Therapeutic angiogenesis for myocardial ischemia

Therapeutic angiogenesis offers promise as a novel treatment for ischemic heart disease, particularly for patients who are not candidates for current methods of revascularization. The goal of treatment is both relief of symptoms of coronary artery disease and improvement of cardiac function by increasing perfusion to the ischemic region. Protein-based therapy with cytokines including vascular endothelial growth factor and fibroblast growth factor demonstrated functionally significant angiogenesis in several animal models. However, clinical trials have yielded largely disappointing results. The attenuated angiogenic response seen in clinical trials of patients with coronary artery disease may be due to multiple factors including endothelial dysfunction, particularly in the context of advanced atherosclerotic disease and associated comorbid conditions, regimens of single agents, as well as inefficiencies of current delivery methods. Gene therapy has several advantages over protein therapy and recent advances in gene transfer techniques have improved the feasibility of this approach. The safety and tolerability of therapeutic angiogenesis by gene transfer has been demonstrated in phase I clinical trials. The utility of therapeutic angiogenesis by gene transfer as a treatment option for ischemic cardiovascular disease will be determined by adequately powered, randomized, placebo-controlled Phase II and III clinical trials. Cell-based therapies offer yet another approach to therapeutic angiogenesis. Although it is a promising therapeutic strategy, additional preclinical studies are warranted to determine the optimal cell type to be administered, as well as the optimal delivery method. It is likely the optimal treatment will involve multiple agents as angiogenesis is a complex process involving a large cascade of cytokines, as well as cells and extracellular matrix, and administration of a single factor may be insufficient. The promise of therapeutic angiogenesis as a novel treatment for no-option patients should be approached with cautious optimism as the field progresses.     

New options for untreatable coronary artery disease: angiogenesis and laser revascularization

Some patients with severe symptomatic coronary artery disease despite maximal medical therapy are not eligible for bypass surgery or percutaneous coronary intervention, but may be eligible for two newer therapies: therapeutic angiogenesis with growth factors and transmyocardial laser revascularization.     

The future of therapeutic myocardial angiogenesis

Despite improvements in its medical and surgical management, ischemic coronary disease remains responsible for significant morbidity, mortality, and economic burden in developed nations. Therapeutic myocardial angiogenesis is an attractive treatment option for patients with end-stage coronary disease who have failed percutaneous and surgical methods of revascularization. Over the past decade, our understanding of the biology of new blood vessel formation has improved significantly, and consequently, the use of growth factors to induce myocardial angiogenesis has been attempted in preclinical and clinical trials. Although growth factor therapy had demonstrated tremendous success in animal models, clinical trials have shown limited benefit in patients with coronary disease. Vascular endothelial growth factors and fibroblast growth factors are perhaps the most potent inducers of angiogenesis that have been used in animal models, and the only ones that have been used in clinical trials. This review outlines the biology of new vessel formation and the effects of these growth factors in the context of myocardial angiogenesis with an emphasis on the effects on the endothelium. It also provides a brief overview of delivery strategies and summarizes the preclinical and clinical evidence relating to exogenous growth factor delivery for myocardial angiogenesis. Lastly, we discuss the limitations and future challenges of angiogenic therapy.     

