Beta-cell death and mass in syngeneically transplanted islets exposed to short- and long-term hyperglycemia

Prolonged Survival of Subcutaneous Allogeneic Islet Graft by Donor Chimerism without Immunosuppressive Treatment

The aim of this study was to investigate whether tolerance-induced protection of islets in the renal subcapsular space can also prevent subcutaneous allogeneic islets from being rejected. We used bone marrow stem cells from C57BL/6 (H2^b) mice to construct donor chimerism in conditioned diabetic BALB/c (H2^d) mice and investigated the effect of donor chimerism on engraftment and survival of subcutaneously transplanted allogeneic islets in streptozotocin-induced diabetic mice. We also studied the anti-inflammatory effect of mesenchymal stem cell on islet engraftment. Full but not low-grade or no donor chimerism was associated with successful engraftment of allogeneic islets and restoration of normoglycemia in the treated diabetic mice. The temporary hyperglycemia was 11 ± 1 versus 19 ± 5 days (p < 0.05) for the mice with full donor chimerism with transplanted islets in the renal subcapsular space versus the subcutaneous space, respectively. Cotransplantation of mesenchymal stem cell did not enhance alloislet engraftment. Full multilineage donor chimerism was associated with a higher transient expansion of CD11b⁺ and Gr-1⁺ myeloid progenitor cells and effector memory CD4 and CD8 T cells. In conclusion, full donor chimerism protected both renal subcapsular and subcutaneous allogeneic islets in this rodent transplantation model.

Immunomodulation of cell-penetrating tat-metallothionein for successful outcome of xenotransplanted pancreatic islet

Pancreatic islet transplantation is a promising treatment for treatment of type 1 diabetes; however, transplantation outcomes have been disappointing due to early graft loss that is mediated by many immune responses. Immune cells not only directly damaged islet but also produced reactive oxygen species (ROS), which is highly toxic to islet cells. Metallothionein (MT) can provide protection against oxidative stress by scavenging various ranges of ROS including superoxide, hydroxyl radical, hydrogen peroxide and nitric oxide. For scavenging immune response-induced ROS, cell-penetrating Tat peptide-metallothionein (Tat-MT) was delivered into islets. The viability of Tat-MT-treated islets was not damaged during co-culture with macrophages or ROS-generating paraquat. When Tat-MT-treated islets were xenotransplanted, ROS production was significantly attenuated at the islets. Eventually, the survival time of Tat-MT-treated islets was significantly enhanced without any immunosuppressant medicine. Additionally, we confirmed that the survival time of Tat-MT-treated islets in all animals was dramatically improved when accompanied with low dose immunosuppressive agents (tacrolimus and anti-CD154 monoclonal antibody), indicating that Tat-MT delivery could have synergistic effect with immunosuppressants. Collectively, this new combination therapy of Tat-MT delivery with low dose immunosuppressant would be a powerful remedy for successful outcome of islet xenotransplantation.

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.

Insight into microenvironment remodeling in pancreatic endocrine tissue engineering: Biological and biomaterial approaches

The treatment of diabetes mellitus, as a chronic and complicated disease, is a valuable purpose. Islet transplantation can provide metabolic stability and insulin independence in type 1 diabetes patients. Diet and insulin therapy are only diabetes controllers and cannot remove all of the diabetes complications. Moreover, islet transplantation is more promising treatment than whole pancreas transplantation because of lesser invasive surgical procedure and morbidity and mortality. According to the importance of extracellular matrix for islet viability and function, microenvironment remodeling of pancreatic endocrine tissue can lead to more success in diabetes treatment by pancreatic islets. Production of bioengineered pancreas and remodeling of pancreas extracellular matrix provide essential microenvironment for re-vascularization, re-innervation and signaling cascades triggering. Therefore, islets show better viability and function in these conditions. Researchers conduct various scaffolds with different biomaterials for the improvement of islet viability, function and transplantation outcome. The attention to normal pancreas anatomy, embryology and histology is critical to understand the pancreatic Langerhans islets niche and finally to achieve efficient engineered structure. Therefore, in the present study, the status and components of the islets niche is mentioned and fundamental issues related to the tissue engineering of this structure is considered. The purpose of this review article is summarization of recent progress in the endocrine pancreas tissue engineering and biomaterials and biological aspects of it.

Tweaking Mesenchymal Stem/Progenitor Cell Immunomodulatory Properties with Viral Vectors Delivering Cytokines

Mesenchymal Stem Cells (MSCs) can be found in various body sites. Their main role is to differentiate into cartilage, bone, muscle, and fat cells to allow tissue maintenance and repair. During inflammation, MSCs exhibit important immunomodulatory properties that are not constitutive, but require activation, upon which they may exert immunosuppressive functions. MSCs are defined as "sensors of inflammation" since they modulate their ability of interfering with the immune system both in vitro and in vivo upon interaction with different factors. MSCs may influence immune responses through different mechanisms, such as direct cell-to-cell contact, release of soluble factors, and through the induction of anergy and apoptosis. Human MSCs are defined as plastic-adherent cells expressing specific surface molecules. Lack of MHC class II antigens makes them appealing as allogeneic tools for the therapy of both autoimmune diseases and cancer. MSC therapeutic potential could be highly enhanced by the expression of exogenous cytokines provided by transduction with viral vectors. In this review, we attempt to summarize the results of a great number of in vitro and in vivo studies aimed at improving the ability of MSCs as immunomodulators in the therapy of autoimmune, degenerative diseases and cancer. We will also compare results obtained with different vectors to deliver heterologous genes to these cells.

Comparison of the Ovary and Kidney as Sites for Islet Transplantation in Diabetic Rats

BACKGROUND

Currently, the most commonly used site for clinical islet transplantation is the liver although it is far from being an ideal site. Low oxygen tension and the induction of an inflammatory response impair islet implantation and lead to significant early loss of islet. The present study aimed to investigate and compare the efficacy of islet transplantation to the ovary and kidney subcapsule in diabetic rats.

