Transforming growth factor beta-1 signalling in canine hepatic diseases: new models for human fibrotic liver pathologies.

Abstract: Background/aims: The purpose of this study was to validate spontaneous chronic hepatitis and cirrhosis in dogs as a potential large animal model for fibrotic liver disease in humans by evaluating their molecular pathophysiology. Methods: Transforming growth factor-β1 (TGF-β1) signalling was analysed in liver samples of dogs with acute hepatitis (AH), chronic hepatitis (CH), cirrhosis (CIRR), and a specific form of cirrhosis, lobular dissecting hepatitis (LDH), in comparison with human cirrhotic samples from alcohol abuse (ALC) and hepatitis C (HC). Results: Canine samples were investigated with quantitative real-time PCR (Q-PCR) and Western blotting on TGF-β1 signalling including Smad2/3 phosphorylation. Immunohistochemistry on collagens I and III was performed. Q-PCR showed an increase in TGF-β1 levels and downstream effector gene products in CH, LDH, and CIRR. The same fibrotic diseases also showed an increase in phosphorylated Smad2/3 and a higher deposition of collagens I and III. In contrast, in AH neither active TGF-β1 signalling nor collagen deposition was observed. Western blot analysis on human ALC and HC indicated a high similarity with canine samples in TGF-β1 expression and Smad2/3 phosphorylation. Conclusions: Our results demonstrate that fibrosis in spontaneous dog liver diseases is highly comparable to their human counterparts and might serve as models for anti-fibrotic strategies.