Angiogenic Gene Therapy Research Articles

Timing of capillary enlargement after adenoviral VEGF gene transfer does not support post-ischemic skeletal muscle recovery in hyperlipidemic mice

Abstract Funding Acknowledgements Type of funding sources: Public grant(s) – National budget only. Main funding source(s): Finish Academy (Clinical Researcher 324070 and Research Project 339560). Finnish Foundation for Cardiovascular Research Background Transient capillary enlargement has been shown to be essential for successful post-ischemic tissue recovery as it may facilitate the return of arterial driving pressure by supporting collateral maturation. It also leads to an intussusceptive increase in capillary density that supports efficient oxygen delivery and muscle regeneration. Hyperlipidemia has been shown to blunt post-ischemic capillary reactivity and hinder skeletal muscle recovery from ischemia. Therefore, it can be hypothesized that correction of capillary reactivity might improve post-ischemic muscle recovery under hyperlipidemia. Purpose The aim of this study was to test the ability of angiogenic VEGF gene therapy in improving post-ischemic muscle recovery under hyperlipidemia. Methods AdVEGF gene transfer was performed into the calf muscles of aged, hyperlipidemic LDLR-/-ApoB100/100 mice after acute ischemia induction. The effects of AdVEGF on capillary phenotype, tissue edema, restoration of blood flow parameters, microvascular hemoglobin oxygenation and tissue damage/regeneration were evaluated for up to 29 days post-procedure as compared to AdLacZ control using immuno- and histological analyses, magnetic resonance, contrast-enhanced ultrasound and photoacoustic imaging, respectively. Results AdVEGF gene therapy was able to promote capillary enlargement that led to recovery of arterial driving pressure in ischemic LDLR-/-ApoB100/100 muscles. However, capillary enlargement induced by AdVEGF appeared late, lasted up to 29 days and did not promote intussusception. Consequently, the negative effect of long-lasting enlargement, i.e., massive tissue edema, delayed blood flow recovery and aggravated ischemic tissue damage. Conclusion Proper time of induction and duration of capillary enlargement are crucial to yield a functional vascular response supporting post-ischemic tissue recovery.

Angiogenic Gene Therapy for Refractory Angina: Results of the EXACT Phase 2 Trial.

XC001 is a novel adenoviral-5 vector designed to express multiple isoforms of VEGF (vascular endothelial growth factor) and more safely and potently induce angiogenesis. The EXACT trial (Epicardial Delivery of XC001 Gene Therapy for Refractory Angina Coronary Treatment) assessed the safety and preliminary efficacy of XC001 in patients with no option refractory angina. In this single-arm, multicenter, open-label trial, 32 patients with no option refractory angina received a single treatment of XC001 (1×1011 viral particles) via transepicardial delivery. There were no severe adverse events attributed to the study drug. Twenty expected severe adverse events in 13 patients were related to the surgical procedure. Total exercise duration increased from a mean±SD of 359.9±105.55 seconds at baseline to 448.2±168.45 (3 months), 449.2±175.9 (6 months), and 477.6±174.7 (12 months; +88.3 [95% CI, 37.1-139.5], +84.5 [95% CI, 34.1-134.9], and +115.5 [95% CI, 59.1-171.9]). Total myocardial perfusion deficit on positron emission tomography imaging decreased by 10.2% (95% CI, -3.1% to 23.5%), 14.3% (95% CI, 2.8%-25.7%), and 10.2% (95% CI, -0.8% to -21.2%). Angina frequency decreased from a mean±SD 12.2±12.5 episodes to 5.2±7.2 (3 months), 5.1±7.8 (6 months), and 2.7±4.8 (12 months), with an average decrease of 7.7 (95% CI, 4.1-11.3), 6.6 (95% CI, 3.5-9.7), and 8.8 (4.6-13.0) episodes at 3, 6, and 12 months. Angina class improved in 81% of participants at 6 months. XC001 administered via transepicardial delivery is safe and generally well tolerated. Exploratory improvements in total exercise duration, ischemic burden, and subjective measures support a biologic effect sustained to 12 months, warranting further investigation. URL: https://www.clinicaltrials.gov; Unique identifier: NCT04125732.

