Nonviral gene transfer to skeletal, smooth, and cardiac muscle in living animals

Delivery of DNA-Based Therapeutics for Treatment of Chronic Diseases

Gene therapy and its role in the medical field have evolved drastically in recent decades. Studies aim to define DNA-based medicine as well as encourage innovation and the further development of novel approaches. Gene therapy has been established as an alternative approach to treat a variety of diseases. Its range of mechanistic applicability is wide; gene therapy has the capacity to address the symptoms of disease, the body's ability to fight disease, and in some cases has the ability to cure disease, making it a more attractive intervention than some traditional approaches to treatment (i.e., medicine and surgery). Such versatility also suggests gene therapy has the potential to address a greater number of indications than conventional treatments. Many DNA-based therapies have shown promise in clinical trials, and several have been approved for use in humans. Whereas current treatment regimens for chronic disease often require frequent dosing, DNA-based therapies can produce robust and durable expression of therapeutic genes with fewer treatments. This benefit encourages the application of DNA-based gene therapy to manage chronic diseases, an area where improving efficiency of current treatments is urgent. Here, we provide an overview of two DNA-based gene therapies as well as their delivery methods: adeno associated virus (AAV)-based gene therapy and plasmid DNA (pDNA)-based gene therapy. We will focus on how these therapies have already been utilized to improve treatment of chronic disease, as well as how current literature supports the expansion of these therapies to treat additional chronic indications in the future.

Modified fibrin hydrogel for sustained delivery of RNAi lipopolyplexes in skeletal muscle

RNA interference is a promising therapeutical approach presently hindered by delivery concerns such as rapid RNA degradation and targeting of individual tissues. Injectable hydrogels are one potentially simple and direct route towards overcoming these barriers. Here we report on the utility of a combination of a mildly modified form of the clinically utilised fibrin hydrogel with Invivofectamine^® 3.0, a lipid nonviral transfection vector, for local and sustained release. PEGylation of fibrin allowed for controlled release of small interfering RNA (siRNA)-lipopolyplexes for at least 10 days and greatly increased the stability of fibrin in vitro and in vivo. A 3D cell culture model and a release study showed transfection efficacy of siRNA-lipopolyplexes was retained for a minimum of 7 days. Injection in conjunction with PEGylated-fibrinogen significantly increased retention of siRNA-lipopolyplexes in mouse skeletal muscle and enhanced knockdown of myostatin mRNA that correlated with muscle growth. Thus, the increased efficacy observed here for the combination of a lipid nanoparticle, the only type of nonviral vector approved for the clinic, with fibrin, might allow for more rapid translation of injectable hydrogel-based RNA interference.

Efficient suppression of endogenous CFTR nonsense mutations using anticodon-engineered transfer RNAs

Nonsense mutations or premature termination codons (PTCs) comprise ∼11% of all genetic lesions, which result in over 7,000 distinct genetic diseases. Due to their outsized impact on human health, considerable effort has been made to find therapies for nonsense-associated diseases. Suppressor tRNAs have long been identified as a possible therapeutic for nonsense-associated diseases; however, their ability to inhibit nonsense-mediated mRNA decay (NMD) and support significant protein translation from endogenous transcripts has not been determined in mammalian cells. Here, we investigated the ability of anticodon edited (ACE)-tRNAs to suppress cystic fibrosis (CF) causing PTCs in the cystic fibrosis transmembrane regulator (CFTR) gene in gene-edited immortalized human bronchial epithelial (16HBEge) cells. Delivery of ACE-tRNAs to 16HBEge cells harboring three common CF mutations G542XUGA-, R1162XUGA-, and W1282XUGA-CFTR PTCs significantly inhibited NMD and rescued endogenous mRNA expression. Furthermore, delivery of our highly active leucine-encoding ACE-tRNA resulted in rescue of W1282X-CFTR channel function to levels that significantly exceed the necessary CFTR channel function for therapeutic relevance. This study establishes the ACE-tRNA approach as a potential standalone therapeutic for nonsense-associated diseases due to its ability to rescue both mRNA and full-length protein expression from PTC-containing endogenous genes.

Revisiting the role of pulsed electric fields in overcoming the barriers to in vivo gene electrotransfer

Gene therapies are revolutionizing medicine by providing a way to cure hitherto incurable diseases. The scientific and technological advances have enabled the first gene therapies to become clinically approved. In addition, with the ongoing COVID-19 pandemic, we are witnessing record speeds in the development and distribution of gene-based vaccines. For gene therapy to take effect, the therapeutic nucleic acids (RNA or DNA) need to overcome several barriers before they can execute their function of producing a protein or silencing a defective or overexpressing gene. This includes the barriers of the interstitium, the cell membrane, the cytoplasmic barriers and (in case of DNA) the nuclear envelope. Gene electrotransfer (GET), i.e., transfection by means of pulsed electric fields, is a non-viral technique that can overcome these barriers in a safe and effective manner. GET has reached the clinical stage of investigations where it is currently being evaluated for its therapeutic benefits across a wide variety of indications. In this review, we formalize our current understanding of GET from a biophysical perspective and critically discuss the mechanisms by which electric field can aid in overcoming the barriers. We also identify the gaps in knowledge that are hindering optimization of GET in vivo.

