Arterial gene transfer of naked DNA for therapeutic angiogenesis: early clinical results

Gene Therapy of Thromboangiitis Obliterans with Growth Factor Plasmid (VEGF165) and Autologous Bone Marrow Cells

BACKGROUND

We performed gene therapy for critical limb ischemia in thromboangiitis obliterans (TAO) by the intramuscular administration of plasmids of the vascular endothelial growth factor gene (VEGF 165) with or without bone marrow-derived stem cells.

METHODS

The 21 patients were randomly assigned to three groups: A-with dual therapy, cells and plasmid; B-plasmid only; and C-control group, where patients received intramuscular injections of saline. Serum VEGF levels, the ankle-brachial index (ABI), transcutaneous oxygen pressure (TcPO2), and the rest pain measured by the visual analog scale (VAS) were determined sequentially before treatment, and then 1 and 3 months after treatment.

RESULTS

In the treatment groups, serum VEGF levels increased by 4 weeks and returned to baseline values after 3 months. ABI after 12 weeks increased by an average of 0.18 in group A, and 0.09 in group B and group C. TcPO2 increased by an average of 17.3 mmHg in group A, 14.1 mmHg in group B, and 10.7 mmHg in group C. The largest pain decrease was observed in group A and averaged 5.43 less pain intensity.

CONCLUSIONS

Gene therapy using the VEGF plasmid along with or without bone marrow-derived mononuclear cells administered intramuscularly into an ischemic limb in TAO is a safe and effective therapy.

Peripheral artery disease: the new frontiers of imaging techniques to evaluate the evolution of regenerative medicine

Introduction: Stem cells (ESC, iPSC, MSC) are known to have intrinsic regenerative properties. In the last decades numerous findings have favored the development of innovative therapeutic protocols based on the use of stem cells (Regenerative Medicine/Cell Therapy) for the treatment of numerous diseases including PAD, with promising results in preclinical studies. So far, several clinical studies have shown a general improvement of the patient's clinical outcome, however they possess many critical issues caused by the non-randomized design of the limited number of patients examined, the type cells to be used, their dosage, the short duration of treatment and also their delivery strategy. Areas covered: In this context, the use of the most advanced molecular imaging techniques will allow the visualization of very important physio-pathological processes otherwise invisible with conventional techniques, such as angiogenesis, also providing important structural and functional data. Expert opinion: The new frontier of cell therapy applied to PAD, potentially able to stop or even the process that causes the disease, with particular emphasis on the clinical aspects that different types of cells involve and on the use of more innovative molecular imaging techniques now available.

Treatment of Critical Limb Ischemia by pIRES/VEGF165/HGF Administration

BACKGROUND

Prognosis of peripheral artery disease (PAD), especially critical limb ischemia (CLI), is very poor despite the development of endovascular therapy and bypass surgery. Many patients result in having leg amputation. We decided to investigate the safety and efficacy of plasmid of internal ribosome entry site/vascular endothelial growth factor (VEGF) 165/hepatocyte growth factor (HGF) gene therapy (GT) in patients suffered from CLI.

METHODS

Administration of plasmid of internal ribosome entry site/VEGF165/HGF was performed in 12 limbs of 12 patients with rest pain and ischemic ulcers due to CLI. Plasmid was injected into the muscles of the ischemic limbs. The levels of VEGF in serum and the ankle-brachial index (ABI) were measured before and after treatment.

RESULTS

Mean (±SD) plasma levels of VEGF increased nonsignificantly from 258 ± 81 pg/L to 489 ± 96 pg/L (P > 0.05) 2 weeks after therapy, and the ABI improved significantly from 0.27 ± 0.20 to 0.50 ± 0.22 (P < 0.001) 3 months after therapy. Ischemic ulcers healed in 9 limbs. Amputation was performed in 3 patients because of advanced necrosis and wound infection. However, the level of amputations was lowered below knee in these cases. Complications were limited to transient leg edema in 3 patients and fever in 2 patients.

CONCLUSIONS

Intramuscular administration of plasmid of internal ribosome entry site/VEGF165/HGF is safe, feasible, and effective for patients with critical leg ischemia.

Preclinical evaluation of mesenchymal stem cells overexpressing VEGF to treat critical limb ischemia

Numerous clinical trials are utilizing mesenchymal stem cells (MSC) to treat critical limb ischemia, primarily for their ability to secrete signals that promote revascularization. These cells have demonstrated clinical safety, but their efficacy has been limited, possibly because these paracrine signals are secreted at subtherapeutic levels. In these studies the combination of cell and gene therapy was evaluated by engineering MSC with a lentivirus to overexpress vascular endothelial growth factor (VEGF). To achieve clinical compliance, the number of viral insertions was limited to 1–2 copies/cell and a constitutive promoter with demonstrated clinical safety was used. MSC/VEGF showed statistically significant increases in blood flow restoration as compared with sham controls, and more consistent improvements as compared with nontransduced MSC. Safety of MSC/VEGF was assessed in terms of genomic stability, rule-out tumorigenicity, and absence of edema or hemangiomas in vivo. In terms of retention, injected MSC/VEGF showed a steady decline over time, with a very small fraction of MSC/VEGF remaining for up to 4.5 months. Additional safety studies completed include absence of replication competent lentivirus, sterility tests, and absence of VSV-G viral envelope coding plasmid. These preclinical studies are directed toward a planned phase 1 clinical trial to treat critical limb ischemia.

