Needleless in vivo gene transfer into muscles by jet injection in combination with electroporation

Degradation study on molecules released from laser-based jet injector

Development of needle-free methods to administer injectable therapeutics has been researched for a few decades. We focused our attention on a laser-based jet injection technique where the liquid-jet actuation mechanism is based on optical cavitation. This study investigates the potential damage to therapeutic molecules which are exposed to nanosecond laser pulses in the configuration of a compact laser-based jet injection device. Implementation of a pulsed laser source at 1574 nm wavelength allowed us to generate jets from pure water solutions and circumvent the need to reformulate therapeutics with absorbing dyes. We performed H1-NMR analysis on exposed samples of Lidocaine and δ-Aminolevulinic acid. We made several tests with linear and plasmid DNA to assess the structural integrity and functional potency after ejection with our device. The tests showed no significant degradation or detectable side products, which is promising for further development and eventually clinical applications.

Title: Gene transfer by pyro-drive jet injector is a novel therapeutic approach for muscle diseases

The angiogenic gene therapy is an attractive approach for the treatment of ischemic muscle diseases, including peripheral arterial disease and ischemic heart diseases. Although a variety of gene transfer methods have been developed, the efficiency of gene transfer is still limited. We have been developing the needleless high-energy bioinjector device, Pyro-drive Jet Injector (PJI), based on pyrotechnics using a combination of ignition powder and gunpowder, however, the utility of PJI in gene transfer into muscle tissues remains unclear. pcDNA3.1 plasmid containing Flag was injected to the thigh muscles of C57BL/6J mice using PJI or needle, as a control. Histological analysis demonstrated that the protein expression of Flag was observed in a wider range in PJI group than in needle group. To assess the validity of PJI for gene therapy, pcDNA3.1-human fibroblast growth factor 2 (FGF2), which has angiogenic activity and tissue protective properties, was injected into the ischemic thigh muscles with PJI or needle. ELISA assay revealed that the protein expression of FGF2 was increased in the thigh muscle tissues by PJI-mediated gene delivery. Significantly, histological analyses revealed that muscle fiber cross-sectional area and the number of endothelial marker CD31 (+) cells was increased in ischemic hind-limb tissues of the PJI-FGF2 group but not in those of needle-FGF2 group. To expand the applicability of the PJI-mediated gene transfer, pcDNA3.1-venus plasmid was injected into murine hearts with PJI or needle. PJI method was successful in gene transfer into murine hearts, especially into cardiomyocytes, with high efficiency when compared to needle method. Collectively, the non-needle, non-liposomal and non-viral gene transfer by PJI could be a novel therapeutic approach for muscle diseases.

Repetitive regime of highly focused liquid microjets for needle-free injection

Fast liquid jets are investigated for use as a needle-free drug delivery system into an elastic tissue such as skin. Using smaller jet diameters in a repetitive regime can mitigate bruising and pain associated with current injectors. In this study, we aim to unravel the potential of the method to deliver liquids into biological tissues having higher elasticity than healthy skin (i.e >60 kPa). To address this challenge, we have implemented a laser-based jetting system capable of generating supersonic liquid microjets in a repetitive regime. We provide insights on the penetration of microjets into hydrogel samples with elastic modulus ranging from 16 kPa to 0.5 MPa. The unprecedented speeds of injection (>680 m/s) together with a newly introduced repetitive regime opens possibilities for usage in needle-free drug administration into materials with elasticity covering the wide spectrum of biological soft tissues like blood vessels, all skin layers, scarred or dried skin or tumors.

A Needleless Liquid Jet Injection Delivery Approach for Cardiac Gene Therapy

Fundamentally, cardiac gene therapy clinical trials have demonstrated that route efficiency is paramount in achieving maximum myocardial expression within safety limits. Gene transfer phenomena are largely influenced by physical transport principles (i.e., pressure, residence time, dispersion trafficking, mechanical resistance) that are independent of therapeutic characteristics. An alternative to intracoronary infusion methods, in an effort to improve efficiency in terms of cardiac specificity, is direct myocardial delivery via surgical injection. Direct injection methods circumvent the blood's immunological components and the cardiac system's native anatomical barriers by directly administering product into the myocardium. In addition, this approach offers the advantage of precise site selection. Two unresolved problems with direct delivery wherein the novel needleless liquid jet approach may resolve are: (1) initial therapeutic retention and (2) subsequent host responses associated with highly focal expression.In this protocol, we present a novel approach to improve direct cardiac gene delivery using a needleless liquid jet methodology. The liquid jet application is essentially a device concept that accelerates and disperses the therapeutic at a targeted myocardial site. The core hypothesis offered is that this approach, with optimized settings, could result in increased therapeutic retention in the initial delivery phase. This would theoretically result in more total myocardial expression per dose while at the same time providing a more homogenous profile around the injection site. Therefore, this would increase efficiency in terms of transduced muscle per delivery site and offer a significant improvement to standard intramuscular injection.

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.

