Sequential Regulatory of In Vitro Meiotic Maturation and Developmental Competence of Oocytes

Mimicking the intrafollicular environment during in vitro matu-ration (IVM) of oocyte may have beneficial effects on devel-opmental competence of oocytes. In follicle structure, oocyte, cumulus cells (CCs), granulosa cells (GCs) and circulating fac-tors act as meiotic inhibitory and regulatory elements toward achieving fully grown oocyte. This study aimed to assess the effects of exogenous granulosa secreted factors on development competence of sheep oocytes. Immature ovine cumulus oocyte complexes (COCs) were cultured in presence of combination of exogenous granulosa secreted factors. Cultured COCs were used for assessment of (1) cumulus expansion; (2) maturation rate (3) expression of cumulus-related transcripts and (4) yield and quality of derived embryos. Ligands and receptors related to granulosa secreted signaling had lower expression in cumu-lus cells derived from small follicles in compare to larger fol-licles. The best meiotic regulatory, gap junction communication and developmental rate achieved by sequential exposure of COCs to exogenous granulosa secreted factors. These results may provide an alternative IVM method to optimize oocyte competency and in vitro embryo production in sheep.