Efficient gene transfer into myocardium by direct injection of adenovirus vectors

Safety and biodistribution of XC001 (encoberminogene rezmadenovec) gene therapy in rats: a potential therapy for cardiovascular diseases

Adenovirus-mediated gene therapy holds promise for the treatment of cardiovascular diseases such as refractory angina. However, potential concerns around immunogenicity and vector dissemination from the target injected tissue require evaluation. This study was undertaken to evaluate the safety and biodistribution of XC001, a replication-deficient adenovirus serotype 5 vector expressing multiple isoforms of human vascular endothelial growth factor (VEGF), following direct administration into normal rat myocardium. Animals received the buffer formulation or increasing doses of XC001 (1 × 107, 2.5 × 108 or 2.5 × 109 viral particles). Based on in-life parameters (general health, body weights, clinical pathology, serum cardiac troponin I, plasma VEGF, and gross necropsy), there were no findings of clinical concern. On Day 8, intramyocardial administration of XC001 was associated with dose-related, left ventricular myocardial inflammation at injection sites, resolving by Day 30. XC001 DNA was not detected in blood at any time but was present at Day 8 around the site of injection and to a much lesser extent in the spleen, liver, and lungs, persisting at low levels in the heart and spleen until at least Day 91. These findings demonstrate that intramyocardial injection of XC001 is supported for use in human studies.

NDP52 Protects Against Myocardial Infarction-Provoked Cardiac Anomalies Through Promoting Autophagosome-Lysosome Fusion via Recruiting TBK1 and RAB7

Aims: Acute myocardial infarction (MI), caused by acute coronary artery obstruction, is a common cardiovascular event leading to mortality. Nuclear dot protein 52 (NDP52) is an essential selective autophagy adaptor, although its function in MI is still obscure. This study was designed to examine the function of NDP52 in MI and the associated mechanisms. Results: Our results revealed that MI challenge overtly impaired myocardial geometry and systolic function, along with cardiomyocyte apoptosis, myocardial interstitial fibrosis, and mitochondrial damage, and NDP52 nullified such devastating responses. Further studies showed that the blockade of mitochondrial clearance is related to MI-induced buildup of damaged mitochondria. Mechanistic approaches depicted that 7-day MI induced abnormal mitophagy flux, resulting in poor lysosomal clearance of injured mitochondria. NDP52 promoted mitophagy flux through the recruitment of Ras-associated protein RAB7 (RAB7) and TANK-binding kinase 1 (TBK1). On protein co-localization, TBK1 phosphorylated RAB7, in line with the finding that chloroquine or a TBK1 inhibitor reversed NDP52-dependent beneficial responses. Innovation: This study denoted a novel mechanism that NDP52 promotes cardioprotection against ischemic heart diseases through interaction with TBK1 and RAB7, leading to RAB7 phosphorylation, induction of mitophagy to clear ischemia-induced impaired mitochondria, thus preventing cardiomyocyte apoptosis in MI. Conclusion: Our results indicate that NDP52 promotes autophagic flux and clears damaged mitochondria to diminish reactive oxygen species and cell death in a TBK1/RAB7-dependent manner and thus limits MI-induced injury. Antioxid. Redox Signal. 36, 1119-1135.

Surgical Methods for Cardiac Gene Delivery in Large Animals

This chapter describes main strategies of surgical gene delivery in large animals. Existing methods of cardiac gene transfer can be classified by the site of injection, interventional approach, and type of cardiac circulation at the time of transfer. Randomized clinical trials have suggested that the therapeutic benefits of gene therapy are not as substantial as expected from animal studies. This discordance in results is largely due to gene delivery methods that may be effective in small animals but are not scalable to larger species and, therefore, cannot transduce a sufficient fraction of myocytes to establish long-term clinical efficacy. Ideally, an optimized gene transfer should incorporate the following: a closed-loop recirculation for extended transgene residence time; vector washout form the vascular system after transfer to prevent collateral expression; use of methods to increase myocardial transcapillary gradient for viral particles for a better transduction, probably retrograde route of gene delivery through the coronary venous system; and myocardial ischemic preconditioning.

FOXC1 up-regulates the expression of toll-like receptors in myocardial ischaemia

Myocardial ischaemia (MI) remains a major cause of death and disability worldwide. Accumulating evidence suggests a significant role for innate immunity, in which the family of toll‐like receptors (TLRs) acts as an essential player. We previously reported and reviewed the changes of Tlr expression in models of MI. However, the underlying mechanisms regulating Tlr expression in MI remain unclear. The present study first screened transcription factors (TFs) that potentially regulate Tlr gene transcription based on in silico analyses followed by experimental verification, using both in vivo and in vitro models. Forkhead box C1 (FOXC1) was identified as a putative TF, which was highly responsive to MI. Next, by focusing on two representative TLR subtypes, an intracellular subtype TLR3 and a cell‐surface subtype TLR4, the regulation of FOXC1 on Tlr expression was investigated. The overexpression or knockdown of FoxC1 was observed to up‐ or down‐regulate Tlr3/4 mRNA and protein levels, respectively. A dual‐luciferase assay showed that FOXC1 trans‐activated Tlr3/4 promoter, and a ChIP assay showed direct binding of FOXC1 to Tlr3/4 promoter. Last, a functional study of FOXC1 was performed, which revealed the pro‐inflammatory effects of FOXC1 and its destructive effects on infarct size and heart function in a mouse model of MI. The present study for the first time identified FOXC1 as a novel regulator of Tlr expression and described its function in MI.

Sirtuin 3 Therapy Attenuates Aging Expression, Oxidative Stress Parameters, and Neointimal Hyperplasia Formation in Vein Grafts

BACKGROUND

Vein graft (VG) failure due to neointimal hyperplasia remains an important and unresolved problem in cardiovascular surgery. Sirtuin3 (SIRT3) is associated with oxidative stress and lifespan. We aimed to measure SIRT3 expression in the veins of humans and rats during aging, explore the inhibitory effects of SIRT3 on vascular smooth muscle cell (VSMC) proliferation and neointimal hyperplasia in VGs, and investigate the underlying mechanisms.

METHODS

SIRT3 mRNA and protein levels in saphenous veins of young and older humans and in veins of young and old rats were measured by quantitative real-time polymerized chain reaction (PCR) and Western blot analysis. Young and old male rats were randomized to the control (control), graft (graft), adenovirus-encoding green fluorescent protein (Ad-GFP), and adenovirus encoding SIRT3 (Ad-SIRT3) groups. At 7 days after operation, the mRNA and protein levels of SIRT3 and endothelial nitric oxide synthase (eNOS) were measured by quantitative real-time PCR and Western blot analysis. The mRNA levels and enzyme activity of manganese superoxide dismutase (MnSOD) and catalase (CAT) were measured by quantitative real-time PCR and enzymatic activity assay kits, and total nitric oxide (NO) levels were measured by biochemical assay kits. Histomorphometric analysis of VGs and immunohistochemical staining for proliferative activity were performed at 4 weeks after operation. The hemodynamic parameters of the VGs were also measured by ultrasonic examination.

RESULTS

SIRT3 mRNA and protein levels were lower in older human and rat veins than in younger human and rat veins. Ad-SIRT3 treatment significantly increased the expression and concentration of SIRT3, MnSOD, CAT, eNOS, and NO in VGs at 7 days after operation. Ad-SIRT3 gene transfer reduced the neointimal thickness and neointimal area/media area ratio in the VGs of the Ad-SIRT3 groups compared with the graft and Ad-GFP groups, especially in old rats. Proliferative activity was lower in the Ad-SIRT3 groups than in the other groups. The hemodynamic parameters of VGs were obviously improved in the Ad-SIRT3 groups.