Gene Therapy for Acute Respiratory Distress Syndrome

Acute respiratory distress syndrome (ARDS) is a devastating clinical syndrome that leads to acute respiratory failure and accounts for over 70,000 deaths per year in the United States alone, even prior to the COVID-19 pandemic. While its molecular details have been teased apart and its pathophysiology largely established over the past 30 years, relatively few pharmacological advances in treatment have been made based on this knowledge. Indeed, mortality remains very close to what it was 30 years ago. As an alternative to traditional pharmacological approaches, gene therapy offers a highly controlled and targeted strategy to treat the disease at the molecular level. Although there is no single gene or combination of genes responsible for ARDS, there are a number of genes that can be targeted for upregulation or downregulation that could alleviate many of the symptoms and address the underlying mechanisms of this syndrome. This review will focus on the pathophysiology of ARDS and how gene therapy has been used for prevention and treatment. Strategies for gene delivery to the lung, such as barriers encountered during gene transfer, specific classes of genes that have been targeted, and the outcomes of these approaches on ARDS pathogenesis and resolution will be discussed.

Therapeutic promise of engineered nonsense suppressor tRNAs

Nonsense mutations change an amino acid codon to a premature termination codon (PTC) generally through a single-nucleotide substitution. The generation of a PTC results in a defective truncated protein and often in severe forms of disease. Because of the exceedingly high prevalence of nonsense-associated diseases and a unifying mechanism, there has been a concerted effort to identify PTC therapeutics. Most clinical trials for PTC therapeutics have been conducted with small molecules that promote PTC read through and incorporation of a near-cognate amino acid. However, there is a need for PTC suppression agents that recode PTCs with the correct amino acid while being applicable to PTC mutations in many different genomic landscapes. With these characteristics, a single therapeutic will be able to treat several disease-causing PTCs. In this review, we will focus on the use of nonsense suppression technologies, in particular, suppressor tRNAs (sup-tRNAs), as possible therapeutics for correcting PTCs. Sup-tRNAs have many attractive qualities as possible therapeutic agents although there are knowledge gaps on their function in mammalian cells and technical hurdles that need to be overcome before their promise is realized. This article is categorized under: RNA Processing > tRNA Processing Translation > Translation Regulation.

Polymeric Delivery of Therapeutic Nucleic Acids

The advent of genome editing has transformed the therapeutic landscape for several debilitating diseases, and the clinical outlook for gene therapeutics has never been more promising. The therapeutic potential of nucleic acids has been limited by a reliance on engineered viral vectors for delivery. Chemically defined polymers can remediate technological, regulatory, and clinical challenges associated with viral modes of gene delivery. Because of their scalability, versatility, and exquisite tunability, polymers are ideal biomaterial platforms for delivering nucleic acid payloads efficiently while minimizing immune response and cellular toxicity. While polymeric gene delivery has progressed significantly in the past four decades, clinical translation of polymeric vehicles faces several formidable challenges. The aim of our Account is to illustrate diverse concepts in designing polymeric vectors towards meeting therapeutic goals of in vivo and ex vivo gene therapy. Here, we highlight several classes of polymers employed in gene delivery and summarize the recent work on understanding the contributions of chemical and architectural design parameters. We touch upon characterization methods used to visualize and understand events transpiring at the interfaces between polymer, nucleic acids, and the physiological environment. We conclude that interdisciplinary approaches and methodologies motivated by fundamental questions are key to designing high-performing polymeric vehicles for gene therapy.

Gene transfer to skeletal muscle using hydrodynamic limb vein injection: current applications, hurdles and possible optimizations

Hydrodynamic limb vein injection is an in vivo locoregional gene delivery method. It consists of administrating a large volume of solution containing nucleic acid constructs in a limb with both blood inflow and outflow temporarily blocked using a tourniquet. The fast, high pressure delivery allows the musculature of the whole limb to be reached. The skeletal muscle is a tissue of choice for a variety of gene transfer applications, including gene therapy for Duchenne muscular dystrophy or other myopathies, as well as for the production of antibodies or other proteins with broad therapeutic effects. Hydrodynamic limb vein delivery has been evaluated with success in a large range of animal models. It has also proven to be safe and well-tolerated in muscular dystrophy patients, thus supporting its translation to the clinic. However, some possible limitations may occur at different steps of the delivery process. Here, we have highlighted the interests, bottlenecks and potential improvements that could further optimize non-viral gene transfer following hydrodynamic limb vein injection.

MiR-34c represses muscle development by forming a regulatory loop with Notch1

Since pork accounts for about 40% of global meat consumption, the pig is an important economic animal for meat production. Pig is also a useful medical model for humans due to its similarity in size and physiology. Understanding the mechanism of muscle development has great implication for animal breeding and human health. Previous studies showed porcine muscle satellite cells (PSCs) are important for postnatal skeletal muscle growth, and Notch1 signaling pathway and miRNAs regulate the skeletal muscle development. Notch1 signal pathway regulates the transcription of certain types of miRNAs which further affects target gene expression. However, the specific relationship between Notch1 and miRNAs during muscle development has not been established. We found miR-34c is decreased in PSCs overexpressed N1ICD. Through the overexpression and inhibition of mi-34c, we demonstrated that miR-34c inhibits PSCs proliferation and promotes PSCs differentiation. Using dual-luciferase reporter assay and Chromatin immunoprecipitation, we demonstrate there is a reciprocal regulatory loop between Notch1 and miR-34c. Furthermore, injection of miR-34c lentivirus into mice caused repression of gastrocnemius muscle development. In summary, our data revealed that miR-34c can form a regulatory loop with Notch1 to repress muscle development, and this result expands our understanding of muscle development mechanism.

