EPIDERMAL DIFFERENTIATION IN THE HUMAN EXTERNAL AUDITORY MEATUS

The differentiation of epidermis in the various parts of the human ear canal was documented on the basis of cytokeratin (Ck) expression patt erns. Immunohistochemistry was performed on cryostat sections of norma l meatal skin using a comprehensive panel of monospecific Ck antibodie s representing the main lines of epithelial differentiation. The epide rmis of the cartilaginous part showed a Ck profile characteristic of n ormal skin type differentiation. The deep meatal skin, including the t ympanic membrane, showed a peculiar type of differentiation: in additi on to epidermal Cks, hyperproliferation-associated Cks 6, 16, and 17 w ere expressed in the suprabasal cells, while the simple epithelial cel l marker Ck 19 was found in the basal cells. The presence of hyperprol iferative Cks in the deep meatal skin could only partly be related to areas of proliferative activity. Keratinocytes, which express markers of hyperproliferation, are migratory. Therefore, their presence in the meatal skin is likely to be related to the peculiar pattern of kerati nocyte migration, the purpose of which is to keep the meatus free from desquamation products.