The Effect of Vitamin D on Expression of TGF beta 1 in Ovary

The transforming growth factor beta (TGF-beta) is thought to have important roles in several stages of folliculogenesis. Vitamin D is effective in cell proliferation, differentiation and on estrogen biosynthesis. The aim of the present study was to determine the respective role of 1,25-dihydroxy-vitamin D3 on expression of TGF-beta 1 in developing rat ovaries. 24 (one-month-old n = 12 and adult n = 12) female Wistar rats were enrolled in this study. All animals were divided into 4 groups. Group I and II that consist of one-month-old (n = 6) and adult rats (n = 6) respectively served as control groups. Intramuscular vitamin D3 (0.05 mu g/kg/every other day) was injected for 8 weeks to group III and IV which consist of one-month-old and adult rats respectively. After last injection, ovaries of animals were removed and processed for immunohistochemistry assay. No remarkable differences in staining intensity and localization for TGF-beta 1 were observed in group I and group III. TGF immunostaining was also predominantly found in oocytes. In granulosa cells, TGF-beta 1 immunoreactivity was negative. TGF-beta 1 immunostaining were observed both in nuclei and cytoplasm of granulosa cells in group II. But in group IV granulosa cells and oocytes were negative for TGF-beta 1. We found that vitamin D administration resulted in a decrease in TGF-beta 1 levels in the adult rats, but, TGF-beta 1 expression did not significantly decrease in the newborn rats. However, in multiple linear regression analysis, TGF-beta 1 expressions were independently associated with vitamin D administration. It is observed that Vitamin D attenuated TGF-beta 1 expression. The results of this study suggest that vitamin D may play role in folliculogenesis via TGF-beta 1