Human Mesenchymal Stem Cell Delivery System Modulates Ischemic Cardiac Remodeling With an Increase of Coronary Artery Blood Flow

Ways for extending the longevity of stem cells are imperative to attain diverse expected therapeutic effects. Here, we constructed a three-dimentional (3D) scaffold system for human mesenchymal stem cell (hMSC) delivery. Intramyocardial injections of porous PEI1.8k blended with poly(lactic-co-glycolic acid) (PLGA) (PLGA/PEI1.8k) (PPP) microparticles by physical electrostatic conjugation and structural entrapment of hMSCs demonstrated enhanced functional and geometric improvements on post-infarct cardiac remodeling in rats. In the hMSC-loaded PPP delivery, increases of coronary artery blood flow rate and in vivo engraftment rate as well as time-dependent functional, geometric, and pathologic findings reversing post-infarct cardiac remodeling account for improved left ventricular (LV) systolic function up to the level of sham thoracotomy group. This study expands our understanding by proving that increase of coronary artery blood flow augmented functional recovery of hMSC-loaded PPP delivery system after myocardial infarction (MI).

The Feasibility of a Smart Surgical Probe for Verification of IRE Treatments Using Electrical Impedance Spectroscopy

SIGNIFICANCE

Irreversible electroporation (IRE) is gaining popularity as a focal ablation modality for the treatment of unresectable tumors. One clinical limitation of IRE is the absence of methods for real-time treatment evaluation, namely actively monitoring the dimensions of the induced lesion. This information is critical to ensure a complete treatment and minimize collateral damage to the surrounding healthy tissue.

GOAL

In this study, we are taking advantage of the biophysical properties of living tissues to address this critical demand.

METHODS

Using advanced microfabrication techniques, we have developed an electrical impedance microsensor to collect impedance data along the length of a bipolar IRE probe for treatment verification. For probe characterization and interpretation of the readings, we used potato tuber, which is a suitable platform for IRE experiments without having the complexities of in vivo or ex vivo models. We used the impedance spectra, along with an electrical model of the tissue, to obtain critical parameters such as the conductivity of the tissue before, during, and after completion of treatment. To validate our results, we used a finite element model to simulate the electric field distribution during treatments in each potato.

RESULTS

It is shown that electrical impedance spectroscopy could be used as a technique for treatment verification, and when combined with appropriate FEM modeling can determine the lesion dimensions.

CONCLUSIONS

This technique has the potential to be readily translated for use with other ablation modalities already being used in clinical settings for the treatment of malignancies.

Pluronic L64-mediated stable HIF-1α expression in muscle for therapeutic angiogenesis in mouse hindlimb ischemia

Intramuscular injection of plasmid DNA (pDNA) to express a therapeutic protein is a promising method for the treatment of many diseases. However, the therapeutic applications are usually hindered by gene delivery efficiency and expression level. In this study, critical factors in a pDNA-based gene therapy system, such as gene delivery materials, a therapeutic gene, and its regulatory elements, were optimized to establish an integrated system for the treatment of mouse hindlimb ischemia. The results showed that Pluronic^® L64 (L64) was an efficient and safe material for gene delivery into mouse skeletal muscle. It also showed intrinsic ability to promote in vivo angiogenesis in a concentration-dependent manner, which might be through the activation of nuclear factor kappa-light-chain-enhancer of activated B cell (NF-κB)-regulated angiogenic factors. The combination of 0.1% L64 with a hybrid gene promoter (pSC) increased the gene expression level, elongated the gene expression duration, and enhanced the number of transfected muscle fibers. In mice ischemic limbs, a gene medicine (pSC-HIF1α^tri/L64) composed of L64 and pSC-based expression plasmid encoding hypoxia-inducible factor 1-alpha triple mutant (HIF-1α^tri), improved the expression of stable HIF-1α, and in turn, the expression of multiple angiogenic factors. As a result, the ischemic limbs showed accelerated function recovery, reduced foot necrosis, faster blood reperfusion, and higher capillary density. These results indicated that the pSC-HIF1α^tri/L64 combination presented a potential and convenient venue for the treatment of peripheral vascular diseases, especially critical limb ischemia.

Human erythropoietin gene delivery for cardiac remodeling of myocardial infarction in rats

Considerable efforts have been made to exploit cardioprotective drugs and gene delivery systems for myocardial infarction (MI). The promising cardioprotective effects of recombinant human erythropoietin (rHuEPO) protein in animal experiments have not been consistently reproduced in clinical human trials of acute MI; however, the mechanisms underlying the inconsistent discrepancies are not yet fully understood. We hypothesized that the plasmid human erythropoietin gene (phEPO) delivered by our bioreducible polymer might produce cardioprotective effects on post-infarct cardiac remodeling. We demonstrated that intramyocardial delivery of phEPO by an arginine-grafted poly(disulfide amine) (ABP) polymer in infarcted rats preserves cardiac geometry and systolic function. The reduced infarct size of phEPO/ABP delivery was followed by decrease in fibrosis, protection from cardiomyocyte loss, and down-regulation of apoptotic activity. In addition, the increased angiogenesis and decreased myofibroblast density in the border zone of the infarct support the beneficial effects of phEPO/ABP administration. Furthermore, phEPO/ABP delivery induced prominent suppression on Ang II and TGF-β activity in all subdivisions of cardiac tissues except for the central zone of infarct. These results of phEPO gene therapy delivered by a bioreducible ABP polymer provide insight into the lack of phEPO gene therapy translation in the treatment of acute MI to human trials.

