Achieving and maintaining insulin independence in human islet transplant recipients

Aptabinding of tumor necrosis factor-α (TNFα) inhibits its proinflammatory effects and alleviates islet inflammation

Pancreatic islet cell transplantation (ICT) has emerged as an effective therapy for diabetic patients lacking endogenous insulin production. However, the islet graft function is compromised by a nonspecific inflammatory and thrombotic reaction known as the instant blood-meditated inflammatory reaction (IBMIR). Here, we report the characterization of four single-stranded DNA aptamers that bind specifically to TNFα - a pivotal cytokine that causes proinflammatory signaling during the IBMIR process - using single molecule binding analysis and functional assays as a means to assess the aptamers' ability to block TNFα activity and inhibiting the downstream proinflammatory gene expression in the islets. Our single-molecule fluorescence analyses of mono- and multivalent aptamers showed that they were able to bind effectively to TNFα with monoApt2 exhibiting the strongest binding (Kd  ∼ 0.02 ± 0.01 nM), which is ∼3 orders of magnitude smaller than the Kd of the other aptamers. Furthermore, the in vitro cell viability analysis demonstrated an optimal and safe dosage of 100 μM for monoApt2 compared to 50 μM for monoApt1 and significant protection from proinflammatory cytokine-mediated cell death. More interestingly, monoApt2 reversed the upregulation of IBMIR mediating genes induced by TNFα in the human islets, and this was comparable to established TNFα antagonists. Both monoaptamers showed high specificity and selectivity for TNFα. Collectively, these findings suggest the potential use of aptamers as anti-inflammatory and localized immune-modulating agents for cellular transplant therapy.

Decellularized Whole-Organ Pre-vascularization: A Novel Approach for Organogenesis

Introduction: Whole-organ decellularization is an attractive approach for three-dimensional (3D) organ engineering. However, progress with this approach is hindered by intra-vascular blood coagulation that occurs after in vivo implantation of the re-cellularized scaffold, resulting in a short-term graft survival. In this study, we explored an alternative approach for 3D organ engineering through an axial pre-vascularization approach and examined its suitability for pancreatic islet transplantation. Methods: Whole livers from male Lewis rats were decellularized through sequential arterial perfusion of detergents. The decellularized liver scaffold was implanted into Lewis rats, and an arteriovenous bundle was passed through the scaffold. At the time of implantation, fresh bone marrow preparation (BM; n = 3), adipose-derived stem cells (ADSCs; n = 4), or HBSS (n = 4) was injected into the scaffold through the portal vein. After 5 weeks, around 2,600 islet equivalents (IEQs) were injected through the portal vein of the scaffold. The recipient rats were rendered diabetic by the injection of 65 mg/kg STZ intravenously 1 week before islet transplantation and were followed up after transplantation by measuring the blood glucose and body weight for 30 days. Intravenous glucose tolerance test was performed in the cured animals, and samples were collected for immunohistochemical (IHC) analyses. Micro-computed tomography (CT) images were obtained from one rat in each group for representation. Results: Two rats in the BM group and one in the ADSC group showed normalization of blood glucose levels, while one rat from each group showed partial correction of blood glucose levels. In contrast, no rats were cured in the HBSS group. Micro-CT showed evidence of sprouting from the arteriovenous bundle inside the scaffold. IHC analyses showed insulin-positive cells in all three groups. The number of von-Willebrand factor-positive cells in the islet region was higher in the BM and ADSC groups than in the HBSS group. The number of 5-bromo-2'-deoxyuridine-positive cells was significantly lower in the BM group than in the other two groups. Conclusions: Despite the limited numbers, the study showed the promising potential of the pre-vascularized whole-organ scaffold as a novel approach for islet transplantation. Both BM- and ADSCs-seeded scaffolds were superior to the acellular scaffold.

Non-Invasive Monitoring of Oxygen Tension and Oxygen Transport Inside Subcutaneous Devices After H2S Treatment

Medical devices for cell therapy can be improved through prevascularization. In this work we study the vascularization of a porous polymer device, previously used by our group for pancreatic islet transplantation with results indicating improved glycemic control. Oxygen partial pressure within such devices was monitored non-invasively using an optical technique. Oxygen-sensitive tubes were fabricated and placed inside devices prior to subcutaneous implantation in nude mice. We tested the hypothesis that vascularization will be enhanced by administration of the pro-angiogenic factor hydrogen sulfide (H2S). We found that oxygen dynamics were unique to each implant and that the administration of H2S does not result in significant changes in perfusion of the devices as compared with control. These observations suggest that vascular perfusion and density are not necessarily correlated, and that the rate of vascularization was not enhanced by the pro-angiogenic agent.

Pancreatic Islet Transplantation in Humans: Recent Progress and Future Directions

Pancreatic islet transplantation has become an established approach to β-cell replacement therapy for the treatment of insulin-deficient diabetes. Recent progress in techniques for islet isolation, islet culture, and peritransplant management of the islet transplant recipient has resulted in substantial improvements in metabolic and safety outcomes for patients. For patients requiring total or subtotal pancreatectomy for benign disease of the pancreas, isolation of islets from the diseased pancreas with intrahepatic transplantation of autologous islets can prevent or ameliorate postsurgical diabetes, and for patients previously experiencing painful recurrent acute or chronic pancreatitis, quality of life is substantially improved. For patients with type 1 diabetes or insulin-deficient forms of pancreatogenic (type 3c) diabetes, isolation of islets from a deceased donor pancreas with intrahepatic transplantation of allogeneic islets can ameliorate problematic hypoglycemia, stabilize glycemic lability, and maintain on-target glycemic control, consequently with improved quality of life, and often without the requirement for insulin therapy. Because the metabolic benefits are dependent on the numbers of islets transplanted that survive engraftment, recipients of autoislets are limited to receive the number of islets isolated from their own pancreas, whereas recipients of alloislets may receive islets isolated from more than one donor pancreas. The development of alternative sources of islet cells for transplantation, whether from autologous, allogeneic, or xenogeneic tissues, is an active area of investigation that promises to expand access and indications for islet transplantation in the future treatment of diabetes.

Carnosine protects pancreatic beta cells and islets against oxidative stress damage

Islet transplantation is a valid therapeutic option for type 1 diabetes treatment. However, in this procedure one of the major problems is the oxidative stress produced during pancreatic islet isolation. The aim of our study was to evaluate potential protective effects of L-carnosine and its isomer D-carnosine against oxidative stress. We evaluated the carnosine effect on cell growth, cell death, insulin production, and the main markers of oxidative stress in rat and murine stressed beta cell lines as well as in human pancreatic islets. Both isomers clearly inhibited hydrogen peroxide induced cytotoxicity, with a decrease in intracellular reactive oxygen and nitrogen species, prevented hydrogen peroxide induced apoptosis/necrosis, nitrite production, and reduced glucose-induced insulin secretion. In addition, NF-κB expression/translocation and nitrated protein induced in stressed cells was significantly reduced. Furthermore, both isomers improved survival and function, and decreased reactive oxygen and nitrogen species, and nitrite and nitrotyrosine production in human islets cultured for 1, 3, and 7 days. These results seem to indicate that both L and D-carnosine have a significant cytoprotective effect by reducing oxidative stress in beta cell lines and human islets, suggesting their potential use to improve islet survival during the islet transplantation procedure.

