Indocyanine-enhanced mouse model of bleomycin-induced lung fibrosis with hallmarks of progressive emphysema.

The development of new drugs for idiopathic pulmonary fibrosis strongly relies on preclinical experimentation, which requires the continuous improvement of animal models and integration with in vivo imaging data. Here, we investigated the lung distribution of bleomycin (BLM) associated with the indocyanine green (ICG) dye by fluorescence imaging. A long-lasting lung retention (up to 21 days) was observed upon oropharyngeal aspiration (OA) of either ICG or BLM + ICG, with significantly more severe pulmonary fibrosis, accompanied by the progressive appearance of emphysema-like features, uniquely associated with the latter combination. More severe and persistent lung fibrosis, together with a progressive air space enlargement uniquely associated with the BLM + ICG group, was confirmed by longitudinal micro-computed tomography (CT) and histological analyses. Multiple inflammation and fibrosis biomarkers were found to be increased in the bronchoalveolar lavage fluid of BLM- and BLM + ICG-treated animals, but with a clear trend toward a much stronger increase in the latter group. Similarly, in vitro assays performed on macrophage and epithelial cell lines revealed a significantly more marked cytotoxicity in the case of BLM + ICG-treated mice. Also unique to this group was the synergistic upregulation of apoptotic markers both in lung sections and cell lines. Although the exact mechanism underlying the more intense lung fibrosis phenotype with emphysema-like features induced by BLM + ICG remains to be elucidated, we believe that this combination treatment, whose overall effects more closely resemble the human disease, represents a valuable alternative model for studying fibrosis development and for the identification of new antifibrotic compounds.

MFAP4: a candidate biomarker for hepatic and pulmonary fibrosis?

BACKGROUND: Several comparable mechanisms have been identified for hepatic and pulmonary fibrosis. The human microfibrillar associated glycoprotein 4 (MFAP4), produced by activated myofibroblasts, is a ubiquitous protein playing a potential role in extracellular matrix (ECM) turnover and was recently identified as biomarker for hepatic fibrosis in hepatitis C patients. The current study aimed to evaluate serum levels of MFAP4 in patients with pulmonary fibrosis in order to test its potential as biomarker in clinical practice. A further aim was to determine whether MFAP4 deficiency in mice affects the formation of pulmonary fibrosis in the bleomycin model of lung fibrosis. METHODS: 91 patients with idiopathic pulmonary fibrosis (IPF), 23 with hypersensitivity pneumonitis (HP) and 31 healthy subjects were studied. In the mouse model, C57BL/6 Mfap4+/+ and Mfap4-/- mice between 6-8 weeks of age were studied. Serum levels of MFAP4 were measured by ELISA in patients and in mice. Surfactant protein D (SP-D) and LDH were measured as comparison biomarkers in patients with pulmonary fibrosis. Morphometric assessment and the Sircol kit were used to determine the amount of collagen in the lung tissue in the mouse model. RESULTS: Serum levels of MFAP4 were not elevated in lung fibrosis - neither in the patients with IPF or HP nor in the animal model. Furthermore no significant correlations with pulmonary function tests of IPF patients could be found for MFAP4. MFAP4 levels were increased in BAL of bleomycin treated mice with pulmonary fibrosis. CONCLUSIONS: MFAP4 is not elevated in sera of patients with pulmonary fibrosis or bleomycin treated mice with pulmonary fibrosis. This may be due to different pathogenic mechanisms of liver and lung fibrogenesis. MFAP4 seems to be useful as serum biomarker for hepatic but not for lung fibrosis.