Expression and Function of Meflin in Human Endometrial Decidualization

Purpose Decidualization of endometrial stromal cells involves significant morphological and functional changes in which alpha‐smooth muscle actin (αSMA) expression decreases. Meflin, a glycosylphosphatidylinositol‐anchored protein, suppresses αSMA expression and inhibits fibrosis in various tissues. Therefore, we investigated whether Meflin regulates decidualization by modulating αSMA expression. Methods Meflin protein expression was evaluated in human endometrial tissues using immunohistochemistry. Immortalized endometrial stromal cells were used for in vitro experiments. The effects of decidualization on Meflin were assessed using 17β‐estradiol, progesterone, and dibutyryl cyclic AMP treatments and analyzed using quantitative polymerase chain reaction, western blotting, and collagen gel contraction assays. The role of Meflin was investigated by performing an overexpression assay. Results Meflin expression was significantly higher in the secretory‐phase endometrium than in the proliferative‐phase endometrium and was inversely correlated with αSMA expression. In vitro decidualization increased Meflin expression while suppressing that of αSMA. Meflin overexpression decreased αSMA expression and contractility, induced morphological changes from spindle‐shaped to polygonal cells, and attenuated IGFBP1 expression, a decidualization marker. Conclusion Meflin functions as a regulator of endometrial decidualization by modulating αSMA expression and cellular contractility. The evaluation of Meflin expression may provide insights into disorders associated with impaired decidualization, such as infertility and endometriosis.