Quantitative micro-CT-derived biomarkers elucidate age-related lung fibrosis in elder mice

• Published in: Respiratory research 2024-10, Vol.25 (1), p.393-18, Article 393
• Main Authors: Buseghin, Davide, Grandi, Andrea, Ferrini, Erica, Villetti, Gino, Ciccimarra, Roberta, Sverzellati, Nicola, Aliverti, Andrea, Pennati, Francesca, Stellari, Franco Fabio
• Format: Article
• Language: English
• Subjects: Age; Age Factors; Aging - metabolism; Aging - pathology; Animal welfare; Animals; Biological markers; Biomarkers - metabolism; Bleomycin; Bleomycin - administration & dosage; Bleomycin - toxicity; Bleomycin model; Comparative analysis; CT imaging; Disease Models, Animal; Ethylenediaminetetraacetic acid; Fibrosis; Idiopathic Pulmonary Fibrosis - chemically induced; Idiopathic Pulmonary Fibrosis - diagnostic imaging; Idiopathic Pulmonary Fibrosis - drug therapy; Idiopathic Pulmonary Fibrosis - metabolism; Idiopathic Pulmonary Fibrosis - pathology; Indoles - administration & dosage; IPF; Lung - diagnostic imaging; Lung - drug effects; Lung - metabolism; Lung - pathology; Lung fibrosis; Male; Medical research; Medicine, Experimental; Mice; Mice, Inbred C57BL; Micro-computed tomography; Nintedanib; Pulmonary Fibrosis - chemically induced; Pulmonary Fibrosis - diagnostic imaging; Pulmonary Fibrosis - drug therapy; Pulmonary Fibrosis - metabolism; Pulmonary Fibrosis - pathology; Wildlife conservation; X-Ray Microtomography - methods
• ISSN: 1465-993X; 1465-9921; 1465-993X
• DOI: 10.1186/s12931-024-03006-7

Idiopathic Pulmonary Fibrosis (IPF), prevalently affecting individuals over 60 years of age, has been mainly studied in young mouse models. The limited efficacy of current treatments underscores the need for animal models that better mimic an aged patient population. We addressed this by inducing pulmonary fibrosis in aged mice, using longitudinal micro-CT imaging as primary readout, with special attention to animal welfare. A double bleomycin dose was administered to 18-24 months-old male C57Bl/6j mice to induce pulmonary fibrosis. Bleomycin dosage was reduced to as low as 75% compared to that commonly administered to young (8-12 weeks-old) mice, resulting in long-term lung fibrosis without mortality, complying with animal welfare guidelines. After fibrosis induction, animals received Nintedanib once-daily for two weeks and longitudinally monitored by micro-CT, which provided structural and functional biomarkers, followed by post-mortem histological analysis as terminal endpoint. Compared to young mice, aged animals displayed increased volume, reduced tissue density and function, and marked inflammation. This increased vulnerability imposed a bleomycin dosage reduction to the lowest tested level (2.5 µg/mouse), inducing a milder, yet persistent, fibrosis, while preserving animal welfare. Nintedanib treatment reduced fibrotic lesions and improved pulmonary function. Our data identify a downsized bleomycin treatment that allows to achieve the best trade-off between fibrosis induction and animal welfare, a requirement for antifibrotic drug testing in aged lungs. Nintedanib displayed significant efficacy in this lower-severity disease model, suggesting potential patient stratification strategies. Lung pathology was quantitatively assessed by micro-CT, pointing to the value of longitudinal endpoints in clinical trials.