Enhancement of primate oocyte maturation and fertilization in vitro by inhibin A and activin A

Objective: A role for inhibin and activin in primate oocyte maturation was investigated. Design: The maturation and fertilization of rhesus monkey oocytes recovered from the excised ovaries of nine regularly cycling animals was compared for untreated germinal vesicle (GV)intact controls versus oocytes cultured in the presence of inhibin, activin, inhibin + activin, or in a combination with follistatin. Setting: Nonhuman primates in a research institute environment. Interventions: Bilateral oophorectomy. Main Outcome Measure: Oocyte maturation from germinal vesicle breakdown (GVBD) to metaphase II (MII) and fertilization. Results: Germinal vesicle breakdown, progression to MII and fertilization was monitored in oocytes cultured for 48 hours. Activin alone, at an optimum concentration of 100 ng/mL, stimulated GVBD whereas both GVBD and MII development was enhanced in the presence of inhibin activin. The latter also accelerated the rate of maturation to MII. All treatment groups exhibited a higher incidence of GVBD compared with controls. When follistatin was added, the stimulatory effect of activin or activin + inhibin was abolished. Exposure to medium containing inhibin + activin significantly increased the percentage of MII oocytes that fertilized compared with controls (68% versus 25%, respectively). Conclusions: Inhibin and activin are potent stimulators of primate oocyte maturation, producing mature oocytes in vitro that fertilize with high efficiency.