Pig liver gene therapy by noninvasive interventionist catheterism

Safe Procedure for Efficient Hydrodynamic Gene Transfer to Isolated Porcine Liver in Transplantation

Although calcineurin inhibitors are very effective as immunosuppressants in organ transplantation, complete graft acceptance remains as a challenge. Transfer of genes with immunosuppressant functions could contribute to improving the clinical evolution of transplantation. In this sense, hydrodynamic injection has proven very efficacious for liver gene transfer. In the present work, the hIL-10 gene was hydrofected 'ex vivo' to pig livers during the bench surgery stage, to circumvent the cardiovascular limitations of the procedure, in a model of porcine orthotopic transplantation with a 10-day follow-up. We used IL-10 because human and porcine proteins can be differentially quantified and for its immunomodulatory pleiotropic functions. Safety (biochemical parameters and histology), expression efficacy (RNA transcription and blood protein expression), and acute inflammatory response (cytokines panel) of the procedure were evaluated. The procedure proved safe as no change in biochemical parameters was observed in treated animals, and human IL-10 was efficaciously expressed, with stationary plasma protein levels over 20 pg/mL during the follow-up. Most studied cytokines showed increments (interferon-α, IFN-α; interleukin-1β, IL-1β; tumor necrosis factor α, TNFα; interleukin-6, IL-6; interleukin-8, IL-8; interleukin-4, IL-4; and transforming growth factor-β, TGF-β) in treated animals, without deleterious effects on tissue. Collectively, the results support the potential clinical interest in this gene therapy model that would require further longer-term dose-response studies to be confirmed.

Liver lobe-specific hydrodynamic gene delivery to baboons: A preclinical trial for hemophilia gene therapy

Hydrodynamics-based gene transfer has been successfully employed for in vivo gene delivery to the liver of small animals by tail vein injection and of large animals using a computer-assisted and image-guided protocol. In an effort to develop a hydrodynamic gene delivery procedure clinically applicable for gene therapy, we have evaluated the safety and effectiveness of a lobe-specific hydrodynamic delivery procedure for hepatic gene delivery in baboons. Reporter plasmid was used to assess the gene delivery efficiency of the lobe-specific hydrodynamic gene delivery, and plasmid-carrying human factor IX gene was used to examine the pattern of long-term gene expression. The results demonstrated liver lobe-specific gene delivery, therapeutic levels of human factor IX gene expression lasting for >100 days, and the efficacy of repeated hydrodynamic gene delivery into the same liver lobes. Other than a transient increase in blood concentration of liver enzymes right after the injection, no significant adverse events were observed in animals during the study period. The results obtained from this first non-human primate study support the clinical applicability of the procedure for lobe-specific hydrodynamic gene delivery to liver.

Endoscopic-mediated, biliary hydrodynamic injection mediating clinically relevant levels of gene delivery in pig liver

BACKGROUND AND AIMS

Gene therapy could provide curative therapies to many inherited monogenic liver diseases. Clinical trials have largely focused on adeno-associated viruses (AAVs) for liver gene delivery. These vectors, however, are limited by small packaging size, capsid immune responses, and inability to redose. As an alternative, nonviral, hydrodynamic injection through vascular routes can successfully deliver plasmid DNA (pDNA) into mouse liver but has achieved limited success in large animal models.

METHODS

We explored hydrodynamic delivery of pDNA through the biliary system into the liver of pigs using ERCP and a power injector to supply hydrodynamic force. Human factor IX (hFIX), deficient in hemophilia B, was used as a model gene therapy.

RESULTS

Biliary hydrodynamic injection was well tolerated without significant changes in vital signs, liver enzymes, hematology, or histology. No off-target pDNA delivery to other organs was detected by polymerase chain reaction. Immunohistochemistry revealed that 50.19% of the liver stained positive for hFIX after hydrodynamic injection at 5.5 mg pDNA, with every hepatic lobule in all liver lobes demonstrating hFIX expression. hFIX-positive hepatocytes were concentrated around the central vein, radiating outward across all 3 metabolic zones. Biliary hydrodynamic injection in pigs resulted in significantly higher transfection efficiency than mouse vascular hydrodynamic injection at matched pDNA per liver weight dose (32.7%-51.9% vs 18.9%, P < .0001).

CONCLUSIONS

Biliary hydrodynamic injection using ERCP can achieve higher transfection efficiency into hepatocytes compared with AAVs at magnitudes of less cost in a clinically relevant human-sized large animal. This technology may serve as a platform for gene therapy of human liver diseases.

Parameters of biliary hydrodynamic injection during endoscopic retrograde cholangio-pancreatography in pigs for applications in gene delivery

The biliary system is routinely accessed for clinical purposes via endoscopic retrograde cholangiopancreatography (ERCP). We previously pioneered ERCP-mediated hydrodynamic injection in large animal models as an innovative gene delivery approach for monogenic liver diseases. However, the procedure poses potential safety concerns related mainly to liver or biliary tree injury. Here, we sought to further define biliary hydrodynamic injection parameters that are well-tolerated in a human-sized animal model. ERCP was performed in pigs, and hydrodynamic injection carried out using a novel protocol to reduce duct wall stress. Each pig was subjected to multiple repeated injections to expedite testing and judge tolerability. Different injection parameters (volume, flow rate) and injection port diameters were tested. Vital signs were monitored throughout the procedure, and liver enzyme panels were collected pre- and post-procedure. Pigs tolerated repeated biliary hydrodynamic injections with only occasional, mild, isolated elevation in aspartate aminotransferase (AST), which returned to normal levels within one day post-injection. All other liver tests remained unchanged. No upper limit of volume tolerance was reached, which suggests the biliary tree can readily transmit fluid into the vascular space. Flow rates up to 10 mL/sec were also tolerated with minimal disturbance to vital signs and no anatomic rupture of bile ducts. Measured intrabiliary pressure was up to 150 mmHg, and fluid-filled vesicles were induced in liver histology at high flow rates, mimicking the changes in histology observed in mouse liver after hydrodynamic tail vein injection. Overall, our investigations in a human-sized pig liver using standard clinical equipment suggest that ERCP-guided hydrodynamic injection will be safely tolerated in patients. Future investigations will interrogate if higher flow rates and pressure mediate higher DNA delivery efficiencies.

Improved Lentiviral Gene Delivery to Mouse Liver by Hydrodynamic Vector Injection through Tail Vein

Delivery of genes to mouse liver is routinely accomplished by tail-vein injections of viral vectors or naked plasmid DNA. While viral vectors are typically injected in a low-pressure and -volume fashion, uptake of naked plasmid DNA to hepatocytes is facilitated by high pressure and volumes, also known as hydrodynamic delivery. In this study, we compare the efficacy and specificity of delivery of vesicular stomatitis virus G glycoprotein (VSV-G) pseudotyped lentiviral vectors to mouse liver by a number of injection schemes. Exploiting in vivo bioluminescence imaging as a readout after lentiviral gene transfer, we compare delivery by (1) “conventional” tail-vein injections, (2) “primed” injections, (3) “hydrodynamic” injections, or (4) direct “intrahepatic” injections into exposed livers. Reporter gene activity demonstrate potent and targeted delivery to liver by hydrodynamic injections. Enhanced efficacy is confirmed by analysis of liver sections from mice treated with GFP-encoding vectors, demonstrating 10-fold higher transduction rates and gene delivery to ∼80% of hepatocytes after hydrodynamic vector delivery. In summary, lentiviral vector transfer to mouse liver can be strongly augmented by hydrodynamic tail-vein injections, resulting in both reduced off-target delivery and transduction of the majority of hepatocytes. Our findings pave the way for more effective use of lentiviral gene delivery in the mouse.

