D21-13 A Single-Cell Comparison of Diseased Ethmoid Mucosa and Nasal Polyp Tissue Reveals Presence and Expansion of TREM2+ Macrophages in Chronic Rhinosinusitis With Nasal Polyps

Rationale Chronic rhinosinusitis (CRS) is an inflammatory disorder of the upper airway that affects up to 12% of the U.S. population. Approximately 25-30% of patients with CRS have nasal polyps (CRSwNP) -- inflammatory and hyperplastic outgrowths of the sinonasal mucosa driven by type 2 inflammation and tissue remodeling. Nasal polyps are thought to arise as extensions of chronically inflamed sinonasal mucosa. However, the molecular and cellular mechanisms underlying the transition from healthy to diseased sinonasal mucosa, and ultimately to nasal polyposis, remain poorly understood. Methods 10X Genomics single-cell RNA sequencing was performed on anterior ethmoid from donors without CRS (control, n = 5), as well as anterior ethmoid (AE; n = 8) and nasal polyp (NP; n = 6) samples from patients with CRSwNP. Cell cluster types were identified, and differential gene expression analyses were conducted by comparing diseased AE and NP tissues to control. Key transcriptomic findings were further validated with histological and immunofluorescence imaging. Results After quality control, 78,359 high-quality cells were retained and classified into 17 distinct clusters representing epithelial, immune, and stromal cell populations. Gene set enrichment analysis revealed both shared and distinct pathways in AE and NP compared to control. Both AE and NP showed enhanced signaling related to type 2 inflammation (IL-4/IL-13 pathway) and tissue remodeling (VEGF and EGFR pathways). However, compared to NP tissue, AE tissue myeloid cells exclusively showed enrichment in genes regulating lipid catabolism and the presence of TREM2+ macrophages. Further analysis identified two transcriptionally distinct TREM2+ macrophage subsets (TREM2 M1 and TREM2 M2), displaying gene signatures resembling M1 (e.g., CXCL2, TNF) and M2 (e.g., MRC1, CD163) macrophages. Notably, TREM2+ M2 cells were significantly increased in AE and enriched for lipid-associated genes (e.g., APOE, APOC1, and LIPA). TREM2 expression positively correlated with transcripts regulating type 2 inflammation (IL5, IL13) and tissue remodeling (FN1, MMP9), suggesting a link between macrophage metabolic reprogramming and chronic inflammation. Finally, we validated the presence of TREM2+CD68+ macrophages in AE by immunofluorescence staining. Conclusion This study delineates two distinct states in CRSwNP pathogenesis. Although both diseased AE and NP share an enhanced type 2 inflammatory and tissue remodeling signature, AE uniquely exhibits an expanded population of TREM2+ macrophages enriched in lipid-associated transcripts. The association of TREM2 expression with type 2 cytokines and remodeling genes highlights a previously unrecognized potential link between macrophage metabolic reprogramming and chronic airway inflammation, while also identifying TREM2+ macrophages as potential biomarkers and therapeutic targets in CRSwNP. This abstract is funded by: National Institutes of Health-K08ES037417