Current gene therapy trials for vascular diseases

Therapeutic angiogenesis in coronary artery disease: a review of mechanisms and current approaches

INTRODUCTION

Despite tremendous advances, the shortcomings of current therapies for coronary disease are evidenced by the fact that it remains the leading cause of death in many parts of the world. There is hence a drive to develop novel therapies to tackle this disease. Therapeutic approaches to coronary angiogenesis have long been an area of interest in lieu of its incredible, albeit unrealized potential.

AREAS COVERED

This paper offers an overview of mechanisms of native angiogenesis and a description of angiogenic growth factors. It progresses to outline the advances in gene and stem cell therapy and provides a brief description of other investigational approaches to promote angiogenesis. Finally, the hurdles and limitations unique to this particular area of study are discussed.

EXPERT OPINION

An effective, sustained, and safe therapeutic option for angiogenesis truly could be the paradigm shift for cardiovascular medicine. Unfortunately, clinically meaningful therapeutic options remain elusive because promising animal studies have not been replicated in human trials. The sheer complexity of this process means that numerous major hurdles remain before therapeutic angiogenesis truly makes its way from the bench to the bedside.

Molecular mechanism of diabetic cardiomyopathy and modulation of microRNA function by synthetic oligonucleotides

Diabetic cardiomyopathy (DCM) is a chronic complication in individuals with diabetes and is characterized by ventricular dilation and hypertrophy, diastolic dysfunction, decreased or preserved systolic function and reduced ejection fraction eventually resulting in heart failure. Despite being well characterized, the fundamental mechanisms leading to DCM are still elusive. Recent studies identified the involvement of small non-coding small RNA molecules such as microRNAs (miRs) playing a key role in the etiology of DCM. Therefore, miRs associated with DCM represents a new class of targets for the development of mechanistic therapeutics, which may yield marked benefits compared to other therapeutic approaches. Indeed, few miRs currently under active clinical investigation, with many expressing cautious optimism that miRs based therapies will succeed in the coming years. The major caution in using miRs based therapy is the need to improve the stability and specificity following systemic injection, which can be achieved through chemical and structural modification. In this review, we first discuss the established role of miRs in DCM and the advances in miRs based therapeutic strategies for the prevention/treatment of DCM. We next discuss the currently employed chemical modification of miR oligonucleotides and their utility in therapies specifically focusing on the DCM. Finally, we summarize the commonly used delivery system and approaches for assessment of miRNA modulation and potential off-target effects.

Angiogenic gene therapy in cardiovascular diseases: dream or vision?

Chronic cardiovascular diseases are significant health problems. Although current treatment strategies have tremendously improved disease management, up to 30% of these patients cannot be successfully treated with current treatment approaches and new treatment strategies are clearly needed. Gene therapy and therapeutic vascular growth may provide a new treatment option for these patients. Several growth factors, like vascular endothelial growth factors, fibroblast growth factors and hepatocyte growth factor have been tested in clinical trials. However, apart from demonstration of increased vascularity, very few results with clinical significance have been obtained. Problems with gene transfer efficiency, short duration of transgene expression, selection of endpoints, and suboptimal patients for gene therapy have been recognized. Ongoing gene therapy trials have included improvements in study protocols, vector delivery and endpoints, addressing the identified problems. Better, targeted delivery systems and new, more optimal growth factors have been taken to clinical testing. Recent advances in these areas will be discussed and the concept of angiogenic therapy as a sole treatment is re-evaluated. A combination with regenerative therapies or standard revascularization operations might be needed to improve tissue function and clinical benefits.

Cardiovascular Gene Therapy: Past, Present, and Future

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

Enhancing Adenoviral-Mediated Gene Transfer and Expression to Endometrial Cells

OBJECTIVE

Our aim was to screen a panel of modified adenoviral gene transfer vectors to identify those which can sustain high gene expression in human endometrial cells.

