IL-10 and TGF-beta gene transfer to rodent islets: effect on xenogeneic islet graft survival in naive and B-cell-deficient mice

Newer therapeutic approaches towards the management of diabetes mellitus: an update

Diabetes mellitus is a chronic metabolic condition characterized by an elevation of blood glucose levels, resulting from defects in insulin secretion, insulin action, or both. The prevalence of the disease has been rapidly rising all over the globe at an alarming rate. Despite advances in the management of diabetes mellitus, it remains a growing epidemic that has become a significant public health burden due to its high healthcare costs and its complications. There is no cure has yet been found for the disease, however, treatment modalities include insulin and antidiabetic agents along with lifestyle modifications are still the mainstay of therapy for diabetes mellitus. The treatment spectrum for the management of diabetes mellitus has rapidly developed in recent years, with new class of therapeutics and expanded indications. This article focused on the emerging therapeutic approaches other than the conventional pharmacological therapies, which include stem cell therapy, gene therapy, siRNA, nanotechnology and theranostics.

Expression of Transforming Growth Factor-β by Human Islets: Impact on Islet Viability and Function

Transforming growth factor-β1 (TGF-β1) is a pleotropic cytokine that promotes angiogenesis and extracellular matrix protein synthesis in addition to its immunosuppressive effects. The purpose of this study is to identify optimal conditions for in vivo expression of TGF-β1 by human islets to exploit the possible beneficial effects and minimize undesirable side effects. We transduced human islets with adenoviral vectors encoding the active form of Ad-TGF-β1 or Ad-LacZ to test the effects of TGF-β1 gene expression on islet in vivo function following their transplantation into a NOD-SCID mouse model. Islets were transduced with multiplicity of infection (MOI) of 20, 10, 5, and 2.5 per islet cell. At a MOI ranging from 2.5 to 20, expression of TGF-β1 in islet supernatant persisted for 1–2 months and ranged from 153 ± 5 to 2574 ± 1299 pg/ml, respectively. Transduction with the lowest MOI (2.5) did not compromise the in vivo production of human C-peptide. We conclude that TGF-β1 expression in transplanted islets does not compromise viability and that adenoviral transduction with the TGF-β1 gene has a dose-dependent effect, with larger MOIs being deleterious. The data also indicate that in vitro culture system and the in vivo NOD-SCID model could be used successfully to evaluate the nonimmune effects of gene transduction.

Overexpression of thioredoxin in islets transduced by a lentiviral vector prolongs graft survival in autoimmune diabetic NOD mice

Abstract

Pancreatic islet transplantation is considered an appropriate treatment to achieve insulin independence in type I diabetic patients. However, islet isolation and transplantation-induced oxidative stress and autoimmune-mediated destruction are still the major obstacles to the long-term survival of graft islets in this potential therapy. To protect islet grafts from inflammatory damage and prolong their survival, we transduced islets with an antioxidative gene thioredoxin (TRX) using a lentiviral vector before transplantation. We hypothesized that the overexpression of TRX in islets would prolong islet graft survival when transplanted into diabetic non-obese diabetic (NOD) mice.

Methods

Islets were isolated from NOD mice and transduced with lentivirus carrying TRX (Lt-TRX) or enhanced green fluorescence protein (Lt-eGFP), respectively. Transduced islets were transplanted under the left kidney capsule of female diabetic NOD mice, and blood glucose concentration was monitored daily after transplantation. The histology of the islet graft was assessed at the end of the study. The protective effect of TRX on islets was investigated.

Results

The lentiviral vector effectively transduced islets without altering the glucose-stimulating insulin-secretory function of islets. Overexpression of TRX in islets reduced hydrogen peroxide-induced cytotoxicity in vitro. After transplantation into diabetic NOD mice, euglycemia was maintained for significantly longer in Lt-TRX-transduced islets than in Lt-eGFP-transduced islets; the mean graft survival was 18 vs. 6.5 days (n = 9 and 10, respectively, p < 0.05).

Conclusion

We successfully transduced the TRX gene into islets and demonstrated that these genetically modified grafts are resistant to inflammatory insult and survived longer in diabetic recipients. Our results further support the concept that the reactive oxygen species (ROS) scavenger and antiapoptotic functions of TRX are critical to islet survival after transplantation.

Transduction of rat pancreatic islets with pseudotyped adeno-associated virus vectors

Background

Pancreatic islet transplantation is a promising treatment for type I diabetes mellitus, but current immunosuppressive strategies do not consistently provide long-term survival of transplanted islets. We are therefore investigating the use of adeno-associated viruses (AAVs) as gene therapy vectors to transduce rat islets with immunosuppressive genes prior to transplantation into diabetic mice.

