Gene therapy for the treatment of hyperhomocysteinemia by naked DNA delivery

Gene therapy is considered as a potential way to treat genetic diseases by replacing the altered gene with a wild type gene.;Hyperhomocysteinemia is considered as an independent risk factor of cardiovascular diseases. It is caused by several factors and genetic defects of cystathionine beta synthase (CBS) is one. In this experiment, we delivered CBS encoding plasmid DNA into CBS knockout mice model to investigate the efficacy of naked DNA delivery.;We found that (1) CBS gene delivery to Balb/c mouse decreased serum homocysteine level by 20%. (2) CBS gene delivery to CBS-/- mice extended life length in treated animals up to 80% compared to 20% of untreated animals and it was partly derived from the enhanced bodyweight gain. (3) CBS gene delivery to CBS+/- mice under high methionine feeding diet also decreased homocysteine level about 20%. This decrease was enough to show the biological effects that the impaired antioxidant enzyme activities (glutathione peroxidase 1, paraoxonase 1 and superoxide dismutase) caused by hyperhomocysteinemia was partially restored by CBS gene delivery.;Two vehicles are commonly used to deliver the gene of interest; viral vector and naked DNA. Because of their ability to efficiently infect human cells, viral vectors have been long favored for gene therapy. Viral vectors are created by deleting most of structural genes and replacing them with a gene of interest. Their expression level is usually higher than other methods. But, short-term gene expression, immune responses and safety issues have been concerned. Naked DNA delivery refers to a delivery system without electroporation, liposome-mediated or other vehicles and it is the most common non-viral vector. It is simple that the gene of interest is inserted into plasmid backbone and amplified in E. coli. DNA itself with saline is administered to the site of interest by needle injection. The duration of gene expression sometimes lasts for the life of an animal and DNA itself does not induce immune responses. As a result, naked DNA delivery considers as a potential candidate where long-term gene expression is required.