Bipartite adenoviral vector encoding hHGF and hIL-1Ra for improved human islet transplantation

Current Landscape of Various Techniques and Methods of Gene Therapy through CRISPR Cas9 along with its Pharmacological and Interventional Therapies in the Treatment of Type 2 Diabetes Mellitus

BACKGROUND

Type 2 diabetes mellitus (T2DM) is frequently referred to as a "lifestyle illness". In 2000, India (31.7 million) had the greatest global prevalence of diabetes mellitus, followed by China (20.8 million), the United States (17.7 million), and other countries. In recent years, the treatment of gene therapy (T2DM) has attracted intensive interest.

OBJECTIVE

We aimed to critically review the literature on the various techniques and methods, which may be a possible novel approach through the gene therapy CRISPR Cas9 and some other gene editing techniques for T2DM. Interventional and pharmacological approaches for the treatment of T2DM were also included to identify novel therapies for its treatment.

METHOD

An extensive literature survey was done on databases like PubMed, Elsevier, Science Direct and Springer.

CONCLUSION

It can be concluded from the study that recent advancements in gene-editing technologies, such as CRISPR Cas9, have opened new avenues for the development of novel therapeutic approaches for T2DM. CRISPR Cas9 is a powerful tool that enables precise and targeted modifications of the genome.

Improved therapeutic potential of MSCs by genetic modification

Mesenchymal stem cells (MSCs), well-studied adult stem cells in various tissues, possess multi-lineage differentiation potential and anti-inflammatory properties. MSCs have been approved to regenerate lineage-specific cells to replace injured cells in tissues. MSCs are approved to treat inflammatory diseases. With the discovery of genes important for the repair of damaged tissues, MSCs genetically modified by such genes hold improved therapeutic potential. In this review, we summarised the uses of genetically modified MSCs to treat different diseases, including bone diseases, cardiovascular diseases, autoimmune diseases, central nervous system disorders, and cancer. To better understand the exact role of genetically modified MSCs, key mechanisms determining, which genes are selected to be used for modifying MSCs and improvements in post-genetic modification are discussed. Therapeutic benefits enhanced by genetic modifications are to be documented by further clinical studies.

Genetically modified human bone marrow derived mesenchymal stem cells for improving the outcome of human islet transplantation

The objective of this study was to determine the potential of human bone marrow derived mesenchymal stem cells (hBMSCs) as gene carriers for improving the outcome of human islet transplantation. hBMSCs were characterized for the expression of phenotypic markers and transduced with Adv-hVEGF-hIL-1Ra to overexpress human vascular endothelial growth factor (hVEGF) and human interleukin-1 receptor antagonist (hIL-1Ra). Human islets were co-cultured with hBMSCs overexpressing hVEGF and hIL-1Ra. Islet viability was determined by membrane fluorescent method and glucose stimulation test. Transduced hBMSCs and human islets were co-transplanted under the kidney capsule of NOD.Cg-Prkdc^scid Il2rg^tm1Wjl/SzJ (NSG) diabetic mice and blood glucose levels were measured over time to demonstrate the efficacy of genetically modified hBMSCs. At the end of study, immunofluorescent staining of kidney section bearing islets was performed for insulin and von Willebrand Factor (vWF). hBMSCs were positive for the expression of CD73, CD90, CD105, CD146 and Stro-1 surface markers as determined by flow cytometry. Transduction of hBMSCs with adenovirus did not affect their stemness and differentiation potential as confirmed by mRNA levels of stem cell markers and adipogenic differentiation of transduced hBMSCs. hBMSCs were efficiently transduced with Adv-hVEGF-hIL-1Ra to overexpress hVEGF and hIL-1Ra. Live dead cell staining and glucose stimulation test have shown that transduced hBMSCs improved the viability of islets against cytokine cocktail. Co-transplantation of human islets with genetically modified hBMSCs improved the glycemic control of diabetic NSG mice as determined by mean blood glucose levels and intraperitoneal glucose tolerance test. Immunofluorescent staining of kidney sections was positive for human insulin and vWF. In conclusion, our results have demonstrated that hBMSCs may be used as gene carriers and nursing cells to improve the outcome of islet transplantation.

RGD peptide-modified adenovirus expressing hepatocyte growth factor and X-linked inhibitor of apoptosis improves islet transplantation

BACKGROUND

Islet transplantation has the potential for treating type I diabetes; however, its widespread clinical application is limited by the massive apoptotic cell death and poor revascularization of transplanted islet grafts.

METHODS

We constructed a surface-modified adenoviral vector with RGD (Arg-Gly-Asp) sequences encoding human X-linked inhibitor of apoptosis and hepatocyte growth factor (RGD-Adv-hHGF-hXIAP). In vitro transgene expression in human islets was determined by enzyme-liniked immunosorbent assay. RGD-Adv-hHGF-hXIAP-transduced human islets were transplanted under the kidney capsule of streptozotocin-induced diabetic NOD/SCID mice. The blood glucose levels of mice were measured weekly. The kidneys bearing islets were isolated at the end of the experiment and subjected to immunofluorescence staining.

