A comparative study of attachment of human, bovine and mouse blastocysts to uterine epithelial monolayer.

The in-vitro attachment of human, bovine and murine blastocysts to monolayer cultures of uterine epithelium were studied by transmission electron microscopy. The human trophoblastic cells intrude between uterine epithelial cells forming a multilayer during attachment in vitro, thus resembling the intrusive type of penetration observed in vivo. The bovine trophoblastic outgrowth resembled an epitheliochorial attachment as the trophoblast formed an attachment plate on top of the endometrial cells without penetration. In the murine attachment study, the trophoblast cells immediately displaced the uterine cells and formed contact with the culture vessel.