Hydrodynamics- and ultrasound-based transfection of heart with naked plasmid DNA

A novel, efficient transfection method, based on ultrasound and hydrodynamics, has been developed to transfect heart tissue with plasmid DNA. An ultrasound probe was aimed at the heart of anesthetized rats for 30 sec, at an intensity of 1 MHz and 2 W/cm2. The aorta was clamped and a phosphate-buffered saline (PBS) solution containing pSV-LacZ was quickly injected into the left ventricle. Each animal was maintained in this condition for 20 sec, and then the clamp was opened and the needle was removed. Electrocardiography, performed after 4 weeks, showed mild or no sign of ischemia in all groups. Visual evaluation of heart tissue samples from rats that received 100 microg of pSV-LacZ in 100 microl had only a few blue cells, indicating transfection, and those that received only PBS had no blue cells. However, all heart tissue samples from rats transfected with 100 to 500 microg of pSV-LacZ in 200 microl, or with 200 to 500 microg of pSV-LacZ in 100 micro had many blue cells. The base and epicardium of the heart tissue samples had many more blue cells than did the rest of the samples. Histological results, based on staining with hematoxylin and eosin, showed similar results between control and transfected groups. Therefore, we concluded that gene delivery by plasmid vector in association with ultrasound and hydrodynamics was highly effective in transfecting rat heart.