 Effect of fibroblast growth factors 1, 2, 4, 5, 6, 7, 8, 9, and 10 on avian chondrocyte proliferation. J Cell Biochem 84:359–366[CrossRef][Medline]
295. Kishimoto J, Ehama R, Ge Y, Kobayashi T, Nishiyama T, Detmar M, Burgeson RE 2000 In vivo detection of human vascular endothelial growth factor promoter activity in transgenic mouse skin. Am J Pathol 157:103–110[Abstract/Free Full Text]
296. Ichigatani M, Saga T, Yamaki K, Yoshizuka M 2001 Appearance of vascular endothelial growth factor (VEGF) in femoral head in the growing rat. Histol Histopathol 16:463–468[Medline]
297. Le Merrer M, Legeai-Mallet L, Jeannin PM, Horsthemke B, Schinzel A, Plauchu H, Toutain A, Achard F, Munnich A, Maroteaux P 1994 A gene for hereditary multiple exostoses maps to chromosome 19p. Hum Mol Genet 3:717–722[Abstract/Free Full Text]
298. Ludecke HJ, Wagner MJ, Nardmann J, La Pillo B, Parrish JE, Willems PJ, Haan EA, Frydman M, Hamers GJ, Wells DE 1995 Molecular dissection of a contiguous gene syndrome: localization of the genes involved in the Langer-Giedion syndrome. Hum Mol Genet 4:31–36[Abstract/Free Full Text]
299. Porter DE, Emerton ME, Villanueva-Lopez F, Simpson AH 2000 Clinical and radiographic analysis of osteochondromas and growth disturbance in hereditary multiple exostoses. J Pediatr Orthop 20:246–250[CrossRef][Medline]
300. McCormick C, Duncan G, Goutsos KT, Tufaro F 2000 The putative tumor suppressors EXT1 and EXT2 form a stable complex that accumulates in the Golgi apparatus and catalyzes the synthesis of heparan sulfate. Proc Natl Acad Sci USA 97:668–673[Abstract/Free Full Text]
301. Duncan G, McCormick C, Tufaro F 2001 The link between heparan sulfate and hereditary bone disease: finding a function for the EXT family of putative tumor suppressor proteins. J Clin Invest 108:511–516[CrossRef][Medline]
302. Hecht JT, Hall CR, Snuggs M, Hayes E, Haynes R, Cole WG 2002 Heparan sulfate abnormalities in exostosis growth plates. Bone 31:199–204[Medline]
303. Hopyan S, Gokgoz N, Poon R, Gensure RC, Yu C, Cole WG, Bell RS, Juppner H, Andrulis IL, Wunder JS, Alman BA 2002 A mutant PTH/PTHrP type I receptor in enchondromatosis. Nat Genet 30:306–310[CrossRef][Medline]
304. Bakker B, van der Eerden BC, Koppenaal DW, Karperien M, Wit JM 2003 Effect of x-irradiation on growth and the expression of parathyroid hormone-related peptide and Indian hedgehog in the tibial growth plate of the rat. Horm Res 59:35–41
305. Schipani E, Lanske B, Hunzelman J, Luz A, Kovacs CS, Lee K, Pirro A, Kronenberg HM, Juppner H 1997 Targeted expression of constitutively active receptors for parathyroid hormone and parathyroid hormone-related peptide delays endochondral bone formation and rescues mice that lack parathyroid hormone-related peptide. Proc Natl Acad Sci USA 94:13689–13694[Abstract/Free Full Text]
306. Kindblom JM, Nilsson O, Ohlsson C, Savendahl L 2002 Expression and localization of Indian hedgehog (Ihh) and parathyroid hormone related protein (PTHrP) in the human growth plate during pubertal development. J Endocrinol 174:R1–R6
307. Paspaliaris V, Petersen DN, Thiede MA 1995 Steroid regulation of parathyroid hormone-related protein expression and action in the rat uterus. J Steroid Biochem Mol Biol 53:259–265[CrossRef][Medline]

This article has been cited by other articles:

