Cytokeratin diversity in epithelia of the human inner ear

The expression of cytokeratins (Cks) nos. 5, 7, the combination 5 and 8, 8, 10, 17, 18 and 19 was analysed in the inner ear of 14-24-week-old human fetuses, using 10 different well characterized monoclonal antibodies (mAbs). A complex pattern of Ck immunoreactivity was found. Cks 8 and 18 were identified in both cochlear and vestibular hair cells as well as in all other epithelia. Epithelia involved in fluid regulation (stria vascularis, Reissner's membrane and dark cell epithelium) revealed the same pattern of Ck immunoreactivity in spite of morphological differences in cell configuration. A specific Ck, no. 10 as detected with the mAbs RKSE 60, was found in the endolymphatic duct and sac. The expression of Cks in the human inner ear is in principle similar to that found in the labyrinth of other animal species, for instance in the mouse. However, the human inner ear had a more complex pattern than any inner ear so far known in animal species.