Results from a phase II multicenter, double-blind placebo-controlled study of Del-1 (VLTS-589) for intermittent claudication in subjects with peripheral arterial disease

Racial and ethnic representation in peripheral artery disease randomized clinical trials

Clinical trial enrollment provides various benefits to study participants including early access to novel therapies that may potentially alter the trajectory of disease states. Trial sponsors benefit from enrolling demographically diverse trial participants enabling the trial outcomes to be generalizable to a larger proportion of the community at large. Despite these and other well-documented benefits, clinical trial enrollment for Black and Hispanic Americans as well as women continues to be low. Specific disease states such as peripheral artery disease (PAD) have a higher prevalence and clinical outcomes are relatively worse in Black Americans compared with non-Hispanic white Americans. The recruitment process for PAD clinical trials can be costly and challenging and usually comes at the expense of representation. Participant willingness and trust, engagement, and socioeconomic status play essential roles in the representation of under-represented minority (URM) groups. Despite the contrary belief, URM groups such as Blacks and Hispanics are just as willing to participate in a clinical trial as non-Hispanic Whites. However, financial burdens, cultural barriers, and inadequate health literacy and education may impede URMs' access to clinical trials and medical care. Clinical trials' enrollment sites often pose transportation barriers and challenges that negatively impact creating a diverse study population. Lack of diversity among a trial population can stem from the stakeholder level, where corporate sponsors of academic readers do not consider diversity in clinical trials a priority due to false cost-benefit assumptions. The funding source may also impact the racial reporting or the results of a given trial. Industry-based trials have always been criticized for over-representing non-Hispanic White populations, driven by the desire to reach high completion rates with minimum financial burdens. Real efforts are warranted to ensure adequate minorities' representation in the PAD clinical trials and to the process toward the ultimate goal of developing more durable and effective PAD treatments that fit the needs of real-world populations.

Translational Relevance of Advanced Age and Atherosclerosis in Preclinical Trials of Biotherapies for Peripheral Artery Disease

Approximately 6% of adults worldwide suffer from peripheral artery disease (PAD), primarily caused by atherosclerosis of lower limb arteries. Despite optimal medical care and revascularization, many PAD patients remain symptomatic and progress to critical limb ischemia (CLI) and risk major amputation. Delivery of pro-angiogenic factors as proteins or DNA, stem, or progenitor cells confers vascular regeneration and functional recovery in animal models of CLI, but the effects are not well replicated in patients and no pro-angiogenic biopharmacological procedures are approved in the US, EU, or China. The reasons are unclear, but animal models that do not represent clinical PAD/CLI are implicated. Consequently, it is unclear whether the obstacles to clinical success lie in the toxic biochemical milieu of human CLI, or in procedures that were optimized on inappropriate models. The question is significant because the former case requires abandonment of current strategies, while the latter encourages continued optimization. These issues are discussed in the context of relevant preclinical and clinical data, and it is concluded that preclinical mouse models that include age and atherosclerosis as the only comorbidities that are consistently present and active in clinical trial patients are necessary to predict clinical success. Of the reviewed materials, no biopharmacological procedure that failed in clinical trials had been tested in animal models that included advanced age and atherosclerosis relevant to PAD/CLI.

Complementary Gene Therapy after Revascularization with the Saphenous Vein in Diabetic Foot Syndrome

Diabetic foot syndrome (DFS) is one of the most serious macroangiopathic complications of diabetes. The primary treatment option is revascularization, but complementary therapies are still being sought. The study group consisted of 18 patients diagnosed with ischemic ulcerative and necrotic lesions in DFS. Patients underwent revascularization procedures and, due to unsatisfactory healing of the lesions, were randomly allocated to two groups: a group in which bicistronic VEGF165/HGF plasmid was administered and a control group in which saline placebo was administered. Before gene therapy administration and after 7, 30, 90, and 180 days, color duplex ultrasonography (CDU) was performed, the ankle-brachial index (ABI) and transcutaneous oxygen pressure (TcPO2) were measured, and DFS changes were described and documented photographically. In the gene therapy group, four out of eight patients (50%) healed their DFS lesions before 12 weeks. During this time, the ABI increased by an average of 0.25 and TcPO2 by 30.4 mmHg. In the control group, healing of the lesions by week 12 occurred in six out of nine patients (66.67%), and the ABI increased by an average of 0.14 and TcPO2 by 27.1 mmHg. One major amputation occurred in each group. Gene therapy may be an attractive option for complementary treatment in DFS.

Developmental endothelial locus-1 in cardiovascular and metabolic diseases: A promising biomarker and therapeutic target

Cardiovascular and metabolic diseases (CVMDs) are a leading cause of death worldwide and impose a major socioeconomic burden on individuals and healthcare systems, underscoring the urgent need to develop new drug therapies. Developmental endothelial locus-1 (DEL-1) is a secreted multifunctional domain protein that can bind to integrins and play an important role in the occurrence and development of various diseases. Recently, DEL-1 has attracted increased interest for its pharmacological role in the treatment and/or management of CVMDs. In this review, we present the current knowledge on the predictive and therapeutic role of DEL-1 in a variety of CVMDs, such as atherosclerosis, hypertension, cardiac remodeling, ischemic heart disease, obesity, and insulin resistance. Collectively, DEL-1 is a promising biomarker and therapeutic target for CVMDs.

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.

Molecular Mechanisms Associated with ROS-Dependent Angiogenesis in Lower Extremity Artery Disease

Currently, atherosclerosis, which affects the vascular bed of all vital organs and tissues, is considered as a leading cause of death. Most commonly, atherosclerosis involves coronary and peripheral arteries, which results in acute (e.g., myocardial infarction, lower extremities ischemia) or chronic (persistent ischemia leading to severe heart failure) consequences. All of them have a marked unfavorable impact on the quality of life and are associated with increased mortality and morbidity in human populations. Lower extremity artery disease (LEAD, also defined as peripheral artery disease, PAD) refers to atherosclerotic occlusive disease of the lower extremities, where partial or complete obstruction of peripheral arteries is observed. Decreased perfusion can result in ischemic pain, non-healing wounds, and ischemic ulcers, and significantly reduce the quality of life. However, the progressive atherosclerotic changes cause stimulation of tissue response processes, like vessel wall remodeling and neovascularization. These mechanisms of adapting the vascular network to pathological conditions seem to play a key role in reducing the impact of the changes limiting the flow of blood. Neovascularization as a response to ischemia induces sprouting and expansion of the endothelium to repair and grow the vessels of the circulatory system. Neovascularization consists of three different biological processes: vasculogenesis, angiogenesis, and arteriogenesis. Both molecular and environmental factors that may affect the process of development and growth of blood vessels were analyzed. Particular attention was paid to the changes taking place during LEAD. It is important to consider the molecular mechanisms underpinning vessel growth. These mechanisms will also be examined in the context of diseases commonly affecting blood vessel function, or those treatable in part by manipulation of angiogenesis. Furthermore, it may be possible to induce the process of blood vessel development and growth to treat peripheral vascular disease and wound healing. Reactive oxygen species (ROS) play an important role in regulation of essential cellular signaling pathways such as cell differentiation, proliferation, migration and apoptosis. With regard to the repair processes taking place during diseases such as LEAD, prospective therapeutic methods have been described that could significantly improve the treatment of vessel diseases in the future. Summarizing, regenerative medicine holds the potential to transform the therapeutic methods in heart and vessel diseases treatment.

