Infection of intact human islets by a lentiviral vector

Highly efficient ex vivo lentiviral transduction of primary human pancreatic exocrine cells

The lack of efficient gene transfer methods into primary human pancreatic exocrine cells hampers studies on the plasticity of these cells and their possible role in beta cell regeneration. Therefore, improved gene transfer protocols are needed. Lentiviral vectors are widely used to drive ectopic gene expression in mammalian cells, including primary human islet cells. Here we aimed to optimize gene transfer into primary human exocrine cells using modified lentiviral vectors or transduction conditions. We evaluated different promoters, viral envelopes, medium composition and transduction adjuvants. Transduction efficiency of a reporter vector was evaluated by fluorescence microscopy and flow cytometry. We show that protamine sulfate-assisted transduction of a VSV-G-pseudotyped vector expressing eGFP under the control of a CMV promoter in a serum-free environment resulted in the best transduction efficiency of exocrine cells, reaching up to 90% of GFP-positive cells 5 days after transduction. Our findings will enable further studies on pancreas (patho)physiology that require gene transfer such as gene overexpression, gene knockdown or lineage tracing studies.

Translational assessment of a genetic engineering methodology to improve islet function for transplantation

Background

The functional quality of insulin-secreting islet beta cells is a major factor determining the outcome of clinical transplantations for diabetes. It is therefore of importance to develop methodological strategies aiming at optimizing islet cell function prior to transplantation. In this study we propose a synthetic biology approach to genetically engineer cellular signalling pathways in islet cells.

Methods

We established a novel procedure to modify islet beta cell function by combining adenovirus-mediated transduction with reaggregation of islet cells into pseudoislets. As a proof-of-concept for the genetic engineering of islets prior to transplantation, this methodology was applied to increase the expression of the V1b receptor specifically in insulin-secreting beta cells. The functional outcomes were assessed in vitro and in vivo following transplantation into the anterior chamber of the eye.

Findings

Pseudoislets produced from mouse dissociated islet cells displayed basic functions similar to intact native islets in terms of glucose induced intracellular signalling and insulin release, and after transplantation were properly vascularized and contributed to blood glucose homeostasis. The synthetic amplification of the V1b receptor signalling in beta cells successfully modulated pseudoislet function in vitro. Finally, in vivo responses of these pseudoislet grafts to vasopressin allowed evaluation of the potential benefits of this approach in regenerative medicine.

Interpretation

These results are promising first steps towards the generation of high-quality islets and suggest synthetic biology as an important tool in future clinical islet transplantations. Moreover, the presented methodology might serve as a useful research strategy to dissect cellular signalling mechanisms of relevance for optimal islet function.

Retrovirally Transferred Genes Inhibit Apoptosis in an Insulin-Secreting Cell Line: Implications for Islet Transplantation

The transplantation of pancreatic islets for the treatment of type I diabetes is hindered by the enormous loss of cells due to early apoptotic events. Genetic engineering of islets with cytoprotective genes is an important strategy aimed to enhance the survival of these cells in the transplant setting. The present study was designed to evaluate and compare the effects of five genes on a cell line derived from insulin-producing β-cells, NIT-1. Cells were transduced using a Maloney murine leukemia virus (MLV) vector coding for yellow fluorescent protein (YFP) and for one of the following antiapoptotic genes: cFLIP, FADD-DN, BcL-2, PI-9, and ICAM-2. These genes were able to protect NIT-1 cells from cytokine-induced apoptosis to varying degrees ranging from no protection to significant protection equivalent to an optimal dose of a chemical caspase inhibitor. The data demonstrate that cFLIP, FADD-DN, and PI-9 are significantly more effective in protecting NIT-1 cells than BcL-2 and ICAM-2. Additionally, the data show that despite its weak in vitro inhibition of caspase-3, PI-9 affords significant protection against TNF-α-induced apoptosis in these cells. These genes may be ideal candidates to augment islet survival following transplantation.

Gene Transfection and Expression of Transforming Growth Factor-β1 in Nonobese Diabetic Mouse Islets Protects β-Cells in Syngeneic Islet Grafts from Autoimmune Destruction

Nonobese diabetic (NOD) mice develop diabetes and destroy syngeneic islet grafts through an autoimmune response. Because transforming growth factor (TGF)-β1 downregulates immune responses, we tested whether overexpression of TGF-β1 by gene transfection of NOD mouse islets could protect β-cells in islet grafts from autoimmune destruction. NOD mouse islet cells were transfected with an adenoviral DNA expression vector encoding porcine latent TGF-β1 (Ad TGF- β1) or the adenoviral vector alone (control Ad vector). The frequency of total islet cells expressing TGF-1 protein was increased from 12±1% in control Ad vector-transfected cells to 89 ± 4% in Ad TGF-β1-transfected islet cells, and the frequency of β-cells that expressed TGF-β1 was increased from 12 ± 1% to 60 ± 7%. Also, secretion of TGF-β1 was significantly increased in islets that overexpressed TGF-β1. Ad TGF-β1-transfected NOD mouse islets that overexpressed TGF-β1 prevented diabetes recurrence after transplantation into diabetic NOD mice for a median of 22 days compared with only 7 days for control Ad vector-transfected islets (p = 0.001). Immunohistochemical examination of the islet grafts revealed significantly more TGF-β1+ cells and insulin+ cells and significantly fewer CD45+ leukocytes in Ad TGF-β1-transfected islet grafts. Also, islet β-cell apoptosis was significantly decreased whereas apoptosis of graft-infiltrating leukocytes was significantly increased in Ad TGF-β1-transfected islet grafts. These observations demonstrate that overexpression of TGF-β1, by gene transfection of NOD mouse islets, protects islet β-cells from apoptosis and autoimmune destruction and delays diabetes recurrence after islet transplantation.

A Simple High Efficiency Intra-Islet Transduction Protocol Using Lentiviral Vectors

Successful normalization of blood glucose in patients transplanted with pancreatic islets isolated from cadaveric donors established the proof-of-concept that Type 1 Diabetes Mellitus is a curable disease. Nonetheless, major caveats to the widespread use of this cell therapy approach have been the shortage of islets combined with the low viability and functional rates subsequent to transplantation. Gene therapy targeted to enhance survival and performance prior to transplantation could offer a feasible approach to circumvent these issues and sustain a durable functional β-cell mass in vivo. However, efficient and safe delivery of nucleic acids to intact islet remains a challenging task. Here we describe a simple and easy-to-use lentiviral transduction protocol that allows the transduction of approximately 80 % of mouse and human islet cells while preserving islet architecture, metabolic function and glucose-dependent stimulation of insulin secretion. Our protocol will facilitate to fully determine the potential of gene expression modulation of therapeutically promising targets in entire pancreatic islets for xenotransplantation purposes.

