Tryptase+ mast cells associate with fibrotic regions in the lungs of idiopathic pulmonary fibrosis patients; a multiplex staining approach

Abstract

Background: Idiopathic pulmonary fibrosis (IPF) is a chronic fibrotic lung disease characterised by a progressive decline in lung function and a mean survival of 3 years post-diagnosis. Several studies have documented the presence of mast cells (MC) in the lungs of IPF patients, but despite this association the role MC play in the fibrotic process remains undefined. This study aimed to characterize specific MC phenotypes including chymase+ (MC C ), tryptase+ (MC T ) and chymase/tryptase+ cells (MC TC ) in IPF lung. Methods: Lung biopsy specimens from IPF patients (n=17) and normal individuals (n=20) obtained from Papworth Hospital underwent dual IHC staining for chymase and tryptase. Samples were analysed using image software analysis algorithm (Indica Labs HALO O software) to quantify the MC density per area (mm 2 ) in both IPF and normal lung tissue, and within annotated fibrotic and non-fibrotic areas. Results: MC C and MC T were significantly increased in the IPF lung (11.24±2.41 and 100.3±19.36/mm 2 ) compared to controls (2.25±0.73 and 24.9±4.98/mm 2 respectively; p T increased in both non-fibrotic (p=0.03) and fibrotic areas in IPF samples compared to the same regions in normal controls, whereas no difference was observed for MC C or MC T C . Conclusions: These data demonstrate that MC C , MC T and MC TC are significantly increased in IPF lung compared to normal controls and are associated mainly with fibrotic regions. Furthermore, multiplex IHC combined with image analysis are important technological tools to enable detailed quantification and interpretation of specific cell populations involved in IPF.