Cellular and molecular therapeutic modalities for arterial obstructive syndromes

Arterial obstructive syndromes result in heart disease, stroke and limb loss, disability, and mortality. Currently available therapeutics for patients with these conditions are inadequate or fail in a significant number of patients. The development of novel therapies for severe coronary arterial disease (CAD), peripheral arterial disease (PAD), and cerebral vascular disease (CVD) is a major goal for modern medicine. Molecular and cell-based therapies for arterial obstructive syndromes have the potential to become clinically useful in the near future. Molecular therapy employs angiogenic proteins and genes in order to initiate the development of new blood vessels that by-pass an arterial occlusion. The induction of a collateral artery system is termed therapeutic angiogenesis or neovascularization. Proteins have been delivered either directly into the ischemic area or via a vector encoding an angiogenic gene. Both protein and gene therapies have been associated with promising preclinical and early phase human trial results in patients with PAD as well as CAD. However, to date, efficacy has not been demonstrated in placebo-controlled, large trails. Today's cell-based therapy is focused on stem cells (SCs) for the treatment of patients after acute myocardial infarction (AMI) or for patients with severe left ventricular dysfunction. Stem cells have shown to increase cardiac performance in uncontrolled, early phase human studies. This improvement is believed to have its origin in myogenesis and neovascularization. In the following review, we will cover current state of molecular- and cellular-based treatments for PAD and CAD that have reached the clinical arena.     

Cholesterol in peripheral vascular disease--a suitable case for treatment?

We assessed the prevalence of conventional risk factors for ischaemic heart disease in patients with peripheral vascular disease, and the scope for preventative treatment with lipid-lowering therapy in this group, by retrospectively reviewing 299 patients who had undergone peripheral angiography in 1996. A total of 278 patients had severe peripheral vascular disease; 44% were current smokers at the time of their angiogram, and 36% had a history of coronary artery disease (either myocardial infarction, coronary artery bypass surgery, coronary angioplasty or angina). Cholesterol had been measured in 80 (27%) patients, of whom 26 (9%) were receiving treatment for hypercholesterolaemia. Patients with a history of ischaemic heart disease were more likely to have had their cholesterol measured (50% vs. 15%; p < 0.001). Hypertension (defined as systolic > 160 mmHg or diastolic > 90 mmHg) was present in 44%. There was no difference in the distribution of risk factors between those with and those without known ischaemic heart disease. There is a high prevalence of modifiable risk factors for coronary disease in patients with severe peripheral vascular disease. Effective prevention is available for coronary artery disease, but we found low levels of treatment. There is considerable scope for intervention to reduce the risk of coronary disease in such patients.     

Gene therapy for ischemic heart disease

INTRODUCTION: Coronary artery disease (CAD) is still the leading cause of death in industrialized nations. Even though revascularization strategies such as percutaneous coronary intervention (PCI) and coronary artery bypass graft surgery (CABG) as well as drug therapy have significantly reduced mortality, about 30% of patients will develop chronic heart failure over time. Ischemic heart disease and heart failure are characterized by an adverse remodeling of the heart, featuring cardiomyocyte hypertrophy, increased fibrosis and capillary rarification. AREAS COVERED: Beside an assessment of current vector systems, this review focuses on potential target genes affecting angiogenesis/arteriogenesis and contractility. The potential of micro RNA (miRNA) modulation for the de-repression of survival and pro-angiogenic genes is discussed. Since gene therapy of the target region is preferable to avoid systemic contamination, application routes are discussed. Expert opinion: miRNAs are a promising new development for successful gene therapy, especially for acute myocardial infarction since their miRNA antagonists are easy to apply and appear to be selectively absorbed by the ischemic myocardial tissue. Rapid uptake and prolonged presence of known antimirs and antagomirs support this notion. For ischemic heart disease the most promising gene therapeutic approach seems to be the regional intravenous application of suitable AAV vectors and vascular growth factors, providing the full scope of angiogenesis, vessel maturation and collateral growth optionally combined with genes enhancing contractility.     

Long-term safety of intramuscular gene transfer of non-viral FGF1 for peripheral artery disease

