Bone Resorption in Chronic Otitis Media

Abstract

Bone resorption is an important aspect of chronic otitis media contributing to many complications of this disease. It is postulated that the mechanism of this localized destructive process is chemical in origin. Collagenase, lysosomal enzymes, prostaglandins, and other cell mediators are thought to induce bone resorption, but the site of action and cellular origin of these substances remains unclear. In this report, we demonstrate the location and attempt to delineate the cellular origin of two enzymes, collagenase and the lysosomal enzyme acid phosphatase in guinea pig temporal bones and human ossicles from ears containing chronic otitis media. Tissue localization of these enzymes identifies sites of active bone resorption and demonstrates the cells initiating this process. Using immunohistochemical and immunocytochemical techniques, collagenase was seen surrounding mononuclear inflammatory cells of granulation tissue at bone resorbing margins and at the periphery of osteocyte lacunae adjacent to resorbing areas. Electron microscopic data suggests that collagenase is an extracellular enzyme foun at the periphery of osteocytes. In addition, abundant acid phosphatase activity was seen in the same cells that exhibited collagenase staining, lending credence to the destructive function of these cells. The chronic inflammatory reaction found in chronic otitis media appears to activate bone destruction through the dynamic activity of mononuclear inflammatory cells and stimulates bone cells to increase their destructive biochemical functions.