Reversal of cardiac dysfunction after long-term expression of SERCA2a by gene transfer in a pre-clinical model of heart failure

Assessing left ventricular systolic dysfunction after myocardial infarction: are ejection fraction and dP/dt(max) complementary or redundant?

Among the various cardiac contractility parameters, left ventricular (LV) ejection fraction (EF) and maximum dP/dt (dP/dt(max)) are the simplest and most used. However, these parameters are often reported together, and it is not clear if they are complementary or redundant. We sought to compare the discriminative value of EF and dP/dt(max) in assessing systolic dysfunction after myocardial infarction (MI) in swine. A total of 220 measurements were obtained. All measurements included LV volumes and EF analysis by left ventriculography, invasive ventricular pressure tracings, and echocardiography. Baseline measurements were performed in 132 pigs, and 88 measurements were obtained at different time points after MI creation. Receiver operator characteristic (ROC) curves to distinguish the presence or absence of an MI revealed a good predictive value for EF [area under the curve (AUC): 0.998] but not by dP/dt(max) (AUC: 0.69, P < 0.001 vs. EF). Dividing dP/dt(max) by LV end-diastolic pressure and heart rate (HR) significantly increased the AUC to 0.87 (P < 0.001 vs. dP/dt(max) and P < 0.001 vs. EF). In naïve pigs, the coefficient of variation of dP/dt(max) was twice than that of EF (22.5% vs. 9.5%, respectively). Furthermore, in n = 19 pigs, dP/dt(max) increased after MI. However, echocardiographic strain analysis of 23 pigs with EF ranging only from 36% to 40% after MI revealed significant correlations between dP/dt(max) and strain parameters in the noninfarcted area (circumferential strain: r = 0.42, P = 0.05; radial strain: r = 0.71, P < 0.001). In conclusion, EF is a more accurate measure of systolic dysfunction than dP/dt(max) in a swine model of MI. Despite the variability of dP/dt(max) both in naïve pigs and after MI, it may sensitively reflect the small changes of myocardial contractility.

Cardiac gene therapy in large animals: bridge from bench to bedside

Several clinical trials are evaluating gene transfer as a therapeutic approach to treat cardiac diseases. Although it has just started on the path to clinical application, recent advances in gene delivery technologies with increasing knowledge of underlying mechanisms raise great expectations for the cardiac gene therapy. Although in vivo experiments using small animals provide the therapeutic potential of gene transfer, there exist many fundamental differences between the small animal and the human hearts. Before applying the therapy to clinical patients, large animal studies are a prerequisite to validate the efficacy in an animal model more relevant to the human heart. Several key factors including vector type, injected dose, delivery method and targeted cardiac disease are all important factors that determine the therapeutic efficacy. Selecting the most optimal combination of these factors is essential for successful gene therapy. In addition to the efficacy, safety profiles need to be addressed as well. In this regard, large animal studies are best suited for comprehensive evaluation at the preclinical stages of therapeutic development to ensure safe and effective gene transfer. As the cardiac gene therapy expands its potential, large animal studies will become more important to bridge the bench side knowledge to the clinical arena.

AAV6.βARKct cardiac gene therapy ameliorates cardiac function and normalizes the catecholaminergic axis in a clinically relevant large animal heart failure model

AIMS

G protein-coupled receptor kinase 2 (GRK2), which is markedly upregulated in failing human myocardium, has been implicated as a contributing factor or consequence of heart failure (HF). Importantly, cardiac-specific GRK2 knockout mice have recently proved the pathological nature of GRK2 in HF. Targeted inhibition of GRK2 is possible using a peptide inhibitor known as the βARKct, which has rescued several disparate small animal HF models. This study was designed to evaluate long-term βARKct expression in a clinically relevant large animal HF model, using stable myocardial gene delivery with adeno-associated virus serotype 6 (AAV6).

METHODS AND RESULTS

A porcine model of HF subsequent to left ventricular (LV) myocardial infarction (MI) was used to study the effects of retrograde injection into the anterior interventricular vein of either AAV6.βARKct or AAV6.luciferase as a control 2 weeks after MI. Echocardiography and LV hemodynamics were performed before and 6 weeks after gene transfer. Robust and long-term βARKct expression was found after AAV6-mediated delivery, leading to significant amelioration of LV haemodynamics and contractile function in HF pigs compared with AAV6.luciferase-treated control animals that showed a continued decline in cardiac function. Interestingly, the neurohormonal axis was virtually normalized in AVV6.βARKct-treated HF animals, represented by reductions in plasma norepinephrine levels, whereas AAV6.luciferase-treated pigs showed further increases in plasma catecholamine levels. As a result, LV remodelling and foetal gene expression was reversed by AVV6.βARKct gene therapy.

CONCLUSION

These data--showing sustained amelioration of cardiac function in a post-MI pig HF model--demonstrate the therapeutic potential of βARKct gene therapy for HF.

Concomitant intravenous nitroglycerin with intracoronary delivery of AAV1.SERCA2a enhances gene transfer in porcine hearts

SERCA2a gene therapy improves contractile and energetic function of failing hearts and has been shown to be associated with benefits in clinical outcomes, symptoms, functional status, biomarkers, and cardiac structure in a phase 2 clinical trial. In an effort to enhance the efficiency and homogeneity of gene uptake in cardiac tissue, we examined the effects of nitroglycerin (NTG) in a porcine model following AAV1.SERCA2a gene delivery. Three groups of Göttingen minipigs were assessed: (i) group A: control intracoronary (IC) AAV1.SERCA2a (n = 6); (ii) group B: a single bolus IC injection of NTG (50 µg) immediately before administration of intravenous (IV) AAV1.SERCA2a (n = 6); and (iii) group C: continuous IV NTG (1 µg/kg/minute) during the 10 minutes of AAV1.SERCA2a infusion (n = 6). We found that simultaneous IV infusion of NTG and AAV1.SERCA2a resulted in increased viral transduction efficiency, both in terms of messenger RNA (mRNA) as well as SERCA2a protein levels in the whole left ventricle (LV) compared to control animals. On the other hand, IC NTG pretreatment did not result in enhanced gene transfer efficiency, mRNA or protein levels when compared to control animals. Importantly, the transgene expression was restricted to the heart tissue. In conclusion, we have demonstrated that IV infusion of NTG significantly improves cardiac gene transfer efficiency in porcine hearts.

Exploiting natural diversity of AAV for the design of vectors with novel properties

Twelve AAV serotypes have been described so far in human and nonhuman primate (NHP) populations while surprisingly high diversity of AAV sequences is detected in tissue biopsies. The analysis of these novel AAV sequences has indicated a rapid evolution of the viral genome both by accumulation of mutations and recombination. This chapter describes how this rich resource of naturally evolved sequences is used to derive gene transfer vectors with a wide array of activities depending on the nature of the cap gene used in the packaging system. AAV2-based recombinant genomes have been packaged in dozens of different capsid types, resulting in a wide array of "pseudotyped vectors" that constitute a rich resource for the development of gene therapy clinical trials. We describe a polymerase chain reaction-based molecular rescue method for novel AAV isolation that uses primers designed to recognize the highly conserved regions in known AAV isolates and generate amplicons across the hypervariable regions of novel AAV genomes present in the analyzed sample.