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.

Combined autologous bone marrow mononuclear cell and gene therapy as the last resort for patients with critical limb ischemia

INTRODUCTION

Our study was designed to investigate the safety and efficacy of combined autologous bone marrow mononuclear cell (MNC) and gene therapy in comparison to conventional drug therapy in patients with critical limb ischemia (CLI).

MATERIAL AND METHODS

Thirty-two patients with CLI persisting for 12-48 months (average time 27.5 months) were randomized into 2 groups, each group consisting of 16 patients. In the first group, administration of autologous bone marrow MNC and vascular endothelial growth factor (VEGF) plasmid was performed. The patients from the second group were treated pharmacologically with pentoxifylline. Ankle-brachial index (ABI) was measured and angiography was performed before and finally 3 months after treatment. The pain was evaluated using the Visual Analog Scale (VAS) before and after 3 months.

RESULTS

Ankle-brachial index improved significantly from 0.29 ±0.21 to 0.52 ±0.23 (p < 0.001) in 12 patients (75.0%) 3 months after the experimental therapy in group 1. In this group angiography showed the development of collateral vessels. Ischemic ulcers healed completely in 11 patients (68.75%). In group 2 the ABI did not improve in any patient; moreover the complete healing of skin ulcers was not found in any of the patients of this group. Amputation was performed in 4 (25.0%) patients in group 1, and in 8 patients (50%) from group 2.

CONCLUSIONS

These data after 3-month follow-up indicate that intramuscular injection of MNC combined with gene therapy in patients with chronic CLI is safe, and a more feasible and effective method of treatment than the conventional therapy. However, both therapies are limited by the degree of microcirculation damage.

Microvascular repair: post-angiogenesis vascular dynamics

Vascular compromise and the accompanying perfusion deficits cause or complicate a large array of disease conditions and treatment failures. This has prompted the exploration of therapeutic strategies to repair or regenerate vasculatures, thereby establishing more competent microcirculatory beds. Growing evidence indicates that an increase in vessel numbers within a tissue does not necessarily promote an increase in tissue perfusion. Effective regeneration of a microcirculation entails the integration of new stable microvessel segments into the network via neovascularization. Beginning with angiogenesis, neovascularization entails an integrated series of vascular activities leading to the formation of a new mature microcirculation, and includes vascular guidance and inosculation, vessel maturation, pruning, AV specification, network patterning, structural adaptation, intussusception, and microvascular stabilization. While the generation of new vessel segments is necessary to expand a network, without the concomitant neovessel remodeling and adaptation processes intrinsic to microvascular network formation, these additional vessel segments give rise to a dysfunctional microcirculation. While many of the mechanisms regulating angiogenesis have been detailed, a thorough understanding of the mechanisms driving post-angiogenesis activities specific to neovascularization has yet to be fully realized, but is necessary to develop effective therapeutic strategies for repairing compromised microcirculations as a means to treat disease.

Critical limb ischemia: cell and molecular therapies for limb salvage

There is a growing interest in developing new limb salvage therapies for patients with severe peripheral artery disease who have no alternative to amputation. Cell and gene therapy studies are showing promise in controlling pain and minor ulceration in patients with significant critical limb ischemia. Among cardiovascular cell and molecular therapy programs, The Methodist Hospital is one of the leading centers in both gene and cell therapy for critical limb ischemia. Randomized controlled trials continue to be performed, and these experimental therapies will move from research to pharmacy within the decade. In conjunction with aggressive medical and surgical management, these emergent therapies may help patients with critical limb ischemia avoid a major amputation and are one of the foundations of any advanced limb salvage program.

Therapeutic angiogenesis for myocardial ischemia revisited: basic biological concepts and focus on latest clinical trials

Therapeutic angiogenesis is based on the premise that the development of new blood vessels can be augmented by exogenous administration of the appropriate growth factors. Over the last years, successful preclinical studies and promising results of early clinical trials have created great excitement about the potential of therapeutic angiogenesis for patients with advanced ischemic heart disease. The authors provide an overview of the biology of angiogenesis, the basic characteristics of angiogenic factors, and the different routes of their delivery. They discuss experimental studies in animal models of myocardial ischemia and outline available clinical studies on therapeutic angiogenesis for myocardial ischemia. Related safety issues are also addressed followed by a critical perspective about the future of proangiogenic therapies for ischemic cardiovascular disorders. Despite the established proof of concept and reasonable safety, however, results of the latest trials on therapeutic angiogenesis for myocardial ischemia have provided inconsistent results and the definite means of inducing clinically useful therapeutic angiogenesis remain elusive. More studies are required to gain further insights into the biology of angiogenesis and address pharmacological limitations of current approaches of angiogenic therapy. The authors hope and envisage that in the not-too-distant future, these investigative efforts will lead to important new strategies for treatment of myocardial ischemic syndromes. Means of non-invasive individualized pharmacological therapeutic neovascularization may be the next major advance in the treatment of ischaemic heart disease.

