Prolonged transgene expression in glomeruli using an EBV replicon vector system combined with HVJ liposomes

Renal Artery Catheterization for Microcapsules' Targeted Delivery to the Mouse Kidney

The problem of reducing the side effects associated with drug distribution throughout the body in the treatment of various kidney diseases can be solved by effective targeted drug delivery. The method described herein involves injection of a drug encapsulated in polyelectrolyte capsules to achieve prolonged local release and long-term capillary retention of several hours while these capsules are administered via the renal artery. The proposed method does not imply disruption (puncture) of the renal artery or aorta and is suitable for long-term chronic experiments on mice. In this study, we compared how capsule size and dosage affect the target kidney blood flow. It has been established that an increase in the diameter of microcapsules by 29% (from 3.1 to 4.0 μm) requires a decrease in their concentration by at least 50% with the same suspension volume. The photoacoustic method, along with laser speckle contrast imaging, was shown to be useful for monitoring blood flow and selecting a safe dose. Capsules contribute to a longer retention of a macromolecular substance in the target kidney compared to its free form due to mechanical retention in capillaries and slow impregnation into surrounding tissues during the first 1-3 h, which was shown by fluorescence tomography and microscopy. At the same time, the ability of capillaries to perform almost complete "self-cleaning" from capsular shells during the first 12 h leads to the preservation of organ tissues in a normal state. The proposed strategy, which combines endovascular surgery and the injection of polymer microcapsules containing the active substance, can be successfully used to treat a wide range of nephropathies.

Gene Transfer Using Nonviral Delivery Systems

In peritoneal dialysis, loss of peritoneal function is a major factor in treatment failure. The alterations in peritoneal function are related to structural changes in the peritoneal membrane, including peritoneal sclerosis with increased extracellular matrix. Although peritoneal sclerosis is considered reversible to some extent through peritoneal rest, which improves peritoneal function and facilitates morphological changes, there has been no therapeutic intervention and no drug against the development and progression of peritoneal sclerosis. Using recent biotechnological advances in genetic engineering, a strategy based on genetic modification of the peritoneal membrane could be a potential therapeutic maneuver against peritoneal sclerosis and peritoneal membrane failure. Before this gene therapy may be applied clinically, a safe and effective gene delivery system as well as the selection of a gene therapy method must be established. There are presently two kinds of gene transfer vectors: viral and nonviral. Viral vectors are used mainly as a gene delivery system in the field of continuous ambulatory peritoneal dialysis research; however, they have several problems such as immunogenicity and toxicity. On the other hand, nonviral vectors have several advantages over viral vectors. We review here gene transfer using nonviral vector systems in the peritoneum: electroporation, liposomes, and cationized gelatin microspheres. In the field of peritoneal dialysis, gene therapy research using nonviral vectors is presently limited. Improvement in delivery methods together with an intelligent design of targeted genes has brought about large degrees of enhancement in the efficiency, specificity, and temporal control of nonviral vectors.

Liposome-mediated Gene Therapy in the Kidney

Gene therapy directed to the kidney has been attempted to improve renal disorders such as inherited kidney diseases and common renal diseases that cause interstitial fibrosis, tubular atrophy, and glomerulosclerosis. Viral and non-viral vectors have been tried and been modulated to obtain sufficient transgene expression. However, gene delivery to the kidney is usually difficult because of characteristics of renal cell biology. Among non-viral vectors, the liposome system is a promising procedure for kidney-targeted gene therapy. Using cationic liposome, tubular cells were effectively transduced by retrograde injection of liposome/cDNA complex. Although transgene expression was reportedly modest using cationic liposomes, this method improved renal disease models such as carbonic anhydrase II deficiency and unilateral ureteral obstruction. In contrast, HVJ-liposome system is an effective transfection method to glomerular cells using intra-renal arterial infusion and improved glomerular disease models such as glomerulonephritis and glomerulosclerosis. In addition, intra-renal pelvic injection of DNA by HVJ-liposome system showed transgene expression in interstitial fibroblasts. In kidney-targeted gene therapy, liposome-mediated gene transfer is an attractive method because of its simplicity and reduced toxicity. In spite of modest transgene expression, several renal disease models were successfully modulated by liposome system. Although one limitation of liposome-mediated gene delivery is the duration of transgene expression, the liposome/cDNA complex can be repeatedly administered due to the absence of an immune response.