Reverse remodeling in heart failure--mechanisms and therapeutic opportunities

Heart failure (HF) involves changes in cardiac structure, myocardial composition, myocyte deformation, and multiple biochemical and molecular alterations that impact heart function and reserve capacity. Collectively, these changes have been referred to as 'cardiac remodeling'. Understanding the components of this process with the goal of stopping or reversing its progression has become a major objective. This concept is often termed 'reverse remodeling', and is successfully achieved by inhibitors of the renin-angiotensin-aldosterone system, β-blockers, and device therapies such as cardiac resynchronization or ventricular assist devices. Not every method of reverse remodeling has long-lasting clinical efficacy. However, thus far, every successful clinical treatment with long-term benefits on the morbidity and mortality of patients with HF reverses remodeling. Reverse remodeling is defined by lower chamber volumes (particularly end-systolic volume) and is often accompanied by improved β-adrenergic and heart-rate responsiveness. At the cellular level, reverse remodeling impacts on myocyte size, function, excitation-contraction coupling, bioenergetics, and a host of molecular pathways that regulate contraction, cell survival, mitochondrial function, oxidative stress, and other features. Here, we review the current evidence for reverse remodeling by existing therapies, and discuss novel approaches that are rapidly moving from preclinical to clinical trials.

Chronic heart failure: current evidence, challenges to therapy, and future directions

Heart failure (HF) is a complex syndrome characterized by the inability of the heart to maintain a normal cardiac output without elevated intracardiac filling pressures, resulting in signs of pulmonary and peripheral edema and symptoms of dyspnea and fatigue. Central to the management of HF is a multifaceted pharmacological intervention to abate the harmful counter-regulatory effects of neurohormonal activation and avid salt and water retention. Whereas up to 40 years ago HF was managed with diuretics and leaf of digitalis, the cornerstones of therapy for HF patients with systolic dysfunction now include ACE inhibitors or angiotensin II type 1 receptor antagonists (angiotensin receptor blockers), β-adrenoceptor antagonists (β-blockers), and aldosterone antagonists, which have significantly improved survival. However, with the increasing number of beneficial therapies, there are challenges to implementing all of them. Specific cardiomyopathies also merit specific considerations with respect to treatment, and - unfortunately - there is no therapy for HF with preserved left ventricular ejection fraction that has been shown to improve survival. Although mortality has improved in HF, the biggest challenge to treatment lies in addressing the morbidity of this disease, which is now the most common reason for hospital admission in our aged population. As such, there are many therapies that may serve to improve the quality of life of HF patients. Future HF treatment regimens may include direct cellular therapy via hormone and cytokine signaling or cardiac regeneration through growth factors or cell therapy.

Neutralizing antibodies against AAV serotypes 1, 2, 6, and 9 in sera of commonly used animal models

Adeno-associated virus (AAV)-based vectors are promising gene delivery vehicles for human gene transfer. One significant obstacle to AAV-based gene therapy is the high prevalence of neutralizing antibodies in humans. Until now, it was thought that, except for nonhuman primates, pre-existing neutralizing antibodies are not a problem in small or large animal models for gene therapy. Here, we demonstrate that sera of several animal models of cardiovascular diseases harbor pre-existing antibodies against the cardiotropic AAV serotypes AAV1, AAV6, and AAV9 and against AAV2. The neutralizing antibody titers vary widely both between species and between serotypes. Of all species tested, rats displayed the lowest levels of neutralizing antibodies. Surprisingly, naive mice obtained directly from commercial vendors harbored neutralizing antibodies. Of the large animal models tested, the neutralization of AAV6 transduction by dog sera was especially pronounced. Sera of sheep and rabbits showed modest neutralization of AAV transduction whereas porcine sera strongly inhibited transduction by all AAV serotypes and displayed the largest variation between individual animals. Importantly, neutralizing antibody titers as low as 1/4 completely prevented in vivo transduction by AAV9 in rats. Our results suggest that prescreening of animals for neutralizing antibodies will be important for future gene transfer experiments in these animal models.

SUMO1-dependent modulation of SERCA2a in heart failure

SR Ca²⁺ ATPase 2a (SERCA2a) is a critical ATPase responsible for Ca²⁺ re-uptake during excitation-contraction coupling. Impaired SR Ca²⁺ uptake resulting from decreased expression and reduced activity of SERCA2a is a hallmark of heart failure (HF)¹. Accordingly, restoration of SERCA2a expression by gene transfer has proven to be effective in improving cardiac function in HF patients² as well as in animal models³. The small ubiquitin-related modifier (SUMO) can be conjugated to lysine residues of target proteins⁴, which is involved in most cellular process⁵. Here, we show that SERCA2a is SUMOylated at lysine 480 and 585 and that this SUMOylation is essential for preserving SERCA2a ATPase activity and stability. The levels of SUMO1 and SUMOylation of SERCA2a itself were greatly reduced in failing hearts. SUMO1 restitution by adeno-associated virus-mediated gene delivery maintained protein abundance of SERCA2a and significantly improved cardiac function in HF mice. This effect was comparable to SERCA2a gene delivery. Moreover, SUMO1 overexpression in isolated cardiomyocytes augmented contractility and accelerated Ca²⁺ decay. Transgene-mediated SUMO1 overexpression rescued pressure overload-induced cardiac dysfunction concomitantly with increased SERCA2a function. By contrast, down-regulation of SUMO1 using shRNA accelerated pressure overload-induced deterioration of cardiac function and was accompanied by decreased SERCA2a function. However, knockdown of SERCA2a resulted in severe contractile dysfunction both in vitro and in vivo, which was not rescued by overexpression of SUMO1. Taken together, our data show that SUMOylation is a critical post-translational modification that regulates SERCA2a function and provides a platform for the design of novel therapeutic strategies for HF.

Hydralazine-induced promoter demethylation enhances sarcoplasmic reticulum Ca2+ -ATPase and calcium homeostasis in cardiac myocytes

Sarcoplasmic reticulum (SR) Ca(2+)-ATPase (SERCA2a) plays an essential role in Ca(2+) homeostasis and cardiac functions. The promoter region of SERCA2a has a high content of CpG islands; thus, epigenetic modification by inhibiting methylation can enhance SERCA2a expression in cardiomyocytes. Hydralazine, a drug frequently used in heart failure, is a potential DNA methylation inhibitor. We evaluated whether hydralazine can modulate Ca(2+) handling through an increase in SERCA2a expression via regulating methylation. We used indo-1 fluorescence, real-time RT-PCR, immunoblotting, and methylation-specific PCR to investigate intracellular Ca(2+), the expressions of RNA and protein, and methylation of SERCA2a in HL-1 cardiomyocytes with and without (control) the administration of hydralazine (1, 10, and 30 μM) for 72 h. Hydralazine (10 and 30 μM) increased the intracellular Ca(2+) transients and SR Ca(2+) contents. Hydralazine (10 and 30 μM) decreased methylation in the SERCA2a promoter region and increased the RNA and protein expressions of SERCA2a. Additionally, hydralazine (10 and 30 μM) decreased the expression of DNA methyltransferase 1. Moreover, treatment with hydralazine in isoproterenol-induced heart failure rats decreased the promoter methylation of SERCA2a and increased SERCA2a RNA expression. In conclusion, hydralazine-induced promoter demethylation may improve cardiac function through increasing SERCA2a and modulating calcium homeostasis in cardiomyocytes.

