Cumulus cell determinants of oocytes developmental competence

A third of women undergoing oncological treatment is at risk of premature ovarian failure. In vitro maturation of denuded fullygrown antral oocytes (DOs) to metaphase II in the presence of cumulus cells (CCs) and their further cryopreservation is a strategy for preserving women fertility.1,2 Attempts have been made to culture DOs upon a feeder layer of CCs (FL-CCs) with meager results.3-5 The purpose of this study was to test whether a selection of CCs prior to the preparation of the FL improves the quality of oocytes maturation. We classified CCs based on their association with developmentally competent (SN) or incompetent (NSN) mouse fully-grown antral oocytes and prepared a FL-SNCCs or FL-NSN-CCs, respectively. We show that maturation of DOs upon FL-SN-CCs significantly better contributes to the acquisition of oocytes meiotic and developmental competence, with a developmental rate to blastocyst equal to that obtained after the maturation of intact cumulus oocyte complexes. Instead, DOs matured in the absence of CCs (NO-FL) or upon FL-NSN-CCs undergo meiotic and developmental failure, with embryos arresting either at the 4-cell or morula stage. Our experiments suggest the presence of a crucial developmental CC-factor/s released in the presence of FL-SN-CCs during oocyte maturation. These results set the bases to unravel the molecules involved in the cross-talk between the gamete and its companion cumulus cells during the GV-to-MII transition and to further improve the protocols of antral oocytes maturation in animal studies and human clinical applications.