Delivery of RNAi-Based Oligonucleotides by Electropermeabilization

For more than a decade, understanding of RNA interference (RNAi) has been a growing field of interest. The potent gene silencing ability that small oligonucleotides have offers new perspectives for cancer therapeutics. One of the present limits is that many biological barriers exist for their efficient delivery into target cells or tissues. Electropermeabilization (EP) is one of the physical methods successfully used to transfer small oligonucleotides into cells or tissues. EP consists in the direct application of calibrated electric pulses to cells or tissues that transiently permeabilize the plasma membranes, allowing efficient in vitro and in vivo cytoplasmic delivery of exogenous molecules. The present review reports on the type of therapeutic RNAi-based oligonucleotides that can be electrotransferred, the mechanism(s) of their electrotransfer and the technical settings for pre-clinical purposes.

Hyperactive self-inactivating piggyBac for transposase-enhanced pronuclear microinjection transgenesis

We have developed a unique method for mouse transgenesis. The transposase-enhanced pronuclear microinjection (PNI) technique described herein uses the hyperactive piggyBac transposase to insert a large transgene into the mouse genome. This procedure increased transgene integration efficiency by fivefold compared with conventional PNI or intracytoplasmic sperm injection-mediated transgenesis. Our data indicate that the transposase-enhanced PNI technique additionally requires fewer embryos to be microinjected than traditional methods to obtain transgenic animals. This transposase-mediated approach is also very efficient for single-cell embryo cytoplasmic injections, offering an easy-to-implement transgenesis method to the scientific community.

Sustained, high transgene expression in liver with plasmid vectors using optimized promoter-enhancer combinations

BACKGROUND

Plasmid-based gene therapy approaches often lack long-term transgene expression in vivo as a result of silencing or loss of the vector. One way to overcome these limitations is to combine nonsilenced promoters with strong enhancers.

METHODS

In the present study, we combine murine or human cytomegalovirus (CMV)-derived enhancer elements with the human elongation factor 1α (EF1α) promoter in a plasmid backbone devoid of potentially immunostimulating cytosine-guanine repeat sequences. Luciferase transgene activity was monitored in mouse liver after hydrodynamic plasmid delivery.

RESULTS

Luciferase activity of a CMV-promoter driven plasmid rapidly declined within days, whereas the activity of the EF1α driven plasmid remained high for 2 weeks (murine enhancer) and detectable for > 80 days (human enhancer). Expression levels clearly correlated with higher plasmid copy number found in the liver at 2 months after gene delivery. Furthermore, we developed a novel synthetic CMV-EF1α hybrid promoter (SCEP) combining the high activity of CMV and sustained activity of EF1α promoter. The SCEP led to a constitutive three-fold increase in expression levels compared to the EF1α promoter in vivo.

CONCLUSIONS

This novel combination of enhancer and promoter element with optimized plasmid backbones will pave the way for more efficient nonviral approaches in gene therapy.

Ultrasound- and liposome microbubble-mediated targeted gene transfer to cardiomyocytes in vivo accompanied by polyethylenimine

OBJECTIVES

Gene transfer to cardiomyocytes in vivo has received much research attention in the last decade but remains a substantial hurdle. Gene transfer using ultrasound-targeted microbubble destruction is a promising tool for gene therapy. Little data have shown the feasibility and optimization of this method for primary myocardial disease. In this study, we sought to determine the feasibility and efficiency of in vivo gene transfer to the myocardium mediated by ultrasound-targeted microbubble destruction accompanied by polyethylenimine.

METHODS

Three plasmids (luciferase reporter, red fluorescent protein reporter, and enhanced green fluorescent protein reporter) were used in this study. The ultrasound parameters were also optimized. A solution containing phosphate-buffered saline, a plasmid, plasmid complex, or polyethylenimine/plasmid, and liposome microbubbles was injected via a tail vein with (study) or without (control) transthoracic ultrasound irradiation. The efficiency of reporter gene transfer was determined by detection of luciferase activity or microscopy, and histologic investigations of the tissue specimens were performed.

RESULTS

Ultrasound-targeted microbubble destruction significantly increased luciferase activity in vivo compared to plasmids and microbubbles alone (P < .001). More importantly, the increase in transgene expression was significantly related to ultrasound-targeted microbubble destruction in the presence of polyethylenimine (P < .001). In addition, fluorescein expression was present in all sections that received ultrasound-targeted microbubble destruction. The fluorescent reporter genes and luciferase plasmid all had similar results. Regardless of ultrasound exposure, expression in other organs was close to a background level except for the liver and lung. Hematoxylin-eosin staining showed no notable myocardial injury or death in control and treated mice.

CONCLUSIONS

An atraumatic targeted gene delivery technique based on ultrasound-targeted microbubble destruction and polyethylenimine has been developed to transfect cardiomyocytes in vivo. If a suitable target gene is added, the novel technique could be highly effective in many kinds of heart disease.

