Transforming growth factor-? signaling participates in the maintenance of the primordial follicle pool in the mouse ovary.

ABSTRACT: Physiologically, only a few primordial follicles are activated to enter the growing follicle pool each wave. Recent studies in knock-out mice show that early follicular activation depends on signaling from the tuberous sclerosis complex, the mammalian target of rapamycin complex 1 (mTORC1), phosphatase and tensin homolog deleted on chromosome 10, and phosphatidylinositol 3-kinase (PI3K) pathways. However, the manner in which these pathways are normally regulated, and whether or not TGF-? acts on them are poorly understood. So, this study aims to identify whether or not TGF-? acts on the process. Ovary organ culture experiments showed that the culture of 18.5 days post-coitus (dpc) ovaries with TGF-?1 reduced the total population of oocytes and activated follicles, accelerated oocyte growth was observed in ovaries treated with TGF-?R1 inhibitor 2-(5-chloro-2-fluorophenyl)pteridin-4-yl]pyridin-4-yl-amine (SD208) compared with control ovaries, the down-regulation of TGF-?R1 gene expression also activated early primordial follicle oocyte growth. We further showed that there was dramatically more proliferation of granulosa cells in SD208-treated ovaries and less proliferation in TGF-?1-treated ovaries. Western blot and morphological analyses indicated that TGF-? signaling manipulated primordial follicle growth through tuberous sclerosis complex/mTORC1 signaling in oocytes, and the mTORC1-specific inhibitor rapamycin could partially reverse the stimulated effect of SD208 on the oocyte growth and decreased the numbers of growing follicles. In conclusion, our results suggest that TGF-? signaling plays an important physiological role in the maintenance of the dormant pool of primordial follicles, which functions through activation of p70 S6 kinase 1 (S6K1)/ribosomal protein S6 (rpS6) signaling in mouse ovaries.

SUBMITTER: Wang ZP 

PROVIDER: S-EPMC3961657 | biostudies-literature | 2014 Mar

REPOSITORIES: biostudies-literature