[Stromal cell-derived miR-423-5p targets EMP2 to promote M2 macrophage polarization and directly enhance stromal cell migration in endometriosis]

OBJECTIVES: M2 macrophages enriched in endometriotic lesions are involved in immune evasion and angiogenesis, while the migratory capacity of ectopic endometrial stromal cells is also closely associated with lesion progression. However, whether these two processes are regulated by a common upstream molecule remains unclear. This study aims to investigate whether endometrial stromal cell-derived miR-423-5p promotes M2 macrophage polarization by targeting epithelial membrane protein 2 (EMP2) and directly enhances the migratory capacity of stromal cells themselves, thereby synergistically contributing to the progression of endometriosis (EMs). METHODS: The EMs-related dataset GSE7305 was downloaded from the Gene Expression Omnibus (GEO) database. The dataset included ectopic endometrial tissues from 9 patients with EMs and endometrial tissues from 7 women without EMs, and the infiltration of 22 immune cell types was evaluated and compared. Ectopic and eutopic endometrial tissues were collected from 10 patients with EMs, respectively. The expression levels of miR-423-5p, EMP2, and the M2 markers CD206 and IL-10 were examined by immunohistochemical staining, reverse transcription PCR (RT-PCR), and Western blotting. A dual-luciferase reporter assay was performed to verify the direct binding of miR-423-5p to the 3'- untranslated region (3'-UTR) of EMP2. THP-1 cells were induced to differentiate into M2 macrophages in vitro and were transfected with miR-423-5p mimics, mimic negative control (NC), miR-423-5p inhibitor, or inhibitor NC. Meanwhile, primary human endometrial stromal cells (phESCs) were isolated and cultured, transfected, and subsequently co-cultured with M2 macrophages. The expression levels of miR-423-5p, EMP2, CD206, and IL-10 were assessed by RT-PCR and Western blotting. A wound-healing assay was used to assess the migratory capacity of endometrial stromal cells. RESULTS: Bioinformatics analysis showed that the proportion of M2 macrophages was significantly higher in ectopic endometrial tissues than in normal endometrial tissues (P<0.05). Immunohistochemical staining, RT-PCR, and Western blotting consistently showed that the expression levels of the M2 markers CD206 and IL-10 were significantly higher in ectopic endometrial tissues from patients with EMs than in their eutopic endometrial tissues, whereas EMP2 expression was significantly lower in ectopic than in eutopic endometrium (all P<0.05). RT-PCR showed that miR-423-5p expression was significantly higher in phESCs derived from ectopic endometrium than in those derived from eutopic endometrium (P<0.05). The dual-luciferase reporter assay demonstrated that miR-423-5p directly bound to the 3'-UTR of EMP2 and suppressed its activity (P<0.05). Overexpression of miR-423-5p in M2 macrophages significantly upregulated CD206 and IL-10 expression and downregulated EMP2 expression (all P<0.05), whereas inhibition of miR-423-5p produced the opposite effects. Co-culture experiments further demonstrated that stromal cells overexpressing miR-423-5p promoted M2 macrophage polarization and downregulated EMP2 expression in the co-culture system (all P<0.05). The wound-healing assay showed that upregulation of miR-423-5p significantly enhanced the migratory capacity of endometrial stromal cells (P<0.05). CONCLUSIONS: Endometrial stromal cells may promote M2 macrophage polarization by secreting miR-423-5p and thereby targeting and downregulating EMP2 expression in M2 macrophages, while simultaneously enhancing their own migratory capacity. Together, these effects may contribute to remodeling of the immune microenvironment and progression of EMs.