MicroRNA-615-5p Regulates Angiogenesis and Tissue Repair by Targeting AKT/eNOS (Protein Kinase B/Endothelial Nitric Oxide Synthase) Signaling in Endothelial Cells

Objective- In response to tissue injury, the appropriate progression of events in angiogenesis is controlled by a careful balance between pro and antiangiogenic factors. We aimed to identify and characterize microRNAs that regulate angiogenesis in response to tissue injury. Approach and Results- We show that in response to tissue injury, microRNA-615-5p (miR-615-5p) is rapidly induced and serves as an antiangiogenic microRNA by targeting endothelial cell VEGF (vascular endothelial growth factor)-AKT (protein kinase B)/eNOS (endothelial nitric oxide synthase) signaling in vitro and in vivo. MiR-615-5p expression is increased in wounds of diabetic db/db mice, in plasma of human subjects with acute coronary syndromes, and in plasma and skin of human subjects with diabetes mellitus. Ectopic expression of miR-615-5p markedly inhibited endothelial cell proliferation, migration, network tube formation in Matrigel, and the release of nitric oxide, whereas miR-615-5p neutralization had the opposite effects. Mechanistic studies using transcriptomic profiling, bioinformatics, 3' untranslated region reporter and microribonucleoprotein immunoprecipitation assays, and small interfering RNA dependency studies demonstrate that miR-615-5p inhibits the VEGF-AKT/eNOS signaling pathway in endothelial cells by targeting IGF2 (insulin-like growth factor 2) and RASSF2 (Ras-associating domain family member 2). Local delivery of miR-615-5p inhibitors, markedly increased angiogenesis, granulation tissue thickness, and wound closure rates in db/db mice, whereas miR-615-5p mimics impaired these effects. Systemic miR-615-5p neutralization improved skeletal muscle perfusion and angiogenesis after hindlimb ischemia in db/db mice. Finally, modulation of miR-615-5p expression dynamically regulated VEGF-induced AKT signaling and angiogenesis in human skin organoids as a model of tissue injury. Conclusions- These findings establish miR-615-5p as an inhibitor of VEGF-AKT/eNOS-mediated endothelial cell angiogenic responses and that manipulating miR-615-5p expression could provide a new target for angiogenic therapy in response to tissue injury. Visual Overview- An online visual overview is available for this article.

MicroRNA-135a-3p regulates angiogenesis and tissue repair by targeting p38 signaling in endothelial cells

Angiogenesis is a critical process in repair of tissue injury that is regulated by a delicate balance between pro- and antiangiogenic factors. In disease states associated with impaired angiogenesis, we identified that miR-135a-3p is rapidly induced and serves as an antiangiogenic microRNA (miRNA) by targeting endothelial cell (EC) p38 signaling in vitro and in vivo. MiR-135a-3p overexpression significantly inhibited EC proliferation, migration, and network tube formation in matrigel, whereas miR-135-3p neutralization had the opposite effects. Mechanistic studies using transcriptomic profiling, bioinformatics, 3'-UTR reporter and miRNA ribonucleoprotein complex -immunoprecipitation assays, and small interfering RNA dependency studies revealed that miR-135a-3p inhibits the p38 signaling pathway in ECs by targeting huntingtin-interacting protein 1 (HIP1). Local delivery of miR-135a-3p inhibitors to wounds of diabetic db/db mice markedly increased angiogenesis, granulation tissue thickness, and wound closure rates, whereas local delivery of miR-135a-3p mimics impaired these effects. Finally, through gain- and loss-of-function studies in human skin organoids as a model of tissue injury, we demonstrated that miR-135a-3p potently modulated p38 signaling and angiogenesis in response to VEGF stimulation by targeting HIP1. These findings establish miR-135a-3p as a pivotal regulator of pathophysiological angiogenesis and tissue repair by targeting a VEGF-HIP1-p38K signaling axis, providing new targets for angiogenic therapy to promote tissue repair.-Icli, B., Wu, W., Ozdemir, D., Li, H., Haemmig, S., Liu, X., Giatsidis, G., Cheng, H. S., Avci, S. N., Kurt, M., Lee, N., Guimaraes, R. B., Manica, A., Marchini, J. F., Rynning, S. E., Risnes, I., Hollan, I., Croce, K., Orgill, D. P., Feinberg, M. W. MicroRNA-135a-3p regulates angiogenesis and tissue repair by targeting p38 signaling in endothelial cells.

Non-viral Vector for Muscle-Mediated Gene Therapy

Non-viral gene delivery to skeletal muscle was one of the first applications of gene therapy that went into the clinic, mainly because skeletal muscle is an easily accessible tissue for local gene transfer and non-viral vectors have a relatively safe and low immunogenic track record. However, plasmid DNA, naked or complexed to the various chemistries, turn out to be moderately efficient in humans when injected locally and very inefficient (and very toxic in some cases) when injected systemically. A number of clinical applications have been initiated however, based on transgenes that were adapted to good local impact and/or to a wide physiological outcome (i.e., strong humoral and cellular immune responses following the introduction of DNA vaccines). Neuromuscular diseases seem more challenging for non-viral vectors. Nevertheless, the local production of therapeutic proteins that may act distantly from the injected site and/or the hydrodynamic perfusion of safe plasmids remains a viable basis for the non-viral gene therapy of muscle disorders, cachexia, as well as peripheral neuropathies.

Gene therapy for peripheral arterial disease

BACKGROUND

Peripheral arterial disease (PAD), caused by narrowing of the arteries in the limbs, is increasing in incidence and prevalence as our population is ageing and as diabetes is becoming more prevalent. PAD can cause pain in the limbs while walking, known as intermittent claudication, or can be more severe and cause pain while at rest, ulceration, and ultimately gangrene and limb loss. This more severe stage of PAD is known as 'critical limb ischaemia'. Treatments for PAD include medications that help to reduce the increased risk of cardiovascular events and help improve blood flow, as well as endovascular or surgical repair or bypass of the blocked arteries. However, many people are unresponsive to medications and are not suited to surgical or endovascular treatment, leaving amputation as the last option. Gene therapy is a novel approach in which genetic material encoding for proteins that may help increase revascularisation is injected into the affected limbs of patients. This type of treatment has been shown to be safe, but its efficacy, especially regarding ulcer healing, effects on quality of life, and other symptomatic outcomes remain unknown.

OBJECTIVES

To assess the effects of gene therapy for symptomatic peripheral arterial disease.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched Cochrane CENTRAL, the Cochrane Vascular Specialised Register, MEDLINE Ovid, Embase Ovid, CINAHL, and AMED, along with trials registries (all searched 27 November 2017). We also checked reference lists of included studies and systematic reviews for further studies.

SELECTION CRITERIA

We included randomised and quasi-randomised studies that evaluated gene therapy versus no gene therapy in people with PAD. We excluded studies that evaluated direct growth hormone treatment or cell-based treatments.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected studies, performed quality assessment, and extracted data from the included studies. We collected pertinent information on each study, as well as data for the outcomes of amputation-free survival, ulcer healing, quality of life, amputation, all-cause mortality, ankle brachial index, symptom scores, and claudication distance.