Translational Advances of Hydrofection by Hydrodynamic Injection

Hydrodynamic gene delivery has proven to be a safe and efficient procedure for gene transfer, able to mediate, in murine model, therapeutic levels of proteins encoded by the transfected gene. In different disease models and targeting distinct organs, it has been demonstrated to revert the pathologic symptoms and signs. The therapeutic potential of hydrofection led different groups to work on the clinical translation of the procedure. In order to prevent the hemodynamic side effects derived from the rapid injection of a large volume, the conditions had to be moderated to make them compatible with its use in mid-size animal models such as rat, hamster and rabbit and large animals as dog, pig and primates. Despite the different approaches performed to adapt the conditions of gene delivery, the results obtained in any of these mid-size and large animals have been poorer than those obtained in murine model. Among these different strategies to reduce the volume employed, the most effective one has been to exclude the vasculature of the target organ and inject the solution directly. This procedure has permitted, by catheterization and surgical procedures in large animals, achieving protein expression levels in tissue close to those achieved in gold standard models. These promising results and the possibility of employing these strategies to transfer gene constructs able to edit genes, such as CRISPR, have renewed the clinical interest of this procedure of gene transfer. In order to translate the hydrodynamic gene delivery to human use, it is demanding the standardization of the procedure conditions and the molecular parameters of evaluation in order to be able to compare the results and establish a homogeneous manner of expressing the data obtained, as ‘classic’ drugs.

Neutralizing Antibodies Induced by Gene-Based Hydrodynamic Injection Have a Therapeutic Effect in Lethal Influenza Infection

The influenza virus causes annual epidemics and occasional pandemics and is thus a major public health problem. Development of vaccines and antiviral drugs is essential for controlling influenza virus infection. We previously demonstrated the use of vectored immune-prophylaxis against influenza virus infection. We generated a plasmid encoding neutralizing IgG monoclonal antibodies (mAbs) against A/PR/8/34 influenza virus (IAV) hemagglutinin (HA). We then performed electroporation of the plasmid encoding neutralizing mAbs (EP) in mice muscles and succeeded in inducing the expression of neutralizing antibodies in mouse serum. This therapy has a prophylactic effect against lethal IAV infection in mice. In this study, we established a new method of passive immunotherapy after IAV infection. We performed hydrodynamic injection of the plasmid encoding neutralizing mAbs (HD) involving rapid injection of a large volume of plasmid-DNA solution into mice via the tail vein. HD could induce neutralizing antibodies in the serum and in several mucosal tissues more rapidly than in EP. We also showed that a single HD completely protected the mice even after infection with a lethal dose of IAV. We also established other isotypes of anti-HA antibody (IgA, IgM, IgD, and IgE) and showed that like anti-HA IgG, anti-HA IgA was also effective at combating upper respiratory tract IAV infection. Passive immunotherapy with HD could thus provide a new therapeutic strategy targeting influenza virus infection.

Preclinical and clinical advances in transposon-based gene therapy

Transposons derived from Sleeping Beauty (SB), piggyBac (PB), or Tol2 typically require cotransfection of transposon DNA with a transposase either as an expression plasmid or mRNA. Consequently, this results in genomic integration of the potentially therapeutic gene into chromosomes of the desired target cells, and thus conferring stable expression. Non-viral transfection methods are typically preferred to deliver the transposon components into the target cells. However, these methods do not match the efficacy typically attained with viral vectors and are sometimes associated with cellular toxicity evoked by the DNA itself. In recent years, the overall transposition efficacy has gradually increased by codon optimization of the transposase, generation of hyperactive transposases, and/or introduction of specific mutations in the transposon terminal repeats. Their versatility enabled the stable genetic engineering in many different primary cell types, including stem/progenitor cells and differentiated cell types. This prompted numerous preclinical proof-of-concept studies in disease models that demonstrated the potential of DNA transposons for ex vivo and in vivo gene therapy. One of the merits of transposon systems relates to their ability to deliver relatively large therapeutic transgenes that cannot readily be accommodated in viral vectors such as full-length dystrophin cDNA. These emerging insights paved the way toward the first transposon-based phase I/II clinical trials to treat hematologic cancer and other diseases. Though encouraging results were obtained, controlled pivotal clinical trials are needed to corroborate the efficacy and safety of transposon-based therapies.

Efficacy and Safety of Pancreas-Targeted Hydrodynamic Gene Delivery in Rats

Development of an effective, safe, and convenient method for gene delivery to the pancreas is a critical step toward gene therapy for pancreatic diseases. Therefore, we tested the possibility of applying the principle of hydrodynamic gene delivery for successful gene transfer to pancreas using rats as a model. The established procedure involves the insertion of a catheter into the superior mesenteric vein with temporary blood flow occlusion at the portal vein and hydrodynamic injection of DNA solution. We demonstrated that our procedure achieved efficient pancreas-specific gene expression that was 2,000-fold higher than that seen in the pancreas after the systemic hydrodynamic gene delivery. In addition, the level of gene expression achieved in the pancreas by the pancreas-specific gene delivery was comparable to the level in the liver achieved by a liver-specific hydrodynamic gene delivery. The optimal level of reporter gene expression in the pancreas requires an injection volume equivalent to 2.0% body weight with flow rate of 1 mL/s and plasmid DNA concentration at 5 μg/mL. With the exception of transient expansion of intercellular spaces and elevation of serum amylase levels, which recovered within 3 days, no permanent tissue damage was observed. These results suggest that pancreas-targeted hydrodynamic gene delivery is an effective and safe method for gene delivery to the pancreas and clinically applicable.

Transgene Expression in Dogs After Liver-Directed Hydrodynamic Delivery of Sleeping Beauty Transposons Using Balloon Catheters

The Sleeping Beauty transposon system has been extensively tested for integration of reporter and therapeutic genes in vitro and in vivo in mice. Dogs were used as a large animal model for human therapy and minimally invasive infusion of DNA solutions. DNA solutions were delivered into the entire liver or the left side of the liver using balloon catheters for temporary occlusion of venous outflow. A peak intravascular pressure between 80 and 140 mmHg supported sufficient DNA delivery in dog liver for detection of secretable reporter proteins. Secretable reporters allowed monitoring of the time course of gene products detectable in the circulation postinfusion. Canine secreted alkaline phosphatase reporter protein levels were measured in plasma, with expression detectable for up to 6 weeks, while expression of canine erythropoietin was detectable for 7-10 days. All animals exhibited a transient increase in blood transaminases that normalized within 10 days; otherwise the treated animals were clinically normal. These results demonstrate the utility of a secreted reporter protein for real-time monitoring of gene expression in the liver in a large animal model but highlight the need for improved delivery in target tissues to support integration and long-term expression of Sleeping Beauty transposons.

