Embryo effects in human implantation: embryonic regulation of endometrial molecules in human implantation.

Embryonic implantation requires coordinated development of the blastocyst and the maternal endometrium. Considerable advances have been made in the understanding of the cell biology of human embryo and maternal endometrium as separate entities. Nevertheless, communication between them and their reciprocal effects on each other constitute an exciting and as-yet unsolved problem in reproductive medicine. Cross-talk among the embryo, endometrium, and the corpus luteum are known to occur in ruminants and primates; more specifically, endometrial-embryonic interactions have been reported in rodents and primates. Here, we present updated information in humans on the embryonic regulation of endometrial epithelial molecules such as chemokines, adhesion molecules, antiadhesion molecules, and leptin during the apposition and adhesion phases of human implantation. Also the embryonic induction of apoptosis in endometrial epithelial cells as a mechanism for crossing the epithelial barrier will be described.