Cellular comparison of sinus mucosa vs polyp tissue from a single sinus cavity in chronic rhinosinusitis

Background: Nasal polyposis is a common development in chronic rhinosinusitis (CRS), and sinus mucosa and polyp tissue have been used interchangeably in studies investigating CRS. However, potential differences may exist between these 2 tissue types, which have not been entirely characterized. Methods: A cross-sectional study of CRS with nasal polyposis (CRSwNP) patients undergoing endoscopic sinus surgery was conducted. Sinus mucosal biopsies and corresponding polyp tissue were obtained from the same sinus cavity via flow cytometry, single-cell suspensions identified type 2 innate lymphoid cells (ILC2s), CD4 and CD8 T cells, activated CD4 and CD8 T cells, plasma cells, plasmacytoid dendritic cells (pDCs), regulatory T cells, T follicular helper cells, B cells, and immunoglobulin A (IgA)⁺ and IgG⁺ B cells. Cells were measured as a percentage of CD45⁺ cells. Paired nonparametric comparisons between sinus and polyp tissue were performed. Results: Ten patients (50% female; age 48 ± 16 years) were recruited. Significantly elevated ILC2 levels were found in polyp tissue compared to sinus mucosa (0.12 [0.07 to 0.23] vs 0.07 [0.04 to 0.16], p = 0.02), as well as plasma cells (2.25 [0.84 to 3.68] vs 1.18 [0.74 to 2.41], p = 0.01); pDCs (0.15 [0.12 to 0.50[ vs 0.04 [0.02 to 0.17], p = 0.03); activated CD8 T cells (29.22 [17.60 to 41.43] vs 16.32 [10.07 to 36.16], p = 0.04) and IgG⁺ B cells (6.96 [0.06 to 11.82] vs 1.51 [0.38 to 5.13], p = 0.04). Other cell populations showed no significant differences. Conclusion: Polyps have a similar cellular composition to that of mucosa. Higher levels of ILC2s, plasma cells, pDCs, activated CD8 T cells, and IgG⁺ B cells in polyp tissue may be reflective of cell populations driving nasal polyp development. The cellular machinery of CRS is present in polyps and representative of the disease process. This pilot study strongly suggests that a larger study would provide significant insights into the relationship of sinus mucosa to pathogenesis of nasal polyps.