Abstract
1,25-Dihydroxyvitamin D3 (1,25(OH)2D3) and transforming growth factor-β (TGF-β) are both important regulators of chondrocyte growth and differentiation. We report here that 1,25(OH)2D3 differentially regulates the expression of the genes for TGF-β1 to -β3 and the secretion of the corresponding proteins in cultured chick chondrocytes. Confluent growth plate chondrocytes were serum-deprived and cultured in varying concentrations of 1,25(OH)2D3. Cells were assayed for TGF-β mRNA and conditioned medium was assayed for TGF-β activity and isoform composition. Active TGF-β was only detected in 10−8m 1,25(OH)2D3-treated cultures (8·37 ng active TGF-β/mg protein). There was a significant decrease in total (latent+active) TGF-β activity in conditioned medium of 10−12 m (23·4%; P<0·05) and 10−10 m (20·7%; P<0·05) 1,25(OH)2D3-treated cultures but 10−8 m 1,25(OH)2D3 significantly increased (30·9%; P<0·01) TGF-β activity. The amounts of TGF-β1, -β2 and -β3 isoforms produced were similar in control, 10−10 or 10−12m 1,25(OH)2D3-treated cultures but the conditioned medium of 10−8 m 1,25(OH)2D3-treated cultures contained significantly higher amounts of all three isoforms. Quantification of TGF-β mRNA demonstrated differential control of TGF-β gene expression with TGF-β1 and -β3 mRNA levels reduced by all concentrations of 1,25(OH)2D3 examined (10−8, 10−10 and 10−12 m) whilst TGF-β2 mRNA concentrations were elevated. Our results indicated that 1,25(OH)2D3 regulates chick growth plate chondrocyte TGF-β secretion and mRNA expression in a concentration-dependent and isoform-specific manner. This interaction may be important in the regulation of chondrocyte metabolism and endochondral bone growth.
Journal of Endocrinology (1996) 149, 277–285
Temporal and spatial expression of connective tissue growth factor (CCN2; CTGF) and transforming growth factor beta type 1 (TGF-beta1) at the utero-placental interface during early pregnancy in the pig