Polymer scaffolds for pancreatic islet transplantation - Progress and challenges

Pancreatic-islet transplantation is a safe and noninvasive therapy for type 1 diabetes. However, the currently applied site for transplantation, ie, the liver, is not the optimal site for islet survival. Because the human body has shortcomings in providing an optimal site, artificial transplantation sites have been proposed. Such an artificial site could consist of a polymeric scaffold that mimics the pancreatic microenvironment and supports islet function. Recently, remarkable progress has been made in the technology of engineering scaffolds. The polymer-islet interactions, the site of implantation, and scaffold prevascularization are critical factors for success or failure of the scaffolds. This article critically reviews these factors while also discussing translation of experimental studies to human application as well as the steps required to create a clinically applicable prevascularized, retrievable scaffold for implantation of insulin-producing cells for treatment of type 1 diabetes mellitus.

Regulated Cell Death Seen through the Lens of Islet Transplantation

Clinical islet transplantation effectively restores euglycemia and corrects glycosylated hemoglobin in labile type 1 diabetes mellitus (T1DM). Despite marked improvements in islet transplantation outcomes, acute islet cell death remains a substantial obstacle that compromises long-term engraftment outcomes. Multiple organ donors are routinely required to achieve insulin independence. Therapeutic agents that ameliorate cell death and/or control injury-related inflammatory cascades offer potential to improve islet transplant success. Apoptotic cell death has been identified as a major contributor to cellular demise and therapeutic strategies that subvert initiation and consequences of apoptotic cell death have shown promise in pre-clinical models. Indeed, in numerous pathologies and diseases apoptosis has been the most extensively described form of regulated cell death. However, recent identification of novel, alternative regulated cell death pathways in other disease states and solid organ transplantation suggest that these additional pathways may also have substantial relevance in islet transplantation. These regulated, non-apoptotic cell death pathways exhibit distinct biochemical characteristics but have yet to be fully characterized within islet transplantation. We review herein the various regulated cell death pathways and highlight their relative potential contributions to islet viability, engraftment failure and islet dysfunction.

Combination Immunotherapy for Type 1 Diabetes

PURPOSE OF REVIEW

Type 1 diabetes (T1D) is an autoimmune disease marked by β-cell destruction. Immunotherapies for T1D have been investigated since the 1980s and have focused on restoration of tolerance, T cell or B cell inhibition, regulatory T cell (Treg) induction, suppression of innate immunity and inflammation, immune system reset, and islet transplantation. The purpose of this review is to provide an overview and lessons learned from single immunotherapy trials, describe recent and ongoing combination immunotherapy trials, and provide perspectives on strategies for future combination clinical interventions aimed at preserving insulin secretion in T1D.

RECENT FINDINGS

Combination immunotherapies have had mixed results in improving short-term glycemic control and insulin secretion in recent-onset T1D. A handful of studies have successfully reached their primary end-point of improved insulin secretion in recent-onset T1D. However, long-term improvements glycemic control and the restoration of insulin independence remain elusive. Future interventions should focus on strategies that combine immunomodulation with efforts to alleviate β-cell stress and address the formation of antigens that activate autoimmunity.

Stimulation of vascularization of a subcutaneous scaffold applicable for pancreatic islet-transplantation enhances immediate post-transplant islet graft function but not long-term normoglycemia

The liver as transplantation site for pancreatic islets is associated with significant loss of islets, which can be prevented by grafting in a prevascularized, subcutaneous scaffold. Supporting vascularization of a scaffold to limit the period of ischemia is challenging and was developed here by applying liposomes for controlled release of angiogenic factors. The angiogenic capacity of platelet-derived growth factor, vascular endothelial growth factor, acidic fibroblast growth factor (aFGF), and basic FGF were compared in a tube formation assay. Furthermore, the release kinetics of different liposome compositions were tested. aFGF and L-α-phosphatidylcholine/cholesterol liposomes were selected to support vascularization. Two dosages of aFGF-liposomes (0.5 and 1.0 μg aFGF per injection) were administered weekly for a month after which islets were transplanted. We observed enhanced efficacy in the immediate post-transplant period compared to the untreated scaffolds. However, on the long-term, glucose levels of the aFGF treated animals started to increase to diabetic levels. These results suggest that injections with aFGF liposomes do improve vascularization and the immediate restoration of blood glucose levels but does not facilitate the long-term survival of islets. Our data emphasize the need for long-term studies to evaluate potential beneficial and adverse effects of vascularization protocols of scaffolds. © 2017 Wiley Periodicals, Inc. J Biomed Mater Res Part A: 105A: 2533-2542, 2017.

Polyglycolic Acid Fibrous Scaffold Improving Endothelial Cell Coating and Vascularization of Islet

Background:

Improving islet graft revascularization has become a crucial task for prolonging islet graft survival. Endothelial cells (ECs) are the basis of new microvessels in an isolated islet, and EC coating has been demonstrated to improve the vascularization and survival of an islet. However, the traditional method of EC coating of islets has low efficiency in vitro. This study was conducted to evaluate the effect of a polyglycolic acid (PGA) scaffold on the efficiency of islet coating by ECs and the angiogenesis in the coated islet graft.

Methods:

A PGA fibrous scaffold was used for EC coating of islet culture and was evaluated for its efficiency of EC coating on islets and islet graft angiogenesis.

Results:

In in vitro experiments, we found that apoptosis index of ECs-coating islet in PGA group (27% ± 8%) was significantly lower than that in control group (83% ± 20%, P < 0.05) after 7 days culture. Stimulation index was significantly greater in the PGA group than in the control group at day 7 after ECs-coating (2.07 ± 0.31 vs. 1.80 ± 0.23, P < 0.05). vascular endothelial growth factor (VEGF) level in the PGA group was significantly higher than the coating in the control group after 7 days culture (52.10 ± 13.50 ng/ml vs. 16.30 ± 8.10 ng/ml, P < 0.05). Because of a tight, circumvallated, adhesive and three-dimensional growth microenvironment, islet cultured in a PGA scaffold had higher coating efficiency showing stronger staining intensity of enzyme than those in the control group after 14 days of culture following ECs-coating. For in vivo study, PGA scaffold significantly prolonged the average survival time of EC-coated islet graft after transplantation compared with control group (15.30 ± 5.60 days vs. 8.30 ± 2.45 days, P < 0.05). The angiogenesis and area of survived grafts were more in the PGA group compared with the control group by measuring the mean microvessel density (8.60 ± 1.21/mm² vs. 5.20 ± 0.87/mm², P < 0.05). In addition, expression of VEGF and tyrosin-protein kinase receptor (Tie-2) gene increased in PGA scaffold group than that in control group by real-time reverse transcription-polymerase chain reaction analysis.

