Résumé
Here we present a simple two-step in vitro model of vascularized trophoblastic tissue derived from human embryonic stem (hES) cells. The first step is the formation of cystic embryoid bodies (EBs) in suspension in a semisolid methyl cellulose medium, within which an endothelial platelet/endothelial cell adhesion molecule-1 (PECAM-1+) cell network develops. In a second step, deposition of these EBs on the bottom of nontreated, polystyrene tissue culture plates, leads by centrifugal outgrowth of the EB to the emergence of an adherent cell layer, with which a PECAM-1+ network is associated. Cells of this adherent layer expressed VE-cadherin (CD144), PECAM-1 (CD31), and α-fetoprotein (α-FP). Trophoblastic differentiation was strongly suggested by the secretion of β-human chorionic gonadotropin (β-hCG) and by the presence of the cytotrophoblast and syncytiotrophoblast marker GB25. The INSL4 gene, a cyto and syncytio-trophoblast marker, was also highly expressed in the adherent layer, as well as other trophoblast genes such as CGA, CDX1, CDX2, and HAND1, compared to hES cell gene expression taken as reference. In contrast, expression of self-renewal genes, such as TERT, POU5F1, ZFP42, GDF3, and NODAL were decreased. No ectodermal or endodermal genes were expressed, but the mesodermal genes PECAM-1 and GATA2 were. The possibility of removing the EBs during the second step would permit analysis of their relative contribution to angiogenesis or possible hemangioblast formation, compared to that of the trophoblastic adherent layer. This primitive vascularized trophoblastic model could also provide a tool to study early steps of normal and pathological placental development.