Simultaneous silencing of multiple RB and p53 pathway members induces cell cycle reentry in intact human pancreatic islets

Background

Human pancreatic islet structure poses challenges to investigations that require specific modulation of gene expression. Yet dissociation of islets into individual cells destroys cellular interactions important to islet physiology. Approaches that improve transient targeting of gene expression in intact human islets are needed in order to effectively perturb intracellular pathways to achieve biological effects in the most relevant tissue contexts.

Results

Electroporation of intact human cadaveric islets resulted in robust and specific suppression of gene expression. Two genes were simultaneously suppressed by 80% from baseline levels. When multiple (up to 5) genes were simultaneously targeted, effective suppression of 3 of 5 genes occurred. Enzymatic pretreatment of islets was not required. Simultaneous targeting of RB and p53 pathway members resulted in cell cycle reentry as measured by EDU incorporation in 10% of islet nuclei.

Conclusions

At least three genes can be effectively suppressed simultaneously in cultured intact human pancreatic islets without disruption of islet architecture or overt alterations in function. This enabled the effective modulation of two central growth control pathways resulting in the phenotypic outcome of cell cycle reentry in postmitotic islet cells. Transient exposure to multiple siRNAs is an effective approach to modify islets for study with the potential to aid clinical applications.

Osteogenic differentiation of human periodontal ligament cells after transfection with recombinant lentiviral vector containing follicular dendritic cell secreted protein

BACKGROUND AND OBJECTIVE

Follicular dendritic cell secreted protein (FDC-SP), has been identified in human periodontal ligament (PDL) in a recent study. It is suggested that the expression of FDC-SP might be associated with the osteogenic differentiation and mineralization of human periodontal ligament cells (hPDLCs). However, the intrinsic mechanism regarding this is still unclear. The aim of this study was to establish hPDLCs with safe and efficient overexpression of FDC-SP and to elucidate the influence of FDC-SP transfection on hPDLC osteogenesis in periodontal regeneration.

MATERIAL AND METHODS

We first applied a recombinant lentiviral vector containing FDC-SP to transfect hPDLCs via different multiplicity of infection (MOI) levels (1, 10, 20, 50 and 100). Western blot was performed to confirm the expression of FDC-SP. MTT assay was employed to evaluate the proliferation status of transfected cells. Then, the extent of osteogenic differentiation was investigated by simultaneous monitoring of alkaline phosphatase (ALP) activity assessment, immunofluorescent staining, the expression patterns of osteoblastic markers and mineralization staining.

RESULTS

We found that hPDLCs transfected via MOI 20, 50 and 100 exhibited expression of FDC-SP protein compared with MOI 1 and 10. There was no significant effect of FDC-SP transfection (at different MOI levels of 1, 10 and 20) on the proliferation of hPDLCs, whereas higher MOI levels (50 and 100) inhibited cell proliferation ability. In addition, ALP activity decreased significantly in FDC-SP-transfected hPDLCs at day 7. When stained with alizarin red, cells overexpressing FDC-SP formed less mineralized nodules at 21 d post-induction of differentiation, compared with the control cultures. Osteogenic inhibition was also confirmed by ALP immunostaining. Moreover, mRNA expression levels of osteoblastic markers decreased after FDC-SP transfection, which were in accordance with western blot results.

CONCLUSION

Our data suggest that MOI 20 is optimal to transfect hPDLCs, which achieves safe and efficient overexpression of FDC-SP in transfected cells. Moreover, FDC-SP overexpression inhibits osteogenic differentiation of hPDLCs. The present study contributes to a better understanding of the biological functions governing FDC-SP-induced hPDLC differentiation.

β cell protection by inhibition of iNOS through lentiviral vector-based strategies

Cytoprotective gene transfer to pancreatic islet β cell s may prove useful in preventing their destruction and prolonging islet graft survival after transplantation in patients with type 1 diabetes mellitus. A host of therapeutically relevant transgenes may potentially be incorporated into an appropriate gene delivery vehicle and used for islet modification. To examine this, we utilised a robust model of cytokine-induced β cell pathophysiology. Using this model, it is clear that antioxidant gene transfer confers no cytoprotective benefit. In contrast, we demonstrated that gene-based approaches to inhibit the activation of NF-κBNF-κB following cytokine exposure harbours therapeutic utility in preserving islet β cell viability in the face of cytokine toxicity. We identified that NF-κB-dependent induction of iNOSiNOS is a critical determinant of β cell fate following cytokine exposure. Having identified the pivotal role of iNOS activation in cytokine-induced β cell pathophysiology, lentiviral vectors may be used to efficiently deliver small interfering RNARNA molecules to confer efficient iNOS gene silencing. We have shown that lentiviral vector-based shRNA delivery holds significant promise in preserving β cell viability following cytotoxic cytokine exposure.

Genetic vaccination for re-establishing T-cell tolerance in type 1 diabetes

Type 1 diabetes (T1D) is a T-cell mediated autoimmune disease resulting in the destruction of the insulin-secreting β cells. Currently, there is no established clinical approach to effectively suppress long-term the diabetogenic response. Genetic-based vaccination offers a general strategy to reestablish β-cell specific tolerance within the T-cell compartment. The transfer of genes encoding β-cell autoantigens, anti-inflammatory cytokines and/or immunomodulatory proteins has proven to be effective at preventing and suppressing the diabetogenic response in animal models of T1D. The current review will discuss genetic approaches to prevent and treat T1D with an emphasis on plasmid DNA- and adeno-associated virus-based vaccines.

RNA interference for improving the outcome of islet transplantation

Islet transplantation has the potential to cure type 1 diabetes. Despite recent therapeutic success, it is still not common because a large number of transplanted islets get damaged by multiple challenges including instant blood mediated inflammatory reaction, hypoxia/reperfusion injury, inflammatory cytokines, and immune rejection. RNA interference (RNAi) is a novel strategy to selectively degrade target mRNA. The use of RNAi technologies to downregulate the expression of harmful genes has the potential to improve the outcome of islet transplantation. The aim of this review is to gain a thorough understanding of biological obstacles to islet transplantation and discuss how to overcome these barriers using different RNAi technologies. This eventually will help improve islet survival and function post transplantation. Chemically synthesized small interferring RNA (siRNA), vector based short hairpin RNA (shRNA), and their critical design elements (such as sequences, promoters, and backbone) are discussed. The application of combinatorial RNAi in islet transplantation is also discussed. Last but not the least, several delivery strategies for enhanced gene silencing are discussed, including chemical modification of siRNA, complex formation, bioconjugation, and viral vectors.

Efficient gene delivery and silencing of mouse and human pancreatic islets

Background

In view of the importance of beta cells in glucose homeostasis and the profound repercussions of beta cell pathology on human health, the acquisition of tools to study pancreatic islet function is essential for the design of alternative novel therapies for diabetes. One promising approach toward this goal involves the modification of gene expression profile of beta cells.