				M. J. E. Wassenaar, O. M. Dekkers, A. M. Pereira, J. M. Wit, J. W. Smit, N. R. Biermasz, and J. A. Romijn Impact of the Exon 3-Deleted Growth Hormone (GH) Receptor Polymorphism on Baseline Height and the Growth Response to Recombinant Human GH Therapy in GH-Deficient (GHD) and Non-GHD Children with Short Stature: A Systematic Review and Meta-Analysis J. Clin. Endocrinol. Metab., October 1, 2009; 94(10): 3721 - 3730. [Abstract] [Full Text] [PDF]

				I. Mohamed and J. K Yeh Alfacalcidol prevents aromatase inhibitor (Letrozole)-induced bone mineral loss in young growing female rats J. Endocrinol., August 1, 2009; 202(2): 317 - 325. [Abstract] [Full Text] [PDF]

				C. Ohlsson, S. Mohan, K. Sjogren, A. Tivesten, J. Isgaard, O. Isaksson, J.-O. Jansson, and J. Svensson The Role of Liver-Derived Insulin-Like Growth Factor-I Endocr. Rev., August 1, 2009; 30(5): 494 - 535. [Abstract] [Full Text] [PDF]

				K. K Ong, M. Langkamp, M. B Ranke, K. Whitehead, I. A Hughes, C. L Acerini, and D. B Dunger Insulin-like growth factor I concentrations in infancy predict differential gains in body length and adiposity: the Cambridge Baby Growth Study Am. J. Clinical Nutrition, July 1, 2009; 90(1): 156 - 161. [Abstract] [Full Text] [PDF]

				M. A. Serrat, R. M. Williams, and C. E. Farnum Temperature alters solute transport in growth plate cartilage measured by in vivo multiphoton microscopy J Appl Physiol, June 1, 2009; 106(6): 2016 - 2025. [Abstract] [Full Text] [PDF]

				J H D. Bassett and G. R Williams The skeletal phenotypes of TR{alpha} and TR{beta} mutant mice J. Mol. Endocrinol., April 1, 2009; 42(4): 269 - 282. [Abstract] [Full Text] [PDF]

				T. Scharschmidt, R. Jacquet, D. Weiner, E. Lowder, T. Schrickel, and W. J. Landis Gene Expression in Slipped Capital Femoral Epiphysis. Evaluation with Laser Capture Microdissection and Quantitative Reverse Transcription-Polymerase Chain Reaction J. Bone Joint Surg. Am., February 1, 2009; 91(2): 366 - 377. [Abstract] [Full Text] [PDF]

				T. Matsushita, W. R. Wilcox, Y. Y. Chan, A. Kawanami, H. Bukulmez, G. Balmes, P. Krejci, P. B. Mekikian, K. Otani, I. Yamaura, et al. FGFR3 promotes synchondrosis closure and fusion of ossification centers through the MAPK pathway Hum. Mol. Genet., January 15, 2009; 18(2): 227 - 240. [Abstract] [Full Text] [PDF]

				P. R. Ferket, E. O. Oviedo-Rondon, P. L. Mente, D. V. Bohorquez, A. A. Santos Jr., J. L. Grimes, J. D. Richards, J. J. Dibner, and V. Felts Organic trace minerals and 25-hydroxycholecalciferol affect performance characteristics, leg abnormalities, and biomechanical properties of leg bones of turkeys, Poult. Sci., January 1, 2009; 88(1): 118 - 131. [Abstract] [Full Text] [PDF]

				T. C R Prickett, G. K Barrell, M. Wellby, T. G Yandle, A M. Richards, and E. A Espiner Effect of sex steroids on plasma C-type natriuretic peptide forms: stimulation by oestradiol in lambs and adult sheep J. Endocrinol., December 1, 2008; 199(3): 481 - 487. [Abstract] [Full Text] [PDF]

				K. E. Govoni, J. E. Wergedal, R. B. Chadwick, A. K. Srivastava, and S. Mohan Prepubertal OVX increases IGF-I expression and bone accretion in C57BL/6J mice Am J Physiol Endocrinol Metab, November 1, 2008; 295(5): E1172 - E1180. [Abstract] [Full Text] [PDF]

