Increased survival and exocytosis of toxic primary granules by neutrophils in an in vitro model of Cystic Fibrosis airway disease (INC6P.310)

Abstract

Abstract Cystic Fibrosis (CF) lung disease is characterized by the massive recruitment of neutrophils (PMNs) into the bronchiolar lumen. Extracellular neutrophil elastase (NE) that is released from PMN primary granules, is a strong predictor of lung function and survival in CF patients. However, the process by which CF airway PMNs exocytose HNE is not well understood and not reproduced in animal models of CF airway disease. Methods: We used a surface collagen-coated 3D porous polystyrene scaffold (Alvetex) to mimic the airway lamina propria and grew human bronchiolar H441 cells at air-liquid interface on top. In the transepithelial migration assay, blood PMNs were placed on the basal side and allowed to migrate towards to CF airway fluid placed apically, after which PMNs were analyzed by flow cytometry for rate of migration, survival, and degranulation. Results: Using this model we show that (i) CF airway fluid induces rapid transepithelial migration and survival of neutrophils, (ii) live PMNs actively release of primary granules upon exposure to CF airway fluid, and (iii) migration towards CF airway fluid induces PMN reprogramming allowing for the activation of the inflammasome and pinocytosis. Conclusions: These results suggest a primary role for the CF microenviroment in inducing increased survival and phenotypic reprogramming of PMNs and establish our model as a robust platform for deconstructing CF airway PMN dysfunction and developing new therapies for CF inflammation.