Determination of mTOR signal pathway in MMTV-TGF alpha mice ovary at different ages

Transforming growth factor alpha (TGF alpha), a member of the epidermal growth factor (EGF) family, regulates cell proliferation, differentiation, and development, and involves follicular development and viability. In ovaries, TGF alpha is shown localized in granulosa cells (GCs) of primary follicles, theca cells (TCs) of pre-antral, antral and pre-ovulatory follicles. TGF alpha overexpression in mouse mammary tumor virus (MMTV-TGF alpha) transgenic mice causes mammary tumor after 50 weeks. However, follicular development and preservation of the ovarian follicle reserve-mediating follicle stimulating hormone (FSH) response are unknown. Mammalian target of rapamycin (mTOR) is a key regulator for cell proliferation, growth, differentiation, and apoptosis, and important for ovarian folliculogenesis and oocyte maturation. The study aim determines TGF alpha overexpression during folliculogenesis via mTOR signaling pathway in ovaries from 10-, 18-, 50-, and 82-week-old MMTV-TGF alpha mice. Histological analysis was performed, along with western blot for mTOR, p-mTOR, P70S6K, PCNA, and Caspase-3, and quantitative RNA (qRT-PCR) for mTOR and P70S6K. Developing follicles number decreased and atretic follicles number increased with aging in MMTV-TGF alpha mice ovary. Ovaries at 18 and 82 weeks had decreased PCNA and increased Caspase-3 protein expression levels as compared to 10-week ovaries. Protein expression levels of mTOR and p-mTOR decreased gradually from ovaries at 10-18 weeks, increased at 50 weeks and decreased again at 82 weeks. These results indicate that TGF alpha may be one regulator of healthy follicular development and affect mTOR signaling pathway during ovarian aging. Thus, over-expression of TGF alpha might lead to reduced ovarian reserve and premature ovarian insufficiency.