CONCLUSIONS

SIRT3 expression decreases in the veins of humans and rats during aging. Furthermore, SIRT3 overexpression can significantly reduce VSMC proliferation and neointimal hyperplasia in VGs. Local intravenous delivery of adenovirus encoding SIRT3 may be a promising gene therapy for preventing VG failure.

Metallothionein Preserves Akt2 Activity and Cardiac Function via Inhibiting TRB3 in Diabetic Hearts

Cardiac insulin resistance is a key pathogenic factor for diabetic cardiomyopathy (DCM), but the mechanism remains largely unclear. We found that diabetic hearts exhibited decreased phosphorylation of total Akt and isoform Akt2 but not Akt1 in wild-type (WT) male FVB mice, which was accompanied by attenuation of Akt downstream glucose metabolic signal. All of these signal changes were not observed in metallothionein cardiac-specific transgenic (MT-TG) hearts. Furthermore, insulin-induced glucose metabolic signals were attenuated only in WT diabetic hearts. In addition, diabetic hearts exhibited increased Akt-negative regulator tribbles pseudokinase 3 (TRB3) expression only in WT mice, suggesting that MT may preserve Akt2 function via inhibiting TRB3. Moreover, MT prevented tert-butyl hydroperoxide (tBHP)-reduced insulin-stimulated Akt2 phosphorylation in MT-TG cardiomyocytes, which was abolished by specific silencing of Akt2. Specific silencing of TRB3 blocked tBHP inhibition of insulin-stimulated Akt2 phosphorylation in WT cardiomyocytes, whereas overexpression of TRB3 in MT-TG cardiomyocytes and hearts abolished MT preservation of insulin-stimulated Akt2 signals and MT prevention of DCM. Most importantly, supplementation of Zn to induce MT preserved cardiac Akt2 signals and prevented DCM. These results suggest that diabetes-inhibited cardiac Akt2 function via TRB3 upregulation leads to aberrant cardiac glucose metabolism. MT preservation of cardiac Akt2 function by inhibition of TRB3 prevents DCM.

Percutaneous Contrast Echocardiography-guided Intramyocardial Injection and Cell Delivery in a Large Preclinical Model

Cell and gene therapy are exciting and promising strategies for the purpose of cardiac regeneration in the setting of heart failure with reduced ejection fraction (HFrEF). Before they can be considered for use, and implemented in humans, extensive preclinical studies are required in large animal models to evaluate the safety, efficacy, and fate of the injectate (e.g., stem cells) once delivered into the myocardium. Small rodent models offer advantages (e.g., cost effectiveness, amenability for genetic manipulation); however, given inherent limitations of these models, the findings in these rarely translate into the clinic. Conversely, large animal models such as rabbits, have advantages (e.g., similar cardiac electrophysiology compared to humans and other large animals), whilst retaining a good cost-effective balance. Here, we demonstrate how to perform a percutaneous contrast echocardiography-guided intramyocardial injection (IMI) technique, which is minimally invasive, safe, well tolerated, and very effective in the targeted delivery of injectates, including cells, into several locations within the myocardium of a rabbit model. For the implementation of this technique, we also have taken advantage of a widely available clinical echocardiography system. After putting in practice the protocol described here, a researcher with basic ultrasound knowledge will become competent in the performance of this versatile and minimally invasive technique for routine use in experiments, aimed at hypothesis testing of the capabilities of cardiac regenerative therapeutics in the rabbit model. Once competency is achieved, the whole procedure can be performed within 25 min after anaesthetizing the rabbit.

Sustained viral gene delivery from a micro-fibrous, elastomeric cardiac patch to the ischemic rat heart

Biodegradable and elastomeric patches have been applied to the surface of infarcted hearts as temporary mechanical supports to effectively alter adverse left ventricular remodeling processes. In this report, recombinant adeno-associated virus (AAV), known for its persistent transgene expression and low pathogenicity, was incorporated into elastomeric polyester urethane urea (PEUU) and polyester ether urethane urea (PEEUU) and processed by electrospinning into two formats (solid fibers and core-sheath fibers) designed to influence the controlled release behavior. The extended release of AAV encoding green fluorescent protein (GFP) was assessed in vitro. Sustained and localized viral particle delivery was achieved over 2 months in vitro. The biodegradable cardiac patches with or without AAV-GFP were implanted over rat left ventricular lesions three days following myocardial infarction to evaluate the transduction effect of released viral vectors. AAV particles were directly injected into the infarcted hearts as a control. Cardiac function and remodeling were significantly improved for 12 weeks after patch implantation compared to AAV injection. More GFP genes was expressed in the AAV patch group than AAV injection group, with both α-SMA positive cells and cardiac troponin T positive cells transduced in the patch group. Overall, the extended release behavior, prolonged transgene expression, and elastomeric mechanical properties make the AAV-loaded scaffold an attractive option for cardiac tissue engineering where both gene delivery and appropriate mechanical support are desired.

Receptor-interacting protein 140 overexpression impairs cardiac mitochondrial function and accelerates the transition to heart failure in chronically infarcted rats

Heart failure (HF) is associated with myocardial energy metabolic abnormality. Receptor-interacting protein 140 (RIP140) is an important transcriptional cofactor for maintaining energy balance in high-oxygen consumption tissues. However, the role of RIP140 in the pathologic processes of HF remains to be elucidated. In this study, we investigated the role of RIP140 in mitochondrial and cardiac functions in rodent hearts under myocardial infarction (MI) stress. MI was created by a permanent ligation of left anterior descending coronary artery and exogenous expression of RIP140 by adenovirus (Ad) vector delivery. Four weeks after MI or Ad-RIP140 treatment, cardiac function was assessed by echocardiographic and hemodynamics analyses, and the mitochondrial function was determined by mitochondrial genes expression, biogenesis, and respiration rates. In Ad-RIP140 or MI group, a subset of metabolic genes changed, accompanied with slight reductions in mitochondrial biogenesis and respiration rates but no change in adenosine triphosphate (ATP) content. Cardiac malfunction was compensated. However, under MI stress, rats overexpressing RIP140 exhibited greater repressions in mitochondrial genes, state 3 respiration rates, respiration control ratio, and ATP content and had further deteriorated cardiac malfunction. In conclusion, RIP140 overexpression leads to comparable cardiac function as resulted from MI, but RIP140 aggravates metabolic repression, mitochondrial malfunction, and further accelerates the transition to HF in response to MI stress.

Biological Therapies for Atrial Fibrillation: Ready for Prime Time?

Atrial fibrillation is a prominent cause of morbidity and mortality in developed countries. Treatment strategies center on controlling atrial rhythm or ventricular rate. The need for anticoagulation is an independent decision from the rate versus rhythm control debate. This review discusses novel biological strategies that have potential utility in the management of atrial fibrillation. Rate controlling strategies predominately rely on G-protein gene transfer to enhance cholinergic or suppress adrenergic signaling pathways in the atrioventricular node. Calcium channel blocking gene therapy and fibrosis enhancing cell therapy have also been reported. Rhythm controlling strategies focus on disrupting reentry by enhancing conduction or suppressing repolarization. Efforts to suppress inflammation and apoptosis are also under study. Resistance to blood clot formation has been shown with thrombomodulin. These strategies are in various stages of preclinical development.