Efficacy of hydrodynamic interleukin 10 gene transfer in human liver segments with interest in transplantation

Different diseases lead, during their advanced stages, to chronic or acute liver failure, whose unique treatment consists in organ transplantation. The success of intervention is limited by host immune response and graft rejection. The use of immunosuppressant drugs generally improve organ transplantation, but they cannot completely solve the problem. Also, their management is delicate, especially during the early stages of treatment. Thus, new tools to set an efficient modulation of immune response are required. The local expression of interleukin (IL) 10 protein in transplanted livers mediated by hydrodynamic gene transfer could improve the organ acceptance by the host because it presents the natural ability to modulate the immune response at different levels. In the organ transplantation scenario, IL10 has already demonstrated positive effects on graft tolerance. Hydrodynamic gene transfer has been proven to be safe and therapeutically efficient in animal models and could be easily moved to the clinic. In the present work, we evaluated efficacy of human IL10 gene transfer in human liver segments and the tissue natural barriers for gene entry into the cell, employing gold nanoparticles. In conclusion, the present work shows for the first time that hydrodynamic IL10 gene transfer to human liver segments ex vivo efficiently delivers a human gene into the cells. Indexes of tissue protein expression achieved could mediate local pharmacological effects with interest in controlling the immune response triggered after liver transplantation. On the other hand, the ultrastructural study suggests that the solubilized plasmid could access the hepatocyte in a passive manner mediated by the hydric flow and that an active mechanism of transportation could facilitate its entry into the nucleus. Liver Transplantation 23:50-62 2017 AASLD.

Studying Closed Hydrodynamic Models of "In Vivo" DNA Perfusion in Pig Liver for Gene Therapy Translation to Humans

INTRODUCTION

Expressing exogenous genes after naked DNA delivery into hepatocytes might achieve sustained and high expression of human proteins. Tail vein DNA injection is an efficient procedure for gene transfer in murine liver. Hydrodynamic procedures in large animals require organ targeting, and improve with liver vascular exclusion. In the present study, two closed liver hydrofection models employing the human alpha-1-antitrypsin (hAAT) gene are compared to reference standards in order to evaluate their potential clinical interest.

MATERIAL AND METHODS

A solution of naked DNA bearing the hAAT gene was retrogradely injected in 7 pig livers using two different closed perfusion procedures: an endovascular catheterization-mediated procedure (n = 3) with infrahepatic inferior vena cava and portal vein blockage; and a surgery-mediated procedure (n = 4) with completely sealed liver. Gene transfer was performed through the suprahepatic inferior cava vein in the endovascular procedure and through the infrahepatic inferior vena cava in the surgical procedure. The efficiency of the procedures was evaluated 14 days after hydrofection by quantifying the hAAT protein copies per cell in tissue and in plasma. For comparison, samples from mice (n = 7) successfully hydrofected with hAAT and healthy human liver segments (n = 4) were evaluated.

RESULTS

Gene decoding occurs efficiently using both procedures, with liver vascular arrest improving its efficiency. The surgically closed procedure (sealed organ) reached higher tissue protein levels (4x10^5- copies/cell) than the endovascular procedure, though the levels were lower than in human liver (5x10^6- copies/cell) and hydrofected mouse liver (10^6- copies/cell). However, protein levels in plasma were lower (p<0.001) than the reference standards in all cases.

CONCLUSION

Hydrofection of hAAT DNA to "in vivo" isolated pig liver mediates highly efficient gene delivery and protein expression in tissue. Both endovascular and surgically closed models mediate high tissue protein expression. Impairment of protein secretion to plasma is observed and might be species-related. This study reinforces the potential application of closed liver hydrofection for therapeutic purposes, provided protein secretion improves.

Effects of Fibrotic Tissue on Liver-targeted Hydrodynamic Gene Delivery

Hydrodynamic gene delivery is a common method for gene transfer to the liver of small animals, and its clinical applicability in large animals has been demonstrated. Previous studies focused on functional analyses of therapeutic genes in animals with normal livers and little, however, is known regarding its effectiveness and safety in animals with liver fibrosis. Therefore, this study aimed to examine the effects of liver fibrosis on hydrodynamic gene delivery efficiency using a rat liver fibrosis model. We demonstrated for the first time, using pCMV-Luc plasmid, that this procedure is safe and that the amount of fibrotic tissue in the liver decreases gene delivery efficiency, resulting in decrease in luciferase activity depending on the volume of fibrotic tissue in the liver and the number of hepatocytes that are immunohistochemically stained positive for transgene product. We further demonstrate that antifibrotic gene therapy with matrix metalloproteinase-13 gene reduces liver fibrosis and improves efficiency of hydrodynamic gene delivery. These results demonstrate the negative effects of fibrotic tissue on hydrodynamic gene delivery and its recovery by appropriate antifibrotic therapy.

Image-Guided Hydrodynamic Gene Delivery: Current Status and Future Directions

Hydrodynamics-based delivery has been used as an experimental tool to express transgene in small animals. This in vivo gene transfer method is useful for functional analysis of genetic elements, therapeutic effect of oligonucleotides, and cancer cells to establish the metastatic cancer animal model for experimental research. Recent progress in the development of image-guided procedure for hydrodynamics-based gene delivery in large animals directly supports the clinical applicability of this technique. This review summarizes the current status and recent progress in the development of hydrodynamics-based gene delivery and discusses the future directions for its clinical application.

Human AAT gene transfer to pig liver improved by using a perfusion isolated organ endovascular procedure

OBJECTIVE

The efficiency of endovascular liver gene transfer in pigs is evaluated by comparing two models of retrograde catheterization: single lobe catheterization with portal inflow (open procedure) versus whole liver isolation with portal and inferior vena cava blockage (close procedure).

METHODS

Percutaneous endovascular catheterization was performed in pigs. Open procedure (n = 3): 8Fr balloon catheter placement in a suprahepatic branch through the jugular vein. Closed procedure (n = 3): simultaneous catheterization of the intrahepatic portal vein (transhepatic catheterization, 10Fr balloon catheter), the supra- and infrahepatic cava veins (8Fr balloon catheters through the jugular and femoral veins). In both models, 200 ml of hAAT DNA solution (20 μg/ml) were retrogradely injected at 20 ml/s. Tissue samples (8 per liver) were obtained 14 days later and the exogenous DNA, RNA and protein per cell were quantified. Blood samples were collected periodically for transaminase determination in all the animals.

RESULTS

The open procedure achieved lower (approx. 1000-fold) DNA delivery, resulting in a significantly lower (p < 0.001) gene transcription (> 100-fold). The closed model also achieved a higher translation index, although differences were smaller (p < 0.001).