Gene therapy targets in heart failure: the path to translation

Heart failure (HF) is the common end point of cardiac diseases. Despite the optimization of therapeutic strategies and the consequent overall reduction in HF-related mortality, the key underlying intracellular signal transduction abnormalities have not been addressed directly. In this regard, the gaps in modern HF therapy include derangement of β-adrenergic receptor (β-AR) signaling, Ca(2+) disbalances, cardiac myocyte death, diastolic dysfunction, and monogenetic cardiomyopathies. In this review we discuss the potential of gene therapy to fill these gaps and rectify abnormalities in intracellular signaling. We also examine current vector technology and currently available vector-delivery strategies, and we delineate promising gene therapy structures. Finally, we analyze potential limitations related to the transfer of successful preclinical gene therapy approaches to HF treatment in the clinic, as well as impending strategies aimed at overcoming these limitations.

SERCA2a gene transfer improves electrocardiographic performance in aged mdx mice

Background

Cardiomyocyte calcium overloading has been implicated in the pathogenesis of Duchenne muscular dystrophy (DMD) heart disease. The cardiac isoform of sarcoplasmic reticulum calcium ATPase (SERCA2a) plays a major role in removing cytosolic calcium during heart muscle relaxation. Here, we tested the hypothesis that SERCA2a over-expression may mitigate electrocardiography (ECG) abnormalities in old female mdx mice, a murine model of DMD cardiomyopathy.

Methods

1 × 10¹² viral genome particles/mouse of adeno-associated virus serotype-9 (AAV-9) SERCA2a vector was delivered to 12-m-old female mdx mice (N = 5) via a single bolus tail vein injection. AAV transduction and the ECG profile were examined eight months later.

Results

The vector genome was detected in the hearts of all AAV-injected mdx mice. Immunofluorescence staining and western blot confirmed SERCA2a over-expression in the mdx heart. Untreated mdx mice showed characteristic tachycardia, PR interval reduction and QT interval prolongation. AAV-9 SERCA2a treatment corrected these ECG abnormalities.

Conclusions

Our results suggest that AAV SERCA2a therapy may hold great promise in treating dystrophin-deficient heart disease.

Calcium cycling proteins and their association with heart failure

Heart failure (HF) has reached epidemic proportions in the United States and is one of the most important challenges to public health. Severe congestive HF is associated with substantial morbidity and mortality. HF afflicts approximately 5 million patients and contributes to 3 million hospitalizations and 300,000 deaths yearly. Late-stage HF has a poor prognosis, and therapeutic options are limited. Defective excitation–contraction (EC) coupling in HF may result from altered density or function of proteins relevant for Ca2+ homeostasis.

Cardiac gene transfer of short hairpin RNA directed against phospholamban effectively knocks down gene expression but causes cellular toxicity in canines

Derangements in calcium cycling have been described in failing hearts, and preclinical studies have suggested that therapies aimed at correcting this defect can lead to improvements in cardiac function and survival. One strategy to improve calcium cycling would be to inhibit phospholamban (PLB), the negative regulator of SERCA2a that is upregulated in failing hearts. The goal of this study was to evaluate the safety and efficacy of using adeno-associated virus (AAV)-mediated cardiac gene transfer of short hairpin RNA (shRNA) to knock down expression of PLB. Six dogs were treated with self-complementary AAV serotype 6 (scAAV6) expressing shRNA against PLB. Three control dogs were treated with empty AAV6 capsid, and two control dogs were treated with scAAV6 expressing dominant negative PLB. Vector was delivered via a percutaneously inserted cardiac injection catheter. PLB mRNA and protein expression were analyzed in three of six shRNA dogs between days 16 and 26. The other three shRNA dogs and five control dogs were monitored long-term to assess cardiac safety. PLB mRNA was reduced 16-fold, and PLB protein was reduced 5-fold, with treatment. Serum troponin elevation and depressed cardiac function were observed in the shRNA group only at 4 weeks. An enzyme-linked immunospot assay failed to detect any T cells reactive to AAV6 capsid in peripheral blood mononuclear cells, heart, or spleen. Microarray analysis revealed alterations in cardiac expression of several microRNAs with shRNA treatment. AAV6-mediated cardiac gene transfer of shRNA effectively knocks down PLB expression but is associated with severe cardiac toxicity. Toxicity may result from dysregulation of endogenous microRNA pathways.

AAV vectors for cardiac gene transfer: experimental tools and clinical opportunities

Since the first demonstration of in vivo gene transfer into myocardium there have been a series of advancements that have driven the evolution of cardiac gene delivery from an experimental tool into a therapy currently at the threshold of becoming a viable clinical option. Innovative methods have been established to address practical challenges related to tissue-type specificity, choice of delivery vehicle, potency of the delivered material, and delivery route. Most importantly for therapeutic purposes, these strategies are being thoroughly tested to ensure safety of the delivery system and the delivered genetic material. This review focuses on the development of recombinant adeno-associated virus (rAAV) as one of the most valuable cardiac gene transfer agents available today. Various forms of rAAV have been used to deliver "pre-event" cardiac protection and to temper the severity of hypertrophy, cardiac ischemia, or infarct size. Adeno-associated virus (AAV) vectors have also been functional delivery tools for cardiac gene expression knockdown studies and successfully improving the cardiac aspects of several metabolic and neuromuscular diseases. Viral capsid manipulations along with the development of tissue-specific and regulated promoters have greatly increased the utility of rAAV-mediated gene transfer. Important clinical studies are currently underway to evaluate AAV-based cardiac gene delivery in humans.

Calcium Upregulation by Percutaneous Administration of Gene Therapy in Cardiac Disease (CUPID): a phase 2 trial of intracoronary gene therapy of sarcoplasmic reticulum Ca2+-ATPase in patients with advanced heart failure

BACKGROUND

Adeno-associated virus type 1/sarcoplasmic reticulum Ca(2+)-ATPase was assessed in a randomized, double-blind, placebo-controlled, phase 2 study in patients with advanced heart failure.

