miR-503, a microRNA epigenetically repressed in endometriosis, induces apoptosis and cell-cycle arrest and inhibits cell proliferation, angiogenesis, and contractility of human ovarian endometriotic stromal cells

Is the micro-RNA (miRNA) miR-503, downregulated in endometriotic cyst stromal cells (ECSCs) and does this affect the cell cycle, cell proliferation, angiogenesis and contractility of these cells? miR-503 expression is downregulated in ECSCs by DNA hypermethylation and this contributes to their proliferation, resistance to apoptosis, extracellular matrix (ECM) contractility and angiogenesis through effects on cyclin D1, B-cell lymphoma/leukemia (Bcl)-2, Ras homology A and vascular endothelial growth factor A (VEGF-A). A variety of miRNAs are demonstrated to involve in the pathogenesis of endometriosis. miR-503 is a miRNA with tumor-suppressor functions, whose expression is suppressed in ECSCs. We isolated ECSCs and normal endometrial stromal cells (NESCs) from ovarian endometriotic tissues (n = 32) and eutopic endometrial tissues without endometriosis (n = 8), respectively. We investigated the functions of miR-503 by using miR-503-transfected ECSCs and the DNA methylation status of miR-503 gene in ECSCs and NESCs by combined bisulfite restriction analysis. In ECSCs, miR-503 is downregulated by the DNA hypermethylation of its gene. The transfection of miR-503 into ECSCs resulted in the inhibition of cell proliferation and induction of cell-cycle arrest at G0/G1 phase through the suppression of cyclin D1, the induction of apoptosis through Bcl-2 suppression, the inhibition of VEGF-A production and the attenuation of ECM contractility via the suppression of Rho/Rho-associated coiled-coil-forming protein kinase-pathways. NA. The present experiments were carried out only with the stromal component of endometriosis and eutopic endometrium. The experiments with the eutopic endometrial stromal cells from women with endometriosis are not performed. Our findings indicate that epigenetically repressed miR-503 in ECSCs is involved in the acquisition of endometriosis-specific cellular functions. This work was supported in part by Grants-in-Aid for Scientific Research from the Japan Society for the Promotion of Science (no. 13237327 to K.N., no. 26861335 to K.K. and no. 23592407 to H.N.) and the Kanzawa Medical Research Foundation (to K.K.). There are no conflicts of interest to declare.