Pyridinoline collagen cross-links in patients with chronic viral hepatitis and cirrhosis

Background/Aims: The mature form of collagen cross-linking increases the resistance of collagen to degradative enzymes, and thus renders the protein in the fibrotic lesions extremely stable and the fibrosis virtually irreversible. It is crucial to elucidate the extent of cross-linking in fibrotic and cirrhotic livers if we are to control the subsequent removal of the excessive deposited collagen, whether by natural enzymes or induced by therapy. We aimed to quantitative pyridinoline, a mature form of the cross-linking, in normal control livers, viral fibrotic livers with various degrees of fibrosis and viral cirrhotic livers. Methods: Needle liver biopsy samples from 75 patients with chronic viral hepatitis and 13 patients with viral liver cirrhosis, and six normal control livers were analyzed. Collagen and pyridinoline contents were determined by high-performance liquid chromatography. Results: Significantly higher levels of pyridinoline cross-links per collagen molecule were found in the viral cirrhotic livers (0.60 [0.46, 0.65] pmol/pmol of collagen; median [25%, 75%]) compared with those in normal livers (0.39 [0.24, 0.43] pmol/pmol of collagen, p =0.03491). But no differences were found in levels between cirrhosis and chronic hepatits with various degrees of fibrosis. These data suggest that liver collagen may be susceptible to degradation to a similar degree in viral cirrhosis and in chronic viral hepatitis. Conclusion: The extent of the pyridinoline cross-linking of hepatic collagen does not seem to be responsible for the irreversibility of viral liver fibrosis.