Electroporation for gene transfer to skeletal muscles: current status

Evaluation of protective immune responses induced by DNA vaccines encoding Echinococcus granulosus EgM123 protein in Beagle dogs

Introduction

Echinococcus granulosus, known as cystic echinococcosis, is a prominent zoonotic parasitic disease of significant global concern. The definitive hosts serves as the primary reservoir for the transmission of echinococcosis, as well as a main factor in the prevention and control of the disease. Unfortunately, there is currently no commercially available vaccine for these hosts. Nevertheless, DNA vaccines show potential as a feasible strategy for the control and management of parasitic diseases.

Methods

In this study, the EgM123 antigen was selected for its well-documented immunogenic properties to develop a DNA vaccine aimed at combating E. granulosus infection in canines.

Results

The results showed a marked increase in IgG levels in the group vaccinated with pVAX1-EgM123 DNA compared to the PBS group. Additionally, the cytokines IL-1, IFN-γ, IL-4, and IL-6 were significantly upregulated in the pVAX1-EgM123 DNA vaccine group. Furthermore, in comparison to the PBS control group, the EgM123 DNA vaccine group exhibited a notable 87.85% reduction in worm burden and a 65.00% inhibition in segment development.

Discussion

These findings indicate that the pVAX1-EgM123 DNA vaccine shows promising immunogenicity, successfully eliciting a targeted immune response in canines. Moreover, it significantly diminishes the worm burden and hinders the progression of tapeworms in the pVAX1-EgM123 DNA vaccine group. These findings suggest that the pVAX1-EgM123 DNA vaccine holds promise as a potential candidate vaccine for combating E. granulosus infection in dogs.

Importance of the electrophoresis and pulse energy for siRNA-mediated gene silencing by electroporation in differentiated primary human myotubes

BACKGROUND

Electrotransfection is based on application of high-voltage pulses that transiently increase membrane permeability, which enables delivery of DNA and RNA in vitro and in vivo. Its advantage in applications such as gene therapy and vaccination is that it does not use viral vectors. Skeletal muscles are among the most commonly used target tissues. While siRNA delivery into undifferentiated myoblasts is very efficient, electrotransfection of siRNA into differentiated myotubes presents a challenge. Our aim was to develop efficient protocol for electroporation-based siRNA delivery in cultured primary human myotubes and to identify crucial mechanisms and parameters that would enable faster optimization of electrotransfection in various cell lines.

RESULTS

We established optimal electroporation parameters for efficient siRNA delivery in cultured myotubes and achieved efficient knock-down of HIF-1α while preserving cells viability. The results show that electropermeabilization is a crucial step for siRNA electrotransfection in myotubes. Decrease in viability was observed for higher electric energy of the pulses, conversely lower pulse energy enabled higher electrotransfection silencing yield. Experimental data together with the theoretical analysis demonstrate that siRNA electrotransfer is a complex process where electropermeabilization, electrophoresis, siRNA translocation, and viability are all functions of pulsing parameters. However, despite this complexity, we demonstrated that pulse parameters for efficient delivery of small molecule such as PI, can be used as a starting point for optimization of electroporation parameters for siRNA delivery into cells in vitro if viability is preserved.

CONCLUSIONS

The optimized experimental protocol provides the basis for application of electrotransfer for silencing of various target genes in cultured human myotubes and more broadly for electrotransfection of various primary cell and cell lines. Together with the theoretical analysis our data offer new insights into mechanisms that underlie electroporation-based delivery of short RNA molecules, which can aid to faster optimisation of the pulse parameters in vitro and in vivo.

Electroporation in Translational Medicine: From Veterinary Experience to Human Oncology

Electroporation (EP) is a broadly accepted procedure that, through the application of electric pulses with appropriate amplitudes and waveforms, promotes the delivery of anticancer molecules in various oncology therapies. EP considerably boosts the absorptivity of targeted cells to anticancer molecules of different natures, thus upgrading their effectiveness. Its use in veterinary oncology has been widely explored, and some applications, such as electrochemotherapy (ECT), are currently approved as first-line treatments for several neoplastic conditions. Other applications include irreversible electroporation and EP-based cancer vaccines. In human oncology, EP is still mostly restricted to therapies for cutaneous tumors and the palliation of cutaneous and visceral metastases of malignant tumors. Fields where veterinary experience could help smooth the clinical transition to humans include intraoperative EP, interventional medicine and cancer vaccines. This article recapitulates the state of the art of EP in veterinary and human oncology, recounting the most relevant results to date.

In Vivo and Ex Vivo Gene Electrotransfer in Ophthalmological Disorders

The aim of this document is to present an overview of gene electrotransfer in ophthalmological disorders. In order to ensure an adequate variety of the assessed studies, several electronic databases were considered and studies published between January 1998 and December 2021 were analysed. Three investigators carried out data extraction and analysis, focusing on both technical (i.e., electrical protocol, type of electrode, plasmid) and medical (i.e., type of study, threated disease) aspects and highlighting the main differences in terms of results obtained. Moreover, the IGEA experience in the project “Transposon-based, targeted ex vivo gene therapy to treat age-related macular degeneration” (TargetAMD) was reported in the results section. No clinical trial was found on international literature and on ClinicalTrials.gov. Twelve preclinical studies were found including in vivo and ex-vivo applications. The studied showed that electrotransfer could be very efficient for plasmid DNA transfection. Many attempts such as modification of the electric field, buffers and electrodes have been made and the optimization of electric field setting seems to be very important. Using this technique, gene replacement can be designed in cases of retinal inheritance or corneal disease and a wide range of human eye diseases could, in the future, benefitfrom these gene therapy technologies.

CORP: Gene delivery into murine skeletal muscle using in vivo electroporation

The strategy of gene delivery into skeletal muscles has provided exciting avenues in identifying new potential therapeutics towards muscular disorders and addressing basic research questions in muscle physiology through overexpression and knockdown studies. In vivo electroporation methodology offers a simple, rapidly effective technique for the delivery of plasmid DNA into post-mitotic skeletal muscle fibers and the ability to easily explore the molecular mechanisms of skeletal muscle plasticity. The purpose of this review is to describe how to robustly electroporate plasmid DNA into different hindlimb muscles of rodent models. Further, key parameters (e.g., voltage, hyaluronidase, plasmid concentration) which contribute to the successful introduction of plasmid DNA into skeletal muscle fibers will be discussed. In addition, details on processing tissue for immunohistochemistry and fiber cross-sectional area (CSA) analysis will be outlined. The overall goal of this review is to provide the basic and necessary information needed for successful implementation of in vivo electroporation of plasmid DNA and thus open new avenues of discovery research in skeletal muscle physiology.