Results

We compared the transduction efficiency of AAV2 vectors with an AAV2 capsid (AAV2/2) to AAV2 vectors pseudotyped with AAV5 (AAV2/5), AAV8 (AAV2/8) or bovine adeno-associated virus (BAAV) capsids, or an AAV2 capsid with an insertion of the low density lipoprotein receptor ligand from apolipoprotein E (AAV2apoE), on cultured islets, in the presence of helper adenovirus infection to speed expression of a GFP transgene. Confocal microscopy and flow cytometry were used. The AAV2/5 vector was superior to AAV2/2 and AAV2/8 in rat islets. Flow cytometry indicated AAV2/5-mediated gene expression in approximately 9% of rat islet cells and almost 12% of insulin-positive cells. The AAV2/8 vector had a higher dependence on the helper virus multiplicity of infection than the AAV 2/5 vector. In addition, the BAAV and AAV2apoE vectors were superior to AAV2/2 for transducing rat islets. Rat islets (300 per mouse) transduced with an AAV2/5 vector harboring the immunosuppressive transgene, tgfβ1, retain the ability to correct hyperglycemia when transplanted into immune-deficient diabetic mice.

Conclusion

AAV2/5 vectors may therefore be useful for pre-treating donor islets prior to transplantation.

Avenues for immunomodulation and graft protection by gene therapy in transplantation

Organ transplantation represents the only definitive therapy for many causes of end-organ failure. However, the universal success of this therapy is limited by chronic allograft rejection, the side effects of chronic immunosuppressive therapy, and a severe shortage of donor organs. Presently, the success of solid-organ transplantation depends on the continuous administration of toxic and nonspecific immunosuppressive agents, therapies that present risks for opportunistic infection, malignancy, and a variety of agent-specific side effects. To promote the use of transplantation with limited risk of long-term sequelae, three dominant research challenges emerge: (i) elimination of the need for exogenous immunosuppression by immunological tolerance induction; (ii) prevention of chronic rejection/graft dysfunction; and (iii) expansion of available organs for transplantation. Gene therapy may provide significant advances and solutions in each of these areas. Rejection of the graft in the immediate post-transplant period has been attacked through the transfer of immunomodulatory molecules in addition to tolerance inducing approaches. Chronic graft rejection may be similarly addressed through permanent tolerance induction or alternatively through the introduction of molecules to resist chronic graft damage. Genetic manipulation of stem cells may ultimately produce transgenic animals to serve as tissue donors to overcome the limited donor organ supply. This review will highlight ongoing developments in the translation of gene therapy approaches to the challenges inherent in transplantation.

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.

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.

Suppression of allogeneic response by viral IL-10 gene transfer

Th1 cell activation and cytokine production shift the balance between Th1 and Th2, favoring the upregulation of proinflammatory activity that leads to destruction of allogeneic hepatocytes following transplantation. Th2-type cytokines. such as IL-10, have immune regulatory function. The aim of this study was to determine the antirejection efficacy of allogeneic hepatocytes with spheroidal shape (spheroids) genetically modified with viral IL-10 (vIL-10). Allogeneic hepatocyte spheroids, transferred vIL-10 gene by using adenovirus as the vector, were transplanted into the spleen of Nagase's analbuminemic rats (NAR). NAR transplanted with vIL-10-transfected hepatocytes showed an abrupt rise in serum albumin levels that peaked on day 7 and remained at high levels up to day 21 after transplantation. The peak level of albumin on day 7 in vIL-10-transfected NAR was eminently higher than that in nontransfected NAR. Histopathological analysis revealed that in nontransfected NAR hepatocyte spheroids were more or less rejected on day 4, and, in contrast, vIL-10-transfected spheroids were still not rejected on day 14. This protective effect correlated with sustained high vIL-10 level in the splenic vein in NAR transplanted with vIL-10-transfected hepatocyte spheroids, suggesting that vIL-10 secreted from the transplanted hepatocytes induced an active suppression of allogeneic response. This study provides evidence to support the possibility of using vIL-10 gene therapy to prevent allogeneic response in hepatocyte transplantation.

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.

