Background: Cathepsin D decomposes cytoplasmic proteins, cell organelles, collagen, elastase and proteoglycans. It takes part in angiogenesis and activates osteoclasts, and is thought to play a major role in the destruction of bone tissue by cholesteatoma. The aim of the present study was to evaluate the activity of cathepsin D in the structures of cholesteatoma.
Material/Methods: Cholesteatomas were collected from 16 patients operated on for chronic inflammation of the middle ear. Specimens were fixed in formalin at pH 7.2, after which parrafin slices were made. Cathepsin D was assayed with a Dako set. Keratin was measured by the Kreyberg method. Normal skin from behind the ear was taken from the patients during the same operation. The samples included a stratified, desquamative epithelium (matrix), a streak containing connective tissue (perimatrix), and a mass of keratin debris.
Results: Cathepsin D demonstrates high activity in perimatrix cells adjacent to bone tissue, while it occurs in trace amounts in the matrix. A highly positive reaction was observed within keratin, which was present in the superficial layer of the epithelium. Pseudocathepsin located in desquamative epithelial cells demonstrated a high positive reaction. There were trace amounts of cathepsin D within the dermis. In the control group (the skin samples), there were trace amounts of cathepsin D within the corneous layer of the epithelium.
Conclusions: Cathepsin D places a major role in bone tissue destruction due to cholesteatoma.

Keywords: Cholesteatoma, Cathepsin D, Kreyberg method