Short noncoding DNA fragment improve efficiencies of in vivo electroporation-mediated gene transfer

Gene Therapy of Chronic Limb-Threatening Ischemia: Vascular Medical Perspectives

A decade ago, gene therapy seemed to be a promising approach for the treatment of chronic limb-threatening ischemia, providing new perspectives for patients without conventional, open or endovascular therapeutic options by potentially enabling neo-angiogenesis. Yet, until now, the results have been far from a safe and routine clinical application. In general, there are two approaches for inserting exogenous genes in a host genome: transduction and transfection. In case of transduction, viral vectors are used to introduce genes into cells, and depending on the selected strain of the virus, a transient or stable duration of protein production can be achieved. In contrast, the transfection of DNA is transmitted by chemical or physical processes such as lipofection, electro- or sonoporation. Relevant risks of gene therapy may be an increasing neo-vascularization in undesired tissue. The risks of malignant transformation and inflammation are the potential drawbacks. Additionally, atherosclerotic plaques can be destabilized by the increased angiogenesis, leading to arterial thrombosis. Clinical trials from pilot studies to Phase II and III studies on angiogenic gene therapy show mainly a mixed picture of positive and negative final results; thus, the role of gene therapy in vascular occlusive disease remains unclear.

Molecular mechanisms for enhanced DNA vaccine immunogenicity

In the two decades since their initial discovery, DNA vaccines technologies have come a long way. Unfortunately, when applied to human subjects inadequate immunogenicity is still the biggest challenge for practical DNA vaccine use. Many different strategies have been tested in preclinical models to address this problem, including novel plasmid vectors and codon optimization to enhance antigen expression, new gene transfection systems or electroporation to increase delivery efficiency, protein or live virus vector boosting regimens to maximise immune stimulation, and formulation of DNA vaccines with traditional or molecular adjuvants. Better understanding of the mechanisms of action of DNA vaccines has also enabled better use of the intrinsic host response to DNA to improve vaccine immunogenicity. This review summarizes recent advances in DNA vaccine technologies and related intracellular events and how these might impact on future directions of DNA vaccine development.

Physical energy for drug delivery; poration, concentration and activation

Techniques for controlling the rate and duration of drug delivery, while targeting specific locations of the body for treatment, to deliver the cargo (drugs or DNA) to particular parts of the body by what are becoming called "smart drug carriers" have gained increased attention during recent years. Using such smart carriers, researchers have also been investigating a number of physical energy forces including: magnetic fields, ultrasound, electric fields, temperature gradients, photoactivation or photorelease mechanisms, and mechanical forces to enhance drug delivery within the targeted cells or tissues and also to activate the drugs using a similar or a different type of external trigger. This review aims to cover a number of such physical energy modalities. Various advanced techniques such as magnetoporation, electroporation, iontophoresis, sonoporation/mechnoporation, phonophoresis, optoporation and thermoporation will be covered in the review. Special emphasis will be placed on photodynamic therapy owing to the experience of the authors' laboratory in this area, but other types of drug cargo and DNA vectors will also be covered. Photothermal therapy and theranostics will also be discussed.

Short-fragment DNA-mediated in vivo DNA electroporation delivery

Electroporation is an effective physical delivery method. A variety of factors have been shown to affect the electroporation-mediated gene delivery efficiency. Here we report the usefulness of noncoding short-fragment DNA (sf-DNA) for facilitating electroporation-mediated gene transfer. The plasmid pGL3-control encoding firefly luciferase was injected into tissue together with or without sf-DNA in different length or dose. Immediately after injection, the tissues were electroporated and the level of luciferase activity was assessed 24 h later. The results showed that plasmid DNA formulated with sf-DNA resulted in significant improvement in electroporation-mediated gene transfer efficiency. The effect is dose and length dependent, and also found in low-voltage electroporation. These results indicated that sf-DNA can be used as a helper molecule to improve the electroporation-mediated gene transfection efficiency.

The impact of non-electrical factors on electrical gene transfer

Electrical pulses directly and effectively boost both in vitro and in vivo gene transfer, but this process is greatly affected by non-electrical factors that exist during electroporation. These factors include, but are not limited to, the types of cells or tissues used, property of DNA, DNA formulation, and expressed protein. In this mini-review, we only describe and discuss a summary of DNA properties and selected DNA formulations on gene transfer via electroporation. The properties of DNA were selected for review because a substantial amount of remarkable work has been performed during the past few years but has received less notice than other works, although DNA properties appear to be critical for boosting electroporation delivery. The selected formulations will be covered in this mini-review because we are only interested in the simple formulations that could be used for cell or gene therapy via electroporation. Plus, there was an extensive review of DNA formulations in the first edition of this book. The formulations discussed in this mini-review represent novel developments in recent years and may impact electroporation significantly. These advancements in DNA formulations could prove to be important for gene delivery and disease treatment.

Novel gene delivery systems

Gene therapy is an emerging field in medical and pharmaceutical sciences because of its potential in treating chronic diseases like cancer, viral infections, myocardial infarctions, and genetic disorders. Application of gene therapy is limited because of lack of suitable methods for proper introduction of genes into cells and therefore, this is an area of interest for most of the researchers. To achieve successful gene therapy, development of proper gene delivery systems could be one of the most important factors. Several nonviral and viral gene transfer methods have been developed. Even though the viral agents have a high transferring efficiency, they are difficult to handle due to their toxicity. To overcome the safety problems of the viral counterpart, several nonviral in vitro and in vivo gene delivery systems are developed. Out of these, the most promising and latest systems include polymer-based nonviral gene carriers, dendrimers, and physical means like electroporation, microinjection, etc., Shunning of possible immunogenicity and toxicity, and the feasibility of repeated administration are some of the merits of nonviral gene delivery systems over viral gene delivery. An ideal nonviral gene carrying system should possess all these merits without any compromise to its gene transferring efficiency. The viral gene delivery systems include lytic and nonlytic vectors for drug delivery. Inspite of its toxicity they are still preferred because of their long term expression, stability, and integrity. This review explores the recent developments and relevancy of the novel gene delivery systems in gene therapy.