Subepithelial ALOX15+ macrophage niches orchestrate eosinophil recruitment in chronic rhinosinusitis with nasal polyps via the ALOX15-ERK-CCL13 axis

BACKGROUND: Eosinophilic chronic rhinosinusitis with nasal polyps (eCRSwNP) is characterized by intense type 2 inflammation and high recurrence rate. The precise spatial determinants and cellular mechanisms sustaining tissue eosinophilia within the polyp microenvironment remain unkown. This study aimed to identify the spatially cellular niches driving eosinophil recruitment and evaluate the therapeutic efficacy of targeting specific macrophage-driven pathogenic loops in eCRSwNP. METHODOLOGY: Transcriptomic profiles were analyzed using bulk RNA-sequencing of nasal polyp tissues from CRSwNP patients (n = 30, stratified by eosinophilic severity) and healthy controls (HC, n = 10). Spatial transcriptomics (GeoMx DSP) and single-cell RNA sequencing analyses were utilized to map macrophage niches. Mechanistic findings were validated ex vivo and in vitro using human sinonasal explant models and migration assays, incorporating an independent cohort of healthy controls (n = 12). RESULTS: Bulk transcriptomics of nasal polyps stratified across a gradient of tissue eosinophil density identified ALOX15 and CCL13 as top candidates positively correlating with tissue eosinophilia. Spatial transcriptomics revealed that subepithelial ALOX15+ macrophages served as the primary source of CCL13, and the localized CCL13 expression significantly correlated with eosinophil density in epithelial areas. Mechanistically, IL-4/IL-13 induces ALOX15-ERK-CCL13 axis in macrophages. Functional explant assays confirmed that ALOX15+ macrophages drive eosinophil recruitment via CCR3. IL-4Ra blockade with Dupilumab or Stapokibart abrogated the pathogenic ALOX15-CCL13 loop and attenuated eosinophil chemotaxis. CONCLUSIONS: Our findings identify the subepithelial ALOX15+ macrophage niche as a pivotal spatial determinant of eosinophilia in eCRSwNP. Targeting this specialized immune hub with emerging biologics offers a promising precision therapeutic strategy.