A novel human embryonic stem cell-derived trophoblastic spheroid implantation mocel for the study of early human implanation

Abstract

Assisted reproduction technology offers the infertile couples with successful pregnancy over the past few decades though the pregnancy rate remains low. Failure in implantation remains as the rate-limiting factor. The exact mechanism of implantation failure is still poorly understood and investigations are constrained by ethical issues. The recent developments of informative animal models and novel in vitro human models have shed some lights on this implantation “black box” though choriocarinoma cell lines were used in these models. In this study, we aimed at generating a novel model of human embryonic stem cells (hESC) derived trophoblastic spheroid to mimic the three-dimensional structure of human blastocyst during the early implantation stage. To this end, we have generated hESC-derived trophoblastic spheroids which resembled early implanting human embryo in size and with blastocoel like cavity structure. Those spheroids expressed various trophoblastic markers and secrete βhCG. Interestingly, spheroids that have been differentiated for 3 days were able to attach and invade; while little or no attachment was found on those that have been differentiated for 2 days. The attachment was specific to the endometrial epithelial cells, as little or no attachment was found when they were ocultured with a number of different cell lines. The present modified differentiation protocol provides a novel approach to study trophoblastic cell differentiation, implantation, and trophoblastic invasion into human endometrial cells.