Prostanoids for critical limb ischaemia

BACKGROUND

Peripheral arterial occlusive disease (PAOD) is a common cause of morbidity and mortality due to cardiovascular diseases in the general population. While numerous treatments have been adopted for different disease stages, there is no option other than amputation for patients presenting with critical limb ischaemia (CLI), unsuitable for rescue or reconstructive intervention.

OBJECTIVES

To determine the effectiveness and safety of prostanoids in patients presenting with CLI.

SEARCH STRATEGY

The Cochrane Peripheral Vascular Diseases Group searched their trials register (last searched October 2009) and the Cochrane Central Register of Controlled Trials (CENTRAL) in The Cochrane Library (last searched 2009, Issue 4) for publications describing randomised controlled trials (RCTs) of prostanoids for CLI. We ran additional searches in MEDLINE, EMBASE, LILACS, and SciSearch, and we also contacted pharmaceutical companies and experts, in order to identify unpublished data and trials still underway.

SELECTION CRITERIA

Randomised controlled trials describing efficacy and safety of prostanoids compared with placebo or other pharmacological control treatments, in patients presenting with CLI, without chance of rescue or reconstructive intervention.

DATA COLLECTION AND ANALYSIS

Two authors independently selected trials, assessed trials for eligibility and methodological quality, and extracted data. Disagreements were resolved by consensus or by the third author.

MAIN RESULTS

We retrieved 532 citations which after the first screening resulted in 111 potential studies. Finally, after exclusion of studies of poor quality and a lack of sufficient information, 20 trials were included in the review.Prostanoids seem to have efficacy regarding rest-pain relief (risk ratio (RR) 1.32, 95% confidence interval (CI) 1.10 to 1.57; P = 0.003), and ulcer healing (RR 1.54, 95% CI 1.22 to 1.96). Iloprost also shows favourable results regarding major amputations (RR 0.69, 95% CI 0.52 to 0.93). The more frequently reported adverse events when using prostanoids were headache, facial flushing, nausea, vomiting and diarrhoea.

AUTHORS' CONCLUSIONS

Despite some positive results regarding rest-pain relief, ulcer healing and amputations, there is no conclusive evidence based on this meta-analysis of the long-term effectiveness and safety of different prostanoids in patients with CLI. Further well-conducted, high quality randomised double-blinded trials should be performed.

Angiogenic effect of saponin extract from Panax notoginseng on HUVECs in vitro and zebrafish in vivo

Angiogenesis plays an important role in a wide range of physiological processes such as wound healing and fetal development. In fact, many diseases are associated with imbalance in the regulation of angiogenesis in which there is either excessive or insufficient blood vessel formation. Panax notoginseng, a blood circulation invigorating herb, is commonly used in traditional Chinese medicine to treat circulation-related diseases. However, the biological effects of saponin extract from Panax notoginseng (PNS) on angiogenesis and the underlying mechanisms are yet to be fully elucidated. This investigation describes the angiogenic effects of PNS on human umbilical vein endothelial cells (HUVECs) in vitro and zebrafish in vivo. The 2,3-bis(2-methoxy-4-nitro-5-sulfophenyl)5[(phenylamino)carbonyl]2H-tetrazolium hydroxide (XTT) assay and microscopic cell counting demonstrated that the extract was able to stimulate the proliferation of HUVECs. Meanwhile, the numbers of invaded cells and tube branches were significantly increased in PNS treatment groups. PNS was also shown to promote changes in the subintestinal vessels, a feature of angiogenesis, in zebrafish. In addition, by using real-time polymerase chain reaction (PCR), PNS was found to enhance vascular endothelial growth factor (VEGF) and kinase-domain region/fetal liver kinase-1 in mice (KDR/Flk-1) mRNA expression, and the PNS-induced HUVECs proliferation could be abolished by a KDR/Flk-1 inhibitor. Furthermore, the proliferation of HUVECs induced by PNS was significantly attenuated by inhibitors of PI3K-Akt-eNOS. All the results suggest that PNS can promote angiogenesis, and that the proangiogenic effects involve the VEGF-KDR/Flk-1 and PI3K-Akt-eNOS signaling pathways.