Gene and cell therapies for diabetes mellitus: strategies and clinical potential

The last 5 years have witnessed an explosion in the use of genes and cells as biomedicines. While primarily aimed at cancer, gene engineering and cell therapy strategies have additionally been used for Mendelian, neurodegenerative and metabolic disorders. The main focus of gene and cell therapy strategies in metabolism has been diabetes mellitus. This disease is a disorder of glucose homeostasis, either due to the immune-mediated eradication of pancreatic beta cells in the islets of Langerhans (type 1 diabetes) or resulting from insulin resistance and obesity syndromes where the insulin-producing capability of the beta cell is ultimately exhausted in the face of insensitivity to the effects of insulin in the peripheral glucose-utilising tissues (type 2 diabetes). A significant number of animal studies have demonstrated the potential in restoring normoglycaemia by islet transplantation in the context of immunoregulation achieved by gene transfer of immunoregulatory genes to allo- and xenogeneic islets ex vivo. Additionally, gene and cell therapy has also been used to induce tolerance to auto- and alloantigens and to generate the tolerant state in autoimmune rodent animal models of type 1 diabetes or rodent recipients of allogeneic/xenogeneic islet transplants. The achievements of gene and cell therapy in type 2 diabetes are less evident, but seminal studies promise that this modality can be relevant to treat and perhaps prevent the underlying causes of the disease. Here we present an overview of the current status of gene and cell therapy for type 1 and 2 diabetes and we propose potential therapeutic options that could be clinically useful. For type 1 diabetes, transplantation of islets engineered to evade or suppress the recipient immune response is the most readily-available technology today. A number of gene delivery vectors encoding proteins that impair a variety of immune cells have already been examined and proven versatile. More challenging but, nonetheless, just over the horizon are attempts to promote tolerance to islet allografts. Type 2 diabetes will likely require a better understanding of the processes that determine insulin sensitivity in the periphery. Targeting tissues such as muscle and fat with vectors encoding genes whose products promote insulin sensitivity and glucose uptake is an approach that does not carry with it the side-effects often associated with pharmacologic agents currently in use. In the end, progress in vector design, elucidation of antigen-specific immunity and insulin sensitivity will provide the framework for gene drug use in the treatment of type 1 and type 2 diabetes.

Suppression of autoimmune diabetes by viral IL-10 gene transfer

Th1 cell activation and cytokine production shift the balance between Th1 and Th2, favoring the up-regulation of proinflammatory activity that leads to destruction of insulin-producing pancreatic beta cells in type 1 diabetes. Th2-type cytokines, such as IL-10, have immune regulatory function. Administration of IL-10, or IL-10 gene transfer, prevents autoimmune diabetes in nonobese diabetic (NOD) mice. However, constant administration of purified rIL-10 is not practical for long-term therapy to prevent diabetes. In this study, we transferred the BCRF-1 gene, an open reading frame in the Epstein-Barr viral genome with remarkable homology to mouse IL-10 (viral IL-10 or vIL-10), by an adeno-associated viral (AAV) vector to NOD mice to attain sustained vIL-10 gene expression. Like endogenous mouse IL-10, vIL-10 has potent immunoregulatory and immunosuppressive functions, but can be specifically distinguished from endogenous mouse IL-10 for monitoring of the transgene expression. A single systemic administration of AAV vIL-10 significantly reduced insulitis and prevented diabetes development in NOD mice. This protective effect correlated with sustained transgene expression and protein production. Moreover, splenocytes from the treated mice blocked diabetes transfer to NOD recipients, suggesting that vIL-10 induces an active suppression of autoimmunity. This study provides evidence to support the possibility of using vIL-10 gene therapy to prevent type 1 diabetes.

Human pancreatic islets transfected to produce an inhibitor of TNF are protected against destruction by human leukocytes

The objective of this study was to determine whether transfection of human islets with an adenovirus construct encoding an inhibitor of tumor necrosis factor (TNFi) was effective at limiting damage to beta cells induced by human peripheral blood leukocytes (huPBL). Human islets transfected with TNFi or control islets were transplanted under the kidney capsule of NOD-scid mice. After a 15-day engraftment period, half of the mice received injections of activated huPBL and half received buffer injections. Islet graft function was assessed by two different methods, both of which use a species-specific radioimmunoassay to determine human insulin. In some mice, insulin production following intraperitoneal glucose injection was determined in serum. In other mice, total graft insulin content was determined by acid ethanol extraction. Histochemical stains were performed on some kidneys at the termination of the experiment to evaluate graft presence, transgene expression, and huPBL infiltration. In huPBL injected mice, graft performance was maintained in mice whose grafts were transfected with TNFi but declined substantially in control groups with sham transfected or beta-galactosidase transfected islet grafts. Similar results were obtained using either glucose-stimulated insulin release or graft insulin content as a measure of graft survival. There was no significant difference in graft function between control groups receiving buffer injections, regardless of whether the islets had been transfected. Human leukocytes were found in all huPBL groups regardless of islet transfection status. We conclude that transfection of human islets with an adenovirus encoding TNFi protects beta cells from destruction induced by human leukocytes. The local production of TNFi does not prevent graft infiltration by leukocytes, only the destruction of grafts by the infiltrating leukocytes. These results raise the possibility that local expression of an inhibitor of the proinflammatory cytokine TNF-alpha may also prevent graft failure in clinical islet transplantation.

