Objective: FAS-mediated apoptosis of hepatocytes and aberrant TGF-β signaling are major drivers of liver fibrosis. Decreased miRNA let-7 expression in the livers of patients and animals with fibrosis suggests a mechanistic link of let-7 to hepatic fibrogenesis.
Methods: Using transient transfection we tested the effects of let-7 overexpression and TET3 siRNA knockdown on FAS and TGF-β1 expression and FAS-mediated apoptosis in human and mouse primary hepatocytes. We assessed the therapeutic activity of let-7 miRNA delivered via adeno-associated viral vectors in mouse models of carbon tetrachloride (CCl4)-induced and bile duct ligation (BDL)-induced liver fibrosis.
Results: Let-7 decreased TGF-β1 production from hepatocytes through a negative feedback loop involving TET3. On the other hand, let-7 post-transcriptionally inhibits FAS expression, thereby suppressing hepatocyte apoptosis. Hepatic-specific delivery of let-7 miRNA mitigated liver fibrosis in both CCl4 and BDL mouse models.
Conclusions: Let-7 is a crucial node in the signaling networks that govern liver fibrosis progression. Let-7 and/or its derivatives may be used as therapeutic agents for liver fibrosis.
Keywords: AAV; Apoptosis; Fibrosis; Gene therapy; Let-7; Liver; miRNA.
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