Gene Therapy in Heart Failure

Heart failure is a significant burden to the global healthcare system and represents an underserved market for new pharmacologic strategies, especially therapies which can address root cause myocyte dysfunction. Modern drugs, surgeries, and state-of-the-art interventions are costly and do not improve survival outcome measures. Gene therapy is an attractive strategy, whereby selected gene targets and their associated regulatory mechanisms can be permanently managed therapeutically in a single treatment. This in theory could be sustainable for the patient's life. Despite the promise, however, gene therapy has numerous challenges that must be addressed together as a treatment plan comprising these key elements: myocyte physiologic target validation, gene target manipulation strategy, vector selection for the correct level of manipulation, and carefully utilizing an efficient delivery route that can be implemented in the clinic to efficiently transfer the therapy within safety limits. This chapter summarizes the key developments in cardiac gene therapy from the perspective of understanding each of these components of the treatment plan. The latest pharmacologic gene targets, gene therapy vectors, delivery routes, and strategies are reviewed.

The Use of Gene Therapy for Ablation of Atrial Fibrillation

Atrial fibrillation is the most common clinically significant cardiac arrhythmia, increasing the risk of stroke, heart failure and morbidity and mortality. Current therapies, including rate control and rhythm control by antiarrhythmic drugs or ablation therapy, are moderately effective but far from optimal. Gene therapy has the potential to become an attractive alternative to currently available therapies for atrial fibrillation. Various gene transfer vectors have been developed for cardiovascular disease with viral vectors being most widely used due to their high efficiency. Several gene delivery methods have been employed on different therapeutic targets. With increasing understanding of arrhythmia mechanisms, novel therapeutic targets have been discovered. This review will evaluate state-of-art gene therapy strategies and approaches including sinus rhythm restoration and ventricular rate control that could eventually prevent or eliminate atrial fibrillation in patients.

A needleless liquid jet injection delivery method for cardiac gene therapy: a comparative evaluation versus standard routes of delivery reveals enhanced therapeutic retention and cardiac specific gene expression

This study evaluates needleless liquid jet method and compares it with three common experimental methods: (1) intramuscular injection (IM), (2) left ventricular intracavitary infusion (LVIC), and (3) LV intracavitary infusion with aortic and pulmonary occlusion (LVIC-OCCL). Two protocols were executed. First (n = 24 rats), retention of dye was evaluated 10 min after delivery in an acute model. The acute study revealed the following: significantly higher dye retention (expressed as % myocardial cross-section area) in the left ventricle in both the liquid jet [52 ± 4] % and LVIC-OCCL [58 ± 3] % groups p < 0.05 compared with IM [31 ± 8] % and LVIC [35 ± 4] %. In the second (n = 16 rats), each animal received adeno-associated virus encoding green fluorescent protein (AAV.EGFP) at a single dose with terminal 6-week endpoint. In the second phase with AAV.EGFP at 6 weeks post-delivery, a similar trend was found with liquid jet [54 ± 5] % and LVIC-OCCL [60 ± 8] % featuring more LV expression as compared with IM [30 ± 9] % and LVIC [23 ± 9] %. The IM and LVIC-OCCL cross sections revealed myocardial fibrosis. With more detailed development in future model studies, needleless liquid jet delivery offers a promising strategy to improve direct myocardial delivery.

Gene therapy to stimulate angiogenesis to treat diffuse coronary artery disease

Cardiac gene therapy offers a strategy to treat diffuse coronary artery disease (CAD), a disorder with no therapeutic options. The use of genes to revascularize the ischemic myocardium has been the focus of two decades of preclinical research with a variety of angiogenic mediators, including vascular endothelial growth factor, fibroblast growth factor, hepatocyte growth factor, and others encoded by DNA plasmids or adenovirus vectors. The multifaceted challenge for developing efficient induction of collateral vessels in the ischemic heart requires a choice for route of delivery, dosing level, a relevant animal model, duration of treatment, and assessment of phenotype for efficacy. Overall, studies of gene therapy for ischemia in experimental models are very encouraging, with clear evidence of safety and efficacy, strongly supporting the concept that gene therapy to induce angiogenesis is a viable therapeutic approach for CAD. Clinical studies of cardiac gene therapy with angiogenic factors have added substantially to the evidence for efficacy, but definitive studies have not yet led to commercial approval. This review provides the general concepts for angiogenesis-based therapeutic approaches for diffuse CAD and summarizes the results from key studies in the field with recommendations for refinement to a successful product design and evaluation.

Gene therapy delivery systems for enhancing viral and nonviral vectors for cardiac diseases: current concepts and future applications

Gene therapy is one of the most promising fields for developing new treatments for the advanced stages of ischemic and monogenetic, particularly autosomal or X-linked recessive, cardiomyopathies. The remarkable ongoing efforts in advancing various targets have largely been inspired by the results that have been achieved in several notable gene therapy trials, such as the hemophilia B and Leber's congenital amaurosis. Rate-limiting problems preventing successful clinical application in the cardiac disease area, however, are primarily attributable to inefficient gene transfer, host responses, and the lack of sustainable therapeutic transgene expression. It is arguable that these problems are directly correlated with the choice of vector, dose level, and associated cardiac delivery approach as a whole treatment system. Essentially, a delicate balance exists in maximizing gene transfer required for efficacy while remaining within safety limits. Therefore, the development of safe, effective, and clinically applicable gene delivery techniques for selected nonviral and viral vectors will certainly be invaluable in obtaining future regulatory approvals. The choice of gene transfer vector, dose level, and the delivery system are likely to be critical determinants of therapeutic efficacy. It is here that the interactions between vector uptake and trafficking, delivery route means, and the host's physical limits must be considered synergistically for a successful treatment course.

The road ahead: working towards effective clinical translation of myocardial gene therapies

During the last two decades the fields of molecular and cellular cardiology, and more recently molecular cardiac surgery, have developed rapidly. The concept of delivering cDNA encoding a therapeutic gene to cardiomyocytes using a vector system with substantial cardiac tropism, allowing for long-term expression of a therapeutic protein, has moved from hypothesis to bench to clinical application. However, the clinical results to date are still disappointing. The ideal gene transfer method should be explored in clinically relevant animal models of heart disease to evaluate the relative roles of specific molecular pathways in disease pathogenesis, helping to validate the potential targets for therapeutic intervention. Successful clinical cardiovascular gene therapy also requires the use of nonimmunogenic cardiotropic vectors capable of expressing the requisite amount of therapeutic protein in vivo and in situ. Depending on the desired application either regional or global myocardial gene delivery is required. Cardiac-specific delivery techniques incorporating mapping technologies for regional delivery and highly efficient methodologies for global delivery should improve the precision and specificity of gene transfer to the areas of interest and minimize collateral organ gene expression.

