Colocalization of three types of intermediate filament proteins in perisinusoidal stellate cells: glial fibrillary acidic protein as a new cellular marker.

The presence and the colocalization of the three intermediate filament proteins, glial fibrillary acidic protein (GFAP) and the marker of mesenchymal liver cells, vimentin, were studied by an immunofluorescence double-labeling technique in cultures of isolated rat perisinusoidal stellate cells (PSC) and hepatocytes, in cocultures of isolated PSC and hepatocytes as well as in cryostat sections of rat liver. GFAP and vimentin immunoreactivities were localized in cultured PSC which were identified by the presence of the cellular marker desmin, another intermediate filament protein, or the stellate morphology to be seen after staining for one of three intermediate filament proteins. Both GFAP and vimentin were strongly expressed in the perinuclear region and the cell processes of cultured PSC. Staining for GFAP highly coincided with that for vimentin or desmin in cultured PSC and with that for vimentin in the liver sections. Desmin-positive cells were always also GFAP-positive. However, of the GFAP-positive cells only an estimated 50% were found desmin-positive. The coexpression of desmin and GFAP in the same cells appear to be unique, since apparently it has not been previously reported for any other cell type. Almost all of the vimentin-positive cells in hepatocyte culture were also expressing GFAP. Since desmin was not found in all of the cultured cells with PSC morphology, GFAP is suggested as a more reliable marker for PSC than desmin.