Endometriosis-associated infertility dysregulates miRNAs in follicular fluid extracellular vesicles compromising follicular cells dialog and impairing oocyte quality
Background: Endometriosis is a multifactorial disease affecting around 10% of women worldwide and strongly associated to infertility. However, the impact of endometriosis-associated infertility on the follicular microenvironment and oocyte quality is poorly understood. Extracellular vesicles (EVs), lipid bilayer nanoparticles with diverse molecular cargo (such as miRNAs), have emerged as key mediators of the intercellular communication among granulosa cells, cumulus cells (CCs), and the oocyte in the ovarian follicle. These cellular dialogs through follicular fluid EVs (FFEVs) are essential to support egg developmental competence, fertilization potential, and its capacity to form a viable embryo. So far, it has not been explored if endometriosis affects FFEVs and their cargo. Therefore, the study aimed: 1) to determine whether endometriosis patients (E) have different FFEV miRNA cargo compared to patients without the disease (considering disease stage and oocyte fertilization status); and 2) if so, to examine whether the dysregulated FFEV miRNAs are common to those altered in CCs from a previous study, leading both the compromised oocyte quality associated to endometriosis; and 3) to unveil if the altered FFEV miRNAs can be the drivers of reported alterations in granulosa cells (GCs), CCs or oocytes, thereby disrupting the follicular cells dialog and indirectly impairing oocyte quality.Basic procedure: FF samples obtained from single follicles from patients undergoing ART were used (E: n=19 and without the disease C: n=19). FF samples were retrospectively classified into patients with 2PN oocytes (n=12) and patients with 0PN oocytes (n=7). The FFEVs were isolated from one single follicle, to be able to associate it to the oocyte in that follicle and the miRNAs analyzed by RNA-seq.Main findings: RNA-seq identified a total of 173 miRNAs with considerable expression in FFEVs, with 23 found as differentially abundant (DA) in E vs. C (FDR 10%). In E patients, 3 miRNAs were identified as DA in mild E versus severe E, while no significant differences were found for 2PN versus 0PN oocytes. Comparison of miRNAs identified in FFEVs (173) and CCs (189), revealed an overlap of 123 miRNAs. Among the 23 DA miRNAs in FFEV in E vs. C, 17 were also found in CC (with 8 also DA in CCs) and 6 DA exclusively in FFEVs. The 8 DA miRNAs in FFEV and CCs target genes altered by E disease in oocytes and related to: progesterone-mediated oocyte maturation, oocyte meiosis, embryo development, response to oxidative stress, protein targeting to mitochondrion, and autophagy of mitochondrion.Conclusions. Dysregulated miRNAs in FFEVs identified for the first time in endometriosis-associated infertility patients, are also altered in CCs surrounding the oocyte. This indicates an altered follicular microenvironment in E patients, that could impair the follicular cells dialog and oocyte quality, and thus, the identified miRNAs are potential biomarkers and therapeutic targets.