Characterization of human villous and extravillous trophoblasts isolated from first trimester placenta

Trophoblasts of the human placenta differentiate along two pathways to give either extravillous cytotrophoblasts (EVCT) with invasive properties and t hat are implicated in the implantation process, or villous cytotrophoblasts (VCT) that by cell fusion form multinucleated syncytiotrophoblasts. We rep ort the first isolation and purification of these two cell types from the s ame chorionic villi of first trimester human placenta. We also studied thei r differentiation in vitro. Electron microscopy showed that in contrast to VCT, EVCT had no microvilli but contained large fibrinoid inclusions. EVCT cultures required a matrix to invade, and as previously established, VCT cu ltured on plastic dishes aggregated and fused to form syncytiotrophoblasts. These differentiation processes were characterized by a particular pattern of gene expression as assessed by real-time PCR and confirmed by immunocyt ochemical analysis of the corresponding proteins. EVCT cultured in vitro ex pressed high levels of HLA-G, c-erbB2, human placental lactogen, and very l ittle human chorionic gonadotropin. Interestingly, TGF beta2 was a marker o f EVCT in vitro and in situ. These data offer a new tool for cell biologist s to study the molecular mechanisms involved in human placental development and its pathology.