TIM-3-Expressing Mast Cells Are Present in Chronic Rhinosinusitis with Nasal Polyps

Objectives To identify whether TIM-3 expression is present in the mast cell population within nasal polyps and to determine its correlation with clinical severity in patients with chronic rhinosinusitis with nasal polyposis. Study Design Basic science, translational study. Setting Nasal polyp tissue collected from patients seen at a tertiary care hospital (2015-2016). Subjects and Methods Nasal polyp tissue obtained during functional endoscopic sinus surgery (n = 24) was enzymatically digested into epithelial and stromal fractions. Viable mast cells expressing TIM-3 were identified using flow cytometry for the following: CD45, Live/Dead, c-kit, FcεR1, TIM-3. Disease severity was assessed using the Sino-Nasal Outcome Test, Lund-Mackay staging system, Lund-Kennedy staging system, and complete blood counts. Results Mast cells were found in both the epithelial and stromal layers of polyps, with a greater %TIM-3⁺ mast cells in the epithelial layer compared with that of the stromal layer ( P = .001). As the percentage of mast cells increased, there was a comparative worsening in endoscopic severity after comparing pre- and postoperative LK scores (ρ = -0.455, P = .029). In a subgroup of patients with concomitant asthma, increased epithelial %TIM-3⁺ mast cells also correlated with worsening endoscopic appearance postoperatively (ρ = 0.866, P = .001, n = 11). Oral corticosteroid treatment did not change the viability of mast cells nor their influence on the increased postoperative endoscopic disease severity (ρ = -0.544, P = .020, n = 18). Conclusion Viable mast cells were found to be present in polyps with increased TIM-3 expression at the epithelial layer. This suggests that TIM-3 may play a role in chronic inflammation in CRSwNP via mast cell activation.