Cell cooperation on bone resorption in chronic otitis media

Effect of HA-1A monoclonal IgM antibody on endotoxin-induced proliferation of cultured rat middle ear epithelium

The effect of human monoclonal antibody HA-1A (Centoxin) on the effect of endotoxin on cultured rat middle ear epithelium was investigated. The addition of endotoxin to the standard culture medium revealed a concentration-related proliferative effect on cultured rat middle ear epithelium, leading to cobblestone cells, cell tracks, and stratification of epithelium, whereas rat middle ear epithelium cultured in standard medium grew as a monolayer composed of flat polygonal cells. Addition of HA-1A to standard medium supplemented with endotoxin gave rise to a statistically significant suppression of the proliferative effects of endotoxin on these cells. The morphology of rat middle ear epithelium cultured in the presence of HA-1A and endotoxin showed that these cells still had a tendency to form cobblestone-like cells and cell tracks, but to a substantially lower degree. The present results support the hypothesis that HA-1A suppresses the proliferative and morphological effects of endotoxin on rat middle ear epithelium and may play an important role in the pathogenesis of otitis media.

Localization of Cytokines in Cholesteatoma Tissue

Acquired cholesteatoma is associated with an intense inflammatory reaction with resuitant tissue and bone destruction. Cytokines are molecules released by inflammatory cells at the site of infection and are potent mediators of inflammation and the immune response. Five cytokines, tumor necrosis factor-α, transforming growth factor-β1 and 2, and interleukin-1 and 6, were immunolocalized in human cholesteatoma epithelium and subepithelial stroma, with greater intensity of staining compared with noninflamed external auditory canal skin. Increased interleukin-6 activity in cholesteatoma epithelium and stroma correlated significantly with the presence of ossicular and bony erosion and granulation tissue noted intraoperatively. Transforming growth factor-β2 activity in cholesteatoma epithelium correlated significantly with bony erosion at surgery. Additionally, transforming growth factor-β1 activity in cholesteatoma epithelium correlated significantly with increased length of disease. Tumor necrosis factor-a, interleukin-1, and interleukin-6 appear to be involved in the inflammation and resultant remodeling associated with cholesteatoma. We hypothesized a protective function of transforming growth factor-β1 and 2 in the presence of cholesteatoma. The antiinflammatory and osteoclast and keratinocyte inhibitory actions of the transforming growth factor-βs could potentially slow the proliferation and resultant tissue destructiveness associated with Cholesteatoma.

Platelet-derived growth factor in middle ear cholesteatoma

Platelet-derived growth factor (PDGF) was localized in human middle ear cholesteatoma tissue by an immunoperoxidase technique using rabbit anti-human PDGF IgG. PDGF was found mainly in basal cells and in granulation tissue, and especially involved monocytes and fibroblast-like cells. The external ear canal epithelium was not significantly stained by anti-human PDGF. Findings demonstrate that the presence of PDGF in cholesteatoma is in response to inflammation and wound healing in the middle ear. PDGF in vitro was found to stimulate protein synthesis and cellular terminal differentiation of basal keratinocytes. PDGF also stimulated monocytes to form multinucleated osteoclast-like cells. These multinucleated cells, in turn, induced the resorption of devitalized bovine bone. This bone resorption was seen in co-cultures of osteoblasts and multinucleated osteoclast-like cells in the presence of PDGF, suggesting that cell-to-cell interaction plays a role in bone resorption. The present study suggests that PDGF takes part in the clinical development and the destructive effect of cholesteatoma.

The role of tumor necrosis factor-alpha in bone resorption of cholesteatoma

Recent investigations have indicated that cytokines such as tumor necrosis factor-alpha (TNF-alpha) play a potential role in the bone resorption associated with inflammatory diseases. In this immunoperoxidase study, TNF-alpha was localized in mononuclear cells, macrophages, fibroblasts, osteoblasts, and osteoclasts adjacent to bone resorption areas in both human and experimental middle ear cholesteatomas. In vitro, TNF-alpha stimulated monocytes to form multinucleated cells that demonstrate tartrate-resistant acid phosphatase activity, a marker enzyme for osteoclasts. These multinucleated osteoclast-like cells induce resorption of devitalized bone. The extent of bone resorption was increased by the co-cultures of osteoblasts and osteoclasts in the presence of TNF-alpha, suggesting that cell to cell interaction plays a significant role in bone resorption. Moreover, TNF-alpha was capable of stimulating macrophages to produce acid phosphatase and collagenase, and osteoblasts to produce prostaglandin E2 and collagenase. These chemical mediators have been known to lead to bone resorption. Our findings suggest that TNF-alpha may play an important clinical role in the destructive process of cholesteatoma.

Localization of interleukin-1 in human cholesteatoma

Recent studies by other investigators have shown that interleukin-1 (IL-1) promotes bone resorption by stimulating various cells. Interleukin-1 not only stimulates collagenase production by fibroblasts and macrophages, but also acts as an osteoclast-activating factor. In this study, IL-1 was localized in human cholesteatoma tissues using both immunoperoxidase and immunofluorescent-staining methods with specific monoclonal antibodies. Highly concentrated IL-1 was found in the epithelial layer and granulation tissue. More specifically, intense staining was seen in basal and spinous cells of the epithelial layer, and in fibroblasts and macrophages of the granulation layer. We also located IL-1 in the normal external ear canal skin; however, the intensity of the staining in the cholesteatoma epithelium was found to be stronger. The presence of IL-1 in the epithelial layer and granulation tissue of the cholesteatoma suggests that IL-1 from the stimulated keratinocytes of the cholesteatoma could be one factor responsible for the markedly increased bone resorption observed in cholesteatoma patients.

Role of polymorphonuclear leukocytes in collagenase production in chronic otitis media

The effect of polymorphonuclear leukocytes on collagenase production by fibroblast-like cells was studied in an in vitro cell culture system. An extract of rat intraperitoneal polymorphonuclear leukocytes induced significant collagenase production by rat skin fibroblast-like cells. Fibroblast-like cells cultured in the presence of polymorphonuclear leukocytes had many conspicuous microspikes on their surface and contained bundles of actin filaments in their cytoplasm. Polymorphonuclear leukocytes appears to be involved in bone resorption by inducing collagenase production by fibroblast-like cells, as well as by releasing their own enzymes involved in bone resorption.