PORCINE CHOROID-PLEXUS CELLS IN CULTURE - EXPRESSION OF POLARIZED PHENOTYPE, MAINTENANCE OF BARRIER PROPERTIES AND APICAL SECRETION OF CSF-COMPONENTS

We have successfully cultured choroid plexus epithelial cells from por cine brain in pure form by the addition of cytosine arabinoside to the culture medium which prevented growth of other contaminating cells, W e characterized the cells in culture by the presence of desmoplakin, f ibronectin, thrombospondin, and the zonula occludens protein ZO-1 in c omparison to frozen fractions of the isolated choroid plexus tissue, T he cells in culture express those marker proteins and moreover exhibit a polarized phenotype which was expected from the presence of tight j unction strands that correlate to an electrical resistance of 120 Ohm cm(2) measured across the cell monolayer on a permeable support, Perme ability studies with fluorescein-labeled dextrans also indicate a bioc hemical tightness. The polarity of the cells is demonstrated by the pr esence of microvilli and cilia on the surface of the cultured cells as well as by the laser scanning microscopic determination of the apical localization of the ZO-1-protein and the Na+K+-ATPase. Thrombospondin and fibronectin were found to be localized at the basolateral membran e side, The cells in culture secrete medium containing prealbumin pred ominantly into the apical compartment which demonstrates that they are able to release medium containing CSF-proteins and therefore verifies the usefulness of this in vitro model.