Expression of HERV-W Env glycoprotein (syncytin) in the extravillous trophoblast of first trimester human placenta.

Although the extravillous trophoblastic invasion has a critical role in human placental development, nothing is known about HERV-W expression in the extravillous phenotype. The aim of the present study was to localize in first trimester placenta the expression of HERV-W Env glycoprotein and its receptor all along the differentiation pathway of the extravillous phenotype. In addition using an in vitro model of extravillous cytotrophoblastic cell isolation and invasion we investigated the presence of HERV-W transcripts and envelope glycoprotein in cultured extravillous trophoblastic cells. Using monoclonal and polyclonal antibodies, the glycoprotein was immunolocalized in all the cell types of the extravillous phenotype lineage: cytotrophoblastic cells of the column, interstitial extravillous trophoblastic cells, multinucleated giant cells and endovascular trophoblast. Furthermore, using a polyclonal antibody, the D mammalian virus receptor was also localized in the various extravillous trophoblastic phenotypes. In addition, the presence of HERV-W transcripts and protein was demonstrated in cultured extravillous trophoblastic cells. HERV-W Env glycoprotein expressed in villous and extravillous trophoblast can be considered as a specific marker of the human trophoblast.