Aural cholesteatomas arise from the tympanic membrane as a sequela of otitis media. Cholesteatomas are progressive, epithelial lesions which destroy the bony structures of the middle and sometimes inner ear. Once established, cholesteatomas can only be managed by surgical eradication and secondary middle ear reconstruction. The long term objective of this research program is to understand the cellular mechanisms which lead to the development, progression and bone destruction of cholesteatomas. Such an understanding may lead to strategies for the non-surgical prevention and management of this disease.
The specific aims of this application are to investigate the cellular biology of three cell types that appear to be important in cholesteatoma progression: the KERATINOCYTE, the FIBROBLAST, and the OSTEOCLAST. The gerbilline retraction pocket cholesteatoma model will be used to investigate the alteration and the expression of 1) cytokeratins, 2) the plasminogen activator cascade components, and 3) the interleukin-1 family within keratinocytes in developing cholesteatomas. Quantitative immunohistochemistry, histomorphometry, 3H-thymidine incorporation, 3H- uridine incorporation and in situ hybridization will be used to test hypotheses regarding KERATINOCYTES. The propensity of cultured FIBROBLASTS from induced cholesteatomas to invade synthetic basement membrane will be compared to control fibroblasts. Conditioned medium from these cultures will be tested for bone resorbing activity in the mouse calvarial organ culture system. Prior studies have indicated that local factor(s) are produced at the bone surface which lead to recruitment of OSTEOCLAST precursors and activation of osteoclasts. Localized bone resorption will be induced in vivo using the pressurized bulla model. 3H-uridine incorporation into bone cells will be used as a measure of increased RNA transcription. A potential role of interleukin-1 in osteoclastic activity in vivo and in vitro will be investigated by attempting to block induced, localized bone resorption with the recently discovered interleukin-l receptor antagonist. The potential of the tissue-type, and urokinase-type plasminogen activators to affect osteoclastic resorption will be determined using the mouse calvarial organ culture.
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