Sonodelivery in Skeletal Muscle: Current Approaches and Future Potential

There are currently multiple approaches to facilitate gene therapy via intramuscular gene delivery, such as electroporation, viral delivery, or direct DNA injection with or without polymeric carriers. Each of these methods has benefits, but each method also has shortcomings preventing it from being established as the ideal technique. A promising method, ultrasound-mediated gene delivery (or sonodelivery) is inexpensive, widely available, reusable, minimally invasive, and safe. Hurdles to utilizing sonodelivery include choosing from a large variety of conditions, which are often dependent on the equipment and/or research group, and moderate transfection efficiencies when compared to some other gene delivery methods. In this review, we provide a comprehensive look at the breadth of sonodelivery techniques for intramuscular gene delivery and suggest future directions for this continuously evolving field.

Definition of a Novel Plasmid-Based Gene Transfection Protocol of Mammalian Skeletal Muscles by Means of In Vivo Electroporation

We describe an original electroporation protocol for in vivo plasmid DNA transfection. The right hind limbs of C57 mice are exposed to a specifically designed train of permeabilizing electric pulses by transcutaneous application of tailored needle electrodes, immediately after the injection of pEGFP-C1 plasmid encoding GFP (Green Fluorescente Protein). The electroporated rodents show a greater GFP expression than the controls at three different time points (4, 10, and 15 days). The electroporated muscles display only mild interstitial myositis, with a significant increase in inflammatory cell infiltrates. Finally, mild gait abnormalities are registered in electroporated mice only in the first 48 h after the treatment. This protocol has proven to be highly efficient in terms of expression levels of the construct, is easy to apply since it does not require surgical exposure of the muscle and is well tolerated by the animals because it does not cause evident morphological and functional damage to the electroporated muscle.

Twist3 is required for dedifferentiation during extraocular muscle regeneration in adult zebrafish

Severely damaged adult zebrafish extraocular muscles (EOMs) regenerate through dedifferentiation of residual myocytes involving a muscle-to-mesenchyme transition. Members of the Twist family of basic helix-loop-helix transcription factors (TFs) are key regulators of the epithelial-mesenchymal transition (EMT) and are also involved in craniofacial development in humans and animal models. During zebrafish embryogenesis, twist family members (twist1a, twist1b, twist2, and twist3) function to regulate craniofacial skeletal development. Because of their roles as master regulators of stem cell biology, we hypothesized that twist TFs regulate adult EOM repair and regeneration. In this study, utilizing an adult zebrafish EOM regeneration model, we demonstrate that inhibiting twist3 function using translation-blocking morpholino oligonucleotides (MOs) impairs muscle regeneration by reducing myocyte dedifferentiation and proliferation in the regenerating muscle. This supports our hypothesis that twist TFs are involved in the early steps of dedifferentiation and highlights the importance of twist3 during EOM regeneration.

PGC-1α Overexpression via Local In Vivo Transfection in Mouse Skeletal Muscle

The overexpression of a specific protein is a common method for investigating the specific biological function of the substance and the mechanism of action. In vivo electrotransfer has been confirmed to be one of the most reliable, efficient and cost-effective way to overexpress a protein in a select biological tissue. Typically, this technique involves a physical injection of plasmid DNA followed by electric pulses across the injection site. Here, we introduce this method that we used to transfect green fluorescent protein (GFP)-tagged PGC-1α plasmid DNA into mouse tibialis anterior (TA) muscle, which attained high transfection efficiency with no muscle damage. To quantify the transfection efficiency, we also demonstrate the visualization of plasmid DNA transfected fibers via immunohistochemical staining on muscle cross sections.

Clinically Usable Interleukin 12 Plasmid without an Antibiotic Resistance Gene: Functionality and Toxicity Study in Murine Melanoma Model

Plasmids, which are currently used in interleukin 12 (IL-12) gene electrotransfer (GET) clinical trials in the USA, contain antibiotic resistance genes and are thus, according to the safety recommendation of the European Medicines Agency (EMA), not suitable for clinical trials in the EU. In the current study, our aim was to prepare an IL-12 plasmid without an antibiotic resistance gene and test its functionality and toxicity after GET in a preclinical B16F10 mouse melanoma model. The antibiotic resistance-free plasmid encoding the human IL-12 fusion gene linked to the p21 promoter, i.e., p21-hIL-12-ORT, was constructed using operator-repressor titration (ORT) technology. Next, the expression profile of the plasmid after GET was determined in B16F10 cells and tumors. Additionally, blood chemistry, hematological and histological changes, and antitumor response were evaluated after GET of the plasmid in melanoma tumors. The results demonstrated a good expression and safety profile of the p21-hIL-12-ORT GET and indications of efficacy. We hope that the obtained results will help to accelerate the transfer of this promising treatment from preclinical studies to clinical application in the EU.

Selection and Identification of Skeletal-Muscle-Targeted RNA Aptamers

Oligonucleotide gene therapy has shown great promise for the treatment of muscular dystrophies. Nevertheless, the selective delivery to affected muscles has shown to be challenging because of their high representation in the body and the high complexity of their cell membranes. Current trials show loss of therapeutic molecules to non-target tissues leading to lower target efficacy. Therefore, strategies that increase uptake efficiency would be particularly compelling. To address this need, we applied a cell-internalization SELEX (Systematic Evolution of Ligands by Exponential Enrichment) approach and identified a skeletal muscle-specific RNA aptamer. A01B RNA aptamer preferentially internalizes in skeletal muscle cells and exhibits decreased affinity for off-target cells. Moreover, this in vitro selected aptamer retained its functionality in vivo, suggesting a potential new approach for targeting skeletal muscles. Ultimately, this will aid in the development of targeted oligonucleotide therapies against muscular dystrophies.

