The modern view of ovarian folliculogenesis recognizes the potential regulatory impact of endocrine, paracrine, and autocrine factors on this process. Recent interest has focused upon the roles of intraovarian growth factors in the regulation of follicle cell proliferation and differentiation. Of particular interest is transforming growth factor-beta (TGF-B) by nature of its multifunctional role with respect to cell proliferation and differentiation. It is hypothesized that TGF-B of theca cell origin regulates follicle development in the pig by regulation of granulosa and theca cell proliferation and differentiation. Theca cell TGF-B expression is in turn regulated by endocrine factors and intraovarian growth factors. This project will focus upon testing this hypothesis by analyzing the regulation of TGF-B production in porcine theca cells at four distinct levels: (A) secretion and (B) activation using a highly sensitive bioassay; (C) cellular accumulation using bioassay and by radiolabeled amino acid incorporation and immunoprecipitation; and (D) transcription, by analysis of TGF-B mRNA production using specific cDNA hybridization. With these as endpoints the following questions will be addressed: (1) Do theca cells produce TGF-B and if so what TGF-B subtype? (2) Do luteinizing hormone (LH) and/or follicle-stimulation hormone (FSH) directly regulate TGF-B production by the theca cells and at what level? (3) Do TGF-a/EGF, PDGF, IGF-I, and TGF-B, growth factors which regulate theca and granulosa cell proliferation and differentiation, directly regulate the production of theca cell TGF-B and at what level? (4) Do granulosa cells regulate the production of theca cell TGF-B? (5) Do LH, FSH, TGFa/EGF, PDGF, IGF-I and TGF-B act through granulosa cells to regulate theca cell TGF-B production? The studies outlined above and detailed herein will provide a comprehensive analysis of the regulation of expression and activation of a potent growth factor implicated in the regulation of follicle development. Moreover, they will provide a means with which to test statements with respect to the autocrine and paracrine roles of growth factors in follicle cell function.
