Inner Ear Tissue Remodeling and Ion Homeostasis Gene Alteration in Murine Chronic Otitis Media

Abstract

Studies were designed to ascertain the impact of chronic middle ear infection on the numerous ion and water channels, transporters, and tissue remodeling genes in the inner and middle ear. Permanent sensorineural hearing loss is a significant problem resulting from chronic middle ear disease, although the inner ear processes involved are poorly defined. Maintaining a balanced ionic composition of endolymph in the inner ear is crucial for hearing; thus, it was hypothesized that this may be at risk with inflammation. Inner and middle ear RNA collected separately from 6-month-old C3H/HeJ mice with prolonged middle ear disease were subjected to qRT-PCR for 8 common inflammatory cytokine genes, 24 genes for channels controlling ion (sodium, potassium, and chloride) and water (aquaporin) transport, tight junction claudins, and gap junction connexins, and 32 tissue remodeling genes. Uninfected Balb/c mice were used as controls. Significant increase in inner ear inflammatory and ion homeostasis (claudin, aquaporin, and gap junction) gene expression, and both upregulation and downregulation of tissue remodeling gene expression occurred. Alteration in middle ear ion homeostasis and tissue remodeling gene expression was noted in the setting of uniform upregulation of cytokine genes. Chronic inflammatory middle ear disease can impact inner ear ion and water transport functions and induce tissue remodeling. Recognizing these inner ear mechanisms at risk may identify potential therapeutic targets to maintain hearing during prolonged otitis media.