Pathophysiological features of disease in a large animal model of COPD

Background: Chronic obstructive pulmonary disease (COPD) is a serious chronic disease of the airways that affects many people worldwide and have limited treatment options. While small animal models provide a platform for therapeutic investigations into COPD, their deficiencies continue to impede clinical translation. Alternatively, as a large animal model, sheep have a respiratory system anatomically and physiologically similar to that of humans, encouraging their use in airway disease research. The aim of this study was to better understand disease pathology in a large animal (sheep) experimental model of COPD. Methods: COPD was induced in sheep following lung exposure to porcine elastase (PE) and repeated weekly lung exposures to lipopolysaccharide (LPS) over a period of 8 weeks. Bronchoalveolar fluid and blood samples were collected for immune analyses. Lung function was assessed and lung tissues were collected for histopathology and RNA sequencing. Results: Lung neutrophil levels were elevated in response to repeated airway exposure to PE/LPS, accompanied by a significant decline in ventilation over time. Histological evidence of COPD-like disease changes included chronic inflammation with increased airway and tissue inflammation scores, together with significantly larger airway wall area measures, increased connective tissue deposition and dysregulated gene expression. Conclusions: These studies demonstrate sustained chronic airway inflammation and pathophysiological lung changes in a sheep model of COPD, providing many similarities to that seen in COPD patients. This work opens a pathway for future translational studies using this unique large animal model of COPD, which will serve to bridge the gap between smaller animal models and humans. Total RNA samples from Saline- and Porcine Elastase/LPS-exposed lung lobes sheep (n=7 in triplicate) sequenced after quality control analysis