METHODS

The study was performed with 3 groups of rats (control, ovary, and kidney subcapsule) including 6 Sprague female rats each. Diabetes model was created with the use of streptozotocin, and blood glucose levels of the rats were measured after 72 hours. Thirty days after the transplantation, blood samples were obtained from the rats, and then pancreas, kidney, and ovary specimens were fixed in 10% formaldehyde and the experiment completed. After staining with hematoxylin and eosin, the tissue samples were morphologically evaluated by a specialist histopathologist.

RESULTS

Changes in mean blood glucose and C-peptide levels were statistically significant in the ovary and kidney subcapsule groups. Histologic examination revealed that granulosus insulin-bearing cells were detected in the islet grafts of both ovary and kidney subcapsule groups. The renal subcapsule group had inflammation signs on histologic examination. The islet cells of both ovary and renal subcapsule groups had no vacuolization.

CONCLUSIONS

We showed that the ovary might be a new site for islet transplantation. Further research should be done on whether the initial results of this study can be reproduced in larger numbers of animal models and eventually in humans.

Mesenchymal stem cell and derived exosome as small RNA carrier and Immunomodulator to improve islet transplantation

Human bone marrow mesenchymal stem cells (hBMSCs) and their exosomes can suppress immune reaction and deliver small RNAs. Thus, they may improve islet transplantation by delivering small RNAs for promoting islet function and inhibiting immune rejection. Here, we proposed an hBMSC and its exosome-based therapy to overcome immune rejection and poor islet function, both of which hinder the success of islet transplantation. We found overexpressed siFas and anti-miR-375 in plasmid encoding shFas and anti-miR-375 transfected hBMSC-derived exosomes, which silenced Fas and miR-375 of human islets and improved their viability and function against inflammatory cytokines. This plasmid transfected hBMSCs downregulated Fas and miR-375 of human islets in a humanized NOD scid gamma (NSG) mouse model, whose immune reaction was inhibited by injecting hBMSC and peripheral blood mononuclear cell (PBMC) co-cultured exosomes. These exosomes suppressed immune reaction by inhibiting PBMC proliferation and enhancing regulatory T cell (Treg) function. Collectively, our studies elucidated the mechanisms of RNA delivery from hBMSCs to human islets and the immunosuppressive effect of hBMSC and peripheral blood mononuclear cell co-cultured exosomes for improving islet transplantation.

Characterizing the Mechanistic Pathways of the Instant Blood-Mediated Inflammatory Reaction in Xenogeneic Neonatal Islet Cell Transplantation

Supplemental digital content is available in the text.

Introduction

The instant blood-mediated inflammatory reaction (IBMIR) causes major loss of islets after transplantation and consequently represents the initial barrier to survival of porcine neonatal islet cell clusters (NICC) after xenotransplantation.

Methods

This study used novel assays designed to characterize the various immunologic components responsible for xenogeneic IBMIR to identify initiators and investigate processes of IBMIR-associated coagulation, complement activation and neutrophil infiltration. The IBMIR was induced in vitro by exposing NICC to platelet-poor or platelet-rich human plasma or isolated neutrophils.

Results

We found that xenogeneic IBMIR was characterized by rapid, platelet-independent thrombin generation, with addition of platelets both accelerating and exacerbating this response. Platelet-independent complement activation was observed as early as 30 minutes after NICC exposure to plasma. However, membrane attack complex formation was not observed in NICC histopathology sections until after 60 minutes. We demonstrated for the first time that NICC-mediated complement activation was necessary for neutrophil activation in the xenogeneic IBMIR setting. Finally, using the Seahorse extracellular flux analyzer, we identified substantial loss of islet function (up to 40%) after IBMIR with surviving NICC showing evidence of mitochondrial damage.

Conclusions

This study used novel assays to describe multiple key pathways by which xenogeneic IBMIR causes islet destruction, allowing further refinement of future interventions aimed at resolving the issue of IBMIR in xenotransplantation.

Silicon nanopore membrane (SNM) for islet encapsulation and immunoisolation under convective transport

Problems associated with islet transplantation for Type 1 Diabetes (T1D) such as shortage of donor cells, use of immunosuppressive drugs remain as major challenges. Immune isolation using encapsulation may circumvent the use of immunosuppressants and prolong the longevity of transplanted islets. The encapsulating membrane must block the passage of host’s immune components while providing sufficient exchange of glucose, insulin and other small molecules. We report the development and characterization of a new generation of semipermeable ultrafiltration membrane, the silicon nanopore membrane (SNM), designed with approximately 7 nm-wide slit-pores to provide middle molecule selectivity by limiting passage of pro-inflammatory cytokines. Moreover, the use of convective transport with a pressure differential across the SNM overcomes the mass transfer limitations associated with diffusion through nanometer-scale pores. The SNM exhibited a hydraulic permeability of 130 ml/hr/m²/mmHg, which is more than 3 fold greater than existing polymer membranes. Analysis of sieving coefficients revealed 80% reduction in cytokines passage through SNM under convective transport. SNM protected encapsulated islets from infiltrating cytokines and retained islet viability over 6 hours and remained responsive to changes in glucose levels unlike non-encapsulated controls. Together, these data demonstrate the novel membrane exhibiting unprecedented hydraulic permeability and immune-protection for islet transplantation therapy.

Accessory cells for β-cell transplantation

Despite recent advances, insulin therapy remains a treatment, not a cure, for diabetes mellitus with persistent risk of glycaemic alterations and life-threatening complications. Restoration of the endogenous β-cell mass through regeneration or transplantation offers an attractive alternative. Unfortunately, signals that drive β-cell regeneration remain enigmatic and β-cell replacement therapy still faces major hurdles that prevent its widespread application. Co-transplantation of accessory non-islet cells with islet cells has been shown to improve the outcome of experimental islet transplantation. This review will highlight current travails in β-cell therapy and focuses on the potential benefits of accessory cells for islet transplantation in diabetes.