Conclusions:

These results demonstrate that the efficiency of EC coating of islets was successfully increased by culturing ECs on a PGA scaffold. This method enhances the function, survival, and vascularization of isolated islets in vitro and in vivo.

Clinical pancreatic islet transplantation

Clinical pancreatic islet transplantation can be considered one of the safest and least invasive transplant procedures. Remarkable progress has occurred in both the technical aspects of islet cell processing and the outcomes of clinical islet transplantation. With >1,500 patients treated since 2000, this therapeutic strategy has moved from a curiosity to a realistic treatment option for selected patients with type 1 diabetes mellitus (that is, those with hypoglycaemia unawareness, severe hypoglycaemic episodes and glycaemic lability). This Review outlines the techniques required for human islet isolation, in vitro culture before the transplant and clinical islet transplantation, and discusses indications, optimization of recipient immunosuppression and management of adjunctive immunomodulatory and anti-inflammatory strategies. The potential risks, long-term outcomes and advances in treatment after the transplant are also discussed to further move this treatment towards becoming a more widely available option for patients with type 1 diabetes mellitus and eventually a potential cure.

Inactivation of p27kip1 Promoted Nonspecific Inflammation by Enhancing Macrophage Proliferation in Islet Transplantation

Islet transplantation suffers from low efficiency caused by nonspecific inflammation-induced graft loss after transplantation. This study reports increased islet loss and enhanced inflammatory response in p27-deficient mice (p27-/-) and proposes a possible mechanism. Compared with wild type, p27-/- mice showed more severe functional injury of islet, with increased serum levels of inflammatory cytokines IL-1 and TNF-α, inducing macrophage proliferation. Furthermore, the increased number, proapoptotic proteins, and nuclear factor-kappa b (NF-κB) phosphorylation status of the infiltrating macrophages were accompanied by increased TNF-α mRNA level of islet graft site in p27-/- mice. Moreover, in vitro, we found that macrophages were still activated and cocultured with islet and promoted islet loss even blocking the direct effect of TNF-α on islets. Malondialdehyde (MDA, an end product of lipid peroxidation) in islet and media were increased after cocultured with macrophages. p27 deficiency also increased macrophage proliferation and islet injury. Therefore, p27 inactivation promotes injury islet graft loss via the elevation of proliferation and inflammatory cytokines secretion in infiltrating macrophages which induced nonspecific inflammation independent of TNF-α/nuclear factor-kappa b pathway. This potentially represents a promising therapeutic target in improving islet graft survival.

Pancreas Transplantation: Past, Present, Future

Diabetes is the pandemic disease of the modern era, with 10% of these patients having type 1 diabetes mellitus. Despite the prevalence, morbidities, and associated financial burden, treatment options have not changed since the introduction of injectable insulin. To date, over 40,000 pancreas transplants have been performed globally. It remains the only known method for restoring glycemic control and thus curing type 1 diabetes mellitus. The aim of this review is to bring pancreatic transplantation out of the specialist realm, informing practitioners about this important procedure, so that they feel better equipped to refer suitable patients for transplantation and manage, counsel, and support when encountering them within their own specialty. This study was a narrative review conducted in October 2015, with OVID interface searching EMBASE and MEDLINE databases, using Timeframe: Inception to October 2015. Articles were assessed for clinical relevance and most up-to-date content, with articles written in English as the only inclusion criterion. Other sources used included conference proceedings/presentations and unpublished data from our institution (Oxford Transplant Centre). Pancreatic transplantation is growing and has quickly become the gold standard of care for patients with type 1 diabetes mellitus and renal failure. Significant improvements in quality of life and life expectancy make pancreatic transplant a viable and economically feasible intervention. It remains the most effective method of establishing and maintaining euglycemia, halting and potentially reversing complications associated with diabetes.

Beta-cell replacement therapy: current outcomes and future landscape

PURPOSE OF REVIEW

This article provides a summary of the current outcomes of β-cell replacement strategies, an algorithm for choosing a specific modality while highlighting associated advantages and disadvantages, and outlines remaining challenges and areas of active investigation in β-cell replacement therapy.

RECENT FINDINGS

The most recent reports of islet cell allotransplantation have shown improvements over previous eras and now rival some outcomes of pancreas alone transplantation. Active areas of investigation are focused on improving techniques for islet isolation, graft monitoring, and managing challenges posed by the innate and alloimmune systems.

SUMMARY

Patients with insulin-dependent diabetes who continue to experience life threatening hypoglycemia despite maximal medical management can benefit from β-cell replacement. Emerging nontransplant technologies have not provided a physiologic euglycemic state to the extent offered by transplantation. Islet transplantation eliminates hypoglycemic episodes/unawareness, facilitates normalization of hemoglobin A1c (HbA1c), decreases microvascular disease progression, and improves quality of life for patients with problematic diabetes. Mid- and long-term outcomes of islet transplantation performed at expert centers approximate those of registry reports of solitary pancreas transplant, whereas the complication profile is quite favorable.

Differentiation of human pluripotent stem cells into β-cells: Potential and challenges

Human embryonic stem cells (hESCs) and induced pluripotent stem cells (iPSCs) hold great potential as the basis for cell-based therapies of degenerative diseases, including diabetes. Current insulin-based therapies for diabetes do not prevent hyperglycaemia or the associated long-term organ damage. While transplantation of pancreatic islets can achieve insulin independence and improved glycemic control, it is limited by donor tissue scarcity, challenges of purifying islets from the pancreas, and the need for immunosuppression to prevent rejection of transplants. Large-scale production of β-cells from stem cells is a promising alternative. Recent years have seen considerable progress in the optimization of in vitro differentiation protocols to direct hESCs/iPSCs into mature insulin-secreting β-cells and clinical trials are now under way to test the safety and efficiency of hESC-derived pancreatic progenitor cells in patients with type 1 diabetes. Here, we discuss key milestones leading up to these trials in addition to recent developments and challenges for hESC/iPSC-based diabetes therapies and disease modeling.

The Impact of c-Fos/Activator Protein-1 Inhibition on Allogeneic Pancreatic Islet Transplantation

Unpreventable allograft rejection is one of the main problems in pancreatic islet transplantation (PIT). Therefore, it is imperative to develop a more effective immunosuppressive strategy. The blockade of transcription factors has been a central part of T cell-depleting immunosuppressive therapies, as typified by the use of calcineurin inhibitors. The inhibition of activator protein-1 (AP-1) offers a novel strategy for immunosuppression in PIT, although to date, no reports on the effects of AP-1 inhibition are available. In this study, we investigated the immunosuppressive effects of T-5224, a c-Fos/AP-1-selective inhibitor, on murine T cells activated by αCD3+αCD28 mAbs. T-5224 inhibited proliferation, CD25 up-regulation, and the production of IL-2 and interferon-γ. In addition, T-5224 blocked the nuclear translocation of c-Fos/AP-1 in activated murine T cells. In BALB/c (H-2(d) )-to-C57BL/6J (H-2(b) ) mouse PIT, the 2-week administration of T-5224 prolonged survival of 600 islet allografts in a dose-dependent manner. When combined with a 2-week low-dose tacrolimus, the T-5224 treatment markedly prolonged allograft survival to over 300 days, while the efficacy was indeterminate when transplanted islet allograft mass was reduced to 300. We conclude that the c-Fos/AP-1 inhibition by T-5224 is a potentially attractive strategy for allogeneic PIT.