Adenovirus-mediated gene transfer and lipoprotein-mediated protein delivery of plasma PAF-AH ameliorates proteinuria in rat model of glomerulosclerosis

Oxidative stress has been proposed to play a crucial role in glomerulosclerosis, although its in vivo demonstration has proved taxing given the difficulty of inducing gene expression in specific renal cells. In this study, we examined whether the liver-directed expression of plasma platelet-activating factor acetylhydrolase (PAF-AH) would affect the glomerular pathophysiology in Imai rats, an animal model for glomerulosclerosis. Adenovirus-mediated liver-directed gene delivery of human PAF-AH resulted in a significant increase in plasma PAF-AH activity, which was detected almost exclusively on HDL. Histological examination of rats overexpressing PAF-AH showed not only the deposition of PAF-AH in mesangial cells, but also a reduction in hydroxynonenal and matrix protein content in the glomeruli. In situ hybridization analysis was negative for human PAF-AH mRNA in the kidney, while injection of HDL abundant in PAF-AH resulted in the deposition of PAF-AH in mesangial cells. Urine protein levels did not increase in rats overexpressing PAF-AH, while those of control rats increased significantly with age. This study provides direct evidence of the in vivo role of an enzyme that degrades lipid peroxides during the progression of glomerulosclerosis. Adenovirus-mediated extrarenal gene expression and lipoprotein-mediated glomeruli-targeted protein delivery promise to be a novel therapeutic approach to glomerulosclerosis.

Liver-directed gene therapy of diabetic rats using an HVJ-E vector containing EBV plasmids expressing insulin and GLUT 2 transporter

Insulin gene therapy in clinical medicine is currently hampered by the inability to regulate insulin secretion in a physiological manner, the inefficiency with which the gene is delivered, and the short duration of gene expression. To address these issues, we injected the liver of streptozotocin-induced diabetic rats with hemagglutinating virus of Japan-envelope (HVJ-E) vectors containing Epstein-Barr virus (EBV) plasmids encoding the genes for insulin and the GLUT 2 transporter. Efficient delivery of the genes was achieved with the HVJ-E vector, and the use of the EBV replicon vector led to prolonged hepatic gene expression. Blood glucose levels were normalized for at least 3 weeks as a result of the gene therapy. Cotransfection of GLUT 2 with insulin permitted the diabetic rats to regulate their blood glucose levels upon exogenous glucose loading in a physiologically appropriate manner and improved postprandial glucose levels. Moreover, cotransfection with insulin and GLUT 2 genes led to in vitro glucose-stimulated insulin secretion that involved the closure of K(ATP) channels. The present study represents a new way to efficiently deliver insulin gene in vivo that is regulated by ambient glucose level with prolonged gene expression. This may provide a basis to overcome limitations of insulin gene therapy in humans.

Electroporation-mediated HGF gene transfection protected the kidney against graft injury

The annual rate of kidney graft loss caused by chronic allograft nephropathy (CAN) has not improved over the past decade. Recent reports suggest that acute renal ischemia results in development of CAN. The goal of the present study was to assess the renoprotective potential and safety of hepatocyte growth factor (HGF) gene transfer using a porcine kidney transplant warm ischemia injury model. Following left porcine kidney removal, 10 min of warm ischemic injury was intentionally induced. Next, the HGF expression vector or vehicle was infused into the renal artery with the renal vein clamped ex vivo, and electric pulses were discharged using bathtub-type electrodes. Kidney grafts were then transplanted after removing the right kidney. Histopathological examination of vehicle-transfected kidney transplant revealed initial tubular injury followed by tubulointerstitial fibrosis. In contrast, HGF-transfected kidneys showed no initial tubular damage and no interstitial fibrosis at 6 months post-transplant. We conclude that electroporation-mediated ex vivo HGF gene transfection protects the kidney against graft injury in a porcine model.

