The Influence Of Multiparity On Uterine Immunocytes In Early Pregnancy Of Mice

Embryo implantation is an interactive process between an active embryo and receptive uterus.It is significant for an embryo to have a normal development to be blastocyst and uterus to differentiate to receptive state in the successful implantation.In rodents and human beings,physical process between the top of uterine lumen epithelium and hatched blastocyst of trophoblast is a marker of initiation of implantation,followed by apposition and adhesion,and then trophoblast invades the uterine lumen epithelium.Both in these two species,decidualization,or the uterine stromal cells differentiate into transient specific secreted decidual tissue,contributes to the complete the implantation.This course is accompanied by vasculogenesis and recruitment of immunocytes to decidua tissue.Various cytokines or inflammatory factors secreted by immunocytes also involve in embryo implantation and decidualization.The maternal-fetal interface constituting of maternal decidual tissue and placental trophoblast is the basis of immune privilege.Balance of immune response contributes to maintenance of a successful gestation.Decidual cells,as an inherent cell type in maternal-fetal interface,modulates the local immune balance within uterus by interacting with other cell types,including bone marrow-derived immune cells,endothelial cells and invading extravillous trophoblast cells.Maternal immune tolerance to semi-heterologous fetus is the guarantee of normal development and growth for blastocyst in uterine during early pregnancy.It raises immune memory to have multiple births.However,it is still unclear that the position as well as variance of these immune cells and inflammatory factors both in the uteruses of multiparity and primiparity during implantation and decidualization.This study aims to explore the location and variance of uterine immune cells and related molecules during early pregnancy through multiparous mouse model.We set a multiparity group with mice that had undergone delivered 3 times and a primiparity group consists of peer virgin females.After mating with sexually mature male mice,the uteruses on the 4th(D4),5th(D5),and 8th(D8)days of pregnancy were collected for experimental use.Immunohistochemistry and in situ hybridization were used to detect the expression and distribution of five kinds of immune cells within uterus,as well as markers of receptive state and decidualization.The results showed that uterine natural killer cells were less expressed in D5 uterus,while highly expressed in the uterine stroma near mesometrium in D8 uterus.Regulatory T cells were nearly expressed in D8 uterus.Distribution of Treg in D4 and D5 uterus was around endometrial glands.Mast cells showing a purple signal were abundant in the myometrium and outer membrane of D4,D5,and D8 uteruses.So were Dendritic cells.Macrophages were expressed within stroma of D4 uterine,stroma which was near outer membrane of D5 uterine,and myometrium and outer membrane of D8 uterine.ImageJ was used to count signals of immune cells.The statistics demonstrated that only was the number of uterine natural killer cells in the multiparity group less than that in the primary production group,but the difference was not significant.There were a great deal of macrophages in D4 and D5 uterines while it decreased in quantity of D8 uterine.The number of macrophages didn't change significantly between multiparity group and primiparity group.In terms of regulatory T cells,uterine mast cells and dendritic cells in the uterus,the quantity increased because of multiparity.Especially,the quantity variation of mast cells was the most significant.Embryos were not transferred into uterine lumen until D4 of gestation,and the uterus differentiated into receptive state to complete the implantation.The level of Msx1,ER?,PR in D4 uterine representing uterine receptive state was down-regulated by multiparity;the level of Bmp2,Cox2,and Hand2 in D5 uterine that were markers of decidualization were also decreased in multiparity group,compared to primiparity group.The results indicated that multiparity is beneficial to implantation and decidualization.