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Objective— MicroRNAs are involved in many critical functions, including angiogenesis. Ultrasound-targeted microbubble destruction (UTMD) is a noninvasive technique for targeted vascular transfection of plasmid DNA and may be well suited for proangiogenic microRNA delivery. We aimed to investigate UTMD of miR-126-3p for therapeutic angiogenesis in chronic ischemia. Approach and Results— The angiogenic potential of miR-126-3p was tested in human umbilical vein endothelial cells in vitro. UTMD of miR-126-3p was tested in vivo in Fischer-344 rats before and after chronic left femoral artery ligation, evaluating target knockdown, miR-126-3p and miR-126-5p expression, phosphorylated Tie2 levels, microvascular perfusion, and vessel density. In vitro, miR-126-3p–transfected human umbilical vein endothelial cells showed repression of sprouty-related protein-1 and phosphatidylinositol-3-kinase regulatory subunit 2, negative regulators of vascular endothelial growth factor and angiopoietin-1 signaling, increased phosphorylated Tie2 mediated by knockdown of phosphatidylinositol-3-kinase regulatory subunit 2 and greater angiogenic potential mediated by both vascular endothelial growth factor/vascular endothelial growth factor R2 and angiopoietin-1 /Tie2 effects. UTMD of miR-126-3p resulted in targeted vascular transfection, peaking early after delivery and lasting for >3 days, and resulting in inhibition of sprouty-related protein-1 and phosphatidylinositol-3-kinase regulatory subunit 2, with minimal uptake in remote organs. Finally, UTMD of miR-126-3p to chronic ischemic hindlimb muscle resulted in improved perfusion, vessel density, enhanced arteriolar formation, pericyte coverage, and phosphorylated Tie2 levels, without affecting miR-126-5p or delta-like 1 homolog levels. Conclusions— UTMD of miR-126 results in improved tissue perfusion and vascular density in the setting of chronic ischemia by repressing sprouty-related protein-1 and phosphatidylinositol-3-kinase regulatory subunit 2 and enhancing vascular endothelial growth factor and angiopoietin-1 signaling, with no effect on miR-126-5p. UTMD is a promising platform for microRNA delivery, with applications for therapeutic angiogenesis.

Background: Ultrasound-targeted microbubble destruction (UTMD) is a non-invasive gene transfection technique using carrier microbubbles and targeted high power ultrasound, primarily used to deliver plasmid DNA (pDNA). Minicircle-DNA (mcDNA) is a novel gene vector, which has recently been shown to have an improved and persistent transfection, compared to conventional pDNA. Hypothesis: We hypothesized that UTMD of mcDNA in a hind-limb model would exhibit a more potent and prolonged gene expression compared to conventional pDNA. Methods: In vitro , HUVECs, fibroblasts (3T3) and neonatal cardiomyocytes were transfected with molar equivalents of GFP-minicircle and GFP-plasmid. GFP expression was measured by RT-PCR and fluorescent microscopy for 28 days. We then performed a comparison of bubble binding capacities of both vectors to cationic lipid microbubbles. In vivo , for UTMD to the left proximal hind-limb adductor muscle, 500μg and 214μg of GFP-plasmid and GFP-minicircle respectively were charge-coupled with 1x10 9 cationic microbubbles and delivered via UMGD into Sprague-Dawley rats (n=30). The animals were followed for 28 days with GFP measured by RT-PCR and immunohistochemistry. Results: In vitro results showed greater GFP expression by mcDNA across all cell lines, with 7-10 fold transfection efficacy compared to pDNA. mcDNA demonstrated greater binding capacity to cationic microbubbles compared to pDNA. For plasmid and minicircle DNA, binding saturations were reached at ~6000 copies per microbubble, and ~20000 copies per microbubble respectively, suggesting a higher minicircle bubble binding efficiency. In vivo results showed higher GFP levels as early as 6 hours post minicircle UTMD, demonstrating minicircle to be a faster acting therapeutic agent over conventional plasmid. A significantly greater (p Conclusions: In summary, UTMD using mcDNA results in more rapid and sustained transfection compared to conventional pDNA, and may be a more effective vector for translational studies of UTMD.

Background: Diabetes mellitus is a chronic metabolic disease associated with various vascular complications. Various strategies to promote therapeutic angiogenesis in ischemic tissue including delivery of pro-angiogenic growth factors have shown disappointing results. Risk factors, such as diabetes, may adversely impact the response to angiogenic strategies and limit efficacy in vivo. We assessed the hypothesis that temporally separated delivery of multiple pro-angiogenic growth factors will improve the efficacy of the angiogenic response in the setting of both diabetes and non-diabetes in vitro. Methods: 96-well tissue culture plates were coated with 60 μL growth factor reduced Matrigel. After gelation, non-diabetic human dermal microvascular endothelial cells (HMVECs) and type-II diabetic cells (D-HMVECs) were plated at 1x104 cells/well with 100 μL basal media EBM-2 with 0.1% bovine serum, and incubated at 37°C. Combinations of growth factors including recombinant human VEGF (50 ng/mL), angiopoietin (Ang)-1 and -2 (250 ng/mL) were administrated at start of the assay and/or at 6 hours into the assay. Images were taken at 3, 6, 9, 12, 18 and 24 hours and used for tube formation quantification by Inverted Microscope at 10x magnification. Results: In untreated control, D-HVECs showed reduced tube formation in compared to HMVECs (n=12; p Conclusion: Diabetic endothelial cells showed impaired angiogenesis compared to non-diabetic endothelial cells. Combinations of temporally separated pro-angiogenic growth factors were able to optimize the angiogenic effects and yield the most significant efficacy in the setting of both diabetes and non-diabetes. Future studies will focus on in vivo temporally separated combinations of multiple growth factors.