METHODS AND RESULTS

Thirty-nine patients received intracoronary adeno-associated virus type 1/sarcoplasmic reticulum Ca(2+)-ATPase or placebo. Seven efficacy parameters were assessed in 4 domains: symptoms (New York Heart Association class, Minnesota Living With Heart Failure Questionnaire), functional status (6-minute walk test, peak maximum oxygen consumption), biomarker (N-terminal prohormone brain natriuretic peptide), and left ventricular function/remodeling (left ventricular ejection fraction, left ventricular end-systolic volume), plus clinical outcomes. The primary end point success criteria were prospectively defined as achieving efficacy at 6 months in the group-level (concordant improvement in 7 efficacy parameters and no clinically significant worsening in any parameter), individual-level (total score for predefined clinically meaningful changes in 7 efficacy parameters), or outcome end points (cardiovascular hospitalizations and time to terminal events). Efficacy in 1 analysis had to be associated with at least a positive trend in the other 2 analyses. This combination of requirements resulted in a probability of success by chance alone of 2.7%. The high-dose group versus placebo met the prespecified criteria for success at the group-level, individual-level, and outcome analyses (cardiovascular hospitalizations) at 6 months (confirmed at 12 months) and demonstrated improvement or stabilization in New York Heart Association class, Minnesota Living With Heart Failure Questionnaire, 6-minute walk test, peak maximum oxygen consumption, N-terminal prohormone brain natriuretic peptide levels, and left ventricular end-systolic volume. Significant increases in time to clinical events and decreased frequency of cardiovascular events were observed at 12 months (hazard ratio=0.12; P=0.003), and mean duration of cardiovascular hospitalizations over 12 months was substantially decreased (0.4 versus 4.5 days; P=0.05) on high-dose treatment versus placebo. There were no untoward safety findings.

CONCLUSIONS

The Calcium Upregulation by Percutaneous Administration of Gene Therapy in Cardiac Disease (CUPID) study demonstrated safety and suggested benefit of adeno-associated virus type 1/sarcoplasmic reticulum Ca(2+)-ATPase in advanced heart failure, supporting larger confirmatory trials.

CLINICAL TRIAL REGISTRATION

http://www.clinicaltrials.gov. Unique identifier: NCT00454818.

Rescuing the failing heart by targeted gene transfer

Congestive heart failure is a major cause of morbidity and mortality in the United States. Although progress in conventional treatments is making steady and incremental gains to decrease heart failure mortality, there is a critical need to explore new therapeutic approaches. Gene therapy was initially applied in the clinical setting for inherited monogenic disorders. It is now apparent that gene therapy has broader potential that also includes acquired polygenic diseases, such as congestive heart failure. Recent advances in understanding of the molecular basis of myocardial dysfunction, together with the evolution of increasingly efficient gene transfer technology, have placed heart failure within the reach of gene-based therapy. Furthermore, the recent successful and safe completion of a phase 2 trial targeting the sarcoplasmic reticulum Ca(2+) ATPase pump along with the start of more recent phase 1 trials are ushering in a new era of gene therapy for the treatment of heart failure.

Ovine models for chronic heart failure

PURPOSE

Testing and optimizing of surgical therapies for chronic heart failure (CHF) requires large animal models. CHF has been induced in several large animal species. Sheep have modest body mass increase and demonstrate docile behavior and are therefore a preferred species in research on surgical therapies for CHF METHODS: A literature search for existing ovine CHF models was performed, using search terms "sheep" and "heart failure". Relevant secondary references were traced.

RESULTS

Rapid ventricular pacing produces rapid-onset CHFE Its severity ranges from moderate left ventricular failure to severe biventricular failure, depending on length and frequency of pacing. Its counterpart in human CHF is tachycardia-induced HF since it is reversible upon cessation of pacing. Myocardial damage models include CHF induced by cardiototoxic drugs and ischemia. Ischemia-based models include coronary microembolization, occlusion and ischemia/reperfusion models. The microembolization model is relevant to diabetic cardiomyopathy. Coronary occlusion models exhibit variable functional impairment, some with aneurysm formation, and some with mitral valve regurgitation, depending on occlusion localization. They are relevant to CHF following non-reperfused myocardial infarction. Coronary occlusion/reperfusion models are relevant to the occurrence of human ãã despite coronary artery recanalization. Pressure overload of left and right ventricle is induced by aortic and pulmonary artery banding, respectively. Hypertrophy precedes CHF as in patients with valve stenosis and hypertension. Volume overload is induced by valve damage or shunt creation. Atrioventricular valve regurgitation is the most important clinical counterpart.

CONCLUSION

Several ovine CHF models exist. Since they exhibit important cardiac pathology differences, the choice of model should be based on the specific experimental question.

Targeted gene therapy for the treatment of heart failure

Chronic heart failure is one of the leading causes of morbidity and mortality in Western countries and is a major financial burden to the health care system. Pharmacologic treatment and implanting devices are the predominant therapeutic approaches. They improve survival and have offered significant improvement in patient quality of life, but they fall short of producing an authentic remedy. Cardiac gene therapy, the introduction of genetic material to the heart, offers great promise in filling this void. In-depth knowledge of the underlying mechanisms of heart failure is, obviously, a prerequisite to achieve this aim. Extensive research in the past decades, supported by numerous methodological breakthroughs, such as transgenic animal model development, has led to a better understanding of the cardiovascular diseases and, inadvertently, to the identification of several candidate genes. Of the genes that can be targeted for gene transfer, calcium cycling proteins are prominent, as abnormalities in calcium handling are key determinants of heart failure. A major impediment, however, has been the development of a safe, yet efficient, delivery system. Nonviral vectors have been used extensively in clinical trials, but they fail to produce significant gene expression. Viral vectors, especially adenoviral, on the other hand, can produce high levels of expression, at the expense of safety. Adeno-associated viral vectors have emerged in recent years as promising myocardial gene delivery vehicles. They can sustain gene expression at a therapeutic level and maintain it over extended periods of time, even for years, and, most important, without a safety risk.

SERCA2a gene transfer decreases sarcoplasmic reticulum calcium leak and reduces ventricular arrhythmias in a model of chronic heart failure

BACKGROUND

Sarcoplasmic reticulum calcium ATPase 2a (SERCA2a) gene therapy improves mechanical function in heart failure and is under evaluation in a clinical trial. A critical question is whether SERCA2a gene therapy predisposes to increased sarcoplasmic reticulum calcium (SR Ca(2+)) leak, cellular triggered activity, and ventricular arrhythmias in the failing heart.

METHODS AND RESULTS

We studied the influence of SERCA2a gene therapy on ventricular arrhythmogenesis in a rat chronic heart failure model. ECG telemetry studies revealed a significant antiarrhythmic effect of SERCA2a gene therapy with reduction of both spontaneous and catecholamine-induced arrhythmias in vivo. SERCA2a gene therapy also reduced susceptibility to reentry arrhythmias in ex vivo programmed electrical stimulation studies. Subcellular Ca(2+) homeostasis and spontaneous SR Ca(2+) leak characteristics were measured in failing cardiomyocytes transfected in vivo with a novel AAV9.SERCA2a vector. SR Ca(2+) leak was reduced after SERCA2a gene therapy, with reversal of the greater spark mass observed in the failing myocytes, despite normalization of SR Ca(2+) load. SERCA2a reduced ryanodine receptor phosphorylation, thereby resetting SR Ca(2+) leak threshold, leading to reduced triggered activity in vitro. Both indirect effects of reverse remodeling and direct SERCA2a effects appear to underlie the antiarrhythmic action.

