Background: Hepatitis C virus (HCV) induced liver disease is the leading indication for liver transplantation (LTx). Reinfection of HCV is a universal phenomenon, and accelerated development of fibrosis following LTx is a major concern following LTx of a HCV+ recipient. The molecular events that lead to fibrosis following HCV infection still remains poorly defined.

Methods: miRNA and mRNA expression profiles in the livers from chronic HCV (8) and normal (8) were performed using microarrays. Using the Genego software and pathway finder analysis software we performed an interactive analysis to identify the target genes that are modulated by miRNAs. Regulation of gene expression by miRNA was analyzed by in vitro transfection of human primary liver fibroblasts.

Results: 22 miRNAs were up regulated (>2 fold) and 35 miRNAs were down regulated (>2fold) in the liver of HCV patients compared to controls. Chronic HCV patients had increases in the expression of 306 genes (>3 fold) and reduction in the expression of 133 genes (>3 fold). Combinatorial analysis of the networks modulated by the miRNAs identified regulation of the phospholipase C pathway (miR200c, miR20b, and miR31through cSrc), response to growth factors and hormones (miR141, miR107 and miR200c through PPARalpha and ERK), and regulation of cellular proliferation (miR20b, miR10b, and miR141 through p21). Real time PCR validation of the miRNA levels in the chronic HCV infected liver demonstrated a 3.3 ±0.9 fold increase in the levels of miR 200c in the chronic HCV infected liver compared to the normal. In vitro transfection of fibroblasts with miR200c resulted in a 2.2 fold reduction in the expression of FAP-1 and 2.3 fold increase in the expression of cSrc. miR200c transfection also resulted in significant increases in expression of collagen and FGF (2.8 and 3.4 fold, p<0.05).

Conclusion: Chronic HCV infection results in the increased expression of miR200c which down modulates the expression of FAP1, a critical regulator of Src and MAP kinase pathway that is crucial in the production of fibrogenic growth factors and development of fibrosis. We also demonstrated that blocking of the miR200c function can result in increased levels of FAP1 leading to decreased FGF, collagen deposition and development of fibrosis.

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