Improvement of in vitro culture of mouse cumulus–oocyte complexes using PDE3-inhibitor followed by meiosis induction with epiregulin

Abstract

To explore potential helping effects of a PDE3-inhibitor (PDE3-I), Org9935, in long-term culture of cumulus-corona-oocyte complexes (COC) and to associate adequate stimuli for efficient oocyte maturation. Experimental in vitro study on mice. Academic research laboratory. F1 hybrid mice: C57Bl/6j x CBA/ca. The COCs were selectively retrieved from cultured follicles at the early antral stage and subcultured for 4 days in absence or presence of Org9935 (5 nM to 1 microM). Oocyte nuclear maturation; estradiol and progesterone concentrations in conditioned medium. Survival of COCs was dose dependently improved by Org9935. When subculture was done in absence of Org9935; human chorionic gonadotropin (hCG), epiregulin, or hCG + epiregulin induced 0%, 17%, and 21%, respectively, of polar body formation. Concentrations above 50 nM prohibited the reinitiation of meiosis by a hCG + epidermal growth factor stimulus. Epiregulin or hCG + epiregulin induced 63% and 66% polar body rate, respectively, but only after washing out the inhibitor. Acute progesterone production occurs after stimulation with hCG, or hCG + epiregulin, but epiregulin alone induces the lowest response. Presence of PDE3-I in cultured COCs improves survival. Washout of PDE3-I is necessary for meiotic resumption to occur. Epiregulin by itself induces meiotic maturation but is a weak inducer of progesterone production.