CONCLUSIONS

SERCA2a gene therapy stabilizes SR Ca(2+) load, reduces ryanodine receptor phosphorylation and decreases SR Ca(2+) leak, and reduces cellular triggered activity in vitro and spontaneous and catecholamine-induced ventricular arrhythmias in vivo in failing hearts. SERCA2a gene therapy did not therefore predispose to arrhythmias and may represent a novel antiarrhythmic strategy in heart failure.

What causes a broken heart--molecular insights into heart failure

Our understanding of the molecular processes which regulate cardiac function has grown immeasurably in recent years. Even with the advent of β-blockers, angiotensin inhibitors and calcium modulating agents, heart failure (HF) still remains a seriously debilitating and life-threatening condition. Here, we review the molecular changes which occur in the heart in response to increased load and the pathways which control cardiac hypertrophy, calcium homeostasis, and immune activation during HF. These can occur as a result of genetic mutation in the case of hypertrophic cardiomyopathy (HCM) and dilated cardiomyopathy (DCM) or as a result of ischemic or hypertensive heart disease. In the majority of cases, calcineurin and CaMK respond to dysregulated calcium signaling and adrenergic drive is increased, each of which has a role to play in controlling blood pressure, heart rate, and left ventricular function. Many major pathways for pathological remodeling converge on a set of transcriptional regulators such as myocyte enhancer factor 2 (MEF2), nuclear factors of activated T cells (NFAT), and GATA4 and these are opposed by the action of the natriuretic peptides ANP and BNP. Epigenetic modification has emerged in recent years as a major influence cardiac physiology and histone acetyl transferases (HATs) and histone deacetylases (HDACs) are now known to both induce and antagonize hypertrophic growth. The newly emerging roles of microRNAs in regulating left ventricular dysfunction and fibrosis also has great potential for novel therapeutic intervention. Finally, we discuss the role of the immune system in mediating left ventricular dysfunction and fibrosis and ways this can be targeted in the setting of viral myocarditis.

Adeno-associated virus vector delivery to the heart

Cardiac gene transfer may serve as a novel therapeutic approach in the treatment of heart disease. For it to reach its full potential, methods for highly efficient cardiac gene transfer must be available to investigators so that informative preclinical data can be collected and evaluated. We have recently optimized AAV-mediated cardiac gene transfer protocols in both the mouse and rat. In the mouse, we have developed a procedure for intrapericardial delivery of vector in the neonate and successfully applied intravenous injections in adult animals. In the rat, we have developed a procedure for direct injection of vector into the myocardium in adults and established a protocol for vector delivery into the left ventricular anterior wall by ultrasound-targeted destruction of microbubbles loaded with AAV. Each protocol can be used to achieve safe and efficient cardiac gene transfer in the model of choice.

Cardiac gene therapy with SERCA2a: from bench to bedside

While progress in conventional treatments is making steady and incremental gains to reduce mortality associated with heart failure, there remains a need to explore potentially new therapeutic approaches. Heart failure induced by different etiologies such as coronary artery disease, hypertension, diabetes, infection, or inflammation results generally in calcium cycling dysregulation at the myocyte level. Recent advances in understanding of the molecular basis of these calcium cycling abnormalities, together with the evolution of increasingly efficient gene transfer technology, have placed heart failure within reach of gene-based therapy. Furthermore, the recent successful completion of a phase 2 trial targeting the sarcoplasmic reticulum calcium pump (SERCA2a) ushers in a new era for gene therapy for the treatment of heart failure. This article is part of a Special Section entitled "Special Section: Cardiovascular Gene Therapy".

Perivascular fluid cuffs decrease lung compliance by increasing tissue resistance

OBJECTIVE

Lung inflammation causes perivascular fluid cuffs to form around extra-alveolar blood vessels; however, the physiologic consequences of such cuffs remain poorly understood. Herein, we tested the hypothesis that perivascular fluid cuffs, without concomitant alveolar edema, are sufficient to decrease lung compliance.

DESIGN

Prospective, randomized, controlled study.

SETTING

Research laboratory.

SUBJECTS

One hundred twenty male CD40 rats.

INTERVENTIONS

To test this hypothesis, the plant alkaloid thapsigargin was used to activate store-operated calcium entry and increase cytosolic calcium in endothelium. Thapsigargin was infused into a central venous catheter of intact, sedated, and mechanically ventilated rats.

MEASUREMENTS

Static and dynamic lung mechanics and hemodynamics were measured continuously.

MAIN RESULTS

Thapsigargin produced perivascular fluid cuffs along extra-alveolar vessels but did not cause alveolar flooding or blood gas abnormalities. Lung compliance dose-dependently decreased after thapsigargin infusion, attributable to an increase in tissue resistance that was attributed to increased tissue damping and tissue elastance. Airway resistance was not changed. Neither central venous pressure nor left ventricular end diastolic pressure was altered by thapsigargin. Heart rate did not change, although thapsigargin decreased left ventricular systolic function sufficient to reduce cardiac output by 50%. Infusion of the type 4 phosphodiesterase inhibitor, rolipram, prevented thapsigargin from inducing perivascular cuffs and decreasing lung compliance. Rolipram also normalized pressure over time and corrected the deficit in cardiac output.

CONCLUSIONS

Our findings resolve for the first time that perivascular cuff formation negatively impacts mechanical coupling between the bronchovascular bundle and the lung parenchyma, decreasing lung compliance without impacting central venous pressure.

Gene delivery of sarcoplasmic reticulum calcium ATPase inhibits ventricular remodeling in ischemic mitral regurgitation

BACKGROUND

Mitral regurgitation (MR) doubles mortality after myocardial infarction (MI). We have demonstrated that MR worsens remodeling after MI and that early correction reverses remodeling. Sarcoplasmic reticulum Ca(+2)-ATPase (SERCA2a) is downregulated in this process. We hypothesized that upregulating SERCA2a might inhibit remodeling in a surgical model of apical MI (no intrinsic MR) with independent MR-type flow.

METHODS AND RESULTS

In 12 sheep, percutaneous gene delivery was performed by using a validated protocol to perfuse both the left anterior descending and circumflex coronary arteries with occlusion of venous drainage. We administered adeno-associated virus 6 (AAV6) carrying SERCA2a under a Cytomegalovirus promoter control in 6 sheep and a reporter gene in 6 controls. After 2 weeks, a standardized apical MI was created, and a shunt was implanted between the left ventricle and left atrium, producing regurgitant fractions of ≈30%. Animals were compared at baseline and 1 and 3 months by 3D echocardiography, Millar hemodynamics, and biopsies. The SERCA2a group had a well-maintained preload-recruitable stroke work at 3 months (decrease by 8±10% vs 42±12% with reporter gene controls; P<0.001). Left ventricular dP/dt followed the same pattern (no change vs 55% decrease; P<0.001). Left ventricular end-systolic volume was lower with SERCA2a (82.6±9.6 vs 99.4±9.7 mL; P=0.03); left ventricular end-diastolic volume, reflecting volume overload, was not significantly different (127.8±6.2 vs 134.3±9.4 mL). SERCA2a sheep showed a 15% rise in antiapoptotic pAkt versus a 30% reduction with the reporter gene (P<0.001). Prohypertrophic activated STAT3 was also 41% higher with SERCA2a than in controls (P<0.001). Proapoptotic activated caspase-3 rose >5-fold during 1 month in both SERCA2a and control animals (P=NS) and decreased by 19% at 3 months, remaining elevated in both groups.

