FOXO1 Expression and Regulation in Endometrial Tissue during the Menstrual Cycle and in Early Pregnancy Decidua

AIMS: To determine FOXO1 (forkhead box O1) expression in the human endometrium during the menstrual cycle and decidua of early pregnancy, as well as FOXO1 regulation in endometrial stromal cells (ESC). METHODS: Immunohistochemistry, RT-qPCR, and Western blot analyses evaluated cellular localization and altered FOXO1 expression in the endometrium during the menstrual cycle and decidua of early pregnancy (proliferative phase, n = 12; early-secretory phase, n = 7; mid-secretory phase, n = 10; late-secretory phase, n = 10; early pregnancy, n = 12). Using RT-qPCR and Western blot, we studied the regulation of FOXO1 by 8-bromo-cAMP, 4-pregnene-3,20-dione, 17β-estradiol, and human chorionic gonadotrophin in ESC (n = 5). RESULTS: The expression level of FOXO1 in human endometrial tissue fluctuated with the menstrual cycle. If pregnancy occurred, the expression of FOXO1 was further increased (p < 0.05) and cAMP regulated FOXO1 expression in ESC. In addition, 4-pregnene-3,20-dione cooperatively stimulated FOXO1 expression with cAMP. We also observed FOXO1 expression during in vitro cAMP-induced decidualization. CONCLUSIONS: The pattern of FOXO1 expression suggests a potential role for FOXO1 in implantation and decidualization.