CONCLUSIONS

Portal inflow blockage increased the delivery, transcription and translation indexes, significantly improving the final procedure efficacy when compared with an open procedure.

KEY POINTS

Endovascular hydrodynamic pig liver gene transfer: open procedure versus closed procedure. Open procedure resulted in much lower DNA delivery than closed model. Open procedure reached significantly lower gene transcription index. Translation index with closed model was higher than with the open.

Gene therapy for inherited diseases of liver metabolism

Gene therapy is entering the stage of initial clinical development to treat a growing number of inherited metabolic diseases. This review outlines the development of liver-directed gene therapy for diseases caused by deficiencies of enzymes that are primarily expressed in the liver and discusses the disorders that appear most promising for clinical translation.

Hydrodynamic delivery

Hydrodynamic delivery (HD) is a broadly used procedure for DNA and RNA delivery in rodents, serving as a powerful tool for gene/protein drug discovery, gene function analysis, target validation, and identification of elements in regulating gene expression in vivo. HD involves a pressurized injection of a large volume of solution into a vasculature. New procedures are being developed to satisfy the need for a safe and efficient gene delivery in clinic. Here, we summarize the fundamentals of HD, its applications, and future perspectives for clinical use.

Safety assessment of liver-targeted hydrodynamic gene delivery in dogs

Evidence in support of safety of a gene delivery procedure is essential toward gene therapy. Previous studies using the hydrodynamics-based procedure primarily focus on gene delivery efficiency or gene function analysis in mice. The current study focuses on an assessment of the safety of computer-controlled and liver-targeted hydrodynamic gene delivery in dogs as the first step toward hydrodynamic gene therapy in clinic. We demonstrate that the impacts of the hydrodynamic procedure were limited in the injected region and the influences were transient. Histological examination and the hepatic microcirculation measurement using reflectance spectrophotometry reveal that the liver-specific impact of the procedure involves a transient expansion of the liver sinusoids. No systemic damage or toxicity was observed. Physiological parameters, including electrocardiogram, heart rate, blood pressure, oxygen saturation, and body temperature, remained in normal ranges during and after hydrodynamic injection. Body weight was also examined to assess the long-term effects of the procedure in animals who underwent 3 hydrodynamic injections in 6 weeks with 2-week time interval in between. Serum biochemistry analysis showed a transient increase in liver enzymes and a few cytokines upon injection. These results demonstrate that image-guided, liver-specific hydrodynamic gene delivery is safe.

Hemodynamics of a hydrodynamic injection

The hemodynamics during a hydrodynamic injection were evaluated using cone beam computed tomography (CBCT) and fluoroscopic imaging. The impacts of hydrodynamic (5 seconds) and slow (60 seconds) injections into the tail veins of mice were compared using 9% body weight of a phase-contrast medium. Hydrodynamically injected solution traveled to the heart and drew back to the hepatic veins (HV), which led to liver expansion and a trace amount of spillover into the portal vein (PV). The liver volumes peaked at 165.6 ± 13.3% and 165.5 ± 11.9% of the original liver volumes in the hydrodynamic and slow injections, respectively. Judging by the intensity of the CBCT images at the PV, HV, right atrium, liver parenchyma (LP), and the inferior vena cava (IVC) distal to the HV conjunction, the slow injection resulted in the higher intensity at PV than at LP. In contrast, a significantly higher intensity was observed in LP after hydrodynamic injection in comparison with that of PV, suggesting that the liver took up the iodine from the blood flow. These results suggest that the enlargement speed of the liver, rather than the expanded volume, primarily determines the efficiency of hydrodynamic delivery to the liver.

Hemodynamics of a hydrodynamic injection

The hemodynamics during a hydrodynamic injection were evaluated using cone beam computed tomography (CBCT) and fluoroscopic imaging. The impacts of hydrodynamic (5 seconds) and slow (60 seconds) injections into the tail veins of mice were compared using 9% body weight of a phase-contrast medium. Hydrodynamically injected solution traveled to the heart and drew back to the hepatic veins (HV), which led to liver expansion and a trace amount of spillover into the portal vein (PV). The liver volumes peaked at 165.6 ± 13.3% and 165.5 ± 11.9% of the original liver volumes in the hydrodynamic and slow injections, respectively. Judging by the intensity of the CBCT images at the PV, HV, right atrium, liver parenchyma (LP), and the inferior vena cava (IVC) distal to the HV conjunction, the slow injection resulted in the higher intensity at PV than at LP. In contrast, a significantly higher intensity was observed in LP after hydrodynamic injection in comparison with that of PV, suggesting that the liver took up the iodine from the blood flow. These results suggest that the enlargement speed of the liver, rather than the expanded volume, primarily determines the efficiency of hydrodynamic delivery to the liver.

Irreversible electroporation facilitates gene transfer of a GM-CSF plasmid with a local and systemic response

BACKGROUND

Electroporation uses an electric field to induce pores in the cell membrane that can transfer macromolecules into target cells. Modulation of electrical parameters leads to irreversible electroporation (IRE), which is being developed for tissue ablation. We sought to evaluate whether the application of IRE may induce a lesser electric field in the periphery where reversible electroporation may occur, facilitating gene transfer of a granulocyte macrophage colony-stimulating factor (GM-CSF) plasmid to produce its biologic response.

METHODS

Yorkshire pigs underwent laparotomy, and IRE of the liver was performed during hepatic arterial infusion of 1 or 7 mg of a naked human GM-CSF plasmid. The serum, liver, lymph nodes, and bone marrow were harvested for analysis.

RESULTS

Human GM-CSF level rose from undetectable to 131 pg/mL in the serum at 24 hours after IRE and plasmid infusion. The liver demonstrated an ablation zone surrounded by an immune infiltrate that had greater macrophage intensity than when treated with IRE or plasmid infusion alone. This dominance of macrophages was dose dependent. Distant effects of GM-CSF were found in the bone marrow, where proliferating myeloid cells increased from 14% to 25%.

CONCLUSION

IRE facilitated gene transfer of the GM-CSF plasmid and brought about a local and systemic biologic response. This technique holds potential for tumor eradication and immunotherapy of residual cancer.

Parameters Affecting Image-guided, Hydrodynamic Gene Delivery to Swine Liver

Development of a safe and effective method for gene delivery to hepatocytes is a critical step toward gene therapy for liver diseases. Here, we assessed the parameters for gene delivery to the livers of large animals (pigs, 40-65 kg) using an image-guided hydrodynamics-based procedure that involves image-guided catheter insertion into the lobular hepatic vein and hydrodynamic injection of reporter plasmids using a computer-controlled injector. We demonstrated that injection parameters (relative position of the catheter in the hepatic vasculature, intravascular pressure upon injection, and injection volume) are directly related to the safety and efficiency of the procedure. By optimizing these parameters, we explored for the first time, the advantage of the procedure for sequential injections to multiple lobes in human-sized pigs. The optimized procedure resulted in sustained expression of the human α-1 antitrypsin gene in livers for more than 2 months after gene delivery. In addition, repeated hydrodynamic gene delivery was safely conducted and no adverse events were seen in the entire period of the study. Our results support the clinical applicability of the image-guided hydrodynamic gene delivery method for the treatment of liver diseases.Molecular Therapy-Nucleic Acids (2013) 2, e128; doi:10.1038/mtna.2013.52; published online 15 October 2013.