CONCLUSIONS

In this controlled model, upregulating SERCA2a induced better function and lesser remodeling, with improved contractility, smaller volume, and activation of prohypertrophic/antiapoptotic pathways. Although caspase-3 remained activated in both groups, SERCA2a sheep had increased molecular antiremodeling "tone." We therefore conclude that upregulating SERCA2a inhibits MR-induced post-MI remodeling in this model and thus may constitute a useful approach to reduce the vicious circle of remodeling in ischemic MR.

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.

Refilling Intracellular Calcium Stores

Within the cardiac cell, the movements of calcium ions are tightly regulated by a number of regulatory proteins including pumps, and channels. The sarcoplasmic reticulum (SR) is in large part responsible for orchestrating these movements for the normal functioning of the cardiomyocyte. Alterations of SR regulatory proteins in failing hearts leads to abnormal Ca(2+) homeostasis and consequently to a deficient contractile state. This review focuses on the roles of SR Ca(2+) regulators in disease states and novel strategies for therapeutic targeting of these pathways.

Parathyroid hormone accelerates decompensation following left ventricular hypertrophy

Parathyroid hormone (PTH) treatment was previously shown to improve cardiac function after myocardial infarction by enhancing neovascularization and cell survival. In this study, pressure overload-induced left ventricular hypertrophy (LVH) was induced in mice by transverse aortic banding (TAB) for 2 weeks. We subsequently evaluated the effects of a 2-week treatment with PTH or saline on compensated LVH. After another 4 weeks, the hearts of the mice were analyzed by echocardiography, histology, and molecular biology. Echocardiography showed that hearts of the PTH-treated mice have more severe failing phenotypes than the saline-treated mice following TAB with a greater reduction in fractional shortening and left ventricular posterior wall thickness and with a greater increase in left ventricular internal dimension. Increases in the heart weight to body weight ratio and lung weight to body weight ratio following TAB were significantly exacerbated in PTH-treated mice compared to saline-treated mice. Molecular markers for heart failure, fibrosis, and angiogenesis were also altered in accordance with more severe heart failure in the PTH-treated mice compared to the saline-treated mice following TAB. In addition, the PTH-treated hearts were manifested with increased fibrosis accompanied by an enhanced SMAD2 phosphorylation. These data suggest that the PTH treatment may accelerate the process of decompensation of LV, leading to heart failure.

SERCA2a gene transfer enhances eNOS expression and activity in endothelial cells

Congestive heart failure (HF) is associated with impaired endothelium-dependent nitric oxide-mediated vasodilatation. The aim of this study was to examine the effects of sarco/endoplasmic reticulum (ER) Ca(2+)-ATPase 2a (SERCA2a) gene transfer on endothelial function in a swine HF model. Two months after the creation of mitral regurgitation to induce HF, the animals underwent intracoronary injection of adeno-associated virus (AAV) carrying SERCA2a (n = 7) or saline (n = 6). At 4 months, coronary flow (CF) was measured in the mid-portion of the left anterior descending (LAD) artery. In the failing animals, CF was decreased significantly; SERCA2a gene transfer rescued CF to levels observed in sham-group [ml/min/g, 0.47 +/- 0.064 saline versus 0.89 +/- 0.116, SERCA2a; P < 0.05; 1.00 +/- 0. 185 sham P = NS (nonsignificant)]. In coronary arteries from HF animals, SERCA2a and endothelial isoform of nitric oxide synthase (eNOS) protein expression were decreased, but restored to normal levels by SERCA2a gene transfer. In human coronary artery endothelial cells (HCAECs), SERCA2a overexpression increased eNOS expression, phosphorylation, eNOS promoter activity, Ca(2+) storage capacity, and enhanced histamine-induced calcium oscillations, eNOS activity, and cyclic guanosine monophosphate (cGMP) production. Thus, SERCA2a gene transfer increases eNOS expression and activity by modulating calcium homeostasis to improve CF. These findings suggest that SERCA2a gene transfer improves vascular reactivity in the setting of HF.

Myocardial gene expression alterations in peripheral blood mononuclear cells of patients with idiopathic dilated cardiomyopathy

AIMS

To assess cardiac gene expression in peripheral blood cells of patients with idiopathic dilated cardiomyopathy (IDCM) and its relationship to echocardiographic left ventricular (LV) function.

METHODS AND RESULTS

A complete echocardiographic study and blood sampling were performed in 65 consecutive stable IDCM patients with LV ejection fraction (LVEF) 31.76 +/- 10.07% and chronic mild to moderate heart failure (NYHA functional class II to III) for > or =9 months. Blood samples from 19 healthy individuals were included for comparison. Transcript levels of myocardin, GATA4, alpha- and beta-myosin heavy chain (MHC), sarcoplasmic reticulum calcium ATPase 2 (SERCA2), and phospholamban were determined by quantitative real-time reverse transcription-polymerase chain reaction. Myocardin (24.88 +/- 4.93 vs. 3.98 +/- 1.12, P = 0.0048) and GATA4 (17.85 +/- 4.85 vs. 0.45 +/- 0.15, P = 0.0069 x 10(-5)) were upregulated in IDCM patients compared with controls, whereas SERCA2 (5.11 +/- 0.42 vs. 8.93 +/- 1.07, P = 0.001) was downregulated. In IDCM patients, myocardin (r = 0.279, P = 0.025), GATA4 (r = 0.314, P = 0.011), beta-MHC (r = 0.444, P=0.0002), and alpha-MHC (r = 0.272, P = 0.034) showed positive correlations, whereas SERCA2 (r = -0.264, P = 0.034) exhibited a negative correlation with LVEF. Patients with elevated LV filling pressures had lower myocardin (15.06 +/- 3.10 vs. 43.12 +/- 12.03, P = 0.048), GATA4 (8.96 +/- 2.17 vs. 34.38 +/- 12.60, P = 0.026), beta-MHC (10.59 +/- 4.05 vs. 16.43 +/- 4.91, P = 0.013), and alpha-MHC (0.27 +/- 0.08 vs. 0.79 +/- 0.20, P = 0.033) and higher SERCA2 (5.65 +/- 0.54 vs. 3.90 +/- 0.61, P = 0.037) levels. Patients with atrial fibrillation (AF) had higher SERCA2 levels compared with sinus rhythm patients (6.75 +/- 0.84 vs. 4.54 +/- 0.45, P = 0.017).

CONCLUSION

Our data indicate that cardiac gene expression alterations in peripheral blood cells of IDCM patients may reflect alterations in LV function, whereas the presence of AF may be associated with increased SERCA2 levels in these patients.