Angiogenic gene therapy for refractory angina: results of the epicardial delivery of XC001 gene therapy for refractory angina coronary treatment (EXACT) phase 2 trial

Abstract Background Refractory or "no option" angina (RA) is a debilitating condition with increasing global prevalence. Exogenous transduction of vascular endothelial growth factor (VEGF) induces angiogenesis and improves perfusion of ischemic myocardium in preclinical studies. XC001 (AdVEGFXC1) is a novel adenoviral-5 vector expressing the three major isoforms of VEGF (-121, -165, -189) in ratios shown to enhance potency and improve safety. Purpose EXACT is a single-arm, multicenter, open-label, phase 2 trial to explore the safety, tolerability, and preliminary efficacy of trans-epicardial delivery of XC001 to improve exercise capacity and ischemic burden in RA patients. Methods Patients were required to have stable Canadian Cardiovascular Society (CCS) class II-IV angina on maximally tolerated medical therapy with exercise limited by angina after 90 but before 540 seconds on a modified Bruce protocol, demonstrable ischemia on stress positron emission tomography (PET) and lack revascularization options. XC001 (1x1011 viral particles) was injected directly into ischemic myocardium via surgical transthoracic epicardial access. The primary outcome was safety by adverse event monitoring. Efficacy assessments included difference from baseline to six months in total exercise time (TET), myocardial ischemia by PET, angina class, angina frequency, and quality of life. Results Thirty-two patients (mean/median ages of 64/64, 34% female) were enrolled at 13 sites between March 2021 and July 2022. Median anti-anginal use was 3, 75% had prior revascularization with CABG and 88% with PCI. Fifty-five serious adverse events (SAEs) were observed in 21 patients (66%). None were attributed to study drug. Twenty-one SAEs in 14 patients were related to the surgical procedure, all of which were expected. One non-CV death occurred in month 3 following respiratory infection (Covid) deemed unrelated to surgery or study drug. Compared to baseline, total exercise time at 6-months increased by 85.5 seconds (95% CI 31.3-139.7) [Figure 1A] while total myocardial ischemic deficit in the treated region on PET decreased by 14.4% (95% CI, 3.01–25.73) [Figure 1B]. Angina frequency and nitroglycerin use measured during a two-week diary decreased by 6.6 episodes (95% CI, 3.5–9.7) and 4.1 doses (95% CI, 1.3–6.9), respectively. Canadian Cardiovascular Society angina grade decreased from 3.1 to 1.8, mean difference 1.3 classes (95% CI, 1.0–1.6) [Figure 2] while Seattle Angina Questionnaire Frequency score improved from 41.3 to 67.4, mean difference of 26.1 (95% CI, 16.3–35.9). Conclusions VEGF gene therapy with XC001 administered via minimally invasive epicardial delivery appears safe and well tolerated. Improvements in objective and subjective measures including total exercise time, myocardial perfusion, angina frequency and quality of life support a clinically meaningful biologic effect. This therapy warrants study in larger randomized studies.

Thymosin ß4 and MRTF-A mitigate vessel regression despite cardiovascular risk factors.

Since clinical revascularization techniques of coronary or peripheral artery disease (CAD/PAD) focus on macrovessels of the heart, the microcirculatory compartment largely goes unnoticed. However, cardiovascular risk factors not only drive large vessel atherosclerosis, but also microcirculatory rarefaction, an instance unmet by current therapeutic schemes. Angiogenic gene therapy has the potential to reverse capillary rarefaction, but only if the disease-causing inflammation and vessel-destabilization are addressed. This review summarizes the current knowledge with regard to capillary rarefaction due to cardiovascular risk factors. Moreover, the potential of Thymosin ß4 (Tß4) and its downstream signal, myocardin-related transcription factor-A (MRTF-A), to counteract capillary rarefaction are discussed.

Progress in Clinical Gene Therapy for Cardiac Disorders.

