Nuclear maturation and structural components of nonhuman primate cumulus–oocyte complexes during in vivo and in vitro maturation

ObjectiveTo compare cumulus cell structure and timing of oocyte maturation of in vitro–matured (IVM) and in vivo–matured (VVM) nonhuman primate oocytes.DesignIn vivo maturation and in vitro maturation of oocytes.SettingAnimal cell culture laboratory.Animal(s)Forty-eight female rhesus macaques.Intervention(s)Fifteen animals were administered FSH, and aspirated oocytes were cultured in vitro for 0, 3, 6, 12, or 24 hours (IVM). Thirty-three animals were administered FSH and hCG, and oocytes were collected 3, 6, 12, or 28–30 hours after hCG (VVM).Main Outcome Measure(s)Nuclear maturation and microtubule scores of oocytes and actin and tubulin transzonal processes of cumulus cells. Embryo development was observed for VVM oocytes.Result(s)The rate of nuclear maturation was faster for IVM oocytes compared with VVM oocytes. Actin transzonal processes decreased 0–12 hours after hCG administration for VVM oocytes. Tubulin transzonal processes of IVM and VVM oocytes decreased from 0 to 24 hours and from 0 to 3 hours, respectively. Embryo development improved as VVM time increased.Conclusion(s)Nuclear maturation and remodeling of cumulus–oocyte complex structural components associated with in vitro maturation do not parallel those of oocyte maturation in vivo, indicating that in vitro culture conditions continue to be suboptimal.