Vascular growth in ischemic limbs: a review of mechanisms and possible therapeutic stimulation

Stimulation of vascular growth to treat limb ischemia is promising, and early results obtained from uncontrolled clinical trials using angiogenic agents, e.g., vascular endothelial growth factor, led to high expectations. However, negative results from recent placebo-controlled trials warrant further research. Here, current insights into mechanisms of vascular growth in the adult, in particular the role of angiogenic factors, the immune system, and bone marrow, were reviewed, together with modes of its therapeutic stimulation and results from recent clinical trials. Three concepts of vascular growth have been described to date-angiogenesis, vasculogenesis, and arteriogenesis (collateral artery growth)-which represent different aspects of an integrated process. Stimulation of arteriogenesis seems clinically most relevant and has most recently been attempted using autologous bone marrow transplantation with some beneficial results, although the mechanism of action is not completely understood. Better understanding of the highly complex molecular and cellular mechanisms of vascular growth may yet lead to meaningful clinical applications.

Microenvironmental regulation of biomacromolecular therapies

There is currently great interest in molecular therapies to treat various diseases, and this has prompted extensive efforts to achieve target-specific and controlled delivery of bioactive macromolecules (for example, proteins, antibodies, DNA and small interfering RNA) through the design of smart drug carriers. By contrast, the influence of the microenvironment in which the target cell resides and the effect it might have on the success of biomacromolecular therapies has been under-appreciated. The extracellular matrix (ECM) component of the cellular niche may be particularly important, as many diseases and injury disrupt the normal ECM architecture, the cell adhesion to ECM, and the subsequent cellular activities. This Review will discuss the importance of the ECM and the ECM-cell interactions on the cell response to bioactive macromolecules, and suggest how this information could lead to new criteria for the design of novel drug delivery systems.

[Chronic critical ischemia of the lower leg: pretherapeutic imaging and methods for revascularization]

Each year 1-2% of patients with peripheral arterial occlusive disease (pAOD) develop critical limb ischemia (CLI), characterized by rest pain and peripheral ulcer or gangrene. This aggravation of the disease is accompanied by an increase of the 1-year mortality rate up to 25% and a similarly increased frequency of major amputation. We can choose between conservative, endovascular, and surgical procedures for an adequate therapy of the underlying vascular stenoses or occlusions. Yet, clear therapeutic recommendations only exist for suprapopliteal lesions. However, in a number of cases, especially in diabetics, target lesions have an infrapopliteal location. Since endovascular procedures have undergone significant improvement in the last few years, the following review discusses methods for infrapopliteal revascularization taking into consideration the newest publications on this topic.

Therapeutic Angiogenesis Inhibits or Rescues Chemotherapy-induced Peripheral Neuropathy: Taxol- and Thalidomide-induced Injury of Vasa Nervorum is Ameliorated by VEGF

Toxic neuropathy represents an important clinical problem in the use of the chemotherapeutic substances Taxol and thalidomide. Sensory neuropathy has a high incidence, lacks an effective treatment and is the dose-limiting factor for these drugs. The pathogenic basis of these neuropathies is unknown. We investigated the hypothesis that the experimental toxic neuropathies from Taxol and thalidomide results from destruction of vasa nervorum and can be reversed by the administration of an angiogenic cytokine. In animal models of Taxol- and thalidomide-induced neuropathy, nerve blood flow has been attenuated and the number of vasa nervorum has been reduced. Intramuscular gene transfer of naked plasmid DNA encoding VEGF-1 administered in parallel with Taxol injections completely inhibited deterioration of nerve function and diminution of the peripheral nerve vasculature. Gene therapy in animals with established Taxol- or thalidomide-induced neuropathies resulted in recovery of vascularity and improved nerve electrophysiology. These findings implicate microvascular damage as the basis for toxic neuropathy and suggest that angiogenic growth factors may constitute a novel treatment for this disorder.

Gene therapy of the ischemic lower limb--Therapeutic angiogenesis

The limitations of surgical revascularisation and pharmacological treatment in peripheral arterial occlusive disease (PAOD) are well recognized. Therapeutic options for critical leg ischemia are consequently limited to percutaneous transluminal angioplasty (PTA) or surgical revascularisation. Unfortunately, many patients with critical leg ischemia are poor candidates for either procedure. Therapeutic angiogenesis is a novel promising tool to treat these patients. Experimental and clinical and trials of gene transfer for therapeutic angiogenesis have already shown some clinical efficacy. This review is focused on gene transfer techniques in preclinical and clinical therapeutic angiogenesis, angiogenic growth factors, vectors, delivery methods and routes. The results of clinical and experimental studies, safety and side effects of gene therapy, and the perspectives of future research are also discussed.

Electroporation by nucleofector is the best nonviral transfection technique in human endothelial and smooth muscle cells

Background

The aim of this study was to determine the optimal non-viral transfection method for use in human smooth muscle cells (SMC) and endothelial cells (EC).

Methods

Coronary Artery (CoA) and Aortic (Ao) SMC and EC were transfected with a reporter plasmid, encoding chloramphenicol acetyltransferase type 1 (CAT), with seven different transfection reagents, two electroporation methods and a photochemical internalization (PCI) method. CAT determination provided information regarding transfection efficiency and total protein measurement was used to reflect the toxicity of each method.