Despite significant advances in novel treatments and approaches, cardiovascular disease remains the leading cause of death globally. Gene therapy is a promising option for many diseases, including cardiovascular diseases. In the last 30 years, gene therapy has slowly proceeded towards clinical translation and recently reached US Food and Drug Administration approval for several diseases such as Leber congenital amaurosis and spinal muscular atrophy, among others. Previous attempts at developing gene therapies for cardiovascular diseases have yielded promising results in preclinical studies and early-phase clinical trials. However, larger trials failed to demonstrate consistent benefits in patients with ischemic heart disease and heart failure. In this review, we summarize the history and current status of clinical cardiac gene therapy. Starting with angiogenic gene therapy, we also cover more recent gene therapy trials for heart failure and cardiomyopathies. New programs are actively vying to be the first to get Food and Drug Administration approval for a cardiac gene therapy product by taking advantage of novel techniques.

Vasculogenic gene therapy: No role for revitalization of structural bone allografts.

Segmental bone defects are often performed with cryopreserved allografts. They provide immediate stability, but risk nonunion, infection and late stress fracture. Improving the rate and extent of bone revitalization may improve results. Angiogenesis from surgically placed arteriovenous (AV) bundles improves bone blood flow and vitality in cryopreserved rat femora, augmented by vasculogenic growth factors. This study tests the same principal in Yucatan mini-pigs with a tibial diaphyseal defect, combining surgical angiogenesis with angiogenic gene therapy within cryopreserved orthotopically-placed allografts. Tibial diaphyseal defects were reconstructed with cryopreserved allografts and rigid internal fixation in 16 mini pigs. Half of the cranial tibial AV bundles placed within the allograft medullary canal were transfected with an adeno-associated virus containing vascular endothelial growth factor (VEGF) and platelet-derived growth factor (PDGF) genes (AAV9.VEGF.PDGF). Bone remodeling, angiogenesis, and allograft healing were assessed. During the postoperative survival period 5 of 8 transfected animals developed cutaneous benign vascular lesions at sites remote from the operated hindlimb, causing excessive bleeding. Within the allograft, both medullary (p = 0.013) and cortical (p = 0.009) vascular volumes were higher and vessels more mature than nontransfected allografts. Bone turnover (p = 0.013), bone mineralization (p = 0.018), bone healing (p = 0.008) and graft incorporation (p = 0.006) were all significantly higher in the gene therapy group. In a large animal tibial defect model, gene therapy of implanted AV bundles improved revascularization, remodeling and healing of cryopreserved allografts used for limb reconstruction. However, benign vascular lesions causing excessive bleeding developed in 5 out of 8 pigs transfected with AAV containing genes for VEGF and PDGF. This unforeseen complication makes vasculogenic gene therapy unacceptable for clinical use.

Gene Therapy of Chronic Limb-Threatening Ischemia: Vascular Medical Perspectives.

A decade ago, gene therapy seemed to be a promising approach for the treatment of chronic limb-threatening ischemia, providing new perspectives for patients without conventional, open or endovascular therapeutic options by potentially enabling neo-angiogenesis. Yet, until now, the results have been far from a safe and routine clinical application. In general, there are two approaches for inserting exogenous genes in a host genome: transduction and transfection. In case of transduction, viral vectors are used to introduce genes into cells, and depending on the selected strain of the virus, a transient or stable duration of protein production can be achieved. In contrast, the transfection of DNA is transmitted by chemical or physical processes such as lipofection, electro- or sonoporation. Relevant risks of gene therapy may be an increasing neo-vascularization in undesired tissue. The risks of malignant transformation and inflammation are the potential drawbacks. Additionally, atherosclerotic plaques can be destabilized by the increased angiogenesis, leading to arterial thrombosis. Clinical trials from pilot studies to Phase II and III studies on angiogenic gene therapy show mainly a mixed picture of positive and negative final results; thus, the role of gene therapy in vascular occlusive disease remains unclear.

