Evaluation of the expressions of FOXO1, FOXO3 and FOXO4 transcription factors in mouse endometrium during peri-implantation period

Objective: In parallel with pre-implantation embryo development, the formation of receptive endometrium is one of the most critical steps in development and continuation of pregnancy. The aim of this study was to investigate whether FoxO transcription factors that have important roles in cell cycle, DNA repair, apoptosis and cellular metabolism are expressed in mouse uterus during peri-implantation period, if so, whether their expressions are related pregnancy hormones and the presence of the embryo. Method: In this study; using 6-8 weeks old BALB/C female mice, estrous phase and days 1–8 of pregnancy mouse uteri sections were obtained. Immunohistochemistry was performed for the evaluation of FoxO1, FoxO3 and FoxO4 proteins. In addition, pseudopregnancy and induced-decidualization for artificial decidualization models were performed. The expressions of all FoxOs in all groups were evaluated with H-score analysis and statistical analysis was performed. Results FoxO proteins were expressed differentially with nuclear and/or cytoplasmic expressions during pregnancy. Interestingly, nuclear expression of FoxO1 in endometrial epithelium and glands on pregnancy day 5 when uterus receptive for implantation, FoxO3 and FoxO4 expressions were present in primer and secondary decidualization regions on days 6–8 of pregnancy respectively. When expressions of these proteins in pseudopregnancy and artificial decidualization models were evaluated, we found that their expressions seem to be related to steroid hormones. Besides, FoxO1 and FoxO3 expressions seems to be presence of the embryo Whereas FoxO4 expression seems to be related to presence of the embryo. Conclusion: Our findings indicate that FoxO transcription factors are differentially expressed troughout early pregnancy and they may have important roles in mouse embryo implantation, uterus receptivity and decidualization processes. Key words: mouse, endometrium, FoxO, implantation, peri-implantation