Results

This study describes a new method of gene and siRNA delivery into human pancreatic islets by microporation technology. We demonstrated that mild islet distention with accutase greatly enhanced the transfection efficiency without compromising in vitro function (secretion, apoptosis and viability). As an example, the recently identified gene involved in type 2 diabetes, ZnT8, can be over-expressed or silenced by RNA interference using this technology. Microporation can also be used on rodent islets.

Conclusions

Taken together, our results demonstrate that microporation technology can be used to modify gene expression in whole rodent and human islets without altering their in vitro function and will be key to the elucidation of the factors responsible for proper islet function.

Genetic modification of cells for transplantation

Progress in gene therapy has produced promising results that translate experimental research into clinical treatment. Gene modification has been extensively employed in cell transplantation. The main barrier is an effective gene delivery system. Several viral vectors were utilized in end-stage differentiated cells. Recently, successful applications were described with adenovirus-associated vectors. As an alternative, embryonic stem cell- and stem cell-like systems were established for generation of tissue-specified gene-modified cells. Owing to the feasibility for genetic manipulations and the self-renewing potency of these cells they can be used in a way enabling large-scale in vitro production. This approach offers the establishment of in vitro cell culture systems that will deliver sufficient amounts of highly purified, immunoautologous cells suitable for application in regenerative medicine. In this review, the current technology of gene delivery systems to cells is recapitulated and the latest developments for cell transplantation are discussed.

Both HIV- and EIAV-based lentiviral vectors mediate gene delivery to pancreatic cancer cells and human pancreatic primary patient xenografts

Few effective treatments for pancreatic cancer exist, especially for patients with advanced disease. Gene therapy alone, or combined with current treatments, offers an alternative approach. Here we examined the potential of primate and nonprimate lentivectors to mediate gene delivery to this cancer type. VSV-G pseudotyped lentivectors based on human immunodeficiency type-1 virus (HIV-1) and equine infectious anemia virus (EIAV), containing the enhanced green fluorescent protein (EGFP) reporter gene were prepared and characterized for titer and RNA content. Vector-mediated gene delivery was examined in five pancreatic cancer cell lines in vitro, and in MiaPaCa-2 cells as well as in five human primary patient biopsies xenografted subcutaneously in nude mice. While individual cell lines showed differential sensitivities to transduction with lentivectors, all cell lines were successfully transduced with both vector types. Similarly, both vectors transduced MiaPaCa-2 and all of the human primary patient xenografts. We observed 6-29% transduction with HIV-based vectors (n=3 xenografts) and 1.8-30% with EIAV-based vectors (n=4 xenografts). Long-term EIAV-mediated gene expression was recorded in cell lines for up to 6 months. We conclude that these vectors have potential as mediators of clinical gene therapy for pancreatic cancer treatment. Moreover, they are useful laboratory research tools for pancreatic cancer research.

Efficient and persistent transduction of exocrine and endocrine pancreas by adeno-associated virus type 8

Efficient delivery of therapeutic proteins into the pancreas represents a major obstacle to gene therapy of pancreatic disorders. The current study compared the efficiency of recombinant lentivirus and adeno-associated virus (AAV) serotypes 1, 2, 5, 8 vectors delivered by intrapancreatic injection for gene transfer in vivo. Our results indicate that lentivirus and AAV 1, 2, 8 are capable of transducing pancreas with the order of efficiency AAV8 >>AAV1 > AAV2 >/= lentivirus, whereas AAV5 was ineffective. AAV8 resulted in an efficient, persistent (150 days) and dose-dependent transduction in exocrine acinar cells and endocrine islet cells. Pancreatic ducts and blood vessels were also transduced. Extrapancreatic transduction was restricted to liver. Leukocyte infiltration was not observed in pancreas and blood glucose levels were not altered. Thus, AAV8 represents a safe and effective vehicle for therapeutic gene transfer to pancreas in vivo.

Evaluation of promoters for driving efficient transgene expression in neonatal porcine islets

There is considerable interest in the viral modification of insulin-producing islets, including porcine islets, in the context of islet xenotransplantation to treat type 1 diabetes. Adenovirus (Adv) gene delivery offers the potential to modify pre-transplant islets for enhanced survival. Modifications include transfer of cytoprotective molecules to ensure islet survival immediately post-transplant, and molecules to dampen the immune system and prevent chronic islet graft rejection. In this study, we compared different promoters (three promiscuous and two tissue-specific promoters) for their efficiency in driving gene expression in neonatal pig islet tissue after Adv delivery. We also compared the efficiency of these promoters in adult islets from mouse and human pancreata. We observed that the promiscuous cytomegalovirus promoter was the most potent, eliciting high luciferase expression in neonatal pig islets, as well as in human and mouse islets. In contrast, the mammalian EF1-alpha promoter educed comparatively intermediate gene expression. The mouse major histocompatibility complex class I promoter H-2K(b) and the pancreatic-specific promoters insulin and human pdx-1 (area II) performed poorly in islets from all three species. This has important implications for the generation of modified neonatal pig islets for transplantation into humans.

Biological and Biomaterial Approaches for Improved Islet Transplantation

Islet transplantation may be used to treat type I diabetes. Despite tremendous progress in islet isolation, culture, and preservation, the clinical use of this modality of treatment is limited due to post-transplantation challenges to the islets such as the failure to revascularize and immune destruction of the islet graft. In addition, the need for lifelong strong immunosuppressing agents restricts the use of this option to a limited subset of patients, which is further restricted by the unmet need for large numbers of islets. Inadequate islet supply issues are being addressed by regeneration therapy and xenotransplantation. Various strategies are being tried to prevent beta-cell death, including immunoisolation using semipermeable biocompatible polymeric capsules and induction of immune tolerance. Genetic modification of islets promises to complement all these strategies toward the success of islet transplantation. Furthermore, synergistic application of more than one strategy is required for improving the success of islet transplantation. This review will critically address various insights developed in each individual strategy and for multipronged approaches, which will be helpful in achieving better outcomes.

Long-term gene expression and metabolic control exerted by lentivirus-transduced pancreatic islets

BACKGROUND

Genetic modification of non-human islets before transplantation may provide means by which they can escape immunity and, thus, be used in a human host. To accomplish this, efficient gene transfer methods are needed. Lentiviral vectors are transgene vehicles capable of stably transducing a variety of primary, post-mitotic cells including islets.

METHODS

We investigated whether lentiviral transduction impaired rat pancreatic islet function long term. Following transduction, the gross morphology, viability and in vitro functionality of islets were evaluated by microscopy, adenylate nucleotide and insulin secretion assays, respectively. Further, in vivo functionality of transduced islets was assessed by transplanting the islets under the kidney capsule of diabetic nude mice.