Regulation of the JNK3 signaling pathway during islet isolation: JNK3 and c-fos as new markers of islet quality for transplantation

Stress conditions generated throughout pancreatic islet processing initiate the activation of pro-inflammatory pathways and beta-cell destruction. Our goal is to identify relevant and preferably beta-specific markers to assess the activation of beta-cell stress and apoptotic mechanisms, and therefore the general quality of the islet preparation prior to transplantation. Protein expression and activation were analyzed by Western blotting and kinase assays. ATP measurements were performed by a luminescence-based assay. Oxygen consumption rate (OCR) was measured based on standard protocols using fiber optic sensors. Total RNA was used for gene expression analyzes. Our results indicate that pancreas digestion initiates a potent stress response in the islets by activating two stress kinases, c-Jun N-terminal Kinase (JNK) and p38. JNK1 protein levels remained unchanged between different islet preparations and following culture. In contrast, levels of JNK3 increased after islet culture, but varied markedly, with a subset of preparations bearing low JNK3 expression. The observed changes in JNK3 protein content strongly correlated with OCR measurements as determined by the Spearman's rank correlation coefficient rho in the matching islet samples, while inversely correlating with c-fos mRNA expression . In conclusion, pancreas digestion recruits JNK and p38 kinases that are known to participate to beta-cell apoptosis. Concomitantly, the islet isolation alters JNK3 and c-fos expression, both strongly correlating with OCR. Thus, a comparative analysis of JNK3 and c-fos expression before and after culture may provide for novel markers to assess islet quality prior to transplantation. JNK3 has the advantage over all other proposed markers to be islet-specific, and thus to provide for a marker independent of non-beta cell contamination.

The current state of pancreas transplantation

For many patients with type 1 diabetes mellitus and selected patients with type 2 diabetes mellitus, a successful pancreas transplant is the only definitive long-term treatment that both restores euglycaemia without the risk of severe hypoglycaemia and prevents, halts or reverses secondary complications. These benefits come at the cost of major surgery and lifelong immunosuppression. Nevertheless, pancreas transplants are safe and effective, with patient survival rates currently >95% at 1 year and >88% at 5 years; graft survival rates are almost 85% at 1 year and >60% at 5 years. The estimated half-life of a pancreas graft is now 7-14 years. The improvements in graft survival are attributable to considerable reductions in technical failures and in immunologic graft losses. Pancreas recipients have reduced mortality compared with waiting candidates or patients with diabetes mellitus who undergo a kidney transplant alone. Pancreas transplants should be more frequently offered to nonuraemic patients with brittle diabetes mellitus to prevent the development of secondary diabetic complications and to avoid the need for a kidney transplant. Although the results of islet transplantation have also improved, islet recipients rarely maintain long-term insulin independence despite the use of multiple organ donor pancreases. Pancreas transplants and islet transplants should be considered complementary, not mutually exclusive, procedures that are chosen on the basis of the individual patient's surgical risk.

Collagen IV-modified scaffolds improve islet survival and function and reduce time to euglycemia

Islet transplantation on extracellular matrix (ECM) protein-modified biodegradable microporous poly(lactide-co-glycolide) scaffolds is a potential curative treatment for type 1 diabetes mellitus (T1DM). Collagen IV-modified scaffolds, relative to control scaffolds, significantly decreased the time required to restore euglycemia from 17 to 3 days. We investigated the processes by which collagen IV-modified scaffolds enhanced islet function and mediated early restoration of euglycemia post-transplantation. We characterized the effect of collagen IV-modified scaffolds on islet survival, metabolism, and insulin secretion in vitro and early- and intermediate-term islet mass and vascular density post-transplantation and correlated these with early restoration of euglycemia in a syngeneic mouse model. Control scaffolds maintained native islet morphologies and architectures as well as collagen IV-modified scaffolds in vivo. The islet size and vascular density increased, while β-cell proliferation decreased from day 16 to 113 post-transplantation. Collagen IV-modified scaffolds promoted islet cell viability and decreased early-stage apoptosis in islet cells in vitro-phenomena that coincided with enhanced islet metabolic function and glucose-stimulated insulin secretion. These findings suggest that collagen IV-modified scaffolds promote the early restoration of euglycemia post-transplantation by enhancing islet metabolism and glucose-stimulated insulin secretion. These studies of ECM proteins, in particular collagen IV, and islet function provide key insights for the engineering of a microenvironment that would serve as a platform for enhancing islet transplantation as a viable clinical therapy for T1DM.

Combined strategy of endothelial cells coating, Sertoli cells coculture and infusion improves vascularization and rejection protection of islet graft

Improving islet graft revascularization and inhibiting rejection become crucial tasks for prolonging islet graft survival. Endothelial cells (ECs) are the basis of islet vascularization and Sertoli cells (SCs) have the talent to provide nutritional support and exert immunosuppressive effects. We construct a combined strategy of ECs coating in the presence of nutritious and immune factors supplied by SCs in a co-culture system to investigate the effect of vascularization and rejection inhibition for islet graft. In vivo, the combined strategy improved the survival and vascularization as well as inhibited lymphocytes and inflammatory cytokines. In vitro, we found the combinatorial strategy improved the function of islets and the effect of ECs-coating on islets. Combined strategy treated islets revealed higher levels of anti-apoptotic signal molecules (Bcl-2 and HSP-32), survival and function related molecules (PDX-1, Ki-67, ERK1/2 and Akt) and demonstrated increased vascular endothelial growth factor receptor 2 (KDR) and angiogenesis signal molecules (FAk and PLC-γ). SCs effectively inhibited the activation of lymphocyte stimulated by islets and ECs. Predominantly immunosuppressive cytokines could be detected in culture supernatants of the SCs coculture group. These results suggest that ECs-coating and Sertoli cells co-culture or infusion synergistically enhance islet survival and function after transplantation.