In vivo and ex vivo analysis of tubule function

Analysis of tubule function with in vivo and ex vivo approaches has been instrumental in revealing renal physiology. This work allows assignment of functional significance to known gene products expressed along the nephron, primary of which are proteins involved in electrolyte transport and regulation of these transporters. Not only we have learned much about the key roles played by these transport proteins and their proper regulation in normal physiology but also the combination of contemporary molecular biology and molecular genetics with in vivo and ex vivo analysis opened a new era of discovery informative about the root causes of many renal diseases. The power of in vivo and ex vivo analysis of tubule function is that it preserves the native setting and control of the tubule and proteins within tubule cells enabling them to be investigated in a "real-life" environment with a high degree of precision. In vivo and ex vivo analysis of tubule function continues to provide a powerful experimental outlet for testing, evaluating, and understanding physiology in the context of the novel information provided by sequencing of the human genome and contemporary genetic screening. These tools will continue to be a mainstay in renal laboratories as this discovery process continues and as we continue to identify new gene products functionally compromised in renal disease.

Therapeutic potential of genes in cardiac repair

Cardiovascular diseases remain the primary reason of premature death and contribute to a major percentage of global patient morbidity. Recent knowledge in the molecular mechanisms of myocardial complications have identified novel therapeutic targets along with the availability of vectors that offer the chance for designing gene therapy technique for protection and revival of the diseased heart functions. Gene transfer procedure into the myocardium is demonstrated through direct injection of plasmid DNA or through the coronary vasculature using the direct or indirect delivery of viral vectors. Direct DNA injection to the myocardium is reported to be of immense value in research studies that aims at understanding the activities of various elements in myocardium. It is also deemed vital for investigating the effect of the myocardial pathophysiology on expression of the foreign genes that are transferred. Gene therapies have been reported to heal cardiac pathologies such as myocardial ischemia, heart failure and inherited myopathies in several animal models. The results obtained from these animal studies have also encouraged a flurry of early clinical trials. This translational research has been triggered by an enhanced understanding of the biological mechanisms involved in tissue repair after ischemic injury. While safety concerns take utmost priority in these trials, several combinational therapies, various routes and dose of delivery are being tested before concrete optimization and complete potential of gene therapy is convincingly understood.

High-dose plasmid-mediated VEGF gene transfer is safe in patients with severe ischemic heart disease (Genesis-I). A phase I, open-label, two-year follow-up trial

OBJECTIVES

We aimed to assess safety and, secondarily, the efficacy of intramyocardial high-dose plasmid-vascular endothelial growth factor (VEGF) 165 (pVEGF165) gene transfer in no-option patients with coronary artery disease (CAD).

BACKGROUND

Controlled trials of pVEGF165 in CAD have shown little benefit. One possible reason is shortness of dosage. We have shown in large mammalian models of chronic myocardial ischemia and acute myocardial infarction that intramyocardial pVEGF165 at doses significantly higher than those used in recent phase II trials is safe and efficacious on myocardial perfusion, left ventricular function, and infarct size limitation.

METHODS

Using an injection catheter, 10 patients with severe CAD not amenable for revascularization received 10 intramyocardial injections of 0.38 mg (total dose, 3.8 mg) pVEGF165 in zones exhibiting myocardial ischemia, as assessed by combined stress 99mTc-sestamibi single-photon emission computed tomography and stress echocardiography.

RESULTS

No serious adverse events related to either VEGF or the injection procedure occurred over the 2-year follow-up. One patient suffered femoral artery thrombosis after a follow-up coronary angiography, successfully resolved with medical treatment. Six patients suffered uncomplicated coronary ischemic events during the second year follow-up. Angina functional class decreased from 2.6 ± 0.2 to 1.2 ± 0.3 (mean ± SEM, P < 0.05), quality of life increased from 56.9 ± 3.2 to 82.6 ± 2.4 (P < 0.05), the summed difference score of myocardial perfusion decreased from 13.4 ± 2 to 7.7 ± 1.8 (P < 0.04), and stress ejection fraction did not change (44.2 ± 3.6% to 47.8 ± 3.1%, P = NS).

CONCLUSIONS

High-dose intramyocardial pVEGF165 is safe at 2 years follow-up in patients with severe CAD. The efficacy results observed must be taken cautiously given the uncontrolled, open-label study design.

Gene therapy for the prevention of vein graft disease

Ischemic cardiovascular disease remains the leading cause of death worldwide. Despite advances in the medical management of atherosclerosis over the past several decades, many patients require arterial revascularization to reduce mortality and alleviate ischemic symptoms. Technological advancements have led to dramatic increases in the use of percutaneous and endovascular approaches, yet surgical revascularization (bypass surgery) with autologous vein grafts remains a mainstay of therapy for both coronary and peripheral artery disease. Although bypass surgery is highly efficacious in the short term, long-term outcomes are limited by relatively high failure rates as a result of intimal hyperplasia, which is a common feature of vein graft disease. The supply of native veins is limited, and many individuals require multiple grafts and repeat procedures. The need to prevent vein graft failure has led to great interest in gene therapy approaches to this problem. Bypass grafting presents an ideal opportunity for gene therapy, as surgically harvested vein grafts can be treated with gene delivery vectors ex vivo, thereby maximizing gene delivery while minimizing the potential for systemic toxicity and targeting the pathogenesis of vein graft disease at its onset. Here we will review the pathogenesis of vein graft disease and discuss vector delivery strategies and potential molecular targets for its prevention. We will summarize the preclinical and clinical literature on gene therapy in vein grafting and discuss additional considerations for future therapies to prevent vein graft disease.

Efficient transduction of vascular smooth muscle cells with a translational AAV2.5 vector: a new perspective for in-stent restenosis gene therapy

Coronary artery disease represents the leading cause of mortality in the developed world. Percutaneous coronary intervention (PCI) involving stent placement remains disadvantaged by restenosis or thrombosis. Vascular gene-therapy-based methods may be approached, but lack a vascular gene delivery vector.

We report a safe and efficient long-term transduction of rat carotid vessels after balloon-injury intervention with a translational optimized AAV2.5 vector. Compared to other known AAV serotypes, AAV2.5 demonstrated the highest transduction efficiency of human coronary artery vascular smooth muscle cells (VSMC) in vitro. Local delivery of AAV2.5-driven transgenes in injured carotid arteries resulted in transduction as soon as day 2 after surgery and persisted for at least 30 days. In contrast to adenovirus 5 vector, inflammation was not detected in AAV2.5-transduced vessels. The functional effects of AAV2.5-mediated gene transfer on neointimal thickening were assessed using the sarco/endoplasmic reticulum Ca²⁺ ATPase (SERCA2a) human gene, known to inhibit VSMC proliferation. At 30 days, human SERCA2a mRNA was detected in transduced arteries. Morphometric analysis revealed a significant decrease of neointimal hyperplasia in AAV2.5-SERCA2a transduced arteries: 28.36±11.30 (n=8) vs 77.96±24.60 (n=10) μm², in AAV2.5-GFP-infected, p<0.05.

In conclusion, AAV2.5 vector can be considered as a promising safe and effective vector for vascular gene therapy.

Minimally invasive closed-chest ultrasound-guided substance delivery into the pericardial space in mice

Organ-directed gene transfer remains an attractive method for both gaining a better understanding of heart disease and for cardiac therapy. However, virally mediated transfer of gene products into cardiac cells requires prolonged exposure of the myocardium to the viral substrate. Pericardial injection of viral vectors has been proposed and used with some success to achieve myocardial transfection and may be a suitable approach for transfection of atrial myocardium. Indeed, such an organ-specific method would be particularly useful to reverse phenotypes in young and adult genetically altered murine models of cardiac disease. We therefore sought to develop a minimally invasive technique for pericardial injection of substances in mice. Pericardial access in anaesthetised, spontaneously breathing mice was achieved using continuous high-resolution ultrasound guidance. We could demonstrate adequate delivery of injected substances into the murine pericardium. Atrial epicardial and myocardial cells were transfected in approximately one third of mice injected with enhanced green fluorescent protein-expressing adenovirus. Cellular expression rates within individual murine atria were limited to a maximum of 20 %; therefore, expression efficiency needs to be further improved. Minimally invasive, ultrasound-guided injection of viral material appears a technically challenging yet feasible method for selective transfection of atrial epi- and myocardium. This pericardial injection method may be useful in the evaluation of potential genetic interventions aimed at rescuing atrial phenotypes in transgenic mouse models.

