100µg of pre-miRNA were complexed with 16µl of in vivo-jetPEI (N/P=8) and injected intraperitoneally into mice with induced endometrosis. Injections were repeated every 2 days for 4 weeks. 10 µg of pre-miRNA were complexed with 1.6µl of in vivo-jetPEI(N/P=8) and injected intratumorally into subcutaneous tumors (ectopic endometrial mesenchymal stem cells) of mice. Injections started 7 days after cell implantation and were performed every 2 days for 3 weeks.

It is believed that endometrial miRNAs contribute to the aetiology of endometriosis in stem cells; however, the mechanisms remain unclear. Here we collected serum samples from patients with or without endometriosis and characterized the miRNA expression profiles of these two groups. MicroRNA-199a-5p (miR-199a-5p) was dramatically down-regulated in patients with endometriosis compared with control patients. In addition, we found that the tumour suppressor gene, SMAD4, could elevate miR-199a-5p expression in ectopic endometrial mesenchymal stem cells. Up-regulation of miR-199a-5p suppressed cell proliferation, motility and angiogenesis of these ectopic stem cells by targeting the 3' untranslated region of VEGFA. Furthermore, we established an animal model of endometriosis and found that miR-199a-5p could decrease the size of endometriotic lesions in vivo. Taken together, this newly identified miR-199a-5p module provides a new avenue to the understanding of the processes of endometriosis development, especially proliferation, motility and angiogenesis, and may facilitate the development of potential therapeutics against endometriosis.