Non‐viral gene therapy for myocardial engineering

Abstract

Despite significant advances in surgical and pharmacological techniques, myocardial infarction remains the main cause of morbidity in the developed world because no remedy has been found for the regeneration of infarcted myocardium. Once the blood supply to the area in question is interrupted, the inflammatory cascade, among other mechanisms, results in the damaged tissue becoming a scar. The goals of cardiac gene therapy are essentially to minimize damage, to promote regeneration or some combination thereof. While the vector is, in theory, less important than the gene being delivered, the choice of vector can have a significant impact. Viral therapies can have very high transfection efficiencies, but disadvantages include immunogenicity, retroviralmediated insertional mutagenesis and the expense and difficulty of manufacture. For these reasons, researchers have focused on non-viral gene therapy as an alternative. In this review, naked plasmid delivery, or the delivery of complexed plasmids, and cellmediated gene delivery to the myocardium will be reviewed. Pre-clinical and clinical trials in the cardiac tissue will form the core of the discussion. While unmodified stem cells are sometimes considered therapeutic vectors based on paracrine mechanisms of action basic understanding is limited. Thus, only genetically modified cells will be discussed as cell-mediated gene therapy.Ischemic heart disease, which includes acute damage due to myocardial infarction (MI) and chronic damage due to atherosclerotic narrowing of vessels, accounts for 35% of deaths reported in the United States every year [1]. MI, which is literally the death of cardiac tissue due to lack of 2 oxygen supply, is the result of the occlusion of a coronary artery. Within a few hours of interrupted blood supply, affected cardiomyocytes die. While the body has adaptive mechanisms, such as hypertrophy of the undamaged cardiac muscle and the development of collateral blood supply to minimize the damage, ischemic heart disease remains the most common cause of death in developed countries [2].The delivery of plasmid DNA to the myocardium is a complicated problem as the transfection efficiency of unmodified DNA is quite low, but complexation with agents designed to improve transfection can increase the cytotoxicity of the treatment [3]. Delivery of uncomplexed plasmid DNA is conceptually the simplest gene delivery technique, but these plasmids have extremely low transfection efficiencies in vitro and are not particularly effective in vivo. Compared to viral vectors, transgene expression is almost negligible and the expression time is also very limited [4]. However, there are significant advantages in using plasmids instead of viruses, such as ease of preparation (large and small scale), very low immunogenicity (as there are essentially no protein or membrane components in the plasmid), capacity for long term storage, ease of recombinant manipulation and much larger expression cassettes [4]. A variety of non-viral techniques are available to improve...

Therapeutic effects of hepatocyte growth factor‐overexpressing human umbilical cord blood‐derived mesenchymal stem cells on liver fibrosis in rats

“…Among the viral vector systems, systems based on retroviral vectors have been used for gene delivery into rat livers after partial hepatectomy, with 1-5% of hepatocytes being transfected in this model (Ferry et al, 1991). The highest transfection efficiencies are obtained with viral vectors (Holladay et al, 2010). Regarding non-viral vector systems, the haemagglutinating virus of Japan (HVJ) liposome method, which is a non-viral vector system, has no side effects (Kaneda et al, 1989a, b;Kato et al, 1991;Matsuno et al, 2003).…”

“…Adenoviral vectors can induce efficient gene expression in hepatocytes in vivo; however, these vectors can lead to transient gene expression and give some side effects, for example cytotoxicity and immune responses (Li et al, 1993;Yang et al, 1994;Marshall, 1999;Powell et al, 1999;Rabinowitz et al, 1999). However, cell-mediated gene transfer is unlike other methods of gene transfer (Holladay et al, 2010), and the transfection efficiency is not really an issue because the cells that do take up the gene are selectively cultured, while those that do not are eliminated. However, expression of the introduced gene is transient in this system.…”

Sample displacement chromatography of plasmid DNA isoforms

“…Despite the increasing pharmaceutical potential of plasmid DNA (pDNA), which is typically purified using step gradient elution [16,17], only a single study applied DC/SDC approach to its purification [18]. The study demonstrated that conventional porous particle columns were not suited to the separation of any two substances varying considerably in molecular mass, whereas of separation of pDNA from host cell proteins (HCP) and endotoxin was achieved using a continuous bed column.…”

Cellular Injury of Cardiomyocytes during Hepatocyte Growth Factor Gene Transfection with Ultrasound-Triggered Bubble Liposome Destruction

“…This is especially true in cardiovascular medicine, where malignant cellular transformation is rare [17]. One of the promising candidates for safe and efficacious gene transfection is a naked plasmid vector that has been modified to have high affinity for cardiovascular tissues but which has no built-in viral components [17, 18]. We have developed a method for electroporation of a cytokine gene for treatment of cardiomyopathy [13].…”