Adenoviral expression of a transforming growth factor-beta1 antisense mRNA is effective in preventing liver fibrosis in bile-duct ligated rats

Transforming growth factor-beta (TGF-beta) is a key mediator in establishing liver fibrosis. Therefore, TGF-beta as a causative agent may serve as a primary target for antifibrotic gene therapy approaches. We have previously shown that the adenoviral delivery of a transgene constitutively expressing a TGF-beta1 antisense mRNA blocks TGF-beta synthesis in culture-activated hepatic stellate cells and effectively abolishes ongoing fibrogenesis in vitro. Ligature of the common bile duct was used to induce liver fibrosis in rats. The effect of the TGF-beta1 antisense on fibrogenesis was analyzed in this model of liver injury. In the present study, we demonstrate that the adenoviral vector directs the synthesis of mRNA quantities that are approximately 8000-fold more abundant than endogenous TGF-beta1 mRNA. In experimentally injured rat livers induced by ligature of the common bile duct, a model for persistent fibrogenesis and cirrhosis, administration of the adenoviral vector abrogates TGF-beta-enhanced production of collagen and alpha-smooth muscle actin. Furthermore, the number of cells positive for alpha-smooth muscle actin resulting from active recruitment of activated hepatic stellate cells around the bile ductular structures was significantly reduced in animals after application of Ad5-CMV-AS-TGF-beta1. However, the observed elevated serum levels of aspartate aminotransferase, alanine aminotransferase, and bilirubin induced in this obstructive liver injury model were not significantly altered in the presence of the TGF-beta antagonist. Taken together, our data provides in vivo evidence that the delivery of TGF-beta1 antisense mRNA specifically abolishes the diverse effects of direct TGF-beta function in ongoing liver fibrogenesis. Therefore, we conclude that the expressed transgene is therapeutically useful for inhibition of TGF-beta effects in diverse applications, ranging from clarification of TGF-beta function in the course of liver injury to the development of novel gene therapeutic approaches.