In vitro cellular models for cardiac development and pharmacotoxicology

Permanent cultures of cardiac cells described so far have limited value for studying cell biology and pharmacology of the developing heart because of the loss of proliferative capacity and cardiac-specific properties of cardiomyocytes during long-term cultivation. Pluripotent embryonic carcinoma (EC) and embryonic stem (ES) cells cultivated as permanent lines offer a new approach for studying cardiogenic differentiation in vitro. We describe cardiogenesis in vitro by differentiating EC and ES cells by way of embryo-like aggregates (embryoid bodies) into spontaneously beating cardiomyocytes. During cardiomyocyte differentiation three distinct developmental stages were defined by expression of specific action potentials and ionic currents measured by the whole-cell patch-clamp technique. Whereas early differentiated cardiomyocytes are characterized by action potentials and ionic currents typical for early pacemaker cells, terminally differentiated cardiomyocytes show action potentials and ionic currents inherent to ventricular-, atrial- or sinus nodal-like cells. These functional characteristics are in accordance with the expression of alpha- and beta-cardiac myosin heavy chain at early differentiation stages and the additional expression of ventricular-specific MLC-2V and atrial-specific ANF genes at terminal stages demonstrated by reverse transcription polymerase chain reaction (RT-PCR) analysis. Pharmacological studies performed by measuring chronotropic responses and by analysing the Ca(2+) channel activity correspond to data obtained with cardiac cells from living organisms. For testing the influence of exogenous compounds on cardiac differentiation the teratogenic compound retinoic acid (RA) was applied during distinct stages of embryoid body development. A temporally controlled influence of RA on cardiac differentiation and expression of cardiac-specific genes was found. We conclude that ES cell-derived cardiomyocytes provide an excellent cellular model to study early cardiac development and to perform pharmacological and embryotoxicological investigations.

(Pro)renin receptor triggers distinct angiotensin II-independent extracellular matrix remodeling and deterioration of cardiac function

Background

Activation of the renin-angiotensin-system (RAS) plays a key pathophysiological role in heart failure in patients with hypertension and myocardial infarction. However, the function of (pro)renin receptor ((P)RR) is not yet solved. We determined here the direct functional and structural effects of (P)RR in the heart.

Methodology/Principal Findings

(P)RR was overexpressed by using adenovirus-mediated gene delivery in normal adult rat hearts up to 2 weeks. (P)RR gene delivery into the anterior wall of the left ventricle decreased ejection fraction (P<0.01), fractional shortening (P<0.01), and intraventricular septum diastolic and systolic thickness, associated with approximately 2–fold increase in left ventricular (P)RR protein levels at 2 weeks. To test whether the worsening of cardiac function and structure by (P)RR gene overexpression was mediated by angiotensin II (Ang II), we infused an AT₁ receptor blocker losartan via osmotic minipumps. Remarkably, cardiac function deteriorated in losartan-treated (P)RR overexpressing animals as well. Intramyocardial (P)RR gene delivery also resulted in Ang II-independent activation of extracellular-signal-regulated kinase1/2 phosphorylation and myocardial fibrosis, and the expression of transforming growth factor-β1 and connective tissue growth factor genes. In contrast, activation of heat shock protein 27 phosphorylation and apoptotic cell death by (P)RR gene delivery was Ang II-dependent. Finally, (P)RR overexpression significantly increased direct protein–protein interaction between (P)RR and promyelocytic zinc-finger protein.

Conclusions/Significance

These results indicate for the first time that (P)RR triggers distinct Ang II-independent myocardial fibrosis and deterioration of cardiac function in normal adult heart and identify (P)RR as a novel therapeutic target to optimize RAS blockade in failing hearts.

Prevention of coronary in-stent restenosis and vein graft failure: does vascular gene therapy have a role?

Coronary artery bypass grafting (CABG) and percutaneous coronary intervention (PCI), including stent insertion, are established therapies in both acute coronary syndromes (ACS) and symptomatic chronic coronary artery disease refractory to pharmacological therapy. These continually advancing treatments remain limited by failure of conduit grafts in CABG and by restenosis or thrombosis of stented vessel segments in PCI caused by neointimal hyperplasia, impaired endothelialisation and accelerated atherosclerosis. While pharmacological and technological advancements have improved patient outcomes following both procedures, when grafts or stents fail these result in significant health burdens. In this review we discuss the pathophysiology of vein graft disease and in-stent restenosis, gene therapy vector development and design, and translation from pre-clinical animal models through human clinical trials. We identify the key issues that are currently preventing vascular gene therapy from interfacing with clinical use and introduce the areas of research attempting to overcome these.

Electroporation-mediated gene transfer directly to the swine heart

In vivo gene transfer to the ischemic heart via electroporation holds promise as a potential therapeutic approach for the treatment of heart disease. In the current study, we investigated the use of in vivo electroporation for gene transfer using three different penetrating electrodes and one non-penetrating electrode. The hearts of adult male swine were exposed through a sternotomy. Eight electric pulses synchronized to the rising phase of the R wave of the electrocardiogram were administered at varying pulse widths and field strengths following an injection of either a plasmid encoding luciferase or one encoding green fluorescent protein. Four sites on the anterior wall of the left ventricle were treated. Animals were killed 48 h after injection and electroporation and gene expression was determined. Results were compared with sites in the heart that received plasmid injection but no electric pulses or were not treated. Gene expression was higher in all electroporated sites when compared with injection only sites demonstrating the robustness of this approach. Our results provide evidence that in vivo electroporation can be a safe and effective non-viral method for delivering genes to the heart, in vivo.

Empowering adult stem cells for myocardial regeneration

Treatment strategies for heart failure remain a high priority for ongoing research due to the profound unmet need in clinical disease coupled with lack of significant translational progress. The underlying issue is the same whether the cause is acute damage, chronic stress from disease, or aging: progressive loss of functional cardiomyocytes and diminished hemodynamic output. To stave off cardiomyocyte losses, a number of strategic approaches have been embraced in recent years involving both molecular and cellular approaches to augment myocardial structure and performance. Resultant excitement surrounding regenerative medicine in the heart has been tempered by realizations that reparative processes in the heart are insufficient to restore damaged myocardium to normal functional capacity and that cellular cardiomyoplasty is hampered by poor survival, proliferation, engraftment, and differentiation of the donated population. To overcome these limitations, a combination of molecular and cellular approaches must be adopted involving use of genetic engineering to enhance resistance to cell death and increase regenerative capacity. This review highlights biological properties of approached to potentiate stem cell-mediated regeneration to promote enhanced myocardial regeneration, persistence of donated cells, and long-lasting tissue repair. Optimizing cell delivery and harnessing the power of survival signaling cascades for ex vivo genetic modification of stem cells before reintroduction into the patient will be critical to enhance the efficacy of cellular cardiomyoplasty. Once this goal is achieved, then cell-based therapy has great promise for treatment of heart failure to combat the loss of cardiac structure and function associated with acute damage, chronic disease, or aging.