				K. Nakagawa, E. C. Perez, J. Oh, F. Santos, A. Geldyyev, M.-L. Gross, F. Schaefer, and C. P. Schmitt Cinacalcet does not affect longitudinal growth but increases body weight gain in experimental uraemia Nephrol. Dial. Transplant., September 1, 2008; 23(9): 2761 - 2767. [Abstract] [Full Text] [PDF]

				P. J King, L. Guasti, and E. Laufer Hedgehog signalling in endocrine development and disease J. Endocrinol., September 1, 2008; 198(3): 439 - 450. [Abstract] [Full Text] [PDF]

				A. Giustina, G. Mazziotti, and E. Canalis Growth Hormone, Insulin-Like Growth Factors, and the Skeleton Endocr. Rev., August 1, 2008; 29(5): 535 - 559. [Abstract] [Full Text] [PDF]

				E. O. Oviedo-Rondon, J. Small, M. J. Wineland, V. L. Christensen, J. L. Grimes, S. V. L. Funderburk, D. T. Ort, and K. M. Mann Effects of Incubator Temperature and Oxygen Concentration During the Plateau Stage of Oxygen Consumption on Turkey Embryo Long Bone Development Poult. Sci., August 1, 2008; 87(8): 1484 - 1492. [Abstract] [Full Text] [PDF]

				P Zhang, G M Malacinski, and H Yokota Joint loading modality: its application to bone formation and fracture healing Br. J. Sports Med., July 1, 2008; 42(7): 556 - 560. [Abstract] [Full Text] [PDF]

				T. Tsutsumi, H. Kuwabara, T. Arai, Y. Xiao, and J. A. DeCaprio Disruption of the Fbxw8 Gene Results in Pre- and Postnatal Growth Retardation in Mice Mol. Cell. Biol., January 15, 2008; 28(2): 743 - 751. [Abstract] [Full Text] [PDF]

				A. Marchini, B. Hacker, T. Marttila, V. Hesse, J. Emons, B. Weiss, M. Karperien, and G. Rappold BNP is a transcriptional target of the short stature homeobox gene SHOX Hum. Mol. Genet., December 15, 2007; 16(24): 3081 - 3087. [Abstract] [Full Text] [PDF]

				R. M. Leach Jr. and E. Monsonego-Ornan Tibial Dyschondroplasia 40 Years Later Poult. Sci., October 1, 2007; 86(10): 2053 - 2058. [Abstract] [Full Text] [PDF]

				K. E. Govoni, S. K. Lee, Y.-S. Chung, R. R. Behringer, J. E. Wergedal, D. J. Baylink, and S. Mohan Disruption of insulin-like growth factor-I expression in type II{alpha}I collagen-expressing cells reduces bone length and width in mice Physiol Genomics, August 20, 2007; 30(3): 354 - 362. [Abstract] [Full Text] [PDF]

				E A Parker, A Hegde, M Buckley, K M Barnes, J Baron, and O Nilsson Spatial and temporal regulation of GH-IGF-related gene expression in growth plate cartilage J. Endocrinol., July 1, 2007; 194(1): 31 - 40. [Abstract] [Full Text] [PDF]

				J. Baron Growth Hormone Therapy in Childhood: Titration Versus Weight-Based Dosing? J. Clin. Endocrinol. Metab., July 1, 2007; 92(7): 2436 - 2438. [Full Text] [PDF]

				C. J. Xian Roles of Epidermal Growth Factor Family in the Regulation of Postnatal Somatic Growth Endocr. Rev., May 1, 2007; 28(3): 284 - 296. [Abstract] [Full Text] [PDF]

				T. C. R. Prickett, G. K. Barrell, M. Wellby, T. G. Yandle, A. M. Richards, and E. A. Espiner Response of plasma CNP forms to acute anabolic and catabolic interventions in growing lambs Am J Physiol Endocrinol Metab, May 1, 2007; 292(5): E1395 - E1400. [Abstract] [Full Text] [PDF]

				S. Ciarmatori, D. Kiepe, A. Haarmann, U. Huegel, and B. Tonshoff Signaling mechanisms leading to regulation of proliferation and differentiation of the mesenchymal chondrogenic cell line RCJ3.1C5.18 in response to IGF-I J. Mol. Endocrinol., April 1, 2007; 38(4): 493 - 508. [Abstract] [Full Text] [PDF]

