Effect Of Folate Deficiency On Promoter Methylation And Gene Expression Of Esr1, Cdh1and Pgr, And Its Influence On Endometrial Receptivity And Embryo Implantation

Background: Folate, one of the B vitamins, provides the one-carbonunits required for methylation. Folate deficiency has been reported for theassociation with many pathologies. However, much less is known about theeffect of it on human reproduction, especially on implantation.Establishment of uterine receptivity is crucial for successful embryoimplantation. Gene expression can be influenced by both heredity andepigenetics such as DNA methylation. However, it is not known whether themethylation and expression of genes related to uterine receptivity can beaffected by folate levels. To explore whether folate deficiency affected theepigenetic regulation of genes related to uterine receptivity, and theirinfluence on implantation, we investigated the methylation and expressionof Cdh1, Pgr and Esr1during implantation and the implantation efficiency using a folate-deficient pregnant mouse model.Methods: A folate-deficient pregnant mouse model was established inthis study. Plasma folate levels of pregnant mice were detected using theelectro-chemiluminescence immunoassay. The methylation status of Cdh1,Pgr and Esr1promoter region was determined by methylation specific PCRand bisulfite sequencing. The expression of Cdh1, Pgr and Esr1in theimplantation-site endometrium was examined by real-time PCR, westernblot and immunohistochemistry. The number and the morphology ofpinopodes, important morphologic marker of endometrial receptivity, wereexamined using scanning-electron microscopy. The number of implantationsites on day5of pregnancy demarcated by distinct blue bands was recordedalso.Results: Here it showed that methylation status of Esr1wassignificantly decreased, while the methylation status of Cdh1and Pgr werenot varied in folate-deficient mice compared with wild type. The geneexpression of Esr1were significantly decreased, and Cdh1and Pgrexpression levels were slightly elevated in folate-deficient mice. Neither thenumber nor morphology of pinopodes was affected by folate deficiency.Furthermore, folate deficiency did not affect the number of implantationsites in mice.Conclusions: This study demonstrates for the first time that althoughthe methylation and expression of Esr1is significantly altered at the folate-deficient status, folate deficiency is not able to influence themethylation and expression of Pgr and Cdh1, two genes shown to beessential for uterine receptivity, and embryo can implant into endometriumnormally. The differential regulation of Esr1, Cdh1and Pgr methylationduring tumorigenesis and endometrium receptivity may be a new aspect forstudying the mechanisms of "uncontrolled" tumor invasion and "controlled"embryo implantation. It is a clue for further possibility of the effect of folateon pregnancy process after implantation, although embryo implantation isnormal at the deficiency of folate. Background: As is well known, uterine decidualization andplacentation is the basement of embryo development after embryoimplantation. It is believed that decidualization is much important for theprovision of nutrition to the developing embryo until the placenta has beendeveloped. The abnormal decidualization could not lead fetal get propernourishmen and develop normally. Studies have suggested that folate has aimportant role in the placentation. However, much less is known about theeffect of it on uterine decidualization. In this research, our aim is to study onthe possible roles of folate deficiency in the regulation of decidualization bycells apoptosis after embryo implantation.Methods: A folate-deficient pregnant mouse model was established inthis study and the fetus birth rate was analyzed. The morphologicalcharacteristics of uterine on day7was detected by HE staining. Theexpression of Hoxa10and MMP2in endometrium on day7and day8were examined by real-time PCR, western-blot and immunohistochemistry. Themouse uterine stromal cells on day7were isolated and purified forapoptosis by flow cytometry and the protein expression of Bax and Bcl2were examined using western-blot.Results: By mating normal or folate deficient females with normalmales, we found that the fetus birth rate (0,0/20) of folate deficient groupwas significantly decreased than that (90%,18/20) in control. The embryosin folate deficiency on day7were in different degrees of absorption. Theresults by HE staining showed the decidual morphology was affected byfolate deficiency. In folate-deficient mice, the gene expression of Hoxa10and MMP2were significantly decreased. Apoptosis of decidual tissues infolate deficiency was obviously decreased, and the Bax protein expressionwas significantly decreased while Bcl2was significantly elevated.Conclusions: This study demonstrates for the first time that expressionof Hoxa10and MMP2, two genes shown to be important fordecidualization, are significantly altered at the folate-deficient status, andthe expression of Bax and Bcl2, which play essential roles for apoptosis indecidualization, are also significantly altered in folate deficiency. Itsuggestes that folate may be essential for decidualization.