ALOX15+ M2 macrophages contribute to epithelial remodeling in eosinophilic chronic rhinosinusitis with nasal polyps

Background Epithelial remodeling is a prominent feature of eosinophilic chronic rhinosinusitis with nasal polyps (eCRSwNP), and infiltration of M2 macrophages plays a pivotal role in the pathogenesis of eCRSwNP, but the underlying mechanisms remain undefined. Objective We aimed to investigate the role of ALOX15+ M2 macrophages in the epithelial remodeling of eCRSwNP. Methods Digital spatial transcriptome and single-cell sequencing analyses were used to characterize the epithelial remodeling and cellular infiltrate in eCRSwNP. Hematoxylin and eosin staining, immunohistochemical and immunofluorescent staining were used to explore the relationship between ALOX15+ M2 (CD68+CD163+) macrophages and epithelial remodeling. A co-culture system of primary human nasal epithelial cells (hNECs) and the macrophage cell line THP-1 was used to determine the underlying mechanisms. Results Spatial transcriptomics analysis showed that upregulation of epithelial remodeling-related genes, such as VIM and MMP10, and enrichment of epithelial-mesenchymal transition (EMT)-related pathways, in the epithelial areas in eCRSwNP, with more abundance of epithelial basal, goblet and glandular cells. Single-cell analysis identified ALOX15+, rather ALOX15-, M2 macrophages were specifically highly expressed in eCRSwNP. CRSwNP with high ALOX15+ M2THP-1-IL-4+IL-13 macrophages had more obvious epithelial remodeling features and increased genes associated with epithelial remodeling and integrity of epithelial morphology versus that with low ALOX15+ M2THP-1-IL-4+IL-13 macrophages. IL-4/13-polarized M2THP-1-IL-4+IL-13 macrophages upregulated expressions of EMT-related genes in hNECs, including VIM, TWIST1, Snail, and ZEB1. ALOX15 inhibition in M2THP-1-IL-4+IL-13 macrophages resulted in reduction of the EMT-related transcripts in hNECs. Blocking CCL13 signaling inhibited M2THP-1-IL-4+IL-13 macrophage-induced EMT alteration in hNECs. Conclusion ALOX15+ M2 macrophages are specifically increased in eCRSwNP and may contribute to the pathogenesis of epithelial remodeling via production of CCL13.