Simmyung Yook

Surface modification of pancreatic islets using heparin-DOPA conjugate and anti-CD154 mAb for the prolonged survival of intrahepatic transplanted islets in a xenograft model

This study proposes a combination method of using 3,4-dihydorxy-l-phenylalanine (DOPA) conjugated heparin (heparin-DOPA) and a low dose of anti-CD154 monoclonal antibody (MR-1) treatment to improve the survival time of intrahepatic islet xenograft. To inhibit instant blood mediated inflammatory reactions, heparin-DOPA was directly grafted to the pancreatic islet surface. The surface coverage of heparin-DOPA, the viability and functionality of heparin-DOPA grafted islets were evaluated. In addition, the combined effect of grafted heparin-DOPA and a low dose of MR-1 (a T-cell targeting immunosuppressive drug) on the survival of islet was evaluated in a xenograft model. Both unmodified islets and heparin-DOPA grafted islets were completely rejected within 2 weeks after intraportal transplantation. However, when 0.1 mg/mouse of MR-1 was administered (at day 0, 2, 4, 6 of transplantation) to 11 mice that had heparin-DOPA grafted islets transplanted to, seven out of the recipients maintained normoglycemia over 60 days. Therefore, we propose that a developed combinatory immunoprotection protocol of surface modification of pancreatic islets using heparin-DOPA with a low dose of MR-1 can be effective in prolonging the survival rate of transplanted islets in a xenograft model.

Functional enhancement of beta cells in transplanted pancreatic islets by secretion signal peptide-linked exendin-4 gene transduction.

This study assessed whether the newly designed exendin-4 (Ex-4) gene with highly releasable characteristics could enhance the beta cell function, thereby attenuating the essential islet mass required to cure diabetes. We constructed a lentivirus system encoding for a highly releasable secretion signal peptide, the peptide linked Ex-4 (SP-Ex-4) gene. After the transduction of lentivirus encoding for SP-Ex-4 (LV-SP-Ex-4) gene into the islets, the therapeutic effects of Ex-4 secreted were evaluated by conducting glucose-stimulated insulin secretion and cytokine- or hypoxia-induced apoptosis. Additionally, the effect of reduced islet numbers for transplantation was evaluated via in vivo models. The transduction of LV-SP-Ex-4 gene did not affect the viability of islets. In diabetic animal models, 50 islets expressing Ex-4 were transplanted to cure the diabetic nude mice, whereas at least 150 untransduced islets had to be transplanted to cure the diabetic nude mice. When the transduced islets were transplanted into diabetic immunocompetent mice, the survival rate of the mice was 18.0±4.9 days; however, when the untransduced islets were transplanted, they were rejected within 10.0±0.6 days. Therefore, the highly releasable Ex-4 could enhance the beta cell function with slightly enhanced viability of transplanted islets, presenting as a potential technology for overcoming islet shortage.

Synergistic Effect of Surface Modification With Poly(ethylene glycol) and Immunosuppressants on Repetitive Pancreatic Islet Transplantation Into Antecedently Sensitized Rat

BACKGROUND Polymeric modification of islet surface is highly effective in preventing transplanted islets against host immune reactions. However, grafted islets are eventually rejected by the host immune reaction. Thus, repetitive islet transplantation is needed to treat type 1 diabetic patients experiencing graft rejection. We explored whether using poly(ethylene glycol) (PEG) as surface camouflage of islets (PEGylation) can be an affordable immunoprotective remedy for repeated islet transplantation. METHODS The surface coverage of PEG was evaluated in vitro. The viability of PEGylated islets cocultured with sensitized or nonsensitized splenocytes was evaluated using lactate dehydrogenase assay. In addition, the effect of surface modification on immunoprotection for repetitively transplanted islets was evaluated in a sensitized rat model. RESULTS Unmodified islets transplanted in combination with Cyclosporine (CsA) and anti-CD4 monoclonal antibody (OX-38) into the sensitized recipients did not maintain a normal level of blood glucose over 20 days. Interestingly, however, three of the five recipients became normoglycemic up to 30 days when PEGylated islets were transplanted in combination with CsA and OX-38. CONCLUSION These results demonstrated that PEGylation alone was not an affordable immunoprotective method, but the combination of CsA and OX-38 along with PEGylation showed a highly improved a synergic effects on the inhibition of sensitized host immune reactions.

Molecularly engineered islet cell clusters for diabetes mellitus treatment.

Pancreatic islet transplantation is a promising method for curing diabetes mellitus. We proposed in this study a molecularly engineered islet cell clusters (ICCs) that could overcome problems posed by islet transplantation circumstances and hosts immune reactions. A gene containing highly releasable exendin-4, an insulinotropic protein, was delivered into single islet cells to enhance glucose sensitivity; thereafter, the cells were reaggregated into small size ICCs. Then the surface of ICCs was modified with biocompatible poly(ethylene glycol)-lipid (PEG) (C18) for preventing immune reactions. The regimen of ICCs with low doses of anti-CD154 mAb and tacrolimus could effectively maintain the normal glucose level in diabetic mice. This molecularly engineered PEG-Sp-Ex-4 ICC regimen prevented cell death in transplantation site, partly through improving the regulation of glucose metabolism and by preventing hypoxia- and immune response-induced apoptosis. Application of this remedy is also potentially far-reaching; one would be to help overcome islet supply shortage due to the limited availability of pancreas donors and reduce the immunosuppressant regimens to eliminate their adverse effects.

