Hepatitis C virus-replicating hepatocytes induce fibrogenic activation of hepatic stellate cells

Area of Science:

• Hepatology
• Virology
• Molecular Biology

Background:

• The mechanism of hepatitis C virus (HCV)-induced liver fibrosis is not fully understood.
• HCV nonstructural genes (NS3-NS5B) are implicated in liver damage.
• Hepatic stellate cells are key effectors in liver fibrogenesis.

Purpose of the Study:

• To characterize the profibrogenic potential of HCV.
• To investigate the role of HCV nonstructural genes in activating hepatic stellate cells.
• To identify factors released by HCV-replicating cells that promote fibrosis.

Main Methods:

• Utilized a Huh-7 5-15 cell line stably expressing HCV nonstructural genes (NS3-NS5B).
• Incubated rat and human hepatic stellate cells with conditioned media from HCV replicon cells.
• Quantified fibrosis-related gene expression using real-time PCR, protein assays, and functional assays; measured TGF-β1 activity via bioassay.

Main Results:

• HCV replicon cells release factors that promote liver fibrosis by up-regulating collagen genes (procollagen alpha1(I) and procollagen alpha1(III)) and down-regulating matrix metalloproteinases in hepatic stellate cells.
• Transforming growth factor beta1 (TGF-β1) expression and bioactivity were significantly increased in HCV-replicating cells.
• TGF-β1 accounted for only 50% of the observed profibrogenic activity, indicating other HCV-induced factors are involved.

Conclusions:

• HCV nonstructural genes induce increased expression of TGF-β1 and other profibrogenic factors in infected hepatocytes.
• Direct induction of profibrogenic mediators by HCV in hepatocytes explains progressive liver fibrosis.
• These findings suggest novel therapeutic targets for antifibrotic strategies in chronic hepatitis C.