Ion channels, transporters, and pumps as targets for heart failure therapy

Congestive heart failure is a leading cause of morbidity and mortality. Congestive heart failure is marked by atrial and ventricular enlargements and reduced cardiac contractility and an association with an increased incidence of atrial and ventricular arrhythmias and sudden cardiac death. Dysfunctional ion channel function is one of the major underlying mechanisms of the reduced contractility and arrhythmias. In this review, we explore the utility of ion channels, transporters, and pumps as targets for the treatment of heart failure, focusing predominantly on the treatment for reduced contractility and arrhythmias.

Mitral valve surgery in advanced heart failure

The appropriateness and timing of mitral valve surgery in patients with advanced heart failure and severe mitral regurgitation remains controversial. Recent surgical results provide evidence for beneficial effects on left ventricular remodeling and functional capacity. Given the absence of randomized trials comparing the outcomes of mitral valve surgery to medical therapy, however, clinical decision making regarding surgery for these fragile patients poses a dilemma to thoughtful clinicians. This paper reviews the pathophysiology of mitral regurgitation in heart failure and proposes an integrated approach to management.

Alpha1A-adrenergic receptor-directed autoimmunity induces left ventricular damage and diastolic dysfunction in rats

BACKGROUND

Agonistic autoantibodies to the alpha(1)-adrenergic receptor occur in nearly half of patients with refractory hypertension; however, their relevance is uncertain.

METHODS/PRINCIPAL FINDINGS

We immunized Lewis rats with the second extracellular-loop peptides of the human alpha(1A)-adrenergic receptor and maintained them for one year. Alpha(1A)-adrenergic antibodies (alpha(1A)-AR-AB) were monitored with a neonatal cardiomyocyte contraction assay by ELISA, and by ERK1/2 phosphorylation in human alpha(1A)-adrenergic receptor transfected Chinese hamster ovary cells. The rats were followed with radiotelemetric blood pressure measurements and echocardiography. At 12 months, the left ventricles of immunized rats had greater wall thickness than control rats. The fractional shortening and dp/dt(max) demonstrated preserved systolic function. A decreased E/A ratio in immunized rats indicated a diastolic dysfunction. Invasive hemodynamics revealed increased left ventricular end-diastolic pressures and decreased dp/dt(min). Mean diameter of cardiomyocytes showed hypertrophy in immunized rats. Long-term blood pressure values and heart rates were not different. Genes encoding sarcomeric proteins, collagens, extracellular matrix proteins, calcium regulating proteins, and proteins of energy metabolism in immunized rat hearts were upregulated, compared to controls. Furthermore, fibrosis was present in immunized hearts, but not in control hearts. A subset of immunized and control rats was infused with angiotensin (Ang) II. The stressor raised blood pressure to a greater degree and led to more cardiac fibrosis in immunized, than in control rats.

CONCLUSIONS/SIGNIFICANCE

We show that alpha(1A)-AR-AB cause diastolic dysfunction independent of hypertension, and can increase the sensitivity to Ang II. We suggest that alpha(1A)-AR-AB could contribute to cardiovascular endorgan damage.

Sarcoplasmic reticulum Ca(2+) ATPase as a therapeutic target for heart failure

The cardiac isoform of the sarco/endoplasmic reticulum Ca(2+)ATPase (SERCA2a) plays a major role in controlling excitation/contraction coupling. In both experimental and clinical heart failure, SERCA2a expression is significantly reduced which leads to abnormal Ca(2+) handling and deficient contractility. A large number of studies in isolated cardiac myocytes and in small and large animal models of heart failure showed that restoring SERCA2a expression by gene transfer corrects the contractile abnormalities and improves energetics and electrical remodeling. Following a long line of investigation, a clinical trial is underway to restore SERCA2a expression in patients with heart failure using adeno-associated virus type 1. This review addresses the following issues regarding heart failure gene therapy: i) new insights on calcium regulation by SERCA2a; ii) SERCA2a as a gene therapy target in animal models of heart failure; iii) advances in the development of viral vectors and gene delivery; and iv) clinical trials on heart failure using SERCA2a. This review focuses on the new advances in SERCA2a- targeted gene therapy made in the last three years. In conclusion, SERCA2a is an important therapeutic target in various cardiovascular disorders. Ongoing clinical gene therapy trials will provide answers on its safety and applicability.

Phospholamban ablation rescues sarcoplasmic reticulum Ca(2+) handling but exacerbates cardiac dysfunction in CaMKIIdelta(C) transgenic mice

RATIONALE

We previously showed that transgenic mice expressing Ca(2+)/calmodulin-dependent protein kinase II delta(C) (CaMKII-TG) develop dilated cardiomyopathy associated with increased ryanodine receptors (RyR2) phosphorylation, enhanced sarcoplasmic reticulum (SR) Ca(2+) leak and lowering of SR Ca(2+) load. We hypothesized that phospholamban (PLN) ablation would restore SR Ca(2+) load and prevent the decreased ventricular contractility, dilation and mortality seen in CaMKII-TG.

OBJECTIVE

Our objectives were to generate CaMKII-TG mice lacking PLN, determine whether the maladaptive effects of cardiac CaMKIIdelta(C) expression were corrected, and establish the mechanistic basis for these changes.

METHODS AND RESULTS

CaMKII-TG were crossed with PLN knockout (PLN-KO) mice to generate KO/TG mice. Myocytes from wild type (WT), CaMKII-TG, PLN-KO and KO/TG were compared. The decreased SR Ca(2+) load and twitch Ca(2+) transients seen in CaMKII-TG were normalized in KO/TG. Surprisingly the heart failure phenotype was exacerbated, as indicated by increased left ventricular dilation, decreased ventricular function, increased apoptosis and greater mortality. In KO/TG myocytes SR Ca(2+) sparks and leak were significantly increased, presumably because of the combined effects of restored SR Ca(2+) load and RyR2 phosphorylation. Mitochondrial Ca(2+) loading was increased in cardiomyocytes from KO/TG versus WT or CaMKII-TG mice and this was dependent on elevated SR Ca(2+) sparks. Cardiomyocytes from KO/TG showed poor viability, improved by inhibiting SR Ca(2+) release and mitochondrial Ca(2+) loading.

CONCLUSIONS

Normalizing cardiomyocyte SR Ca(2+) loading in the face of elevated CaMKII and RyR2 phosphorylation leads to enhanced SR Ca(2+) leak and mitochondrial Ca(2+) elevation, associated with exacerbated cell death, heart failure and mortality.

Large animal models of heart failure: a critical link in the translation of basic science to clinical practice

Congestive heart failure (HF) is a clinical syndrome, with hallmarks of fatigue and dyspnea, that continues to be highly prevalent and morbid. Because of the growing burden of HF as the population ages, the need to develop new pharmacological treatments and therapeutic interventions is of paramount importance. Common pathophysiologic features of HF include changes in left ventricle structure, function, and neurohormonal activation. The recapitulation of the HF phenotype in large animal models can allow for the translation of basic science discoveries into clinical therapies. Models of myocardial infarction/ischemia, ischemic cardiomyopathy, ventricular pressure and volume overload, and pacing-induced dilated cardiomyopathy have been created in dogs, pigs, and sheep for the investigation of HF and potential therapies. Large animal models recapitulating the clinical HF phenotype and translating basic science to clinical applications have successfully traveled the journey from bench to bedside. Undoubtedly, large animal models of HF will continue to play a crucial role in the elucidation of biological pathways involved in HF and the development and refinement of HF therapies.

