Investigation of the regulation of FoxO1 expression through HBEGF and akt signalization in the process of embryo implantation

EMBRYONIC HBEGF REGULATES FOXO1 THROUGH PI3K/AKT SIGNALIZATION IN THE PROCESS OF REMOVAL OF THE EMBRYO-EPITHELIAL BARRIER Objective: To investigate the relationship of embryonic HBEGF and AKT signaling pathways with FoxO1, which regulates implantation by controlling the mechanism of removal of the epithelial barrier in the endometrial luminal epithelium during embryo implantation in the mouse. Method: Expression of HBEGF, AKT, p-AKT, and FoxO1 were evaluated by immunofluorescence labeling in the process of removal of the epithelial barrier in normal pregnancy, which includes D4 night (23:00), D5 morning (09:00), D5 night (23:00), D6 morning (09:00) groups, and in mouse endometrium where beads coated with HBEGF and as well as inhibit AKT signaling were transferred. Results: During implantation, endometrial lumen closure occurs with the activation of PI3K signaling. Embryonic HBEGF initiates PI3K signaling in the endometrial epithelium, thereby activating AKT. As a result, in the luminal epithelium that the embryo encounters, FoxO1 is transported to the cytoplasm, apoptosis is prevented in the epithelium, and instead, the embryo crosses the epithelial barrier by entosis. Thereafter HBEGF, which migrates to the nucleus, initiates its own transcriptional inhibition, thus causing nuclear FoxO1 accumulation and apoptosis in the closed luminal epithelium. Conclusion: In this study, the roles of HBEGF, AKT, p-AKT, and FoxO1 signaling in the embryonal crossing of the epithelial barrier were revealed. Currently, 40-50% of the causes of recurrent pregnancy loss are stated as unexplained causes. Considering these, the failure of the embryo to cross the epithelial barrier may be related to the causes of unexplained pregnancy losses in humans. On the other hand, AKT, p-AKT, and FoxO1 molecules seem to be important for a healthy pregnancy as well as a healthy endometrial homeostasis. For this reason, the results of our study have formed a basis for new projects in the context of developing therapeutic target molecules for endometrial diseases as well. Key words: FoxO1, HBEGF, crypt epithelium, implantation, endometrium