Targeted nonviral gene-based inhibition of Gα(i/o)-mediated vagal signaling in the posterior left atrium decreases vagal-induced atrial fibrillation

BACKGROUND

Pharmacologic and ablative therapies for atrial fibrillation (AF) have suboptimal efficacy. Newer gene-based approaches that target specific mechanisms underlying AF are likely to be more efficacious in treating AF. Parasympathetic signaling appears to be an important contributor to AF substrate.

OBJECTIVE

The purpose of this study was to develop a nonviral gene-based strategy to selectively inhibit vagal signaling in the left atrium and thereby suppress vagal-induced AF.

METHODS

In eight dogs, plasmid DNA vectors (minigenes) expressing Gα(i) C-terminal peptide (Gα(i)ctp) was injected in the posterior left atrium either alone or in combination with minigene expressing Gα(o)ctp, followed by electroporation. In five control dogs, minigene expressing scrambled peptide (Gα(R)ctp) was injected. Vagal- and carbachol-induced left atrial effective refractory periods (ERPs), AF inducibility, and Gα(i/o)ctp expression were assessed 3 days following minigene delivery.

RESULTS

Vagal stimulation- and carbachol-induced effective refractory period shortening and AF inducibility were significantly attenuated in atria receiving a Gα(i2)ctp-expressing minigene and were nearly eliminated in atria receiving both Gα(i2)ctp- and Gα(o1)ctp-expressing minigenes.

CONCLUSION

Inhibition of both G(i) and G(o) proteins is necessary to abrogate vagal-induced AF in the left atrium and can be achieved via constitutive expression of Gα(i/o)ctps expressed by nonviral plasmid vectors delivered to the posterior left atrium.

Non-viral genetic transfection of rat Schwann cells with FuGENE HD© lipofection and AMAXA© nucleofection is feasible but impairs cell viability

Purpose:

To determine transfection efficiency of FuGENE HD© lipofection and AMAXA© nucleofection on rat Schwann cells (SC).

Methods:

The ischiadic and median nerves of 6-8 week old Lewis rats were cultured in modified melanocyte-growth medium. SCs were genetically transfected with green fluorescent protein (GFP) as reporter gene using FuGENE HD© lipofection and AMAXA© nucleofection. Transfection rates were determined by visualization of GFP fluorescence under fluorescence microscopy and cell counting. Transfected cell to non-transfected cell relation was determined.

Results:

Purity of Schwann cell culture was 88% as determined by immunohistologic staining. Transfection rate of FuGENE HD© lipofection was 2%, transfection rate of AMAXA© nucleofection was 10%. With both methods, Schwann cells showed pronounced aggregation behavior which made them unfeasible for further cultivation. Settling of Schwann cells on laminin and poly-l-ornithine coated plates was compromised by either method.

Conclusion:

Non-viral transfection of rat SC with FuGENE HD© lipofection and AMAXA© nucleofection is basically possible with a higher transfection rate for nucleofection than for lipofection. As cell viability is compromised by either method however, viral transfection is to be considered if higher efficiency is required.

Microribonucleic acids for prevention of plaque rupture and in-stent restenosis: "a finger in the dam"

Vascular smooth muscle cells (VSMCs), which make up the arterial medial layer, possess a phenotype switching capability. This modulation of VSMCs is important in the development of atherosclerotic vascular disease. It has been recognized that VSMCs may also have a stabilizing role in advanced atherosclerotic plaques. Moreover, reduction of the proliferative capacity of these cells may be of benefit in reducing neointimal hyperplasia following therapeutic percutaneous intervention. The biology of microribonucleic acids (miRNAs) and their ability to modify smooth muscle biology has recently emerged in a number of investigations. These studies elucidated the key role of miRNAs, miR-143 and miR-145, in particular, in the regulation of SMC homeostasis in vitro, in murine models of targeted gene deletion, and also in human vascular pathology. This review places this burgeoning knowledge within the wider context of atherosclerosis and restenosis and explores the therapeutic potential of miRNAs to change the fate of VSMCs within the plaque.

Enhanced stability and in vitro bioactivity of surfactant-loaded liposomes containing Asiatic Pennywort extract

The objective of this work has been the microencapsulation of Asiatic Pennywort (AP) extract with lecithin from soybean. The effect of various quantities of non-ionic surfactant (Montanov82) on liposomes upon physicochemical characteristics as well as their in vitro bio-activities was investigated. An addition of surfactant resulted in a decrease in particle size and an increase in percentage AP entrapment efficiency of liposomes. The surfactant-loaded liposomes demonstrated higher stability than surfactant-free liposomes where higher percentage AP remaining of liposomes can be achieved depending on surfactant concentration. No significant difference was found on AP release profiles among varied surfactant concentrations, although a presence of surfactant resulted in prolonged AP release rate. Liposomal AP with 20% w/w surfactant or higher demonstrated low cytotoxicity, a stronger anti-oxidation effect and collagen production on dermal fibroblast cells when compared with free AP and surfactant-free liposomes, possibly due to better cell internalization and less AP degradation in cells.

