Gene Electro Transfer of Plasmid Encoding Vascular Endothelial Growth Factor for Enhanced Expression and Perfusion in the Ischemic Swine Heart

Myocardial ischemia can damage heart muscle and reduce the heart\u27s pumping efficiency. This study used an ischemic swine heart model to investigate the potential for gene electro transfer of a plasmid encoding vascular endothelial growth factor for improving perfusion and, thus, for reducing cardiomyopathy following acute coronary syndrome. Plasmid expression was significantly greater in gene electro transfer treated tissue compared to injection of plasmid encoding vascular endothelial growth factor alone. Higher gene expression was also seen in ischemic versus non-ischemic groups with parameters 20 Volts (

Gene electro transfer of plasmid encoding vascular endothelial growth factor for enhanced expression and perfusion in the ischemic swine heart.

Myocardial ischemia can damage heart muscle and reduce the heart's pumping efficiency. This study used an ischemic swine heart model to investigate the potential for gene electro transfer of a plasmid encoding vascular endothelial growth factor for improving perfusion and, thus, for reducing cardiomyopathy following acute coronary syndrome. Plasmid expression was significantly greater in gene electro transfer treated tissue compared to injection of plasmid encoding vascular endothelial growth factor alone. Higher gene expression was also seen in ischemic versus non-ischemic groups with parameters 20 Volts (p<0.03), 40 Volts (p<0.05), and 90 Volts (p<0.05), but not with 60 Volts (p<0.09) while maintaining a pulse width of 20 milliseconds. The group with gene electro transfer of plasmid encoding vascular endothelial growth factor had increased perfusion in the area at risk compared to control groups. Troponin and creatine kinase increased across all groups, suggesting equivalent ischemia in all groups prior to treatment. Echocardiography was used to assess ejection fraction, cardiac output, stroke volume, left ventricular end diastolic volume, and left ventricular end systolic volume. No statistically significant differences in these parameters were detected during a 2-week time period. However, directional trends of these variables were interesting and offer valuable information about the feasibility of gene electro transfer of vascular endothelial growth factor in the ischemic heart. The results demonstrate that gene electro transfer can be applied safely and can increase perfusion in an ischemic area. Additional study is needed to evaluate potential efficacy

Heart Rate.

<p>Echocardiography was used to obtain heart rate for pVEGF injection only, sham and pVEGF +GET groups. A) Heart rate before myocardial infarction, after the left anterior descending artery (LAD) was occluded and 14 days post MI. B) Change in heart rate at 2 weeks when compared to pre MI baseline. C) Change in heart rate at 2 weeks when compared to post MI baseline. There were no statistically significant differences in HR between the groups.</p

Ejection Fraction.

<p>Echocardiography was used to obtain levels of ejection fraction for pVEGF injection only, sham and pVEGF +GET groups. A) Ejection fraction levels before MI, after the left anterior descending artery (LAD) was occluded and 14 days post MI. B) Change in ejection fraction at 2 weeks when compared to pre MI baseline. C) Change in ejection fraction at 2 weeks when compared to post MI baseline. There were no statistically significant differences in EF between the groups.</p

Sequence for administration of therapy.

<p>A) The heart was exposed as described in the <a href="http://www.plosone.org/article/info:doi/10.1371/journal.pone.0115235#s2" target="_blank">Methods</a> section under “surgical procedure”. B) The left anterior descending coronary artery is ligated with a permanent suture (arrow) and a SPY image is collected to visualize change in perfusion. C) Sutures are placed to designate the treatment sites. D) Sequence of treatment, applicator containing 4 electrodes and injection port is placed at the treatment site marked by suture; 100 µl of plasmid solution at a concentration of 2 mg/ml is injected; 8 pulses are administered. Procedure is repeated for the other 3 sites.</p

Intra-cardiac delivery of pVax1-hVEGF₁₆₅.

<p>The duration of intra-cardiac delivery of pVax1-hVEGF₁₆₅ was 20 milliseconds at varying voltages. Plasmid expression was significantly greater in the ischemic hearts with parameters 20 milliseconds; 20 V (p<0.03 non- ischemic versus ischemic), 20 milliseconds; 40 V (p<0.05 non- ischemic versus ischemic), and 20 milliseconds; 90 V (p<0.05 non- ischemic versus ischemic), but not with the 20 milliseconds; 60 V parameter (p<0.09 non- ischemic versus ischemic). The non-treated hearts had significantly less expression (p<0.002) than the hearts treated with injection only.</p

Plasma troponin and creatine kinase measurements before and after occlusion of the LAD coronary artery.

<p>Plasma troponin and creatine kinase measurements before and after occlusion of the LAD coronary artery.</p

Expression of pVax1-hVEGF₁₆₅.

<p>pVEGF expression was analyzed over a two week period at 48 hours, 7 days and 14 days. Peak expression was observed at 48 hours in all ischemic tissues at all parameters except 20 milliseconds; 60 V. VEGF expression was significantly greater in the 20 milliseconds; 60 V parameter 14 days after ischemia was produced.</p

Left ventricular end diastolic volume.

<p>Echocardiography was used to obtain left ventricular end diastolic volume (LVEDV) for pVEGF injection only, sham and pVEGF +GET groups. A) LVEDV before myocardial infarction, after the left anterior descending artery (LAD) was occluded and 14 days post MI. B) Change in LVEDV at 2 weeks when compared to pre MI baseline. C) Change in LVEDV at 2 weeks when compared to post MI baseline. There were no statistically significant differences in LVEDV between the groups.</p

Fluorescent Intensity measurement using The SPY Elite Intraoperative Perfusion Assessment System.

<p>Fluorescent Intensity measurement using The SPY Elite Intraoperative Perfusion Assessment System.</p