Effectiveness and safety of hydrodynamic gene delivery in animals with fibrotic liver

Hydrodynamic gene delivery (HGD) has emerged as an effective and safe method for transfecting liver hepatocytes in vivo, and has potential for gene therapy of liver fibrosis. The objective of this study was to evaluate the effectiveness and safety of HGD using CCl4 induced fibrotic liver in rats as a model. I demonstrated that there is a progressive reduction of efficiency of HGD in rats with increasing severity of liver fibrosis. Using a reporter plasmid containing luciferase gene, we showed over 2,000-fold decrease in luciferase activity in the liver with advanced fibrosis compared to that of control animals. Reduction in reporter gene expression in fibrotic liver was correlated to lower copy number of plasmid DNA and less amount of luciferase mRNA in the liver. Microscopy analysis revealed significant accumulation of collagen fibers in the boundary of liver lobules and thickened hepatic sinusoidal endothelium. The morphological changes in fibrotic liver are associated with restriction of flow-through across the liver of DNA solution hydrodynamically injected and are responsible for the reduced gene delivery efficiency of the hydrodynamic procedure. Results from electrocardiogram and serum biochemistry show no difference between the control and fibrotic animals undergone HGD. These results suggest that the HGD is a safe method for gene transfer in animals with liver fibrosis but the effectiveness of gene delivery decreases with increase of severity of fibrosis. Future work should focus on adjustment of injection parameters (DNA dose, injection volume, injection speed) for optimal gene delivery to fibrotic liver