Differentiaton of Human Cytotrophoblast into Syncytiotrophoblast in Culture

Abstract

The trophoblast performs many important functions during pregnancy: it mediates the transport of nutrients between maternal and fetal circulations, and secretes steroid and protein hormones (Loke and Whyte, 1983). It is also believed to play an active role in immunoglobulin transport from mother to fetus (Wood et al., 1982), and in the prevention of rejection of the fetus by the mother (Lala et al., 1983). The regulation of these activities is poorly understood. The availability of a system to study purified trophoblasts in vitro would facilitate research on the cell biology of this tissue. In an earlier report (Kliman et al., 1986), we described such a system for 1) the isolation of cytotrophoblasts from human term placentae by enzymatic digestion and Percoll-gradient-centrifugation, and 2) the transformation of these mononuclear cells into syncytial structures in culture. In this report, with the aid of scanning electron microscopy, we document the morphological changes occurring as cytotrophoblasts form syncytiotrophoblasts in vitro. We also use immunocytochemistry to study the appearance of human chorionic gonadotropin (hCG) and pregnancy-specific β₁glycoprotein (SP₁), as the trophoblasts differentiate from single cells to syncytiotrophoblasts. We also describe double antibody immunocytochemical localization of hCG and human placental lactogen (hPL). Finally, we examine the pattern of hCG and progesterone secretion by trophoblasts in culture.