Correlation Between Embryo Incubation Site And Pregnancy And Its Mechanism

Embryo implantation is a complex and continuously dynamic development process regulated by an intimate cross-talk between the activated blastocyst and the receptive uterus,including apposition,adhesion and invasion of blastocyst and placenta formation.Blastocyst hatching is the precondition for the establishment of a mother-embryo relationship.Blastocysts must be hatched from the zona pellucida to enable implantation.Even the embryo with good developmental potential can cause the embryo to be unable to implantation due to the hatching barrier in the blastocyst stage.Currently,assisted hatching technology has been used in clinical practice,but it is not clear whether it will affect the development of implantation and late embryo.In this study,mouse embryos were studied to explore the relationship between embryo hatching sites and pregnancy.By in vitro culture of embryos to hatching,it was found based on ICM that there are five kinds of hatching model respectively for:A site(12 o’clock),B site(1-2 o’clock),C site(3 o’clock),D site(4-5 o’clock)and E site(6 o’clock).By counting the numbers of embryos at different incubation sites(>2000),the results showed that the embryonic hatching rates of B site(44.4%)and C site(38.6%)were significantly higher than those of D site(12.5%)and E site(3.1%)(P<0.05),while A site(1.4%)was lowest.The results showed that the embryo incubation in vitro was site-specific.In order to explore the relationship between the site specificity of hatching and pregnancy,the embryos hatched at different sites were subjected to embryo transfer.The results showed that the birth rate of C site was the highest(55.3%),significantly higher than that of D site(21.3%)and the control group(30.4%)(P<0.05),but not significantly different from B site(40.4%).The B site birth rate was significantly different from the D site,but there was no significant difference from the control group.The results showed specific embryo birth rates at different hatching sites rate.The expression of LIF,LIFR,IL6,IL6R,IL11,IL11R,HB-EGF,MMP2,u-PA,S100A16,CX26,E-cadherin and other gene related to implantation were detected by RT-PCR.The results showed that there were significant differences in LIF,LIFR and u-PA at different sites.Among them,LIF expressed the highest at D site and B site had the lowest expression;LIFR and u-PA expressed the highest at D site and C site had the lowest expression.Immunofluorescence staining was used to detect the protein expression of LIF.LIFR and u-PA at different sites.The results showed that the expression differences of the three proteins in different embryonic hatching sites were not significant.This study found that the natural hatching of normal mouse embryos under in vitro culture is not random,there is specificity of site hatching,and this feature is significantly related to the birth rate,the mechanism still needs further exploration.This discovery can provide a theoretical basis for clinical assisted reproduction and other reproductive technologies.