Peripheral artery disease is a progressive disease. Primary ischemic leg symptoms are muscle fatigue, discomfort or pain during ambulation, known as intermittent claudication. The most severe manifestation of peripheral artery disease is critical limb ischemia (CLI). The long-term safety of gene therapy in peripheral artery disease remains unclear. This four center peripheral artery disease registry was designed to evaluate the long-term safety of the intramuscular non-viral fibroblast growth factor-1 (NV1FGF), a plasmid-based angiogenic gene for local expression of fibroblast growth factor-1 versus placebo in patients with peripheral artery disease who had been included in five different phase I and II trials. Here we report a 3-year follow-up in patients suffering from CLI or intermittent claudication. There were 93 evaluable patients, 72 of them in Fontaine stage IV (47 NV1FGF versus 25 placebo) and 21 patients in Fontaine stage IIb peripheral artery disease (15 NV1FGF versus 6 placebo). Safety parameters included rates of non-fatal myocardial infarction (MI), stroke, death, cancer, retinopathy and renal dysfunction. At 3 years, in 93 patients included this registry, there was no increase in retinopathy or renal dysfunction associated with delivery of this angiogenic factor. There was also no difference in the number of strokes, MI or deaths, respectively, for NV1FGF versus placebo. In the CLI group, new cancer occurred in two patients in the NV1FGF group. Conclusions that can be drawn from this relatively small patient group are limited because of the number of patients followed and can only be restricted to safety. Yet, data presented may be valuable concerning rates in cancer, retinopathy, MI or strokes following angiogenesis gene therapy in the absence of any long-term data in angiogenesis gene therapy. It may take several years until data from larger patient populations will become available.     

Extracorporeal cardiac shock wave therapy for angina pectoris

Prognosis of severe ischemic heart disease with no indication of percutaneous coronary intervention or coronary artery bypass grafting remains poor. Extracorporeal shock wave (SW) therapy was introduced for medical therapy more than 20 years ago to break up kidney stones. We have demonstrated that extracorporeal cardiac SW therapy at a low level (about 10% of the energy density that used for urinary lithotripsy), effectively induces coronary angiogenesis and improves myocardial ischemia in a porcine model of chronic myocardial ischemia in vivo. Also, our extracorporeal cardiac SW therapy improved symptoms and myocardial ischemia in patients with severe coronary artery disease. Importantly, no procedural complications or adverse effects were noted. These results indicate that our extracorporeal cardiac SW therapy is an effective and non-invasive treatment for ischemic heart disease.     

Gene therapy for ischemic heart disease

Introduction: Coronary artery disease (CAD) is still the leading cause of death in industrialized nations. Even though revascularization strategies such as percutaneous coronary intervention (PCI) and coronary artery bypass graft surgery (CABG) as well as drug therapy have significantly reduced mortality, about 30% of patients will develop chronic heart failure over time. Ischemic heart disease and heart failure are characterized by an adverse remodeling of the heart, featuring cardiomyocyte hypertrophy, increased fibrosis and capillary rarification.

Areas covered: Beside an assessment of current vector systems, this review focuses on potential target genes affecting angiogenesis/arteriogenesis and contractility. The potential of micro RNA (miRNA) modulation for the de-repression of survival and pro-angiogenic genes is discussed. Since gene therapy of the target region is preferable to avoid systemic contamination, application routes are discussed.

Expert opinion: miRNAs are a promising new development for successful gene therapy, especially for acute myocardial infarction since their miRNA antagonists are easy to apply and appear to be selectively absorbed by the ischemic myocardial tissue. Rapid uptake and prolonged presence of known antimirs and antagomirs support this notion. For ischemic heart disease the most promising gene therapeutic approach seems to be the regional intravenous application of suitable AAV vectors and vascular growth factors, providing the full scope of angiogenesis, vessel maturation and collateral growth optionally combined with genes enhancing contractility.     

Angiogenic and antiangiogenic gene therapy

Gene therapy is thought to be a promising method for the treatment of various diseases. One gene therapy strategy involves the manipulations on a process of formation of new vessels, commonly defined as angiogenesis. Angiogenic and antiangiogenic gene therapy is a new therapeutic approach to the treatment of cardiovascular and cancer patients, respectively. So far, preclinical and clinical studies are successfully focused mainly on the treatment of coronary artery and peripheral artery diseases. Plasmid vectors are often used in preparations in angiogenic gene therapy trials. The naked plasmid DNA effectively transfects the skeletal muscles or heart and successfully expresses angiogenic genes that are the result of new vessel formation and the improvement of the clinical state of patients. The clinical preliminary data, although very encouraging, need to be well discussed and further study surely continued. It is really possible that further development of molecular biology methods and advances in gene delivery systems will cause therapeutic angiogenesis as well as antiangiogenic methods to become a supplemental or alternative option to the conventional methods of treatment of angiogenic diseases.     

