Roles Of ICM In Murine Decidualization

The uterus undergoes differentiation of the endometrial stroma into decidual tissue in response to an implanting conceptus.This process,called decidualization,is essential for establishing and maintaining a successful pregnancy.Murine blastocysts include the inner cell mass(ICM)and the trophectoderm(TE).The ICM is the progenitor of the embryo proper as well as of some non-trophoblastic extraembryonic tissues.The TE contributes to the extraembryonic components of the placenta.The paracrine signals from the trophoblast cells of the conceptus can regulate decidualization.If ICM were removed from murine blastocysts by microsurgery,trophoblastic fragment vesicles were proved as effective as intact blastocysts in inducing decidualization in recipient uteri.The proliferation and differentiation of TE were regulated by ICM,and the regulation effect of ICM on trophoblast was maintained until the later period of pregnancy.However,there are a little studies about the roles of ICM tissues and its derivatives in murine decidualization.Based on the documents on TE regulating decidualization and ICM regulating TE,we hypothesize that ICM may play a key role in regulating decidualization.In this study the CD-1 mouse were employed.First,a variety of decidualization were induced by different allogenic materials including tetraploid embryos,air bubbles,zygotes,2-cell embryos,oocytes,trophoblast cells,and glass beads.These allogenic materials were transferred into a single uterine horn of day 3.5 pseudopregnant mice,and decidual tissues were collected four days after stimulation.The differences among different decidual tissues were explored by morphologic observation,tissue section,RNA-sequencing,real-time PCR,and two-dimensional electrophoresis.The results showed that tetraploid embryo-induced deciduoma responses with uniform and obvious nodules were the same as the normal embryo-induced decidua in morphology.The rest of induced deciduoma are non-beaded appearance,crowded around and unevenly distribution along the uterine lumens.Second,dissect and observe decidua tissue under microscope,zygote-induced deciduoma had obvious gaps and was significantly different from 2-cell embryo-induced deciduoma.The decidua induced by normal embryos were intact,and the region of mesometrium were thicker than anti-mesometrium.The conceptuses inside decidua displayed normal embryonic structure.The conceptuses from tetraploid embryo-induced deciduoma completely lost anatomical structure.The blood vessel of mesometrium in deciduoma induced by tetraploid embryo and air bubbles were significantly different from normal embryo-induced decidua.The blood vessel distribution of mesometrium in tetraploid embryo-induced deciduoma were regular,and the blood vessel distribution of mesometrium in air induced-deciduoma were serried.To further explore the potential effect of ICM on decidual tissue gene exprssion during decidualization,the global mRNA levels between RNA samples from 7.5 day tetraploid embryo-induced deciduoma and normal embryo-induced decidua were analysized.There were one hundred and seventy-nine differentially expressed genes between tetraploid embryo-induced deciduoma and normal embryo-induced decidua.One hundred and fifty-one genes were upregulated in embryo-induced decidua compared with the tetraploid embryo-induced deciduoma.Twenty-eight genes were upregulated in tetraploid embryo-induced deciduoma compared with the normal embryo-induced decidua.The differentially expressed genes were closely related trophoblast gaint cell differentiation by GO terms,and the expression of protein were concentrate highly in PRL in decidua with STRING database.The gene expression of Prl4a1,Apoa1,Apoc2,H19,Ttr were upregulated in embryo-induced decidua and downregulated in tetraploid embryo-induced deciduoma.The gene expression of Prl8a2 was the same in embryo-induced decidua and tetraploid embryo-induced deciduoma.In addition,three differential protein points in normal embryo-induced decidua and tetraploid embryo-induced deciduoma were detected by two-dimensional electrophoresis.The results indicated that ICM defect led to abnormal decidualization with abnormal morphology,structure and gene expression,and ICM plays a key role in regulating decidualization.This study provided a new idea for detecting the developmental status of embryo proper and exploring the mechanism of embryo implantation in the future.