1,25(OH) 2 D 3 and Dihydrotestosterone Interact to Regulate Proliferation and Differentiation of Epiphyseal Chondrocytes

Abstract

Growth plate chondrocytes are affected by 1,25(OH)2D3 and androgens, which may critically interact to regulate proliferation and differentiation during the male pubertal growth spurt. We investigated possible interactions of 1,25(OH)2D3 and the non-aromatizable androgen dihydrotestosterone (DHT) in primary chondrocyte cultures from young male rats. DHT and 1,25(OH)2D3 independently stimulated DNA synthesis and cell proliferation in a dose-dependent manner with maximally effective doses of [10(-8) M] and [10(-12) M], respectively. Both DHT and 1,25(OH)2D3 stimulated the expression and release of IGF-I, and the proliferative effects of each hormone were prevented by an IGF-I antibody. DHT and 1,25(OH)2D3 increased messenger RNAs (mRNAs) of their cognate receptors and of IGF-I receptor mRNA (IGF-I-R). 1,25(OH)2D3 also stimulated mRNA of the androgen receptor (AR), whereas DHT did not affect mRNA of the vitamin-D receptor (VDR). Coincubation with both steroid hormones did not stimulate receptor mRNAs more than either hormone alone. The proliferative effects of DHT and 1,25(OH)2D3 were completely inhibited by simultaneous incubation with both hormones, despite potentiation of IGF-I synthesis. In contrast, both hormones synergistically stimulated cell differentiation as judged by alkaline phosphatase activity, collagen X mRNA, and matrix calcification in long-term experiments. We conclude that DHT and 1,25(OH)2D3 interact with respect to chondrocyte proliferation and cell differentiation. The proliferative effects of both hormones are mediated by local IGF-I synthesis. Simultaneous coincubation with both hormones blunts the proliferative effect exerted by either hormone alone, in favor of a more marked stimulation of cell differentiation.

Differential expression of IGF system components in proliferating vs. differentiating growth plate chondrocytes: the functional role of IGFBP-5

“…Cells were cultured in monolayers (Nunc, Wiesbaden, Germany), as described previously, from our laboratory (4,19). Briefly, the F-12-DMEM (1:1) medium, which contained a nominal calcium concentration of 1.2 mM, was supplemented with 10 mM HEPES, 100 g/ml streptomycin, and 10% FCS.…”

Androgen and Estrogen Treatment, Alone or in Combination, Differentially Influences Bone Maturation and Hypothalamic Mechanisms that Time Puberty in the Male Rhesus Monkey (Macaca mulatta)

“…In this regard, DHT has been shown to stimulate DNA synthesis and cell proliferation in epiphyseal rat chondrocyte in primary culture (50), indicating a growth-promoting effect of this steroid on epiphyseal cartilage. A role of AR in the pubertal growth spurt is also supported by the present finding that DHT was equivalent in its effects on linear growth and other somatic growth indices to both E 2 and T. Therefore, unlike the case for BA, where E 2 may be the singular steroid responsible for pubertal bone maturation, both ER and AR probably play important roles in supporting the pubertal linear growth spurt.…”

Endocrine Regulation of the Growth Plate

“…Similarly, testosterone, and to a lesser extent, dihydrotestosterone stimulates chondrocyte proliferation in the mouse mandibular condyle, an organ culture model of endochondral ossification [71]. These local effects may be mediated, in part, by increased local IGF-I expression [70, 71]. …”

“…Local administration of testosterone reportedly increases unilateral rat tibial epiphyseal growth plate width [69]. Furthermore, in vitro, dihydrotestosterone can stimulate proliferation and proteoglycan synthesis in growth plate chondrocytes [70]. Similarly, testosterone, and to a lesser extent, dihydrotestosterone stimulates chondrocyte proliferation in the mouse mandibular condyle, an organ culture model of endochondral ossification [71].…”