Choroidal ependymocytes in culture: expression of markers of polarity and function.

Long-term primary cultures derived from fetal mouse or rat choroid plexus were obtained in serum-supplemented media. Monoclonal and polyclonal antibodies to basolateral and apical membrane components were used to observe the expression of specific markers of polarity and function. Choroid plexus cultures and thin frozen sections of adult tissues were compared by immunocytochemistry. Two polyclonal antibodies directed against laminin and fibronectin were used on cultured choroid plexus and sectioned tissues, showing that fibronectin and laminin are located on the basolateral membrane domain in ependymocytes in vitro, as well as in vivo. Na(+)-K(+) ATPase was apically detected by light and electron microscopy with a monoclonal antibody (Mab H30) in both cultured cells and sectioned tissues. Double immunofluorescent staining with Mab H30 and affinity-purified polyclonal antibodies to the alpha subunit of G0 protein (G0 alpha) demonstrated the relatively similar distribution of the two antigens on the apical face of the choroidal tissue, both in vivo and in vitro. The distribution of these markers shows a typical differentiation with maintenance of polarized features in choroidal ependymocytes in culture, testifying that this cell culture system constitutes an interesting model for studying the functional characteristics of ependymal cells of the choroid plexus.