Title: Gene transfer by pyro-drive jet injector is a novel therapeutic approach for muscle diseases.

The angiogenic gene therapy is an attractive approach for the treatment of ischemic muscle diseases, including peripheral arterial disease and ischemic heart diseases. Although a variety of gene transfer methods have been developed, the efficiency of gene transfer is still limited. We have been developing the needleless high-energy bioinjector device, Pyro-drive Jet Injector (PJI), based on pyrotechnics using a combination of ignition powder and gunpowder, however, the utility of PJI in gene transfer into muscle tissues remains unclear. pcDNA3.1 plasmid containing Flag was injected to the thigh muscles of C57BL/6J mice using PJI or needle, as a control. Histological analysis demonstrated that the protein expression of Flag was observed in a wider range in PJI group than in needle group. To assess the validity of PJI for gene therapy, pcDNA3.1-human fibroblast growth factor 2 (FGF2), which has angiogenic activity and tissue protective properties, was injected into the ischemic thigh muscles with PJI or needle. ELISA assay revealed that the protein expression of FGF2 was increased in the thigh muscle tissues by PJI-mediated gene delivery. Significantly, histological analyses revealed that muscle fiber cross-sectional area and the number of endothelial marker CD31 (+) cells was increased in ischemic hind-limb tissues of the PJI-FGF2 group but not in those of needle-FGF2 group. To expand the applicability of the PJI-mediated gene transfer, pcDNA3.1-venus plasmid was injected into murine hearts with PJI or needle. PJI method was successful in gene transfer into murine hearts, especially into cardiomyocytes, with high efficiency when compared to needle method. Collectively, the non-needle, non-liposomal and non-viral gene transfer by PJI could be a novel therapeutic approach for muscle diseases.

Adenoviral Gene Transfer of Gremlin Modulates Vascular Endothelial Growth Factor-A-Induced Angiogenesis in Porcine Myocardium.

Coronary artery disease is a major cause of death and disability worldwide. New therapies are needed for patients who do not benefit or are not suitable for current treatments. Angiogenic gene therapy using vascular endothelial growth factors (VEGFs) has shown potential in preclinical trials. However, undesired side effects, such as increased permeability, limit their therapeutic potential. The aim of this study was to investigate if adenoviral gene transfer of a VEGF receptor 2 (VEGFR-2) ligand Gremlin, given simultaneously with VEGF-A, could modulate VEGFR-2-mediated increase in permeability without impairing the angiogenic effect of VEGF-A gene therapy. Gene transfers were done in pigs (n = 22) using endocardial injections with an endovascular injection catheter. Animals were divided in three groups receiving adenoviral (Ad) VEGF-A (n = 10), Gremlin (n = 6), or VEGF-A+Gremlin (n = 6) gene therapy. Animals were sacrificed and samples collected 6 days later for histological, safety, and permeability analyses. The mean capillary area was significantly increased in both treatment groups with AdVEGF-A when compared with the AdGremlin group. Also, the capillary area was significantly larger in AdVEGF-A group without AdGremlin. No significant differences in tissue permeability were observed using modified Miles assay between AdVEGF-A and AdVEGF-A+AdGremlin groups. However, cardiac tamponade and sudden cardiac deaths were observed only in the AdVEGF-A group. AdVEGF-A induces strong angiogenesis in porcine myocardium. Our results suggest that AdGremlin can limit the side effects of AdVEGF-A therapy, even though no direct effect on tissue permeability could be demonstrated. This could enable the use of larger AdVEGF-A doses to increase the treatment area and angiogenic effects without adverse side effects.