RESULTS

The transduction efficiency on human islets was significantly improved using RGD-modified adenovirus. HGF and XIAP gene expressions were dose-dependent after viral transduction. When exposed to a cocktail of inflammatory cytokines, RGD-Adv-hHGF-hXIAP-transduced human islets showed decreased caspase 3 activity and reduced apoptotic cell death. Prolonged normoglycemic control could be achieved by transplanting RGD-Adv-hHGF-hXIAP-transduced human islets. Immunofluorescence staining of kidney sections bearing RGD-Adv-hHGF-hXIAP-transduced islets was positive for insulin and von Willebrand factor (vWF) at 200 days after transplantation.

CONCLUSIONS

These results indicated that ex vivo transduction of islets with RGD-Adv-hHGF-hXIAP decreased apoptotic islet cell death and improved islet revascularization, and eventually might improve the outcome of human islet transplantation.

Mesenchymal stem cell-based therapy

Mesenchymal stem cells (MSCs) are multipotent adult stem cells which have self-renewal capacity and differentiation potential into several mesenchymal lineages including bones, cartilages, adipose tissues and tendons. MSCs may repair tissue injuries and prevent immune cell activation and proliferation. Immunomodulation and secretion of growth factors by MSCs have led to realizing the true potential of MSC-based cell therapy. The use of MSCs as immunomodulators has been explored in cell/organ transplant, tissue repair, autoimmune diseases, and prevention of graft vs host disease (GVHD). This review focuses on the clinical applications of MSC-based cell therapy, with particular emphasis on islet transplantation for treating type I diabetes.

Mesenchymal stem cells as a gene delivery vehicle for successful islet transplantation

PURPOSE

To evaluate the efficacy of human bone marrow-derived mesenchymal stem cells (hBMSCs) as gene delivery vehicles to simultaneously express human hepatocyte growth factor (HGF) and interleukin 1 receptor antagonist (IL-1Ra) to improve the outcome of islet transplantation.

METHODS

Morphology and islet-binding affinity of hBMSCs were checked by microscope. The expression of target genes and endogenous genes was determined by ELISA. Protection of islets by hBMSCs was evaluated in vitro by Calcein-AM/Propidium Iodide staining and in vivo by allogeneic islet transplantation study. Function and revascularization of islets was evaluated by immune fluorescence study.

RESULTS

Non-donor-specific hBMSCs showed strong binding affinity to human islets and protected viability and function. Transduction of hBMSCs with adenovirus encoding human HGF and human IL-1Ra (Adv-hHGF-hIL-1Ra) prior to co-culturing with islets further protected from apoptotic cell death, helped maintain 3D structures and morphology, and enhanced insulin secretion. Transplantation of human islets reconstituted with Adv-hHGF-hIL-1Ra transduced hBMSCs under the kidney capsule of streptozotocin-induced diabetic non-obese diabetic/severe combined immunodeficient (NOD-SCID) mice reversed diabetes by reducing blood glucose levels to ≤ 200 mg/dL for up to 15 weeks and reduced the number of islets required to achieving normoglycemia. Blood glucose levels of mice transplanted with islets alone reversed to ≥ 500 mg/dL 4 weeks post-transplantation.

CONCLUSIONS

Results indentified hBMSCs as effective gene delivery vehicles to improve the outcome of islet transplantation.

Genetically modified mesenchymal stem cells for improved islet transplantation

The use of adult stem cells for therapeutic purposes has met with great success in recent years. Among several types of adult stem cells, mesenchymal stem cells (MSCs) derived from bone marrow (BM) and other sources have gained popularity for basic research and clinical applications because of their therapeutic potential in treating a variety of diseases. Because of their tissue regeneration potential and immune modulation effect, MSCs were recently used as cell-based therapy to promote revascularization, increase pancreatic β-cell proliferation, and avoid allograft rejection in islet transplantation. Taking advantage of the recent progress in gene therapy, genetically modified MSCs can further enhance and expand the therapeutic benefit of primary MSCs while retaining their stem-cell-like properties. This review aims to gain a thorough understanding of the current obstacles to successful islet transplantation and discusses the potential role of primary MSCs before or after genetic modification in islet transplantation.

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.

XIAP gene expression protects β-cells and human islets from apoptotic cell death

Islet transplantation has the potential to treat type I diabetes, however, its clinical application is limited due to the massive apoptotic cell death and other post-transplantation challenges to islet grafts. Therefore, the objective of this study was to determine whether ex vivo transduction of rat insulin producing INS-1E cells and human islets with adenoviral vector encoding human X-linked inhibitor of apoptosis (Adv-hXIAP) can protect them from inflammatory cytokines and improve their viability and function. There was dose dependent XIAP gene expression. XIAP expression led to decrease in the activities of caspase 3/7, 8 and 9, resulting in reduced apoptotic cell death induced by a cocktail of inflammatory cytokines such as IL-1β, TNFα, and IFNγ. Prolonged normoglycemic control could be achieved by transplantation of Adv-XIAP transduced human islets under the kidney capsule of streptozotocin induced diabetic NOD-SCID mice. Immunohistological staining of the islets bearing kidney sections at day 42 after transplantation was positive for insulin. Moreover, the protective effect of XIAP was reversed by coadministration of XIAP inhibitor embelin. These results indicate that ex vivo transduction of islets with Adv-XIAP will decrease cytokine induced apoptosis and improve the outcome of islet transplantation.