The evolution of heart gene delivery vectors

Gene therapy holds promise for treating numerous heart diseases. A key premise for the success of cardiac gene therapy is the development of powerful gene transfer vehicles that can achieve highly efficient and persistent gene transfer specifically in the heart. Other features of an ideal vector include negligible toxicity, minimal immunogenicity and easy manufacturing. Rapid progress in the fields of molecular biology and virology has offered great opportunities to engineer various genetic materials for heart gene delivery. Several nonviral vectors (e.g. naked plasmids, plasmid lipid/polymer complexes and oligonucleotides) have been tested. Commonly used viral vectors include lentivirus, adenovirus and adeno-associated virus. Among these, adeno-associated virus has shown many attractive features for pre-clinical experimentation in animal models of heart diseases. We review the history and evolution of these vectors for heart gene transfer.

Current strategies for myocardial gene delivery

Existing methods of cardiac gene delivery can be classified by the site of injection, interventional approach and type of cardiac circulation at the time of transfer. General criteria to assess the efficacy of a given delivery method include: global versus regional myocardial transduction, technical complexity and the pathophysiological effects associated with its use, delivery-related collateral expression and the delivery-associated inflammatory and immune response. Direct gene delivery (intramyocardial, endocardial, epicardial) may be useful for therapeutic angiogenesis and for focal arrhythmia therapy but with gene expression which is primarily limited to regions in close proximity to the injection site. An often unappreciated limitation of these techniques is that they are frequently associated with substantial systemic vector delivery. Percutaneous infusion of vector into the coronary arteries is minimally invasive and allows for transgene delivery to the whole myocardium. Unfortunately, efficiency of intracoronary delivery is highly variable and the short residence time of vector within the coronary circulation and significant collateral organ expression limit its clinical potential. Surgical techniques, including the incorporation of cardiopulmonary bypass with isolated cardiac recirculation, represent novel delivery strategies that may potentially overcome these limitations; yet, these techniques are complex with inherent morbidity that must be thoroughly evaluated before safe translation into clinical practice. Characteristics of the optimal technique for gene delivery include low morbidity, increased myocardial transcapillary gradient, extended vector residence time in the coronary circulation and exclusion of residual vector from the systemic circulation after delivery to minimize extracardiac expression and to mitigate a cellular immune response. This article is part of a Special Section entitled "Special Section: Cardiovascular Gene Therapy".

Gene therapy for heart failure

Despite the progress achieved in conventional treatment modalities, heart failure remains a major cause of mortality and morbidity. The identification of novel signaling pathways has provided a solid scientific rationale which has stimulated preclinical development of gene-based therapies for heart failure. Advances in somatic gene transfer technologies have been crucial to the advent of the first human clinical trials which are currently in progress. As these and other trials of gene transfer-based therapies are initiated, these approaches have generated excitement and hope for novel treatments for cardiovascular disease. In this review, we present a summary of advancements in construction of different vectors and methods of delivery that have been used for specific myocardial gene delivery. In addition, we will show results from studies focusing on the use of gene therapy to target heart failure mechanisms in animal models of cardiac dysfunction. Finally, we discuss the limited but highly promising results from clinical studies that have served as catalysts to translate preclinical achievements towards new treatment modalities for heart failure.

Cardiac gene therapy: optimization of gene delivery techniques in vivo

Vector-mediated cardiac gene therapy holds tremendous promise as a translatable platform technology for treating many cardiovascular diseases. The ideal technique is one that is efficient and practical, allowing for global cardiac gene expression, while minimizing collateral expression in other organs. Here we survey the available in vivo vector-mediated cardiac gene delivery methods--including transcutaneous, intravascular, intramuscular, and cardiopulmonary bypass techniques--with consideration of the relative merits and deficiencies of each. Review of available techniques suggests that an optimal method for vector-mediated gene delivery to the large animal myocardium would ideally employ retrograde and/or anterograde transcoronary gene delivery,extended vector residence time in the coronary circulation, an increased myocardial transcapillary gradient using physical methods, increased endothelial permeability with pharmacological agents, minimal collateral gene expression by isolation of the cardiac circulation from the systemic, and have low immunogenicity.

A simple technique to establish a long-term adenovirus mediated gene transfer to the heart of newborn mice

Previous studies using different techniques have shown that adenoviral-mediated gene transfer to different tissues, including the kidney, is more efficient in neonatal mice. In this study, we report a simple technique that allows an efficient and long term expression of beta-galactosidase (beta-gal) in the heart of newborn mice. Newborn and adult C57BL6/J mice were subjected to a single retro-orbital venous plexus injection of recombinant adenoviral vectors (rAd) (2 x 10(9) particles/g body weight) carrying the lac Z gene. Seven days after the injection, positive beta-gal staining was systematically observed in the heart, lung, intestine, liver, kidney and spleen of newborn mice. However, only the heart showed persistent expression of beta-gal one year after the initial injection. In contrast, adult mice showed only significant but transient beta-gal expression mainly in the liver. In summary, we have found that a single retro-orbital intravenous injection can be used to establish a long-term adenoviral-mediated gene transfer to cardiac cells of newborn mice.

Herpesvirus-mediated delivery of a genetically encoded fluorescent Ca(2+) sensor to canine cardiomyocytes

We report the development and application of a pseudorabies virus-based system for delivery of troponeon, a fluorescent Ca²⁺ sensor to adult canine cardiomyocytes. The efficacy of transduction was assessed by calculating the ratio of fluorescently labelled and nonlabelled cells in cell culture. Interaction of the virus vector with electrophysiological properties of cardiomyocytes was evaluated by the analysis of transient outward current (I_to), kinetics of the intracellular Ca²⁺ transients, and cell shortening. Functionality of transferred troponeon was verified by FRET analysis. We demonstrated that the transfer efficiency of troponeon to cultured adult cardiac myocytes was virtually 100%. We showed that even after four days neither the amplitude nor the kinetics of the I_to current was significantly changed and no major shifts occurred in parameters of [Ca²⁺]_i transients. Furthermore, we demonstrated that infection of cardiomyocytes with the virus did not affect the morphology, viability, and physiological attributes of cells.

Refinement of in vivo surgical procedures for cardiac gene and cell transfer in rats

In studies of gene and cell transfer for the treatment of heart disease, direct intramyocardial injection and antegrade intracoronary injection are common methods of delivering biomaterials to the heart. The authors, who carried out these surgical procedures in 377 rats, describe their methodology in detail and discuss surgical refinements that substantially reduced rat mortality. These refinements include a rigorous fluid replacement regimen, use of inhalational anesthesia instead of injectable agents, exposure of the heart without direct contact and use of a chest drainage cannula to remove air from the pleural cavity and prevent lung collapse.

