CHARACTERIZATION OF CELL POLARITY AND EPITHELIAL JUNCTIONS IN THE CHORIOCARCINOMA CELL-LINE, JAR

In the placenta the trophoblast cell layer separates maternal and feta l circulations and is involved in the active transport of selected sub stances across this barrier. We have used the JAR choriocarcinoma; cel l line to study aspects of trophoblast membrane transport. To determin e whether JAR cells could be used in studies of vectorial transepithel ial transport it mbs necessary to determine whether these cells were p olarized and assembled tight junctions. In the present study we invest igated JAR cells using a range of markers for specific cell surface do mains combined with confocal laser scanning microscopy. Freshly isolat ed cells initially formed a confluent epithelial monolayer with recrui tment of a tight junction-associated protein, ZO-1, and a cell adhesio n molecule, E-cadherin, to the surface at sites of cell-cell contact. They did not, however, display cell surface polarization as NaK-ATPase was not segregated in the basolateral domain, and a differentiated ap ical cell surface was not assembled. The monolayer stage was also unst able, as continued proliferation resulted in the formation of multilay ered aggregates where ZO-1 and E-cadherin were lost from the cell surf ace. These results suggest that the JAR cell line is unlikely to be a suitable model for studies of transepithelial transport in the placent a.