Evaluation of vector mediated gene therapy as a novel approach to mitigate cardiovascular diseases; A short review

Positioning in the top list of mortality and morbidity, cardiovascular disease (CVD) is required new approaches to mitigate the risk and prevalence. Recombinant DNA (rDNA) technology and genome sequencing explore the new horizon to treat CVD through modified therapy. Gene transfer mechanism eventually angiogenic gene therapy provides efficacy in early-stage heart failure. Targeted gene delivery system depicts the novel therapeutic pattern for both genetic disorder and pathophysiological deficit and opens the pathway of early diagnose and treatment. Despite some limitations of a specific vector (viral vector) mediated gene transfer, these new approaches make hope on CVD treatment rather than the surgery and other ways. Furthermore, some vectors are less hazardous than viral vectors to suggest successful non-viral gene modulations to Cardiovascular tissues and perform in the clinical trial. However, plasmid-mediated gene transfer method along with genome editing technology might be the best possible approach for future CVD prognostics and diagnostics.

Long-term follow-up and safety assessment of angiogenic gene therapy trial VIF-CAD: Transcatheter intramyocardial administration of a bicistronic plasmid expressing VEGF-A165/bFGF cDNA for the treatment of refractory coronary artery disease

There have been a number of angiogenic gene therapy trials, yielding mixed results as to efficacy, but demonstrating uniform short-term treatment safety. Data regarding long-term safety of angiogenic gene therapy are limited. Double-blind VIF-CAD trial (NCT00620217) assessed myocardial perfusion and clinical data in 52 refractory coronary artery disease (CAD) patients randomized into treatment (VIF; n = 33) and Placebo (n = 19) arms. VIF group received electromechanical system NOGA-guided intramyocardial injections of VEGF-A165/bFGF plasmid (VIF) into ischemic regions, while the Placebo group—placebo plasmid injections. Full 1-year follow-up data have been published. This study presents the results of over 10-year (median 133 months, range 95-149) safety follow-up of VIF-CAD patients. Overall, 12 (36.4%) patients died in VIF and 8 (42.1%) in Placebo group (P = .68). Cardiovascular mortality was 12/33 (36.4%) in the VIF group and 6/19 (31.6%) in Placebo group (P = .73). Two Placebo patients died due to malignancies, but no VIF patients (P = .17). The Kaplan-Meier curves of combined endpoint: cardiovascular mortality, myocardial infarction and stroke were similar for both patient groups (P = .71). Odds ratio of Placebo group increasing (reaching a worse) their CCS class versus VIF was non-significant (OR 1.28, 95% CI = 0.66-2.45; P = .47). However, CCS class improved in time irrespectively of treatment—OR of reaching a less favorable CCS class per each year of follow-up was 0.74 (95% CI 0.685-0.792; P < .0001, pooled data). There were no differences in readmission rates.Intramyocardial VEGF-A165/bFGF plasmid administration appears safe, with no evidence of an increase in the incidence of death, malignancy, myocardial infarction or stroke during 10-year follow-up in this limited patient population.

Therapeutic Benefit and Gene Network Regulation by Combined Gene Transfer of Apelin, FGF2, and SERCA2a into Ischemic Heart.

Despite considerable advances in cardiovascular disease treatment, heart failure remains a public health challenge. In this context, gene therapy appears as an attractive approach, but clinical trials using single therapeutic molecules result in moderate benefit. With the objective of improving ischemic heart failure therapy, we designed a combined treatment, aimed to simultaneously stimulate angiogenesis, prevent cardiac remodeling, and restore contractile function. We have previously validated IRES-based vectors as powerful tools to co-express genes of interest. Mono- and multicistronic lentivectors expressing fibroblast growth factor 2 (angiogenesis), apelin (cardioprotection), and/or SERCA2a (contractile function) were produced and administrated by intramyocardial injection into a mouse model of myocardial infarction. Data reveal that combined treatment simultaneously improves vessel number, heart function parameters, and fibrosis prevention, due to FGF2, SERCA2a, and apelin, respectively. Furthermore, addition of SERCA2a in the combination decreases cardiomyocyte hypertrophy. Large-scale transcriptome analysis reveals that the triple treatment is the most efficient in restoring angiogenic balance as well as expression of genes involved in cardiac function and remodeling. Our study validates the concept of combined treatment of ischemic heart disease with apelin, FGF2, and SERCA2a and shows that such therapeutic benefit is mediated by a more effective recovery of gene network regulation.