RESULTS

All transduced islets contained green fluorescent protein (GFP)-positive cells. In single cell suspensions prepared from transduced islets, 33+/-8% (n = 3) of dispersed islet cells were GFP-positive. The ADP/ATP ratio was 0.07+/-0.01 for transduced islets and 0.06+/-0.01 for controls (normal range <0.11). No morphological changes were observed in transduced islets. Further, basal insulin secretion was comparable between the two islet groups. When transduced and non-transduced islets were challenged with insulin secretagogues, they showed similar increases in insulin release. Transduced and non-transduced islets were equally effective in normalizing blood glucose when transplanted into diabetic nude mice. Euglycemia was maintained for 8 weeks until the graft-bearing kidney was removed. Intense green fluorescence was seen in removed islet grafts. Histology revealed preserved islet morphology, with abundant insulin-producing cells, few apoptotic cells and infiltrating leukocytes in both transduced and non-transduced grafts.

CONCLUSIONS

Lentivirus transduction does not affect islet morphology or function. Lentiviral vectors will allow genetic modifications to be performed in islets before transplantation--modifications that can improve engraftment and/or prevent xenograft rejection.

In vivo Gene Transfer to Healthy and Diabetic Canine Pancreas

Gene therapy may provide new treatments for severe pancreatic disorders. However, gene transfer to the pancreas is difficult because of its anatomic location and structure, and pancreatitis is a serious concern. Like the human pancreas, the canine pancreas is compact, with similar vascularization and lobular structure. It is therefore a suitable model in which to assess gene transfer strategies. Here we examined the ability of adenoviral vectors to transfer genes into the pancreas of dogs in which pancreatic circulation had been clamped. Adenoviruses carrying the beta-galactosidase (beta-gal) gene were injected into the pancreatic-duodenal vein and the clamp was released 10 min later. These dogs showed beta-gal-positive cells throughout the pancreas, with no evidence of pancreatic damage. beta-Gal was expressed mainly in acinar cells, but also in ducts and islets. Moreover, transduction was prominent in connective tissue of the lobe septa. beta-Gal expression in the exocrine pancreas of a diabetic dog was also found to be similar to that observed in healthy dogs. Thus, efficient gene transfer to canine pancreas in vivo may be achieved by adenovirus injection after clamping pancreatic circulation. This technique may be used to assay new gene therapy approaches for diabetes mellitus and other pancreatic disorders.

Gene therapy for type 1 diabetes

The most intensively studied autoimmune disorder, type 1 diabetes mellitus (DM1), has attracted perhaps the greatest interest for gene-based therapeutic and prophylactic interventions. The final clinical manifestation of this immunologically and genetically complex disease, the absence of insulin, is the major starting point for almost all the gene therapy modalities attempted to date. Insulin replacement by transplantation of islets of Langerhans or surrogate beta cells is the obvious choice, but the allogeneic nature of the transplants activates potent antidonor immunoreactivity necessitating gene and cell-based immunosuppressive strategies as an alternative to the toxic pharmacologic immunosuppressives indicated for classic solid organ transplants. Accumulating knowledge of the cellular mechanisms involved in onset, however, have yielded promising tolerance induction prophylactic approaches using genes and cells. Despite the early successes in a number of animal models, the true test of efficacy in humans remains to be demonstrated.

Efficient gene delivery to human and rodent islets with double-stranded (ds) AAV-based vectors

Transplantation of allogeneic pancreatic islets is an effective approach to treat type 1 diabetes. To bypass the need for systemic administration of immunosuppression drugs following transplantation, approaches to genetically modify allogeneic islets to express anti-inflammatory, immunosuppressive, or antiapoptotic proteins prior to transplantation are being developed. Adeno-associated viral (AAV) based vectors have been used for gene transfer to islets, but the efficiency of functional transduction is low. Recently, double-stranded (ds) or double-copy (dc) based AAV vectors have been developed that allow for more rapid and efficient AAV-mediated transgene expression following transduction. Here we demonstrate that intact human and murine islets can be transduced with dsAAV2-eGFP efficiently compared to single-stranded AAV2-eGFP. Furthermore, our results demonstrate that murine islets transduced with dsAAV2-eGFP have normal islet glucose responsiveness, viability, and islet insulin content. Transplantation of the dsAAV2-eGFP transduced islet restored normal glycemia in diabetic mice without eliciting an immune response. Significant dsAAV2-mediated eGFP expression was observed in the islet grafts for at least 6 months post-transplant. Finally, we demonstrated that dsAAV serotypes 2, 6, and 8 infect human islets efficiently. Taken together, these results suggest that dsAAV based vectors are highly appropriate for gene transfer to islets to facilitate transplantation.

Long-term gene expression using the lentiviral vector in rat chondrocytes

The optimal approach to a long-term stable transgene expression in chondrocytes has not been established. Recently, lentiviral vectors have been used for transfection of some cultured cell lines. Our study tests the hypothesis that lentiviral vectors lead to longer gene expression in primary chondrocytes. We transfected lentiviral and adenoviral vectors carrying the green fluorescence protein gene to chondrocytes at different infection rates and cultured them in collagen Type I gel for up to 6 weeks. We also transplanted the cells of gel-suspended chondrocytes into the backs of nude mice. The mRNA expression of collagen Type II and aggrecan core protein was tested by real time polymerase chain reaction. The morphologic features and proliferation of chondrocytes were observed. Lentiviral vectors could transfect the green fluorescence protein gene to chondrocytes and the adenoviral vector, and there was no influence on the proliferation and phenotype of the chondrocytes. The percentage of lentiviral green fluorescence protein positive cells was much greater than the adenoviral green fluorescence protein at the end of 6 weeks. Stable green fluorescence protein expression was observed only in the lentivirus-transfected implants. The gene transfected by the lentiviral vector can be expressed efficiently for a long time and may be useful for gene transfer in cartilage defect repair.

Strategies of Conditional Gene Expression in Myocardium

The use of specialized reporter genes to monitor real-time, tissue-specific transgene expression in animal models offers an opportunity to circumvent current limitations associated with the establishment of transgenic mouse models. The Cre-loxP and the tetracycline (Tet)-inducible systems are useful methods of conditional gene expression that allow spatial (cell-type-specific) and temporal (inducer-dependent) control. Most often, the alpha-myosin heavy chain (alpha-MHC) promoter is used in these inducible systems to restrict expression of reporter genes and transgenes to the myocardium. An overview of each inducible system is described, along with suggested reporter genes for real-time, noninvasive imaging in the myocardium. Effective gene delivery of the inducible gene expression system is carried out by lentiviral vectors, which offer high transduction efficiency, long-term transgene expression, and low immunogenicity. This chapter outlines the packaging of myocardium-specific inducible expression systems into lentiviral vectors, in which a transgene and a reporter gene are transduced into cardiomyocytes. In doing so, transgene and reporter expression can be monitored/tracked with bioluminescence imaging (BLI) and positron emission tomography (PET).

