Up-regulation of MUC5AC and MUC5B mucin genes in chronic rhinosinusitis.

BACKGROUND: Excess mucus production and hypersecretion characterize upper airway diseases. The primary mechanisms leading to mucus hypersecretion in chronic rhinosinus inflammation are not well understood. Mucus hypersecretion is commonly accompanied by goblet cell and submucosal gland cell hyperplasia. It is important to identify which mucin gene messenger RNAs (mRNAs) are expressed in the sinus mucosa.

OBJECTIVES: To investigate the expression of MUC5AC and MUC5B mRNAs and localization of these proteins in human sinus mucosa and to compare the expression of MUC5AC and MUC5B mRNAs in normal and in chronic sinus mucosa.

DESIGN: Twenty chronic maxillary sinusitis mucosa samples and 20 normal maxillary sinus mucosa samples were obtained; RNAs were extracted from sinus mucosa, and semiquantitative reverse transcription-polymerase chain reaction was performed for MUC5AC and MUC5B. Localization of these proteins was sought by using immunohistochemical analysis.

RESULTS: The levels of MUC5AC and MUC5B mRNA in chronic rhinosinusitis were significantly increased compared with those in normal sinus mucosa (P =.02). In inflammed sinus mucosa, MUC5AC protein was expressed in the cytoplasm of the goblet cell in the surface epithelium, and MUC5B expression was restricted to mucous cells of the submucosal glands and to the epithelium of sinus mucosa. However, in the normal sinus mucosa, MUC5AC and MUC5B proteins were expressed at low levels in the sinus epithelium and submucosal glands, respectively.

CONCLUSION: These results suggest that up-regulation of MUC5AC and MUC5B, which are major components of respiratory secretion in chronic rhinosinusitis, may play important roles in the pathogenesis of sinus hypersecretion in chronic rhinosinusitis.