In vivo non-viral gene delivery of human vascular endothelial growth factor improves revascularisation and restoration of euglycaemia after human islet transplantation into mouse liver

AIMS/HYPOTHESIS

Delivery of the gene for human vascular endothelial growth factor (VEGF, also known as VEGFA) to both the transplanted islets and the surrounding tissue may promote islet revascularisation and survival. We previously showed the effective delivery of VEGF gene to rat myocardium by an ultrasound-mediated gene-transfer method named ultrasound-targeted microbubble destruction (UTMD). Here we examined the effect of non-viral VEGF delivery using UTMD on transplanted islets in vivo.

METHODS

A marginal number of human islets were transplanted into livers of mice which were a model for diabetes. Then, non-viral plasmid vectors encoding VEGF (VEGF group, n = 11) or the gene for green fluorescent protein (GFP) (GFP group, n = 7) were introduced into the host liver by UTMD. Transplantation without gene delivery was performed as a control (no-UTMD group, n = 8). Blood glucose, serum human insulin, C-peptide levels and the revascularisation in graft islets were evaluated.

RESULTS

Restoration of euglycaemia occurred in 13% in the no-UTMD group and 14% in the GFP group, whereas 73% mice in the VEGF group became euglycaemic at day 30 (p < 0.05 in no-UTMD vs VEGF). Serum human insulin and C-peptide were significantly higher in the VEGF group at day 32 (insulin: no-UTMD, 17 +/- 8; GFP, 37 +/- 17; VEGF, 109 +/- 26 pmol/l, respectively, p < 0.05; C-peptide: no-UTMD, 68 +/- 38; GFP, 115 +/- 58; VEGF, 791 +/- 230 pmol/l, respectively, p < 0.05). Vessel density in graft islets was significantly higher in the VEGF group (no-UTMD, 169 +/- 36; GFP, 227 +/- 39; VEGF, 649 +/- 51 counts/mm(2), respectively, p < 0.05).

CONCLUSIONS/INTERPRETATION

Delivery of VEGF gene to host liver using UTMD promoted islet revascularisation after islet transplantation and improved the restoration of euglycaemia.

Gene therapy in diabetes

Type 1 diabetes (T1D) is a chronic autoimmune disease, whereby auto-reactive cytotoxic T cells target and destroy insulin-secreting β-cells in pancreatic islets leading to insulin deficiency and subsequent hyperglycemia. These individuals require multiple daily insulin injections every day of their life without which they will develop life-threatening diabetic ketoacidosis (DKA) and die. Gene therapy by viral vector and non-viral transduction may be useful techniques to treat T1D as it can be applied from many different angles; such as the suppression of autoreactive T cells to prevent islet destruction (prophylactic) or the replacement of the insulin gene (post-disease). The need for a better method for providing euglycemia arose from insufficient numbers of cadaver islets for transplantation and the immunosuppression required post-transplant. Ectopic expression of insulin or islet modification have been examined, but not perfected. This review examines the various gene transfer methods, gene therapy techniques used to date and promising novel techniques for the maintenance of euglycemia in the treatment of T1D.

Gene expression and silencing for improved islet transplantation

Islet transplantation has great potential as an effective means of treating type 1 diabetes. However, its successful application greatly depends on the rapid revascularization of islets and prevention from their apoptotic cell death. We co-expressed human vascular endothelial growth factor (hVEGF) and human interleukin-1 receptor antagonist (hIL-1Ra) after transduction of human islets with Adv-hVEGF-hIL-1Ra. Since hepatocyte growth factor (HGF) increases beta-cell proliferation and promotes revascularization of islets, we also constructed Adv-hHGF-hIL-1Ra. There was dose and time dependent expression of hVEGF and hIL-1Ra or hHGF and hIL-1Ra by islets, which led to decrease in caspase-3 activity and apoptosis induced by a cocktail of TNF-alpha, IL-1beta and IFN-gamma. Compared to non-treated islets, transduction of islets with these bipartite Adv vectors prior to transplantation under the kidney capsules of diabetic NOD-SCID mice reduced the blood glucose levels, and increased serum insulin and c-peptide levels. Immunohistochemical staining of the islet bearing kidney sections was positive for human insulin, growth factor (hVEGF or hHGF) and von Willebrand factor. Transduction with Adv-caspase-3-shRNA also prevented islets from cytokine induced apoptosis and improved islet transplantation. In conclusion, bipartite Adv vector efficiently co-expressed both growth factor and antiapoptotic genes or shRNA targeting pro-apoptotic genes, decreases apoptosis and improves the outcome of islet transplantation.