In VivoGene Transfer to Pancreatic Beta Cells by Systemic Delivery of Adenoviral Vectors

Type 1 diabetes results from autoimmune destruction of pancreatic beta cells. This process might be reversed by genetically engineering the endocrine pancreas in vivo to express factors that induce beta cell replication and neogenesis and counteract the immune response. However, the pancreas is difficult to manipulate and pancreatitis is a serious concern, which has made effective gene transfer to this organ elusive. Thus, new approaches for gene delivery to the pancreas in vivo are required. Here we show that pancreatic beta cells were efficiently transduced to express beta-galactosidase after systemic injection of adenovirus into mice with clamped hepatic circulation. Seven days after vector administration about 70% of pancreatic islets showed beta-galactosidase expression, with an average of about 20% of the cells within positive islets being transduced. In addition, scattered acinar cells expressing beta-galactosidase were also observed. Thus, this approach may be used to transfer genes of interest to mouse islets and beta cells, both for the study of islet biology and gene therapy of diabetes and other pancreatic disorders.

Adenoviral gene transfer of erythropoietin confers cytoprotection to isolated pancreatic islets

BACKGROUND

The transfer of cytoprotective genes to isolated pancreatic islets may contribute to their enhanced survival in the transplant setting. Our laboratory established the expression of functional erythropoietin (EPO) receptors throughout pancreatic islets. Because EPO is a cytokine that promotes survival, we examined whether adenovirus-mediated gene transfer of EPO would result in cytoprotection of human pancreatic islets in culture and in the transplant setting.

METHODS

Isolated human islets were transduced using an adenoviral vector coding for human EPO or green fluorescent protein. Comparison of cell death in culture was measured using annexin V-phycoerythrin and propidium iodide. Transplantation of transduced islets into diabetic nude mice was used to assess the effect of EPO on islet function and in vivo survival.

RESULTS

Adenoviral delivery of EPO to pancreatic islets resulted in high-level EPO synthesis and secretion, which did not affect islet function in vitro or in vivo. Islets transduced with EPO were protected from apoptosis in culture and were at a functional advantage in vivo when compared with islets transduced with green fluorescent protein or untransduced islets. The high level of EPO had a negative effect on the blood chemistry of the animals that underwent transplantation.

CONCLUSIONS

Overexpression of EPO protects islets from destruction and does not compromise islet function. Genetic engineering with EPO may be a viable approach for improving islet survival and engraftment in the transplant setting, but regulation of the gene's expression will be an important prerequisite to this strategy.

Endocrine aspects of cancer gene therapy

The field of cancer gene therapy is in continuous expansion, and technology is quickly moving ahead as far as gene targeting and regulation of gene expression are concerned. This review focuses on the endocrine aspects of gene therapy, including the possibility to exploit hormone and hormone receptor functions for regulating therapeutic gene expression, the use of endocrine-specific genes as new therapeutic tools, the effects of viral vector delivery and transgene expression on the endocrine system, and the endocrine response to viral vector delivery. Present ethical concerns of gene therapy and the risk of germ cell transduction are also discussed, along with potential lines of innovation to improve cell and gene targeting.

Transduction of Human Islets with Pseudotyped Lentiviral Vectors

Type I diabetes is caused by an autoimmune-mediated elimination of insulin-secreting pancreatic islets. Genetic modification of islets offers a powerful molecular tool for improving our understanding of islet biology. Moreover, efficient genetic engineering of islets could allow for evaluation of new strategies aimed at preventing islet destruction. The present study evaluated the ability of a human immunodeficiency virus (HIV)-based lentiviral vector pseudotyped with various viral envelopes to target human islets ex vivo, with the goal of improving efficiency while minimizing toxicity. Transfer of the enhanced green fluorescent protein reporter gene in human islets was first evaluated with an HIV-based vector pseudotyped with the vesicular stomatitis virus (VSV), murine leukemia virus, Ebola, rabies, Mokola, or lymphocytic choriomeningitis virus (LCMV) envelope glycoprotein to optimize transduction efficiency. Results indicated that LCMV-pseudotyped vector transduced insulin-secreting beta cells with the highest efficiency. Moreover, toxicity associated with transduction of islets was found to be lower with LCMV-pseudotyped vector than with VSV-G-pseudotyped vector, the second most efficient vector for islet transduction. Overall, our study describes an improved methodology for achieving safe and efficient gene transfer into cells of human islets.

Lentiviral Vector: A Useful Tool for Transduction of Human Liver Endothelial Cells

Endothelial cells play multiple roles in pathophysiologic processes and are increasingly being recognized as target cells of gene therapy. Lentiviral vectors derived from human immunodeficiency virus type 1 have an ability to infect both dividing and nondividing cells and currently receive a great deal of attention as an innovative tool for transduction of target cells. The purpose of the present work was to evaluate the efficacy of a lentiviral vector for transducing human liver endothelial cells (HLECs) in vitro. For the present study, a pseudotyped lentiviral vector encoding a green fluorescent protein (GFP) gene, LtV-GFP, was generated by means of FuGENE 6 method and allowed to infect HLECs. Approximately 95% of HLECs were positive for GFP expression after LtV-GFP infection at a multiplicity of infection of 10. Notably, LtV-GFP transduced HLECs had stable and long term GFP expression, showed gene expression of endothelial markers including CD 34, factor VIII, flt-1, KDR/flk-1 and HGF, and maintained in vitro angiogenic potential in a Matrigel assay to the same extent as primarily cultured HLECs. These findings provide evidence that lentivirus based gene delivery is an efficient tool for transduction of endothelial cells that could be considered for cell and gene therapies and hybrid artificial organs.

Double genetic modification of adenovirus fiber with RGD polylysine motifs significantly enhances gene transfer to isolated human pancreatic islets

BACKGROUND

New strategies for improving durable functional islet mass will be instrumental in facilitating islet transplantation as a cure for type 1 diabetes mellitus. The ability to transfer immunoregulatory or cytoprotective genes into pancreatic islets may enhance survival. Adenoviral vectors (Ad5) have been used widely to deliver therapeutic genes to different tissues. Limitations associated with the use of Ad5 for gene therapy are related to the reliance of the virus on the presence of its primary receptor, the transient nature of the transgene expression, and the immediate inflammatory and immune response elicited by the infection. Because the arginine-glycine-aspartame (RGD) and polylysine (pK7) motifs have been shown to enhance Ad5 infection through an Ad5 receptor-independent pathway, we hypothesized that they could act additively to improve infectivity and reduce toxicity to isolated human pancreatic islets (IHPI).