Designing heart performance by gene transfer

The birth of molecular cardiology can be traced to the development and implementation of high-fidelity genetic approaches for manipulating the heart. Recombinant viral vector-based technology offers a highly effective approach to genetically engineer cardiac muscle in vitro and in vivo. This review highlights discoveries made in cardiac muscle physiology through the use of targeted viral-mediated genetic modification. Here the history of cardiac gene transfer technology and the strengths and limitations of viral and nonviral vectors for gene delivery are reviewed. A comprehensive account is given of the application of gene transfer technology for studying key cardiac muscle targets including Ca(2+) handling, the sarcomere, the cytoskeleton, and signaling molecules and their posttranslational modifications. The primary objective of this review is to provide a thorough analysis of gene transfer studies for understanding cardiac physiology in health and disease. By comparing results obtained from gene transfer with those obtained from transgenesis and biophysical and biochemical methodologies, this review provides a global view of cardiac structure-function with an eye towards future areas of research. The data presented here serve as a basis for discovery of new therapeutic targets for remediation of acquired and inherited cardiac diseases.

Viral IL-10 gene transfer prolongs rat islet allograft survival

Islet transplantation is a potential cure for diabetes. However, allotransplant rejection severely limits its clinical application. In this study, we sought to transfect rat islets with an adenoviral vector containing the viral IL-10 (vIL-10) gene and examine its efficacy in preventing graft rejection. The immunosuppressive effect of vIL-10 is reported but its efficacy is somehow debatable in transplantation model. vIL-10 transfected islets were transplanted into streptozotocin-induced diabetic rats. Blood glucose, serum vIL-10 concentration, graft histology, and graft cytokine expression were used to monitor graft function up to day 21 after transplantation. Transfected islets released a large amount of vIL-10 protein without affecting their viability and functional integrity. When we transplanted the transfected islets into allogeneic hosts, the survival of grafted islets was not significantly increased. However, the combined use of vIL-10 and subtherapeutic doses of CsA (cyclosporine) significantly prolonged graft survival beyond that achieved with either agent alone (p < 0.001). vIL-10 and CsA-treated rats contain high level of vIL-10 in serum, which is evidenced by the inhibition of allogeneic mixed lymphocyte reaction (MLR). Histological analysis additionally revealed the presence of viable islets up to 21 days. IL-10 mRNA expression in grafted liver was higher and IFN-gamma mRNA was lower in vIL-10 and CsA-treated animals, compared with other groups. The synergistic effect of this combination therapy is potentially correlated with the induction of inhibitory cytokine secretion and downregulation of proinflammatory cytokine secretion from host cells.

Advances in gene-based therapy for heart failure

Heart failure is a major cause of morbidity and mortality in western countries. While progress in current treatment modalities is making steady and incremental gains to reduce this disease burden, there remains a need to explore novel therapeutic strategies. Clinicians and researchers alike have thus looked towards novel adjunctive therapeutic strategies, including gene-based therapy for congestive heart failure (CHF). Advances in the understanding of the molecular basis of CHF, combined to the evolution of increasingly efficient gene transfer technology, have placed congestive heart failure within reach of gene-based therapy. This review will discuss issues related to gene vector systems, gene delivery strategies, and gene targets for intervention in the setting of CHF.

Design of a phase 1/2 trial of intracoronary administration of AAV1/SERCA2a in patients with heart failure

BACKGROUND

Heart failure (HF) remains a major cause of morbidity and mortality in North America. With an aging population and an unmet clinical need by current pharmacologic and device-related therapeutic strategies, novel treatment options for HF are being explored. One such promising strategy is gene therapy to target underlying molecular anomalies in the dysfunctional cardiomyocyte. Prior animal and human studies have documented decreased expression of SERCA2a, a major cardiac calcium cycling protein, as a major defect found in HF.

METHODS AND RESULTS

We hypothesize that increasing the activity of SERCA2a in patients with moderate to severe HF will improve their cardiac function, disease status, and quality of life. Gene transfer of SERCA2a will be performed via an adeno-associated viral (AAV) vector, derived from a nonpathogenic virus with long-term transgene expression as well as a clinically established favorable safety profile.

CONCLUSIONS

We describe the design of a phase 1 clinical trial of antegrade epicardial coronary artery infusion (AECAI) administration of AAVI/SERCA2a (MYDICAR) to subjects with HF divided into 2 stages: in Stage 1, subjects will be assigned open-label MYDICAR in one of up to 4 sequential dose escalation cohorts; in Stage 2, subjects will be randomized in parallel to 2 or 3 doses of MYDICAR or placebo in a double-blinded manner.

Preservation of mechanical and energetic function after adenoviral gene transfer in normal rat hearts

1. The aim of the present study was to examine the acute and chronic effects of adenoviral gene transfer on cardiac function in terms of left ventricular (LV) mechanoenergetic function. Recombinant adenoviral vector carrying beta-galactosidase and green fluorescent protein genes (Ad.betagal-GFP) was used. Cardiac function was examined in cross-circulated rat heart preparations, where end-systolic/diastolic pressure-volume relationships (ESPVR/EDPVR), systolic pressure-volume area (PVA), LV relaxation rate, equivalent maximal elastance at mid-range LV volume (eE(max) at mLVV), coronary blood flow, coronary vascular resistance and myocardial oxygen consumption (VO(2)) were also measured. 2. To examine the ex vivo acute effects of the adenoviral vector, data were obtained before and 30-90 min after intracoronary infusion of Ad.betagal-GFP in the excised, cross-circulated hearts that underwent serotonin pretreatment. To examine the in vivo chronic effects of adenoviral gene transfer, normal rat hearts received Ad.betagal-GFP or saline by a catheter-based technique and data were obtained 3 days after the injection of Ad.betagal-GFP or saline. 3. The ESPVR, EDPVR, LV relaxation rate, eE(max) at mLVV, coronary blood flow and coronary vascular resistance remained unchanged in Ad.betagal-GFP-transfected hearts in both ex vivo acute and in vivo chronic experiments. Moreover, the ex vivo and in vivo transfection caused no change in the slope and VO(2) intercept of the VO(2)-PVA relationship, VO(2) for basal metabolism and for Ca(2+) handling in excitation-contraction coupling and O(2) costs of LV contractility. 4. These results indicate that adenoviral gene transfer has neither acute nor chronic toxic effects on LV mechanical and energetic function. A special combination of in vivo adenoviral gene transfer and a cross-circulation experimental system may provide a useful novel strategy to explore the functional and mechanoenergetic role of specifically targeted genes in the diseased heart.

Gene Therapy for Cardiac Arrhythmias: A Dream Soon to Come True?

Alternatively, excitement and frustration have been generated from the literature reports of gene therapy for treatment and potential cure of cardiac diseases. The time since the first literature report of in vivo myocardial gene transfer is more than 15 years, and the time since the first report of gene therapy for a cardiac arrhythmia is six years. Clinical trials, let alone clinical usage, of these promising therapies have not yet started. This article reviews the current state of the art for arrhythmia gene therapy, including the literature reports of antiarrhythmic studies and of problems within the field. Gene transfer continues to be a promising technology, but patience is required as these problems are solved and the therapies make their way through the preclinical and clinical testing process.

Recombinant adeno-associated virus vector for gene transfer to the transplanted rat heart

Efficient durable viral vector transduction of the transplanted heart remains elusive. This study assesses the potential of recombinant adeno-associated virus (rAAV) mediated gene delivery to the transplanted rat heart. rAAV serotype 1, 2 and 5 vectors encoding the green fluorescent protein (GFP) gene (1 x 10(11) viral particles/ml) were diluted in cold University of Wisconsin solution and circulated through the coronary vasculature of the donor organs for 30 min before syngeneic rat heterotopic heart transplantation was performed. Study 1: animals (n = 5 each serotype) were killed at 21 days post-transplant to evaluate the efficiency of GFP transduction using RT-PCR and expression by fluorescence microscopy. Study 2: using rAAV-1, animals (n = 5 each group) were killed at 7, 21 and 84 days to evaluate the durability of GFP expression. The maximum cardiac GFP expression at 21 days was observed in rAAV-1. GFP expression by rAAV-1 was detectable at 7 days, improved at 21 days, and was still evident at 84 days. This study demonstrates cardiac rAAV gene transduction with a cold perfusion preservation system of the donor heart. These data show that AAV-1 is superior to AAV-2 and AAV-5 for this purpose and that durable expression is achievable.