Comparison of Different Electroporation Parameters on Transfection Efficiency of Sheep Testicular Cells

OBJECTIVE

Electroporation can be a highly efficient method for introducing the foreign genetic materials into the targeted cells for transient and/or permanent genetic modification. Considering the application of this technique as a very efficient method for drug, oligonucleotide, antibody and plasmid delivery for clinical applications and production of transgenic animals, the present study aimed to optimize the transfection efficiency of sheep testicular cells including spermatogonial stem cells (SSCs) via electroporation.

MATERIALS AND METHODS

This study is an experimental research conducted in Biotechnology Research Center (Avicenna Research Institute, Tehran, Iran) from September 2013 to March 2014. Following isolation and propagation of one-month lamb testicular cells (SSCs and somatic testicular cells including; Sertoli, Leydig, and myoid cells), the effect of different electroporation parameters including total voltages (280, 320, and 350 V), burst durations (10, 8, and 5 milliseconds), burst modes (single or double) and addition of dimethyl sulfoxide (DMSO) were evaluated on transfection efficiency, viability rate and mean fluorescent intensity (MFI) of sheep testicular cells.

RESULTS

The most transfection efficiency was obtained in 320 V/8 milliseconds/single burst group in transduction medium with and without DMSO. There was a significantly inverse correlation between transfection efficiency with application of both following parameters: addition of DMSO and double burst. After transfection, the highest and lowest viability rates of testicular cells were demonstrated in 320 V/8 milliseconds with transduction medium without DMSO and 350 V/5 milliseconds in medium containing DMSO. Ad- dition of DMSO to transduction medium in all groups significantly decreased the viability rate. The comparison of gene expression indicated that Sertoli and SSCs had the most fluorescence intensity in 320 V/double burst/DMSO positive. However, myoid and Leydig cells showed the maximum expression in 320 V/single burst and/or 350 V/double burst/ DMSO positive.

CONCLUSION

We optimized the electroporation method for transfection of sheep testicular cells and recommended the application of 320 V/8 milliseconds/single pulse/DMSO negative for transduction of plasmid vector into these cells. Among testicular cells, the most external gene expression was demonstrated in SSC population.

Partial correction of the dwarf phenotype by non-viral transfer of the growth hormone gene in mice: Treatment age is critical

Non-viral transfer of the growth hormone gene to different muscles of immunodeficient dwarf (lit/scid) mice is under study with the objective of improving phenotypic correction via this particular gene therapy approach. Plasmid DNA was administered into the exposed quadriceps or non-exposed tibialis cranialis muscle of lit/scid mice followed by electroporation, monitoring several growth parameters. In a 6-month bioassay, 50μg DNA were injected three times into the quadriceps muscle of 80-day old mice. A 50% weight increase, with a catch-up growth of 21%, together with a 16% increase for nose-to-tail and tail lengths (catch-up=19-21%) and a 24-28% increase for femur length (catch-up=53-60%), were obtained. mIGF1 serum levels were ~7-fold higher than the basal levels for untreated mice, but still ~2-fold lower than in non-dwarf scid mice. Since treatment age was found to be particularly important in a second bioassay utilizing 40-day old mice, these pubertal mice were compared in a third bioassay with adult (80-day old) mice, all treated twice with 50μg DNA injected into each tibialis cranialis muscle, via a less invasive approach. mIGF1 concentrations at the same level as co-aged scid mice were obtained 15days after administration in pubertal mice. Catch-up growth, based on femur length (77%), nose-to-tail (36%) and tail length (39%) increases was 40 to 95% higher than those obtained upon treating adult mice. These data pave the way for the development of more effective pre-clinical assays in pubertal dwarf mice for the treatment of GH deficiency via plasmid-DNA muscular administration.

A review of basic to clinical studies of irreversible electroporation therapy

The use of irreversible electroporation (IRE) for cancer treatment has increased sharply over the past decade. As a nonthermal therapy, IRE offers several potential benefits over other focal therapies, which include 1) short treatment delivery time, 2) reduced collateral thermal injury, and 3) the ability to treat tumors adjacent to major blood vessels. These advantages have stimulated widespread interest in basic through clinical studies of IRE. For instance, many in vitro and in vivo studies now identify treatment planning protocols (IRE threshold, pulse parameters, etc.), electrode delivery (electrode design, placement, intraoperative imaging methods, etc.), injury evaluation (methods and timing), and treatment efficacy in different cancer models. Therefore, this study reviews the in vitro, translational, and clinical studies of IRE cancer therapy based on major experimental studies particularly within the past decade. Further, this study provides organized data and facts to assist further research, optimization, and clinical applications of IRE.

Physical methods for gene transfer

The key impediment to the successful application of gene therapy in clinics is not the paucity of therapeutic genes. It is rather the lack of nontoxic and efficient strategies to transfer therapeutic genes into target cells. Over the past few decades, considerable progress has been made in gene transfer technologies, and thus far, three different delivery systems have been developed with merits and demerits characterizing each system. Viral and chemical methods of gene transfer utilize specialized carrier to overcome membrane barrier and facilitate gene transfer into cells. Physical methods, on the other hand, utilize various forms of mechanical forces to enforce gene entry into cells. Starting in 1980s, physical methods have been introduced as alternatives to viral and chemical methods to overcome various extra- and intracellular barriers that limit the amount of DNA reaching the intended cells. Accumulating evidence suggests that it is quite feasible to directly translocate genes into cytoplasm or even nuclei of target cells by means of mechanical force, bypassing endocytosis, a common pathway for viral and nonviral vectors. Indeed, several methods have been developed, and the majority of them share the same underlying mechanism of gene transfer, i.e., physically created transient pores in cell membrane through which genes get into cells. Here, we provide an overview of the current status and future research directions in the field of physical methods of gene transfer.

DNA electroporation of multi-agent vaccines conferring protection against select agent challenge: TriGrid delivery system

Effective multi-agent/multivalent vaccines that confer protection against more than one disease are highly desirable to the patient and to health-care professionals. Electroporation of DNA vaccines, whereby tissues injected with DNA are subjected to localized electrical currents, is an ideal platform technology that achieves protective immune responses to multivalent vaccination. Here, we describe an electroporation-based immunization technique capable of administering a cocktail of DNA vaccinations in vivo. Immune response measurements, including protection from pathogen challenge and induction of antigen-specific antibody responses and cell-mediated immune responses, are also discussed.

