Crosstalk between lung fibroblasts and mast cells is modified by alveolar extracellular matrix and influences epithelial migration

Abstract

<b>Background:</b> Mast cells play an important role in asthma, however, the interactions between mast cells, fibroblasts and epithelial cells in idiopathic pulmonary fibrosis (IPF) are less known. The objectives were to investigate the effect of mast cells on fibroblast activity and migration of epithelial cells. <b>Methods:</b> Primary distally-derived lung fibroblasts obtained from IPF patients and healthy individuals were cultured with LAD2 mast cells or stimulated with the mast cell proteases tryptase and chymase for 72 hours. Human lung fibroblasts and mast cells were cultured on traditional cell culture plastics or decellularized human lung tissue slices (lung scaffolds) to create a more physiological milieu by providing an alveolar extracellular matrix. Released mediators were analyzed and further evaluated for effects on epithelial cell migration. <b>Results:</b> Tryptase increased IL-6, VEGF and HGF release whereas co-culture with mast cells increased IL-6 in healthy lung fibroblasts. VEGF-C release was significantly increased in IPF fibroblasts and further induced by mast cells compared to healthy fibroblasts. Tryptase induced fibroblast migration but mast cells did not promote a myofibroblast phenotype such as altered αSMA levels. Culture in lung scaffolds increased the release of HGF and VEGF compared to culture on plastic plates. Migration of A549 epithelial cells was significantly reduced by IL-6, while HGF and conditioned media from scaffold cultures with mast cells and fibroblasts promoted migration. <b>Conclusions:</b> Mast cells and tryptase increased fibroblast release of mediators that influenced epithelial migration. These data indicate a role of mast cells in the interplay between fibroblasts, epithelial cells and the alveolar extracellular matrix in the pathogenesis of lung diseases.