The longitudinal and regional analysis of bleomycin-induced pulmonary fibrosis in mice by microcomputed tomography

Introduction: Microcomputed tomography (micro-CT) is powerful for assessment of the progression of lung fibrosis in animal model, but current whole lung analysis (WLA) methods are timeconsuming. Here, a longitudinal and regional analysis (LRA) method was developed to assess fibrosis easily and quickly by micro-CT.Method: Firstly, we investigated the distribution pattern of lesions in BLM-induced pulmonary fibrosis mice. Then, the VOIs for LRA were selected based on the anatomical locations and we compared the robustness, accuracy, repeatability, analysis time of LRA to WLA. Additionally, LRA was applied to assess different stages of pulmonary fibrosis, and was validated with conventional endpoint measurements (such as lung hydroxyproline and histopathology). Results: The lesions of fibrosis in 66 bleomycin (BLM)-induced pulmonary fibrosis mice were mostly in the middle and upper parts of lungs. By applying LRA, the percentages of high-density voxels in selected volumes of interest (VOIs) were well correlated with that in WLA both at Day 7 and Day 21 after bleomycin induction (R2 = 0.8784 and 0.8464, respectively). The relative standard deviation (RSD) of the percentage of high-density voxels in the VOIs was lower than that of WLA (P < 0.05). The cost time of LRA was shorter than that of WLA (P < 0.05) and the accuracy of LRA was further confirmed by the histological analysis and biochemical quantification of hydroxyproline.Conclusion: LRA is probably an easier and more time-saving method to assess fibrosis formation and evaluate treatment efficacy.