Islet transplantation in type 1 diabetes: ongoing challenges, refined procedures, and long-term outcome

Remarkable progress has been made in islet transplantation over a span of 40 years. Once just an experimental curiosity in mice, this therapy has moved forward, and can now provide robust therapy for highly selected patients with type 1 diabetes (T1D), refractory to stabilization by other means. This progress could not have occurred without extensive dynamic international collaboration. Currently, 1,085 patients have undergone islet transplantation at 40 international sites since the Edmonton Protocol was reported in 2000 (752 allografts, 333 autografts), according to the Collaborative Islet Transplant Registry. The long-term results of islet transplantation in selected centers now match registry data of pancreas-alone transplantation, with 6 sites reporting five-year insulin independence rates ≥50%. Islet transplantation has been criticized for the use of multiple donor pancreas organs, but progress has also occurred in single-donor success, with 10 sites reporting increased single-donor engraftment. The next wave of innovative clinical trial interventions will address instant blood-mediated inflammatory reaction (IBMIR), apoptosis, and inflammation, and will translate into further marked improvements in single-donor success. Effective control of auto- and alloimmunity is the key to long-term islet function, and high-resolution cellular and antibody-based assays will add considerable precision to this process. Advances in immunosuppression, with new antibody-based targeting of costimulatory blockade and other T-B cellular signaling, will have further profound impact on the safety record of immunotherapy. Clinical trials will move forward shortly to test out new human stem cell derived islets, and in parallel trials will move forward, testing pig islets for compatibility in patients. Induction of immunological tolerance to self-islet antigens and to allografts is a difficult challenge, but potentially within our grasp.

Significant improvement in islet yield and survival with modified ET-Kyoto solution: ET-Kyoto/Neutrophil elastase inhibitor

Although islet transplantation can achieve insulin independence in patients with type 1 diabetes, sufficient number of islets derived from two or more donors is usually required to achieve normoglycemia. Activated neutrophils and neutrophil elastase (NE), which is released from these neutrophils, can directly cause injury in islet grafts. We hypothesized that inhibition of NE improves islet isolation and islet allograft survival. We tested our hypothesis by examining the effects of modified ET-Kyoto solution supplemented with sivelestat, a NE inhibitor (S-Kyoto solution), on islet yield and viability in islet isolation and the effect of intraperitoneally injected sivelestat on islet graft survival in a mouse allotransplant model. NE and proinflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-6 increased markedly at the end of warm digestion during islet isolation and exhibited direct cytotoxic activity against the islets causing their apoptosis. The use of S-Kyoto solution significantly improved islet yield and viability. Furthermore, treatment with sivelestat resulted in significant prolongation of islet allograft survival in recipient mice. Furthermore, serum levels of IL-6 and TNF-α at 1 and 2 weeks posttransplantation were significantly higher in islet recipients than before transplantation. Our results indicated that NE released from activated neutrophils negatively affects islet survival and that its suppression both in vitro and in vivo improved islet yield and prolonged islet graft survival. The results suggest that inhibition of NE activity could be potentially useful in islet transplantation for patients with type 1 diabetes mellitus.

Effects of astragalosides on cultured islets after cryopreservation in rats

OBJECTIVE

To explore the effects of AST (astragalosides) on cultured rat islet yield, purity, and function after cryopreservation in rats.

METHODS

Pancreatic islets were isolated from 30 Sprague-Dawley rats using the standard technique of collagenase P digestion and discontinuous Ficoll gradient purification. After thaw, the islets were randomly divided into AST group and control group (n=15). Next, the islet cells were cultured in AST-containing medium or standard medium for 7, 14, and 21 days after cryopreservation and thaw. The quantity, purity, and survival rate were calculated in the two groups before and after culture. Then the in vitro and in vivo function was observed in diabetic rats after islet transplantation.

RESULTS

The quantity and purity of islets had no difference between the two groups before culture (P>.05) while the difference after culture was significantly (P<.05). The survival rate of islets was 48% in AST group and 32% in the control group 21 days after thaw (P<.05). After 3 days, there was significantly a higher simulation index in the AST group than in the control group (P<.05). There was a significant difference in blood glucose and insulin concentrations between the groups after 3 days (P<.05).

CONCLUSION

AST can be added to the culture medium to reduce the loss of islet cryopreservation and be intravenously injected to improve culture islet function in vitro and prolong islet graft survival in diabetic rats.

Pig islet xenotransplantation acceptance in a Latin-American diabetic population

Progress in porcine islet xenotransplantation has been accompanied by studies on acceptance of this new procedure by patients, health professionals or the general public. Such studies have not been done in the Latin-American population. We conducted a questionnaire in 108 diabetes patients (insulin-dependent, n = 53; insulin-independent, n = 55) in a public hospital in Argentina. The questions addressed the general perception of the xenotransplant procedure and specific items related to the outcome (achieving insulin independence, improvement in metabolic control, delay in emergence of diabetic complications, need for repeat procedures, potential of transfer of infectious viruses, association with psychological problems, and anticipated success in relation to achieving a cure). Eighty-six (79%) of the patients accepted islet xenotransplantation; this incidence was not different for insulin-dependent or insulin-independent patients, patients with or without complications, or patients with good or poor metabolic control. Also, over 75% of patients accepted the procedure if this is only associated with a reduction in insulin requirement, if the procedure just delays but not prevents the onset of complications, or if the procedure needs to be performed every 6 months. Fifty-seven percent of patients indicated acceptance even if the potential transmission of a virus infection cannot be completely ruled out: this outcome was not affected by the outbreak of the H1N1 flu epidemic during the conduct of this study. Forty percent of patients indicated that living with porcine cells in their body could give psychological problems. We conclude that this population of Latin-American diabetic patients shows a high acceptance rate of a porcine islet xenotransplantation product.

Prediction of marginal mass required for successful islet transplantation

Islet quality assessment methods for predicting diabetes reversal (DR) following transplantation are needed. We investigated two islet parameters, oxygen consumption rate (OCR) and OCR per DNA content, to predict transplantation outcome and explored the impact of islet quality on marginal islet mass for DR. Outcomes in immunosuppressed diabetic mice were evaluated by transplanting mixtures of healthy and purposely damaged rat islets for systematic variation of OCR/DNA over a wide range. The probability of DR increased with increasing transplanted OCR and OCR/DNA. On coordinates of OCR versus OCR/DNA, data fell into regions in which DR occurred in all, some, or none of the animals with a sharp threshold of around 150-nmol/min mg DNA. A model incorporating both parameters predicted transplantation outcome with sensitivity and specificity of 93% and 94%, respectively. Marginal mass was not constant, depended on OCR/DNA, and increased from 2,800 to over 100,000 islet equivalents/kg body weight as OCR/DNA decreased. We conclude that measurements of OCR and OCR/DNA are useful for predicting transplantation outcome in this model system, and OCR/DNA can be used to estimate the marginal mass required for reversing diabetes. Because human clinical islet preparations in a previous study had OCR/DNA.