Optimization of Gene Transfection in Murine Myeloma Cell Lines using Different Transfection Reagents

Purification and isolation of cellular target proteins for monoclonal antibody (MAb) production is a difficult and time-consuming process. Immunization of mice with murine cell lines stably transfected with genes coding for xenogenic target molecules is an alternative method for mouse immunization and MAb production. Here we present data on transfection efficiency of some commercial reagents used for transfection of murine myeloma cell lines. Little is known about transfectability of murine myeloma cell lines by different transfection reagents. Mouse myeloma cell lines (SP2/0, NS0, NS1, Ag8, and P3U1) were transfected with pEGFP-N1 vector using Lipofectamine 2000, jetPEI and LyoVec commercial transfection reagents in different combinations. The transfection permissible HEK293-FT cell line was used as a control in transfection procedure. Transfected cells, expressing the Enhanced Green Fluorescent Protein (EGFP), were analyzed by flow cytometry 48 hrs post transfection. Our results showed transfection efficiency of 71%, 57% and 22% for HEK293-FT, 5.5%, 3.4% and 1% for SP2/0, 55.7%, 21.1% and 9.3% for NS0, 8.2%, 6% and 5.5% for NS1, 22%, 49.2% and 5.5% for Ag8 and 6.3%, 21.5% and 4.6% for P3U1 cell lines after transfection with Lipofectamine 2000, jetPEI and LyoVec reagents, respectively. Our data indicate that NS0 and Ag8 are efficiently transfected by Lipofectamine 2000 and jetPEI reagents. Finally, we propose Ag8 and NS0 cell lines as suitable host cells for efficient expression of target genes which can be used for mouse immunization and MAb production.

Electroporation-mediated delivery of a naked DNA plasmid expressing VEGF to the porcine heart enhances protein expression

Gene therapy is an attractive method for the treatment of cardiovascular disease. However, using current strategies, induction of gene expression at therapeutic levels is often inefficient. In this study, we show a novel electroporation (EP) method to enhance the delivery of a plasmid expressing an angiogenic growth factor (vascular endothelial growth factor, VEGF), which is a molecule previously documented to stimulate revascularization in coronary artery disease. DNA expression plasmids were delivered in vivo to the porcine heart with or without coadministered EP to determine the potential effect of electrically mediated delivery. The results showed that plasmid delivery through EP significantly increased cardiac expression of VEGF compared with injection of plasmid alone. This is the first report showing successful intracardiac delivery, through in vivo EP, of a protein expressing plasmid in a large animal.

Gene electrotransfer: from biophysical mechanisms to in vivo applications : Part 2 - In vivo developments and present clinical applications

Gene electrotransfer can be obtained not just on single cells in diluted suspension. For more than 10 years, this is a quasi routine strategy in tissue on the living animal and a few clinical trials have now been approved. New problems have been brought by the close contacts of cells in tissue both on the local field distribution and on the access of DNA to target cells. They need to be solved to provide a further improvement in the efficacy and safety of protein expression. There is a competition between gene transfer and cell destruction. Nevertheless, present results are indicative that electrotransfer is a promising approach for gene therapy. High level and long-lived expression of proteins can be obtained in muscles. This is used for a successful method of electrovaccination.

Variability of the minimal transmembrane voltage resulting in detectable membrane electroporation

We present a study of the variability of the minimal transmembrane voltage resulting in detectable electroporation of the plasma membrane of spherical and irregularly shaped CHO cells (we denote this voltage by ITVc). Electroporation was detected by monitoring the influx of Ca(2+), and the transmembrane voltage was computed on a 3D finite-elements model of each cell constructed from its cross-section images. We found that ITVc was highly variable, particularly in irregularly shaped cells, where it ranged from 512-1028 mV. We show that this range is much too large to be an artifact due to numerical errors and experimental inaccuracies, implying that for cells of the same type and exposed to the same number of pulses with the same duration, the value of ITVc can differ considerably from one cell to another. We also observed that larger cells are in many cases characterized by a higher ITVc than a smaller one. This is in qualitative agreement with the reports that higher membrane curvature facilitates electroporation, but quantitative considerations suggest that the observed variability of ITVc cannot be attributed entirely to the differences in membrane curvature.

Hypoxia-inducible factor induces local thyroid hormone inactivation during hypoxic-ischemic disease in rats

Thyroid hormone is a critical determinant of cellular metabolism and differentiation. Precise tissue-specific regulation of the active ligand 3,5,3'-triiodothyronine (T3) is achieved by the sequential removal of iodine groups from the thyroid hormone molecule, with type 3 deiodinase (D3) comprising the major inactivating pathway that terminates the action of T3 and prevents activation of the prohormone thyroxine. Using cells endogenously expressing D3, we found that hypoxia induced expression of the D3 gene DIO3 by a hypoxia-inducible factor-dependent (HIF-dependent) pathway. D3 activity and mRNA were increased both by hypoxia and by hypoxia mimetics that increase HIF-1. Using ChIP, we found that HIF-1alpha interacted specifically with the DIO3 promoter, indicating that DIO3 may be a direct transcriptional target of HIF-1. Endogenous D3 activity decreased T3-dependent oxygen consumption in both neuronal and hepatocyte cell lines, suggesting that hypoxia-induced D3 may reduce metabolic rate in hypoxic tissues. Using a rat model of cardiac failure due to RV hypertrophy, we found that HIF-1alpha and D3 proteins were induced specifically in the hypertrophic myocardium of the RV, creating an anatomically specific reduction in local T3 content and action. These results suggest a mechanism of metabolic regulation during hypoxic-ischemic injury in which HIF-1 reduces local thyroid hormone signaling through induction of D3.