Approaches and methods in gene therapy for kidney disease

Renal gene therapy may offer new strategies to treat diseases of native and transplanted kidneys. Several experimental techniques have been developed and employed using nonviral, viral, and cellular vectors. The most efficient vector for in vivo transfection appears to be adenovirus. Glomeruli, blood vessels, interstitial cells, and pyelum can be transfected with high efficiency. In addition, electroporation and microbubbles with ultrasound, both being enhanced naked plasmid techniques, offer good opportunities. Trapping of mesangial cells into the glomeruli as well as natural targeting of monocytes or macrophages to inflamed kidneys are elegant methods for site-specific delivery of genes. For gene therapy in kidney transplantation, hemagglutinating virus of Japan liposomes are efficient vectors for tubular transfection, whereas enhanced naked plasmid techniques are suitable for glomerular transfection. However, adenovirus offers the best opportunities in a renal transplantation setup because varying parameters of graft perfusion allows targeting of different cell types. In renal grafts, lymphocytes can be used for selective targeting to sites of inflammation. In conclusion, for both in vivo and ex vivo renal transfection, enhanced naked plasmids and adenovirus offer the best perspectives for effective clinical application. Moreover, the development of safer, nonimmunogenic vectors and the large-scale production could make clinical renal gene therapy a realistic possibility for the near future.

Reduced toxicity of F-deficient Sendai virus vector in the mouse fetus

Current concerns over insertional mutagenesis by retroviral vectors mitigate investigations into alternative, potentially persistent gene therapy vector systems not dependent on genomic integration, such as Sendai virus vectors (SeVV). Prenatal gene therapy requires efficient gene delivery to several tissues, which may not be achievable by somatic gene transfer to the adult. Initially, to test the potential and tropism of the SeVV for gene delivery to fetal tissues, first-generation (replication- and propagation-competent) recombinant SeVV, expressing beta-galactosidase was introduced into late gestation immunocompetent mice via the amniotic and peritoneal cavities and the yolk sac vessels. At 2 days, this resulted in very high levels of expression particularly in the airway epithelium, mesothelium and vascular endothelium, respectively. However, as expected, substantial vector toxicity was observed. The efficiency of gene transfer and the level of gene expression were then examined using a second-generation SeVV. The second generation was developed to be still capable of cytoplasmic RNA replication and therefore high-level gene expression, but incapable of vector spread due to lack of the gene for viral F-protein. Vector was introduced into the fetal amniotic and peritoneal cavities, intravascularly, intramuscularly and intraspinally; at 2 days, expression was observed in the airway epithelia, peritoneal mesothelia, unidentified cells in the gut wall, locally at the site of muscle injection and in the dorsal root ganglia, respectively. Mortality was dramatically diminished compared with the first-generation vector.

Inhibition of renal fibrosis by gene transfer of inducible Smad7 using ultrasound-microbubble system in rat UUO model

TGF-beta is a key mediator in renal fibrosis. Kidney-targeted gene therapy with anti-TGF-beta strategies is expected to have therapeutic potential, but this has been hampered by concerns over the safety and practicability of viral vectors and the inefficiency of nonviral transfection techniques. The present study explored the potential role of TGF-beta/Smad signaling in renal fibrosis in vivo and developed a safe and effective gene therapy to specifically block TGF-beta signaling and renal fibrosis in a rat unilateral ureteral obstruction (UUO) model by transferring a doxycycline-regulated Smad7 gene or control empty vectors using an ultrasound-microbubble (Optison)-mediated system. The Smad7 transgene expression was tightly controlled by addition of doxycycline in the daily drinking water. Groups of six rats were sacrificed at day 7, and the transfection rate, Smad7 transgene expression, and tubulointerstitial fibrosis including alpha-smooth muscle actin and collagen matrix mRNA and protein expression were determined. Compared with the non-ultrasound treatment, the combination of ultrasound with Optison largely increased the transfection rate of FITC-ODN and Smad7 transgene expression up to a 1000-fold, and this was found in all kidney tissues. Compared with normal rats, Smad7 expression within the UUO kidney was significantly reduced, and this was associated with up to a sixfold increase in Smad2 and Smad3 activation and severe tubulointerstitial fibrosis. In contrast, treatment with inducible Smad7 resulted in a fivefold increase in Smad7 expression with complete inhibition of Smad2 and Smad3 activation and tubulointerstitial fibrosis in terms of tubulointerstitial myofibroblast accumulation (85% downward arrow ) and collagen I and III mRNA and protein expression (60 to 70% downward arrow ). In conclusion, the ultrasound-mediated inducible Smad7 gene transfer is a safe, effective, and controllable gene therapy. TGF-beta-mediated renal fibrosis is regulated positively by Smad2/3, but negatively by Smad7. Target blockade of TGF-beta/Smad signaling by expression of Smad7 may provide a new therapeutic potential for renal fibrosis.

