Implantation, trophoblast differentiation and haemochorial placentation: mechanistic evidence in vivo and in vitro.

The process of implantation and placentation in women in volves a series of intercellular interactions, the eventual elucidation of which will result in extensions or even shifts of cell biological paradigms. These include the formation of motile and non-motile mononuclear and multinuclear trophoblast, alterations between faster and slower states of proliferation, changes in adhesive properties and further differentiation of the various trophoblast populations. In addition there is progressive local tissue remodelling by both mononuclear and multinuclear trophoblast as it interacts with the maternal environment (Aplin, 1989; Glasser et al. 1991) including decidua, smooth muscle, endothelium and blood.