Vaginal extracellular vesicles impair fertility in endometriosis by favoring Th17/Treg imbalance and inhibiting sperm activity.

ABSTRACT

Extracellular vesicles (EVs) play a key role in various diseases. However, their effect on endometriosis (EMs)-associated infertility is poorly understood. We co-cultured EVs from the female vaginal secretions with human sperm and also generated a mouse model of EMs by allogenic transplant to explore the effect of EVs on fertility. EVs from individuals with EMs-associated infertility (E-EVs) significantly inhibited the total motility (26.46% vs. 47.1%), progressive motility (18.78% vs. 41.06%), linear velocity (21.98 vs. 41.91 µm/s) and the acrosome reaction (AR) rate (5% vs. 22.3%) of human sperm in contrast to the control group (PBS). Furthermore, E-EVs dose-dependently decreased the intracellular Ca2+ ([Ca2+]i), a pivotal regulator of sperm function. Conversely, healthy women (H-EVs) increased human sperm motion parameters, the AR rate, and sperm [Ca2+]i. Importantly, the mouse model of EMs confirmed that E-EVs further decreased the conception rate and the mean number of embryo implantations (7.6 ± 3.06 vs. 4.5 ± 3.21) compared with the control mice by inducing the production of inflammatory cytokines leading to a Th17/Treg imbalance. H-EVs could restore impaired fertility by restoring the Th17/Treg balance. We determined the impact of EVs derived from the female genital tract on human sperm function and studied the possible mechanisms by which it affects fertility. Our findings provide a novel rationale to ameliorate EMs-associated infertility.