Infection of intact human islets by a lentiviral vector

The transfer of genes encoding immunomodulatory proteins to islets can be used to improve islet function, block apoptosis, and inhibit rejection following transplantation. Adenoviral vectors have been shown to infect intact human islets, but the immunogenicity and transient gene expression of the current adenoviral vectors may hinder their use clinically for islet transplantation. In this report, we compared an HIV-1-based lentiviral vector with the E1-deleted adenoviral vehicle of the Ad5 type for gene transfer to human islets in vitro. We demonstrate that at similar viral particle concentrations per islet that an HIV-based lentiviral vector is able to infect beta-cells within an intact human islet at an efficiency similar to an adenoviral vector. In addition, both the adenoviral and lentiviral vectors were able to express significant levels of soluble interleukin-1 receptor antagonist (IL-1Ra) protein following infection of intact islets. More importantly, there was no impairment of islet beta-cell function following adenoviral and lentiviral infection in responding to glucose stimulation. These results support the utility of replication-defective lentiviral vectors as efficient gene delivery vehicles to islets to faciliate transplantation of islets for therapy of type I diabetes.

Transforming growth factor (TGF)-beta mimics and anti-TGF-beta antibody abrogates the in vivo effects of cyclosporine: demonstration of a direct role of TGF-beta in immunosuppression and nephrotoxicity of cyclosporine

BACKGROUND

Cyclosporine (CsA) has been shown to induce the expression of transforming growth factor (TGF)-beta both in vitro and in vivo. It is hypothesized that the efficacy as well as the side effects of CsA are mediated by TGF-beta. This study was planned to investigate whether anti-TGF-beta mitigated and TGF-beta reproduced the in vivo effects of CsA to directly prove this hypothesis.

METHODS

B6AF1 (H2b/k.d) mice were divided into groups and received the following: CsA, vehicle (olive oil), CsA + anti-TGF-beta1 antibody, TGF-beta1, or vehicle phosphate-buffered saline/bovine serum albumin. All studies were carried out at 10 and 28 days after the last day of CsA administration with the exception of the exogenous TGF-beta experiments, which were performed 5 days after exogenous TGF-beta administration. The efficacy was studied by the anti-CD3-induced ex vivo proliferation of splenocytes measured by [3H]thymidine uptake; TGF-beta protein levels were quantified by ELISA. TGF-beta, collagen, and fibronectin gene expression was studied using reverse transcriptase-polymerase chain reaction, and histopathological analysis was made on periodic acid-Schiff- and trichrome C-stained thin kidney sections.

RESULTS

CsA treatment resulted in decreased ex vivo proliferation of splenocytes, an increase in TGF-beta protein in the sera, and renal histopathological changes including tubular swelling, vacuolization, thrombotic microangiopathy, and increased expression of TGF-beta, collagen and fibronectin genes. All of these findings were blocked by anti-TGF-beta antibody.

CONCLUSION

The study demonstrates the in vivo modulation of the effects of CsA by manipulating TGF-beta levels and suggests that TGF-beta at least in part mediates CsA's beneficial and detrimental effects.

Lentivirus-mediated transduction of islet grafts with interleukin 4 results in sustained gene expression and protection from insulitis

Autoimmune destruction of islets in the pancreas leads to the development of insulin-dependent diabetes mellitus (IDDM). Replacement of insulin-producing tissue by transplantation of islets provides a cure to disease but requires immunosuppression or a means of controlling anti-graft immune responses. To promote islet survival we have utilized a local approach by expressing immunoregulatory molecules in islet grafts. The results presented here show that the human immunodeficiency virus (HIV)-based lentiviral vector is capable of stably transducing whole islets. Foreign reporter gene expression was observed both in vitro and in vivo 30 days after transplantation. Grafts containing insulin-positive beta-islet cells expressing foreign protein indicate that transduction does not interfere with glucose regulation. The absence of inflammatory infiltrates in grafts suggests that transduction does not activate the immune system. When islets transduced with an HIV vector expressing IL-4 were transplanted into diabetes-prone mice, animals were protected from autoimmune insulitis and islet destruction. As demonstrated by proliferative and cytokine analysis, protection was consistent with a switching of islet-antigen-specific T cell responses toward a Th2 phenotype. These results suggest that HIV-based lentivirus vectors can efficiently transduce islet cells with genes encoding potentially therapeutic molecules, for possibly managing diabetes.