Gene targeting for site-specific gene therapy

Abstract

For safe and effective gene therapy, the therapeutic gene should be targeted to a specific site. Gene targeting can be achieved at two levels, gene delivery and gene expression. In this research, we developed a method to target the gene expression to hypoxic tissue for ischemic disease gene therapy. Therapeutic angiogenesis with gene encoding vascular endothelial growth factor (VEGF) is a potential treatement in ischemic disease. However, unregulated VEGF mediated angiogenesis ahs the potential to promote tumor growth, accelerate diabetic proliferative retionpathy and promote rupture of atherosclerotic plaque. To limit the risk of pathological angiogenesis, we developed a hypoxia inducible VEGF gene therapy system using the rythropoietin (Epo) enhancer or RTP801 promoter. In vitro transfection to various cells showed that the Epo enhancer or the RTP801 promoter induced the gene expression specifically in the cells under hypoxia. pEpo-SV-VEGF and pRTP801-VEGF were applied to ischemic heart disease and spinal cord injry (SCI). The injection of the pEpo-SV-VEGF showed that the expression of VEGF was induced in ischemic myocardium, compared to normal myocardium. In addition, pEpo-SV-VEGF and pRTP801-VEGF showed higher VEGF expression than pSV-VEGF in ischemicmyocardium. The plasmids were then directly injected into the rat spinal cord with a contusion injury. The VEGF expression level was significantly higher in the pEpo-SV-VEGF group and the pRTP801-VEGF group than the pSV-VEGF group. The locomoter recovery of the SCI rat was improved in the pEpo-SV-VEGF group and the pRTP801-VEGF group, compared with the other groups. These results suggest that the hypoxia inducible VEGF expression system will be useful for the gene therapy of ischemic heart disease and SCI.