Role of Cumulus Cells and Follicular Fluid on Oocyte Maturation and Developmental Competence of Embryos: Intact and Reconstructed Oocytes

Abstract

Ovarian follicles develop during fetal and postnatal periods through several distinct phases and they release their matured ova upon puberty. Oocytes surrounded by a single layer of pregranulosa follicular cells are called primordial follicles and they remain dormant in the meiotic prophase I stage. Activation of primordial follicles initiate through pregranulosa follicular cells. The primordial follicle takes several months to grow and develop to preovulatory follicles in mammals. Changes occur during follicular growth and development stages on the oocyte and the surrounding cumulus cells to prepare the oocyte for further embryo development upon ovulation and fertilization. Molecules transfer to oocytes through gap junctions of cumulus cells. Therefore, cumulus cells and their secretion, follicular fluid, effect on oocyte maturation and developmental potential of the resulting embryos in vivo and in vitro. Because of the importance of cumulus cells on follicular development, this review was made to collect and consolidate the current knowledge of cumulus cells effects on maturation of intact and reconstructed oocytes and further developmental competence of embryos in vivo and in vitro