Quantitative Micro-CT Analysis of Lung Parenchymal and Airway Remodeling in a Ferret Model of Pulmonary Fibrosis

Pulmonary fibrosis (PF) is a chronic and progressive lung disease characterized by repetitive alveolar injury leading to parenchymal thickening, scarring, and respiratory impairment. Current rodent models, particularly those utilizing bleomycin (BLEO), have limited translational relevance to human idiopathic pulmonary fibrosis (IPF) due to anatomical differences such as the absence of respiratory bronchioles. To address this limitation, we developed a large-animal model of pulmonary fibrosis in ferrets, which possess respiratory bronchioles similar to those in humans. Three-month-old wild-type ferrets received intratracheal instillation of BLEO. Lungs were harvested 8 weeks post-treatment for micro-computed tomography (micro-CT) and histological evaluation. Owing to the limited spatial resolution of multidetector CT (MDCT) in visualizing the ferret small airways, excised lungs were imaged ex vivo using a micro-CT scanner at controlled airway pressures (0 cmH2O and 25 cmH2O) to simulate expiratory and inspiratory conditions. Micro-CT imaging revealed distinct structural differences between normal and BLEO-treated ferret lungs. Normal lungs displayed low attenuation and preserved architecture, whereas BLEO-treated lungs showed markedly increased attenuation consistent with fibrosis. Features characteristic of human fibrotic lung disease, including honeycombing with cystic spaces, thickened interlobular septa, and ground-glass opacities indicative of early fibrotic or inflammatory changes, were evident. Using quantitative micro-CT analysis, it was observed that airways in BLEO-treated ferret lungs exhibited significantly reduced radial expansion, longitudinal stretching, and volume change at both applied air pressures. Furthermore, generation-matched analysis revealed significant thickening of airway walls in regions with visually apparent fibrosis. Histological assessment, including Masson's trichrome staining, confirmed extensive collagen deposition and fibrosis. This study demonstrates that BLEO-treated ferrets develop radiologic, mechanical, and histopathologic features resembling human pulmonary fibrosis. Furthermore, micro-CT enables high-resolution assessment of fibrotic distribution, airway dynamics, and lung volume changes. These findings highlight the potential of the ferret as a translational model for studying PF pathogenesis and evaluating novel therapeutic strategies.