Ischemic injury-specific VEGF gene expression in the rat spinal cord injury model

초록

Background data and objects Gene therapy is an emerging therapeutic technique to treat spinal cord injury (SCI). However, uncontrolled overexpression of therapeutic genes (VEGF) in non-disease tissues during therapy raises a doubt about its safety. We hypothesized that the expression system controlled by tissue oxygenation could be a useful therapeutic principle for treating SCI by reducing the dangerous side effects of unregulated gene expression in normal spinal promoter for the hypoxia-inducible gene expression. To limit the risk of unwanted overexpression of VEGF genes, we developed a hypoxia-inducible gene therapy system using the erythropoietin (Epo) enhancer and the RTP801 promoter.Results 1. pEpo-SV-Luc and pRTP801-Luc showed more than three times higher gene expression in N2A cells under hypoxia than normoxia. The expression level of luciferase in the injured spinal cord was higher than in the normal spinal cord. Immunostaining demonstrated that neurons, astrocytes ans capillary endothelial cells expressed luciferase in the cytoplasm. 2. VEGF gene expression is also increased in pEpo-SV-VEGF and pRTP801-VEGF than SV40-VEGF. Animals treated with pEpo-SV-VEGF show significantly improved locomotor recovery versus animals in the SV40-VEGF group. Conclusion The pEpo-SV-VEGF and pRTP801-VEGF systems are effective in that it induces gene expression specifically in neuron under the hypoxic condition and spinal cord injury. Furthermore, the pEpo-SV-VEGF and pRTP801-VEGF systems could improve neurologic functions in rat SCI model. These findings suggest that gene therapy using hypoxia-inducible gene expression system is one of important therapeutic principles treating SCI.