Immunological profiling of key inflammatory drivers of nasal polyp formation and growth in chronic rhinosinusitis

Background: Chronic rhinosinusitis (CRS) is a chronic inflammatory condition of the upper airways, often associated with the formation of nasal polyps (CRSwNP). It is well established that macroscopically normal (non-polypoidal) sinonasal mucosa in CRSwNP patients can undergo polypoidal change over time, turning into frank polyps. However, little is known about what drives this process. This study aimed to investigate potential drivers of nasal polyp formation or growth through comparison of the immunological profiles of nasal polyps with contiguous non-polypoidal sinonasal mucosa, from the same patients. Methods: The immune profiles of three types of tissue were compared; nasal polyps and adjacent non-polypoidal sinonasal mucosa from 10 CRSwNP patients, and sinonasal mucosa from 10 control patients undergoing trans-sphenoidal pituitary surgery. Nasal polyp and control samples were also stimulated with Staphylococcus aureus enterotoxin B (SEB) using a nasal explant model, prior to cytokine analysis. Real time quantitative polymerase chain reaction (IL-5, T-bet, IL-17A, FoxP3, TLR-4, IL-8, IL-1β and IL-6) and Luminex (IFNγ, IL-5 and IL-17A) were used to quantify pro-inflammatory responses. Results: Nasal polyps and contiguous non-polypoidal sinonasal mucosa from CRSwNP patients displayed a very similar pro-inflammatory profile. When stimulated with SEB, nasal polyps displayed a Th2/Th17 mediated response when compared to controls. Conclusions: In CRSwNP, nasal polyps and non-polypoidal sinonasal mucosa from the same patient displayed a similar pro-inflammatory profile skewed towards the Th2/Th17 pathway in nasal polyps following SEB stimulation, with evidence of disordered bacterial clearance. These factors may contribute to enhanced survival of bacteria and development of a chronic inflammatory milieu, potentially driving new polyp formation and recurrence following surgical removal.