Sputum biomarkers in IPF: Evidence for raised gene expression and protein level of IGFBP-2, IL-8 and MMP-7

Abstract

BackgroundIdiopathic pulmonary fibrosis (IPF) is a rare lung disease of unknown origin leading rapidly to death. This paper addresses the issue of whether sputum induction is a suitable tool to study respiratory tract inflammation and potential biomarkers in IPF compared to COPD, a fibrosing airway wall disease.MethodsIn a cross-sectional analysis, 15 IPF patients, 32 COPD and 30 healthy subjects underwent sputum induction. Total sputum cell counts and the amount of TGF- β, IGF-1, IGF-2, IGFBP-1, IGFBP-2, IGFBP-3, IL-8, IL-13, MMP-7, MMP-9, YKL-40, TNF-α and KL-6 in sputum supernatant were analysed. We also profiled gene expression of cells in the induced sputum for TGF-β, MMP-7, YKL-40, IGFBP-2, IL-6, IL-8 and TNF-α.ResultsIPF patients, like COPD, had increased sputum absolute number of neutrophils, eosinophils, macrophages and epithelial cells compared to HS. IPF sputum supernatants had increased concentrations of IGFBP-2, IL-8, TGF-β, MMP-7, MMP-9 and KL-6 (p<0.05, p<0.0001, p<0.05, p<0.05, p<0.0001, p<0.05 respectively) when compared to healthy subjects where COPD had higher IL-6 and TNF-α levels than IPF (p<0.05 and p<0.05 respectively) and HS (p<0.0001 and p<0.001 respectively) and higher IL-8 and MMP-9 than HS (p<0.0001 and p<0.001 respectively). Conversely to IL-6 and TNF-α, MMP-7 was increased in IPF compared to COPD (p<0.05). The KL-6 and MMP-7 protein levels in sputum were inversely correlated with total lung capacity (TLC, % of predicted) in IPF patients (r = -0.73 and r = -0.53 respectively). Sputum gene expression analysis identified a significant increase for IGFBP-2, IL-6, IL-8 and MMP-7 in IPF compared to HS (p<0.05, p<0.01, p<0.05 and p<0.0001 respectively) and for IGFBP-2, YKL-40, IL-6, IL-8 and MMP-7 compared to COPD (p<0.01, p<0.01, p<0.05, p<0.01 and p<0.0001 respectively). Furthermore, gene expression of TGF-β was increased in IPF compared to COPD (p<0.001) but not to HS.ConclusionOur data show clear increase in expression and production of IGFBP-2, IL-8 and MMP-7 in sputum from patients with IPF that may contribute to the disease.

FPR-1 is an important regulator of neutrophil recruitment and a tissue-specific driver of pulmonary fibrosis

“…Neutrophil elastase-null mice are protected from bleomycin-induced pulmonary fibrosis (31) and a similar protective effect is seen in mice treated with the neutrophil elastase inhibitor sivelestat (32). Critically, the number of neutrophils and levels of the neutrophil chemoattractant IL-8 are increased in patients with IPF compared with healthy subjects (33), and neutrophilia has been shown to predict early mortality in patients with IPF (34). Taken together, these data imply a critical role for neutrophils and their secreted products in the initiation and progression of fibrosis in the lung.…”

Recapitulating idiopathic pulmonary fibrosis related alveolar epithelial dysfunction in an iPSC-derived air-liquid interface model

“…Building on previous efforts to derive alveolar epithelium from hPSCs, we aimed to develop a novel model system that allows human ATII-like differentiation from induced 6 pluripotent stem cells (iPSCs) in 2D air-liquid interface (ALI) culture. We next aimed to apply this model to studying alveolar epithelial dysfunction in IPF by exposing iPSC-derived alveolar epithelial progenitor cells to an IPF-relevant cocktail (IPF-RC), based on upregulated cytokines found in IPF patient bronchoalveolar lavage or sputum (38)(39)(40)(41)(42)(43)(44)(45)(46).…”

“…Despite this fact, many currently available in vitro models of pulmonary fibrosis rely on a single stimulus (59). To mimic a profibrotic milieu in vitro, we designed a novel cocktail (IPF-RC) containing nine IPF-relevant cytokines and assessed its effect on differentiating iPSC-derived distal lung epithelial progenitor cells (38)(39)(40)(41)(42)(43)(44)(45)(46). As we primarily aimed to investigate the effect of a fibrosis-relevant environment on progenitors of the alveolar epithelium, IPF-RC stimulation was initiated by day 35 of the protocol, following induction of SFTPC expression, which constitutes a specific feature of alveolar epithelial progenitors in fetal human lungs (60)(61)(62).…”

Therapeutic Targeting of 15-PGDH in Murine Idiopathic Pulmonary Fibrosis

“…Although anti-inflammatory therapies have provided little benefit in IPF trials 5 , studies suggest that immune responses are involved in disease development and progression 6 . Indeed, neutrophils accumulate in IPF patient lungs 7-9 , and neutralizing neutrophil-derived products mitigates murine IPF severity 10,11 . Monocyte-derived alveolar macrophages are also implicated in human IPF 12 .…”