Results

Electroporation via the nucleofector machine was the most effective method tested. It exhibited a 10 to 20 fold (for SMC and EC, respectively) increase in transfection efficiency in comparison to the lipofection method combined with acceptable toxicity. FuGene 6 and Lipofectamine PLUS were the preferred transfection reagents tested and resulted in 2 to 60 fold higher transfection efficiency in comparison to the PCI which was the least effective method.

Conclusion

This study indicates that electroporation via the nucleofector machine is the preferred non-viral method for in vitro transfection of both human aortic and coronary artery SMC and EC. It may be very useful in gene expression studies in the field of vascular biology. Through improved gene transfer, non-viral transfer techniques may also play an increasingly important role in delivering genes to SMC and EC in relevant disease states.

Management of Peripheral Vascular Disease

The management of patients with peripheral arterial occlusive disease (PAD) has to be planned in the context of natural history, epidemiology, and apparent risk factors that predict deterioration. The ankle-brachial index to date has proved to be the most effective, accurate, and practical method of PAD detection. Given that PAD is a powerful indicator of systemic atherosclerosis and (independent of symptoms) is associated with an increased risk of myocardial infarction and stroke, as well as a six times greater likelihood of death, the prevalence and demographic distribution of measurable PAD becomes particularly relevant. Reliable information on interventions to confer symptom relief is much weaker and reflects discrepancies between published reports from centers of excellence and the experience of patients routinely treated in communities around the world. The impact of newer treatment modalities, such as complex endovascular procedures and therapeutic angiogenesis, has been a subject of recent controversy.

Reciprocal role of vasculogenic factors and progenitor cells in atherogenesis

While neovascularization plays an integral role in atherosclerosis, stimulation of angiogenesis does not appear to promote atherogenesis. This observation is important in view of recent advancements in angiogenic gene and cell therapy aimed at promoting new blood vessel growth in humans with vascular disease. Endothelial progenitor cells (EPCs) may actually prevent rather than provoke intimal thickening and vascular remodeling by promoting re-endothelialization in response to vascular trauma, as occurs with percutaneous transluminal vascular intervention for treating atherosclerotic vessels. Further support for the hypothesis that EPCs continuously repair vascular injury and contribute to the rejuvenation of vessels has been derived from animal studies demonstrating that serial injection of bone marrow-derived EPCs prevent atherogenesis, but that the quantity and quality of these cells deteriorate with aging. This chapter provides a summary of the influence of angiogenesis on atheromatous disease. Furthermore, the increasingly important relationship between atherosclerosis and newly emerging techniques in therapeutic angiogenesis (i.e., gene therapy and cell therapy with EPCs) is discussed.

Non‐Viral Vectors for Gene Therapy: Clinical Trials in Cardiovascular Disease

The population of patients with end-stage symptomatic coronary and peripheral vascular disease is ever-expanding. Many of these patients no longer have options for mechanical revascularization, and despite maximal medical therapy, they remain physically limited due to angina or critical limb ischemia. The fundamental problem in these patients is insufficient blood supply to muscle due to severely diseased conduit vessels to the target tissue. Therefore, it seems logical that increasing the blood supply to ischemic tissue will relieve symptoms. One potential means to achieving this goal is via therapeutic angiogenesis. The molecular mechanisms behind vascular development are being elucidated, and animal models have shown that mediators of vascular development can be harnessed to produce new capillaries in ischemic tissue. These mediators include cytokines such as vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). Angiogenic cytokines can be delivered in several forms including recombinant protein or via gene delivery as a naked plasmid or via viral vector. This chapter will describe the clinical trial experience to date with delivery of non-viral gene therapy for therapeutic angiogenesis in humans with disabling myocardial ischemia and peripheral vascular disease.

Gene therapy for cardiovascular angiogenesis

Atherosclerosis and endothelial dysfunction are responsible for the pathophysiologic basis of the spectrum of cardiovascular disorders including ischaemic heart disease (IHD), the leading cause of morbidity and mortality in the US. There have been major advances, including the use of pharmacotherapy, coronary and peripheral percutaneous transluminal interventions (PTI), coronary and peripheral bypass surgery and primary/secondary prevention measures. There are, however, multiple unmet needs: IHD refractory to medical therapy and unsuitable for revascularisation; critical limb ischaemia unsuitable for PTI or surgery; restenosis; ischaemic/diabetic neuropathy and heart failure. Cardiovascular gene therapy (GT) with vascular endothelial growth factor (VEGF) has yielded improved perfusion and reduced ischaemia in preclinical models of IHD. Several preclinical studies and Phase I and II clinical trials have shown the safety and therapeutic potential of GT in the treatment of IHD, peripheral arterial disease (PAD), restenosis, and ischaemic and diabetic neuropathy, pointing to the need for Phase III clinical trials.

