Expression of intermediate filament proteins in the mature inner ear of the rat and guinea pig.

The expression of intermediate filament proteins was studied in the mature inner ear of the rat and guinea pig, using a panel of polyclonal and monoclonal antibodies directed against cytokeratins, desmin, neurofilament proteins and glial fibrillary acidic protein (GFAP). The epithelial lining of the endolymphatic space displayed a complex expression pattern of cytokeratin filament proteins, suggesting greater cell diversity than was known sofar from morphological studies. The cytokeratin antibodies when applied to the inner ear tissues revealed the presence of only cytokeratin polypeptides which are typical of simple epithelia (i.e. nos. 7, 8, 18, and 19). Profound differences in cytokeratin expression patterns were, however, found in the various cell types of both the cochlear and vestibular partition. Remarkably, the sensory cells appeared to be devoid of both cytokeratins and neurofilament proteins. Staining with a 200 kDa neurofilament antibody displayed the presence of different populations of ganglion cells in the spiral ganglion and the vestibular ganglion. There was no reaction with antibodies directed against desmin and GFAP. The great resemblance of the intermediate filament protein expression patterns in the inner ear of the rat and guinea pig indicates a close similarity between the different epitopes.