Successful Application of Closed-Loop Artificial Pancreas Therapy After Islet Autotransplantation

Total pancreatectomy with islet autotransplantation (TPIAT) may relieve the pain of chronic pancreatitis while avoiding postsurgical diabetes. Minimizing hyperglycemia after TPIAT limits beta cell apoptosis during islet engraftment. Closed-loop (CL) therapy combining an insulin pump with a continuous glucose monitor (CGM) has not been investigated previously in islet transplant recipients. Our objective was to determine the feasibility and efficacy of CL therapy to maintain glucose profiles close to normoglycemia following TPIAT. Fourteen adult subjects (36% male; aged 35.9 ± 11.4 years) were randomized to subcutaneous insulin via CL pump (n = 7) or multiple daily injections with blinded CGM (n = 7) for 72 h at transition from intravenous to subcutaneous insulin. Mean serum glucose values were significantly lower in the CL pump group than in the control group (111 ± 4 vs. 130 ± 13 mg/dL; p = 0.003) without increased risk of hypoglycemia (percentage of time <70 mg/dL: CL pump 1.9%, control 4.8%; p = 0.46). Results from this pilot study suggest that CL therapy is superior to conventional therapy in maintaining euglycemia without increased hypoglycemia. This technology shows significant promise to safely maintain euglycemic targets during the period of islet engraftment following islet transplantation.

Progress and challenges in macroencapsulation approaches for type 1 diabetes (T1D) treatment: Cells, biomaterials, and devices

Macroencapsulation technology has been an attractive topic in the field of treatment for Type 1 diabetes due to mechanical stability, versatility, and retrievability of the macro-capsule design. Macro-capsules can be categorized into extravascular and intravascular devices, in which solute transport relies either on diffusion or convection, respectively. Failure of macroencapsulation strategies can be due to limited regenerative capacity of the encased insulin-producing cells, sub-optimal performance of encapsulation biomaterials, insufficient immunoisolation, excessive blood thrombosis for vascular perfusion devices, and inadequate modes of mass transfer to support cell viability and function. However, significant technical advancements have been achieved in macroencapsulation technology, namely reducing diffusion distance for oxygen and nutrients, using pro-angiogenic factors to increase vascularization for islet engraftment, and optimizing membrane permeability and selectivity to prevent immune attacks from host's body. This review presents an overview of existing macroencapsulation devices and discusses the advances based on tissue-engineering approaches that will stimulate future research and development of macroencapsulation technology. Biotechnol. Bioeng. 2016;113: 1381-1402. © 2015 Wiley Periodicals, Inc.

Efficient Gene Transduction of Dispersed Islet Cells in Culture Using Fiber-Modified Adenoviral Vectors

To establish novel islet-based therapies, our group has recently developed technologies for creating functional neo-islet tissues in the subcutaneous space by transplanting monolithic sheets of dispersed islet cells (islet cell sheets). Improving cellular function and viability are the next important challenges for enhancing the therapeutic effects. This article describes the adenoviral vector-mediated gene transduction of dispersed islet cells under culture conditions. Purified pancreatic islets were obtained from Lewis rats and dissociated into single islet cells. Cells were plated onto laminin-5-coated temperature-responsive polymer poly(N-isopropylacrylamide)-immobilized plastic dishes. At 0 h, islet cells were infected for 1 h with either conventional type 5 adenoviral vector (Ad-CA-GFP) or fiber-modified adenoviral vector (AdK7-CA-GFP) harboring a polylysine (K7) peptide in the C terminus of the fiber knob. We investigated gene transduction efficiency at 48 h after infection and found that AdK7-CA-GFP yielded higher transduction efficiencies than Ad-CA-GFP at a multiplicity of infection (MOI) of 5 and 10. For AdK7-CA-GFP at MOI = 10, 84.4 ± 1.5% of islet cells were found to be genetically transduced without marked vector infection-related cellular damage as determined by viable cell number and lactate dehydrogenase (LDH) release assay. After AdK7-CA-GFP infection at MOI = 10, cells remained attached and expanded to nearly full confluency, showing that this adenoviral infection protocol is a feasible approach for creating islet cell sheets. We have shown that dispersed and cultured islet cells can be genetically modified efficiently using fiber-modified adenoviral vectors. Therefore, this gene therapy technique could be used for cellular modification or biological assessment of dispersed islet cells.

Connexin-Based Therapeutics and Tissue Engineering Approaches to the Amelioration of Chronic Pancreatitis and Type I Diabetes: Construction and Characterization of a Novel Prevascularized Bioartificial Pancreas

Total pancreatectomy and islet autotransplantation is a cutting-edge technique to treat chronic pancreatitis and postoperative diabetes. A major obstacle has been low islet cell survival due largely to the innate inflammatory response. Connexin43 (Cx43) channels play a key role in early inflammation and have proven to be viable therapeutic targets. Even if cell death due to early inflammation is avoided, insufficient vascularization is a primary obstacle to maintaining the viability of implanted cells. We have invented technologies targeting the inflammatory response and poor vascularization: a Cx43 mimetic peptide that inhibits inflammation and a novel prevascularized tissue engineered construct. We combined these technologies with isolated islets to create a prevascularized bioartificial pancreas that is resistant to the innate inflammatory response. Immunoconfocal microscopy showed that constructs containing islets express insulin and possess a vascular network similar to constructs without islets. Glucose stimulated islet-containing constructs displayed reduced insulin secretion compared to islets alone. However, labeling for insulin post-glucose stimulation revealed that the constructs expressed abundant levels of insulin. This discrepancy was found to be due to the expression of insulin degrading enzyme. These results suggest that the prevascularized bioartificial pancreas is potentially a tool for improving long-term islet cell survival in vivo.