METHODS

Hand-picked IHPI were infected with nonmodified Ad5, single-modified Ad5 with RGD (Ad5RGD) or pK7 (ad5pK7), and Ad5RGDpK7. Transfection efficiency was evaluated by green fluorescent protein and luciferase expression. Apoptosis was assessed using a quantitative assay, activation of caspase 3 by a colorimetric assay, nuclear factor (NF)-kappaB nuclear translocation using a promoter-luciferase NF-kappaB responsive construct, regulated on activation normal T-cell expressed and secreted (RANTES) by enzyme-linked immunosorbent assay. In vivo functionality was evaluated after transplantation into diabetic nonobese diabetic severe combined immunodeficiency mice.

RESULTS

Compared with unmodified and singly-modified Ad5 vectors, Ad5RGDpK7 demonstrated the highest infectivity. After the infection of IHPI with adenoviral vectors using the minimal dose required to infect greater than 80% of the islet cells (Ad5, 500 viral particles [VP]/cell; Ad5RGD and Ad5pK7, 10 VP/cell; Ad5RGDpK7, 0.1 VP/cell), islets infected with Ad5RGDpK7 presented a significant reduction in apoptosis, NF-kappaB nuclear translocation, RANTES expression, and higher glucose disposal rate; reduced Ad5-driven specific Th1 and antibody response were also observed.

CONCLUSIONS

Ad5RGDpK7 exhibited higher transfection efficiency, allowing a significant reduction in the viral dose required to infect greater than 80% of the islet cells. The reduction in the viral dose was associated with reduced toxicity, inflammation, and immune responses related to Ad5 infection. This strategy may thus be used to successfully modify isolated pancreatic islets.

Lentivirus-mediated transduction of connexin cDNAs shows level- and isoform-specific alterations in insulin secretion of primary pancreatic beta-cells

We have generated novel lentiviral vectors to integrate various connexin cDNAs into primary, non-dividing cells. We have used these vectors to test whether proper control of insulin secretion depends on a specific connexin isoform and/or on its level of expression. We have observed that transduced connexin32, connexin36 and connexin43 were expressed by primary adult beta-cells at membrane interfaces, were packed into typical gap junction plaques and formed functional channels that allowed a variable coupling, depending on the type and level of connexin expressed. The infected cells spontaneously reaggregated into three-dimensional pseudo-islet organs that could be maintained in culture. We have found that pseudo-islets made by cells transduced with either GFP- or connexin43-expressing lentivirus released insulin in response to various secretagogues similarly to controls. By contrast, pseudo-islets made by cells expressing connexin32, a connexin exogenous to pancreatic islets, or over-expressing connexin36, the endogenous islet connexin, featured a marked decrease in the secretory response to glucose. The data show: (1) that lentiviral vectors allow stable modulation of various connexin in primary, non-proliferating cells; (2) that specific connexin isoforms affect insulin secretion differently; and (3) that adequate levels of coupling via connexin36 channels are required for proper beta-cell function.

Gene- and cell-based therapeutics for type I diabetes mellitus

Type 1 diabetes mellitus, an autoimmune disorder is an attractive candidate for gene and cell-based therapy. From the use of gene-engineered immune cells to induce hyporesponsiveness to autoantigens to islet and beta cell surrogate transplants expressing immunoregulatory genes to provide a local pocket of immune privilege, these strategies have demonstrated proof of concept to the point where translational studies can be initiated. Nonetheless, along with the proof of concept, a number of important issues have been raised by the choice of vector and expression system as well as the point of intervention; prophylactic or therapeutic. An assessment of the current state of the science and potential leads to the conclusion that some strategies are ready for safety trials while others require varying degrees of technical and conceptual refinement.

Lentiviral vectors for gene delivery into cells

Human immunodeficiency virus type I (HIV) is the etiologic agent of acquired immunodeficiency syndrome or AIDS. Vectors based upon HIV have been in use for over a decade. Beginning in 1996, with the demonstration of improved pseudotyping using vesicular stomatitis virus (VSV) G protein along with transduction of resting mammalian cells, a series of improvements have been made in these vectors, making them both safer and more efficacious. Taking a cue from vector development of murine leukemia virus (MLV), split coding and self-inactivating HIV vectors now appear quite suitable for phase I clinical trials. In parallel, a number of pre-clinical efficacy studies in animals have demonstrated the utility of these vectors for various diseases processes, especially neurodegenerative and hematopoietic illnesses. These vectors are also appropriate for the study of other viruses (specifically of viral entry) and investigation of the HIV replicative cycle, along with straightforward transgene delivery to target cells of interest. Vectors based upon other lentiviruses have shown similar abilities and promise. Although concerns remain, particularly with regards to detection and propagation of replication-competent lentivirus, it is almost certain that these vectors will be introduced into the clinic within the next 3-5 years.

Efficient transduction of pancreatic islets by feline immunodeficiency virus vectors1

BACKGROUND

Pancreatic islets transplanted into immunocompetent diabetic subjects are rapidly lost to apoptotic or lytic death or both. Genetic engineering of islets before transplantation with protective genes may enhance their posttransplantation survival. Accomplishing this goal requires the development of a safe, efficient vector for islet gene delivery.

METHODS

The ability of feline immunodeficiency virus (FIV) vectors to transfer a green fluorescent protein (GFP) gene to NIT-1 cells and primary islets was measured and compared with murine leukemia virus (MLV) and human immunodeficiency virus (HIV) vectors. Islets were examined using confocal microscopy to determine the extent and pattern of infection. Toxicity of the procedure was assessed via measurement of glucose stimulation indices and by reversion of diabetic mice using either FIV-infected or control islet transplants.

RESULTS

FIV effectively transduces islets with no untoward effect on the insulin secretion capacity of the beta cells. When FIV, HIV, and MLV GFP vectors were standardized to the same 293 cell titer and used to infect NIT-1 cells or whole islets, the FIV transduced equal or greater numbers of cells relative to the HIV vector and significantly more than the MLV vector. Islets transduced with FIV GFP were transplanted in a murine model for diabetes and were shown to revert diabetes and express GFP 4 weeks after transduction and 3 weeks after transplantation.

CONCLUSIONS

FIV transduction is a nontoxic and efficient method to genetically modify pancreatic islets and may prove promising for delivering genes to augment islet survival after transplantation.

In vivo gene delivery to synovium by lentiviral vectors

The delivery of anti-arthritic genes to the synovial lining of joints is being explored as a strategy for the treatment of rheumatoid arthritis. In this study, we have investigated the use of VSV-G pseudotyped, HIV-1-based lentiviral vectors for gene delivery to articular tissues. Recombinant lentivirus containing a beta-galactosidase/neomycin resistance fusion gene under control of the elongation factor (EF) 1alpha promoter efficiently transduced human and rat synoviocytes and chondrocytes in cell culture. When directly injected into the knees of rats, this vector transduced synovial lining cells, but not other articular tissues such as cartilage. We also constructed a lentiviral vector containing the human interleukin-1 receptor antagonist (IL1RA) cDNA and examined transgene expression in vitro and in vivo following injection into the knee joints of rats. In immunocompetent animals, intra-articular IL1RA expression was high and persisted, at a sharply declining rate, for approximately 20 days. In immunocompromised rats, however, lentivirus-mediated intra-articular expression of human IL1RA was found to persist for at least 6 weeks. Extra-articular expression of the transgene was minimal. These results indicate that lentiviral vectors are capable of efficient in vivo gene transfer to synovium and merit further investigation as a means of providing long-term expression for gene-based treatments of arthritis.

