Investigation of the role of ILC2 in middle ear mucosa using a novel model of eosinophilic otitis media.

Abstract

OBJECTIVE: Eosinophilic otitis media (EOM) is considered a type 2 inflammation of the middle ear mucosa. In this study, we investigated the role of type 2 innate lymphoid cells (ILC2s) in EOM using a novel animal model locally stimulated with a plant protease Papain. METHODS: Hartley Guinea pigs were injected with 25 μg of Papain into the tympanic cavity daily for 12 days. Eosinophil infiltration and mucin production in the middle ear mucosa were examined histologically, and the localization of ILC2s was investigated using immunohistochemical methods. RESULTS: In the Papain-stimulated group, a significantly larger number of eosinophils were observed in the middle ear mucosa, and mucin enriched with eosinophils was observed around the tympanic ostium of the Eustachian tube. The number of ILC2s in the middle ear mucosa of the stimulated group significantly increased compared to the control group. CONCLUSION: This is the first report on Papain-induced allergic disease models in the middle ear. In the stimulated group, hyperproduction of mucin containing eosinophils in the tympanic cavity and increased ILC2s in the mucosa were observed. The novel model presented in this study may contribute to the elucidation of the pathogenesis of EOM as a type 2 inflammation.