Evolution of electroporated DNA vaccines

Vaccines have evolved for hundreds of years, but all utilize the premise that safely pre-exposing the host to some component of a pathogen allows for enhanced immune recognition, and potential protection from disease, upon encountering the pathogen at a later date. Early vaccination strategies used inactivated or attenuated vaccines, many of which contained toxins and other components that resulted in reactogenicity or risk of reversion to virulence. DNA vaccines supplant many of the issues associated with inactivated or attenuated vaccines, but these vaccines tend to provide weak immunological responses, particularly in primates. DNA Electroporation may prove to be the "missing link" in the evolution of DNA vaccines allowing for enhanced immune responses from DNA vaccination in humans thereby resulting in protection from disease post-pathogen exposure.

DNA immunization

DNA immunization was discovered in early 1990s, and its use has been expanded from vaccine studies to a broader range of biomedical research areas, such as the generation of high-quality polyclonal and monoclonal antibodies as research reagents. In this unit, three common DNA immunization methods are described: needle injection, electroporation, and gene gun. In addition, several common considerations related to DNA immunization are discussed.

Assessment of delivery parameters with the multi-electrode array for development of a DNA vaccine against Bacillus anthracis

Gene electrotransfer (GET) enhances delivery of DNA vaccines by increasing both gene expression and immune responses. Our lab has developed the multi-electrode array (MEA) for DNA delivery to skin. The MEA was used at constant pulse duration (150 ms) and frequency (6.67 Hz). In this study, delivery parameters including applied voltage (5-45 V), amount of plasmid (100-300 μg), and number of treatments (2-3) were evaluated for delivery of a DNA vaccine. Mice were intradermally injected with plasmid expressing Bacillus anthracis protective antigen with or without GET and αPA serum titers measured. Within this experiment no significant differences were noted in antibody levels from varying dose or treatment number. However, significant differences were measured from applied voltages of 25 and 35 V. These voltages generated antibody levels between 20,000 and 25,000. Serum from animals vaccinated with these conditions also resulted in toxin neutralization in 40-60% of animals. Visual damage was noted at MEA conditions of 40 V. No damage was noted either visually or histologically from conditions of 35 V or below. These results reflect the importance of establishing appropriate electrical parameters and the potential for the MEA in non-invasive DNA vaccination against B. anthracis.

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

BACKGROUND

A major obstacle to the application of gene therapy methods in experimental and clinical practice is the lack of safe and efficient gene delivery systems. Electroporation has been shown to an effective physical delivery method. A variety of factors have been shown to affect the electroporation-mediated gene delivery efficiency. In the present study, we assessed the usefulness of noncoding short-fragment DNA (sf-DNA) for facilitating electroporation-mediated gene transfer.

METHODS

The plasmid pGL3-control encoding firefly luciferase was injected into tissues together with or without sf-DNA. Immediately after injection, the tissues were electroporated and the level of luciferase activity was assessed 24 h later. Different types of DNA fragments with different molecular weights, structures and doses were compared. The transfection efficiencies of sf-DNA-mediated electroporation in different tissues or with different electric field strengths were examined.

RESULTS

Plasmid DNA formulated with 300-bp sf-DNA resulted in a significant improvement in electroporation-mediated gene transfer efficiency. The effect is dose-dependent and is also affected by DNA fragment length and structure. It was useful for intramuscular electroporation application, as well as intratumoral application with various pulse voltage parameters.

CONCLUSIONS

The data obtained in the present study indicate that sf-DNA can be used as a helper molecule to improve electroporation-mediated gene transfection efficiency.

Myocardial gene transfer: routes and devices for regulation of transgene expression by modulation of cellular permeability

Heart diseases are major causes of morbidity and mortality in Western society. Gene therapy approaches are becoming promising therapeutic modalities to improve underlying molecular processes affecting failing cardiomyocytes. Numerous cardiac clinical gene therapy trials have yet to demonstrate strong positive results and advantages over current pharmacotherapy. The success of gene therapy depends largely on the creation of a reliable and efficient delivery method. The establishment of such a system is determined by its ability to overcome the existing biological barriers, including cellular uptake and intracellular trafficking as well as modulation of cellular permeability. In this article, we describe a variety of physical and mechanical methods, based on the transient disruption of the cell membrane, which are applied in nonviral gene transfer. In addition, we focus on the use of different physiological techniques and devices and pharmacological agents to enhance endothelial permeability. Development of these methods will undoubtedly help solve major problems facing gene therapy.

Viral and nonviral delivery systems for gene delivery

Gene therapy is the process of introducing foreign genomic materials into host cells to elicit a therapeutic benefit. Although initially the main focus of gene therapy was on special genetic disorders, now diverse diseases with different patterns of inheritance and acquired diseases are targets of gene therapy. There are 2 major categories of gene therapy, including germline gene therapy and somatic gene therapy. Although germline gene therapy may have great potential, because it is currently ethically forbidden, it cannot be used; however, to date human gene therapy has been limited to somatic cells. Although numerous viral and nonviral gene delivery systems have been developed in the last 3 decades, no delivery system has been designed that can be applied in gene therapy of all kinds of cell types in vitro and in vivo with no limitation and side effects. In this review we explain about the history of gene therapy, all types of gene delivery systems for germline (nuclei, egg cells, embryonic stem cells, pronuclear, microinjection, sperm cells) and somatic cells by viral [retroviral, adenoviral, adeno association, helper-dependent adenoviral systems, hybrid adenoviral systems, herpes simplex, pox virus, lentivirus, Epstein-Barr virus)] and nonviral systems (physical: Naked DNA, DNA bombardant, electroporation, hydrodynamic, ultrasound, magnetofection) and (chemical: Cationic lipids, different cationic polymers, lipid polymers). In addition to the above-mentioned, advantages, disadvantages, and practical use of each system are discussed.