Genetically modified adenovirus vector containing an RGD peptide in the HI loop of the fiber knob improves gene transfer to nonhuman primate isolated pancreatic islets

The ability to transfer immunoregulatory, cytoprotective, or antiapoptotic genes into pancreatic islets (PIs) may allow enhanced post-transplantation survival. The available gene transfer vectors differ greatly in their ability to infect and express genes in different cell types. One limitation associated with the use of viral vectors is related to the virus reliance on the presence of its primary binding site. Tropism of the viral vectors can be altered using retargeting strategies. Results on phage biopanning proved that the RGD motif has in vivo targeting capabilities. This motif interacts especially with cellular integrins of the alphavbeta3 and alphavbeta5 types, highly expressed on pancreatic islets. In this report, we have explored the utility of a retargeted adenovirus vector (Ad) containing an RGD motif in the HI loop of the fiber knob in order to improve the infection efficiency to intact isolated nonhuman primate PIs and reduce toxicity after the genetic modification. Nonhuman primate Pis were isolated by a semi-automated technique. Steptozotocin-induced diabetic mice with severe combined immunodeficiency disease (SCID) were used as recipients. A recombinant Ad containing a heterologous RGD peptide and expressing luciferase (AdRGDLuc) or green fluorescent protein (AdRGDGFP) were generated in our laboratory. Similar Ads without the RGD peptide were used as a control (AdLuc and AdGFP). Higher transfection efficiency was demonstrated using AdRGDGFP compared with AdGFP (>80% of the islet cells were infected at 10 particle-forming units (pfu)/cell using AdRGDGFP vs. 7% after infection with AdGFP).More than 90% of the infected cells were insulin-producing cells. Significantly higher transgene expression was demonstrated after infection with AdRGDLuc compared with AdLuc at different titers. Analysis of the glucose-stimulated insulin response demonstrated better performance of PI transfected with AdRGDLuc at low titers (10 pfu/cell in order to achieve > 80% transfection efficiency) compared with AdLuc at high titers. Finally, long-term euglycemia (>250d) was observed in 89% of the animals that received PI infected with AdRGDLuc compared with none of the animals that received PI infected with AdLuc. The present study provides new information about the possibility of tropism modification of Ad vectors to increase the transfection efficiency and transgene expression to isolated PI. Incorporation of the RGD sequence in the HI loop of the fiber knob allows highly efficient transfection efficiency to nonhuman primate insulin-producing cells and adequate long-term function of the p-cell after transplantation.

Indoleamine 2,3-dioxygenase expression in transplanted NOD Islets prolongs graft survival after adoptive transfer of diabetogenic splenocytes

Indoleamine 2,3-dioxygenase (IDO) catalyzes the breakdown of the amino acid tryptophan into kyneurenine. It has been shown that IDO production by placental trophoblasts prevents the attack of maternal T-cells activated in response to the paternal HLA alleles expressed by the tissues of the fetus. In this article, we show that adenoviral gene transfer of IDO to pancreatic islets can sufficiently deplete culture media of tryptophan and consequently inhibit the proliferation of T-cells in vitro. Experiments in vivo have also demonstrated that transplantation of IDO-expressing islets from prediabetic NOD mouse donors into NODscid recipient mice is associated with a prolongation in islet graft survival after adoptive transfer of NOD diabetogenic T-cells. This protection is attributed to the depletion of tryptophan at the transplantation site beneath the kidney capsule. These results suggest that local modulation of tryptophan catabolism may be a means of facilitating islet transplantation as a therapy for type 1 diabetes.

Efficient gene delivery and targeted expression to hepatocytes in vivo by improved lentiviral vectors

Safe and efficient genetic modification of liver cells could enable new therapies for a variety of hepatic and systemic diseases. Lentiviral vectors are promising tools for in vivo gene delivery. Previous data suggested that recruitment into the cell cycle was required for transduction of hepatocytes in vivo. We developed an improved vector design that enhanced nuclear translocation in target cells and significantly improved gene transfer performance. Using the new vector and a panel of internal promoters, we showed that rat hepatocytes were transduced ex vivo to high frequency without requirement for proliferation. On intravenous administration of vector into adult severe combined immunodeficient (SCID) mice, we found high levels (up to 30%) of transduction of parenchymal and nonparenchymal cells of the liver, integration of the vector genome in liver DNA and stable expression of the marker green fluorescent protein (GFP)-encoding gene without signs of toxicity. Coadministration of vectors and 5'-bromo-2'-deoxyuridine in vivo proved that cell cycling was not required for efficient transduction of hepatocytes. In addition to the liver, the spleen and the bone marrow were transduced effectively by systemic delivery of vector. GFP expression was observed in all these organs when driven by the cytomegalovirus promoter and by the phosphoglycerate kinase gene promoter. Using the promoter of the albumin gene, we could restrict expression to hepatocytes. By a single vector injection into the bloodstream of SCID mice, we achieved therapeutic-range levels of the human clotting factor IX, stable in the plasma for up to 1 year (the longest time tested), indicating the potential efficacy of improved lentiviral vectors for the gene therapy of hemophilias and other diseases.

Neonatal porcine pancreatic cell clusters as a potential source for transplantation in humans: characterization of proliferation, apoptosis, xenoantigen expression and gene delivery with recombinant AAV

Neonatal porcine islets are characterized by reproducible isolation success and high yields, sizable advantages over adult islets. In this work we have analyzed selected phenotypic and functional characteristics of porcine neonatal islets relevant to their possible use for transplant in humans. We show that porcine islet cells proliferate in culture, and synthesize and store islet-specific hormones. Proliferating beta cells can be easily identified. Implant of cultured neonatal islets in immunodeficient rodents results in the reversal of diabetes, albeit with delay. We also show that measurable apoptosis occurs in cultured neonatal porcine islets. Further, antigens recognized by human natural antibodies are expressed in a dynamic fashion over the culture period analyzed and are not limited to the alpha-Gal epitope. Lastly, we demonstrate that a recombinant Adeno-Associated virus can be used to efficiently deliver a reporter gene in porcine islets. This characterization might be helpful in the definition of the potential use of neonatal porcine islets for human transplantation.

