Cochlear cytokine gene expression in murine chronic otitis media.

Abstract

To investigate chronic otitis media (COM) induction of cochlear cytokine genes. RNA from cochleas of five C3H/HeJ mice with and without COM was isolated for cytokine expression in gene arrays. Immunohistochemistry was performed for the protein products of up-regulated genes to confirm their expression in cochlear tissues. Cochleas from COM mice showed increased expression of 29 genes (>2x normal) and decreased expression of 19 genes (<0.5x normal). Cytokines expressed were largely those related to inflammation and tissue remodeling. Cochlear immunohistochemistry confirmed the presence of numerous cytokines, as well as NF-kB, a major inflammatory transcription factor that drives cytokine expression. COM causes elevated levels of cochlear cytokine mRNA, which demonstrates that inner ear tissues are capable of NF-kB activation and cytokine production. This may be another mechanism of otitis media-induced cochlear cytotoxicity in addition to that caused by migration of inflammatory cytokines from the middle ear. Cochlear tissues are capable of mounting an immunological response to middle ear inflammatory stimuli.