Bone marrow-CNS connections: implications in the pathogenesis of diabetic retinopathy

Diabetic retinopathy is the fourth most common cause of blindness in adults. Current therapies, including anti-VEGF therapy, have partial efficacy in arresting the progression of proliferative diabetic retinopathy and diabetic macular edema. This review provides an overview of a novel, innovative approach to viewing diabetic retinopathy as the result of an inflammatory cycle that affects the bone marrow (BM) and the central and sympathetic nervous systems. Diabetes associated inflammation may be the result of BM neuropathy which skews haematopoiesis towards generation of increased inflammatory cells but also reduces production of endothelial progenitor cells responsible for maintaining healthy endothelial function and renewal. The resulting systemic inflammation further impacts the hypothalamus, promoting insulin resistance and diabetes, and initiates an inflammatory cascade that adversely impacts both macrovascular and microvascular complications, including diabetic retinopathy (DR). This review examines the idea of using anti-inflammatory agents that cross not only the blood-retinal barrier to enter the retina but also have the capability to target the central nervous system and cross the blood-brain barrier to reduce neuroinflammation. This neuroinflammation in key sympathetic centers serves to not only perpetuate BM pathology but promote insulin resistance which is characteristic of type 2 diabetic patients (T2D) but is also seen in T1D. A case series of morbidly obese T2D patients with retinopathy and neuropathy treated with minocycline, a well-tolerated antibiotic that crosses both the blood-retina and blood-brain barrier is presented. Our results indicates that minocycine shows promise for improving visual acuity, reducing pain from peripheral neuropathy, promoting weight loss and improving blood pressure control and we postulate that these observed beneficial effects are due to a reduction of chronic inflammation.

Evaluation of a novel non-penetrating electrode for use in DNA vaccination

Current progress in the development of vaccines has decreased the incidence of fatal and non-fatal infections and increased longevity. However, new technologies need to be developed to combat an emerging generation of infectious diseases. DNA vaccination has been demonstrated to have great potential for use with a wide variety of diseases. Alone, this technology does not generate a significant immune response for vaccination, but combined with delivery by electroporation (EP), can enhance plasmid expression and immunity. Most EP systems, while effective, can be invasive and painful making them less desirable for use in vaccination. Our lab recently developed a non-invasive electrode known as the multi-electrode array (MEA), which lies flat on the surface of the skin without penetrating the tissue. In this study we evaluated the MEA for its use in DNA vaccination using Hepatitis B virus as the infectious model. We utilized the guinea pig model because their skin is similar in thickness and morphology to humans. The plasmid encoding Hepatitis B surface antigen (HBsAg) was delivered intradermally with the MEA to guinea pig skin. The results show increased protein expression resulting from plasmid delivery using the MEA as compared to injection alone. Within 48 hours of treatment, there was an influx of cellular infiltrate in experimental groups. Humoral responses were also increased significantly in both duration and intensity as compared to injection only groups. While this electrode requires further study, our results suggest that the MEA has potential for use in electrically mediated intradermal DNA vaccination.

Dynamics and control of the two-pulse protocol in electroporation: numerical exploration

Externally applied voltages can create transient, non-selective pores in a cell's membrane, a phenomenon known as electroporation. Electroporation has reduced toxicity, is easy to perform, and does not induce the immune system. Therefore, the technique has a wide range of biological and medical applications. Previous experiments show that a two-pulse protocol, which consists of a fast, large-magnitude pulse and a slow, small-magnitude pulse, can increase the efficiency of drug delivery such as gene electrotransfer. In this work, we investigate the dynamics and control of the two-pulse protocol using a macroscopic model of electroporation. Numerical simulations show that there exists a range of pore radii that cannot be sustained using the conventional, open-loop, two-pulse protocol. As a result, one may need to use pores that are significantly larger than the sizes of the targeted molecules. Moreover, it is not possible to know the rate of delivery a priori. To ensure accurate drug delivery and avoid potential damage to the cell's membrane, we explore feedback mechanisms to eliminate the gap in sustainable pore radii and thus to precisely control the electroporation process. Numerical simulations show that a straightforward feedback algorithm can achieve robust control effects. Moreover, the control algorithm is effective without knowledge of the model and thus has the potential to be implemented in experiments.

Protein delivery for retinal diseases: from basic considerations to clinical applications

Because the eye is protected by ocular barriers but is also easily accessible, direct intravitreous injections of therapeutic proteins allow for specific and targeted treatment of retinal diseases. Low doses of proteins are required in this confined environment and a long time of residency in the vitreous is expected, making the eye the ideal organ for local proteic therapies. Monthly intravitreous injection of Ranibizumab, an anti-VEGF Fab has become the standard of care for patients presenting wet AMD. It has brought the proof of concept that administering proteins into the physiologically low proteic concentration vitreous can be performed safely. Other antibodies, Fab, peptides and growth factors have been shown to exert beneficial effects on animal models when administered within the therapeutic and safe window. To extend the use of such biomolecules in the ophthalmology practice, optimization of treatment regimens and efficacy is required. Basic knowledge remains to be increased on how different proteins/peptides penetrate into the eye and the ocular tissues, distribute in the vitreous, penetrate into the retinal layers and/or cells, are eliminated from the eye or metabolized. This should serve as a basis for designing novel drug delivery systems. The later should be non-or minimally invasive and should allow for a controlled, scalable and sustained release of the therapeutic proteins in the ocular media. This paper reviews the actual knowledge regarding protein delivery for eye diseases and describes novel non-viral gene therapy technologies particularly adapted for this purpose.

Electroporation and ultrasound enhanced non-viral gene delivery in vitro and in vivo

Non-viral vectors are less efficient than the use of viral vectors for delivery of genetic material to cells in vitro and especially in vivo. However, viral vectors involve the use of foreign proteins that can stimulate both the innate and acquired immune response. In contrast, plasmid DNA can be delivered without carrier proteins and is non-immunogenic. Plasmid gene delivery can be enhanced by the use of physical methods that aid the passage of the plasmid through the cell membrane. Electroporation and microbubble-enhanced ultrasound are two of the most effective physical delivery methods and these can be applied to a range of different cell types in vitro and a broad range of tissues in vivo. Both techniques also have the advantage that, unlike viral vectors, they can be used to target specific tissues with systemic delivery. Although electroporation is often the more efficient of the two, microbubble-enhanced ultrasound causes less damage and is less invasive. This review provides an introduction to the methodology and summarises the range of cells and tissues that have been genetically modified using these techniques.

Quantitative real-time PCR study on persistence of pDNA vaccine pVax-Hsp60 TM814 in beef muscles

Background

Application of plasmid DNA for immunization of food-producing animals established new standards of food safety. The addition of foreign products e.g. pDNA into the food chain should be carefully examined to ensure that neither livestock animals nor consumers develop unpredicted or undesirable side-effects.