MAIN RESULTS

We included in this review a total of 17 studies with 1988 participants (evidence current until November 2017). Three studies limited their inclusion to people with intermittent claudication, 12 limited inclusion to people with varying levels of critical limb ischaemia, and two included people with either condition. Study investigators evaluated many different types of gene therapies, using different protocols. Most studies evaluated growth factor-encoding gene therapy, with six studies using vascular endothelial growth factor (VEGF)-encoding genes, four using hepatocyte growth factor (HGF)-encoding genes, and three using fibroblast growth factor (FGF)-encoded genes. Two studies evaluated hypoxia-inducible factor 1-alpha (HIF-1α) gene therapy, one study used a developmental endothelial locus-1 gene therapy, and the final study evaluated a stromal cell-derived factor-1 (SDF-1) gene therapy. Most studies reported outcomes after 12 months of follow-up, but follow-up ranged from three months to two years.Overall risk of bias varied between studies, with many studies not providing sufficient detail for adequate determination of low risk of bias for many domains. Two studies did not utilise a placebo control, leading to risk of performance bias. Several studies reported in previous protocols or in their Methods sections that they would report on certain outcomes for which no data were then reported, increasing risk of reporting bias. All included studies reported sponsorships from corporate entities that led to unclear risk of other bias. The overall quality of evidence ranged from moderate to very low, generally as the result of heterogeneity and imprecision, with few or no studies reporting on outcomes.Evidence suggests no clear differences for the outcomes of amputation-free survival, major amputation, and all-cause mortality between those treated with gene therapy and those not receiving this treatment (all moderate-quality evidence). Low-quality evidence suggests improvement in complete ulcer healing with gene therapy (odds ratio (OR) 2.16, 95% confidence interval (CI) 1.02 to 4.59; P = 0.04). We could not combine data on quality of life and can draw no conclusions at this time regarding this outcome (very low-quality evidence). We included one study in the meta-analysis for ankle brachial index, which showed no clear differences between treatments, but we can draw no overall association (low-quality evidence). We combined in a meta-analysis pain symptom scores as assessed by visual analogue scales from two studies and found no clear differences between treatment groups (very low-quality evidence). We carried out extensive subgroup analyses by PAD classification, dosage schedule, vector type, and gene used but identified no substantial differences.

AUTHORS' CONCLUSIONS

Moderate-quality evidence shows no clear differences in amputation-free survival, major amputation, and all-cause mortality between those treated with gene therapy and those not receiving gene therapy. Some evidence suggests that gene therapy may lead to improved complete ulcer healing, but this outcome needs to be explored with improved reporting of the measure, such as decreased ulcer area in cm², and better description of ulcer types and healing. Further standardised data that are amenable to meta-analysis are needed to evaluate other outcomes such as quality of life, ankle brachial index, symptom scores, and claudication distance.

PEO-PPO-PEO Tri-Block Copolymers for Gene Delivery Applications in Human Regenerative Medicine-An Overview

Lineal (poloxamers or Pluronic^®) or X-shaped (poloxamines or Tetronic^®) amphiphilic tri-block copolymers of poly(ethylene oxide) and poly(propylene oxide) (PEO-PPO-PEO) have been broadly explored for controlled drug delivery in different regenerative medicine approaches. The ability of these copolymers to self-assemble as micelles and to undergo sol-to-gel transitions upon heating has endowed the denomination of “smart” or “intelligent” systems. The use of PEO-PPO-PEO copolymers as gene delivery systems is a powerful emerging strategy to improve the performance of classical gene transfer vectors. This review summarizes the state of art of the application of PEO-PPO-PEO copolymers in both nonviral and viral gene transfer approaches and their potential as gene delivery systems in different regenerative medicine approaches.

Stem cell-based peripheral vascular regeneration

Chronic critical limb ischemia (CLI) represents an end-stage manifestation of peripheral arterial disease (PAD). CLI patients are at very high risk of amputation and cardiovascular complications, leading to severe morbidity and mortality. Because many patients with CLI are ineligible for conventional revascularization procedures, it is urgently needed to explore alternative strategies to improve blood supply in the ischemic tissue. Although researchers initially focused on gene/protein therapy using proangiogenic growth factors/cytokines, recent discovery of somatic stem/progenitor cells including bone marrow (BM)-derived endothelial progenitor cells (EPCs) and mesenchymal stem cells (MSCs) has drastically developed the field of therapeutic angiogenesis for CLI. Overall, early phase clinical trials demonstrated that stem/progenitor cell therapies may be safe, feasible and potentially effective. However, only few late-phase clinical trials have been conducted. This review provides an overview of the preclinical and clinical reports to demonstrate the usefulness and the current limitations of the cell-based therapies.

Growth factors for angiogenesis in peripheral arterial disease

BACKGROUND

Peripheral artery disease (PAD) is associated with a high clinical and socioeconomic burden. Treatments to alleviate the symptoms of PAD and decrease the risks of amputation and death are a high societal priority. A number of growth factors have shown a potential to stimulate angiogenesis. Growth factors delivered directly (as recombinant proteins), or indirectly (e.g. by viral vectors or DNA plasmids encoding these factors), have emerged as a promising strategy to treat patients with PAD.

OBJECTIVES

To assess the effects of growth factors that promote angiogenesis for treating people with PAD of the lower extremities.

SEARCH METHODS

The Cochrane Vascular Information Specialist searched the Specialised Register (June 2016) and CENTRAL (2016, Issue 5). We searched trial registries for details of ongoing or unpublished studies. We also checked the reference lists of relevant publications and, if necessary, tried to contact the trialists for details of the studies.

SELECTION CRITERIA

We included randomised controlled trials comparing growth factors (delivered directly or indirectly) with no intervention, placebo or any other intervention not based on the growth factor's action in patients with PAD of the lower extremities. The primary outcomes were limb amputation, death and adverse events. The secondary outcomes comprised walking ability, haemodynamic measures, ulceration and rest pain.

DATA COLLECTION AND ANALYSIS

Two review authors independently selected trials and assessed the risk of bias. We used outcomes of the studies at low risk of bias for the main analysis and of all studies in the sensitivity analyses. We calculated odds ratios (OR) for dichotomous outcomes and mean differences for continuous outcomes with 95% confidence intervals (CI). We evaluated statistical heterogeneity using the I2 statistic and Cochrane's Q test. We conducted meta-analysis for the overall effect and for each growth factor as a subgroup analysis using OR in a fixed-effect model. We evaluated the robustness of the results in a sensitivity analysis using risk ratio (RR) and/or a random-effects model. We also assessed the quality of the evidence for each outcome.

