Immunohistochemical distribution of extracellular matrix components and keratin in experimentally induced otitis media

The distribution of collagen types I, In, and IV and of laminin, fibronecti n, and keratin was studied in otitis media experimentally induced by Strept ococcus pneumoniae in the chinchilla. The expression of interstitial collag en types I and III and of fibronectin was increased in the subepithelial sp ace that was thickened by inflammation in the acute period of infection. Th e expression of collagen type IV in the subepithelial space could be seen i n the early period. The epithelial cells in the middle ear changed from fla t cuboidal to pseudostratified columnar in pneumococcus-inoculated ears, an d the number of keratin-positive epithelial cells in the middle ear increas ed remarkably after infection. These results indicate that changes in epith elial cell differentiation effected by the extracellular matrix con elate w ith changes in expression of keratin. It is proposed that the extracellular matrix may contribute to tissue repair in the middle ear after bacterial i nfection by interfering with cell proliferation of epithelial cells and fib roblasts.