Choosing a revascularization strategy for your patient with CAD. Consider both the clinical presentation and the urgency of the situation

For patients with less severe coronary artery disease, particularly one- or two-vessel disease, initial therapy may be with either thrombolytics or angioplasty. In those with more extensive disease (three-vessel or left main artery disease or proximal left anterior descending artery stenosis), bypass grafting can significantly reduce mortality. However, a patient's risk profile markedly influences outcome regardless of the procedure performed. Because angioplasty achieves incomplete revascularization, patients may need repeated angiography or revascularization, or they may have recurrent angina. If bypass graft disease is prevented, surgery may be effective for up to 20 years.     

What is the best test for a patient with classic angina?

Symptoms that suggest myocardial ischemia raise two questions: does the patient have severe, hemodynamically obstructive coronary artery disease, and is he or she at risk for premature death or an early, major nonfatal cardiac event? Noninvasive cardiac testing may help with the first question in patients with an intermediate risk of coronary artery disease, and with the second question in patients with either an intermediate or a high risk of disease. Although the diagnostic value of noninvasive tests may be overestimated owing to referral bias, these tests are powerful when used for prognostic purposes. In patients with a normal resting electrocardiogram and no prior revascularization, a regular exercise stress test without imaging should suffice. However, no randomized trials have been done to determine if this strategy leads to better outcomes than with empiric therapy.     

The latest review of therapeutic angiogenesis using angiogenic growth factors to peripheral arterial diseases

Therapeutic angiogenesis using angiogenic growth factors is expected to be a new treatment of patients with severe ischemic diseases. Indeed, human gene therapy for peripheral arterial disease(PAD) using VEGF gene demonstrated the beneficial effects. In contrast, we have reported the potent angiogenic activity of hepatocyte growth factor (HGF) in animal study and we planned gene therapy for ASO and Buerger disease using HGF gene (TREAT-HGF). In a prospective, open-labeled clinical trial, we investigated the safety and biological efficiency of this gene therapy in patients with peripheral arterial disease(PAD) who had failed conventional therapy.     

Tissue engineering strategies for in vivo neovascularisation

Neovascularisation is a promising alternative therapeutic approach to re-establish blood flow in ischaemic tissues of patients suffering from coronary artery or peripheral artery disease. Often, these patients are not suitable candidates for current revascularisation procedures such as coronary angioplasty or bypass surgery. Several strategies are presently under investigation to induce vascularisation by stimulating the body's natural processes of vasculogenesis, angiogenesis and arteriogenesis. These strategies involve transplantation of various cell types into the ischaemic site and the delivery of recombinant angiogenic agents through direct protein administration or gene transfer. We will examine the basic approaches for these neovacularisation strategies and their therapeutic potential as demonstrated in animal models and human trials to date.     

Tissue engineering strategies for in vivo neovascularisation

Neovascularisation is a promising alternative therapeutic approach to re-establish blood flow in ischaemic tissues of patients suffering from coronary artery or peripheral artery disease. Often, these patients are not suitable candidates for current revascularisation procedures such as coronary angioplasty or bypass surgery. Several strategies are presently under investigation to induce vascularisation by stimulating the body’s natural processes of vasculogenesis, angiogenesis and arteriogenesis. These strategies involve transplantation of various cell types into the ischaemic site and the delivery of recombinant angiogenic agents through direct protein administration or gene transfer. We will examine the basic approaches for these neovacularisation strategies and their therapeutic potential as demonstrated in animal models and human trials to date.     

