Common airborne fungi induce species-specific effects on upper airway inflammatory and remodelling responses

Objective: Whilst the exact cause of chronic rhinosinusitis (CRS) remains elusive, it is clear that both inflammation and remodelling are key disease processes. Environmental fungi have been linked to airway inflammation in CRS; however, their role in the pathogenesis of this condition remains controversial. The current consensus suggests that whilst fungi may not be directly causative, it is likely that CRS patients have deficits in their innate and potentially acquired immunity, which in turn may modify their ability to react to fungi. This study used a nasal polyp explant tissue stimulation model to study the inflammatory and remodelling responses related to challenge with common airborne fungal species. Methods: Ex vivo nasal polyp tissue from six well phenotyped CRSwNP patients undergoing functional endoscopic sinus surgery was stimulated with 1, 10 and 100 μg/ml of Alternaria alternata, Aspergillus niger, Cladosporium sphaerospermum and Penicillium notatum and compared with unchallenged polyp tissue as control. Enzyme-linked immunosorbent assay (ELISA) was used to measure the levels of pro-inflammatory cytokines interleukin-6 (IL-6), granulocyte macrophage colony stimulating factor (GM-CSF) and tumour necrosis factor-α (TNF-α); and pro-remodelling cytokines transforming growth factor-b1 (TGF-b1), and basic fibroblast growth factor (bFGF) in the polyp supernatant. Results: Aspergillus niger stimulation increased pro-inflammatory cytokines TNF-α, GM-CSF and IL-6 whilst having little effect on the remodelling cytokines bFGF and TGF-b1. In contrast, stimulation with Cladosporium sphaerospermum, Alternaria alternata and Penicillium notatum reduced pro-inflammatory cytokines TNF-α and IL-6, but induced a dose-dependent increase in remodelling cytokines TGF-b1 and bFGF. Conclusions: This study shows that common airborne fungi induce species-specific effects on the upper airway inflammatory and remodelling responses. These findings provide further immunological evidence of a disease-modifying role for fungi in CRS.