Extracellular Vesicles Derived From Antral Follicles Significantly Change the Transcriptional Profile of Cumulus Cells and Oocytes During Pre‐In Vitro Maturation in Cattle

Abstract

Cumulus-oocyte complexes (COCs) used for in vitro production (IVP) of bovine embryos originate from antral follicles of different sizes, leading to variations in developmental competence. To address this, pre-in vitro maturation (pre-IVM) allows oocytes with additional time to acquire developmental competence. Given the role of follicular fluid-derived extracellular vesicles (EVs) in ovarian follicle communication, which has been shown to vary in content and function across folliculogenesis, we investigated whether EVs from early versus late antral follicles influence COCs during pre-IVM. EV supplementation significantly altered gene expression in cumulus cells and oocytes. In cumulus cells, affected pathways included MAPK signaling, Gap junctions, Cytokine-cytokine receptor interaction, Axon guidance, cAMP, and Cushing syndrome. In oocytes, fewer genes were altered, with effects on Inositol phosphate metabolism, p53 signaling and Cholesterol metabolism. Despite these changes, no significant effects of the EV treatment were noted on oocyte chromatin configuration and developmental competence, except for a significant increase of mitochondrial membrane potential (Δψm) in blastocysts. In conclusion, EV supplementation during pre-IVM significantly altered the transcriptional profile of COCs, with EVs from early follicles modulating the expression of genes regulating cumulus cell proliferation and gap junctions, while EVs from late follicles impacted pathways associated with meiotic resumption, cumulus cell expansion, and apoptosis. Along with improved Δψm in blastocysts, these results support a positive effect of EVs on bovine COCs, but further research is needed to better characterize the functional consequences, mainly in terms of the effects of early versus late follicle-derived EVs on oocyte developmental potential.