Mixed nasal mucus as a model for sinus mucin gene expression studies

Objective/Hypothesis: It is necessary to obtain sinus mucus from the paranasal sinus cavities to study mucin gene expression occurring in the sinuses during chronic sinusitis. This requires an invasive procedure to access the sinus cavity. There are embryological as well as histological similarities between nasal and sinus epithelia; therefore, we postulated that the mucin expression in the secreted nasal and sinus mucins might be similar. Nasal mucus, which can be obtained easily, could then replace sinus mucus in these studies. Study Design: Sinus and nasal mucus from six patients with chronic sinusitis were analyzed in this study. Methods. High-molecular-weight glycoproteins (mucins) were isolated and purified by sequential density gradient centrifugation in caesium chloride (CsCl). Enzyme-linked immunosorbent assay was performed to identify the antigenic identity of these mucins. Results: The MUC2, MUC5AC, and MUC5B mucin genes were all expressed in the nasal and sinus mucus secretions. Antigenic studies showed an inverse relationship between MUC2 and MUC5AC expression in nasal and sinus mucus secretions. The MUC5B gene was the major mucin gene expressed in sinus mucus but not in nasal mucus. Expression of MUC2 was significantly higher in sinus mucus. Expression of MUC5AC was different between nasal and sinus mucus. Conclusions: Individual mucin expression in sinus and nasal mucus was markedly different. From this preliminary study, we conclude that nasal mucus is not a suitable substitute for sinus mucus in sinus mucin gene studies and that different pathological processes are taking place in nasal and sinus tissue in chronic sinusitis.