Effects of surface camouflaged islet transplantation on pathophysiological progression in a db/db type 2 diabetic mouse model

To investigate the inhibition effects of pancreatic islet transplantation on the progression of obese type 2 diabetes, we analyzed the effects of surface camouflaged islet transplantation on delaying the disease progression in a db/db diabetic mouse model. Surface camouflaged islets using 6-arm-PEG-catechol were transplanted in db/db diabetic mice. The fat accumulation and toxicity in the liver, the expansion of islets in the pancreas, and the size change of abdominal adipocyte were analyzed. In addition, the blood glucose control, insulin levels and immunohistochemical staining of recovered tissues were analyzed after transplantation. Then co-administration of anti-CD154 monoclonal antibody and Tacrolimus (IT group) deterred the pathophysiological progression of obese type 2 diabetes. At day 3 of transplantation, the serum insulin concentration of IT group was increased compared to the db/db diabetic mice group. The immunohistochemical studies demonstrated that the mass of 6-arm-PEG-catechol grafted islet was preserved in the transplantation site for 14 days. Surface modification using 6-arm-PEG-catechol effectively inhibited the immune cell infiltration and activation of host immune cells when immunosuppressive drug was given to the db/db type 2 diabetes mice. Therefore, 6-arm-PEG-catechol grafted islets effectively restored the insulin secretion in islet recipients and prevented the disease progression in type 2 diabetes.

Tissue adhesive FK506–loaded polymeric nanoparticles for multi–layered nano–shielding of pancreatic islets to enhance xenograft survival in a diabetic mouse model

This study aims to develop a novel surface modification technology to prolong the survival time of pancreatic islets in a xenogenic transplantation model, using 3,4-dihydroxyphenethylamine (DOPA) conjugated poly(lactide-co-glycolide)-poly(ethylene glycol) (PLGA-PEG) nanoparticles (DOPA-NPs) carrying immunosuppressant FK506 (FK506/DOPA-NPs). The functionalized DOPA-NPs formed a versatile coating layer for antigen camouflage without interfering the viability and functionality of islets. The coating layer effectively preserved the morphology and viability of islets in a co-culture condition with xenogenic lymphocytes for 7 days. Interestingly, the mean survival time of islets coated with FK506/DOPA-NPs was significantly higher as compared with that of islets coated with DOPA-NPs (without FK506) and control. This study demonstrated that the combination of surface camouflage and localized low dose of immunosuppressant could be an effective approach in prolonging the survival of transplanted islets. This newly developed platform might be useful for immobilizing various types of small molecules on therapeutic cells and biomaterial surface to improve the therapeutic efficacy in cell therapy and regenerative medicine.

Delivery of Pancreatic Islets and Single Dose Local Immune Suppression Into Subcutaneous Space Using Injectable Hydrogel Provides Indefinite Survival of the Graft in Mouse Model of Diabetes

Introduction Pancreatic islet transplantation is a promising technique to treat type 1 diabetes. Long-term survival of the graft is required for a successful islet transplantation. Repeated use of immunosuppressive drugs after organ/cell transplantation often leads to severe adverse effects including nephrotoxicity, hepatotoxicity, and opportunistic infections. Thus, development of a local immunosuppression protocol is necessary to improve the islet graft survival in clinics. Materials and Methods Pancreatic islets from Sprague-Dawley rats were transplanted into the subcutaneous space of B6 mice using injectable hydrogel. Three major groups were prepared for transplantation. (1) Islets transplanted FK506-loaded poly(lactic-co-glycolic acid) microspheres (10 mg/kg), (2) Islets transplanted with clodronate liposomes (6.25 mg/kg), and (3) Islet transplanted with the combination of both immune suppressants. The suspension of islets and immune suppressants in Matrigel was then injected into the subcutaneous space over the flanks of streptozocin-induced diabetic mice. Results Islets transplanted without any immunosuppression were rejected within two weeks. In contrast, the islets transplanted with the single immunosuppressive regimen of FK506 or clodronate improved survival rate compared with that of the control mice. More interestingly, the graft transplanted using the combination of both immune suppressants survived indefinitely. Immunological studies revealed that the immunosuppressive cocktail inhibited the proliferation of immune cells residing at the peripheral lymph nodes. Interestingly, the systemic immune system of the transplanted mice remained unaffected. Furthermore, histochemical analysis revealed the intact morphology of the islets at the transplanted site when codelivered with the immunosuppressant. Discussion Antigen presenting cells and T-cells orchestrate the immune rejection cascade. Macrophage depletion by the liposomal clodronate and the inhibition of T-cell activation by FK506 completely blocked the immune rejection cascade in the immune competent mice. The inhibition of immune stimulation in the peripheral lymph nodes improved the islet grafted into the subcutaneous space. Thus, the use of local immune suppression is an effective approach to enhance the survival of the transplanted islets. Conclusion We developed a protocol for the local codelivery of pancreatic islets and immune suppressive agents. Indefinite graft survival was obtained with the use of macrophage depleting agent and T-cell inhibitor. The single dose of local immune suppression during transplantation may avoid toxic effects associated with a long-term use of immune suppressive agents in clinics. National Research Foundation of Korea (NRF) Grant nos: 2015R1A5A2009124 and 2017R1D1A1B03027831. Korea Health Industry Development Institute (KHIDI) Grant no: HI16C1767.

