Abstract 378: In Vivo Gene Delivery by Ultrasound Targeted Microbubble Destruction Induces Angiogenesis and Benefits Cardiac Function after a Myocardial Infarction
BACKGROUND: Inducing angiogenesis after a myocardial infarction may salvage hibernating myocardium and improve the engraftment of transplanted or recruited precursor cells. This study evaluated the effect of delivering plasmid DNA to induce angiogenesis and/or precursor cell homing using a novel ultrasound targeted microbubble destruction (UTMD) method after a myocardial infarction (MI).
METHODS: MI was generated by LAD ligation in C57Bl/6 female mice (20–25g). Seven days after MI, plasmids (0.6 mg/kg) containing genes of vascular endothelial growth factor (VEGF), stem cell factor (SCF), or green fluorescent protein (GFP) were incubated for 20 minutes with 25 μl of perflutren lipid microsphere (DEFINITY). The plasmid/microsphere complexes were injected intravenously. The UTMD method was employed (one burst of ultrasound energy every 500 msec of MCE) to release the genes in vivo. Myocardial contrast echocardiography was performed prior to and 14 days after UTMD for evaluation of myocardial perfusion. Western blot and ELISA were used to quantify gene expression, and histological study was used to quantify blood vessel density.
RESULS: Some cardiomyocytes and vascular cells in the anterior region were GFP positive, suggesting successful plasmid transfection. At 14 days after plasmid delivery by UTMD, VEGF protein levels increased significantly at the border area in the VEGF group (p=0.031), and SCF protein levels increased in the SCF group (p=0.04). Myocardial perfusion also increased in both VEGF and SCF groups at 14 days after UTMD (p<0.01, p<0.05, respectively). Histological study demonstrated more vascular structure (Factor VIII positive vessels) in both gene groups (VEGF: 80.8 ± 13.3/0.2mm2, SCF: 63.7± 24.7/0.2mm2, control group: 15.3± 1.2/0.2mm2, p<0.001) than in the GFP group. Cardiac function (%FAC) was better in the SCF group than in the VEGF group or GFP control group (p=0.03).
CONCLUSIONS: UTMD delivered the gene product to the infarcted region after MI, inducing angiogenesis and increasing perfusion. SCF over-expression provided functional benefits in addition to the increase in capillary density. UTMD may be an ideal method to stimulate the engraftment of implanted or recruited stem cells to restore function after MI.