Augmenter of liver regeneration enhances cell proliferation through the microRNA-26a/Akt/cyclin D1 pathway in hepatic cells.

AIM: Hepatocytes can proliferate and regenerate when injured by toxins, viral infections, and so on. Augmenter of liver regeneration (ALR) is a key regulator of liver regeneration, but the mechanism is unknown. The role of ALR in other cell types is not known. In the present study, we investigated the relationship between microRNA (miRNA)-26a and ALR in the Huh7 cell line and adipose tissue-derived mesenchymal cells from chronic liver disease patients and healthy individuals. METHODS: Huh7 cells were transfected independently with ALR and miRNA-26a expression vectors, and their effects on cell proliferation, the expression of miRNA-26a, and activation of the phosphatase and tensin homolog and Akt signaling pathways were determined. The experiments were repeated on mesenchymal stem cells derived from healthy individuals and chronic liver disease patients to see whether the observations can be replicated in primary cells. RESULTS: Overexpression of ALR or miRNA-26a resulted in an increase of the phosphorylation of Akt and cyclin D1 expression, whereas it resulted in decreased levels of p-GSK-3ß and phosphatase and tensin homolog in Huh7 cells. The inhibition of ALR expression by ALR siRNA or anti-miR-26a decreased the Akt/cyclin D1 signaling pathway, leading to decreased proliferation. Mesenchymal stem cells isolated from the chronic liver disease patients had a higher ALR expression, while the mesenchymal stem cells isolated from healthy volunteers responded to the growth factor treatments for increased ALR expression. It was found that there was a significant increase in miRNA-26a expression and proliferation. CONCLUSIONS: These data clearly showed that ALR induced the expression of miRNA-26a, which downregulated phosphatase and tensin homolog, resulting in an increased p-Akt/cyclin D1 pathway and enhanced proliferation in hepatic cells.

Characterization of liver specific promoters in a foamy viral vector pMD09.

Foamy viruses (FVs) or spumaviruses are retroviruses that are explored as vectors for gene therapy. The good feature of foamy viruses is its broad tropism; however, their infections result in non-targeted gene expression. Here, we attempted to design the liver targeted viral gene delivery by employing liver specific gene promoters like albumin (ALB), transthyretin (TTR) and hepatitis B virus (HBV) promoters. We compared the relative gene expression of liver specific promoters versus the U3 promoter in liver cell line (HepG2) and non-liver cell lines: human fibrosarcoma cell line (HT1080), baby hamster kidney cell line (BHK), human embryonic kidney cell line (HEK 293T) and cervical cancer cell line (HeLa). We have found that the promoter exchange didn't affect viral assembly. The ability to drive gene expression was best with TTR promoter which was followed by HBV and ALB promoter. The use of TTR, HBV and ALB promoters are helpful in achieving liver specific gene expression. Keywords: foamy virus; gene therapy; liver; albumin; transthyretin promoter; HBV promoter.

Nonalcoholic fatty liver disease: the concept and confusion.

Nonalcoholic fatty liver disease (NAFLD) is generally considered as a disease associated with diabetes mellitus type 2. But on a closer evaluation we realize a host of confusion associated with this from the nomenclature, diagnosis to pathogenesis. The term refers to a spectrum ranging from steatosis to steatosis with inflammation (NASH) to cirrhosis in the absence of alcohol abuse. But in fact NAFLD is a vague term for a spectrum of diseases which differ not only in the clinical presentation but also in the etiology. NAFLD is loose to incorporate so many etiologies excluding alcoholism and few other "known" etiologies, presenting as fat in liver. Considering the diverse etiologies there is a need for personalized management in NAFLD, which at present is difficult. Currently fatty liver disease could be considered as an added Hepato-cardiovascular-renal and cancer risk factor rather than a specific diagnosis.

TGF-ß induces liver fibrosis via miRNA-181a-mediated down regulation of augmenter of liver regeneration in hepatic stellate cells.

OBJECTIVE: To study the role of miRNA-181a and augmenter of liver regeneration in TGF-ß-induced fibrosis in hepatic stellate cells. METHODS: LX2 cells were treated with 20 ng/ml TGF-ß for 24 h. miRNA-181a, ALR plasmid and empty vectors were transfected using siPORT NeoFx reagent. Cells were harvested after 48 h or 72 h of transfection for protein or RNA analysis. Western blotting was performed for ALR, TGF-ß receptor II (TGFß-RII), collagen 1A1 (COLL1A1), alpha-smooth muscle cell actin (α-SMA), rac1, E-cadherin and ß-actin. Quantitative RT-PCR was performed for ALR, GAPDH, miRNA-181a or 5S rRNA. RESULTS: TGF-ß induced the expression of miRNA-181a, which in turn down-regulated ALR thereby induced the fibrosis markers, such as COLL1A1, α-SMA and rac1 in hepatic stellate cells. Over-expression of miRNA-181a down-regulated expression of ALR and up-regulated expression of fibrosis markers. On the other hand, ALR over-expression resulted in a decrease in miRNA-181a expression and fibrosis markers. Over-expression of ALR also inhibited the expression of TGFß-RII and increased expression E-cadherin. CONCLUSION: TGF-ß induced miRNA-181a, which in turn induced fibrosis, at least in part, by inhibiting ALR. ALR inhibited TGF-ß action by decreasing the expression of TGFß-RII, thereby inhibiting miRNA-181a expression and fibrosis markers. ALR could serve as a potential molecule to inhibit liver fibrosis.