Immune cell populations in nonhuman primate islets

Islet transplantation is a promising cellular therapy for the treatment of type 1 diabetes (T1D). The immunogenicity of isolated islets has been of interest to the transplant community for many years, as upon transplantation, islets are damaged or destroyed through specific and nonspecific inflammatory and immune events. Antigen presenting cells (APC) are crucial intermediates in the generation of both innate and specific immune responses, and it has long been understood that some APC are resident in islets in situ, as well as after isolation. Our aim was to identify and characterize intraislet resident populations of APC and other immune cells in islets from nonhuman primates (Macaca fascicularis) in situ (pancreas biopsies obtained prerecovery) and after isolation using immunohistochemistry, confocal microscopy, and flow cytometry. The numbers of cells obtained in situ are similar to those in islets postisolation. Each isolated islet equivalent contains an average of 21.8 immune cells, 14.7 (67%) of which are APC. Many of these APC are dentritic cells and, surprisingly, 50% are B lymphocytes. The number of islet-resident immune cells increases with islet size, with greater numbers in large versus small islets (p < 0.001). The APC were localized around the exterior or spread evenly throughout the islets, with no definitive orientation identified. This knowledge will be useful to develop tailored modulation strategies to decrease immunogenicity, enhance engraftment, and ultimately prevent islet rejection.

Pig pancreatic islet transplantation into spontaneously diabetic dogs

INTRODUCTION

Pig islet xenotransplantation represents an attractive way to solve our human organ shortage. In this preclinical protocol, we implanted adult porcine islets microencapsulated in alginate-polylysin into insulin-dependent diabetic dogs.

METHODS

Pancreata were obtained from animals weighing 100 to 150 kg in a slaughterhouse. The islets were isolated by collagenase digestion. The encapsulation technique was a modification of Sun's method. Isolated islets (5000 islet equivalents per kilogram of dog weight) were mixed with 1.6% low-viscocity alginate. Microcapsules were cultured for 36 hours before implantation. The five dogs were in healthy prior to induction of diabetes mellitus at least 1 year prior. Under sedation, we implanted microcapsules. We performed determinations of peripheral blood insulin at baseline and every 3 months as well as glycosylated hemoglobin at baseline and every 4 months. During follow-up, glycemia was estimated twice a day at 3 hours after morning and night meals using a blood glucose monitoring system.

RESULTS

We observed significant decrease (20%-80%) in insulin needs (P < .01). Of note, before the procedure no hormone was detected in the blood at 6 to 12 months after transplantation, plasma insulin had improved significantly (P < .05) and glycosylated hemoglobin also showed a significant decrease (P < .01). All owners subjectively claimed that their animals were enjoying a better quality of life.

DISCUSSION

Our preliminary data suggested that pig islet microencapsulation achieved metabolic control in type I diabetic dogs without the risk of immunosuppression using one or two procedures per year.

[Pancreatic islets transplantation in the treatment of diabetes mellitus: present and future]

Diabetes treatment with insulin does no prevent the development of secondary complications. For this reason, treatments other than conventional ones are needed, which could bring about an <<almost physiological>> metabolic regulation. This can only be done by transplanting insulin producing tissue, such as vascularised pancreas transplantation, which is an already consolidated clinical procedure these days, or by islets transplantation, which is still a procedure in the clinical research phase. This has the same metabolic objectives as the vascularised transplant, but without the risks of major abdominal surgery, since the islets are implanted in the liver with minimal surgery or using interventionist radiology by means of a catheter. A clinical trial (Edmonton Protocol) was published in the year 2000, which improved the results after islet transplantation by obtaining normoglycaemia periods of more than one year in a consecutive patient series with type 1 diabetes and without using corticoids. This protocol has been endorsed in other centre in different trials. Although the initial results were good, the progress of these patients has shown that many islets transplantations do not manage to maintain insulin-independence indefinitely.

Long-term survival of nonhuman primate islets implanted in an omental pouch on a biodegradable scaffold

The aim of this study was to test whether an omental pouch can be used as an alternative site for islet implantation in diabetic monkeys. Here we report the successful engraftment of islets in diabetic cynomolgus monkeys when loaded on a synthetic biodegradable scaffold and placed in an omental pouch. One autologous and five allogeneic diabetic monkey transplants under the cover of steroid-free immune suppression (SFIS) were undertaken. Fasting blood glucose (FBG) and C-peptide (CP), exogenous insulin requirements (EIR), intravenous glucose tolerance test (IVGTT), A1C and histopathology were used to assess islet engraftment and survival. All animals achieved CP levels > 1.0 ng/mL following transplant, a 66-92% posttransplant decrease in EIR and reduced A1C. Following graft removal, CP became negative and histopathological analysis of the explanted grafts demonstrated well-granulated and well-vascularized, insulin-positive islets, surrounded by T-cell subsets and macrophages. Compared to intrahepatic allogeneic islet transplants (n = 20), there was a delayed engraftment for omental pouch recipients but similar levels of CP production were ultimately achieved, with a broad range of IEQ/kg transplanted in both sites. Our results suggest this extrahepatic transplantation site has potential as an alternative site for clinical islet cell transplantation.

Viral IL-10 gene transfer prolongs rat islet allograft survival

Islet transplantation is a potential cure for diabetes. However, allotransplant rejection severely limits its clinical application. In this study, we sought to transfect rat islets with an adenoviral vector containing the viral IL-10 (vIL-10) gene and examine its efficacy in preventing graft rejection. The immunosuppressive effect of vIL-10 is reported but its efficacy is somehow debatable in transplantation model. vIL-10 transfected islets were transplanted into streptozotocin-induced diabetic rats. Blood glucose, serum vIL-10 concentration, graft histology, and graft cytokine expression were used to monitor graft function up to day 21 after transplantation. Transfected islets released a large amount of vIL-10 protein without affecting their viability and functional integrity. When we transplanted the transfected islets into allogeneic hosts, the survival of grafted islets was not significantly increased. However, the combined use of vIL-10 and subtherapeutic doses of CsA (cyclosporine) significantly prolonged graft survival beyond that achieved with either agent alone (p < 0.001). vIL-10 and CsA-treated rats contain high level of vIL-10 in serum, which is evidenced by the inhibition of allogeneic mixed lymphocyte reaction (MLR). Histological analysis additionally revealed the presence of viable islets up to 21 days. IL-10 mRNA expression in grafted liver was higher and IFN-gamma mRNA was lower in vIL-10 and CsA-treated animals, compared with other groups. The synergistic effect of this combination therapy is potentially correlated with the induction of inhibitory cytokine secretion and downregulation of proinflammatory cytokine secretion from host cells.

Improvement of canine islet yield by donor pancreas infusion with a p38MAPK inhibitor

BACKGROUND

The activation of p38 mitogen-activated protein kinases (MAPK) is implicated in cold ischemia-reperfusion injury of donor organs. The islet isolation process, from pancreas procurement through islet collection, may activate p38MAPK leading to cytokine release and islet damage. This damage may be prevented by treating pancreata with a p38MAPK inhibitor (p38IH) before cold preservation.

METHODS

Pancreata removed from Beagle dogs were infused with University of Wisconsin solution containing the p38IH, SB203580, and Pefabloc (n=6) or vehicle (dimethyl sulfoxide and Pefabloc) alone (n=7), through the pancreatic duct and preserved using the two-layer method. After 20 to 22 hr, islets were isolated and 3000 IEQ/kg were autotransplanted into the corresponding dog to monitor glucose metabolism.