Efficient liver gene transfer with foamy virus vectors

Background

Liver gene transfer offers hope for the correction of genetic and acquired disorders. Efficient gene transfer in large animals can be obtained with hydrodynamic gene transfer (HGT), a method that can achieve sufficient levels of gene delivery.

Material/Methods

To test the relative efficiency between plasmid versus foamy virus (FV) vector-based liver gene transfer efficiency, we applied HGT in 4 juvenile pigs, using the same plasmid backbone, either naked or coated as a FV vector particle. Gene transfer efficiency and persistence of expression was assayed by PCR and real-time PCR, respectively, at 1 week and at 1 month after the infusions.

Results

HGT was tolerated well and no adverse reactions were observed. Plasmid injections resulted in no detectable DNA sequences at 1 week. At the 1 month time point, 2/15 liver sections analyzed were positive for the presence of plasmid DNA. When FV vectors were infused under identical conditions, 18/28 (64.3%) of the liver samples were positive for the presence of vector sequences, and the expression levels reached 29.7 and 15.6% of the endogenous GAPDH levels in the injected and the adjacent liver lobes.

Conclusions

Our results indicate that medium-term therapeutic levels of gene expression can be obtained with FV vectors, an effect that can be attributed to the potential of the HGT procedure and to the natural affinity of FV vectors for hepatocytes.

Novel electric power-driven hydrodynamic injection system for gene delivery: safety and efficacy of human factor IX delivery in rats

The development of a safe and reproducible gene delivery system is an essential step toward the clinical application of the hydrodynamic gene delivery (HGD) method. For this purpose, we have developed a novel electric power-driven injection system called the HydroJector-EM, which can replicate various time-pressure curves preloaded into the computer program before injection. The assessment of the reproducibility and safety of gene delivery system in vitro and in vivo demonstrated the precise replication of intravascular time-pressure curves and the reproducibility of gene delivery efficiency. The highest level of luciferase expression (272 pg luciferase per mg of proteins) was achieved safely using the time-pressure curve, which reaches 30 mm Hg in 10 s among various curves tested. Using this curve, the sustained expression of a therapeutic level of human factor IX protein (>500 ng ml(-1)) was maintained for 2 months after the HGD of the pBS-HCRHP-FIXIA plasmid. Other than a transient increase in liver enzymes that recovered in a few days, no adverse events were seen in rats. These results confirm the effectiveness of the HydroJector-EM for reproducible gene delivery and demonstrate that long-term therapeutic gene expression can be achieved by automatic computer-controlled hydrodynamic injection that can be performed by anyone.

The liver as a target organ for gene therapy: state of the art, challenges, and future perspectives

The liver is a target for gene therapy of inborn errors of metabolism, of hemophilia, and of acquired diseases such as liver cancer and hepatitis. The ideal gene transfer strategy should deliver the transgene DNA to parenchymal liver cells with accuracy and precision in the absence of side effects. Liver sinusoids are highly specialized capillaries with a particular endothelial lining: the endothelium contains open fenestrae, whereas a basal lamina is lacking. Fenestrae provide a direct access of gene transfer vectors to the space of Disse, in which numerous microvilli from parenchymal liver cells protrude. The small diameter of fenestrae in humans constitutes an anatomical barrier for most gene transfer vectors with the exception of adeno-associated viral (AAV) vectors. Recent studies have demonstrated the superiority of novel AAV serotypes for hepatocyte-directed gene transfer applications based on enhanced transduction, reduced prevalence of neutralizing antibodies, and diminished capsid immune responses. In a landmark clinical trial, hemophilia B was successfully treated with an AAV8 human factor IX expressing vector. Notwithstanding significant progress, clinical experience with these technologies remains very limited and many unanswered questions warrant further study. Therefore, the field should continue to progress as it has over the past decade, cautiously and diligently.

DNA delivery to 'ex vivo' human liver segments

Hydrodynamic injection is an efficient procedure for liver gene therapy in rodents but with limited efficacy in large animals, using an 'in vivo' adapted regional hydrodynamic gene delivery system. We study the ability of this procedure to mediate gene delivery in human liver segments obtained by surgical resection. Watertight liver segments were retrogradely injected from hepatic vein with a saline solution containing a plasmid bearing the enhanced green fluorescent protein (eGFP) gene, under different conditions of flow rate (1, 10 and 20 ml s(-1)) and final perfused volume. Samples were cultured for 1 to 2 days and used for microscopy and molecular analysis of gene expression. The fluorescent and immunohistochemistry studies indicated that in segments injected at ≥10 ml s(-1), good and wide gene expression was present in the liver sections and the molecular analysis reinforced the histological observation in a quantitative manner (index of apparent gene delivery: 10(2)-10(4) eGFP DNA copy per 100 pg of total DNA; transcription index: 10(5)-2 × 10(6) eGFP RNA copy per 100 ng of total RNA). In addition, injected gold nanoparticles (15 nm diameter) suggested that DNA delivery to hepatocytes must involve a facilitated permeation process without membrane disruption. In summary, we show that retrograde venous injection of watertight human liver segment is an anadromous procedure that results in wide liver gene delivery and good gene expression. However, additional studies will be necessary to clarify the influence of the prolonged ischemia injury to hepatocytes in our model.

Efficacy and safety of Sleeping Beauty transposon-mediated gene transfer in preclinical animal studies

Sleeping Beauty (SB) transposons have been effective in delivering therapeutic genes to treat certain diseases in mice. Hydrodynamic gene delivery of integrating transposons to 5-20% of the hepatocytes in a mouse results in persistent elevated expression of the therapeutic polypeptides that can be secreted into the blood for activity throughout the animal. An alternative route of delivery is ex vivo transformation with SB transposons of hematopoietic cells, which then can be reintroduced into the animal for treatment of cancer. We discuss issues associated with the scale-up of hydrodynamic delivery to the liver of larger animals as well as ex vivo delivery. Based on our and others' experience with inefficient delivery to larger animals, we hypothesize that impulse, rather than pressure, is a critical determinant of the effectiveness of hydrodynamic delivery. Accordingly, we propose some alterations in delivery strategies that may yield efficacious levels of gene delivery in dogs and swine that will be applicable to humans. To ready hydrodynamic delivery for human application we address a second issue facing transposons used for gene delivery regarding their potential to "re-hop" from one site to another and thereby destabilize the genome. The ability to correct genetic diseases through the infusion of DNA plasmids remains an appealing goal.

