Effect of interactions between granulosa and thecal cells on meiotic arrest in bovine oocytes.

An in vitro culture system in which two types of cell from ovarian follicular walls were attached to opposite surfaces of a collagen membrane was developed. The effect of granulosa-theca cell communication on oocyte maturation was investigated using this culture system. Bovine cumulus-oocyte complexes were incubated with granulosa cells, with or without theca cells. The time course of germinal vesicle breakdown was assessed. When cultured with granulosa cells alone, oocytes showed 100% germinal vesicle breakdown after incubation for 6 h. However, when cultured with granulosa and theca cells, germinal vesicle breakdown was significantly delayed for up to 12 h. Breakdown was further delayed by 12 h when cumulus-oocyte complexes were incubated with FSH-treated granulosa and thecal cultures. FSH did not exert this inhibitory effect when in culture with granulosa cells alone. When cumulus-oocyte complexes were incubated with thecal cells alone, all oocytes underwent germinal vesicle breakdown within 6 h; the addition of FSH to the culture medium did not affect the time course of breakdown. It is concluded that a signal(s) from thecal cells augments the meiosis-arresting activity of granulosa cells and that FSH increases the meiosis-arresting activity of granulosa cells under the influence of thecal cells.