RESULTS

p38IH-treated pancreata yielded significantly more islets than control pancreata (IEQ/g: 2134+/-297 vs. 1477+/-145 IEQ/g or 65,012+/-9385 vs. 45,700+/-5103 IEQ/pancreas; P<0.05). Apoptotic beta-cell percentages assessed by laser scanning cytometry were lower in p38IH-treated than the controls (44%+/-9.4% vs. 61.6%+/-4.8%, P<0.05). Tumor necrosis factor-alpha expression assessed by real-time reverse transcription polymerase chain reaction was significantly lower in the p38IH-treated group than controls. All dogs (3000 IEQ/kg) transplanted with p38IH-treated islets (n=5) became euglycemic versus four of five dogs that received untreated islets. Plasma C-peptide levels after glucagon challenge were higher in animals receiving p38IH-treated islets (n=5) versus untreated islets (n=4) (0.40+/-0.78 vs. 0.21+/-0.05 ng/mL, P<0.05).

CONCLUSIONS

Infusion of pancreata with University of Wisconsin solution containing p38IH through the duct before preservation suppresses cytokine release, prevents beta-cell apoptosis, and improves islet yield significantly with no adverse effect on islet function after transplantation. p38IH treatment of human pancreata may improve islet yield for use in clinical transplantation.

Extracellular matrix protein-coated scaffolds promote the reversal of diabetes after extrahepatic islet transplantation

BACKGROUND

The survival and function of transplanted pancreatic islets is limited, owing in part to disruption of islet-matrix attachments during the isolation procedure. Using polymer scaffolds as a platform for islet transplantation, we investigated the hypothesis that replacement of key extracellular matrix components known to surround islets in vivo would improve graft function at an extrahepatic implantation site.

METHODS

Microporous polymer scaffolds fabricated from copolymers of lactide and glycolide were adsorbed with collagen IV, fibronectin, laminin-332 or serum proteins before seeding with 125 mouse islets. Islet-seeded scaffolds were then implanted onto the epididymal fat pad of syngeneic mice with streptozotocin-induced diabetes. Nonfasting glucose levels, weight gain, response to glucose challenges, and histology were used to assess graft function for 10 months after transplantation.

RESULTS

Mice transplanted with islets seeded onto scaffolds adsorbed with collagen IV achieved euglycemia fastest and their response to glucose challenge was similar to normal mice. Fibronectin and laminin similarly promoted euglycemia, yet required more time than collagen IV and less time than serum. Histopathological assessment of retrieved grafts demonstrated that coating scaffolds with specific extracellular matrix proteins increased total islet area in the sections and vessel density within the transplanted islets, relative to controls.

CONCLUSIONS

Extracellular matrix proteins adsorbed to microporous scaffolds can enhance the function of transplanted islets, with collagen IV maximizing graft function relative to the other proteins tested. These scaffolds enable the creation of well-defined microenvironments that promote graft efficacy at extrahepatic sites.

Islet transplantation in patients with autoimmune diabetes induces homeostatic cytokines that expand autoreactive memory T cells

Successful transplantation requires the prevention of allograft rejection and, in the case of transplantation to treat autoimmune disease, the suppression of autoimmune responses. The standard immunosuppressive treatment regimen given to patients with autoimmune type 1 diabetes who have received an islet transplant results in the loss of T cells. In many other situations, the immune system responds to T cell loss through cytokine-dependant homeostatic proliferation of any remaining T cells. Here we show that T cell loss after islet transplantation in patients with autoimmune type 1 diabetes was associated with both increased serum concentrations of IL-7 and IL-15 and in vivo proliferation of memory CD45RO(+) T cells, highly enriched in autoreactive glutamic acid decarboxylase 65-specific T cell clones. Immunosuppression with FK506 and rapamycin after transplantation resulted in a chronic homeostatic expansion of T cells, which acquired effector function after immunosuppression was removed. In contrast, the cytostatic drug mycophenolate mofetil efficiently blocked homeostatic T cell expansion. We propose that the increased production of cytokines that induce homeostatic expansion could contribute to recurrent autoimmunity in transplanted patients with autoimmune disease and that therapy that prevents the expansion of autoreactive T cells will improve the outcome of islet transplantation.

The ATP/DNA ratio is a better indicator of islet cell viability than the ADP/ATP ratio

Real-time, accurate assessment of islet viability is critical for avoiding transplantation of nontherapeutic preparations. Measurements of the intracellular ADP/ATP ratio have been recently proposed as useful prospective estimates of islet cell viability and potency. However, dead cells may be rapidly depleted of both ATP and ADP, which would render the ratio incapable of accounting for dead cells. Since the DNA of dead cells is expected to remain stable over prolonged periods of time (days), we hypothesized that use of the ATP/DNA ratio would take into account dead cells and may be a better indicator of islet cell viability than the ADP/ATP ratio. We tested this hypothesis using mixtures of healthy and lethally heat-treated (HT) rat insulinoma cells and human islets. Measurements of ATP/DNA and ADP/ATP from the known mixtures of healthy and HT cells and islets were used to evaluate how well these parameters correlated with viability. The results indicated that ATP and ADP were rapidly (within 1 hour) depleted in HT cells. The fraction of HT cells in a mixture correlated linearly with the ATP/DNA ratio, whereas the ADP/ADP ratio was highly scattered, remaining effectively unchanged. Despite similar limitations in both ADP/ADP and ATP/DNA ratios, in that ATP levels may fluctuate significantly and reversibly with metabolic stress, the results indicated that ATP/DNA was a better measure of islet viability than the ADP/ATP ratio.

Transplantation for the treatment of type 1 diabetes

Transplantation of pancreatic tissue, as either the intact whole pancreas or isolated pancreatic islets has become a clinical option to be considered in the treatment of patients with type 1 insulin-dependant diabetes mellitus. A successful whole pancreas or islet transplant offers the advantages of attaining normal or near normal blood glucose control and normal hemoglobin A1c levels without the risks of severe hypoglycemia associate with intensive insulin therapy. Both forms of transplants are also effective at eliminating the occurrence of significant hypoglycemic events (even with only partial islet function evident). Whereas whole pancreas transplantation has also been shown to be very effective at maintaining a euglycemic state over a sustained period of time, thus providing an opportunity for a recipient to benefit from improvement of their blood glucose control, it is associated with a significant risk of surgical and post-operative complications. Islet transplantation is attractive as a less invasive alternative to whole pancreas transplant and offers the future promise of immunosuppression-free transplantation through pre-transplant culture. Islet transplantation however, may not always achieve the sustained level of tight glucose control necessary for reducing the risk of secondary diabetic complications and exposes the patient to the adverse effects of immunosuppression. Although recent advances have led to an increased rate of obtaining insulin-independence following islet transplantation, further developments are needed to improve the long-term viability and function of the graft to maintain improved glucose control over time.