Gene transfer into rabbit keratocytes using AAV and lipid-mediated plasmid DNA vectors with a lamellar flap for stromal access

Development of gene transfer methods that can precisely deliver therapeutic genes to the localized or targeted tissue(s) would be highly beneficial in developing new gene therapy approaches and may also extend animal models for studying in vivo gene function and regulation at molecular levels in the selected tissues. We investigated lipid- and AAV-mediated gene transfer in rabbit cornea using a lamellar flap-technique. The goals of this study were to (1) analyze methods for in situ gene transfer into keratocytes, (2) identify efficient and suitable vectors for gene transfer into keratocytes, and (3) characterize times of first detectable expression, localization and duration of transgene expression in keratocytes with different vectors. A lamellar flap was produced in the rabbit cornea with a microkeratome. Recombinant adeno-associated viral vector (rAAV) expressing either beta-galactosidase (rAAV-beta-gal) or chloramphenicol acetyltransferase (rAAV-CAT) reporter genes, or plasmid-cationic lipid complexes expressing CAT (pMP6-CAT) or beta-galactosidase (pTR-beta-gal) were applied beneath the lamellar flap for two minutes. The flap was repositioned and eyelids sutured overnight. Corneas were removed at 4hr, 12hr, 36hr, 3 days, 7 days, or 10 days after application and either fixed in 2% formaldehyde, cryosectioned and stained for beta-galactosidase activity or homogenized and measured for CAT levels by ELISA. Corneas infected with rAAV-beta-gal vector showed positive beta-gal staining in the center and periphery of the flap interface in whole corneas and corneal beds at 3, 7, and 10 days, but not at earlier time points. Corneas treated with pTR-beta-gal plasmid vector showed positive beta-gal expression at the interface at 4, 12 and 36hr, but not at 3 or 7 days. The posterior surface of the lamellar interface where the vector was applied showed more expression than the overlying anterior surface with both plasmid and viral vectors. The level of gene expression was less with plasmid vector than viral vector monitored using beta-gal staining. CAT-ELISA confirmed expression of the CAT reporter gene with either the plasmid or rAAV vector. These results demonstrate that foreign genes can be introduced into keratocytes with plasmid or viral vectors using a lamellar flap to gain access to the stroma. The expression profile of the reporter genes depended on the vector. Transfection of keratocytes with plasmid vectors produced rapid expression of the reporter genes, but for a short duration. Reporter gene expression following transduction by rAAV vector was delayed several days, but was at higher levels and for a longer duration. This is the first report to demonstrate selective gene transfer into keratocytes and would be highly useful in studying function and regulation of genes in vivo and may eventually furnish a tool for the treatment of corneal dystrophies.

Molecular strategy using cis-element 'decoy' of E2F binding site inhibits neointimal formation in porcine balloon-injured coronary artery model

Transcription factor E2F plays a pivotal role in the transactivation of cell cycle regulatory genes, leading to vascular lesion formation. Double-stranded DNA with high affinity for E2F as 'decoy' cis elements may block the activation of genes mediating the cell cycle, resulting in an effective therapeutic agent for treating intimal hyperplasia. In this study, we tested the feasibility of E2F decoy therapy to treat neointimal formation in a porcine coronary artery balloon injury model. An angioplasty catheter was inserted in the left anterior descending coronary artery of pigs to cause vascular injury. Initially, we tested the feasibility of transfection of FITC-labeled E2F decoy ODN using a hydrogel balloon catheter. Fluorescence due to E2F decoy ODN could be detected throughout the medial layer. Therefore, we transfected E2F decoy ODN into the balloon-injured artery using hydrogel catheter. Of importance, intravascular ultrasound (IVUS) and histological evaluation demonstrated that plaque area in the balloon-injured artery was significantly reduced by E2F decoy ODN compared with mismatched decoy ODN at 1 month after a single transfection (P < 0.01). In contrast, luminal and total vessel areas were significantly increased in vessels treated with E2F decoy ODN as compared with mismatched decoy. Endothelial function after angioplasty was not affected by E2F decoy transfection. Finally, we tested the acute toxicity of E2F decoy ODN in monkeys, and no apparent side-effects were detected. Here, we report the successful in vivo transfer of E2F decoy ODN using a hydrogel catheter to inhibit vascular lesion formation in balloon-injured porcine coronary artery without any apparent side-effects.

Pathologic features of vascular endothelial growth factor-induced retinopathy in the nonhuman primate

PURPOSE

Vascular endothelial growth factor (VEGF) is a potent ischemia-upregulated angiogenic protein that has been implicated in diabetic retinopathy. Intravitreal VEGF injections have not previously been shown to produce preretinal neovascularization. The purpose of this study was to further characterize the angiopathic changes that occur after intravitreal injections in a nonhuman primate and determine if preretinal neovascularization develops.

DESIGN

Experimental animal study.