The therapeutic potential of ΦC31 integrase as a gene therapy system

INTRODUCTION

The φC31 integrase system is a phage-derived system that offers the ability to integrate plasmid DNA into the chromosomes at a subset of endogenous preferred locations associated with robust gene expression. Recent progress highlights the unique advantages of this system for in vivo gene therapy and for use in stem cells.

AREAS COVERED

The φC31 integrase system has been under development for ten years and has been demonstrated to be effective for integration of plasmids in a variety of tissues and organs for gene therapy in animal systems, as well as in isolated human cells. We focus on work with the φC31 integrase system during the past 12-18 months. This work has centered on a series of papers involving in vivo delivery of the integrase system to the liver and a variety of studies demonstrating the utility of the integrase system in stem cells.

EXPERT OPINION

We conclude that the φC31 integrase system has significant potential for liver gene therapy, if effective DNA delivery methods for large mammals become available. The φC31 integrase system displays an outstanding fit for use in pluripotent stem cells, and this area is expected to be the subject of intense development.

α-1-antitrypsin gene delivery reduces inflammation, increases T-regulatory cell population size and prevents islet allograft rejection

Antiinflammatory clinical-grade, plasma-derived human α-1 antitrypsin (hAAT) protects islets from allorejection as well as from autoimmune destruction. hAAT also interferes with disease progression in experimental autoimmune encephalomyelitis (EAE) and in collagen-induced arthritis (CIA) mouse models. hAAT increases IL-1 receptor antagonist expression in human mononuclear cells and T-regulatory (Treg) cell population size in animal models. Clinical-grade hAAT contains plasma impurities, multiple hAAT isoforms and various states of inactive hAAT. We thus wished to establish islet-protective activities and effect on Treg cells of plasmid-derived circulating hAAT in whole animals. Islet function was assessed in mice that received allogeneic islet transplants after mice were given hydrodynamic tail-vein injection with pEF-hAAT, a previously described Epstein-Barr virus (EBV) plasmid construct containing the EBV nuclear antigen 1 (EBNA1) and the family of repeat EBNA1 binding site components (designated "EF") alongside the hAAT gene. Sera collected from hAAT-expressing mice were added to lipopolysaccharide (LPS)-stimulated macrophages to assess macrophage responsiveness. Also, maturation of peritoneal cells from hAAT-expressing mice was evaluated. hAAT-expressing mice accepted islet allografts (n = 11), whereas phosphate-buffered saline-injected animals (n = 11), as well as mice treated with truncated-hAAT-plasmid (n = 6) and untreated animals (n = 20) rapidly rejected islet allografts. In hAAT-expressing animals, local Treg cells were abundant at graft sites, and the IL-1 receptor antagonist was elevated in grafts and circulation. Sera from hAAT-expressing mice, but not control mice, inhibited macrophage responses. Finally, peritoneal cells from hAAT-expressing mice exhibited a semimature phenotype. We conclude that plasmid-derived circulating hAAT protects islet allografts from acute rejection, and human plasma impurities are unrelated to islet protection. Future studies may use this in vivo approach to examine the structure-function characteristics of the protective activities of AAT by manipulation of the hAAT plasmid.

Analysis of metabolic and gene expression changes after hydrodynamic DNA injection into mouse liver

The hydrodynamic injection in mice tail vein of a plasmid (40 µg DNA) bearing the human α1-antitrypsin gene mediates: a) good liver gene transfer resulting in therapeutic plasma levels of human protein (1 mg/ml, approximately) from days 1-10 after injection; b) low liver injury as demonstrated by a poor and transient increase of aspartate aminotransferase (AST) and alanine transaminase (ALT) in mouse plasma; 3) limited expression and metabolic changes in host liver genes and metabolites as evaluated on days 2 and 10 after injection. Groups of three mice were uninjected (control) or hydrodynamically injected with saline or plasmid DNA and then sacrificed on days 2 and 10 after injection. The results of principal component analysis (PCA) show, both in expression microarray and metabolomic analysis, that changes between control and hydrodynamically injected groups are not dramatic and tend to normalize after 10 d. The differences are even smaller between DNA and saline hydrodynamically injected mice. Hydrodynamic injection induces a complex but limited gene expression and metabolic change which includes variations in molecules related to energy metabolism and stress response. The results contribute to support that hydrodynamic method is a safe procedure of liver gene transfer but the long-term effect of hydrodynamic gene transfer procedure, remains to be studied.

The Sleeping Beauty transposon system: a non-viral vector for gene therapy

Over the past decade, the Sleeping Beauty (SB) transposon system has been developed as the leading non-viral vector for gene therapy. This vector combines the advantages of viruses and naked DNA. Here we review progress over the last 2 years in vector design, methods of delivery and safety that have supported its use in the clinic. Currently, the SB vector has been validated for ex vivo gene delivery to stem cells, including T-cells for the treatment of lymphoma. Progress in delivery of SB transposons to liver for treatment of various systemic diseases, such as hemophilia and mucopolysaccharidoses types I and VII, has encountered some problems, but even here progress is being made.

Minimal invasive technique for gene delivery in porcine liver lobe segment

INTRODUCTION

The feasibility and outcome of large volume injection of gene solution in a segment of a liver lobe, without backflow, were studied in a porcine model, using a custom-designed balloon catheter.

METHOD

Eight anesthetized pigs underwent successful injection of 200 ml of gene solution at a rate of 20 ml/s via a minimally invasive technique without backflow. A custom-made balloon catheter was introduced under fluoroscopy guidance into the right lateral liver lobe via the right external jugular vein. The vein of the liver lobe was occluded with the balloon catheter and contrast material was injected to check if total occlusion was achieved. Since there was no backflow an angiographic pump injected the solution. The catheter was left in place for 10 min. Then contrast material was injected to check whether the vein remained occluded.

RESULTS

All animals tolerated the procedure without obvious adverse effects. Ultrasound scan showed no gross changes within liver three days following the infusion. A transient rise in platelet count was observed which returned to normal after 13 days and remained stable; all other biochemistry values were normal.

CONCLUSIONS

Injecting large volume of gene solution in a liver lobe segment using this minimally invasive technique in a porcine model is possible, making the development of a successful gene transfer protocol in humans feasible.

Long-term phenotypic correction in factor IX knockout mice by using ΦC31 integrase-mediated gene therapy

Hemophilia B, a hereditary bleeding disorder caused by a deficiency of coagulation factor IX (FIX), is an excellent candidate for gene therapy. However, to date, success in hemophilia gene therapy clinical trials has been limited due to failure to achieve or sustain therapeutic levels of factor expression. The ΦC31 integrase system efficiently integrates plasmid DNA carrying a transgene and an attB site into a limited number of endogenous pseudo attP sites in mammalian genomes, leading to robust, sustained transgene expression. A strategy utilizing plasmid DNA integrated with ΦC31 integrase may offer a facile and safe alternative for sustained human FIX (hFIX) expression. Hydrodynamic tail vein injection was used for delivery of plasmids encoding ΦC31 integrase and hFIX to the liver of FIX knockout mice. We demonstrated prolonged therapeutic levels of hFIX in this knockout mouse model of hemophilia B over a 6-month time course when ΦC31 integrase was used. Additionally, we observed sustained FIX activity in plasma and phenotypic correction of bleeding after tail clip in ΦC31-treated mice. In the livers that received integrase, we also demonstrated prolonged hFIX expression in hepatocytes by immunohistochemistry and documented sequence-specific genomic integration of the hFIX plasmid. These studies suggest the possibility that a similar approach in large animals and humans could lead to a simple and successful gene therapy for hemophilia.