METHODS

Normal endometrial stromal cell cultures were established from endometrial lining of hysterectomy specimens performed for benign gynecologic indications. Human endometrial stromal cells were transfected by modified adenoviruses expressing luciferase reporter gene. Luciferase activity mediated by each virus was expressed as a percentage of adenovirus serotype 5 (Ad5-CMV-luc) activity. The 2-tailed Student t test was used to compare data.

RESULTS

At a multiplicity of infection (MOI) of 10 pfu/cell, of the transductionally modified adenoviruses, adenovirus-RGD (Ad-RGD-luc) mediated highest level of endometrial cell transduction with transgene expression around 4 times higher when compared to Ad5 (P < .001). Of the transcriptionally targeted adenoviruses, adenovirus under secretory leukocyte protease inhibitor promoter (Ad-SLPI-luc) and adenovirus under heparanase promoter (Ad-heparanase-luc)-mediated luciferase activation were 5.8- and 4.3-folds higher than Ad5-CMV-luc, respectively (P = .02 and .03, respectively). At MOI of 50 pfu/cell, Ad-RGD-luc and AD-SLPI-luc mediated significantly higher gene transfer efficiency compared to Ad5-CMV-luc (P values < .001, for each virus). Ad-heparanase-luc achieved higher gene activity, but difference was not significant (P = .1). Ad-SLPI-luc, at low viral dose (10 pfu/ cell), mediated gene expression effect comparable to Ad5-CMV-luc at a high dose (50 pfu/cell), with no significant difference.

CONCLUSIONS

We conclude that when compared to the wild-type adenovirus, Ad-RGD-luc, Ad-SLPI-luc, and Ad-heparanase-luc mediate higher reporter gene activity in endometrial cells and can work as effective gene transfer vectors in gene therapy applications to the endometrium.

Efficacy and safety of myocardial gene transfer of adenovirus, adeno-associated virus and lentivirus vectors in the mouse heart

Gene therapy is a promising new treatment option for cardiac diseases. For finding the most suitable and safe vector for cardiac gene transfer, we delivered adenovirus (AdV), adeno-associated virus (AAV) and lentivirus (LeV) vectors into the mouse heart with sophisticated closed-chest echocardiography-guided intramyocardial injection method for comparing them with regards to transduction efficiency, myocardial damage, effects on the left ventricular function and electrocardiography (ECG). AdV had the highest transduction efficiency in cardiomyocytes followed by AAV2 and AAV9, and the lowest efficiency was seen with LeV. The local myocardial inflammation and fibrosis in the left ventricle (LV) was proportional to transduction efficiency. AdV caused LV dilatation and systolic dysfunction. Neither of the locally injected AAV serotypes impaired the LV systolic function, but AAV9 caused diastolic dysfunction to some extent. LeV did not affect the cardiac function. We also studied systemic delivery of AAV9, which led to transduction of cardiomyocytes throughout the myocardium. However, also diffuse fibrosis was present leading to significantly impaired LV systolic and diastolic function and pathological ECG changes. Compared with widely used AdV vector, AAV2, AAV9 and LeV were less effective in transducing cardiomyocytes but also less harmful. Local administration of AAV9 was safer and more efficient compared with systemic administration.

Cardiac gene therapy: Recent advances and future directions

Gene therapy has the potential to serve as an adaptable platform technology for treating various diseases. Cardiovascular disease is a major cause of mortality in the developed world and genetic modification is steadily becoming a more plausible method to repair and regenerate heart tissue. Recently, new gene targets to treat cardiovascular disease have been identified and developed into therapies that have shown promise in animal models. Some of these therapies have advanced to clinical testing. Despite these recent successes, several barriers must be overcome for gene therapy to become a widely used treatment of cardiovascular diseases. In this review, we evaluate specific genetic targets that can be exploited to treat cardiovascular diseases, list the important delivery barriers for the gene carriers, assess the most promising methods of delivering the genetic information, and discuss the current status of clinical trials involving gene therapies targeted to the heart.