The cumulus cells and oocytes: A systematic review of extended culture for intracytoplasmic sperm injection

Currently-placed protocols for extended culture for in vitro fertilization (IVF) and intracytoplasmic sperm injection (ICSI) are not uniformly standardized in determining the optimal stage of oocyte maturation for maximizing clinical outcomes. The objective of this systematic review is to elucidate the relationship between extended cumulus-oocyte culture and its effect on the clinical outcomes of IVF/ICSI. We included an electronic search on PubMed Central as well as the Journal of Fertility and Sterility to yield seven studies on extended oocyte culture for IVF/ICSI. Four of the seven investigations illustrate the promising beneficial relationship of extended culture with conditioned or supplemented media to mimic physiological uterine conditions. Three studies did not capture beneficial relationships between extended oocyte culture and clinical outcomes with unconditioned, unsupplemented maturation medium. Improvement in fertilization rates, oocyte development, and live birth rates may be achieved by extended culture with the addition of supplemental biochemicals. The usage of follicular fluid, cumulus cells, and meiotic inhibitors imitates the physiological in vivo conditions, whereas extended oocyte culture imitates in vivo temporal conditions. The conjunction of extended oocyte culture with supplemented metabolites, either added in maturation media manually or secreted by cumulus-oocyte complexes, mimics natural uterine physiological conditions to improve clinical outcomes for patients seeking IVF/ICSI. Key words: Cumulus Cells; Extended Culture; In vitro Fertilization; Intracytoplasmic Sperm Injection; Oocyte