Heterozygous inactivation of plasma membrane Ca(2+)-ATPase in mice increases glucose-induced insulin release and beta cell proliferation, mass and viability

AIMS/HYPOTHESIS

Calcium plays an important role in the process of glucose-induced insulin release in pancreatic beta cells. These cells are equipped with a double system responsible for Ca(2+) extrusion--the Na/Ca exchanger (NCX) and the plasma membrane Ca(2+)-ATPase (PMCA). We have shown that heterozygous inactivation of NCX1 in mice increased glucose-induced insulin release and stimulated beta cell proliferation and mass. In the present study, we examined the effects of heterozygous inactivation of the PMCA on beta cell function.

METHODS

Biological and morphological methods (Ca(2+) imaging, Ca(2+) uptake, glucose metabolism, insulin release and immunohistochemistry) were used to assess beta cell function and proliferation in Pmca2 (also known as Atp2b2) heterozygous mice and control littermates ex vivo. Blood glucose and insulin levels were also measured to assess glucose metabolism in vivo.

RESULTS

Pmca (isoform 2) heterozygous inactivation increased intracellular Ca(2+) stores and glucose-induced insulin release. Moreover, increased beta cell proliferation, mass, viability and islet size were observed in Pmca2 heterozygous mice. However, no differences in beta cell glucose metabolism, proinsulin immunostaining and insulin content were observed.

CONCLUSIONS/INTERPRETATION

The present data indicates that inhibition of Ca(2+) extrusion from the beta cell and its subsequent intracellular accumulation stimulates beta cell function, proliferation and mass. This is in agreement with our previous results observed in mice displaying heterozygous inactivation of NCX, and indicates that inhibition of Ca(2+) extrusion mechanisms by small molecules in beta cells may represent a new approach in the treatment of type 1 and type 2 diabetes.

Advances in Local Drug Release and Scaffolding Design to Enhance Cell Therapy for Diabetes

Islet transplant is a curative treatment for insulin-dependent diabetes. However, challenges, including poor tissue survival and a lack of efficient engraftment, must be overcome. An encapsulating or scaffolding material can act as a vehicle for agents carefully chosen for the islet transplant application. From open porous scaffolds to spherical capsules and conformal coatings, greater immune protection is often accompanied by greater distances to microvasculature. Generating a local oxygen supply from the implant material or encouraging vessel growth through the release of local factors can create an oxygenated engraftment site. Intricately related to the vascularization response, inflammatory interaction with the cell supporting implant is a long-standing hurdle to material-based islet transplant. Modulation of the immune responses to the islets as well as the material itself must be considered. To match the post-transplant complexity, the release rate can be tuned to orchestrate temporal responses. Material degradation properties can be utilized in passive approaches or external stimuli and biological cues in active approaches. A combination of multiple carefully chosen factors delivered in an agent-specialized manner is considered by this review to improve the long-term function of islets transplanted in scaffolding and encapsulating materials.

Islet heparan sulfate but not heparan sulfate proteoglycan core protein is lost during islet isolation and undergoes recovery post-islet transplantation

Islet beta cells in situ express intracellular heparan sulfate (HS), a property previously shown in vitro to be important for their survival. We report that HS levels inside islet beta cells correlate with the novel intracellular localization of the HSPG core proteins for collagen type XVIII (Col18), a conventional extracellular matrix component. Syndecan-1 (Sdc1) and CD44 core proteins were similarly localized inside beta cells. During isolation, mouse islets selectively lose HS to 11-27% of normal levels but retain their HSPG core proteins. Intra-islet HS failed to recover substantially during culture for 4 days and was not reconstituted in vitro using HS mimetics. In contrast, significant recovery of intra-islet HS to ∼40-50% of normal levels occurred by 5-10 days after isotransplantation. Loss of islet HS during the isolation procedure is independent of heparanase (a HS-degrading endoglycosidase) and due, in part, to oxidative damage. Treatment with antioxidants reduced islet cell death by ∼60% and increased the HS content of isolated islets by ∼twofold compared to untreated islets, preserving intra-islet HS to ∼60% of the normal HS content of islets in situ. These findings suggest that the preservation of islet HS during the islet isolation process may optimize islet survival posttransplant.

Pediatric Autologous Islet Transplantation

A total pancreatectomy and islet autotransplant (TPIAT) offers substantial pain relief and improved quality of life for children who are severely affected by chronic or recurrent acute pancreatitis and for whom the usual medical and endoscopic therapies have failed. The pancreas is entirely resected, and the pancreatic islets are isolated from the pancreas and infused back into the patient's liver. Because this is an autologous transplant, no immunosuppression is required. Over several months, the islets engraft in the liver; the patient is then slowly weaned off insulin therapy. Slightly more than 40 % of patients become and remain insulin independent, yet even among patients who remain on insulin, most have some islet function, permitting easier diabetes control. The majority of patients experience pain relief, with significant improvements in health-related quality of life. A TPIAT should be considered for children who are significantly disabled by chronic pancreatitis.

Improved coating of pancreatic islets with regulatory T cells to create local immunosuppression by using the biotin-polyethylene glycol-succinimidyl valeric acid ester molecule

BACKGROUND

We showed that T regulatory (Treg) cells can be attached to the surface of pancreatic islets providing local immunoprotection. Further optimization of the method can improve coating efficiency, which may prolong graft survival. In this study, we compared the effectiveness of two different molecules used for binding of the Tregs to the surface of pancreatic islets. Our aim was to increase the number of Treg cells attached to islets without compromising islets viability and function.

METHODS

The cell surface of human Treg cells and pancreatic islets was modified using biotin-polyethylene glycol-N-hydroxylsuccinimide (biotin-PEG-NHS) or biotin-PEG-succinimidyl valeric acid ester (biotin-PEG-SVA). Then, islets were incubated with streptavidin as islet/Treg cells binding molecule. Treg cells were stained with CellTracker CM-DiL dye and visualized using a Laser Scanning Confocal Microscope. The number of Treg cells attached per islets surface area was analyzed by Imaris software. The effect of coating on islet functionality was determined using the glucose-stimulated insulin response (GSIR) assay.

