Cochlear cytokine gene expression in murine chronic otitis media

Objective: To investigate chronic otitis media (COM) induction of cochlear cytokine genes. Study Design: 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. Results: Cochleas from COM mice showed increased expression of 29 genes (>2× normal) and decreased expression of 19 genes (<0.5× 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. Conclusion: 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. Significance: Cochlear tissues are capable of mounting an immunological response to middle ear inflammatory stimuli.