Ectopic endometrial stromal cell-derived extracellular vesicles encapsulating microRNA-25-3p induce endometrial collagen I deposition impairing decidualization in endometriosis.

Endometrial collagen I undergoes dynamic degradation and remodelling in response to endometrial stromal cell (ESC) decidualization and embryo implantation. However, excessive collagen I deposition in the endometrium during the implantation window may impair decidualization, causing embryo implantation failure in patients with endometriosis (EMS). We found that endometrial collagen I expression during the mid-secretory phase was increased in the EMS group of patients. Collagen I stimulation resulted in decreased expression of the decidualization markers prolactin and insulin-like growth factor binding protein-1 in ESCs, impeding ESC transformation to a decidual morphology and decreasing the blastocyst-like spheroid expansion area in vitro. Treatment with extracellular vesicles (EVs) derived from the ectopic ESCs of EMS patients (EMS-EVs) increased collagen I expression in vivo and in vitro and decreased the blastocyst-like spheroid expansion area. Furthermore, EV microRNA (miRNA) sequencing revealed that there were 40 upregulated and 77 downregulated miRNAs in EMS-EVs when compared to the EVs derived from ESCs in the endometrium of control patients (CTL-EVs), including increased expression of miR-25-3p that targets phosphatase and tensin homolog (PTEN). We also found that PTEN expression was decreased and p-Akt expression was increased in the endometrium of EMS patients and EMS-EV-treated ESCs. miR-25-3p transfected ESCs exhibited increased collagen I, decreased PTEN, and increased p-Akt. Additionally, an EV uptake study further showed that EMS-EVs were preferentially taken up by ESCs rather than by endometrial epithelial cells. These results suggest that EMS-EVs encapsulating miR-25-3p might be preferentially taken up by eutopic ESCs where they may induce endometrial collagen I deposition to impair ESC decidualization in EMS.