RESULTS

The coating procedure with biotin-PEG-SVA allowed for attaching 40% more Treg cells per 1 μm(2) of islet surface. Although viability was comparable, function of the islets after coating using the biotin-PEG-SVA molecule was better preserved than with NHS molecule. GSIR was 62% higher for islets coated with biotin-PEG-SVA compared to biotin-PEG-NHS.

CONCLUSION

Coating of islets with Treg cells using biotin-PEG-SVA improves effectiveness with better preservation of the islet function. Improvement of the method of coating pancreatic islets with Treg cells could further facilitate the effectiveness of this novel immunoprotective approach and translation into clinical settings.

Extensive Loss of Islet Mass Beyond the First Day After Intraportal Human Islet Transplantation in a Mouse Model

Clinical islet transplantation is characterized by a progressive deterioration of islet graft function, which renders many patients once again dependent on exogenous insulin administration within a couple of years. In this study, we aimed to investigate possible engraftment factors limiting the survival and viability of experimentally transplanted human islets beyond the first day after their transplantation to the liver. Human islets were transplanted into the liver of nude mice and characterized 1 or 30 days after transplantation by immunohistochemistry. The factors assessed were endocrine mass, cellular death, hypoxia, vascular density and amyloid formation in the transplanted islets. One day posttransplantation, necrotic cells, as well as apoptotic cells, were commonly observed. In contrast to necrotic death, apoptosis rates remained high 1 month posttransplantation, and the total islet mass was reduced by more than 50% between 1 and 30 days posttransplantation. Islet mass at 30 days posttransplantation correlated negatively to apoptotic death. Vascular density within the transplanted islets remained less than 30% of that in native human islets up to 30 days posttransplantation and was associated with prevailing hypoxia. Amyloid formation was rarely observed in the 1-day-old transplants, but was commonly observed in the 30-day-old islet transplants. We conclude that substantial islet cell death occurs beyond the immediate posttransplantation phase, particularly through apoptotic events. Concomitant low vascularization with prevailing hypoxia and progressive amyloid development was observed in the human islet grafts. Strategies to improve engraftment at the intraportal site or change of implantation site in the clinical setting are needed.

Respective effects of oxygen and energy substrate deprivation on beta cell viability

Deficit in oxygen and energetic substrates delivery is a key factor in islet loss during islet transplantation. Permeability transition pore (PTP) is a mitochondrial channel involved in cell death. We have studied the respective effects of oxygen and energy substrate deprivation on beta cell viability as well as the involvement of oxidative stress and PTP opening. Energy substrate deprivation for 1h followed by incubation in normal conditions led to a cyclosporin A (CsA)-sensitive-PTP-opening in INS-1 cells and human islets. Such a procedure dramatically decreased INS-1 cells viability except when transient removal of energy substrates was performed in anoxia, in the presence of antioxidant N-acetylcysteine (NAC) or when CsA or metformin inhibited PTP opening. Superoxide production increased during removal of energy substrates and increased again when normal energy substrates were restored. NAC, anoxia or metformin prevented the two phases of oxidative stress while CsA prevented the second one only. Hypoxia or anoxia alone did not induce oxidative stress, PTP opening or cell death. In conclusion, energy substrate deprivation leads to an oxidative stress followed by PTP opening, triggering beta cell death. Pharmacological prevention of PTP opening during islet transplantation may be a suitable option to improve islet survival and graft success.

Total pancreatectomy with islet autotransplantation: summary of an NIDDK workshop

A workshop sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases focused on research gaps and opportunities in total pancreatectomy with islet autotransplantation (TPIAT) for the management of chronic pancreatitis. The session was held on July 23, 2014 and structured into 5 sessions: (1) patient selection, indications, and timing; (2) technical aspects of TPIAT; (3) improving success of islet autotransplantation; (4) improving outcomes after total pancreatectomy; and (5) registry considerations for TPIAT. The current state of knowledge was reviewed; knowledge gaps and research needs were specifically highlighted. Common themes included the need to identify which patients best benefit from and when to intervene with TPIAT, current limitations of the surgical procedure, diabetes remission and the potential for improvement, opportunities to better address pain remission, GI complications in this population, and unique features of children with chronic pancreatitis considered for TPIAT. The need for a multicenter patient registry that specifically addresses the complexities of chronic pancreatitis and total pancreatectomy outcomes and postsurgical diabetes outcomes was repeatedly emphasized.

Inducible VEGF expression by human embryonic stem cell-derived mesenchymal stromal cells reduces the minimal islet mass required to reverse diabetes

Islet transplantation has been hampered by loss of function due to poor revascularization. We hypothesize that co-transplantation of islets with human embryonic stem cell-derived mesenchymal stromal cells that conditionally overexpress VEGF (hESC-MSC:VEGF) may augment islet revascularization and reduce the minimal islet mass required to reverse diabetes in mice. HESC-MSCs were transduced by recombinant lentiviruses that allowed conditional (Dox-regulated) overexpression of VEGF.

HESC-MSC

VEGF were characterized by tube formation assay. After co-transplantation of hESC-MSC:VEGF with murine islets in collagen-fibrin hydrogel in the omental pouch of diabetic nude mice, we measured blood glucose, body weight, glucose tolerance and serum C-peptide. As control, islets were transplanted alone or with non-transduced hESC-MSCs. Next, we compared functional parameters of 400 islets alone versus 200 islets co-transplanted with hESC-MSC:VEGF. As control, 200 islets were transplanted alone. Metabolic function of islets transplanted with hESC-MSC:VEGF significantly improved, accompanied by superior graft revascularization, compared with control groups. Transplantation of 200 islets with hESC-MSC:VEGF showed superior function over 400 islets alone. We conclude that co-transplantation of islets with VEGF-expressing hESC-MSCs allowed for at least a 50% reduction in minimal islet mass required to reverse diabetes in mice. This approach may contribute to alleviate the need for multiple donor organs per patient.

