Uterine peristalsis plays a vital role in fertility and female reproductive health. Although uterine peristalsis is thought to be correlated with some hormones and uterine pathologies, the physiological mechanisms underlying uterine peristalsis remain not quite clear. This study aimed to identify changes in miRNA in the endometrium of patients with abnormally high-frequency (hyper-) and low-frequency (hypo-) peristalsis to clarify whether miRNAs regulate uterine peristalsis. We used a miRNA microarray and RT-qPCR to identify changes in miRNA in endometrial tissue, a collagen gel contraction assay on co-cultured human endometrial stromal cells (ESCs) to analyze how the altered regulation of miRNAs influences uterine smooth muscle (USM) contraction, Western blots and other assays to elucidate the potential mechanisms involved. We found that among several differentially regulated miRNAs, miR-29c-3p was overexpressed in endometrial samples from patients with hypoperistalsis; oxytocin receptor (OXTR) expression was low in endometrial samples from patients with hypoperistalsis. Bioinformatic analysis and luciferase assays indicated that OXTR is a target of miR-29c-3p, which attenuates its expression. Additionally, downregulation of miR-29c-3p in ESC cultures increased the expression of aldo-keto reductase family 1, member C3 (AKR1C3) and increased the release of prostaglandin F2 alpha (PGF2α). Co-cultured ESCs overexpressing miR-29c-3p reduced USM cell contractions; the opposite tendency was found when ESCs were transfected with a miR-29c-3p inhibitor. To conclude, miR-29c-3p in endometrial cells regulates uterine contractility by attenuating the expression of OXTR and reducing PGF2α release.
Supplemental Fig. 1 Laser scanning confocal microscopy was used to analyze calcium ion flux in USMs following OXTR knockdown. The fluorescence increase after adding oxytocin was smaller in the si-OXTR group than it was in the control group. Relative fluorescence increase rate= fluorescence intensity- fluorescence intenstity baseline/ fluorescence intenstity baseline (the intensity before adding oxytocin).