Adhesion molecules in human trophoblast - a review. II. extravillous trophoblast.

At the tips of anchoring villi, cytotrophoblast (CTB) proliferation leads to a process of multilayering in which cells lose their attachment to the villous basement membrane and develop into columns, within which they adhere to one another using desmosomes, with associated intermediate filament bundles. Non-desmosomal cadherins, tight junction proteins and other adhesion molecules are also present, suggesting that actin-associated adhesions contribute to placental anchorage. In the distal columns, cell-cell interactions diminish, cells upregulate beta1 integrins and bind to a provisional fibrinoid extracellular matrix, eventually detaching to migrate into the decidual stroma and myometrium, where interstitial and endovascular extravillous trophoblast (EVT) populations show distinct repertoires of adhesion molecules.