Global analysis of DNA methylation in early-stage liver fibrosis

To address this issue, we used a pathological mouse model of early-stage liver fibrosis that was induced by treatment with carbon tetrachloride (CCl4) for 2 weeks and performed a genome-wide analysis of DNA methylation status. This global analysis of DNA methylation was performed using a combination of methyl-binding protein (MBP)-based high throughput sequencing (MBP-seq) and bioinformatic tools, IPA and Oncomine. To confirm functional aspect of MBP-seq data, we complementary used biochemical methods, such as bisulfite modification and in-vitro-methylation assays.The genome-wide analysis revealed that DNA methylation status was reduced throughout the genome because of CCl4 treatment in the early-stage liver fibrosis. Bioinformatic and biochemical analyses revealed that a gene associated with fibrosis, secreted phosphoprotein 1 (Spp1), which induces inflammation, was hypomethylated and its expression was up-regulated. These results suggest that DNA hypomethylation of the genes responsible for fibrosis may precede the onset of liver fibrosis. Moreover, Spp1 is also known to enhance tumor development. Using the web-based database, we revealed that Spp1 expression is increased in HCC.Our study suggests that hypomethylation is crucial for the onset of and in the progression of liver fibrosis to HCC. The elucidation of this change in methylation status from the onset of fibrosis and subsequent progression to HCC may lead to a new clinical diagnosis.Fibrosis is one of the most severe systemic diseases and is characterized by excessive accumulation of fibrous connective tissues, such as collagen, induced by acute or chronic injury [1]. Fibroproliferative diseases occur throughout the body, including in the lungs, kidneys, and liver. The progression of fibrosis leads to the failure of the physiological functions of tissues. Liver fibrosis, in particular, has been extensively investigated because its progression results in hepatocellular carcinoma (HCC), which is the fifth m