Targeted high-efficiency, homogeneous myocardial gene transfer

Myocardial gene therapy continues to show promise as a tool for investigation and treatment of cardiac disease. Progress toward clinical approval has been slowed by limited in vivo delivery methods. We investigated the problem in a porcine model, with an objective of developing a method for high efficiency, homogeneous myocardial gene transfer that could be used in large mammals, and ultimately in humans. Eighty-one piglets underwent coronary catheterization for delivery of viral vectors into the left anterior descending artery and/or the great cardiac vein. The animals were followed for 5 or 28 days, and then transgene efficiency was quantified from histological samples. The baseline protocol included treatment with VEGF, nitroglycerin, and adenosine followed by adenovirus infusion into the LAD. Gene transfer efficiency varied with choice of viral vector, with use of VEGF, adenosine, or nitroglycerin, and with calcium concentration. The best results were obtained by manipulation of physical parameters. Simultaneous infusion of adenovirus through both left anterior descending artery and great cardiac vein resulted in gene transfer to 78+/-6% of myocytes in a larger target area. This method was well tolerated by the animals. We demonstrate targeted, homogeneous, high efficiency gene transfer using a method that should be transferable for eventual human usage.

Percutaneous intracoronary delivery of SERCA gene increases myocardial function: a tissue Doppler imaging echocardiographic study

The aim of this study was to examine the efficiency of adenovirus-mediated overexpression of sarco(endo)plasmic reticulum Ca(2+)-ATPase (SERCA1a) gene in a realistic model based on percutaneous intracoronary delivery and on noninvasive functional monitoring. Catheter-based selective coronary delivery of saline or adenoviruses (Ad.CMV.SERCA1a or Ad.CMV.lacZ, 10(10) plaque-forming units) was performed in the circumflex artery of rabbits. Effects were assessed and compared by using serial Doppler echocardiography, hemodynamics, and measurements of SERCA protein and Ca(2+) uptake activity. On day 3, a 21% increase in SERCA proteins and a 37% increase in the maximal rate of Ca(2+) uptake were observed in the transfected left ventricular (LV) walls of Ad.CMV.SERCA1a rabbits. Baseline hemodynamics and conventional echographic measurements of global LV function were poorly affected. In contrast, tissue Doppler imaging (TDI) was able to assess a strong increase in the baseline function of transfected LV walls, as assessed with maximal wall velocities (+32% and +43%, respectively) and strain rates (+18% and +30%, respectively). TDI parameters were closely related to the maximal rate of Ca(2+) uptake (r(2) = 0.68 for the systolic strain rate). Serial TDI analysis during follow-up showed that the effects lasted for 7 days and were no longer detectable 15 days after adenoviruses injection. In conclusion, LV function can be increased by adenovirus-mediated overexpression of SERCA in a clinically relevant model, and TDI provides an accurate and noninvasive tool for monitoring effects on global as well as regional myocardial function.

Human gene therapy and imaging: cardiology

This review discusses the basics of cardiovascular gene therapy, the results of recent human clinical trials, and the rapid progress in imaging techniques in cardiology. Improved understanding of the molecular and genetic basis of coronary heart disease has made gene therapy a potential new alternative for the treatment of cardiovascular diseases. Experimental studies have established the proof-of-principle that gene transfer to the cardiovascular system can achieve therapeutic effects. First human clinical trials provided initial evidence of feasibility and safety of cardiovascular gene therapy. However, phase II/III clinical trials have so far been rather disappointing and one of the major problems in cardiovascular gene therapy has been the inability to verify gene expression in the target tissue. New imaging techniques could significantly contribute to the development of better gene therapeutic approaches. Although the exact choice of imaging modality will depend on the biological question asked, further improvement in image resolution and detection sensitivity will be needed for all modalities as we move from imaging of organs and tissues to imaging of cells and genes.

Transthoracic direct current shock facilitates intramyocardial transfection of naked plasmid DNA infused via coronary vessels in canines

Catheter-mediated, percutaneous, transluminal delivery of naked plasmid DNA (pDNA) into myocardium may offer a valuable strategy to heart diseases. Here, we examined whether clinically available transthoracic direct current (DC) shock improves intracoronary naked DNA transfection into myocardium. Plasmid vector encoding the GL3 luciferase was infused retrogradely into the coronary veins of beagle dogs, whereas another pDNA solution was infused into the left coronary artery. During and after these procedures, the coronary venous sinus was occluded by balloon, and transthoracic DC shock of 200 J was applied immediately after the infusions. Without DC shock, no remarkable increase in luciferase activity was demonstrated in any part of the left ventricular myocardium. In the presence of DC pulsation, significant luciferase expression was detected in the regions that were supplied by left anterior descending coronary artery (LAD), whereas the gene expression in the right coronary artery (RCA) regions was much less drastic. X-gal (5-bromo-4-chloro-3-indolyl-beta-D-galactoside) staining of cardiac cross-sections also revealed regional expression of beta-galactosidase. Immunohistochemical examinations of heart cryosections revealed that cardiomyocytes in LAD regions successfully expressed transgene product. The present system may enable a new strategy for myocardial gene therapy, without any special device or technique other than cardiac catheterization and DC cardioversion that are generally performed in ordinary hospitals.

Development of novel method of non-viral efficient gene transfer into neonatal cardiac myocytes

To establish new treatment for cardiovascular disease, the development of safe and highly efficient vectors is necessary. Especially, non-viral vectors are considered to be ideal for human gene therapy, since recent adverse events with retroviral or adenoviral vectors have highlighted the issue of safety. Although we previously reported safety and high efficiency of HVJ-liposome method, we have modified the envelope of HVJ (Sendai virus). In this novel non-viral vector, the envelope of HVJ alone was utilized as a carrier to deliver proteins, genes and oligodeoxynucleotides (ODN). Thus, we optimized the transfection efficiency of HVJ-envelope vector into neonatal cardiac myocytes in this study, since cardiac myocytes is one of the most difficult cells to be transfected. HVJ-envelope, obtained after complete destruction of HVJ genome, containing FITC-labeled ODN or luciferase plasmid was incubated with cardiac myocytes. In addition, the concentration of protamine sulfate was modified (0-700 microg/ml) to increase transfection efficacy. Without HVJ-envelope vector, few cells showed fluorescence, whereas most cells demonstrated fluorescence with HVJ-envelope vector. Consistent with the high transfection efficiency of ODN, high luciferase activity was also detected using HVJ-envelope vector. Moreover, the transfection efficiency varied according to the concentration of protamine sulfate. No obvious cytotoxicity was observed in cells transfected with HVJ-envelope vector. The present study demonstrated the development of a highly efficient novel non-viral vector for cardiac myocytes, suggesting that further development may provide a new useful tool for research and clinical gene therapy in the field of cardiovascular disease.