Growth and differentiation of meatal skin grafts in the middle ear of the rat.

Abstract

To determine the behavior of epidermal cells after transplantation in the middle ear. In a rat model, full-thickness meatal skin grafts were transplanted into the middle ear and studied morphologically and immunohistochemically with the use of antibodies directed against different cytokeratin (Ck) polypeptides, which are markers of different types of epithelial cell differentiation. The grafts had either transformed into epithelial cysts or had become integrated into the middle ear epithelium. The epithelium of the integrated grafts showed gradual transition into the epithelium of the middle ear. A clear distinction between epidermal cells and middle ear epithelium could be made only on the basis of their Ck profiles. The Ck profiles of the grafts revealed a decrease in the expression of epidermal Cks, while nonepidermal Cks became expressed. These changes can be ascribed to replacement of the dermal mesenchyma by mesenchyma from the middle ear. In two ears with superimposed infection, the graft epithelium showed expansive growth. Meatal epidermis is well tolerated in the middle ear, but superimposed infection can induce expansive growth. These findings favor the concept that the progressive growth of cholesteatoma is related to the presence of inflammatory processes.