Cellular and extracellular vesicular origins of miRNAs within the bovine ovarian follicle.

The ovarian follicle components must provide an ideal environment to ensure the success of reproductive processes, and communication between follicular cells is crucial to support proper oocyte growth. Recently, it has been demonstrated that the presence of extracellular vesicles (EVs) carrying microRNAs (miRNAs) in follicular fluid represents an important autocrine and paracrine communication mechanism inside the ovarian follicle. In this study, we tested the hypothesis that the miRNA content of EVs isolated from ovarian follicular (granulosa and cumulus-oocyte complexes) cell-conditioned culture media is dependent upon cell type. We initially screened bovine granulosa cells (GCs) and cumulus-oocyte complexes (COCs), as well as their derived EVs for 348 miRNAs using real-time PCR, and detected 326 miRNAs in GCs and COCs cells and 62 miRNAs in GCs and COCs EVs. A bioinformatics analysis of the identified cell-specific and differentially expressed miRNAs predicted that they likely modulate important cellular processes, including signalling pathways such as the PI3K-Akt, MAPK and Wnt pathways. By investigating the origins of miRNAs within the follicular fluid, the results of this study provide novel insights into follicular miRNA content and intercellular communication that may be of invaluable use in the context of reproductive technologies, diagnostic of ovarian-related diseases and/or the identification of biomarkers for oocyte and embryo quality.