MAIN RESULTS

We included 20 trials in the review and used 14 studies (on approximately 1400 participants) with published results in the analyses. Six published studies compared fibroblast growth factors (FGF), four studies hepatocyte growth factors (HGF) and another four studies vascular endothelial growth factors (VEGF), versus placebo or no therapy. Six of these studies exclusively or mainly investigated participants with intermittent claudication and eight studies exclusively participants with critical limb ischaemia. Follow-up generally ranged from three months to one year. Two small studies provided some data at 2 years and one of them also at 10 years.The direction and size of effects for growth factors on major limb amputations (OR 0.99, 95% CI 0.71 to 1.38; 10 studies, N = 1075) and death (OR 0.99, 95% CI 0.69 to 1.41; 12 studies, N = 1371) at up to two years are uncertain. The quality of the evidence is low due to risk of bias and imprecision (at one year, moderate-quality evidence due to imprecision). However, growth factors may decrease the rate of any limb amputations (OR 0.56, 95% CI 0.31 to 0.99; 6 studies, N = 415). The quality of the evidence is low due to risk of bias and selective reporting.The direction and size of effects for growth factors on serious adverse events (OR 1.09, 95% CI 0.79 to 1.50; 13 studies, N = 1411) and on any adverse events (OR 1.10, 95% CI 0.73 to 1.64; 4 studies, N = 709) at up to two years are also uncertain. The quality of the evidence is low due to risk of bias and imprecision (for serious adverse events at one year, moderate-quality evidence due to imprecision).Growth factors may improve haemodynamic measures (low-quality evidence), ulceration (very low-quality evidence) and rest pain (very low-quality evidence) up to one year, but they have little or no effect on walking ability (low-quality evidence). We did not identify any relevant differences in effects between growth factors (FGF, HGF and VEGF).

AUTHORS' CONCLUSIONS

The results of this review do not support the use of therapy with the growth factors FGF, HGF or VEGF in people with PAD of the lower extremities to prevent death or major limb amputation or to improve walking ability. However, the use of these growth factors may improve haemodynamic measures and decrease the rate of any limb amputations (probably due to preventing minor amputations) with an uncertain effect on adverse events; an improvement of ulceration and rest pain is very uncertain. New trials at low risk of bias are needed to generate evidence with more certainty.

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.

Cardiovascular Gene Therapy: Past, Present, and Future

Cardiovascular diseases remain a large global health problem. Although several conventional small-molecule treatments are available for common cardiovascular problems, gene therapy is a potential treatment option for acquired and inherited cardiovascular diseases that remain with unmet clinical needs. Among potential targets for gene therapy are severe cardiac and peripheral ischemia, heart failure, vein graft failure, and some forms of dyslipidemias. The first approved gene therapy in the Western world was indicated for lipoprotein lipase deficiency, which causes high plasma triglyceride levels. With improved gene delivery methods and more efficient vectors, together with interventional transgene strategies aligned for a better understanding of the pathophysiology of these diseases, new approaches are currently tested for safety and efficacy in clinical trials. In this article, we integrate a historical perspective with recent advances that will likely affect clinical development in this research area.

Endogenous developmental endothelial locus-1 limits ischaemia-related angiogenesis by blocking inflammation

We have recently identified endothelial cell-secreted developmental endothelial locus-1 (Del-1) as an endogenous inhibitor of β2-integrin-dependent leukocyte infiltration. Del-1 was previously also implicated in angiogenesis. Here, we addressed the role of endogenously produced Del-1 in ischaemia-related angiogenesis. Intriguingly, Del-1-deficient mice displayed increased neovascularisation in two independent ischaemic models (retinopathy of prematurity and hind-limb ischaemia), as compared to Del-1-proficient mice. On the contrary, angiogenic sprouting in vitro or ex vivo (aortic ring assay) and physiological developmental retina angiogenesis were not affected by Del-1 deficiency. Mechanistically, the enhanced ischaemic neovascularisation in Del-1-deficiency was linked to higher infiltration of the ischaemic tissue by CD45+ haematopoietic and immune cells. Moreover, Del-1-deficiency promoted β2-integrin-dependent adhesion of haematopoietic cells to endothelial cells in vitro, and the homing of hematopoietic progenitor cells and of immune cell populations to ischaemic muscles in vivo. Consistently, the increased hind limb ischaemia-related angiogenesis in Del-1 deficiency was completely reversed in mice lacking both Del-1 and the β2-integrin LFA-1. Additionally, enhanced retinopathy-associated neovascularisation in Del-1-deficient mice was reversed by LFA-1 blockade. Our data reveal a hitherto unrecognised function of endogenous Del-1 as a local inhibitor of ischaemia-induced angiogenesis by restraining LFA-1-dependent homing of pro-angiogenic haematopoietic cells to ischaemic tissues. Our findings are relevant for the optimisation of therapeutic approaches in the context of ischaemic diseases.

Vascular Regeneration in Ischemic Hindlimb by Adeno-Associated Virus Expressing Conditionally Silenced Vascular Endothelial Growth Factor

BACKGROUND

Critical limb ischemia (CLI) is the extreme manifestation of peripheral artery disease, a major unmet clinical need for which lower limb amputation is the only option for many patients. After 2 decades in development, therapeutic angiogenesis has been tested clinically via intramuscular delivery of proangiogenic proteins, genes, and stem cells. Efficacy has been modest to absent, and the largest phase 3 trial of gene therapy for CLI reported a worsening trend of plasmid fibroblast growth factor. In all clinical trials to date, gene therapy has used unregulated vectors with limited duration of expression. Only unregulated extended expression vectors such as adeno-associated virus (AAV) and lentivirus have been tested in preclinical models.

METHODS AND RESULTS

We present preclinical results of ischemia (hypoxia)-regulated conditionally silenced (CS) AAV-human vascular endothelial growth factor (hVEGF) gene delivery that shows efficacy and safety in a setting where other strategies fail. In a BALB/c mouse model of CLI, we show that gene therapy with AAV-CS-hVEGF, but not unregulated AAV or plasmid, vectors conferred limb salvage, protection from necrosis, and vascular regeneration when delivered via intramuscular or intra-arterial routes. All vector treatments conferred increased capillary density, but organized longitudinal arteries were selectively generated by AAV-CS-hVEGF. AAV-CS-hVEGF therapy reversibly activated angiogenic and vasculogenic genes, including Notch, SDF1, Angiopoietin, and Ephrin-B2. Reoxygenation extinguished VEGF expression and inactivated the program with no apparent adverse side effects.

CONCLUSIONS

Restriction of angiogenic growth factor expression to regions of ischemia supports the safe and stable reperfusion of hindlimbs in a clinically relevant murine model of CLI.

Evaluation of the clinical relevance and limitations of current pre-clinical models of peripheral artery disease

Peripheral artery disease (PAD) has recognized treatment deficiencies requiring the discovery of novel interventions. This article describes current animal models of PAD and discusses their advantages and disadvantages. There is a need for models which more directly simulate the characteristics of human PAD, such as acute-on-chronic presentation, presence of established risk factors and impairment of physical activity.

Phase I study of multi-gene cell therapy in patients with peripheral artery disease

Alternative treatment strategies for claudication are needed and cell-based therapies designed to induce angiogenesis are promising. The purpose of this report was to conduct a Phase I safety, dose-escalating, non-randomized, open-label study of autologous, fully differentiated venous endothelial and smooth muscle cells called MultiGeneAngio (MGA) for claudication due to peripheral artery disease. Twelve subjects, at two centers, received a single intra-arterial infusion of a suspension of equal amounts of transduced autologous venous smooth muscle cells expressing vascular endothelial growth factor (VEGF165) and endothelial cells expressing angiopoietin-1 (Ang-1) (Cohort 1: 1 × 10(7), Cohort 2: 2 × 10(7), Cohort 3: 5 × 10(7), Cohort 4: 7 × 10(7)). The treatment was given unblinded and in the more symptomatic lower extremity. Transduced cells were tested for in vitro doubling time, telomerase activity, and gene expression. The main outcomes were clinical safety and tolerability. Other safety measures included ankle-brachial index (ABI) and walking time on a treadmill. All subjects were male (mean age 60 ± 5 years) including 25% with diabetes mellitus. At 1-year follow-up, there was one serious adverse event possibly related to MGA. Safety endpoints including VEGF and Ang-1 plasma protein levels were within normal ranges in all subjects. The mean maximal walking time increased from baseline to 1 year and the index limb ABI was unchanged, indicating no safety concerns. MGA, an autologous, transduced, cell-based therapy was well tolerated and safe in this Phase I study. Further evaluation is warranted in randomized human studies.

