involucrin and Ear-Diseases

A histochemical study was performed to clarify further the role played by epidermal transglutaminase (ETgase) in the keratinization of aural cholesteatoma. Weakly and strongly keratinized epidermal tissues and healthy middle ear mucosa were included as references. A first assay revealed the distribution of non-specified acyl donor substrates. In a second assay, the topography of involucrin was assessed immunohistochemically. In both epidermal and cholesteatoma matrix tissues, the presence of acyl donors was not restricted to the sites of (E)Tgase activity, but was almost uniformly extended throughout living layers. In reference tissues, residual acyl donors were poorly detected in horny layers, while they were more abundant in the stratum corneum of the cholesteatomas studied. The presence of involucrin along the cell membrane was observed at varying distances throughout the spinous and granular layers, depending upon the epidermal and matrix configurations. In thick epithelia, involucrin rapidly became concentrated at the cell periphery (in spinous keratinocytes), while in thin epithelia it was usually associated with cell flattening. This latter staining profile was observed more frequently in cholesteatomatous tissues. In addition, we regularly noticed an immediately suprabasal accumulation of involucrin, suggesting a locally hyperproliferative state of the matrix. An insufficient availability of acyl donors, especially involucrin, could not be used to explain the defective ETgase-mediated cross-linking of cholesteatoma cell membranes during terminal stages of differentiation. The present investigation may be the first to demonstrate the presence of involucrin in middle ear mucosa.

Topics: Cholesteatoma; Ear Diseases; Ear, Middle; Humans; Immunoenzyme Techniques; Keratins; Mucous Membrane; Protein Precursors; Transglutaminases

Immunolocalization of involucrin in human middle ear cholesteatoma was performed with specific rabbit anti-human involucrin antibody. Involucrin was noted prominently in the cytoplasm of the suprabasal cells, including spinous cells and granular cells. The pattern of distribution of involucrin in cholesteatoma shows its epidermal characteristics. Immunostaining of involucrin was also made in tympanic membrane and external ear canal skin. As for comparing its distribution, a larger amount of involucrin was present in cholesteatoma (60%) than in external ear canal skin (29%) in our study and in normal skin (25%) in another study. This suggests active differentiation of the epithelial cells in cholesteatoma. Further investigation on the inhibition of involucrin formation may have some effect in the treatment of cholesteatoma.

Topics: Cholesteatoma; Ear Diseases; Ear, External; Ear, Middle; Fluorescent Antibody Technique; Humans; Immunoenzyme Techniques; Protein Precursors; Skin; Tympanic Membrane