Critical physiological and surgical considerations for hydrodynamic pressurization of individual segments of the pig liver

Hydrodynamic gene delivery to the liver is a promising approach for liver gene therapy in the clinic, but levels of gene expression in larger species have been much less than in rodents. The development of surgical techniques for pressurizing individual liver segments and the establishment of whether hepatic vascular anatomy in fact permits pressurization of individual segments are critical issues that need to be addressed. We have evaluated these issues using hydrodynamic delivery to individual segments of the pig liver, via branches of both portal and hepatic veins. Our objective was to develop surgical techniques that achieve elevated vascular pressures within individual liver segments with small volumes, but without interruption of portal blood flow or reduction in venous return to the heart. We report that, without specific surgical interventions to obstruct outflow of DNA solution from the targeted liver segment, little or no increase in intrahepatic vascular pressure occurs. We demonstrate, for the first time, that selective pressurization of individual liver segments is possible without compromising portal venous flow or venous return to the heart. Thus, hydrodynamic gene delivery to individual liver segments is technically achievable in a clinical setting, but will require open abdominal surgery rather than minimally invasive techniques.

Translating Sleeping Beauty transposition into cellular therapies: victories and challenges

Recent results confirm that long-term expression of therapeutic transgenes can be achieved by using a transposon-based system in primary stem cells and in vivo. Transposable elements are natural DNA transfer vehicles that are capable of efficient genomic insertion. The latest generation, Sleeping Beauty transposon-based hyperactive vector (SB100X), is able to address the basic problem of non-viral approaches - that is, low efficiency of stable gene transfer. The combination of transposon-based non-viral gene transfer with the latest improvements of non-viral delivery techniques could provide a long-term therapeutic effect without compromising biosafety. The new challenges of pre-clinical research will focus on further refinement of the technology in large animal models and improving the safety profile of SB vectors by target-selected transgene integration into genomic "safe harbors." The first clinical application of the SB system will help to validate the safety of this approach.

Naked DNA delivery to whole pig cardiac tissue by coronary sinus retrograde injection employing non-invasive catheterization

BACKGROUND

Hydrodynamic injection has demonstrated to be very efficient in the liver of small animals, although this procedure must be translated to the clinical practice in a milder but no less efficient way. The present study evaluates the capacity of non-invasive interventional catheterization as a procedure for naked DNA delivery to the heart in large animals.

METHODS

Two catheters were placed in the coronary sinus: one of them to block blood circulation and the other to retrogradely inject 50 ml of a saline solution of DNA (20 µg/ml) containing the enhanced green fluorescent protein (EGFP) gene, at a flow rate of 5 ml/s.

RESULTS

The results obtained show that EGFP protein, identified by immunohistochemistry, was present and widely distributed throughout the atrial and ventricular cardiac tissue. This observation agrees with the efficiency of EGFP gene delivery resulting in 1-200 EGFP gene copies per endogenous haploid genome. However, the transcription efficiency of the exogenous EGFP gene was at a ratio of 0.2-10 copies with respect to the endogenous GAPDH gene, suggesting that optimized gene constructs for expression in cardiac tissue could increase the final efficacy of gene transfer.

CONCLUSIONS

We conclude that the retrovenous injection of naked DNA in the coronary sinus employing the catheterization technique is an easy and probably safe method for whole cardiac gene transfer.

Gene expression in lung and liver after intravenous infusion of polyethylenimine complexes of Sleeping Beauty transposons

Two methods of systemic gene delivery have been extensively explored, using the mouse as a model system: hydrodynamic delivery, wherein a DNA solution equivalent in volume to 10% of the mouse weight is injected intravenously in less than 10 sec, and condensation of DNA with polyethylenimine (PEI) for standard intravenous infusion. Our goal in this study was to evaluate quantitatively the kinetics of gene expression, using these two methods for delivery of Sleeping Beauty transposons. Transposons carrying a luciferase expression cassette were injected into mice either hydrodynamically or after condensation with PEI at a PEI nitrogen-to-DNA phosphate ratio of 7. Gene expression in the lungs and liver after hydrodynamic delivery resulted in exponential decay with a half-life of about 35-40 hr between days 1 and 14 postinjection. The decay kinetics of gene expression after PEI-mediated gene delivery were more complex; an initial decay rate of 6 hr was followed by a more gradual loss of activity. Consequently, the liver became the primary site of gene expression about 4 days after injection of PEI-DNA, and by 14 days expression in the liver was 10-fold higher than in the lung. Overall levels of gene expression 2 weeks postinjection were 100- to 1000-fold lower after PEI-mediated delivery compared with hydrodynamic injection. These results provide insight into the relative effectiveness and organ specificity of these two methods of nonviral gene delivery when coupled with the Sleeping Beauty transposon system.

Technical requirements for effective regional hydrodynamic gene delivery to the left lateral lobe of the rat liver

Hydrodynamic gene delivery to the liver is an attractive approach for clinical liver gene therapy, but critical aspects of technique remain uncertain. There has not been to date any report of high levels of hydrodynamic gene delivery to the liver, except in rodents. Regional hydrodynamic delivery to individual lobes/segments of the liver is being pursued in preclinical pig models, where reporter gene expression has been <1% of rodent levels, and in one clinical study, where there was no substantive evidence of gene expression. In none of these studies did surgical technique include outflow obstruction of the DNA solution. Here we report a novel technique for regional hydrodynamic gene delivery to the left lateral lobe of the rat liver. The technique gives high levels of gene delivery specific to the left lateral lobe with low volumes ( approximately 1.5 ml) of DNA solution, and permits an evaluation of hydrodynamic delivery in the presence and in the absence of outflow obstruction. We report that outflow obstruction is an absolute requirement for effective hydrodynamic gene delivery to individual lobes/segments of the liver, and therefore that minimally invasive techniques will not be possible in the clinic.

Long-term physiologically regulated expression of the low-density lipoprotein receptor in vivo using genomic DNA mini-gene constructs

Familial hypercholesterolemia (FH) is a condition caused by mutations in the low-density lipoprotein receptor (LDLR) gene. Expression of LDLR is highly regulated and excess receptor expression is cytotoxic. To incorporate essential gene regulation into a gene therapy vector for FH, we generated vectors in which the expression of therapeutic human LDLR gene, or luciferase reporter gene, is driven by 10 kb of human LDLR genomic DNA encompassing the promoter region including elements essential for physiologically regulated expression. Using luciferase expression and specific LDL binding and internalization assays, we have shown in vitro that the genomic promoter element confers long-term, physiologically regulated gene expression and complementation of receptor deficiency in culture for 240 cell-generations. This was demonstrated in the presence of sterols or statins, modifiers of LDLR promoter activity. In vivo, we demonstrate efficient liver-specific delivery and expression of luciferase following hydrodynamic tail-vein injection and confirm that expression from the LDLR promoter element is sensitive to statin administration. We also demonstrate long-term LDLR expression from the 10-kb promoter element up to 9 months following delivery. The vector system that we describe provides the efficient delivery, long-term expression, and physiological regulation required for a successful gene therapy intervention for FH.