CLINICAL TRIAL REGISTRATION

ClinicalTrials.gov Identifier: NCT00390767.

Modulating the vascular response to limb ischemia: angiogenic and cell therapies

The age-adjusted prevalence of peripheral arterial disease in the US population has been estimated to approach 12%. The clinical consequences of occlusive peripheral arterial disease include pain on walking (claudication), pain at rest, and loss of tissue integrity in the distal limbs; the latter may ultimately lead to amputation of a portion of the lower extremity. Surgical bypass techniques and percutaneous catheter-based interventions may successfully reperfuse the limbs of certain patients with peripheral arterial disease. In many patients, however, the anatomic extent and distribution of arterial occlusion is too severe to permit relief of pain and healing of ischemic ulcers. No effective medical therapy is available for the treatment of such patients, for many of whom amputation represents the only hope for alleviation of symptoms. The ultimate failure of medical treatment and procedural revascularization in significant numbers of patients has led to attempts to develop alternative therapies for ischemic disease. These strategies include administration of angiogenic cytokines, either as recombinant protein or as gene therapy, and more recently, to investigations of stem/progenitor cell therapy. The purpose of this review is to provide an outline of the preclinical basis for angiogenic and stem cell therapies, review the clinical research that has been done, summarize the lessons learned, identify gaps in knowledge, and suggest a course toward successfully addressing an unmet medical need in a large and growing patient population.

pCMV-vegf165 Intramuscular Gene Transfer is an Effective Method of Treatment for Patients With Chronic Lower Limb Ischemia

Effective treatment of chronic lower limb ischemia is one of the most challenging issues confronting vascular surgeons. There are a number of choices available to the vascular surgeon. Open or endovascular revascularization is the treatment of choice when applicable. Current pharmacological therapies play an auxiliary role and cannot prevent disease progression. Therefore, new methods of treatment are needed. We conducted a phase 2b/3 multicenter randomized controlled clinical trial of the intramuscular transfer of a plasmid DNA encoding vascular endothelial growth factor (VEGF) 165 with cytomegalovirus promotor (CMV) in patients with atherosclerotic lower limb ischemia. A total of 100 patients were enrolled in the study, that is, 75 patients were randomized into the test group and received 2 intramuscular injections of 1.2 mg of pCMV-vegf165, 14 days apart together with standard pharmacological treatment. In all, 25 patients were randomized into the control group and received standard treatment only. The following end points were evaluated within the first 6 months of the study and during a 1.5-year additional follow-up period: pain-free walking distance (PWD), ankle-brachial index (ABI), and blood flow velocity (BFV). The pCMV-vegf165 therapy appeared to be significantly more effective than standard treatment. The PWD increased in the test group by 110.4%, 167.2%, and 190.8% at 6 months, 1 year, and 2 years after treatment, respectively. The pCMV-vegf165 intramuscular transfer caused a statistically significant increase in ABI and BFV. There were no positive results in the control group. Thus, pCMV-vegf165 intramuscular gene transfer is an effective method of treatment of moderate to severe claudication due to chronic lower limb ischemia.

Pharmacology in peripheral arterial disease: what the interventional radiologist needs to know

Peripheral arterial disease (PAD) is a progressive disease with significant morbidity and mortality. Risk factor control, using diet and lifestyle modification, exercise, and pharmacological methods, improves symptoms and reduces associated cardiovascular events in these patients. Antiplatelet agents and anticoagulants may be used to reduce the incidence of acute events related to thrombosis. The armamentarium available for symptom relief and disease modification is discussed. Novel treatments such as therapeutic angiogenesis are in their evolutionary phase with promising preclinical data.

Collateral vessel number, plaque burden, and functional decline in peripheral artery disease

Associations of collateral vessels and lower extremity plaque with functional decline are unknown. Among people with peripheral artery disease (PAD), we determined whether greater superficial femoral artery (SFA) plaque burden combined with fewer lower extremity collateral vessels was associated with faster functional decline, compared to less plaque and/or more numerous collateral vessels. A total of 226 participants with ankle-brachial index (ABI) <1.00 underwent magnetic resonance imaging of lower extremity collateral vessels and cross-sectional imaging of the proximal SFA. Participants were categorized as follows: Group 1 (best), maximum plaque area < median and collateral vessel number ≥6 (median); Group 2, maximum plaque area < median and collateral vessel number <6; Group 3, maximum plaque area > median and collateral vessel number ≥6; Group 4 (worst), maximum plaque area > median and collateral vessel number <6. Functional measures were performed at baseline and annually for 2 years. Analyses adjust for age, sex, race, comorbidities, and other confounders. Annual changes in usual-paced walking velocity were: Group 1, +0.01 m/s; Group 2, -0.02 m/s; Group 3, -0.01 m/s; Group 4, -0.05 m/s (p-trend=0.008). Group 4 had greater decline than Group 1 (p<0.001), Group 2 (p=0.029), and Group 3 (p=0.010). Similar trends were observed for fastest-paced 4-meter walking velocity (p-trend=0.018). Results were not substantially changed when analyses were repeated with additional adjustment for ABI. However, there were no associations of SFA plaque burden and collateral vessel number with decline in 6-minute walk. In summary, a larger SFA plaque burden combined with fewer collateral vessels is associated with a faster decline in usual and fastest-paced walking velocity in PAD.

Therapeutic site selection is important for the successful development of collateral vessels

BACKGROUND

Induction of collateral development to improve tissue perfusion is a promising approach for the treatment of arterial occlusive diseases. Several growth factors and cells have been reported to increase collateral circulation; however, the appropriate site for the delivery of these factors and cells is unclear. In this study, we identified the delivery site for growth factor in a rabbit model of limb ischemia and evaluated whether specific delivery of basic fibroblast growth factor (bFGF) to this site enhanced collateral augmentation.

METHODS

The left femoral artery of Japanese white rabbits was excised to induce limb ischemia. Twenty-eight days thereafter, angiograms were obtained to identify the typical pattern of collateral development in this model. Subsequently, bFGF (100 μg) was selectively injected into the left coccygeofemoral muscle (coccygeo group) or adductor muscle (adductor group), major thigh muscles in proximity. Collateral development was evaluated at 28 days after injection, and its mechanism was assessed by immunologic and morphometric analyses of muscle samples.

RESULTS

Angiographic evaluation of this model revealed that after femoral artery excision, collateral vessels generally developed in the left coccygeofemoral muscle, whereas few collateral vessels were detected in the left adductor muscle. At 28 days after injection, calf blood pressure ratio, defined as left pressure to right pressure, was significantly higher in the coccygeo group than in the adductor group (0.85 ± 0.05 vs 0.69 ± 0.05, respectively; P < .01). Similar results were observed in blood flow through the internal iliac artery (resting: 24.6 ± 6.1 vs 17.4 ± 8.0 mL/min, P < .01; maximum: 47.4 ± 12.3 vs 33.2 ± 10.7 mL/min, P < .01) and in the angiographic score (0.67 ± 0.13 vs 0.39 ± 0.11; P < .01). Immunologic analyses of the coccygeofemoral muscle at day 3 showed marked expressions of Ki-67, monocyte chemotactic protein 1, and FGF receptor 1 in the coccygeo group compared with the adductor group. Morphometric analyses of the same muscle at day 14 also revealed that collateral vessel density and wall thickness were significantly increased in the coccygeal group compared with the adductor group.

