A Mouse Model of Respiratory Bronchiolitis-Associated Interstitial Lung Disease (RB-ILD)

Rationale. Available evidence suggests that some subsets of interstitial lung diseases, namely desquamative interstitial pneumonia, respiratory bronchiolitis-associated interstitial pneumonia (RB-ILD), and pulmonary Langerhans cell histiocytosis, are caused by cigarette smoke (CS) in susceptible individuals. Despite smoke-related interstitial lung diseases (SRILDs) have been subjected to extensive investigation during the last years, very little is known about the mechanisms involved in the pathogenesis of these diseases and why only a susceptible minority of tobacco smokers develop a clinically significant disease. Recent data suggest that genetic factors may modulate each individual’s risk. Methods. We recently observed that the combination of chronic CS exposure with targeted mutation of the p66Shc gene that is involved in the modulation of antioxidant genes, results in the development of RB-ILD. Results and Conclusions. The p66Shc knock out mouse develops after CS exposure patchy lung changes with a bronchiolocentric distribution characterized by pigmented macrophages within bronchiolar lumina, peribronchiolar fibrosis and epithelial hyperplasia. Pigmented macrophages contain finely granular brown cytoplasmic particles and are also present within alveolar ducts and peribronchiolar alveolar spaces. Chronic bronchiolitis accompanies the intraluminal macrophages and peribronchiolar infiltrates of lymphocytes and histiocytes. Mild peribronchiolar fibrosis expands contiguous alveolar septa, which are frequently lined by hyperplasic type 2 pneumocytes. In this RB-ILD model, honeycomb change does not occur, and only in some well-defined areas mild foci of emphysema are visible. Conclusions. Further studies on this unique animal model can provide valuable information on both the pathogenesis and the evolution of the lung changes characterising RB-ILD.