Structural and functional correlations in a large animal model of bleomycin-induced pulmonary fibrosis

Abstract

BackgroundIdiopathic pulmonary fibrosis (IPF) is a severe and progressive respiratory disease with poor prognosis. Despite the positive outcomes from recent clinical trials, there is still no cure for this disease. Pre-clinical animal models are currently largely limited to small animals which have a number of shortcomings. We have previously shown that fibrosis is induced in isolated sheep lung segments 14 days after bleomycin treatment. This study aimed to determine whether bleomycin-induced fibrosis and associated functional changes persisted over a seven-week period.MethodsTwo separate lung segments in nine sheep received two challenges two weeks apart of either, 3U bleomycin (BLM), or saline (control). Lung function in these segments was assessed by a wedged-bronchoscope procedure after bleomycin treatment. Lung tissue, and an ex vivo CT analysis were used to assess for the persistence of inflammation, fibrosis and collagen content in this model.ResultsFibrotic changes persisted up to seven weeks in bleomycin-treated isolated lung segments (Pathology scores: bleomycin12.27 ± 0.07 vs. saline 4.90 ± 1.18, n = 9, p = 0.0003). Localization of bleomycin-induced injury and increased tissue density was confirmed by CT analysis (mean densitometric CT value: bleomycin −698 ± 2.95 Hounsfield units vs. saline −898 ± 2.5 Hounsfield units, p = 0.02). Masson’s trichrome staining revealed increased connective tissue in bleomycin segments, compared to controls (% blue staining/total field area: 8.5 ± 0.8 vs. 2.1 ± 0.2 %, n = 9, p < 0.0001). bleomycin-treated segments were significantly less compliant from baseline at 7 weeks post treatment compared to control-treated segments (2.05 ± 0.88 vs. 4.97 ± 0.79 mL/cmH20, n = 9, p = 0.002). There was also a direct negative correlation between pathology scores and segmental compliance.ConclusionsWe show that there is a correlation between fibrosis and correspondingly poor lung function which persist for up to seven weeks after bleomycin treatment in this large animal model of pulmonary fibrosis.

An Official American Thoracic Society Workshop Report: Use of Animal Models for the Preclinical Assessment of Potential Therapies for Pulmonary Fibrosis

“…Comparative anatomy of the domesticated pig and ferret more closely resemble humans than do mice (10,11), and both have been used to model cystic fibrosis (12)(13)(14), but neither to study IPF. Australian sheep develop fibrosis in response to bleomycin (15), whereas other animals develop spontaneous lung fibrosis, including horses (16,17), donkeys (18), cats (19), and West Highland white terriers (20). Horses develop fibrosis after experimental gherpesvirus infection (21), but none of the other animals have been proven as tractable models of experimental fibrosis.…”

Inhibition of the KCa3.1 Channel Alleviates Established Pulmonary Fibrosis in a Large Animal Model

“…Both epithelial cells and fibroblasts play critical roles in the regulation of injury and repair in the lung, and both have been shown to be key drivers in the fibrotic process of IPF (6,7). Both of these cell types rely on Ca 21 signaling for the regulation of many critical cellular functions (8). Ca 21 -activated K 1 channels are one of the major mechanisms regulating the influx of external Ca 21 , which can be controlled through a variety of stimuli (8).…”

“…Both of these cell types rely on Ca 21 signaling for the regulation of many critical cellular functions (8). Ca 21 -activated K 1 channels are one of the major mechanisms regulating the influx of external Ca 21 , which can be controlled through a variety of stimuli (8). Ca 21 -activated K 1 channels open in response to increases in cytoplasmic Ca 21 ion concentrations, therefore maintaining a negative membrane potential and promoting further Ca 21 influx.…”

Small Ruminant Lentiviruses in Sheep: Pathology and Tropism of 2 Strains Using the Bone Marrow Route

“…26,36,38 The perivascular fibrosis observed in lungs, a finding not often described in sheep, could be associated with the chronic pulmonary disease 1 caused by experimental infection with these SRLV strains. 21,34 For both infected groups, the severity of lesions in target organs seemed to increase over time. Finally, the lack of cross-infection between infected groups and the negative ELISA and PCR results obtained in the control group proved the appropriateness of the sanitary measures taken in this work.…”