Role of Oocyte-derived Factors in Ovarian Follicular Development and Ovulation

Coordination of extra- and intrafollicular signals is required for the development of ovarian follicles and for the production of functional oocytes. Oocytes play an active role in this coordination. Oocytes produce two families of growth factors: members of the transforming growth factor beta (TGF β) superfamily, including bone morphogenetic protein (BMP) 6, BMP15, and growth differentiation factor 9 (GDF9); and members of fibroblast growth factors (FGFs), including FGF8. These oocyte-derived paracrine factors, in coordination with the other intrafollicular signals, regulate the development and function of oocyteassociated cumulus cells. In this review, we first summarize the role of oocytes in follicular development and ovulation, focusing on the effects of oocyte-derived paracrine factors on the development and function of cumulus cells. In addition, we summarize recent findings on the coordination of oocyte-derived signals with other intrafollicular signals, such as estrogen and epidermal growth factor (EGF) receptor signals, in cumulus cell development and function, and discuss the potential mechanisms driving this coordination.