Treating diet-induced diabetes and obesity with human embryonic stem cell-derived pancreatic progenitor cells and antidiabetic drugs

Human embryonic stem cell (hESC)-derived pancreatic progenitor cells effectively reverse hyperglycemia in rodent models of type 1 diabetes, but their capacity to treat type 2 diabetes has not been reported. An immunodeficient model of type 2 diabetes was generated by high-fat diet (HFD) feeding in SCID-beige mice. Exposure to HFDs did not impact the maturation of macroencapsulated pancreatic progenitor cells into glucose-responsive insulin-secreting cells following transplantation, and the cell therapy improved glucose tolerance in HFD-fed transplant recipients after 24 weeks. However, since diet-induced hyperglycemia and obesity were not fully ameliorated by transplantation alone, a second cohort of HFD-fed mice was treated with pancreatic progenitor cells combined with one of three antidiabetic drugs. All combination therapies rapidly improved body weight and co-treatment with either sitagliptin or metformin improved hyperglycemia after only 12 weeks. Therefore, a stem cell-based therapy may be effective for treating type 2 diabetes, particularly in combination with antidiabetic drugs.

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High-fat diets (HFDs) caused rapid metabolic dysfunction in immunodeficient mice

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HFDs and/or antidiabetic drugs did not affect function of hESC-derived beta cells

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hESC-derived beta cells improved glucose tolerance in HFD-fed mice

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Cell therapy combined with an antidiabetic drug was the most effective treatment

1,25(OH)2D3 prolongs islet graft survival by inflammatory inhibition

OBJECTIVE

This study aimed to determine the protective effect of 1,25-dihydroxyvitamin D3 (1,25(OH)2D3) against islet graft loss.

METHODS

Proliferation of tumor necrosis factor (TNF)-α-induced macrophages was determined in vitro after treatment with different concentrations of 1,25-(OH)2D3. Intraportal islet transplantation (IPIT) was performed with islets harvested from the Sprague-Dawley rats and transplanted to the diabetic rats. The transplanted rats were assigned to receive 1,25-(OH)2D3 or propylene glycol (control). Islet graft survival; inflammatory cytokine (TNF-α and interleukin [IL]-1); numbers and percentages of macrophages, CD4(+), and CD8(+) T cells in bloods; and expression of nuclear factor (NF)-κB and TNF-α were analyzed. Hematoxylin and eosin staining was performed.

RESULTS

We found 100 mg/mL 1,25-(OH)2D3 per day to have the strongest inhibitory effect on macrophages. Survival time of islet grafts significantly increased in the rats receiving 1,25-(OH)2D3. There were fewer infiltrated inflammatory cells in both islet graft and adjacent tissue in the drug-treated rats with lower serum IL-1 and TNF-α. Furthermore, percentage of macrophages and expression of p-NF-κB p65 and TNF-α in graft sites were significantly lower in the treated rats.

CONCLUSION

Our results demonstrated that 1,25(OH)2D3 prolongs islet graft survival by decreasing nonspecific inflammation in syngeneic IPIT through inhibiting TNF-α/NF-κB pathway and macrophage infiltration.

Transplantation of heterospheroids of islet cells and mesenchymal stem cells for effective angiogenesis and antiapoptosis

Although islet transplantation has been suggested as an alternative therapy for type 1 diabetes, there are efficiency concerns that are attributed to poor engraftment of transplanted islets. Hypoxic condition and delayed vasculogenesis induce necrosis and apoptosis of the transplanted islets. To overcome these limitations in islet transplantation, heterospheroids (HSs), which consist of rat islet cells (ICs) and human bone marrow-derived mesenchymal stem cells (hMSCs), were transplanted to the kidney and liver. The HSs cultured under the hypoxic condition system exhibited a significant increase in antiapoptotic gene expression in ICs. hMSCs in the HSs secreted angiogenic and antiapoptotic proteins. With the HS system, ICs and hMSCs were successfully located in the same area of the liver after transplantation of HSs through the portal vein, whereas the transplantation of islets and the dissociated hMSCs did not result in localization of transplanted ICs and hMSCs in the same area. HS transplantation resulted in an increase in angiogenesis at the transplantation area and a decrease in the apoptosis of transplanted ICs after transplantation into the kidney subcapsule compared with transplantation of islet cell clusters (ICCs). Insulin production levels of ICs were higher in the HS transplantation group compared with the ICC transplantation group. The HS system may be a more efficient transplantation method than the conventional methods for the treatment of type 1 diabetes.

Phospho-BAD BH3 mimicry protects β cells and restores functional β cell mass in diabetes

Strategies that simultaneously enhance the survival and glucose responsiveness of insulin-producing β cells will greatly augment β cell replacement therapies in type 1 diabetes (T1D). We show that genetic and pharmacologic mimetics of the phosphorylated BCL-2 homology 3 (BH3) domain of BAD impart β-cell-autonomous protective effects in the face of stress stimuli relevant to β cell demise in T1D. Importantly, these benefits translate into improved engraftment of donor islets in transplanted diabetic mice, increased β cell viability in islet grafts, restoration of insulin release, and diabetes reversal. Survival of β cells in this setting is not merely due to the inability of phospho-BAD to suppress prosurvival BCL-2 proteins but requires its activation of the glucose-metabolizing enzyme glucokinase. Thus, BAD phospho-BH3 mimetics may prove useful in the restoration of functional β cell mass in diabetes.

Engineering biomimetic materials for islet transplantation

A closed-loop system that provides both the sensing of glucose and the appropriate dosage of insulin could dramatically improve treatment options for insulin-dependent diabetics. The intrahepatic implantation of allogeneic islets has the potential to provide this intimate control, by transplanting the very cells that have this inherent sensing and secretion capacity. Limiting islet transplantation, however, is the significant loss and dysfunction of islets following implantation, due to the poor engraftment environment and significant immunological attack. In this review, we outline approaches that seek to address these challenges via engineering biomimetic materials. These materials can serve to mimic natural processes that work toward improving engraftment, minimizing inflammation, and directing immunological responses. Biomimetic materials can serve to house cells, recapitulate native microenvironments, release therapeutic agents in a physiological manner, and/or present agents to direct cells towards desired responses. By integrating these approaches, superior platforms capable of improving long-term engraftment and acceptance of transplanted islets are on the horizon.

