Stage-dependent role of growth differentiation factor-9 in ovarian follicle development.

GDF-9 was shown to be essential for follicle progression and is the only factor secreted by the oocyte shown to increase the number of primordial and primary follicles in vivo. Furthermore, GDF-9 is a major growth factor involved in the oocyte control of granulosa cell differentiation. A concentration gradient of the paracrine factor GDF-9 established by the oocyte could provide the basis to explain the stratification of granulosa cells in antral and preovulatory follicles. The stimulatory effects of GDF-9 on early follicle development provide a basis for the use of GDF-9 in the treatment of infertility.