| The process of mammalian pregnancy involves many links,such as embryo implantation,decidualization,embryo development,delivery and so on.Among them,embryo implantation and decidualization are the keys to the success of pregnancy.The failure of embryo implantation and decidualization will directly lead to the failure or termination of pregnancy.In mouse uterus,the establishment of a series of events,such as embryo implantation and decidualization,decidualization of uterine stromal cells,as well as the maintaining of further development of embryos are induced synergistically by estrogen and progesterone.X box binding protein 1(XBP1)is an important member of the transcription factor CREB/TRF family.As a key protein in the IRE1α/XBP1 s pathway,XBP1 plays an important role in the unfolded protein response(UPR),thereby alleviating endoplasmic reticulum stress.UPR has a broad physiological role in the reproductive process of female mammals,such as embryo implantation,decidualization,preimplantation embryo development,follicular atresia and placental development.As a key regulator in UPR,XBP1 is essential for mammalian pregnancy,as well as growth and development.Studies show that complete loss of XBP1 results in embryo death.There is evidence that XBP1 may be involved in embryo implantation and decidual processes.But during early pregnancy of mice,XBP1 expression patterns in the uterus,whether it is regulated by hormones,as well as its influence and regulation mechanism on events such as embryo implantation,decidua and embryonic development have not been reportedIn this study,we established the early pregnancy model,delayed implantation and activation model,artificial induced decidualization model,estrus cycle model of mice,as well as a hormone regulation model of ovariectomized mice.And we detected the expression of XBP1 m RNA and protein in these models by the methods of immunohistochemistry(IHC)and quantitative RT-PCR.Furthermore,in order to further study the effects of XBP1 on embryo implantation and decidualization of mice,the Ltf-i Cre tool mice were used to be specifically knocked out the Xbp1 genes of uterine epithelium and glands,so that it cannot express XBP1 protein.In order to identify the reproduction of Xbp1-c KO,female fertility was assessed by mating Xbp1-c KO and control females with wild-type males continuously for 2 months and counted the numbers of litters and pups produced by each female.The success rate of pregnancy was analyzed by counting the female mice with successful delivery after normal mating(vaginal suppository positive).The uteruses of adult Xbp1-c KO mice were taken for HE,IHC,quantitative RT-PCR and Western Blotting to observe and analysis whether the structure of uterine and cell proliferation and apoptosis in knockout mice were abnormal.The uterine implantation sites of GD5.5 mice were detected by HE staining and statistical analysis and the effect of XBP1 on embryo implantation and decidua were further analyzed.The conclusions are as follows:(1)The expression of XBP1 in mouse uterus during early pregnancy showed dynamic changes.The XBP1 protein was mainly detected in the luminal and glandular epithelia on days 1-4 of pregnancy,and was strongly detected in the decidual area on days 5-8 of pregnancy.Similarly,XBP1 expression was also mainly expressed in decidual cells following artificial decidualization.During the oestrous cycle,Xbp1,Xbp1 u,and Xbp1 s m RNA was predominantly present in prooestrus.In the ovariectomized uterus,the expression of XBP1 in luminal and glandular epithelia was up-regulated after estrogen treatment.(2)Xbp1-c KO female fertility decreased,pregnancy success rate,litter size and litter size decreased significantly.(3)Xbp1-c KO female uterus structure intact but the number of glands decreased significantly,the percentage of proliferative cells decreased significantly.(4)The uterine structure of female mice Xbp1-c KO 13 weeks of age was intact but the number of glands decreased significantly,the percentage of proliferative cells of uterine stromal cells decreased,and the implantation of embryos in Xbp1-c KO mice was abnormal.To sum up,XBP1 is closely related to mouse embryonic implantation and decidualization,and its expression in uterine and glandular epithelium of early pregnancy is regulated by estrogen. |
