Gene expression after intrarenal injection of plasmid DNA in the rat

Effective gene therapy requires efficient delivery and expression of the ne cessary genetic information to the target tissue. We demonstrate here that plasmid DNA, injected as naked, uncomplexed DNA into the cortical region of rat kidney, or intravenously, is localized and expressed in the kidney. Th e plasmid pRSVZ contained the Rous sarcoma virus promoter and a reporter ge ne, the beta-galactosidase gene, derived from bacteria. The beta-galactosid ase gene hydrolyzes the artificial substrate X-gal to produce an intense bl ue color in cells that have taken up and expressed the plasmid genes. We ha ve used X-gal staining and Western blotting to study plasmid gene expressio n 1, 4, and 8 days and 6 months after intrarenal injection of 50 mu g of pl asmid DNA and at 1 and 4 days after intravenous injection. Expression was a pparent in the kidneys and several other tissues 24 h after injection and p ersisted for at least 8 days; expressed proteins could still be detected in the injected kidney 6 months later. These observations were corroborated b y use of a plasmid, pEGFP-Puro, harboring the cytomegalovirus promoter in c onjunction with a different reporter gene, the green fluorescent protein (G FP), Histological localization and Western blotting analysis of GFP express ion after intrarenal injection of pEGFP-Puro paralleled results obtained wi th the plasmid pRSVZ. Our findings support the suggestion that intrarenal o r intravenous injection of naked plasmid DNA may be an effective means of d elivering therapeutic genes to the kidney and several other tissues.