A Simple, Quantitative Method for Assessing Angiogenic Genes Using Skeletal Muscle by Electroporation-Mediated Naked DNA Delivery

ABSTRACT

BACKGROUND AND OBJECTIVES: For the development of an arteriogenic gene therapy in peripheral artery occlusive disease, we developed a novel angiogenesis assay, with electroporation-mediated naked DNA delivery to the skeletal muscle. MATERIALS AND METHODS: The levels of the expression CAT were compared between pJDK and pcDNA3.1, in HeLa and C2C12 cell lines, and skeletal muscle. The well known angiogenic gene, pJDK-hVEGF165, was injected, intramuscularly, into the tibialis anterior muscle of Balb/C mice, which was followed by electroporation. Two days later, the anterior tibialis muscles were divided into halves, embedded, and cultured in growth factor-reduced Matrigel. The capillary network area formed by the newly sprouting tube-like structures was calculated. For validation of this ex vivo assay, the connective tissue growth factor gene (pJDK-CTGF) was tested both by this new assay, and by the mice-hind limb ischemia model, with Laser Doppler imaging. RESULTS: The pJDK showed a significantly higher level of CAT expression than the pcDNA3.1. From the pJDK-hVEGF165 injected explants, endothelial cell migration and tube-like formation occurred on day 2, and the capillary network formation peaked on day 7. The capillary network formation in the pJDK-hVEGF165 group was markedly increased to that in the pJDK group. From the skeletal muscle assay, the pJDK-CTGF showed no angiogenic activity or attenuated VEGF-induced capillary network formation. The LDI flux ratio, on day 10 in the mice-hind limb ischemia model, for the mice treated with the pJDK-CTGF and pJDK-hVEGF165 was significantly lower than that of the mice treated with the pJDK-hVEGF165 alone. CONCLUSION: The skeletal muscle ex vivo assay, using an electroporation-mediated naked DNA delivery, is a simple, quantitative and reproducible method for assessing angiogenic genes. CTGF could be an anti-angiogenic factor due to its inhibition of VEGF.