Analysis of the proteome of individual equine cumulus complexes after maturation in-vitro and in-vivo

Maturation of oocytes under in-vitro conditions (IVM) results in impaired developmental competence compared to oocytes matured in-vivo. Oocytes are closely coupled to their cumulus complex (COC) with a bidirectional exchange of metabolites. Therefore, elucidation of aberrations in cumulus metabolism in-vitro is crucial for a better mimicking of physiological maturation conditions. The aim of this study was the analysis of the equine cumulus cells proteome of single cumulus complexes of metaphase II oocytes matured either under in-vivo (n=8) or in-vitro (n=7) conditions. For in-vivo COC collection mares were slaughtered 30 hours after injection and cumulus complexes from the dominant follicle were harvested for analysis. For in-vitro maturation COCs were recovered from mares out of oestrous and matured for 30 hours in-vitro. COCs were separated in cumulus complexes and oocytes, and only cumulus of successfully matured oocytes was analyzed for this study. All cumulus samples were washed, snap frozen and stored in liquid nitrogen until preparation for analysis.