Increased IL-1β and Decreased SOD2 mRNA Expression in Cholesteatoma Compared with Postauricular Skin in Cholesteatomatous Otitis Media

Background: Cholesteatomatous otitis media (CholeOM) is a non-cancerous growth characterized by severe clinical manifestations, a high risk of complications, and a high rate of recurrence after surgery, but understanding of its pathogenesis is incomplete. This study investigated the relationships of the expression levels of IL-1β (a pro-inflammatory cytokine), NOX4 (an NADPH oxidase), and three antioxidant genes (CAT, HO-1, and SOD2) with the pathogenesis and clinical features of CholeOM. Methods: Clinical and audiological characteristics were evaluated in 60 patients undergoing surgery for CholeOM. The mRNA expression levels of five target genes (IL-1β, NOX4, CAT, HO-1, and SOD2) were determined by quantitative real-time PCR in successfully extracted unpaired surgical cholesteatoma (n = 23) and postauricular skin (n = 32) tissue specimens. Results: Otorrhea was present in 58.3% of patients, bacterial cultures were positive in 16.7% of patients, and conductive hearing loss (63.3%) was more common than sensorineural hearing loss (35.0%) and normal hearing (1.7%). Comparison of gene expression in cholesteatoma and postauricular skin indicated the cholesteatoma had significantly greater expression of IL-1β (p = 0.024) and significantly less expression of SOD2 (p < 0.001), but there were no differences in the expression of NOX4, CAT, and HO-1 (all p > 0.05). The expression of these five genes in cholesteatoma was unrelated to sex, history of revision surgery, presence of otorrhea, or type of hearing loss (all p > 0.05). Conclusions: Comparison of gene expression indicated cholesteatoma had significantly increased expression of IL-1β and decreased expression of SOD2 compared to postauricular skin. These changes highlight distinct inflammatory and oxidative stress profiles in cholesteatoma tissue, though causal links to the initial pathogenesis of CholeOM require further investigation using normal middle-ear mucosa controls.