Comparison of Gene Delivery Techniques for Therapeutic Angiogenesis : Ultrasound-Mediated Destruction of Carrier Microbubbles Versus Direct Intramuscular Injection

ObjectivesThis study was designed to compare the efficacy of angiogenic gene delivery by ultrasound-mediated (UM) destruction of intravenous carrier microbubbles to direct intramuscular (IM) injections.BackgroundCurrent trials of gene therapy for angiogenesis remain limited by suboptimal, invasive delivery techniques.MethodsHind-limb ischemia was produced by iliac artery ligation in 99 rats. In 32 rats, UM delivery of green fluorescent protein (GFP)/vascular endothelial growth factor-165 (VEGF165) plasmid deoxyribonucleic acid was performed. Thirty-five animals received IM injections of VEGF165/GFP plasmid. Remaining rats received no treatment. Before delivery (day 14 after ligation) and at days 17, 21, and 28 and week 8 after ligation, microvascular blood volume and microvascular blood flow to the proximal hind limbs were assessed by contrast-enhanced ultrasound (n = 8 per group). Total transfection was assessed by reverse transcriptase–polymerase chain reaction, and localization of transfection was determined by immunohistochemistry.ResultsBy day 28, both IM and UM delivery of VEGF165produced significant increases in microvascular blood volume and microvascular blood flow. Whereas increases in microvascular blood volume were similar between treatment groups, microvascular blood flow was greater (p < 0.005) in UM-treated animals as compared with IM-treated animals, persisting to week 8. The VEGF165/GFP messenger ribonucleic acid expression was greater (p < 0.05) for IM-treated animals. A strong GFP signal was detected for both groups and was localized to focal perivascular regions and myocytes around injection sites for IM and to the vascular endothelium of arterioles/capillaries in a wider distribution for UM delivery.ConclusionsDespite lower transfection levels, UM delivery of VEGF165is as effective as IM injections. The UM delivery results in directed vascular transfection over a wider distribution, which may account for the more efficient angiogenesis.