Effect of nuclear localization and hydrodynamic delivery-induced cell division on phiC31 integrase activity

Phage φC31 integrase is a recombinase that can be expressed in mammalian cells to integrate plasmids carrying an attB sequence into the genome at specific pseudo attP locations. We demonstrate by immunofluoresence that wild-type φC31 integrase is cytoplasmic and that addition of a SV40 nuclear localization signal (NLS) localizes φC31 integrase to the nucleus. Unexpectedly, the NLS depressed integration efficiency in HeLa cells and provided no benefit when used to integrate the human Factor IX (hFIX) gene into mouse liver. Since breakdown of the nuclear membrane during mitosis could allow cytoplasmic integrase access to the chromosomes, we analyzed whether cell division was required for integration into liver cells in vivo. Hepatocytes were labeled with iododeoxyuridine to mark cells that underwent DNA replication during the week following hydrodynamic injection. Hydrodynamic delivery led to DNA replication in one-third of hepatocytes. Approximately 3 out of 4 cells having φC31 integrase-mediated stable hFIX expression did not undergo replication, indicating that cell division was not required for integrase function in liver. Therefore, although the bulk of φC31 integrase protein appears to be cytoplasmic in mammalian cells, integration can still occur in the nucleus, even without cell division.

Image-guided, intravascular hydrodynamic gene delivery to skeletal muscle in pigs

Development of an effective, safe, and convenient method for gene delivery to muscle is a critical step toward gene therapy for muscle-associated diseases. Toward this end, we have explored the possibility of combining the image-guided catheter insertion technique with the principle of hydrodynamic delivery to achieve muscle-specific gene transfer in pigs. We demonstrate that gene transfer efficiency of the procedure is directly related to flow rate, injection pressure, and injection volume. The optimal gene delivery was achieved at a flow rate of 15 ml/second with injection pressure of 300 psi and injection volume equal to 1.5% of body weight. Under such a condition, hydrodynamic injection of saline containing pCMV-Luc (100 microg/ml) resulted in luciferase activity of 10(6) to 10(7) relative light units (RLU)/mg of proteins extracted from the targeted muscle 5 days after hydrodynamic gene delivery. Result from immunohistochemical analysis revealed 70-90% transfection efficiency of muscle groups in the hindlimb and persistent reporter gene expression for 2 months in transfected cells. With an exception of transient edema and elevation of creatine phosphokinase, no permanent tissue damage was observed. These results suggest that the image-guided, intravenous hydrodynamic delivery is an effective and safe method for gene delivery to skeletal muscle.

Antioxidant enzyme gene transfer for ischemic diseases

The balance of redox is pivotal for normal function and integrity of tissues. Ischemic insults occur as results of a variety of conditions, leading to an accumulation of reactive oxygen species (ROS) and an imbalanced redox status in the tissues. The oxidant stress may activate signaling mechanisms provoking more toxic events, and eventually cause tissue damage. Therefore, treatments with antioxidants, free radical scavengers and their mimetics, as well as gene transfer approaches to overexpress antioxidant genes represent potential therapeutic options to correct the redox imbalance. Among them, antioxidant gene transfer may enhance the production of antioxidant scavengers, and has been employed to experimentally prevent or treat ischemic injury in cardiovascular, pulmonary, hepatic, intestinal, central nervous or other systems in animal models. With improvements in vector systems and delivery approaches, innovative antioxidant gene therapy has conferred better outcomes for myocardial infarction, reduced restenosis after coronary angioplasty, improved the quality and function of liver grafts, as well as outcome of intestinal and cerebral ischemic attacks. However, it is crucial to be mindful that like other therapeutic armentarium, the efficacy of antioxidant gene transfer requires extensive preclinical investigation before it can be used in patients, and that it may have unanticipated short- or long-term adverse effects. Thus, it is critical to balance between the therapeutic benefits and potential risks, to develop disease-specific antioxidant gene transfer strategies, to deliver the therapy with an optimal time window and in a safe manner. This review attempts to provide the rationale, the most effective approaches and the potential hurdles of available antioxidant gene transfer approaches for ischemic injury in various organs, as well as the possible directions of future preclinical and clinical investigations of this highly promising therapeutic modality.

Image-guided, lobe-specific hydrodynamic gene delivery to swine liver

Image-guided, lobe-specific hydrodynamic gene delivery to liver was assessed in pigs. The procedure involved image-guided insertion of a balloon catheter to the hepatic vein of the selected lobe from the jugular vein and hydrodynamic injection of plasmid DNA using a newly developed computer-controlled injection device. We demonstrated that the impact of the procedure was regional with minimal effects on neighboring lobes. Level of gene expression resulted from the procedure was 10(7) relative light units (RLU)/mg in the targeted lobes and 10(2)-10(5) RLU/mg in the nontargeted lobes 4 hours after hydrodynamic injection of pCMV-Luc plasmids. Occlusion of blood flow in the inferior vena cava (IVC) or IVC plus portal vein (PV) was effective in elevating hydrodynamic pressure in the targeted vasculature but did not enhance gene delivery efficiency. Physiological examination on pigs with IVC occlusion revealed transient decreases of blood pressure and respiration rate. Removal of occlusion from IVC resulted in a rapid and transient increase in heart rate. Occlusion of the PV and hepatic vein showed no effect on physiological and cardiac activities. No major changes in serum composition were observed. These results suggest that (i) image-guided, lobe-specific hydrodynamic procedure is effective for regional gene delivery to liver, (ii) blockade in IVC should be avoided for hydrodynamic gene delivery to the liver, and (iii) clinical application of hydrodynamic gene delivery to liver is feasible.

Physical approaches for nucleic acid delivery to liver

The liver is a key organ for numerous metabolic pathways and involves many inherited diseases that, although being different in their pathology, are often caused by lack or overproduction of a critical gene product in the diseased cells. In principle, a straightforward method to fix such problem is to introduce into these cells with a gene-coding sequence to provide the missing gene product or with the nucleic acid sequence to inhibit production of the excessive gene product. Practically, however, success of nucleic acid-based pharmaceutics is dependent on the availability of a method capable of delivering nucleic acid sequence in the form of DNA or RNA to liver cells. In this review, we will summarize the progress toward the development of physical methods for nucleic acid delivery to the liver. Emphasis is placed on the mechanism of action, pros, and cons of each method developed so far. We hope the information provided will encourage new endeavor to improve the current methodologies or develop new strategies that will lead to safe and effective delivery of nucleic acids to the liver.