HIF-1α Dependent Wound Healing Angiogenesis In Vivo Can Be Controlled by Site-Specific Lentiviral Magnetic Targeting of SHP-2

Hypoxia promotes vascularization by stabilization and activation of the hypoxia inducible factor 1α (HIF-1α), which constitutes a target for angiogenic gene therapy. However, gene therapy is hampered by low gene delivery efficiency and non-specific side effects. Here, we developed a gene transfer technique based on magnetic targeting of magnetic nanoparticle-lentivirus (MNP-LV) complexes allowing site-directed gene delivery to individual wounds in the dorsal skin of mice. Using this technique, we were able to control HIF-1α dependent wound healing angiogenesis invivo via site-specific modulation of the tyrosine phosphatase activity of SHP-2. We thus uncover a novel physiological role of SHP-2 in protecting HIF-1α from proteasomal degradation via a Src kinase dependent mechanism, resulting in HIF-1α DNA-binding and transcriptional activity invitro and invivo. Excitingly, using targeting of MNP-LV complexes, we achieved simultaneous expression of constitutively active as well as inactive SHP-2 mutant proteins in separate wounds invivo and hereby specifically and locally controlled HIF-1α activity as well as the angiogenic wound healing response invivo. Therefore, magnetically targeted lentiviral induced modulation of SHP-2 activity may be an attractive approach for controlling patho-physiological conditions relying on hypoxic vessel growth at specific sites.

Angiogenic gene therapy in cardiovascular diseases: dream or vision?

Chronic cardiovascular diseases are significant health problems. Although current treatment strategies have tremendously improved disease management, up to 30% of these patients cannot be successfully treated with current treatment approaches and new treatment strategies are clearly needed. Gene therapy and therapeutic vascular growth may provide a new treatment option for these patients. Several growth factors, like vascular endothelial growth factors, fibroblast growth factors and hepatocyte growth factor have been tested in clinical trials. However, apart from demonstration of increased vascularity, very few results with clinical significance have been obtained. Problems with gene transfer efficiency, short duration of transgene expression, selection of endpoints, and suboptimal patients for gene therapy have been recognized. Ongoing gene therapy trials have included improvements in study protocols, vector delivery and endpoints, addressing the identified problems. Better, targeted delivery systems and new, more optimal growth factors have been taken to clinical testing. Recent advances in these areas will be discussed and the concept of angiogenic therapy as a sole treatment is re-evaluated. A combination with regenerative therapies or standard revascularization operations might be needed to improve tissue function and clinical benefits.

AdVEGF-B186 and AdVEGF-DΔNΔC induce angiogenesis and increase perfusion in porcine myocardium

ObjectiveCoronary heart disease remains a significant clinical problem, and new therapies are needed especially for patients with refractory angina for whom the current therapies do not provide sufficient relief. The...

Ultrasound imaging with bolus delivered contrast agent for the detection of angiogenesis and blood flow irregularities.

Highly increased blood flow and vascularity after angiogenic gene therapy have raised concerns of shunting and hemangioma-like blood pool formation that might decrease effective perfusion and ruin the beneficial effects of the therapy. Contrast enhanced ultrasound is a promising noninvasive tool for studying skeletal muscle perfusion. The objectives of the present study were to test bolus and infusion administrations of ultrasound microbubble contrast media in imaging vascular growth in skeletal muscle and assess the functionality of vessels grown with angiogenic gene therapy. Contrast enhanced ultrasound was used to study changes in skeletal muscle perfusion in normal and gene-transduced rabbit hindlimbs 6 days after gene transfer. Adenoviral gene transfer of VEGF (10e(9)-10e(11) viral particles) or β-galactosidase control gene (10e(11) viral particles) was done under anesthesia and induced up to 16-fold increases in relative tissue perfusion. Contrast intensity versus time curves were plotted and analyzed for contrast kinetics. Bolus administration of the contrast media was highly feasible in analyzing skeletal muscle blood flow and its kinetics. Maximal signal intensity of the bolus signal reflected relative changes in both blood flow and volume equally to the infusion method. Flow irregularities were detected after angiogenic gene therapy. In conclusion, bolus delivery of ultrasound contrast agent is highly feasible for the relative analysis of both quantity and quality of blood flow after angiogenic gene therapy. The kinetics of blood flow can and should be studied more extensively in both preclinical and clinical trials of angiogenic gene therapy since there is increasing evidence of flow irregularities in angiogenic vessels.