Nucleofection is a highly effective gene transfer technique for human melanoma cell lines

Despite the increasing use of gene transfer strategies in the study of cellular and molecular biology, melanoma cells have remained difficult to transfect in a safe, efficient, and reproducible manner. In the present study, we report the successful use of nucleofector technology to transfect human melanoma cell lines. This technology uses an empirically derived combination of cell line-specific solutions and nucleofector programmes to electroporate nucleic acid substrates directly into the cell nucleus. Using a colorimetric beta-galactosidase assay, we optimized nucleofection parameters for 13 melanoma cell lines, leading to maximum transfection efficiency and cell survival. The combinations of cell solutions NHEM or T and nucleofector programmes A-24 or U-20 produced the best results. We compared nucleofection with two commercially available lipid-based gene transfer systems, effectene and lipofectamine 2000 using a green fluorescent protein reporter vector. Nucleofection demonstrated a 3- to 40-fold improvement in transfection efficiency when compared with the lipid-based counterparts. Nucleofection was also superior in transfecting small-interfering RNA (siRNA) as determined by Western blot analysis. Lastly, we applied nucleofection to the simultaneous transfection of a p53-dependent luciferase plasmid and p53-siRNA. Experiments using dual transfection showed knockdown of p53 expression and silencing of the reporter plasmid. In conclusion, nucleofection is highly effective for the transfer of nucleic acid substrates, singly or in combination, into human melanoma cell lines.

Effect of electroporation on cardiac electrophysiology

Defibrillation shocks are commonly used to terminate life-threatening arrhythmias. According to the excitation theory of defibrillation, such shocks are aimed at depolarizing the membranes of most cardiac cells, resulting in resynchronization of electrical activity in the heart. If shock-induced transmembrane potentials are large enough, they can cause transient tissue damage due to electroporation. In this review, evidence is presented that electroporation of the heart tissue can occur during clinically relevant intensities of the external electrical field and that electroporation can affect the outcome of defibrillation therapy, being both pro- and antiarrhythmic.Here, we present experimental evidence for electroporation in cardiac tissue, which occurs above a threshold of 25 V/cm as evident from propidium iodide uptake, transient diastolic depolarization, and reductions of action potential amplitude and its derivative. These electrophysiological changes can induce tachyarrhythmia, due to conduction block and possibly triggered activity; however, our findings provide the foundation for future design of effective methods to deliver genes and drugs to cardiac tissues, while avoiding possible side effects such as arrhythmia and mechanical stunning.

Regulating Myoblast Phenotype Through Controlled Gel Stiffness and Degradation

Mechanical stiffness and degradability are important material parameters in tissue engineering. The aim of this study was to address the hypothesis that these variables regulate the function of myoblasts cultured in 2-D and 3-D microenvironments. Development of cell-interactive alginate gels with tunable degradation rates and mechanical stiffness was established by a combination of partial oxidation and bimodal molecular weight distribution. Higher gel mechanical properties (13 to 45 kPa) increased myoblast adhesion, proliferation, and differentiation in a 2-D cell culture model. Primary mouse myoblasts were more highly responsive to this cue than the C2C12 myoblast cell line. Myoblasts were then encapsulated in gels varying in degradation rate to simultaneously investigate the effect of degradation and subsequent reduction of mechanical properties on cells in a 3-D environment. C2C12 cells in more rapidly degrading gels exhibited lower proliferation, as they exited the cell cycle to differentiate, compared to those in nondegradable gels. In contrast, mouse primary myoblasts illustrated significantly higher proliferation in degradable gels than in nondegradable gels, and exhibited minimal differentiation in either type of gel. Altogether, these studies suggest that a critical balance between material degradation rate and mechanical properties may be required to regulate formation of engineered skeletal muscle tissue, and that results obtained with the C2C12 cell line may not be predictive of the response of primary myoblasts to environmental cues. The principles delineated in these studies may be useful to tailor smart biomaterials that can be applied to many other polymeric systems and tissue types.

Electroporation-mediated gene transfer of the Na+,K+ -ATPase rescues endotoxin-induced lung injury

RATIONALE

Acute lung injury and acute respiratory distress syndrome are common clinical syndromes resulting largely from the accumulation of and inability to clear pulmonary edema, due to injury to the alveolar epithelium. Gene therapy may represent an important alternative for the treatment and prevention of these diseases by restoring alveolar epithelial function. We have recently developed an electroporation strategy to transfer genes to the lungs of mice, with high efficiency and low inflammation.

OBJECTIVES

We asked whether electroporation-mediated transfer of genes encoding subunits of the Na+,K+ -ATPase could protect from LPS-induced lung injury or be used to treat already injured lungs by up-regulating mechanisms of pulmonary edema clearance.

METHODS

Plasmids were delivered to the lungs of mice using transthoracic electroporation. Lung injury was induced by intratracheal administration of LPS (4 mg/kg body weight). Biochemical, cellular, and physiologic measurements were taken to assess gene transfer and lung injury.

MEASUREMENTS AND MAIN RESULTS

Improvements in wet-to-dry ratios, pulmonary effusions, bronchoalveolar lavage protein levels and cellularity, alveolar fluid clearance, and respiratory mechanics were seen after delivery of plasmids expressing Na+,K+ -ATPase subunits, but not control plasmids, in LPS-injured lungs. Delivery of plasmids expressing Na+,K+ -ATPase subunits both protected from subsequent lung injury and partially reversed existing lung injury by these measures.