Methods

A quantitative real-time PCR (QRTPCR) methodology was developed to study the biodistribution and persistence of plasmid DNA vaccine pDNAX (pVAX-Hsp60 TM814) in mice and beef cattle. The linear quantification range and the sensitivity of the method was found to be 10 – 10⁹ copies per reaction (500 ng/gDNA) and 3 copies per reaction, respectively.

Results

Persistence of pDNAX in mice muscle tissue was restricted to injection site and the amount of pDNAX showed delivery formulation dependent (naked pDNA, electroporation, cationic liposome complexes) and mouse age-dependent clearance form injection site but pDNAX was still detectable even after 365 days. The QRTPCR analysis of various muscle tissue samples of vaccinated beef bulls performed 242–292 days after the last revaccination proved that residual pDNAX was found only in the injection site. The highest plasmid levels (up to 290 copies per reaction) were detected in the pDNAX:CDAN/DOPE group similarly to mice model. No pDNA was detected in the samples from distant muscles and draining lymph nodes.

Conclusion

Quantitative real-time PCR (QRTPCR) assay was developed to assess the residual pDNA vaccine pVAX-Hsp60 TM814 in mice and beef cattle. In beef cattle, ultra low residual level of pDNA vaccine was only found at the injection site. According to rough estimation, consumption of muscles from the injection site represents almost an undetectable intake of pDNA (400 fg/g muscle tissue) for consumers. Residual plasmid in native state will hardly be found at measurable level following further meat processing. This study brings supportive data for animal and food safety and hence for further approval of pDNA vaccine field trials.

Immunogenicity in mice and rabbits of DNA vaccines expressing woodchuck hepatitis virus antigens

The licensed vaccine against hepatitis B virus (HBV) is an effective means to prevent infection, but is not an effective therapeutic strategy to treat established chronic infections when used alone. In an animal model of chronic HBV infection (the woodchuck experimentally infected with woodchuck hepatitis virus (WHV)), the combination of conventional vaccine and potent antiviral drugs has shown promise as a potential therapeutic intervention. This approach might be improved further through the application of newer vaccine technologies. In the present study, we evaluated electroporation (EP)-based intramuscular (i.m.) delivery of a codon-optimized DNA vaccine for the WHV surface antigen (WHsAg) in mice and rabbits. In mice, this immunization procedure compared favorably to vaccination by i.m. injection of the DNA vaccine or i.m. administration of a recombinant WHsAg-alum vaccine, exhibiting characteristics expected to be beneficial for a therapeutic vaccine strategy. These included dose efficiency, consistency, vigorous induction of antibody responses to WHsAg, as well as a Th1 bias. Following scale-up to rabbits, a species that approximates the size of the woodchuck, the EP dosing regimen was markedly more effective than conventional i.m. injection of the DNA vaccine. Taken together, these results provide the foundation for studies of EP-based DNA immunization in the woodchuck in order to further assess its potential as an immunotherapeutic approach for treatment of chronic HBV infection in humans.

Vascular growth in ischemic limbs: a review of mechanisms and possible therapeutic stimulation

Stimulation of vascular growth to treat limb ischemia is promising, and early results obtained from uncontrolled clinical trials using angiogenic agents, e.g., vascular endothelial growth factor, led to high expectations. However, negative results from recent placebo-controlled trials warrant further research. Here, current insights into mechanisms of vascular growth in the adult, in particular the role of angiogenic factors, the immune system, and bone marrow, were reviewed, together with modes of its therapeutic stimulation and results from recent clinical trials. Three concepts of vascular growth have been described to date-angiogenesis, vasculogenesis, and arteriogenesis (collateral artery growth)-which represent different aspects of an integrated process. Stimulation of arteriogenesis seems clinically most relevant and has most recently been attempted using autologous bone marrow transplantation with some beneficial results, although the mechanism of action is not completely understood. Better understanding of the highly complex molecular and cellular mechanisms of vascular growth may yet lead to meaningful clinical applications.

Non-viral gene transfection technologies for genetic engineering of stem cells

The recent rapid progress of molecular biology together with the steady progress of genome projects has given us some essential and revolutionary information about DNA and RNA to elucidate various biological phenomena at a genetic level. Under these circumstances, the technology and methodology of gene transfection have become more and more important to enhance the efficacy of gene therapy for several diseases. In addition, gene transfection is a fundamental technology indispensable to the further research development of basic biology and medicine regarding stem cells. Stem cells genetically manipulated will enhance the therapeutic efficacy of cell transplantation. In this paper, the carrier and technology of gene delivery are briefly overviewed while the applications to the basic researches of biology and medicine as well as regenerative medical therapy are introduced. A new non-viral carrier and the cell culture system are described to efficiently manipulate stem cells.

Prolonged in vivo gene silencing by electroporation-mediated plasmid delivery of small interfering RNA

For the successful application of RNA interference in vivo, it is desired to achieve (local) delivery of small interfering RNAs (siRNAs) and long-term gene silencing. Nonviral electrodelivery is suitable to obtain local and prolonged expression of transgenes. By intramuscular electrodelivery of a plasmid in which two opposing human polymerase III promoters (H1 and U6) drive the expression of siRNA constructs that form functional double-stranded siRNAs, in combination with in vivo bioluminescence imaging, we were able to knock down exogenous delivered luciferase for at least 100 days in murine calf muscles. This effect was sequence specific, because scrambled siRNA had no effect. Moreover, we were able to demonstrate in vivo reduction of endogenous TLR4 expression for at least 1 week, using a similar vector expressing an siRNA for TLR4 in the muscle. In this study, we demonstrate that in vivo suppression of both endogenous (for at least 1 week) and introduced genes (>100 days) is feasible via plasmid-driven siRNA expression after electroporation-mediated intramuscular gene transfer. With this approach the short-term effect of oligonucleotides and the drawbacks of viral gene delivery, like immunological responses, could be circumvented. Therefore, this application of RNA interference is a useful tool with which to investigate gene function and might be promising as a therapeutic tool for locally acting diseases such as restenosis or tumors.