CONCLUSIONS

These findings demonstrated that selective bFGF delivery to the coccygeofemoral muscle markedly improved collateral development and limb perfusion compared with delivery to the adductor muscle, suggesting that site selection is important in increasing therapeutic efficacy.

Postischemic revascularization: from cellular and molecular mechanisms to clinical applications

After the onset of ischemia, cardiac or skeletal muscle undergoes a continuum of molecular, cellular, and extracellular responses that determine the function and the remodeling of the ischemic tissue. Hypoxia-related pathways, immunoinflammatory balance, circulating or local vascular progenitor cells, as well as changes in hemodynamical forces within vascular wall trigger all the processes regulating vascular homeostasis, including vasculogenesis, angiogenesis, arteriogenesis, and collateral growth, which act in concert to establish a functional vascular network in ischemic zones. In patients with ischemic diseases, most of the cellular (mainly those involving bone marrow-derived cells and local stem/progenitor cells) and molecular mechanisms involved in the activation of vessel growth and vascular remodeling are markedly impaired by the deleterious microenvironment characterized by fibrosis, inflammation, hypoperfusion, and inhibition of endogenous angiogenic and regenerative programs. Furthermore, cardiovascular risk factors, including diabetes, hypercholesterolemia, hypertension, diabetes, and aging, constitute a deleterious macroenvironment that participates to the abrogation of postischemic revascularization and tissue regeneration observed in these patient populations. Thus stimulation of vessel growth and/or remodeling has emerged as a new therapeutic option in patients with ischemic diseases. Many strategies of therapeutic revascularization, based on the administration of growth factors or stem/progenitor cells from diverse sources, have been proposed and are currently tested in patients with peripheral arterial disease or cardiac diseases. This review provides an overview from our current knowledge regarding molecular and cellular mechanisms involved in postischemic revascularization, as well as advances in the clinical application of such strategies of therapeutic revascularization.

Therapeutic angiogenesis for revascularization in peripheral artery disease

Therapeutic angiogenesis for peripheral artery disease (PAD), achieved by gene and cell therapy, has recently raised a great deal of hope for patients who cannot undergo standard revascularizing treatment. Although pre-clinical studies gave very promising data, still clinical trials of gene therapy have not provided satisfactory results. On the other hand, cell therapy approach, despite several limitations, demonstrated more beneficial effects but initial clinical studies must be constantly validated by larger randomized, multi-center, double-blinded, placebo-controlled trials. This review focuses on previous and recent gene and cell therapy studies for limb ischemia, including both experimental and clinical research, and summarizes some important papers published in this field. Moreover, it provides a short comment on combined gene and cell therapy approach on the example of heme oxygenase-1 overexpressing cells with therapeutic properties.

DVC1-0101 to treat peripheral arterial disease: a Phase I/IIa open-label dose-escalation clinical trial

We here report the results of a Phase I/IIa open-label four dose-escalation clinical study assessing the safety, tolerability, and possible therapeutic efficacy of a single intramuscular administration of DVC1-0101, a new gene transfer vector based on a nontransmissible recombinant Sendai virus (rSeV) expressing the human fibroblast growth factor-2 (FGF-2) gene (rSeV/dF-hFGF2), in patients with peripheral arterial disease (PAD). Gene transfer was done in 12 limbs of 12 patients with rest pain, and three of them had ischemic ulcer(s). No cardiovascular or other serious adverse events (SAEs) caused by gene transfer were detected in the patients over a 6-month follow-up. No infectious viral particles, as assessed by hemagglutination activity, were detected in any patient during the study. No representative elevation of proinflammatory cytokines or plasma FGF-2 was seen. Significant and continuous improvements in Rutherford category, absolute claudication distance (ACD), and rest pain were observed (P < 0.05 to 0.01). To the best of our knowledge, this is the first clinical trial of the use of a gene transfer vector based on rSeV. The single intramuscular administration of DVC1-0101 to PAD patients was safe and well tolerated, and resulted in significant improvements of limb function. Larger pivotal studies are warranted as a next step.

X-ray-visible microcapsules containing mesenchymal stem cells improve hind limb perfusion in a rabbit model of peripheral arterial disease

The therapeutic goal in peripheral arterial disease (PAD) patients is to restore blood flow to ischemic tissue. Stem cell transplantation offers a new avenue to enhance arteriogenesis and angiogenesis. Two major problems with cell therapies are poor cell survival and the lack of visualization of cell delivery and distribution. To address these therapeutic barriers, allogeneic bone marrow-derived mesenchymal stem cells (MSCs) were encapsulated in alginate impregnated with a radiopaque contrast agent (MSC-Xcaps). In vitro MSC-Xcap viability by a fluorometric assay was high (96.9% ± 2.7% at 30 days postencapsulation) and as few as 10 Xcaps were visible on clinical x-ray fluoroscopic systems. Using an endovascular PAD model, rabbits (n = 21) were randomized to receive MSC-Xcaps (n = 6), empty Xcaps (n = 5), unencapsulated MSCs (n = 5), or sham intramuscular injections (n = 5) in the ischemic thigh 24 hours postocclusion. Immediately after MSC transplantation and 14 days later, digital radiographs acquired on a clinical angiographic system demonstrated persistent visualization of the Xcap injection sites with retained contrast-to-noise. Using a modified TIMI frame count, quantitative angiography demonstrated a 65% improvement in hind limb perfusion or arteriogenesis in MSC-Xcap-treated animals versus empty Xcaps. Post-mortem immunohistopathology of vessel density by anti-CD31 staining demonstrated an 87% enhancement in angiogenesis in Xcap-MSC-treated animals versus empty Xcaps. MSC-Xcaps represent the first x-ray-visible cellular therapeutic with enhanced efficacy for PAD treatment.

Effect of aspirin versus clopidogrel on walking exercise performance in intermittent claudication-a double-blind randomized multicenter trial

Background

This study sought to determine possible effects of different antiplatelet therapies on walking exercise performance in intermittent claudication. Aspirin, in contrast to clopidogrel, interferes with processes that increase collateral conductance in an ischemic animal model.

Methods and Results

Patients with stable intermittent claudication were recruited from 21 centers in Switzerland and Germany and randomized to either aspirin or clopidogrel treatment. They participated in a 3-month rehabilitation program (electronically monitored, home-based, 1-hour daily walking sessions at a speed of approximately 120 steps/min). Walking distance was assessed by treadmill tests (3.2 km/h; 12% grade) at baseline and after 12 weeks. A total of 229 of 259 patients with a mean age of 66.2±7.7 years completed the study according to the protocol. A total of 24.5% were females, 20.1% diabetics, and 85.6% were active/ex-smokers. The baseline characteristics were a median (interquartile range) ankle/brachial index of 0.69 (0.57±0.8), an initial claudication distance (ICD) of 98 m (70 to 151 m), and an absolute claudication distance (ACD) of 162 m (113 to 302 m). Training resulted in a median increase of initial claudication distance by 33.5 m (33.3%) in the clopidogrel group and 29 m (33.9%) in the aspirin group. The values for absolute claudication distance were 60.5 m (34.9%) and 75 m (35.3%), respectively (p_ICD=0.42 and p_ACD=0.66).

