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

Objective: To compare cumulus cell structure and timing of oocyte maturation of in vitro-matured (IVM) and in vivo-matured (VVM) nonhuman primate oocytes. Design: In vivo maturation and in vitro maturation of oocytes. Setting: Animal 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.