Extracellular vesicles derived from antral follicles significantly change the transcriptional profile of cumulus cells and oocytes during pre-in vitro maturation in cattle
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 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 p53 signaling and Cholesterol metabolism. Despite these changes, no significant effects of the EV treatment were noted on Overall design: In the present experiment, COCs were subjected to pre-IVM in the absence (control) or presence of EVs from the follicular fluid of either early (7.0-8.5 mm) or late (= 12.0 mm) follicles. Afterwards, COCs were used for i) analysis of chromatin remodeling and meiotic progression; ii) IVP encompassing IVM, IVF and IVC; iii) isolation of cumulus cells and oocytes at the end of pre-IVM for analysis of the transcriptional profile by RNA sequencing (RNA-Seq). F