Physical methods of nucleic acid transfer: general concepts and applications

Physical methods of gene (and/or drug) transfer need to combine two effects to deliver the therapeutic material into cells. The physical methods must induce reversible alterations in the plasma membrane to allow the direct passage of the molecules of interest into the cell cytosol. They must also bring the nucleic acids in contact with the permeabilized plasma membrane or facilitate access to the inside of the cell. These two effects can be achieved in one or more steps, depending upon the methods employed. In this review, we describe and compare several physical methods: biolistics, jet injection, hydrodynamic injection, ultrasound, magnetic field and electric pulse mediated gene transfer. We describe the physical mechanisms underlying these approaches and discuss the advantages and limitations of each approach as well as its potential application in research or in preclinical and clinical trials. We also provide conclusions, comparisons, and projections for future developments. While some of these methods are already in use in man, some are still under development or are used only within clinical trials for gene transfer. The possibilities offered by these methods are, however, not restricted to the transfer of genes and the complementary uses of these technologies are also discussed. As these methods of gene transfer may bypass some of the side effects linked to viral or biochemical approaches, they may find their place in specific clinical applications in the future.

Prep1 deficiency induces protection from diabetes and increased insulin sensitivity through a p160-mediated mechanism

We have examined glucose homeostasis in mice hypomorphic for the homeotic transcription factor gene Prep1. Prep1-hypomorphic (Prep1(i/i)) mice exhibit an absolute reduction in circulating insulin levels but normal glucose tolerance. In addition, these mice exhibit protection from streptozotocin-induced diabetes and enhanced insulin sensitivity with improved glucose uptake and insulin-dependent glucose disposal by skeletal muscle. This muscle phenotype does not depend on reduced expression of the known Prep1 transcription partner, Pbx1. Instead, in Prep1(i/i) muscle, we find normal Pbx1 but reduced levels of the recently identified novel Prep1 interactor p160. Consistent with this reduction, we find a muscle-selective increase in mRNA and protein levels of PGC-1alpha, accompanied by enhanced expression of the GLUT4 transporter, responsible for insulin-stimulated glucose uptake in muscle. Indeed, using L6 skeletal muscle cells, we induced the opposite effects by overexpressing Prep1 or p160, but not Pbx1. In vivo skeletal muscle delivery of p160 cDNA in Prep1(i/i) mice also reverses the molecular phenotype. Finally, we show that Prep1 controls the stability of the p160 protein. We conclude that Prep1 controls insulin sensitivity through the p160-GLUT4 pathway.

Electroporation for targeted gene transfer

The utilisation of nonviral gene delivery methods has been increasing steadily, however, a drawback has been the relative low efficiency of gene transfer with naked DNA compared with viral delivery methods. In vivo electroporation, which has previously been used clinically to deliver chemotherapeutic agents, also enhances the delivery of plasmid DNA and has been used to deliver plasmids to several tissue types, particularly muscle and tumour. Recently, a large number of preclinical studies for a variety of therapeutic modalities have demonstrated the potential of electrically mediated gene transfer. Although clinical trials using gene transfer with in vivo electroporation have not as yet been realised, the tremendous growth of this technology suggests that the first trials will soon be initiated.

Current status and future prospects of needle-free liquid jet injectors

Needle-free liquid jet injectors have been used for more than 50 years for parenteral delivery of vaccines and drugs. Although excellent bioavailability has been reported for a number of drugs, occasional pain and bruising have limited wide acceptance of jet injectors. This article reviews jet injectors with respect to their current clinical applications, emerging applications, mechanistic understanding and future prospects.

Nonviral Jet-Injection Gene Transfer for Efficient in Vivo Cytosine Deaminase Suicide Gene Therapy of Colon Carcinoma

Jet-injection technology has developed into an efficient gene delivery system for nonviral in vivo gene transfer. In this study the jet-injector system was used for the intratumoral gene transfer of small volumes of naked DNA encoding the Escherichia coli cytosine deaminase (CD) suicide gene. In our in vivo studies human colon carcinoma (patient-derived tumor model Colo5734 and SW480 colon carcinoma)-bearing NMRI-nu/nu male mice received four jet injections (10 microl per injection) of the CD-gene-carrying plasmid, representing 40 microg plasmid DNA per animal. Forty-eight hours after jet-injection, treatment of tumors with 5-fluorocytosine (5-FC; 500 mg/kg ip) was started and during treatment tumor volumes were measured. Starting from day 5 of 5-FC treatment inhibition of tumor growth was seen in the CD-gene-transduced tumors compared to the respective control groups, which lasted for the entire observation time. Expression analysis at the mRNA and protein levels revealed efficient expression of the CD gene in the jet-injected tumors. Therefore, in this in vivo study jet-injection gene transfer of 40 microg CD-expressing naked plasmid DNA leads to a significant tumor growth inhibition. This study demonstrates the applicability of the jet-injection technology for in vivo gene transfer into tumors to achieve efficient tumor gene therapy.