The Role of MUC1 in Chronic Rhinosinusitis with Nasal Polyps (CRSwNP): The Correlation with Disease Severity

<b>Background:</b> Mucins, particularly MUC1, are involved in the pathogenesis of chronic respiratory diseases. In chronic rhinosinusitis with nasal polyposis (CRSwNP), altered mucin expression may contribute to chronic inflammation and tissue remodeling. However, the specific role of MUC1 in CRSwNP and its correlation with clinical severity and inflammatory pathway remains unclear. <b>Objective:</b> We aimed to evaluate the MUC-1 expression in nasal polyps of patients with CRSwNP and to assess the correlation of MUC-1 expression and disease severity, according to Clinical-Cytological Grading (CCG). <b>Methods:</b> Eighteen consecutive patients with CRSwNP who underwent endoscopic sinus surgery (ESS) were enrolled. A double-label immunofluorescence was performed to evaluate the expression of MUC-1, CD15 and Tryptase and their eventual co-localization on histological samples. Double-positive MUC-1+CD15+ and MUC-1+Tryptase+ inflammatory cells were counted by confocal microscopy. <b>Results:</b> MUC1 was expressed in all samples, with a significantly increasing expression in relation to CCG (<i>p</i> < 0.001). A significant co-localization between MUC1 and CD15+ eosinophils was observed, with a progressive increase in the number of double-positive cells from low to high CCG (<i>p</i> < 0.001). On the contrary, the co-localization between MUC1 and Tryptase+ mast cells was not significant, although both markers showed a higher expression in cases with high CCG (<i>p</i> < 0.001). <b>Conclusions:</b> A strong correlation between CRSwNP severity and MUC-1 expression, mainly colocalized with infiltrating eosinophils, was shown. This offers a promising perspective for the use of MUC-1 as a biomarker of CRSwNP.