Identifying and overcoming obstacles in angiogenic gene therapy for myocardial ischemia.

Well-developed coronary collateral vessels in patients with symptomatic coronary artery disease were shown to be associated with reduced future cardiovascular morbidity and mortality. However, the majority of patients with coronary artery disease lack adequate functional coronary collateral circulation. Stimulation of collateral vessel development by angiogenic growth factor therapy (therapeutic angiogenesis) has been tested in many clinical trials in the past, but the potential of this new treatment paradigm has not been realized yet in late stage clinical trials. Mechanistic insights into collateral vessel development and the collective clinical experience in the past decade identified specific obstacles that might have impeded the progress in the field. This review identifies some of the key conceptual, technical, and clinical hurdles and recommends strategies to overcome them in future clinical trials.

Reduced ischemic injury after stroke in mice by angiogenic gene delivery via ultrasound-targeted microbubble destruction.

Angiogenic gene therapy in patients with cerebral infarcts may have clinical benefit, but its potential is diminished by the difficulty of introducing genes into the brain. We evaluated the safety and efficacy of ultrasound-targeted microbubble destruction (UTMD) for delivery of genes to the brains of normal mice and after transient middle cerebral artery occlusion. In normal mice, disruption of the blood-brain barrier detected with trypan blue staining was reversible within 24 hours of a single UTMD administration. Expression of reporter genes in the brain after UTMD demonstrated successful targeted gene delivery and transfection. Decreased neurologic function after transient middle cerebral artery occlusion was attenuated versus controls at 7 days after UTMD delivery of vascular endothelial growth factor. Ultrasound-targeted microbubble destruction delivery of the VEGF gene resulted in decreased infarct areas, increased vessel density, and reduced apoptosis versus controls. There was no evidence of permanent brain injury throughout the study. Thus, UTMD was a safe, minimally invasive, effective technique for gene delivery to the brain. Vascular endothelial growth factor transfection of brain cells conferred beneficial effects on histopathologic parameters and neurologic function, and stimulated angiogenesis in a mouse stroke model.

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New Thoughts in an Old Player: Role of Nitrite in the Treatment of Ischemic Revascularization

By 2030, it is estimated that there will be 439 million people in the world with diabetes. Diabetes is a major risk factor for the development of atherosclerotic peripheral arterial disease (PAD), which is typically caused by progressive narrowing of the arteries in the lower extremities (1). Traditionally, the treatment of PAD has focused on smoking cessation, exercise to promote collateral blood flow, and pharmaceutical vasodilatation to optimize microvascular reserve. Often, aggressive revascularization such as angioplasty and bypass grafting is required to salvage limbs and avoid major amputation in patients with critical limb ischemia. However, restenosis rates after endovascular intervention are high, and while recent advances in drug-eluting balloons and stents have promise, their impact on limb salvage remains unproven (2). Recently, therapeutic angiogenesis has been proposed to induce new blood vessel growth for the treatment or prevention of critical limb ischemia by pharmacological and molecular targeting with vascular endothelial growth factor (VEGF), fibroblastic growth factor, granulocyte colony–stimulating factors, granulocyte-macrophage colony–stimulating factors, angiogenic gene therapy, and endothelial progenitor cells (3). Although preclinical and early-stage clinical results are promising, the strategy of augmenting expression of a single factor has failed to deliver significant clinical improvement. Thus, there remains a clear need for better interventions to induce therapeutic angiogenesis in diabetes-related PAD. One therapeutic strategy is to increase nitric oxide (NO) in order to stimulate angiogenesis in conditions such as ischemia–reperfusion injury, cerebral ischemia, kidney injury, coronary …