In vivo treatment with GDF-9 stimulates primordial and primary follicle progression and theca cell marker CYP17 in ovaries of immature rats.

Growth differentiation factor (GDF)-9 is a cystine knot-containing hormone of the transforming growth factor-beta superfamily produced by the oocyte. In GDF-9 null mice, follicle development is arrested at the primary stage and GDF-9 treatment in vitro enhances preantral follicle growth. Immature female rats were treated with recombinant GDF-9 for 7 or 10 days. At 10 days, treatment with GDF-9 augmented ovarian weights, concomitant with an increase in the number of primary and small preantral follicles by 30 and 60%, respectively. Furthermore, the number of primordial follicles was decreased by 29%, but the number of large preantral follicles was not affected. In contrast, treatment with FSH increased the number of small and large preantral follicles by 36 and 177% but did not influence the number of primary and primordial follicles. Immunoblot analysis showed an increase of CYP17, a theca cell marker, in the ovarian homogenate after treatment with GDF-9 but not FSH. The present results indicate that in vivo treatment with GDF-9 enhances the progression of primordial and primary follicles into small preantral follicles. Thus, GDF-9 treatment could provide an alternative approach to stimulate early follicle development in addition to the widely used FSH that acts mainly on the development of more advanced follicles.