IL-33 Expression in Chronic Rhinosinusitis with Nasal Polyps and Its Relationship with Clinical Severity

<b><i>Background:</i></b> Chronic rhinosinusitis (CRS) is a heterogeneous disease characterized by epithelial inflammation and tissue eosinophilic infiltration. Interleukin-33 (IL-33) is a key inflammatory cytokine that mediates eosinophilic infiltration. <b><i>Objective:</i></b> The aim of our study was to investigate the expression and role of IL-33 in eosinophilic CRS with nasal polyps (ECRSwNP) and in noneosinophilic CRS with nasal polyps (nECRSwNP), and to analyze their correlation with clinical severity. <b><i>Methods:</i></b> The study enrolled 25 patients with ECRSwNP, 27 patients with nECRSwNP, and 12 control subjects, based on immunohistochemical staining. Protein and mRNA expressions of IL-33 in sinus mucosal samples were determined by immunohistochemistry and real-time polymerase chain reaction. Sino-Nasal Outcome Test-20 (SNOT-20) score, visual analog scale (VAS) score, endoscopy score, and computed tomography (CT) score were assessed preoperatively. <b><i>Results:</i></b> IL-33 expression levels in the CRSwNP group were significantly higher than those in the control group (<i>p</i> < 0.01), especially in the ECRSwNP group (<i>p</i> < 0.05). There were no significant differences between the ECRSwNP and nECRSwNP groups with respect to SNOT-20 score, VAS score, endoscopy score, or CT score. IL-33 mRNA expression showed a positive correlation with the number of eosinophils (<i>p</i> < 0.05) and endoscopy score (<i>p</i> < 0.05) but not with VAS score and CT score. <b><i>Conclusion:</i></b> IL-33 expression plays an important role in patients with CRSwNP. No significant differences were observed between the ECRSwNP and nECRSwNP groups with respect to SNOT-20 score, VAS score, endoscopy score, or CT score. IL-33 expression was correlated with eosinophil counts and endoscopy score.