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.