Meiosis activating sterol (MAS) regulate FSH-induced meiotic resumption of cumulus cell-enclosed porcine oocytes via PKC pathway *

Meiosis activating sterol (MAS) have been found to be able to promote oocytes meiotic maturation of small animals in vitro, such as mouse, rat and rabbit. But in large animals, whether MAS play the same function, especially the physiological mechanisms of MAS on oocytes maturation are not clear. To our knowledge, this is the first time to investigate the role and signal pathway of MAS on FSH-induced porcine oocytes meiotic resumption. Porcine cumulus-enclosed oocytes (CEOs) isolated from 3 to 5 mm follicles were cultured in the FSH-medium for 24 h supplemented with 0–50 μM RS21745 or 0–100 μM RS21607 (two specific inhibitors of lanosterol 14α-demethylase that converts lanosterol to FF-MAS), or cultured in FSH-medium with 25 μM RS21745 for 0–24 h firstly, then transferred into a new FSH-medium (the total culture time is 24 h). The results revealed that RS21745 or RS21607 could inhibit FSH-induced porcine CEOs meiotic resumption in a dose and time-dependent manner. Meanwhile, FSH-induced cumulus expansion could also be inhibited dose-dependently by RS21745 or RS21607. Otherwise, AY9944-A-7, an inhibitor of Δ14-reductase which promotes cholesterol accumulation from FF-MAS, had no effect on both denuded oocytes (DOs) cultured for 24 or 44 h and CEOs cultured for 24 h meiotic resumption, but it could promote CEOs meiotic resumption after 44 h culture. In addition, we got that 10−8 to 10−6 M PMA, an activator of PKC pathway, could reverse the inhibiting effect of RS21745 on FSH-induced CEOs meiotic resumption and enhance the rate of germinal vesicle breakdown (GVBD) of CEOs cultured in medium with hypoxanthine (HX). Moreover, 5–10 μM chelerythrine chloride, an inhibitor of PKC, could enhance the inhibitory effect of RS21745 on FSH-induced porcine oocytes resumption of meiosis. All the data of this study support that endogenous FF-MAS takes part in the FSH-induced porcine oocytes meiotic resumption and might play an active role via PKC signal pathway.