VE-cadherin is a critical molecule for trophoblast-endothelial cell interaction in decidual spiral arteries

Fetal cytotrophoblasts colonize the decidual spiral arteries during pregnancy and partially replace the endothelium by an as yet unknown mechanism. To clarify this issue, we cocultured trophoblast cells (TCs) and decidual endothelial cells (DECs) isolated from first trimester placentae and found by electron microscopic analysis that TCs adhered to DECs and migrated through the interendothelial junctions within 24 h. Since extravillous TCs were shown by FACS analysis to express vascular-endothelial (VE)-cadherin and platelet endothelial cell adhesion molecule-1 (PECAM)-1, we investigated the role of these junctional molecules in TC adhesion to DECs and transendothelial migration of cytotrophoblasts. Both VE-cadherin and PECAM-1 were present at the contact sites between TCs and DECs in decidual sections. TC adhesion and migration were markedly inhibited by mAbs to VE-cadherin and marginally by mAb to PECAM-1. Increased expression of VE-cadherin was observed at the contact areas between TCs and DECs, whereas PECAM-1 was found to be redistributed from intercellular junctions. The induction of apoptosis of DECs by TCs, as the mechanism responsible for their replacement, was ruled out by the negative staining with TUNEL of DECs cocultured with TCs and the absence of DNA fragmentation. In conclusion, VE-cadherin is involved in transendothelial migration of TCs, and replacement of DECs by TCs is not the result of apoptosis.