METHODS

Vascular endothelial growth factor 165 was injected into the eyes of normal cynomolgus monkeys at regular intervals. As a control, normal eyes were injected with phosphate buffered saline. Color photography and fluorescein angiography were performed at regular intervals. The retinas were incubated for adenosine diphosphatase (ADPase) activity to visualize retinal vessels. The retinas were flat-embedded and areas of potential preretinal neovascularization were identified en bloc and serially sectioned.

RESULTS

Areas of capillary nonperfusion and vessel dilation and tortuousity were seen by angiography. In serial sections, the nonperfused areas were found to be associated with endothelial cell hyperplasia in vessel lumens. Preretinal neovascularization originating only from superficial veins and venules was observed throughout peripheral retina, but was not seen in the posterior pole. Lacunae-like veins were subdivided by the process of intussusception and endothelial cell bridging. Arterioles demonstrated endothelial cell hyperplasia and microaneurysms.

CONCLUSION

Intraocular injections of VEGF were sufficient to produce preretinal neovascularization in the nonhuman primate. Most vasculopathic structures were associated with endothelial cell hyperplasia. These results demonstrate that VEGF alone can produce many features of both nonproliferative and proliferative diabetic retinopathy including the previously undescribed development of preretinal neovascularization. This well-characterized VEGF-induced primate model of retinal neovascularization may be useful as a means of testing new treatments for retinal neovascularization.

Nonviral gene transfer strategies for the vasculature

Major attention has been focused on the development of gene therapy approaches for the treatment of vascular diseases. In this review, we focus on an alternative use of gene therapy: the use of genetic means to study vascular cell biology and physiology. Both viral and nonviral gene transfer strategies have limitations, but because of the overwhelming inflammatory responses associated with the use of viral vectors, nonviral gene transfer methods are likely to be used more abundantly for future applications in the vasculature. Researchers have made great strides in the advancement of gene delivery to the vasculature in vivo. However, the efficiency of gene transfer seen with most nonviral approaches has been exceedingly low. We discuss how to circumvent and take advantage of a number of the barriers that limit efficient gene delivery to the vasculature to achieve high-level gene expression in appropriate cell types within the vessel wall. With such levels of expression, gene transfer offers the ability to alter pathways at the molecular level by genetically modulating the activity of a gene product, thus obviating the need to rely on pharmacological agents and their foreseen and unforeseen side effects. This genetic ability to alter distinct gene products within a signaling or biosynthetic pathway or to alter structural interactions within and between cells is extremely useful and technologically possible today. Hopefully, with the availability of these tools, new advances in cardiovascular physiology will emerge.

Assessment of risks associated with cardiovascular gene therapy in human subjects

Clinical trials of cardiovascular gene therapy, whether using viral (53%) or nonviral (47%) vectors, have thus far disclosed no evidence indicative of inflammatory or other complications, including death, directly attributable to the vector used. Indeed, despite the fact that initial trials of cardiovascular gene therapy targeted patients with end-stage vascular disease, including critical limb ischemia and refractory myocardial ischemia, the mortality for patients enrolled in clinical trials of cardiovascular gene therapy reported to date compares favorably with mortality for similar groups of patients in contemporary controlled studies of medical or interventional therapies. The most common morbidity reported after cardiovascular gene transfer is lower extremity edema; in contrast to data involving genetically engineered mice, however, evidence of life- or limb-threatening edema has not been described in any patients, including patients after gene transfer for myocardial ischemia. Concerns regarding the potential for angiogenic cytokines to promote the progression of atherosclerosis are not supported by angiographic follow-up of patients with coronary or peripheral vascular disease. The levels and duration of gene expression investigated for therapeutic angiogenesis transfer have been unassociated with hemangioma formation. Likewise, there is little evidence from either preclinical or clinical studies to support the notion that the administration of angiogenic growth factors, per se, is sufficient to stimulate the growth of neoplasms. Patients enrolled in clinical studies of angiogenic cytokines, including patients with diabetes and a previous history of retinopathy, have disclosed no evidence to suggest that ocular pathology is a risk of angiogenic growth factor gene transfer.

Somatic gene therapy in the cardiovascular system

This review surveys a range of approaches using plasmid DNA encoding the 165-amino-acid isoform of vascular endothelial growth factor (phVEGF165) to therapeutically modulate micro- or macrovascular endothelial cells, focusing on strategies to augment postnatal collateral circulation in arterial insufficiency or to accelerate re-endothelialization after balloon angioplasty to prevent restenosis. We focus on intra-arterial and intramuscular/intramyocardial gene transfer of the VEGF165 gene, the options that have been most thoroughly studied to date in patients. We review developmental and postnatal significance of the endothelial-cell-specific mitogen VEGF that has stimulated these studies and present limitations of current knowledge as well as challenges for the future.

