Migration cellulaire a partir des villosités crampons lors du développement du placenta humain

Anchoring villi are trophoblastic specialisations that attach the placenta to maternal tissue. They also supply the extravillous trophoblastic populations that colonise the decidua and arteries during early pregnancy. We have used explant culture on collagen I gel to examine factors that influence the de novo development of anchoring sites and have compared the ultrastructure of cells in this system with those from anchoring villi in vivo. Anchoring villi in vivo show thickening of the basement membrane overlying the attachment area and here the cytotrophoblast breaks through the syncytium to form a column of cells. Cells in the columns develop arrays of intermediate filaments and show dilation of the endoplasmic reticulum. Extracellular fibrinoid matrix material is also found. Cells on the periphery detach and migrate into the stroma. In the explant model, there was rapid outgrowth of tissue and ultrastructural features were found to be similar to those seen in vivo. Antibodies that block the interaction between fibronectin and integrin α5β1 disrupted column morphogenesis. The gel explant culture system provides a good model for the formation of anchoring villi. The interaction between fibronectin in the columnar extracellular matrix and its receptor integrin α5β1 on extravillous cytotrophoblast is critical for placental-decidual stability and anchorage.