Vascular heterogeneity between native rat pancreatic islets is responsible for differences in survival and revascularisation post transplantation

AIMS/HYPOTHESIS

Highly blood-perfused islets have been observed to be the most functional islets in the native pancreas. We hypothesised that differences in vascular support of islets in donor pancreases influence their susceptibility to cellular stress and capacity for vascular engraftment after transplantation.

METHODS

Highly blood-perfused islets in rats were identified by injection of microspheres into the ascending aorta before islet isolation. Cell death was evaluated after in vitro cytokine or hypoxia exposure, and 2 days post transplantation. One month post transplantation, islet engraftment, including vascular density, blood perfusion and oxygen tension (pO2) in the tissue, was evaluated.

RESULTS

Microsphere-containing islets had a similar frequency of cell death during standard culture conditions but increased cell death after exposure to cytokines and hypoxia in comparison with other islets. Two days after transplantation the percentage of apoptotic or necrotic cells was also higher in grafts of such islets and 1 month post transplantation these grafts were composed of substantially more connective tissue. Grafts of highly blood-perfused islets in the native pancreas regained a higher vascular density, blood perfusion and pO2 in comparison with grafts of other islets.

CONCLUSIONS/INTERPRETATION

Native islets that are highly blood-perfused regained this feature after transplantation, indicating a superior capacity for revascularisation and post-transplant function. However, the same group of islets was more vulnerable to different kinds of cellular stress, which limited their early survival post transplantation. Preferential death of these most active islets may contribute to the high number of islets needed to provide cure with islet transplantation.

Lixisenatide accelerates restoration of normoglycemia and improves human beta-cell function and survival in diabetic immunodeficient NOD-scid IL-2rg(null) RIP-DTR mice engrafted with human islets

OBJECTIVE

Glucagon-like peptide-1 induces glucose-dependent insulin secretion and, in rodents, increases proliferation and survival of pancreatic beta cells. To investigate the effects on human beta cells, we used immunodeficient mice transplanted with human islets. The goal was to determine whether lixisenatide, a glucagon-like peptide-1 receptor agonist, improves human islet function and survival in vivo.

METHODS

Five independent transplant studies were conducted with human islets from five individual donors. Diabetic human islet-engrafted immunodeficient mice were treated with lixisenatide (50, 150, and 500 µg/kg) or vehicle. Islet function was determined by blood glucose, plasma human insulin/C-peptide, and glucose tolerance tests. Grafts were analyzed for total beta- and alpha-cell number, percent proliferation, and levels of apoptosis.

RESULTS

Diabetic mice transplanted with marginal human islet mass and treated with lixisenatide were restored to euglycemia more rapidly than vehicle-treated mice. Glucose tolerance tests, human plasma insulin, and glucose-stimulation indices of lixisenatide-treated mice were significantly improved compared to vehicle-treated mice. The percentages of proliferating or apoptotic beta cells at graft recovery were not different between lixisenatide-treated and vehicle-treated mice. Nevertheless, in one experiment we found a significant twofold to threefold increase in human beta-cell numbers in lixisenatide-treated compared to vehicle-treated mice.

CONCLUSION

Diabetic human islet-engrafted immunodeficient mice treated with lixisenatide show improved restoration of normoglycemia, human plasma insulin, and glucose tolerance compared to vehicle-treated mice engrafted with the same donor islets. Because the proliferative capacity of human beta cells is limited, improved beta-cell survival coupled with enhanced beta-cell function following lixisenatide treatment may provide the greatest benefit for diabetic patients with reduced functional islet mass.

Total pancreatectomy with islet autotransplantation: summary of a National Institute of Diabetes and Digestive and Kidney diseases workshop

A workshop sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases focused on research gaps and opportunities in total pancreatectomy with islet autotransplantation (TPIAT) for the management of chronic pancreatitis (CP). The session was held on July 23, 2014, and structured into 5 sessions: (1) patient selection, indications, and timing; (2) technical aspects of TPIAT; (3) improving success of islet autotransplantation; (4) improving outcomes after total pancreatectomy; and (5) registry considerations for TPIAT. The current state of knowledge was reviewed; knowledge gaps and research needs were specifically highlighted. Common themes included the need to identify which patients best benefit from and when to intervene with TPIAT, current limitations of the surgical procedure, diabetes remission and the potential for improvement, opportunities to better address pain remission, gastrointestinal complications in this population, and unique features of children with CP considered for TPIAT. The need for a multicenter patient registry that specifically addresses the complexities of CP and total pancreatectomy outcomes as well as postsurgical diabetes outcomes was repeatedly emphasized.

Total pancreatectomy with islet autotransplantation: summary of a National Institute of Diabetes and Digestive and Kidney diseases workshop

A workshop sponsored by the National Institute of Diabetes and Digestive and Kidney Diseases focused on research gaps and opportunities in total pancreatectomy with islet autotransplantation (TPIAT) for the management of chronic pancreatitis (CP). The session was held on July 23, 2014, and structured into 5 sessions: (1) patient selection, indications, and timing; (2) technical aspects of TPIAT; (3) improving success of islet autotransplantation; (4) improving outcomes after total pancreatectomy; and (5) registry considerations for TPIAT. The current state of knowledge was reviewed; knowledge gaps and research needs were specifically highlighted. Common themes included the need to identify which patients best benefit from and when to intervene with TPIAT, current limitations of the surgical procedure, diabetes remission and the potential for improvement, opportunities to better address pain remission, gastrointestinal complications in this population, and unique features of children with CP considered for TPIAT. The need for a multicenter patient registry that specifically addresses the complexities of CP and total pancreatectomy outcomes as well as postsurgical diabetes outcomes was repeatedly emphasized.