Improvement of in vivo transfer of plasmid DNA in muscle: comparison of electroporation versus ultrasound

Plasmid-based gene delivery to muscle is a treatment strategy for many diseases with potential advantages above viral-based gene delivery methods, however, with a relative low transfection efficiency. We compared two physical methods - electroporation and ultrasound - that facilitate DNA uptake into cells. Mice (C57Bl/6) were injected intramuscular using plasmid DNA encoding an intracellular protein (p53) followed by electroporation or ultrasound. Then 48 hr after the injections the mice were sacrificed. The parameter for transfection efficiency was the area of muscle expressing the transgene. The p53 expression plasmid showed a 36-fold increase (p = 0.015) in transfection efficiency with electroporation compared to ultrasound. Compared with ultrasound, electroporation significantly improves transfection efficiency of naked plasmid DNA transfer into skeletal muscle.

Potential Use of Gene Transfer in Athletic Performance Enhancement

After only a short history of three decades from concept to practice, gene therapy has recently been shown to have potential to treat serious human diseases. Despite this success, gene therapy remains in the realm of experimental medicine, and much additional preclinical and clinical study will be necessary for proving the efficacy and safety of this approach in the treatment of diseases in humans. However, a potential complicating factor is that advances in gene transfer technology could be misused to enhance athletic performance in sports, in a practice termed "gene doping". Moreover, gene doping could be a precursor to a broader controversial agenda of human "genetic enhancement" with the potential for a significant long-term impact on society. This review addresses the possible ways in which knowledge and experience gained in gene therapy in animals and humans may be abused for enhancing sporting prowess. We provide an overview of recent progress in gene therapy, with potential application to gene doping and with the major focus on candidate performance-enhancement genes. We also discuss the current status of preclinical studies and of clinical trials that use these genes for therapeutic purposes. Current knowledge about the association between the natural "genetic make-up" of humans and their physical characteristics and performance potential is also presented. We address issues associated with the safety of gene transfer technologies in humans, especially when used outside a strictly controlled clinical setting, and the obstacles to translating gene transfer strategies from animal studies to humans. We also address the need for development and implementation of measures to prevent abuse of gene transfer technologies, and to pursue research on strategies for its detection in order to discourage this malpractice among athletes.

Optimisation of intradermal DNA electrotransfer for immunisation

The development of DNA vaccines requires appropriate delivery technologies. Electrotransfer is one of the most efficient methods of non-viral gene transfer. In the present study, intradermal DNA electrotransfer was first optimised. Strong effects of the injection method and the dose of DNA on luciferase expression were demonstrated. Pre-treatments were evaluated to enhance DNA diffusion in the skin but neither hyaluronidase injection nor iontophoresis improved efficiency of intradermal DNA electrotransfer. Then, DNA immunisation with a weakly immunogenic model antigen, luciferase, was investigated. After intradermal injection of the plasmid encoding luciferase, electrotransfer (HV 700 V/cm 100 micros, LV 200 V/cm 400 ms) was required to induce immune response. The response was Th1-shifted compared to immunisation with the luciferase recombinant protein. Finally, DNA electrotransfer in the skin, the muscle or the ear pinna was compared. Muscle DNA electrotransfer resulted in the highest luciferase expression and the best IgG response. Nevertheless electrotransfer into the skin, the muscle and the ear pinna all resulted in IFN-gamma secretion by luciferase-stimulated splenocytes suggesting that an efficient Th1 response was induced in all case.

Sine-wave current for efficient and safe in vivo gene transfer

Recently, electro-gene transfer has become a powerful tool to enhance the efficiency of gene expression in different organs and particularly in muscle, which provides efficient secretion of therapeutic proteins into the circulation. However, its toxicity, owing to the high field strengths of conventional direct current (DC) square-waves, should be taken into account and should be minimized if electroporation is to be used routinely for the treatment of human diseases. In this study, we demonstrate that efficient in vivo gene transfer could be safely achieved using pulses of alternating current sine-waves (ACSWs) with a frequency of 60 Hz. Importantly, the field strength was decreased to as low as 20 V/cm and the efficiency of muscle gene transfer increased more than tenfold and showed less toxicity than with conventional DC square-wave pulses. Using ACSW pulses to transfer human clotting factor IX (hFIX) plasmid into muscle, we observed significant phenotypic correction in mice with hemophilia B.

Nonviral gene delivery: what we know and what is next

Gene delivery using nonviral approaches has been extensively studied as a basic tool for intracellular gene transfer and gene therapy. In the past, the primary focus has been on application of physical, chemical, and biological principles to development of a safe and efficient method that delivers a transgene into target cells for appropriate expression. This review summarizes the current status of the most commonly used nonviral methods, with an emphasis on their mechanism of action for gene delivery, and their advantages and limitations for gene therapy applications. The technical aspects of each delivery system are also reviewed, with a focus on how to achieve optimal delivery efficiency. A brief discussion of future development and further improvement of the current systems is intended to stimulate new ideas and encourage rapid advancement in this new and promising field.

Electrically Assisted Ocular Gene Therapy

Electrotransfer and iontophoresis are being developed as innovative non-viral gene delivery systems for the treatment of eye diseases. These two techniques rely on the use of electric current to allow for higher transfection yield of various ocular cell types in vivo. Short pulses of relatively high-intensity electric fields are used for electrotransfer delivery, whereas the iontophoresis technique is based on the application of low voltage electric current. The basic principles of these techniques and their potential therapeutic application for diseases of the anterior and posterior segments of the eye are reviewed. Iontophoresis has been found most efficient for the delivery of small nucleic acid fragments such as antisense oligonucleotides, siRNA, or ribozymes. Electrotransfer, on the other hand, is being developed for the delivery of oligonucleotides or custom designed plasmids. The wide range of strategies already validated and the potential for targeting specific types of cells confirm the promising early observations made using electrotransfer and iontophoresis. These two nonviral delivery systems are safe and can be used efficiently for targeted gene delivery to ocular tissues in vivo. At the present, their application for the treatment of ocular human diseases is nearing its final stages of adaptation and practical implementation at the bedside.