Lentivirus gene transfer in murine hematopoietic progenitor cells is compromised by a delay in proviral integration and results in transduction mosaicism and heterogeneous gene expression in progeny cells

Human immunodeficiency virus type 1-based lentivirus vectors containing the green fluorescent protein (GFP) gene were used to transduce murine Lin(-) c-kit(+) Sca1(+) primitive hematopoietic progenitor cells. Following transduction, the cells were plated into hematopoietic progenitor cell assays in methylcellulose and the colonies were scored for GFP positivity. After incubation for 20 h, lentivirus vectors transduced 27.3% +/- 6.7% of the colonies derived from unstimulated target cells, but transduction was more efficient when the cells were supported with stem cell factor (SCF) alone (42. 0% +/- 5.5%) or SCF, interleukin-3 (IL-3), and IL-6 (53.3 +/- 1.8%) during transduction. The, vesicular stomatitis virus glycoprotein-pseudotyped MGIN oncoretrovirus control vector required IL-3, IL-6, and SCF for significant transduction (39.3 +/- 9.4%). Interestingly, only a portion of the progeny cells within the lentivirus-transduced methylcellulose colonies expressed GFP, in contrast to the homogeneous expression in oncoretrovirus-transduced colonies. Secondary plating of the primary GFP(+) lentivirus vector-transduced colonies revealed vector PCR(+) GFP(+) (42%), vector PCR(-) GFP(-) (46%), and vector PCR(+) GFP(-) (13%) secondary colonies, indicating true genetic mosaicism with respect to the viral genome in the progeny cells. The degree of vector mosaicism in individual colonies could be reduced by extending the culture time after transduction and before plating into the clonal progenitor cell assay, indicating a delay in the lentiviral integration process. Furthermore, supplementation with exogenous deoxynucleoside triphosphates during transduction decreased mosaicism within the colonies. Although cytokine stimulation during transduction correlates with higher transduction efficiency, rapid cell division after transduction may result in loss of the viral genome in the progeny cells. Therefore, optimal transduction may require activation without promoting intense cell proliferation prior to vector integration.

Prevention of beta cell dysfunction and apoptosis activation in human islets by adenoviral gene transfer of the insulin-like growth factor I

Interleukin-1beta is a potent pro-inflammatory cytokine that has been shown to inhibit islet beta cell function as well as to activate Fas-mediated apoptosis in a nitric oxide-dependent manner. Furthermore, this cytokine is effective in recruiting lymphocytes that mediate beta cell destruction in IDDM onset. The insulin-like growth factor I (IGF-I) has been shown to block IL-1beta actions in vitro. We hypothesized that gene transfer of the insulin-like growth factor I to intact human islets could prevent IL-1beta-induced beta cell dysfunction and sensitization to Fas-triggered apoptosis activation. Intact human islets were infected with adenoviral vectors encoding IGF-I as well as beta-galactosidase and enhanced green fluorescent protein as controls. Adenoviral gene transfer of human IGF-I prevented IL-1beta-mediated nitric oxide production from human islets in vitro as well as the suppression of beta cell function as determined by glucose-stimulated insulin production. Moreover, IGF-I gene transfer prevented IL-1beta-induced, Fas-mediated apoptosis. These results suggest that locally produced IGF-I from cultured islets may be beneficial in maintaining beta cell function and promoting islet survival before and following islet transplantation as a potential therapy for type I diabetes.

Protection of human islets from the effects of interleukin-1beta by adenoviral gene transfer of an Ikappa B repressor

Interleukin-1beta (IL-1beta) is a pro-inflammatory cytokine that inhibits beta cell function and promotes Fas-triggered apoptosis. IL-1beta is thought to act early in the initiation of the autoimmune destruction of pancreatic beta cells in type I diabetes. IL-1beta promotes beta cell impairment, in part, by activating NF-kappaB transcription factor-dependent signaling pathways. We have examined whether beta cells could be protected from the effects of IL-1beta by overexpressing an inhibitor of NF-kappaB activity, IkappaB, by adenoviral gene transfer to intact human islets in culture. Infection of islets with an adenoviral vector encoding a non-phosphorylatable, non-degradable variant of IkappaBalpha resulted in normal insulin responses to glucose in the presence of IL-1beta. Furthermore, nitric oxide production was prevented and, more importantly, Fas-triggered apoptosis was inhibited following IkappaBalpha gene transfer. These results suggest that blocking the NF-kappaB pathway might prevent cytokine-induced beta cell impairment as a means of facilitating islet transplantation.

Adeno-associated virus vector mediated gene transfer to pancreatic beta cells

Insulin-dependent diabetes mellitus (IDDM) or type 1 diabetes is an autoimmune disease that results in destruction of the insulin-producing pancreatic islet beta cells. Several factors induce the invasion of immune cells into islets and trigger inflammation. Gene therapy approaches targeting the islet cells could be an effective treatment to prevent the onset or reverse type 1 diabetes. Allogeneic islet transplantation provides short-term treatment. However, genetically modified islets, which resist the host immune response, could provide long-term solutions. Adeno-associated virus (AAV) is emerging as a prominent vector system for delivering therapeutic genes for human gene therapy. AAV vector can transduce nondividing cells and provide long-term gene expression by integrating into host chromosome. Therefore, it is an appropriate vector system for islet cell gene therapy. To test the efficacy of AAV vector to transduce pancreatic endocrine cells, we constructed AAV vectors using plasmid pSub201. Wild-type AAV DNA analogue from plasmid psub201 was subcloned into a cloning plasmid pSP72 and AAV vectors were constructed by inserting the transgenes with heterologous promoter in place of AAV open reading frames (rep and cap). In this report we demonstrate the transduction of pancreatic islet cells with AAV vectors encoding bacterial -galactosidase enzyme or enhanced green fluorescent protein (EGFP) as reporter gene. Dispersed porcine and rat islet cells can be transduced by AAV vector, with an efficiency of 47% and 38%, respectively. In particular porcine islet insulin producing beta cells were transduced with an efficiency of 39%. Intact rat islet cells were transduced with an efficiency of 26% as estimated by FACS analysis following transduction with an AAV vector encoding EGFP. Transduction of intact rat islets with an AAV vector did not alter glucose-induced insulin secretion. AAV vector transduction was higher in transformed islet cell lines INS-1 and RIN m5F with an efficiency of 65% and 57%, respectively. These new results suggest that AAV vectors will provide an improved method of gene delivery to pancreatic islets and isolated pancreatic beta cells.

Lentiviral vectors: excellent tools for experimental gene transfer and promising candidates for gene therapy

Lentiviral vectors are tools for gene transfer derived from lentiviruses. From their first application to now they have been strongly developed in design, in biosafety and in their ability of transgene expression into target cells. Primate and non-primate derived lentiviral vectors are now available and with both types of systems a lot of studies tuned to improve their performances in a large number of tissues are ongoing. Here we review the state of the art of lentiviral vector systems discussing their potential for gene therapy.