Corpus luteum proximity alters molecular signature of the small extracellular vesicles and cumulus cells in the bovine ovarian follicle environment

Progesterone (P4) is predicted to act as a negative regulatory hormone for oocyte maturation events; however, its local effects during follicular development remain poorly understood in bovine. The complex process of oocyte meiosis progression is dependent on cellular communication among follicular cells. Besides, the breakdown of this communication, mainly between cumulus cells and oocyte, through the retraction of cumulus projections connecting these cells can impact oocyte maturation. In our study, we observed that ipsilateral follicles containing high intrafollicular P4 concentrations enhance the expression of proteins in follicular small extracellular vesicles predicted to be involved in the retraction of membrane projections based on actin filaments, such transzonal projections (TZPs). Additionally, we found that contralateral follicles containing low intrafollicular P4 concentrations are predicted to regulate cellular communication pathways inducing the maintenance of membrane projections in cumulus cells. Our functional analysis confirmed that supplementation of cumulus-oocyte complexes during in vitro maturation with P4 at concentration similar to ipsilateral follicles reduces the number of TZPs. In summary, our study underscores a direct association between P4 concentration and cumulus-oocyte interaction, with potential consequences for the acquisition of oocyte competence. Following the OPU sessions, the FF from both groups (ipsilateral and contralateral follicles) were placed separately in a 100 mm petri dish, and pools of COCs were retrieved using a stereomicroscope. Four pools were collected per experimental group. Each pool contained samples from 3 different animals.