Conclusions

Treatment with aspirin did not show a difference in initial claudication distance or absolute claudication distance improvements compared with clopidogrel after a 3-month walking rehabilitation program. (J Am Heart Assoc. 2012;1:51-56.)

Clinical Trial Registration

URL: http://www.ClinicalTrials.gov. Unique identifier: NCT00189618, URL: https://EudraCT.ema.europa.eu, Unique identifier: 2004-005041-35

Electric pulses augment reporter gene expression in the beating heart

BACKGROUND

Gene therapy of the heart has been attempted in a number of clinical trials with the injection of naked DNA, although quantitative information on myocellular transfection rates is not available. The present study aimed to quantify the efficacy of electropulsing protocols that differ in pulse duration and number to stimulate transfection of cardiomyocytes and to determine the impact on myocardial integrity.

METHODS

Reporter plasmid for constitutive expression of green fluorescent protein (GFP) was injected into the left ventricle of beating hearts of adult, male Lewis rats. Four electrotransfer protocols consisting of repeated long pulses (8 × 20 ms), trains of short pulses (eight trains of either 60 or 80 × 100 µs) or their combination were compared with control procedures concerning the degree of GFP expression and the effect on infiltration, fibrosis and apoptosis.

RESULTS

All tested protocols produced GFP expression at the site of plasmid injection. Continuous pulses were most effective and increased the number of GFP-positive cardiomyocytes by more than 300-fold compared to plasmid injection alone (p < 0.05). Concomitantly, the incidence of macrophage infiltration, fibrosis and cell death was increased. Trains of short pulses reduced macrophage infiltration and fibrosis by four- and two-fold, respectively, although they were 20-fold less efficient in stimulating cardiomyocyte transfection. GFP expression co-related to delivered electric energy, infiltration and fibrosis, although not apoptosis.

CONCLUSIONS

The data imply that electropulsing of the myocardium promotes the overexpression of exogenous protein in mature cardiomyocytes in relation to an injury component. Fractionation of pulses is indicated as a option for sophisticated gene therapeutic approaches to the heart.

Poly(alkylene oxide) copolymers for nucleic acid delivery

The advancement of gene-based therapeutics to the clinic is limited by the ability to deliver physiologically relevant doses of nucleic acids to target tissues safely and effectively. Over the last couple of decades, researchers have successfully employed polymer and lipid based nanoassemblies to deliver nucleic acids for the treatment of a variety of diseases. Results of phase I/II clinical studies to evaluate the efficacy and biosafety of these gene delivery vehicles have been encouraging, which has promoted the design of more efficient and biocompatible systems. Research has focused on designing carriers to achieve biocompatibility, stability in the circulatory system, biodistribution to target the disease site, and intracellular delivery, all of which enhance the resulting therapeutic effect. The family of poly(alkylene oxide) (PAO) polymers includes random, block, and branched structures, among which the ABA type triblocks copolymers of ethylene oxide (EO) and propylene oxide (PO) (commercially known as Pluronic) have received the greatest consideration. In this Account, we highlight examples of polycation-PAO conjugates, liposome-PAO formulations, and PAO micelles for nucleic acid delivery. Among the various polymer design considerations, which include molecular weight of polymer, molecular weight of blocks, and length of blocks, the overall hydrophobic-lipophilic balance (HLB) is a critical parameter in defining the behavior of the polymer conjugates for gene delivery. We discuss the effects of varying this parameter in the context of improving gene delivery processes, such as serum stability and association with cell membranes. Other innovative macromolecular modifications discussed in this category include our work to enhance the serum stability and efficiency of lipoplexes using PAO graft copolymers, the development of a PAO gel-based carrier for sustained and stimuli responsive delivery, and the development of biodegradable PAO-based amphiphilic block copolymers.

Targets and delivery methods for therapeutic angiogenesis in peripheral artery disease

Therapeutic angiogenesis utilizing genetic and cellular modalities in the treatment of arterial obstructive diseases continues to evolve. This is, in part, because the mechanism of vasculogenesis, angiogenesis, and arteriogenesis (the three processes by which the body responds to obstruction of large conduit arteries) is a complex process that is still under investigation. To date, the majority of human trials utilizing molecular, genetic, and cellular modalities for therapeutic angiogenesis in the treatment of peripheral artery disease (PAD) have not shown efficacy. Consequently, the current available knowledge is yet to be translated into novel therapeutic approaches for the treatment of PAD. The aim of this review is to discuss relevant scientific and clinical advances in therapeutic angiogenesis and their potential application in the treatment of ischemic diseases of the peripheral arteries. Additionally, this review article discusses past and recent developments, such as some unconventional approaches that have the potential to be applied as therapeutic targets. The article also includes advances in the delivery of genetic, cellular, and bioactive endothelial growth factors.

Sonic hedgehog-modified human CD34+ cells preserve cardiac function after acute myocardial infarction

RATIONALE

Ischemic cardiovascular disease represents one of the largest epidemics currently facing the aging population. Current literature has illustrated the efficacy of autologous, stem cell therapies as novel strategies for treating these disorders. The CD34+ hematopoetic stem cell has shown significant promise in addressing myocardial ischemia by promoting angiogenesis that helps preserve the functionality of ischemic myocardium. Unfortunately, both viability and angiogenic quality of autologous CD34+ cells decline with advanced age and diminished cardiovascular health.

OBJECTIVE

To offset age- and health-related angiogenic declines in CD34+ cells, we explored whether the therapeutic efficacy of human CD34+ cells could be enhanced by augmenting their secretion of the known angiogenic factor, sonic hedgehog (Shh).

METHODS AND RESULTS

When injected into the border zone of mice after acute myocardial infarction, Shh-modified CD34+ cells (CD34(Shh)) protected against ventricular dilation and cardiac functional declines associated with acute myocardial infarction. Treatment with CD34(Shh) also reduced infarct size and increased border zone capillary density compared with unmodified CD34 cells or cells transfected with the empty vector. CD34(Shh) primarily store and secrete Shh protein in exosomes and this storage process appears to be cell-type specific. In vitro analysis of exosomes derived from CD34(Shh) revealed that (1) exosomes transfer Shh protein to other cell types, and (2) exosomal transfer of functional Shh elicits induction of the canonical Shh signaling pathway in recipient cells.

CONCLUSIONS

Exosome-mediated delivery of Shh to ischemic myocardium represents a major mechanism explaining the observed preservation of cardiac function in mice treated with CD34(Shh) cells.

Gene therapy in the treatment of peripheral arterial disease

BACKGROUND

Peripheral arterial disease remains a significant global health burden despite revolutionary improvements in endovascular techniques over the past decade. The durability of intervention for critical limb ischaemia is poor, and the condition is associated with high morbidity and mortality rates. To address this deficiency, alternative therapeutic options are being explored. Advances in the fields of gene therapy and therapeutic angiogenesis have led to these being advocated as potential future treatments.