				S. Kurtoglu, T. Gunes, E. Koklu, O. Bastug, O. Canoz, M. Kula, F. Bastug, and I. Gunes Influence of Maternal Nicotine Exposure on Neonatal Rat Bone: Protective Effect of Pentoxifylline Experimental Biology and Medicine, March 1, 2007; 232(3): 398 - 405. [Abstract] [Full Text] [PDF]

				E. Bonnelye, R. A. Zirngibl, P. Jurdic, and J. E. Aubin The Orphan Nuclear Estrogen Receptor-Related Receptor-{alpha} Regulates Cartilage Formation in Vitro: Implication of Sox9 Endocrinology, March 1, 2007; 148(3): 1195 - 1205. [Abstract] [Full Text] [PDF]

				K. Frazier, R. Thomas, M. Scicchitano, R. Mirabile, R. Boyce, D. Zimmerman, E. Grygielko, J. Nold, A.-C. DeGouville, S. Huet, et al. Inhibition of ALK5 Signaling Induces Physeal Dysplasia in Rats Toxicol Pathol, February 1, 2007; 35(2): 284 - 295. [Abstract] [Full Text] [PDF]

				J. H. Tobias, C. D. Steer, C. Vilarino-Guell, and M. A. Brown Estrogen Receptor {alpha} Regulates Area-Adjusted Bone Mineral Content in Late Pubertal Girls J. Clin. Endocrinol. Metab., February 1, 2007; 92(2): 641 - 647. [Abstract] [Full Text] [PDF]

				J. O. Sanders Maturity Indicators in Spinal Deformity J. Bone Joint Surg. Am., February 1, 2007; 89(suppl_1): 14 - 20. [Full Text] [PDF]

				J. J. Dibner, J. D. Richards, M. L. Kitchell, and M. A. Quiroz Metabolic Challenges and Early Bone Development J. Appl. Poult. Res., January 1, 2007; 16(1): 126 - 137. [Abstract] [Full Text] [PDF]

				R. Chung, J. C. Cool, M. A. Scherer, B. K. Foster, and C. J. Xian Roles of neutrophil-mediated inflammatory response in the bony repair of injured growth plate cartilage in young rats J. Leukoc. Biol., December 1, 2006; 80(6): 1272 - 1280. [Abstract] [Full Text] [PDF]

				S. A. Kontulainen, H. M. Macdonald, and H. A. McKay Change in Cortical Bone Density and Its Distribution Differs between Boys and Girls during Puberty J. Clin. Endocrinol. Metab., July 1, 2006; 91(7): 2555 - 2561. [Abstract] [Full Text] [PDF]

				J. Hoogendam, E. Parlevliet, R. Miclea, C. W. G. M. Lowik, J. M. Wit, and M. Karperien Novel Early Target Genes of Parathyroid Hormone-Related Peptide in Chondrocytes Endocrinology, June 1, 2006; 147(6): 3141 - 3152. [Abstract] [Full Text] [PDF]

				G. Radetti, G. D'Addato, D. Gatti, M. Bozzola, and S. Adami Influence of two different GH dosage regimens on final height, bone geometry and bone strength in GH-deficient children. Eur. J. Endocrinol., March 1, 2006; 154(3): 479 - 482. [Abstract] [Full Text] [PDF]

				A S Chagin, D Chrysis, M Takigawa, E M Ritzen, and L Savendahl Locally produced estrogen promotes fetal rat metatarsal bone growth; an effect mediated through increased chondrocyte proliferation and decreased apoptosis J. Endocrinol., February 1, 2006; 188(2): 193 - 203. [Abstract] [Full Text] [PDF]

				G. Binder, F. Baur, R. Schweizer, and M. B. Ranke The d3-Growth Hormone (GH) Receptor Polymorphism Is Associated with Increased Responsiveness to GH in Turner Syndrome and Short Small-for-Gestational-Age Children J. Clin. Endocrinol. Metab., February 1, 2006; 91(2): 659 - 664. [Abstract] [Full Text] [PDF]

