A mouse model of progressive lung fibrosis with cutaneous involvement induced by a combination of oropharyngeal and osmotic minipump bleomycin delivery

• Published in: American journal of physiology. Lung cellular and molecular physiology Vol. 326; no. 6; pp. L736 - L753
• Main Authors: Grandi, Andrea, Ferrini, Erica, Zoboli, Matteo, Buseghin, Davide, Pennati, Francesca, Khalajzeyqami, Zahra, Ciccimarra, Roberta, Villetti, Gino, Stellari, Franco Fabio
• Format: Journal Article
• Language: English
• Published: United States American Physiological Society 01.06.2024
• Subjects: Animal models; Animals; Biomarkers; Bleomycin; Bleomycin - administration & dosage; Bleomycin - toxicity; Computed tomography; Disease Models, Animal; Drug therapy; Female; Fibrosis; Histology; Hypodermis; Immunofluorescence; Lung - diagnostic imaging; Lung - drug effects; Lung - pathology; Lung diseases; Lung Diseases, Interstitial - chemically induced; Lung Diseases, Interstitial - diagnostic imaging; Lung Diseases, Interstitial - drug therapy; Lung Diseases, Interstitial - pathology; Medical imaging; Methods and Resources; Mice; Mice, Inbred C57BL; Oropharynx - diagnostic imaging; Oropharynx - drug effects; Oropharynx - pathology; Pulmonary Fibrosis - chemically induced; Pulmonary Fibrosis - drug therapy; Pulmonary Fibrosis - pathology; Scleroderma, Systemic - complications; Scleroderma, Systemic - drug therapy; Scleroderma, Systemic - pathology; Skin - drug effects; Skin - pathology; Systemic sclerosis; Thickness; Time dependence; X-Ray Microtomography; micro-CT imaging; bleomycin; osmotic mini-pump; systemic sclerosis; interstitial lung disease
• ISSN: 1040-0605; 1522-1504; 1522-1504
• DOI: 10.1152/ajplung.00408.2023

Systemic sclerosis (SSc) with interstitial lung disease (SSc-ILD) lacks curative pharmacological treatments, thus necessitating effective animal models for candidate drug discovery. Existing bleomycin (BLM)-induced SSc-ILD mouse models feature spatially limited pulmonary fibrosis, spontaneously resolving after 28 days. Here, we present an alternative BLM administration approach in female C57BL/6 mice, combining oropharyngeal aspiration (OA) and subcutaneous mini-pump delivery (pump) of BLM to induce a sustained and more persistent fibrosis, while retaining stable skin fibrosis. A dose-finding study was performed with BLM administered as 10 µg (OA) +80 mg/kg (pump) (10 + 80), 10 + 100, and 15 + 100. Forty-two days after OA, micro-computed tomography (micro-CT) imaging and histomorphometric analyses showed that the 10 + 100 and 15 + 100 treatments induced significant alterations in lung micro-CT-derived readouts, Ashcroft score, and more severe fibrosis grades compared with saline controls. In addition, a marked reduction in hypodermal thickness was observed in the 15 + 100 group. A time-course characterization of the BLM 15 + 100 treatment at , , and , including longitudinal micro-CT imaging, revealed progressing alterations in lung parameters. Lung histology highlighted a sustained fibrosis accompanied by a reduction in hypodermis thickness throughout the explored time-window, with a time-dependent increase in fibrotic biomarkers detected by immunofluorescence analysis. BLM-induced alterations were partly mitigated by Nintedanib treatment. Our optimized BLM delivery approach leads to extensive and persistent lung fibrotic lesions coupled with cutaneous fibrotic alterations: it thus represents a significant advance compared with current preclinical models of BLM-induced SSc-ILD. This study introduces an innovative approach to enhance the overall performance of the mouse bleomycin (BLM)-induced model for systemic sclerosis with interstitial lung disease (SSc-ILD). By combining oropharyngeal aspiration and subcutaneous mini-pump delivery of BLM, our improved model leads to sustained lung fibrosis and stable skin fibrosis in female C57BL/6 mice. The optimized 15 + 100 treatment results in extensive and persistent lung fibrotic lesions and thus represents a significant improvement over existing preclinical models of BLM-induced SSc-ILD.