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.

We sought to investigate the role of ALOX15⁺ M2 macrophages in the epithelial remodeling of eCRSwNP.

Digital spatial transcriptomics and single-cell sequencing analyses were used to characterize the epithelial remodeling and cellular infiltrate in eCRSwNP. Hematoxylin and eosin staining, immunohistochemical staining, and immunofluorescence staining were used to explore the relationship between ALOX15⁺ M2 (CD68⁺CD163⁺) macrophages and epithelial remodeling. A coculture system of primary human nasal epithelial cells (hNECs) and the macrophage cell line THP-1 was used to determine the underlying mechanisms.

Spatial transcriptomics analysis showed the upregulation of epithelial remodeling–related genes, such as Vimentin and matrix metalloproteinase 10, 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 that ALOX15⁺, rather than ALOX15⁻, M2 macrophages were specifically highly expressed in eCRSwNP. CRSwNP with high ALOX15⁺ M2^{THP-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⁺ M2^{THP-1-IL-4+IL-13} macrophages. IL-4/IL-13–polarized M2^{THP-1-IL-4+IL-13} macrophages upregulated expressions of EMT-related genes in hNECs, including Vimentin, TWIST1, Snail, and ZEB1. ALOX15 inhibition in M2^{THP-1-IL-4+IL-13} macrophages resulted in reduction of the EMT-related transcripts in hNECs. Blocking chemokine (C-C motif) ligand 13 signaling inhibited M2^{THP-1-IL-4+IL-13} macrophage–induced EMT alteration in hNECs.

ALOX15⁺ M2 macrophages are specifically increased in eCRSwNP and may contribute to the pathogenesis of epithelial remodeling via production of chemokine (C-C motif) ligand 13.