The invasion of an extravillous trophoblast (EVT) into maternal decidual tissues, especially
towards maternal spiral arteries, is an essential process in the human placental formation and subsequent
normal fetal development. However, the precise regulatory mechanisms to induce EVT invasion
towards arteries and/or to protect EVT from further invasion are not well understood. We found that a
chemokine receptor, CCR1, was specifically expressed on EVT migrating towards maternal arteries.
Using EVT isolated from a primary villous explant culture, RANTES, which is one of the ligands for
CCR1, was shown to enhance EVT invasion. Furthermore, we observed that the platelets were deposited
among intravascular EVT and platelet-derived soluble factors, which contained RANTES, enhanced
EVT invasion. On the one hand, dipeptidyl peptidase IV (DPPIV), which can metabolize
RANTES on the cell surface, was expressed on non-invading EVT and was demonstrated to suppress
EVT invasion. In contrast, laeverin/aminopeptidase Q, which is specifically expressed on EVT, was
shown to induce EVT invasion. Also, CD9 which is a cell surface marker of platelets and a regulator of
integrin function was expressed on EVT and gene knockdown of the CD9 molecule enhanced EVT invasion.
These findings suggest that the chemokine-chemokine receptor, chemokine-peptidase, and
CD9-integrin systems play important roles in the regulation of EVT invasion during early human placental