CONCLUSIONS

These results demonstrate that electroporation can be used effectively in healthy and injured lungs to facilitate gene delivery and expression. To our knowledge, this is the first successful use of gene delivery to treat existing lung injury, and may have future clinical potential.

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.

Sleeping beauty transposon-mediated nonviral gene therapy

Safe and effective delivery of genetic material to mammalian tissues would significantly expand the therapeutic possibilities for a large number of medical conditions. Unfortunately, the promise of gene therapy has been hampered by technical challenges, the induction of immune responses, and inadequate expression over time. Despite these setbacks, progress continues to be made and the anticipated benefits may come to fruition for certain disorders. In terms of delivery, nonviral vector systems are particularly attractive as they are simple to produce, can be stored for long periods of time, and induce no specific immune responses. A significant drawback to nonviral systems has been the lack of persistent expression, as plasmids are lost or degraded when delivered to living tissues. The recent application of integrating transposons to nonviral gene delivery has significantly helped to overcome this obstacle, because it allows for genomic integration and long-term expression. Recent advances in transposon-based vector systems hold promise as new technologies that may unlock the potential of gene therapy; however, technical and safety issues still need refinement.

Intracellular trafficking of plasmids for gene therapy: mechanisms of cytoplasmic movement and nuclear import

Under physiologically relevant conditions, the levels of non-viral gene transfer are low at best. The reason for this is that many barriers exist for the efficient transfer of genes to cells, even before any gene expression can occur. While many transfection strategies focus on DNA condensation and overcoming the plasma membrane, events associated with the intracellular trafficking of the DNA complexes have not been as extensively studied. Once internalized, plasmids must travel potentially long distances through the cytoplasm to reach their next barrier, the nuclear envelope. This review summarizes the current progress on the cytoplasmic trafficking and nuclear transport of plasmids used for gene therapy applications. Both of these processes utilize specific and defined mechanisms to facilitate movement of DNA complexes through the cell. The continued elucidation and exploitation of these mechanisms will lead to improved strategies for transfection and successful gene therapy.

Plasmid-based gene therapy of diabetes mellitus

Type I diabetes mellitus (T1D) is due to a loss of immune tolerance to islet antigen and thus, there is intense interest in developing therapies that can re-establish it. Tolerance is maintained by complex mechanisms that include inhibitory molecules and several types of regulatory T cells (Tr). A major historical question is whether gene therapy can be employed to generate Tr cells. This review shows that gene transfer of immunoregulatory molecules can prevent T1D and other autoimmune diseases. In our studies, non-viral gene transfer is enhanced by in vivo electroporation (EP). This technique can be used to perform DNA vaccination against islet cell antigens and when combined with appropriate immune ligands results in the generation of Tr cells and protection against T1D. In vivo EP can also be applied for non-immune therapy of diabetes. It can be used to deliver protein drugs such as glucagon-like peptide 1 (GLP-1), leptin or transforming growth factor beta (TGF-beta). These act in T1D or type II diabetes (T2D) by restoring glucose homeostasis, promoting islet cell survival and growth or improving wound healing and other complications. Furthermore, we show that in large animals EP can deliver peptide hormones, such as growth hormone releasing hormone (GHRH). We conclude that the non-viral gene therapy and EP represent a safe and efficacious approach with clinical potential.

Gene therapy with anabolic growth factors to prevent muscle atrophy

PURPOSE OF REVIEW

Many situations cause muscle atrophy. When severe, muscle atrophy is associated with an increase in morbidity and mortality. This loss of muscle mass is thought to be due to an imbalance between catabolic and anabolic pathways, resulting in an increase of muscle protein proteolysis and in a decrease in protein synthesis. Changes in muscle levels of muscle growth factors are thought to play a major role in this imbalance. Despite recent better understanding of the metabolic and molecular derangements leading to muscle wasting, therapy of muscle atrophy still has a poor success rate.

RECENT FINDINGS

The recent demonstration that changes in local growth factors, such as insulin-like growth factor-I and myostatin, occur during muscle atrophy has stimulated research interest to prevent muscle mass loss by delivering these growth factors or their inhibitors into the muscle. During the last few years, several advances in the field of muscle gene transfer, using electroporation or recombinant adeno-associated viral vectors, have opened novel therapeutic ways to deliver growth factors able to counteract the loss of muscle mass.

SUMMARY

Preventing decrease of insulin-like growth factor-I muscle, or inhibiting myostatin action by local genes over-expression, may provide a clinically relevant avenue for the preservation, attenuation or reversal of disease-related muscle loss.

Fluorescent labeling of renal cells in vivo

In vivo fluorescence imaging, using confocal or multiphoton microscopes, provides a powerful method to analyze kidney function in experimental animals. In this review, the preparation used for physiological studies in rats is described. A variety of fluorescent probes are available to study glomerular permeability, renal blood flow, peritubular capillary permeability, cell ion concentrations, tubule transport properties, and the functional status of renal cells. We have recently used micropuncture techniques and an adenovirus vector to accomplish gene transfer into kidney tubule and endothelial cells; this new methodology will allow the dynamic study of fluorescently-labeled proteins. Two examples of the use of two-photon fluorescence microscopy to study renal pathophysiology, namely polycystic kidney disease and renal ischemia, are presented. Software is available to quantify data collected from in vivo imaging experiments and to construct 3-dimensional images of renal structures. Two-photon or confocal microscopy offers many opportunities for a better understanding of kidney function in health and disease.