Therapeutic protein production in vivo after electroporation-assisted intramuscular gene delivery

Gene delivery to skeletal muscles assisted by electroporation(EP) is a promising strategy for in vivo production of the therapeutic proteins. But the commonly used procedure required the application of electric pulses with voltages at above 200V/cm and durations at least 40ms, which would result in several damages in the muscle and limited surviving cells expressing transgene. We reported here an optimization study of the various electric pulse parameters to reduce toxicity while maintain transgene expression. In addition, we also found that the secreted transgene product level detected in serum samples may not correlate with the total gene expression level in muscles. Based on our data, we'd propose some less damaging electroporation parameters that may be useful for intramuscular gene delivery and therapeutic protein production.

Non-viral ocular gene therapy: potential ocular therapeutic avenues

Non-viral vectors for potential gene replacement and therapy have been developed in order to overcome the drawbacks of viral vectors. The diversity of non-viral vectors allows for a wide range of various products, flexibility of application, ease of use, low-cost of production and enhanced "genomic" safety. Using non-viral strategies, oligonucleotides (ODNs) can be delivered naked (less efficient) or entrapped in cationic lipids, polymers or peptides forming slow release delivery systems, which can be adapted according to the organ targeted and the therapy purposes. Tissue and cell internalization can be further enhanced by changing by physical or chemical means. Moreover, a specific vector can be selected according to disease course and intensity of manifestations fulfilling specific requirements such as the duration of drug release and its level along with cells and tissues specific targeting. From accumulating knowledge and experience, it appears that combination of several non-viral techniques may increase the efficacy and ensure the safety of these evolving and interesting gene therapy strategies.

Myostatin short interfering hairpin RNA gene transfer increases skeletal muscle mass

BACKGROUND

Myostatin negatively regulates skeletal muscle growth. Myostatin knockout mice exhibit muscle hypertrophy and decreased interstitial fibrosis. We investigated whether a plasmid expressing a short hairpin interfering RNA (shRNA) against myostatin and transduced using electroporation would increase local skeletal muscle mass.

METHODS

Short interfering RNAs (siRNAs) targeting myostatin were co-transfected with a myostatin-expressing plasmid into HEK293 cells and identified for myostatin silencing by Western blot. Corresponding shRNAs were cloned into plasmid shRNA expression vectors. Myostatin or a randomer negative control shRNA plasmid was injected and electroporated into the tibialis anterior or its contralateral muscle, respectively, of nine rats that were sacrificed after 2 weeks. Six other rats received a beta-galactosidase reporter plasmid and were sacrificed at 1, 2, and 4 weeks. Uptake of plasmid was examined by beta-galactosidase expression, whereas myostatin expression was determined by real-time polymerase chain reaction (PCR) and Western blotting. Muscle fiber size was determined by histochemistry. Satellite cell proliferation was determined by PAX7 immunohistochemistry. Myosin heavy chain type II (MHCII) expression was determined by Western blot.

RESULTS

beta-Galactosidase reporter plasmid was expressed at 1 and 2 weeks but diminished by 4 weeks in tibialis anterior skeletal muscle. Myostatin shRNA reduced myostatin mRNA and protein expression by 27 and 48%, respectively. Tibialis anterior weight, fiber size, and MHCII increased by 10, 34, and 38%, respectively. Satellite cell number was increased by over 2-fold.

CONCLUSIONS

This is the first demonstration that myostatin shRNA gene transfer is a potential strategy to increase muscle mass.

The effect of interleukin-10 knock-out and overexpression on neointima formation in hypercholesterolemic APOE*3-Leiden mice

OBJECTIVE

Inflammatory factors are thought to play a regulatory role in restenosis. Interleukin-10 (IL10) is an important anti-inflammatory cytokine with anti-atherogenic potentials. The aim of this study was to assess the effects of IL10 modulation on cuff-induced neointima formation in hypercholesterolemic APOE*3-Leiden mice.

METHODS

The involvement of IL10 in neointima formation was studied in a hypercholesterolemic mouse model of cuff-induced stenosis of the femoral artery by IL10 knocking-out or overexpression procedures. IL10(+/-) mice were crossbred with APOE*3-Leiden mice to generate hypercholesterolemic APOE*3-LeidenIL10(-/-) mice. To achieve IL10 overexpression in APOE*3-Leiden mice, a single intramuscular injection of a murine IL10 overexpression plasmid was performed followed by electroporation.

RESULTS

Knocking-out IL10, in hypercholesterolemic APOE*3-Leiden mice, resulted in a significant 1.9-fold increase of neointima surface as compared to APOE*3-LeidenIL10(+/+) littermates (p=0.02). Conversely, a marked 45% inhibition on cuff-induced neointima formation was obtained after IL10 overexpression (p=0.02). Electrodelivery of IL10 vector leads to detectable IL10 serum levels, with a sustained expression over the experimental period of 3 weeks. IL10 overexpression reduced plasma cholesterol levels in APOE*3-Leiden mice, whereas IL10 deficiency in these mice did not lead to altered cholesterol levels as compared to the IL10(+/+) group. Finally, IL10 overexpression stimulated endogenous IL10 mRNA expression in the spleen and reduced the transcriptional responses of several pro-inflammatory cytokines.

CONCLUSION

Here, we clearly demonstrate the role of IL10 in the development of neointima formation in hypercholesterolemic mice and the potential therapeutic effect of non-viral electrodelivery of IL10 cDNA to inhibit post-angioplasty restenosis.

Gene-Based Intramuscular Interferon-β Therapy for Experimental Autoimmune Encephalomyelitis

In contrast to serial injections of recombinant interferon-beta (IFN-beta) for long-term therapy of multiple sclerosis (MS), prolonged systemic delivery of proteins derived through in vivo gene transfer may provide a more clinically relevant alternative. Here we compare the therapeutic efficacies of electroporation (EP)-mediated intramuscular IFN-beta gene transfer with repeated alternate-day injections of recombinant IFN-beta after the onset of relapsing-remitting experimental autoimmune encephalomyelitis (EAE), an animal model widely used in MS research. We show for the first time that a single EP-mediated intramuscular administration of 20 microg of an IFN-beta-expressing plasmid provides long-term expression of interferon-inducible genes and is therapeutic in ongoing established EAE. The achieved therapeutic effects of IFN-beta gene delivery were comparable to an 8-week regimen of 10,000 IU rIFN-beta injected every other day and involved a significant inhibition of disease progression and a significant reduction of EAE relapses compared to untreated or null-vector-treated mice. Our results indicate the viability of a convenient and effective gene-based alternative for long-term IFN-beta protein therapy in MS.