Establishment of an early liver fibrosis model by the hydrodynamics-based transfer of TGF-beta1 gene.

Abstract

Background: Liver fibrosis represents a significant and severe health care problem and there are no efficient drugs for therapy so far. Preventing the progression of fibrogenesis and revival endogenous repair activities is an important strategy for both current and future therapies. Many studies of liver fibrosis consist of animal testing with various hepatotoxins. Although this method is often used, the model at which cirrhosis or extensive fibrosis becomes irreversible has not been well defined and is not representative of early-stage fibrogenesis. We here report the establishment of a transient and reversible liver fibrosis animal model which may better represent an early and natural fibrotic event. We used a high-speed intravenous injection of naked plasmid DNA of transforming growth factor-beta1 (TGF-beta1) gene which is under the control of a metallothionein-regulated gene in a pPK9A expression vector into the tail vein (the hydrodynamics-based transfer) and fed the mouse with zinc sulfate (ZnSO4)-containing water simultaneously.

Results: Using our hydrodynamics-based gene transfer model we found that upon induction by ZnSO4, the serum TGF-beta1 level in Balb/c mice and Sp1 transcription factor binding activity peaked at 48 h and declined thereafter to a normal level on the 5th day. In addition, mRNA and protein levels of TGF-beta1 in the liver were also upregulated at 48 h. Furthermore, induction of TGF-beta1 increased the alpha-smooth muscle actin (alpha-SMA), p-Smad2/3, hydroxyproline and collagen 1A2 (Col 1A2) levels in the liver, suggesting a significant liver fibrosis.

Conclusion: Our results show that TGF-beta1 in pPK9a-transferred mice liver with ZnSO4 feeding can achieve a high expression level with significant fibrosis. However, since TGF-beta1 induction is transient in our model, the fibrotic level does not reach a large scale (panlobular fibrosis) as seen in the CCl4-treated liver. Our model hence represents a dynamic and reversible liver fibrosis and could be a useful tool for studying early molecular mechanism of fibrogenesis or screening of antifibrotic drugs for clinical use.