Progesterone‐induced miR‐133a inhibits the proliferation of endometrial epithelial cells

Abstract Aim This study aimed to understand the role of miR‐133a in progesterone actions, explore the regulative mechanism of the progesterone receptor, and investigate the effects of miR‐133a on the progesterone‐inhibited proliferation of mouse endometrial epithelial cells. Methods The expression of miR‐133a induced by progesterone was detected by quantitative real‐time PCR both in vivo and in vitro . Ishikawa subcell lines stably transfected with progesterone receptor subtypes were used to determine the receptor mechanism of progesterone inducing miR‐133a. Specific miR‐133a mimics or inhibitors were transfected into mouse uteri and primary cultured endometrial epithelial cells to overexpress or downregulate the miR‐133a. The roles of miR‐133a in the cell cycle and proliferation of endometrial epithelial cells were analysed by flow cytometry and Edu incorporation analysis. The protein levels of cyclinD2 in uterine tissue sections and primary cultured endometrial epithelial cells were determined by immunohistochemistry and Western blot analysis. Results Progesterone could induce miR‐133a expression in a PRB ‐dependent manner in endometrial epithelial cells. miR‐133a inhibited endometrial epithelial cell proliferation by arresting cell cycle at the G 1 ‐S transition. Moreover, miR‐133a acted as an inhibitor in downregulating cyclinD2 in endometrial epithelial cells. Conclusion We showed for the first time that progesterone‐induced miR‐133a inhibited the proliferation of endometrial epithelial cells by downregulating cyclinD2. Our research indicated an important mechanism for progesterone inhibiting the proliferation of endometrial epithelial cells by inducing special mi RNA s to inhibit positive regulatory proteins in the cell cycle.