Molecular serum markers of liver fibrosis

Abstract

Fibrosis is a hallmark histologic event of chronic liver diseases and is characterized by the excessive accumulation and reorganization of the extracellular matrix (ECM). The gold standard for assessment of fibrosis is liver biopsy. As this procedure has various limitations, including risk of patient injury and sampling error, a non-invasive serum marker for liver fibrosis is desirable. The increasing understanding of the pathogenesis of hepatic fibrosis has suggested several markers which could be useful indicators of hepatic fibrogenesis and fibrosis. These markers include serum markers of liver function, ECM synthesis, fibrolytic processes, ECM degradation and fibrogenesis related cytokines. Recently, neo-epitopes, which are post-translational modifications of proteins, have been successfully used in bone and cartilage diseases which are characterized by extensive ECM remodeling. Increasing numbers of studies are being undertaken to identify neo-epitopes generated during liver fibrosis, and which ultimately might be useful for diagnosing and monitoring fibrogenesis. To date, the metalloproteinases generated fragment of collagen I, III, IV and VI have been proven to be elevated in two rat models of fibrosis. This review summarizes the recent efforts that have been made to identify potentially reliable non-invasive serum markers. We used the recently proposed BIPED (Burden of disease, Investigative, Prognostic, Efficacy and Diagnostic) system to characterize potential serum markers and neo-epitope markers that have been identified to date.

Keywords: extracellular matrix; liver fibrosis; neo-epitope; serum marker.

Figure 1

Mechanisms of hepatic fibrogenesis and possible molecular serum biomarkers. Some molecular serum biomarkers may reflect the pathogenesis of liver fibrosis: neo-epitopes, are related to basement membrane degradation; pro-collagen, is related to extracellular matrix (ECM) synthesis; MMPs and TIMPs are relate to ECM fibrolytic processes; ALT and AST are related to liver function and injury; other serum markers are fibrogenesis-related cytokines.