Abstract
Background
Safety issues are of paramount importance in clinical human gene therapy. From this point of view, it would be better to develop a novel nonโviral efficient gene transfer method. Recently, it was reported that ultrasound exposure could induce cell membrane permeabilization and enhance gene expression.
Methods
In this study, we examined the potential of ultrasound for gene transfer into the kidney. First, we transfected rat left kidney with luciferase plasmid mixed with microbubbles, Optison, to optimize the conditions (duration of ultrasound and concentration of Optison). Then, 4, 7, 14 and 21 days after gene transfer, luciferase activity was measured. Next, localization of gene expression was assessed by measuring luciferase activity and green fluorescent protein (GFP) expression. Expression of GFP plasmid was examined under a fluorescence microscope at 4 and 14 days after gene transfer. Finally, to examine the side effects of this gene transfer method, biochemical assays for aspartate aminotransferase (AST), alanine aminotransferase (ALT), blood urea nitrogen (BUN) and creatinine (Cre) were performed.
Results
Optison and/or ultrasound significantly enhanced the efficiency of gene transfer and expression in the kidney. Especially, 70โ80% of total glomeruli could be transfected. Also, a significant doseโdependent effect of Optison was observed as assessed by luciferase assay (Optison 25%: 12.5 ร 10^5^ relative light units (RLU)/g tissue; 50%: 31.3 ร 10^5^ RLU/g tissue; 100%: 57.9 ร 10^5^ RLU/g tissue). GFP expression could be observed in glomeruli, tubules and interstitial area. Results of blood tests did not change significantly after gene transfer.
Conclusions
Overall, an ultrasoundโmediated gene transfer method with Optison enhanced the efficiency of gene transfer and expression in the rat kidney. This novel nonโviral method may be useful for gene therapy for renal disease. Copyright ยฉ 2004 John Wiley & Sons, Ltd.