Gene therapy for peripheral arterial disease

Introduction: Gene therapy has emerged as a novel therapy to promote angiogenesis in patients with critical limb ischemia (CLI) caused by peripheral artery disease. Researchers working in this area have focused on pro-angiogenic factors, such as VEGF, fibroblast growth factor (FGF) and hepatocyte growth factor (HGF). Based on the elaborate studies and favorable results of basic research using naked plasmid DNA (pDNA) encoding these growth factors, some clinical Phase I and Phase II trials have been performed. The results of these studies demonstrate the safety of these approaches and their potential for symptomatic improvement in CLI patients. However, the Phase III clinical trials have so far been limited to HGF gene therapy. Because one pitfall of the Phase III trials has been the limited transgene expression achieved using naked pDNA alone, the development of more efficient gene transfer systems, such as ultrasound microbubbles and the needleless injector, as well as the addition of other genes will make these novel therapies more effective and ease the symptoms of CLI.

Areas covered: This study reviews the previously published basic research and clinical trials that have studied VEGF, FGF and HGF gene therapies for the treatment of CLI. Adjunctive therapies, such as the addition of prostacyclin synthase genes and the development of more efficient gene transfer techniques for pDNA, are also reviewed.

Expert opinion: To date, clinical studies have demonstrated the safety of gene therapy in limb ischemia but the effectiveness of this treatment has not been determined. Larger clinical studies, as well as the development of more effective gene therapy, are needed to achieve and confirm beneficial effects.     

Gene therapy of inherited retinopathies: a long and successful road from viral vectors to patients

Abstract Inherited retinopathies (IRs) are common and untreatable blinding conditions inherited mostly as monogenic due to mutations in genes expressed in retinal photoreceptors (PRs) and in retinal pigment epithelium (RPE). Over the last two decades, the retina has emerged as one of the most favorable target tissues for gene therapy given its small size and its enclosed and immune-privileged environment. Different types of viral vectors have been developed, especially those based on the adeno-associated virus (AAV), which efficiently deliver therapeutic genes to PRs or RPE upon subretinal injections. Dozens of successful proofs of concept of the efficacy of gene therapy for recessive and dominant IRs have been generated in small and large models that have paved the way to the first clinical trials using AAV in patients with Leber congenital amaurosis, a severe form of childhood blindness. The results from these initial trials suggest that retinal gene therapy with AAV is safe in humans, that vision can be improved in patients that have suffered from severe impairment of visual function, in some cases for decades, and that readministration of AAV to the subretinal space is feasible, effective, and safe. However, none of the trials could match the levels of efficacy of gene therapy observed in a dog model of the disease, suggesting that there is room for improvement. In conclusion, these results bode well for further testing of AAV-mediated retinal gene therapy in patients with other monogenic and complex forms of blindness.     

Vascular complications and gene therapy

For gene therapy, the last few years have been an exciting period. Encouraging results from several successful gene therapy trials were reported. Children born with a life-threatening immune system disorder, severe combined immune deficiency (SCID), were cured after receiving gene therapy for replacement of their defective adenosine deaminase (ADA) gene. Gene therapy successes related to vascular complications were also reported. The first human gene therapy trial for a blood-vessel disorder was performed successfully, in which copies of an angiogenic gene, the vascular endothelial growth factor (VEGF) gene, were directly delivered to the area surrounding the diseased artery of the leg of a patient with peripheral artery disease. Within a few days, this stimulated the growth of new blood vessels around the blockage in the ailing blood vessel and helped avoid amputation. In 1998, a patient with genetically small arteries became the first to receive VEGF gene therapy in the heart. Multiple copies of a plasmid with the VEGF gene were delivered into the damaged area of the heart, and a few days later angiogenesis ensued that helped bypass the blocked vessel, with markedly reduced chest pain in the patient. Gene therapy is becoming a reality and, more importantly, it appears to be safe and does not require supplementary immuno-suppressing drugs. Gene therapy seems to have begun delivering on its promises.