miR-133a mediates TGF-ß-dependent derepression of collagen synthesis in hepatic stellate cells during liver fibrosis.

BACKGROUND & AIMS: miRNAs are novel regulators of organ fibrosis. miR-133a plays a role in cardiac and muscle remodeling, but its function in the liver is unclear. We therefore aimed at evaluating a possible function of miR-133a in hepatofibrogenesis. METHODS: miR-133a levels were measured in whole liver samples from different murine hepatic fibrosis models and human liver tissue from patients with liver cirrhosis. The cell-specific regulation of miR-133a was assessed in FACS-sorted hepatic cell subpopulations. Murine and human primary hepatic stellate cells (HSC) were isolated and treated with different cytokines to evaluate upstream regulators of miR-133a. Moreover, GRX cells were transfected with synthetic miR-133a and the effect on extracellular matrix (ECM) gene regulation was assessed. Finally, miR-133a serum levels were measured in a cohort of patients with chronic liver diseases and correlated with disease progression. RESULTS: Overall miR-133a expression levels were unchanged in whole RNA extracts from fibrotic murine and human livers. However, miR-133a was specifically downregulated in HSC during fibrogenesis. Treatment of primary murine and human HSC with transforming growth factor (TGF)-ß resulted in a significant downregulation of miR-133a in these cells. In turn, overexpression of miR-133a in primary murine HSC led to decreased expression of collagens. In addition, miR-133a serum levels were increased in patients with chronic liver disease and indicated the presence and progression of liver cirrhosis. CONCLUSIONS: Evidence is presented for a novel antifibrotic functional role of miR-133a in hepatofibrogenesis. miR-133a may thus represent a target for diagnostic and therapeutic strategies in liver fibrosis.

Micro-RNA profiling in human serum reveals compartment-specific roles of miR-571 and miR-652 in liver cirrhosis.

BACKGROUND AND AIMS: Micro-RNAs (miRNAs) have recently emerged as crucial modulators of molecular processes involved in chronic liver diseases. The few miRNAs with previously proposed roles in liver cirrhosis were identified in screening approaches on liver parenchyma, mostly in rodent models. Therefore, in the present study we performed a systematic screening approach in order to identify miRNAs with altered levels in the serum of patients with chronic liver disease and liver cirrhosis. METHODS: We performed a systematic, array-based miRNA expression analysis on serum samples from patients with liver cirrhosis. In functional experiments we evaluated the relationship between alterations of miRNA serum levels and their role in distinct cellular compartments involved in hepatic cirrhosis. RESULTS: The array analysis and the subsequent confirmation by qPCR in a larger patient cohort identified significant alterations in serum levels of miR-513-3p, miR-571 and miR-652, three previously uncharacterized miRNAs, in patients with alcoholic or hepatitis C induced liver cirrhosis. Of these, miR-571 serum levels closely correlated with disease stages, thus revealing potential as a novel biomarker for hepatic cirrhosis. Further analysis revealed that up-regulation of miR-571 in serum reflected a concordant regulation in cirrhotic liver tissue. In isolated primary human liver cells, miR-571 was up-regulated in human hepatocytes and hepatic stellate cells in response to the pro-fibrogenic cytokine TGF-ß. In contrast, alterations in serum levels of miR-652 were stage-independent, reflecting a concordant down-regulation of this miRNA in circulating monocytes of patients with liver cirrhosis, which was inducible by proinflammatory stimuli like bacterial lipopolysaccharide. CONCLUSION: Alterations of miR571 and miR-652 serum levels in patients with chronic liver disease reflect their putative roles in the mediation of fibrogenic and inflammatory processes in distinct cellular compartments involved in the pathogenesis of liver cirrhosis.