Pancreatic islet cell transplantation: update and new developments

Pancreatic islet cell transplantation is a treatment alternative for patients with type 1 diabetes who experience hypoglycemic unawareness despite maximal care. The good results obtained by the group from Edmonton and other centers, with 80% insulin independence at 1 year posttransplant, are not sustainable over time, with 5-year insulin independence achieved in only 10% of patients. However, persistent graft function, even without insulin independence, results in improved glucose control and avoidance of hypoglycemic events. Changes in organ preservation, islet processing technique, and immunosuppression regimens can result in improvement of results in the future. Islet autotransplantation is an option for patients who undergo total pancreatectomy for chronic pancreatitis with debilitating pain, in which reinfusion of the islets from the resected pancreas can result in avoidance of postsurgical diabetes or enhanced glucose control.

A stirred microchamber for oxygen consumption rate measurements with pancreatic islets

Improvements in pancreatic islet transplantation for treatment of diabetes are hindered by the absence of meaningful islet quality assessment methods. Oxygen consumption rate (OCR) has previously been used to assess the quality of organs and primary tissue for transplantation. In this study, we describe and characterize a stirred microchamber for measuring OCR with small quantities of islets. The device has a titanium body with a chamber volume of about 200 microL and is magnetically stirred and water jacketed for temperature control. Oxygen partial pressure (pO(2)) is measured by fluorescence quenching with a fiber optic probe, and OCR is determined from the linear decrease of pO(2) with time. We demonstrate that measurements can be made rapidly and with high precision. Measurements with betaTC3 cells and islets show that OCR is directly proportional to the number of viable cells in mixtures of live and dead cells and correlate linearly with membrane integrity measurements made with cells that have been cultured for 24 h under various stressful conditions.

Transplantation for the treatment of type 1 diabetes

Transplantation of pancreatic tissue, as either the intact whole pancreas or isolated pancreatic islets has become a clinical option to be considered in the treatment of patients with type 1 insulin-dependant diabetes mellitus. A successful whole pancreas or islet transplant offers the advantages of attaining normal or near normal blood glucose control and normal hemoglobin A1c levels without the risks of severe hypoglycemia associate with intensive insulin therapy. Both forms of transplants are also effective at eliminating the occurrence of significant hypoglycemic events (even with only partial islet function evident). Whereas whole pancreas transplantation has also been shown to be very effective at maintaining a euglycemic state over a sustained period of time, thus providing an opportunity for a recipient to benefit from improvement of their blood glucose control, it is associated with a significant risk of surgical and post-operative complications. Islet transplantation is attractive as a less invasive alternative to whole pancreas transplant and offers the future promise of immunosuppression-free transplantation through pre-transplant culture. Islet transplantation however, may not always achieve the sustained level of tight glucose control necessary for reducing the risk of secondary diabetic complications and exposes the patient to the adverse effects of immunosuppression. Although recent advances have led to an increased rate of obtaining insulin-independence following islet transplantation, further developments are needed to improve the long-term viability and function of the graft to maintain improved glucose control over time.

Improvement of human islet cryopreservation by a p38 MAPK inhibitor

The activation of p38 mitogen-activated protein kinase (MAPK) has been shown to cause ischemia/reperfusion injury of several organs used for transplantation and also to play a significant role in primary islet graft nonfunction. Activation of p38 MAPK may also occur during islet cryopreservation and thawing. In this study, a p38 MAPK inhibitor (p38IH) was applied to human islet cryopreservation to improve islet yield and quality after thawing. Under serum-free conditions, human islets were cryopreserved, thawed and cultured using our standard procedures. Three types of solutions were tested: conventional RPMI1640 medium (RPMI), a newly developed islet cryopreservation solution (ICS), and ICS supplemented with a p38IH, SD-282 (ICS-p38IH). Activation or inhibition of p38 MAPK was demonstrated by the diminished phosphorylation of HSP27 substrate. Islet recovery on day 2 after thawing was highest with ICS-p38IH and islet viability was not significantly different in the three groups. beta Cell numbers and function were the highest in islets cryopreserved with ICS-p38IH. Glucose-stimulated human C-peptide levels were 86% of that of the nonfrozen islets when measured 4 weeks after transplantation into NODscid mice. This improvement may provide an opportunity to establish islet banks and allow the use of cryopreserved islets for clinical transplantation.

The effect of whole organ pancreas transplantation and PIT on diabetic complications

Diabetes mellitus is a leading cause of morbidity and mortality in the Western world. Currently, the only forms of beta-cell replacement are whole organ pancreas transplantation and pancreatic islet transplantation. Whole organ transplantation has demonstrated benefits in prevention and reversal of diabetic complications with sustainable long-term outcomes. Pancreatic islet transplantation continues to be a field that needs further study to ascertain the true benefit of islet transplantation for diabetic complications. This can only be achieved with improvement in long-term islet allograft survival.

Improved islet yields from pancreas preserved in perflurocarbon is via inhibition of apoptosis mediated by mitochondrial pathway

Islet transplantation is a treatment option for type I diabetic patients. Preservation of human pancreata prior to islet isolation using two-layer method with perfluorocarbon (PFC) and University of Wisconsin solution (UW) results in twofold increase in islet yields. The objective of this study was to determine the mechanism by which islets undergo apoptosis and determine PFC's effects on this process. Gene array analysis was used to analyze the expression of pro- and anti-apoptotic genes in islets isolated from pancreata preserved under varying conditions. A 12-fold increase in the expression of inhibitor of apoptosis (IAP) and survivin was observed in islets isolated from pancreata preserved in PFC. This was accompanied by decreased expression of BAD (3.7-fold), BAX (2.7-fold) and caspases (5.2-fold). Levels of activated caspase-9 (77.98%), caspase-2 (61.5%), caspase-3 (68.3%) and caspase-8 (37.2%) were also reduced. 'Rescue' of pancreata after storage (12 h) in UW by preservation using PFC also resulted in a down-regulation of pro-apoptotic genes and inhibition of caspase activation. Apoptosis observed in islets from all groups was mainly mitochondria-dependent, mediated by change in redox potential initiated by hypoxia. We demonstrate that reduction in hypoxia of pancreata preserved using PFC leads to significant up-regulation of anti-apoptotic and inhibition of pro-apoptotic genes.

Pancreatic islet transplantation for treating diabetes

Pancreatic islet transplantation is one of the options for treating diabetes and has been shown to improve the quality of life of severe diabetic patients. Since the Edmonton protocol was announced, islet transplantation have advanced considerably, including islet after kidney transplantation, utilisation of non-heart-beating donors, single-donor islet transplantation and living-donor islet transplantation. These advances were based on revised immunosuppression protocols, improved pancreas procurement and islet isolation methods, and enhanced islet engraftment. Further improvements are necessary to make islet transplantation a routine clinical treatment. To synergise efforts towards a cure for type 1 diabetes, a Diabetes Research Institute (DRI) Federation is currently being established to include leading diabetes research centres worldwide, including DRIs in Miami, Edmonton and Kyoto among others.