				D. Kiepe, S. Ciarmatori, A. Haarmann, and B. Tonshoff Differential expression of IGF system components in proliferating vs. differentiating growth plate chondrocytes: the functional role of IGFBP-5 Am J Physiol Endocrinol Metab, February 1, 2006; 290(2): E363 - E371. [Abstract] [Full Text] [PDF]

				P. J. O'Shea, J. H. D. Bassett, S. Sriskantharajah, H. Ying, S.-y. Cheng, and G. R. Williams Contrasting Skeletal Phenotypes in Mice with an Identical Mutation Targeted to Thyroid Hormone Receptor {alpha}1 or {beta} Mol. Endocrinol., December 1, 2005; 19(12): 3045 - 3059. [Abstract] [Full Text] [PDF]

				A.-M. Cleton-Jansen, H. M. van Beerendonk, H. J. Baelde, J. V.G.M. Bovee, M. Karperien, and P. C.W. Hogendoorn Estrogen Signaling Is Active in Cartilaginous Tumors: Implications for Antiestrogen Therapy as Treatment Option of Metastasized or Irresectable Chondrosarcoma Clin. Cancer Res., November 15, 2005; 11(22): 8028 - 8035. [Abstract] [Full Text] [PDF]

				L. Rodriguez, Z. Cheng, T.-H. Chen, C. Tu, and W. Chang Extracellular Calcium and Parathyroid Hormone-Related Peptide Signaling Modulate the Pace of Growth Plate Chondrocyte Differentiation Endocrinology, November 1, 2005; 146(11): 4597 - 4608. [Abstract] [Full Text] [PDF]

				T. Rhen and J. A. Cidlowski Antiinflammatory action of glucocorticoids--new mechanisms for old drugs. N. Engl. J. Med., October 20, 2005; 353(16): 1711 - 1723. [Full Text] [PDF]

				A. Kato, M. Suzuki, Y. Karasawa, T. Sugimoto, and K. Doi PTHrP and PTH/PTHrP Receptor 1 Expression in Odontogenic Cells of Normal and HHM Model Rat Incisors Toxicol Pathol, June 1, 2005; 33(4): 456 - 464. [Abstract] [Full Text] [PDF]

				A. Woods, G. Wang, and F. Beier RhoA/ROCK Signaling Regulates Sox9 Expression and Actin Organization during Chondrogenesis J. Biol. Chem., March 25, 2005; 280(12): 11626 - 11634. [Abstract] [Full Text] [PDF]

				M. Alba, A. V. Schally, and R. Salvatori Partial Reversibility of Growth Hormone (GH) Deficiency in the GH-Releasing Hormone (GHRH) Knockout Mouse by Postnatal Treatment with a GHRH Analog Endocrinology, March 1, 2005; 146(3): 1506 - 1513. [Abstract] [Full Text] [PDF]

				V. Parikka, Z. Peng, T. Hentunen, J. Risteli, T. Elo, H K. Vaananen, and P. Harkonen Estrogen responsiveness of bone formation in vitro and altered bone phenotype in aged estrogen receptor-{alpha}-deficient male and female mice Eur. J. Endocrinol., February 1, 2005; 152(2): 301 - 314. [Abstract] [Full Text] [PDF]

				C. Phornphutkul, K.-Y. Wu, X. Yang, Q. Chen, and P. A Gruppuso Insulin-like growth factor-I signaling is modified during chondrocyte differentiation J. Endocrinol., December 1, 2004; 183(3): 477 - 486. [Abstract] [Full Text] [PDF]

This Article Abstract Full Text (PDF) Alert me when this article is cited Alert me if a correction is posted Citation Map Services Email this article to a friend Similar articles in this journal Similar articles in PubMed Alert me to new issues of the journal Download to citation manager Request Copyright Permission Citing Articles Citing Articles via HighWire Citing Articles via Google Scholar Google Scholar Articles by van der Eerden, B. C. J. Articles by Wit, J. M. Search for Related Content PubMed PubMed Citation Articles by van der Eerden, B. C. J. Articles by Wit, J. M.