267. A role for transforming growth factor-β1 (TGF-β1) during the establishment of folliculogenesis

Abstract

A group of structurally related proteins, known as the transforming growth factor-β (TGF- β) superfamily, have been implicated in the local regulation of ovarian function. It is unclear what role TGF-β1–3 plays in folliculogenesis during the period after birth in the rat. We investigated whether the TGF-β ligands and their receptors were present during this period of development and the effects of TGF-β1 on granulosa cell function (proliferation, apoptosis, steroidogenesis). Ovaries from rats 4, 8 and 12 days of age were isolated and RNA extracted and reverse transcribed for real-time PCR. The expression of the TGF-β ligands and TGFβRI and TGFβRII were measured. Granulosa cells isolated from DES treated immature rats were treated with FSH (100ng/mL) and TGF-β1 (1 or 10ng/mL) for 2hr, n = 4 replicates. The RNA was extracted and prepared for RT–PCR. The expression of cyclin D2, FKHR, SCC, 3βHSD and StAR were measured. TGFβRI and TGFβRII proteins were localised to postnatal rat ovary by immunohistochemistry. TGF-β1–3, TGFβRI and TGFβRII were present in rat ovaries as early as 4 days after birth. Expression of TGF-β1 mRNA increased 2-fold between day 4 and 12. TGF-β2 and TGF-β3 mRNAs declined between day 4 and 8 and remained low at day 12. The type I and II TGF-β receptors were differentially regulated with TGFβRI expression high at day 4, declining at day 8. In contrast, TGFβRII appeared to be ubiquitously expressed. Cyclin D2 mRNA expression was enhanced in the presence of both TGF-β1 and FSH, whereas FKHR mRNA expression declined. TGF-β1 had no impact on the steroidogenic mRNAs. TGFβRI and TGFβRII proteins were localised to the cytoplasm of oocytes, granulosa cells and theca cells. These studies indicate that TGF-β1 can exert effects on ovarian folliculogenesis as it is established during the postnatal period. Proliferation and apoptosis appear to be targets of TGF-β1 action.

Supported by the NHMRC of Australia (Regkeys 241000, 198705, 441101 & 465415)