MUC5B expression in middle ear effusions: the main gel-forming mucin responsible for viscous properties of middle ear effusions

ABSTRACT

Several mucin genes are expressed in the middle ear mucosa resulting in the development of middle ear effusion. However, the detailed mucin protein expression in middle ear effusions has not been studied in individual effusions. This study aimed to explore the expression patterns of the 3 main secretory mucins, known to be expressed in the air-ways, in individual middle ear effusions with studying the possible correlation with the effusion viscosity. Middle ear effusions were collected under general anesthesia from 30 children with otitis media with effusion. The viscosity of individual effusions was studied. Mucins were extracted from the individual effusions and their antigenic identity was studied with ELISA. Mucoid effusions have significantly higher viscosity and mucin content than serous effusions. MUCs2, 5AC and 5B were expressed in middle ear effusions within a wide range. MUC5B was the most abundant mucin with significantly strong positive correlation with the viscosity of middle ear effusions. Middle ear epithelium expresses MUC5B as the major secretory mucin which is likely to be the main determinant of the viscosity, and hence physical and biological characteristics, of middle ear effusions. A secondary role is played by MUC5AC and, to a small extent, by MUC2. This could have significant clinical implications. MUCsSB, 5AC and 2 are expressed in middle ear effusions with MUC5B representing the major secretory mucin which is also the main determinant of mucin viscosity. The clinical implications of these findings need further studies