Estrous cycle impacts microRNA content in extracellular vesicles that modulate bovine cumulus cell transcripts during in vitro maturation

Purpose: Extracellular vesicles (EVs) are nanoparticles that can be secreted by different cells, including cells found within the ovarian follicle. Currently, EVs are considered an important form of intercellular communication, since they carry biological contents. The goal of this study was to survey the effects of small EVs from follicles at different estrous cycle stage in bovine cumulus cells. Methods: We used an established model to obtain follicular fluid (FF) at early and late estrous cycle stage according to corpus luteum appearance, corresponding to low and high progesterone (P4) levels, respectively. We collected FF from 3-6 mm follicles and isolated small EVs, which were used as a supplement during in vitro maturation (IVM). Cumulus cells were collected from cumulus-oocyte complexes (COCs) pools and the RNAs were obtained and subjected to RNA sequencing. Results: The results showed that small EVs from different estrous cycle stage are capable to affect transcripts in cumulus cells and modulate different pathways and biological processes related to oocyte maturation, ovulation and immune response. Conclusion: This study demonstrated that small EVs from low and high P4 group impact the RNA profile in cumulus cells after 9 hours of in vitro maturation. Cumulus-oocyte complexes (COCs; n=20) were maintained in maturation media without small EVs (EVs free FCS) or with small EVs from low or high P4 follicles for 9 hours. Six replicates of IVM were performed. Cumulus cells from 2 replicates were pooled to form 3 pools of which supplementation group, which were used for RNA sequencing.