Modification of cardiovascular ion channels by gene therapy

Delivery of genes to the heart and vasculature for therapeutic purposes is an exciting strategy that is approaching clinical reality. Abnormalities of expression or function of ion channels is central to many cardiovascular diseases and gene delivery to modify ion channels is an appealing alternative to traditional therapy with small-molecule drugs. Potential therapeutic targets include hypertrophy and heart failure, atrioventricular node modification in atrial fibrillation, ventricular tachycardia and hypertension. Numerous approaches for gene delivery are under development, including use of tissue-specific promoters in viral vectors. For other applications, such as development of biological pacemakers, cells can be transduced with pacemaker genes in vitro, and then the cells implanted within the heart. There are short-term hurdles to therapeutic gene delivery to modify cardiovascular ion channels, but in the intermediate and longer term, the outlook is promising.

Gene and cell therapy for heart failure

Cardiac gene and cell therapy have both entered clinical trials aimed at ameliorating ventricular dysfunction in patients with chronic congestive heart failure. The transduction of myocardial cells with viral constructs encoding a specific cardiomyocyte Ca(2+) pump in the sarcoplasmic reticulum (SR), SRCa(2+)-ATPase has been shown to correct deficient Ca(2+) handling in cardiomyocytes and improvements in contractility in preclinical studies, thus leading to the first clinical trial of gene therapy for heart failure. In cell therapy, it is not clear whether beneficial effects are cell-type specific and how improvements in contractility are brought about. Despite these uncertainties, a number of clinical trials are under way, supported by safety and efficacy data from trials of cell therapy in the setting of myocardial infarction. Safety concerns for gene therapy center on inflammatory and immune responses triggered by viral constructs, and for cell therapy with myoblast cells, the major concern is increased incidence of ventricular arrhythmia after cell transplantation. Principles and mechanisms of action of gene and cell therapy for heart failure are discussed, together with the potential influence of reactive oxygen species on the efficacy of these treatments and the status of myocardial-delivery techniques for viral constructs and cells.

Heart failure management: the present and the future

Clinical heart failure has been defined for a long time as a clinical syndrome with symptoms and signs including shortness of breath, cyanosis, ascites, and edema. However, in recent years, with the thought of promoting early diagnosis and heart-failure prevention, the concept of heart failure has often been defined simply as a subject with severe LV dysfunction and a dilated left ventricle, or by some, defined by evidence of increased circulating levels of molecular markers of cardiac dysfunction, such as ANP and BNP. Heart failure has been considered an irreversible clinical end point. Current medical management for heart failure only relieves symptoms, slows deterioration, and prolongs life modestly. However, in the recent years, rejuvenation of the failing myocardium began to seem possible as the accumulating preclinical studies demonstrated that rejuvenating the myocardium at the molecular and cellular level can be achieved by gene therapy or stem cell transplantation. Here, we review selected novel modalities that have been shown in preclinical studies to exert beneficial effects in animal models of severe LV dysfunction and seem to have the potential to make an impact in the clinical practice of heart-failure management.

Calcium upregulation by percutaneous administration of gene therapy in cardiac disease (CUPID Trial), a first-in-human phase 1/2 clinical trial

BACKGROUND

SERCA2a deficiency is commonly seen in advanced heart failure (HF). This study is designed to investigate safety and biological effects of enzyme replacement using gene transfer in patients with advanced HF.

METHODS AND RESULTS

A total of 9 patients with advanced HF (New York Heart Association [NYHA] Class III/IV, ejection fraction [EF] < or = 30%, maximal oxygen uptake [VO2 max] <16 mL.kg.min, with maximal pharmacological and device therapy) received a single intracoronary infusion of AAV1/SERCA2a in the open-label portion of this ongoing study. Doses administered ranged from 1.4 x 10(11) to 3 x 10(12) DNase resistant particles per patient. We present 6- to 12-month follow-up data for these patients. AAV1/SERCA2a demonstrated an acceptable safety profile in this advanced HF population. Of the 9 patients treated, several demonstrated improvements from baseline to month 6 across a number of parameters important in HF, including symptomatic (NYHA and Minnesota Living with Heart Failure Questionnaire, 5 patients), functional (6-minute walk test and VO2 max, 4 patients), biomarker (NT-ProBNP, 2 patients), and LV function/remodeling (EF and end-systolic volume, 5 patients). Of note, 2 patients who failed to improve had preexisting anti-AAV1 neutralizing antibodies.

CONCLUSIONS

Quantitative evidence of biological activity across a number of parameters important for assessing HF status could be detected in several patients without preexisting neutralizing antibodies in this open-label study, although the number of patients in each cohort is too small to conduct statistical analyses. These findings support the initiation of the Phase 2 double-blind, placebo-controlled portion of this study.

Ca2+: is there something new for the cardiovascular anesthesiologist?

PURPOSE OF REVIEW

Anesthesiologists are frequently called upon to treat abnormalities of heart rhythm or pumping ability. Intracellular Ca is crucial for normal excitation-contraction coupling in the heart and plays a major role in the sequence of events that starts with an electrical signal generated in the atria and ends with myocardial contraction.

RECENT FINDINGS

From controlled diffusion within the cell to a potential role as a biological clock, intracellular Ca is receiving a great deal of attention. For example, the pacemaking electrical signal is known to originate in the sinoatrial node myocyte, but exactly what role Ca plays is controversial despite the fact that the sinoatrial node was discovered over 100 years ago. Basic mechanisms involved in disease processes such as atrial fibrillation and new interventions for heart rate control are beginning to emerge. New discoveries in ventricular myocytes are also stimulating the development of promising therapeutic interventions to safely increase the pumping ability of the heart.

SUMMARY

As our understanding of cardiac physiology and pharmacology progresses at the subcellular and molecular levels, new therapies will continue to emerge and the practice of anesthesia will benefit greatly.

The protective effects of exercise and phosphoinositide 3-kinase (p110α) in the failing heart

Despite the development of a wide range of therapies, heart failure remains a leading cause of death in Western society. New therapies are needed to help combat this debilitating condition. Exercise is becoming an increasingly important feature of rehabilitation programmes for patients with heart failure. Before the 1980s, patients with heart failure were advised not to exercise as it was thought that exercise would increase the risk of a cardiac event (such as myocardial infarction). However, in recent years both aerobic and resistance training have been shown to be safe and beneficial for patients with heart failure, improving exercise tolerance and quality of life, and preventing muscular deconditioning. The molecular mechanisms responsible for exercise-induced cardioprotection are yet to be elucidated, however studies in transgenic mice have identified PI3K(p110α) (phosphoinositide 3-kinase p110α) as a likely mediator. PI3K(p110α) is a lipid kinase which is activated in the heart during chronic exercise training, and is important for maintaining heart structure and function in various pathological settings. In the present review the protective effects of PI3K(p110α) in the failing heart and its potential as a therapeutic strategy for the treatment of heart failure is discussed.