Review: in vitro models for the study of early human embryo-endometrium interactions.

The molecular interactions at the embryo-endometrial interface during the period of blastocyst adhesion and subsequent invasion into the endometrial stroma are not fully understood. Current knowledge is primarily based on evidence from implantation studies in the mouse. The degree to which data derived from animal studies mirror human implantation is limited. The ethical and technical challenges studying implantation in the human can partly be overcome by designing in vitro models of embryo-endometrium interactions. In this review, the principal models in current use are described. Basic models using tissue explants and monolayers are distinguished from complex models using multilayer isolated cells, and embryo-endometrium coculture systems used therapeutically. Although there are limitations to current approaches, a number of research questions that could be addressed using these techniques are identified.