A novel animal model of Meniere’s disease established by postauricular injection of inflammatory soup

BACKGROUND: Endolymphatic hydrops (EH) has long been considered the primary pathological feature of Meniere's disease (MD). Consequently, most existing animal models of MD are EH models, yet they cannot fully reflect all the pathological features of MD. Moreover, the causal relationship between EH and MD remains controversial. The objective of this study is to develop an animal model of MD that accurately reflects the clinical and pathophysiological characteristics of the disease. METHODS: Male C57BL/6J mice aged 6-8 weeks received daily injections of inflammatory soup (IS) at the middle of the right postauricular groove for 5 consecutive weeks. EH was assessed weekly using hematoxylin and eosin staining. Changes in auditory function were evaluated using auditory brainstem response testing and immunofluorescence staining. Vestibular function was assessed using the open-field test, balance beam test, vestibulo-ocular reflex, and immunofluorescence staining. RESULTS: Morphological findings revealed EH in cochlear sections 2 weeks after IS injection. The auditory brainstem response results showed significantly higher thresholds by week 2 after IS injection. The I-wave amplitude decreased as early as week 1 after injection. Immunofluorescence analysis demonstrated reduced inner hair cell synaptic ribbon counts and decreased spiral ganglion cell density. Immediately after each IS injection, the mice exhibited circling behavior and transient agitation, lasting approximately 10 seconds. Decreased locomotor activity was observed in the open-field test at 1, 2, and 5 weeks after IS injection. Vestibular testing showed prolonged balance beam-crossing time at 2 and 5 weeks and reduced vestibulo-ocular reflex gain at 1, 2, and 5 weeks after IS injection. Morphological findings also revealed decreased stereocilia bundle density in the utricle and cristae of the semicircular canals. CONCLUSIONS: This study established an animal model exhibiting several key features of MD, including EH, hearing loss, and vestibular dysfunction. This model may provide a useful experimental tool for investigating the pathogenesis of MD and exploring potential therapeutic strategies.