Fig. 6

The Saga of integrins: The implantation cascade. Depicted is a generalized summary of the attachment cascade for implantation in humans in which the conceptus is hypothesized to roll across the uterine surface until it is slowed and tethered to the uterine luminal epithelium (LE) first via interactions with mucins, followed by carbohydrate-lectin binding, and completed when firm adhesion is mediated through integrins binding to ECM bridging ligands, in a manner similar to the extravasation of leukocytes from the vasculature [39, 40]. Similar cascades are postulated for pigs, sheep and mice; however, the conceptuses of pigs and sheep likely do not roll across the uterine surface. Instead, the trophoblast cells proliferate and migrate across the uterine surface as the conceptuses undergo elongation [41, 42]