ITO CELL HETEROGENEITY - DESMIN-NEGATIVE ITO CELLS IN NORMAL RAT-LIVER

The presence of desmin is used to identify Ito cells in rat liver and to evaluate the purity of separated and cultured Ito cells. Heterogene ity of the normal Ito cell population has been suggested; this could i nclude variations in the content of cytoskeletal components. For these reasons we decided to reevaluate the use of desmin staining as a phen otypical marker of Ito cells in normal rat liver. Our approach was to combine desmin staining with identification of vitamin A (autofluoresc ence), lipid droplets (Sudan III), vimentin, laminin and tenascin, usi ng cryostat sections: Immunofluorescence, double-immunofluorescence or immunoperoxidase techniques were used. All the techniques described c orroborate the existence of desmin-negative Ito cells, mainly located in pericentral areas. In fact, lobular desmin-positive cells showed un even distribution because they were more frequent in periportal than i n pericentral areas. On the contrary, Ito cells identified on the basi s of morphological criteria or positivity for laminin were evenly dist ributed. Double immunofluorescence confirmed this observation, showing nearly complete codistribution of laminin and desmin in periportal ar eas. Outside this area, positivity for desmin was observed only in abo ut 50% of laminin-positive cells. Our observations suggest that desmin cannot be viewed as a phenotypical marker but rather is a differentia tion marker of Ito cells, possibly indicating a specific functional st ate.