Abstract
BackgroundLiver 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-β1 (TGF-β1) 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.ResultsUsing our hydrodynamics-based gene transfer model we found that upon induction by ZnSO4, the serum TGF-β1 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-β1 in the liver were also upregulated at 48 h. Furthermore, induction of TGF-β1 increased the α-smooth muscle actin (α-SMA), p-Smad2/3, hydroxyproline and collagen 1A2 (Col 1A2) levels in the liver, suggesting a significant liver fibrosis.ConclusionOur results show that TGF-β1 in pPK9a-transferred mice liver with ZnSO4 feeding can achieve a high expression level with significant fibrosis. However, since TGF-β1 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.
Highlights
Liver fibrosis represents a significant and severe health care problem and there are no efficient drugs for therapy so far
Many experimental long-term treatment models of liver fibrosis leading to cirrhosis have been useful for testing drug effectiveness but further studies are required to account for effects of disease treatment when gene expressions, especially transforming growth factor-β1 (TGF-β1) gene, has not yet been irreversibly altered [4]
The results indicate that serum levels of TGF-β1 in pPK9atransferred mice fed with ZnSO4 peaked at 48 h and were higher than the four control groups (Fig. 1A)
Summary
Liver fibrosis represents a significant and severe health care problem and there are no efficient drugs for therapy so far. Many studies of liver fibrosis consist of animal testing with various hepatotoxins 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. Many experimental long-term treatment models of liver fibrosis leading to cirrhosis have been useful for testing drug effectiveness but further studies are required to account for effects of disease treatment when gene expressions, especially TGF-β1 gene, has not yet been irreversibly altered [4]. Combining a hydrodynamics-based gene delivery system and the metallothionein-regulated pPK9a vector, we have established a dynamic mouse liver fibrosis model In this model the level of TGF-β1 gene can be overexpressed with the presence of zinc sulfate (ZnSO4) in the drinking water. This model could be useful for studying the initial stages of liver fibrosis
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