Growth and antrum formation of bovine preantral follicles in long-term culture in vitro

Culture of preantral follicles has important biotechnological implications through its potential to produce large quantities of oocytes for embryo production and transfer. A long-term culture system for bovine preantral follicles is described. Bovine prean-tral follicles (166 6 2.15 mm), surrounded by theca cells, were isolated from ovarian cortical slices. Follicles were cultured un-der conditions known to maintain granulosa cell viability in vi-tro. The effects of epidermal growth factor (EGF), insulin-like growth factor (IGF)-I, FSH, and coculture with bovine granulosa cells on preantral follicle growth were analyzed. Follicle and oocyte diameter increased significantly (P, 0.05) with time in culture. FSH, IGF-I, and EGF stimulated (P, 0.05) follicle growth rate but had no effect on oocyte growth. Coculture with granulosa cells inhibited FSH/IGF-I-stimulated growth. Most fol