Interleukin-1-containing cells in cholesteatoma of the middle ear

Abstract

Cholesteatoma of the middle ear and the adjacent temporal bone consists of hyperproliferative keratinizing squamous epithelium in the middle ear cavity, and is capable of destroying the bone. Interleukin-1 (IL-1), an autocrine growth factor for epithelial keratinocytes, is characterized by its capacity to initiate bone absorption. Using immunohistochemical methods, the distribution of two different species of interleukin, IL-1 alpha and IL-1 beta, in cholesteatoma tissue (Fig. 2), the skin of the external ear canal, and the retroauricular region was investigated (Fig. 1). Comparable amounts of both IL-1-species were found in all squamous epithelia examined, but interleukin in cholesteatoma epithelium was increased in comparison with normal epidermis. All cellular layers stained uniformly and equally strongly for IL-1 alpha and IL-1 beta, whereas the dead cells of the keratin layer were negative for both. Some intensely stained cells were found scattered in the connective tissue underlying the basal layer of the cholesteatoma (Fig 4). Using double staining techniques these cells were shown to be mainly macrophages (Fig 6). Our results suggest that IL-1 could be liberated from disintegrating keratinocytes and cells of the monocyte-/macrophage lineage, and stimulate the proliferation of the cholesteatoma epithelium in an autocrine manner, thus contributing to the increased bone destruction seen in cholesteatoma.