Direct positive effect of epidermal growth factor on the cytoplasmic maturation of mouse and human oocytes

Immature mammalian oocytes cultured in vitro undergo inadequate cytoplasmic maturation and hence have a limited potential for fertilization. Our primary objective was to determine if the addition of epidermal growth factor (EGF) to the in vitro culture system would have a positive effect on oocyte cytoplasmic maturation. We studied the effect of different EGF concentrations on both denuded and cumulus-enclosed mouse oocytes cultured in vitro. The percentage of oocytes undergoing germinal vesicle breakdown (GVBD) and polar body one formation over time as a function of EGF concentration was determined. A dose-related positive effect of EGF on both GVBD and polar body one formation over time was observed for mouse oocytes. As well, a similar effect of EGF was seen on immature human oocytes that had not been stimulated with exogenous gonadotropins. The use of EGF may allow for the performance of successful in vitro fertilization procedures using immature human oocytes retrieved during unstimulated cycles.