Effect Of The Relative Position Between Blastocyst Hatching Stie And Inner Cell Mass On The Mouse Embtyo Implantaion And Development

There are about 10% to 15% women of childbearing age in our country suffering from infertile,and one-sixth of the world's couples have fertility problems.Many couples have their babies through Assited Reproductive Technology(ART).Blastocyst selection and embryo transfer are the key steps during the procedure of ART.Two distinct cell types were formed during the blastocyst development in mammals,including inner cell mass(ICM)and trophectoderm(TE).Blastocyst need to be hatched out from the zona pellucida(ZP)before implanting into the uterus.ZP is a layer of glycoprotein that surrounding the mammalian oocytes and pre-implantation embryos.ZP has the function to protect oocyte or embryos.ZP is also able to recognize sperm and prevent polyspermy.Expansion of blastocyst before hatching will make the ZP thinner and produce small holes named hatching site.Embryo will squeeze from ZP through hatching site and move to uterus before implantation and pregnancy.Hatching process is crucial for embryo development.However,researches about this biological procedure is limited.It is still not known if the position of hatching site on the ZP has an effect on embryo development,embryo implantation and offspring health.In this study,we divided blastocysts into three groups according to the angle composed by hatching site and the tagent of ICM arc midpoint,including 0o ? ? ? 30ogroup,30o < ? ? 60ogroup and 60o < ? ? 90ogroup.Nonsurgical embryo transfer(NSET)was used for embryo transfer.Each group of blastocysts were transferred into uterus through the cervix without ahesia and surgery.Implantation rate,pregnancy rate,birth rate and offspring growth curve were calculated.Our data shows that hatching site at different angles does not affect bastocyst implantation rate and the number of implantation sites,but it will affect the birth rate of offspring.Blastocyst at different hatching sites had no effect on the sex ratio,offspring birth weight and the male offspring growth curve,but it affects the growth curve in female pups.Our result could help selecting blastocysts with higher developmental potential in clinical research.