Non-viral gene delivery in skeletal muscle: a protein factory

Ever since the publication of the first reports in 1990 using skeletal muscle as a direct target for expressing foreign transgenes, an avalanche of papers has identified a variety of proteins that can be synthesized and correctly processed by skeletal muscle. The impetus to the development of such applications is not only amelioration of muscle diseases, but also a range of therapeutic applications, from immunization to delivery of therapeutic proteins, such as clotting factors and hormones. Although the most efficient way of introducing transgenes into muscle fibres has been by a variety of recombinant viral vectors, there are potential benefits in the use of non-viral vectors. In this review we assess the recent advances in construction and delivery of naked plasmid DNA to skeletal muscle and highlight the options available for further improvements to raise efficiency to therapeutic levels.

Intra-arterial delivery of p53-containing adenoviral vector into experimental brain tumors

Human tumor xenografts established in athymic rat brains were used to determine the feasibility of intravascular delivery of tumor suppressor genes to brain tumors. Both tumor size and number were compared to characterize the effect of tumor burden on tumor transduction efficacy by a control LacZ-containing adenoviral vector. Experiments with tumors grown in vivo for either 3, 5, or 7 days demonstrated that 5-day-old tumors provided the best target for vector infection and transgene expression by this mode of administration. Intra-arterial mannitol facilitated transduction efficiency. Tumor burden did not seem to affect transduction, while tumor location appeared to be an important factor. Based on these results, intra-arterial infusion of a p53-containing adenoviral vector was carried out and resulted in significant retardation of brain tumor growth 3 days after administration. Effects at longer time points were not as significant. These findings indicate that intra-arterial administration of adenoviral vectors containing p53 is efficient and can result in changes in tumor size, but that long-term control of tumor growth may require multiple adenoviral treatments.

EBV replicon vector system enhances transgene expression in vivo: applications to cancer gene therapy

BACKGROUND

A major limitation of current cancer gene therapies is low and transient expression of the therapeutic gene. For long-term expression of transgenes in vivo, an Epstein-Barr virus (EBV) replicon vector has been developed. The present study examines the effect of the EBV replicon vector system and its application to a suicide gene therapy for melanoma in mice.

METHODS

An EBV replicon vector system, pEBc, consisting of EBV nuclear antigen-1 (EBNA-1) and the origin of latent viral DNA replication, oriP, was used to express either the luciferase gene or the herpes simplex virus (HSV) thymidine kinase (TK) gene. The expression vector was introduced in vivo into melanoma tumor masses in mice by means of HVJ-cationic liposomes. The time-course of gene expression and the anticancer effect of the EBV replicon vector were investigated in comparison with pcLuc, which lacks the EBV components.

RESULTS

Luciferase expression was sustained in both cultured cells and melanoma masses by pEBc but not by pcLuc. The luciferase expression level in melanoma masses was higher by pEBcLuc than by pcLuc, although Southern blot analysis showed the number of copies of pEBcLuc retained in the melanoma masses to be fewer than that of pcLuc. The effectiveness of EBV replicon vector on suicide gene therapy of melanoma in mice was also demonstrated.

CONCLUSION

The EBV replicon vector appears useful for cancer gene therapy. Analysis of the transgene in tumors suggests that the EBV replicon system may be responsible for efficient transcription but not retention of the transgene.