Interstitial pulmonary fibrosis model develpment and identification of early biomarkers by MALDI imaging

Interstitial Pulmonary Fibrosis (IPF) is a chronic and progressive disease. Fibrosis is caused by aberrant alveolar epithelial cell activation and repair leading to fibroblastic foci, accumulation of extracellular matrix and irreversible destruction of the lung. The objective of this study was to develop a rat model of fibrosis using bleomycin. Mass Spectrometry Imaging (MSI) was used to identify biomarkers in fibrotic lesions. Rats were dosed with one or seven doses of bleomycin delivered to the lungs. Control animals received vehicle. Body weights, clinical signs and respiratory parameters were monitored during the in-life phase. Lungs were fixed for histopathology (Day 21) or for mass spectrometry imaging (MALDI-FTICR) (Day 7 and Day 22). MSI was also used to confirm the distribution of bleomycin after dosing. Bleomycin caused statistically significant changes in respiratory parameters and lung weights, as well as a reduction in body weight gain; all changes were consistent with the development of fibrosis. Histopathological analysis revealed multifocal fibrosis with inflammation. The extent of all changes was greater in those animals administered seven doses of bleomycin compared with one dose. MSI identified the significant upregulation of lipids in fibrotic lesions; some identified lipids are known to be associated with IPF (molecular species of lysophosphatidic acid)(Montesi et al BMC Pulm Med.27;14 2014) while other lipids were novel (with roles in cell signalling, chemotaxis and membrane stability). In conclusion, we have identified a number of known and novel lipid biomarkers in fibrotic lesions in a characterized rat model of IPF induced by bleomycin administration.