Regulation of human trophoblast surrogate Jeg-3 spheroids implantation potential by Wnt/β-catenin pathway and lin28a/let-7a axis.

Successful implantation happens only when the development of a competent blastocyst synchronized with the differentiation of a receptive uterus. The exact mechanism affecting embryo implantation competency is still unclear. Previous data from our laboratory showed that several members of the let-7 family were up-regulated in the implanting dormant blastocysts and prohibited embryo activation through down-regulation integrin-β3. However, how the mir-let-7 family is regulated is still a question. In this study, the in vitro co-culture model was applied to imitate implantation. Human embryo surrogate Jeg-3 spheroids and endometrium epithelial cells Ishikawa were used. The following views were demonstrated. Firstly，Wnt/β-catenin signaling is essential for Jeg-3 spheroids implantation. Secondly, mir-let-7a is repressed by Wnt signaling, and low let-7a is beneficial for spheroids attachment and outgrowth. Third, in contrast with let-7a, lin28a is up-regulated by Wnt and promotes attachment and outgrowth. Lastly, the function of Wnt in embryo surrogate spheroids in implantation is mediated through lin28a/let-7a axis. In summary, our findings suggest Wnt/β-catenin signaling strength human embryo surrogate spheroids implanting potential through regulation lin28a/let-7a axis.