Ultrastructural changes and immunocytochemical analysis of human placental trophoblast during short-term culture.

Trophoblastic cells, of at least 95 per cent purity by immunofluorescence and morphological criteria, were obtained from human term placenta by a simple trypsinisation method without the additional purification steps or complex culture conditions used by others. The differentiation of these cells was followed over four days in culture by fluorescence immunocytochemistry, by scanning and transmission electron microscopy and by light microscopy. The results support the idea that the isolated cells are cytotrophoblast and that these differentiate during this time into cells with characteristics of villous syncytiotrophoblast. This process involved first the formation of a multicellular layer of mononucleated cells, then the development of a syncytium of multinucleated cells and, not necessarily concurrently, functional differentiation. This may be a useful model for the study of syncytiotrophoblast function.