Single synchronous delivery of FK506-loaded polymeric microspheres with pancreatic islets for the successful treatment of streptozocin-induced diabetes in mice

Abstract Immune rejection after transplantation is common, which leads to prompt failure of the graft. Therefore, to prolong the survival time of the graft, immunosuppressive therapy is the norm. Here, we report a robust immune protection protocol using FK506-loaded microspheres (FK506M) in injectable hydrogel. Pancreatic islets were codelivered with the FK506M into the subcutaneous space of streptozocin-induced diabetic mice. The islets codelivered with 10 mg/kg FK506M maintained normal blood glucose levels during the study period (survival rate: 60%). However, transplantation of islets and FK506M at different sites hardly controlled the blood glucose level (survival rate: 20%). Immunohistochemical analysis revealed an intact morphology of the islets transplanted with FK506M. In addition, minimal number of immune cells invaded inside the gel of the islet-FK506M group. The single injection of FK506M into the local microenvironment effectively inhibited immune rejection and prolonged the survival time of transplanted islets in a xenograft model.

Dose optimization of tacrolimus for improving survival time of PEGylated islets in a rat-to-mouse xenograft model

Improvements in preventing pancreatic islet rejection are needed for successful treatment of type 1 diabetes. Our objective was to develop an optimized protocol combining modification of islets with polyethyleneglycol (PEG) chains and administration of tacrolimus (FK506, Prograf), an immunosuppressive drug for preventing rejection following transplantation. Freshly isolated islets were incubated with different concentrations (0.25, 1.00, 10.00, and 25.00%) of FITC-labeled mPEG-SCM (MW. 20 KDa) for various incubation times. 1% mPEG-SCM incubated with islets for 1 h is optimized surface coverage condition without cell toxicity. In addition, in order to optimize the concentration of tacrolimus (FK506, Prograf), different concentrations (0.1, 0.5 or 2.0 mg/kg) were injected into the diabetic mice following transplantation of PEGylated islets. The PEGylated islet survival time in mice injected daily with 0.1 mg/kg and 0.5 mg/kg of tacrolimus was significantly better than in the group without tacrolimus injection. The graft survival time in mice injected daily with 2.00 mg/kg of exhibited no prolonged survival time. Finally, immunohistochemical staining of left kidney containing PEGylated islets (injected with 0.1 mg/kg of tacrolimus) demonstrated strong staining for insulin, glucagon, and somatostatin but very weak CD20 staining was observed in the islet transplanted area. In conclusion, 1% mPEG-SCM incubated with islets for 1 h was the optimal condition for PEGylation without affecting the cell viability. A dose of tacrolimus between 0.1-0.5 mg/kg was highly effective for inhibiting immune cell activation. These results are promising for their application in developing a novel immunosuppressive protocol for successful pancreatic islet transplantation in the treatment of type 1 diabetes.

Improvement of beta cell function in intraportal transplantation of islet cell cluster using secretion signal peptide-linked exendin-4 gene

One of the major obstacles to successful intraportal islet transplantation is the early portal vein embolization elicited by the infused islets. Thus, reducing the size and the number of islets is an important process to alleviate the damage of liver after intraportal islet transplantation. In our previous studies, we developed a strategy to construct genetically modified islet cell clusters (ICCs) and demonstrated their superiority in maintaining better viability and functionality in vivo. In this study, signal-peptide linked exendin-4 transduced islet cell clusters (Sp-Ex-4 ICCs) were used to reverse diabetes after intraportal islet transplantation in hyperglycemic mouse model. Group of mice receiving 500 islet equivalent (IEQ) of unmodified ICCs failed to restore normoglycemia following transplantation. Although 500 IEQ of ICCs was insufficient to reverse hyperglycemia in diabetic mice, no significant acute liver damage or life-threatening liver embolization was observed. When 1000 IEQ ICCs were infused into the portal vein, all animals died within 24 h post-surgery. In order to clarify the effect of Sp-Ex-4 gene transduction in improving ICCs functionality, 500 IEQ of Sp-Ex-4 ICCs were infused into the portal vein of diabetic mice. Following transplantation, 75% of diabetic mice returned to normoglycemia and the survival fraction was 100%. In conclusion, intraportal transplantation of Sp-Ex-4 ICCs successfully reversed diabetes in hyperglycemic mice by reducing the mass required for the treatment. Therefore, intraportal transplantation of small islets (genetically engineered ICCs) can be proposed as a new strategy to overcome early graft embolization after intraportal transplantation.