The Functional Role of Cumulus Cells and Their Influence on Oocyte Quality: A Systematic Review.

A systematic review was conducted pertaining to the biologic processes of cumulus cells and measures of oocyte quality. The initial search yielded 18,549 articles, and after screening, 65 studies were included in this review. Extracted data were synthesized descriptively. Articles were categorized based on the biologic feature of cumulus cells addressed: genetic expression, biochemical activity, and morphologic characteristics. Manuscripts addressing cumulus cell function in association with gynecologic conditions and their impact on oocyte quality were also reviewed. Findings from six studies showed an association between increased expression of pathways related to extracellular matrix development (HAS2, VCAN) and improved oocyte quality. Six manuscripts reported improved oocyte quality related to genes involved in cumulus cell expansion (GREM1, PTGS2) and 6 articles noted patterns in expression of regulators of apoptotic pathways (BCL2, BIRC5, MDM2, PGAM5). Twelve studies examined biochemical features of cumulus cells, including cumulus mitochondrial membrane resistance, respirometric index, and acetyl-CoA levels, which have been associated with oocyte development. Morphologic assessment of cumulus cells was evaluated by 5 studies, demonstrating a relationship between mitochondrial dimensions, telomere length, and cumulus density/dispersion with oocyte quality. Twenty-two articles assessed cumulus cell function and its relationship with oocyte quality in diseases such as polycystic ovarian syndrome (PCOS) and endometriosis conditions, and increased maternal age (with or without decreased ovarian reserve). This comprehensive systematic review has integrated findings from studies investigating the relationship between cumulus cells and oocyte quality, identifying patterns in gene expression, biochemical features and morphologic assessments that may offer meaningful insight into this relationship.