Pregnancy achieved by transferring blastocysts into endometrial stroma in mice

Abstract

To prevent the extra-uterine discharge of transferred embryos, we directly inserted mouse embryos into the endometrial stroma (intra-endometrial embryo transfer). A 27G injection needle was inserted near the utero-tubal junction into the endometrial stroma. After removal of the needle, a glass micropipette was inserted and one embryo was transferred with a very small amount of culture medium. To determine the feasibility of this method, the uterine lumen was flushed with phosphate-buffered saline from the tubal ends immediately after transferring blastocysts into pseudopregnant mice on day 2 and day 4. The rates of recovery of embryos from the uterine lumen were 5.0% (1/20; day 4) and 15.0% (3/20; day 2). These results suggest that a high rate of intra-endometrial embryo transfer is possible. The embryonic viability rates (number of viable grown fetuses/number of blastocysts transferred) of this method were 50.0% (28/56; day 4) and 25.0% (5/20; day 2). Living offspring were delivered from both recipients which had received embryos on day 2 and day 4 of pseudopregnancy. In human in-vitro fertilization and embryo transfer, attempts have also been made to immobilize the embryos, and this method might be clinically applicable. Moreover, this method will be a good in-vivo model for studies on the mechanism of implantation.

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Assisted Implantation: Direct Intraendometrial Embryo Transfer

“…It is also not known whether an embryo transferred under luminal epi thelium is able to develop normally and whether it is pos sible to increase pregnancy rate by assisted implantation. In the mouse, pregnancies were achieved by transferring blastocysts into the endometrial stroma [6], By using this technique it was possible to increase pregnancy and em bryonic viability rates in asynchronous embryo transfer in the mouse [7], Implantation of human embryos involves integrated series of processes including adhesion to the endometrial mucosa and invasion of the blastocyst through the lumi nal epithelium into the endometrial stroma [8]. Bulletti et al [9] injected human blastocysts into the endometrium of human ex vivo perfused uteri and demonstrated that blastocysts can successfully undergo implantation and trophoblastic invasion during 52 h of extracorporeal per fusion.…”