METHODS

Relevant medical literature from PubMed, Embase, the Cochrane Library and Google Scholar from the inception of these databases to June 2011 was reviewed.

RESULTS

Encouraging outcomes in preclinical trials using a variety of proangiogenic growth factors have led to numerous efficacy and safety studies. However, no clinical study has shown significant benefit for gene therapy over placebo.

CONCLUSION

Identifying the optimal site for gene delivery, choice of vector and duration of treatment is needed if gene therapy is to become a credible therapeutic option for peripheral arterial disease.

Current approach to the diagnosis and treatment of femoral-popliteal arterial disease. A systematic review

Peripheral arterial disease (PAD) is a common manifestation of atherosclerosis affecting 5 million adults in the United States, with an age-adjusted prevalence of 4% to 15% and increasing up to 30% with age and the presence of cardiovascular risk factors. In this article we focus on lower extremity PAD and specifically on the superficial femoral and proximal popliteal artery (SFPA), which are the most common anatomic locations of lower extremity atherosclerosis. We summarize current evidence and perform a systematic review on the diagnostic evaluation as well as the medical, endovascular and surgical management of SFPA disease.

Plasmid-mediated gene therapy for cardiovascular disease

Gene transfer within the cardiovascular system was first demonstrated in 1989 yet, despite extensive basic-science and clinical research, unequivocal benefit in the clinical setting remains to be demonstrated. Potential reasons for this include the fact that recombinant viral vectors, used in the majority of clinical studies, have inherent problems with immunogenicity that are difficult to circumvent. Attention has turned therefore to plasmid vectors, which possess many advantages over viruses in terms of safety and ease of use, and many clinical studies have now been performed using non-viral technology. This review will provide an overview of clinical trials for cardiovascular disease using plasmid vectors, recent developments in plasmid delivery and design, and potential directions for this modality of gene therapy.

Perspectives on optimizing trial design and endpoints in peripheral arterial disease: a case for imaging-based surrogates as endpoints of functional efficacy

Surrogate endpoints are important for validation of mechanism, early proof of concept, and the rational design of clinical trials for regulatory approval of drugs. The recent failure of several drugs in peripheral arterial disease (PAD) and in atherosclerosis highlights the importance of understanding drug effect and is a clarion call for better endpoints. This review focuses on aspects relating to the current state of surrogate endpoints in PAD and reviews emerging endpoints using imaging approaches that may have the potential of improving study design in PAD.

Autologous bone-marrow mononuclear cell implantation reduces long-term major amputation risk in patients with critical limb ischemia: a comparison of atherosclerotic peripheral arterial disease and Buerger disease

BACKGROUND

Bone-marrow mononuclear cell (BM-MNC) implantation improves ischemic symptoms in patients with critical limb ischemia (CLI). The purpose of this study was to evaluate long-term clinical outcomes after autologous BM-MNC implantation in patients with CLI.

METHODS AND RESULTS

We assessed long-term clinical outcomes after BM-MNC implantation in 51 patients with CLI, including 25 patients with peripheral arterial disease (PAD) and 26 patients with Buerger disease. Forty-six CLI patients who had no BM-MNC implantation served as control subjects. Median follow-up period was 4.8 years. The 4-year amputation-free rates after BM-MNC implantation were 48% in PAD patients and 95% in Buerger disease, and they were 0% in control PAD patients and 6% in control Buerger disease. The 4-year overall survival rates after BM-MNC implantation were 76% in PAD patients and 100% in Buerger disease, and they were 67% in control PAD patients and 100% in control Buerger disease. Multivariable Cox proportional hazards analysis revealed that BM-MNC implantation correlated with prevention of major amputation and that hemodialysis and diabetes mellitus correlated with major amputation. In Buerger disease, ankle brachial pressure index and transcutaneous oxygen pressure were significantly increased after 1 month and remained high during 3-year follow-up. However, in patients with PAD, ankle brachial pressure index and transcutaneous oxygen pressure significantly increased after 1 month and gradually decreased during 3-year follow-up and returned to baseline levels.

CONCLUSIONS

These findings suggest that BM-MNC implantation is safe and effective in patients with CLI, especially in patients with Buerger disease. Clinical Trial Registration- URL: http://home.hiroshima-u.ac.jp/angio/. Unique identifier: 001769.

High expression level of EDIL3 in HCC predicts poor prognosis of HCC patients

AIM: To determine the role of epidermal growth factor-like repeats and discoidin I-like domains 3 (EDIL3) in pathogenesis of hepatocellular carcinoma (HCC) by investigating the EDIL3 expression in HCC and its prognostic value for HCC.

METHODS: EDIL3 expression was detected in 101 HCC surgical tissue samples with immunohistochemistry method, and its relation with clinicopathologic features and prognosis of HCC patients was analyzed.

RESULTS: EDIL3 was highly expressed in 48.5% of the HCC patients. Although the EDIL3 expression level did not correlate with any clinicopathological parameters, Kaplan-Meier survival analysis showed that high expression level of EDIL3 resulted in a significantly poor prognosis of HCC patients (log-rank test, P = 0.010). Multivariate Cox’s analysis showed that the EDIL3 expression level was a significant and independent prognostic parameter for the overall survival rate of HCC patients (hazard ratio = 1.978, 95% confidence interval = 1.139-3.435, P = 0.015).

CONCLUSION: High expression level of EDIL3 predicts poor prognosis of HCC patients. EDIL3 may be a potential target of antiangiogenic therapy for HCC.

Regenerative medicine in the treatment of peripheral arterial disease

The last decade has witnessed a dramatic increase in the mechanistic understanding of angiogenesis and arteriogenesis, the two processes by which the body responds to obstruction of large conduit arteries. This knowledge has been translated into novel therapeutic approaches to the treatment of peripheral arterial disease, a condition characterized by progressive narrowing of lower extremity arteries and heretofore solely amenable to surgical revascularization. Clinical trials of molecular, genetic, and cell-based treatments for peripheral artery obstruction have generally provided encouraging results.

Endovascular treatment of peripheral vascular disease

Peripheral arterial disease (PAD) affects about 27 million people in North America and Europe, accounting for up to 413,000 hospitalizations per year with 88,000 hospitalizations involving the lower extremities and 28,000 involving embolectomy or thrombectomy of lower limb arteries. Many patients are asymptomatic and, among symptomatic patients, atypical symptoms are more common than classic claudication. Peripheral arterial disease also correlates strongly with risk of major cardiovascular events, and patients with PAD have a high prevalence of coexistent coronary and cerebrovascular disease. Because the prevalence of PAD increases progressively with age, PAD is a growing clinical problem due to the increasingly aged population in the United States and other developed countries. Until recently, vascular surgical procedures were the only alternative to medical therapy in such patients. Today, endovascular practice, percutaneous transluminal angioplasty with or without stenting, is used far more frequently for all types of lower extremity occlusive lesions, reflecting the continuing advances in imaging techniques, angioplasty equipment, and endovascular expertise. The role of endovascular intervention in the treatment of limb-threatening ischemia is also expanding, and its promise of limb salvage and symptom relief with reduced morbidity and mortality makes percutaneous transluminal angioplasty/stenting an attractive alternative to surgery and, as most endovascular interventions are performed on an outpatient basis, hospital costs are cut considerably. In this monograph we discuss current endovascular intervention for treatment of occlusive PAD, aneurysmal arterial disease, and venous occlusive disease.