Aggregated eosinophils characterize airway mucus properties

Uncontrolled airway mucus is associated with diverse diseases. We hypothesized that the physical characteristics of infiltrating granulocytes themselves affect the clinical properties of mucus. Surgically obtained nasal mucus from patients with eosinophilic chronic rhinosinusitis (ECRS) and neutrophil-dominant non-eosinophilic chronic rhinosinusitis (non-ECRS) was assessed in terms of computed tomography (CT) density, viscosity, water content, wettability, and granulocyte-specific proteins. In an observational study, we found that nasal mucus from patients with ECRS had significantly higher CT density, viscosity, dry weight, and hydrophobicity than mucus from patients with non-ECRS. The levels of eosinophil-specific proteins in nasal mucus correlated with its physical properties. When isolated human eosinophils and neutrophils were stimulated to induce extracellular traps followed by aggregate formation, we found that cell aggregates showed physical and pathological findings that closely resembled mucus. Co-treatment with heparin (which slenderizes the structure of eosinophil extracellular traps) and DNase efficiently induced a reduction in the viscosity and hydrophobicity of both eosinophil aggregates and eosinophilic mucus. The present study highlights the pathogenesis of mucus stasis in infiltrated granulocyte aggregates from a new perspective. The combination of DNase and heparin might be a novel therapeutic modality against pathologic viscous eosinophilic mucus. One Sentence Summary Intraluminal accumulation and activation of eosinophils contribute to the clinical properties of airway mucus and may serve as a therapeutic target.