Therapeutic angiogenesis for ischemic cardiovascular disease

In animal models of ischemia, a large body of evidence indicates that administration of angiogenic growth factors, either as recombinant protein or by gene transfer, can augment nutrient perfusion through neovascularization. While many cytokines have angiogenic activity, the best studied both in animal models and clinical trials are vascular endothelial growth factor (VEGF) and fibroblast growth factor (FGF). Clinical trials of therapeutic angiogenesis in patients with end-stage coronary artery disease have shown large increases in exercise time and marked reductions in symptoms of angina, as well as objective evidence of improved perfusion and left ventricular function. Larger scale placebo-controlled trials have been limited to intracoronary and intravenous administration of recombinant protein, and have not yet shown significant improvement in either exercise time or angina when compared to placebo. Larger scale placebo-controlled studies of gene transfer are in progress. Future clinical studies will be required to determine the optimal dose, formulation, route of administration and combinations of growth factors, as well as the requirement for endothelial progenitor cell or stem cell supplementation, to provide effective and safe therapeutic myocardial angiogenesis.

Angiogenesis, protein and gene delivery

Advances in our understanding of angiogenesis and blood vessel growth have given rise to efforts to develop novel therapeutic approaches for patients with ischaemia who are not adequately treated with presently available therapies. Among the growth factors that play a role in blood vessel growth and development, vascular endothelial growth factors and fibroblast growth factors have been the most extensively studied. Various methods of delivery have been utilized to enhance localization and persistence, including methods for delivery of proteins as well as gene transfer techniques. Initial clinical trials have now been undertaken. Preliminary information on efficacy is beginning to become available, raising hopes, as well as questions about the future direction and potential success of therapeutic angiogenesis as a clinical approach to the treatment of ischaemia.

Selective downregulation of VEGF-A(165), VEGF-R(1), and decreased capillary density in patients with dilative but not ischemic cardiomyopathy

Cardiomyopathy (CM) comprises a heterogeneous group of diseases, including ischemic (ICM) and dilative (DCM) forms. The pathogenesis of primary DCM is not clearly understood. Recent studies in mice show that vascular endothelial growth factor (VEGF) is involved in ICM. Whether VEGF plays a role in human CM is unknown. We examined the mRNA and protein expression of VEGF and its receptors in hearts of patients with end-stage DCM and ICM and in healthy individuals using real-time polymerase chain reaction and Western blotting. Number of capillaries, area of myocytes, and collagen were calculated in cardiac biopsies using transmission electron microscopy. In DCM, except for VEGF-C, mRNA transcript levels of VEGF-A(165), VEGF-A(189), and VEGF-B and the protein level of VEGF-A and VEGF-R(1) were downregulated compared with controls (P:<0.05). However, in ICM, mRNA transcript levels of VEGF isoforms and protein levels of VEGF-C were upregulated. The vascular density was decreased in DCM but increased in ICM compared with controls (P:<0. 05). Muscular hypertrophy was not different for ICM and DCM, although DCM had more collagen (P:<0.05). Blunted VEGF-A and VEGF-R(1) protein expression and downregulated mRNA of the predominant isoform of VEGF-A, VEGF-A(165), to our knowledge shown here for the first time, provide evidence that the VEGF-A defect in DCM is located upstream. Whether downregulation of certain VEGF isoforms in DCM is a cause or consequence of this disorder remains unclear, although upregulated VEGF levels in ICM are most likely the result of ischemia.

Lower-extremity edema associated with gene transfer of naked DNA encoding vascular endothelial growth factor

BACKGROUND

Vascular endothelial growth factor (VEGF) promotes angiogenesis and vascular permeability. The extent to which VEGF may cause tissue edema in humans has not been established.

OBJECTIVE

To evaluate patients undergoing VEGF gene transfer for evidence of lower-extremity edema.

DESIGN

Prospective consecutive case series.

SETTING

Hospital outpatient clinic.

PATIENTS

62 patients with critical limb ischemia and 28 patients with claudication.

INTERVENTION

Gene transfer of VEGF DNA.

MEASUREMENTS

Semiquantitative analysis of lower-extremity edema.

RESULTS

Lower-extremity edema was observed in 31 of 90 (34%) patients. Edema was less common in patients with claudication than in those with pain at rest (P = 0.016) or ischemic ulcers (P < 0.001), and it was less common in patients with pain at rest than in those with ischemic ulcers (P= 0.017). Treatment was typically limited to a brief course of oral diuretics.

CONCLUSIONS

Vascular endothelial growth factor may enhance vascular permeability in humans. At the doses of plasmid DNA used in this study, lower-extremity edema responded to oral diuretic therapy and did not seem to be associated with serious sequelae.

Manipulating angiogenesis against vascular disease

Gene therapy to stimulate the growth of new blood vessels is proving to be an effective way of bypassing occluded arteries and reestablishing blood flow to ischemic tissues. It could eventually replace surgical revascularization and angioplasty, which are not only more invasive but also plagued with restenosis, problems limiting long-term management of coronary artery and peripheral vascular disease.