Identification of MUC5B mucin gene in human middle ear with chronic otitismedia

Objectives: To identify the mucin gene and its expressing cells in the midd le ear mucosa with chronic otitis media (COM), and to study the correlation between infiltration of inflammatory cells in the submucosa and expression of the mucin gene in the mucosal epithelium with COM Study Design: Middle ear mucosal specimens removed from the inferior promontory area of 19 patie nts undergoing middle ear surgery for COM were studied Methods: Sections we re stained with H&E, Alcian blue-periodic acid Schiff (AB-PAS), polyclonal MUC5B antibody, and specific MUC5B riboprobe for histological, histochemica l, immunohistochemical, and mucin mRNA analyses. Results: H&E staining reve aled pseudostratified epithelia in 18 of the middle ear specimens with COM and cuboidal secretory epithelia in one. AB-PAS staining of epithelia revea led abundant secretory cells and their products (glycoconjugates). In situ hybridization and immunohistochemistry studies demonstrated that the secret ory cells of the middle ear mucosa with COM expressed MUC5B mucin mRNA and its product MUC5B mucin. Conclusions: The MUC5B mucin gene and its product were identified in the middle ear secretory cells of patients with COM. Its expression was extensive in pseudostratified mucosal epithelia and related to infiltration of inflammatory cells in the submucosa of the middle ear c left with COM, suggestive that inflammatory cell products are involved in t he production of MUC5B.