Near-euglycemia can be achieved safely in pediatric total pancreatectomy islet autotransplant recipients using an adapted intravenous insulin infusion protocol

BACKGROUND

Children with severe chronic pancreatitis may undergo total pancreatectomy with islet autotransplantation (TPIAT) to relieve pain while minimizing the risk of postsurgical diabetes. Because overstimulation of transplanted islets by hyperglycemia can result in β-cell loss, we developed a specialized intravenous insulin infusion protocol (IIP) for pediatric TPIAT recipients to maintain euglycemia or near-euglycemia posttransplant.

SUBJECTS AND METHODS

Our objective was to review glucose control using an IIP specific for TPIAT recipients at a single institution. We reviewed postoperative blood glucose (BG) levels for 32 children 4-18 years old with chronic pancreatitis who underwent TPIAT between July 2011 and June 2013. We analyzed the proportion of BG values in the range of 70-140 mg/dL, mean glucose, glucose variability, and occurrence of hypoglycemia during the IIP; we also evaluated the transition to subcutaneous therapy (first 72 h with multiple daily injections [MDI]).

RESULTS

During IIP, the mean patient BG level was 116±27 mg/dL, with 83.1% of all values in the range of 70-140 mg/dL. Hypoglycemia was rare, with only 2.5% of values <70 mg/dL. The more recent era (n=16) had a lower mean BG and less variability than the early era (first 16 patients) (P≤0.004). Mean glucose level (116 vs. 128 mg/dL) and glucose variability were significantly lower during the IIP compared with MDI therapy (P<0.0001).

CONCLUSIONS

Tight glycemic control without excessive severe hypoglycemia was achieved in children undergoing TPIAT using an IIP specifically designed for this population; the ability to maintain BG in target range improved with experience with the protocol.

Pro-inflammatory and pro-oxidant status of pancreatic islet in vitro is controlled by TLR-4 and HO-1 pathways

Since their isolation until implantation, pancreatic islets suffer a major stress leading to the activation of inflammatory reactions. The maintenance of controlled inflammation is essential to preserve survival and function of the graft. Identification and targeting of pathway(s) implicated in post-transplant detrimental inflammatory events, is mandatory to improve islet transplantation success. We sought to characterize the expression of the pro-inflammatory and pro-oxidant mediators during islet culture with a focus on Heme oxygenase (HO-1) and Toll-like receptors-4 signaling pathways. Rat pancreatic islets were isolated and pro-inflammatory and pro-oxidant status were evaluated after 0, 12, 24 and 48 hours of culture through TLR-4, HO-1 and cyclooxygenase-2 (COX-2) expression, CCL-2 and IL-6 secretion, ROS (Reactive Oxygen Species) production (Dihydroethidine staining, DHE) and macrophages migration. To identify the therapeutic target, TLR4 inhibition (CLI-095) and HO-1 activation (cobalt protoporphyrin,CoPP) was performed. Activation of NFκB signaling pathway was also investigated. After isolation and during culture, pancreatic islet exhibited a proinflammatory and prooxidant status (increase levels of TLR-4, COX-2, CCL-2, IL-6, and ROS). Activation of HO-1 or inhibition of TLR-4 decreased inflammatory status and oxidative stress of islets. Moreover, the overexpression of HO-1 induced NFκB phosphorylation while the inhibition of TLR-4 had no effect NFκB activation. Finally, inhibition of pro-inflammatory pathway induced a reduction of macrophages migration. These data demonstrated that the TLR-4 signaling pathway is implicated in early inflammatory events leading to a pro-inflammatory and pro-oxidant status of islets in vitro. Moreover, these results provide the mechanism whereby the benefits of HO-1 target in TLR-4 signaling pathway. HO-1 could be then an interesting target to protect islets before transplantation.

Total pancreatectomy and islet autotransplantation in children for chronic pancreatitis: indication, surgical techniques, postoperative management, and long-term outcomes

OBJECTIVE

Describe the surgical technique, complications, and long-term outcomes of total pancreatectomy and islet autotransplantation (TP-IAT) in a large series of pediatric patients.

BACKGROUND

Surgical management of childhood pancreatitis is not clear; partial resection or drainage procedures often provide transient pain relief, but long-term recurrence is common due to the diffuse involvement of the pancreas. Total pancreatectomy (TP) removes the source of the pain, whereas islet autotransplantation (IAT) potentially can prevent or minimize TP-related diabetes.

METHODS

Retrospective review of 75 children undergoing TP-IAT for chronic pancreatitis who had failed medical, endoscopic, or surgical treatment between 1989 and 2012.

RESULTS

Pancreatitis pain and the severity of pain statistically improved in 90% of patients after TP-IAT (P < 0.001). The relief from narcotics was sustained. Of the 75 patients undergoing TP-IAT, 31 (41.3%) achieved insulin independence. Younger age (P = 0.032), lack of prior Puestow procedure (P = 0.018), lower body surface area (P = 0.048), higher islet equivalents (IEQ) per kilogram body weight (P = 0.001), and total IEQ (100,000) (P = 0.004) were associated with insulin independence. By multivariate analysis, 3 factors were associated with insulin independence after TP-IAT: (1) male sex, (2) lower body surface area, and (3) higher total IEQ per kilogram body weight. Total IEQ (100,000) was the single factor most strongly associated with insulin independence (odds ratio = 2.62; P < 0.001).

CONCLUSIONS

Total pancreatectomy and islet autotransplantation provides sustained pain relief and improved quality of life. The β-cell function is dependent on islet yield. Total pancreatectomy and islet autotransplantation is an effective therapy for children with painful pancreatitis that failed medical and/or endoscopic management.

A Preconditioning Regimen with a PKCε Activator Improves Islet Graft Function in a Mouse Transplant Model

Transplantation of islets isolated from deceased donor pancreata is an attractive method of β-cell replacement therapy for patients with type 1 diabetes (T1D). However, the loss of islet cell viability and function during the peritransplant period is a limiting factor to long-term islet engraftment. Activation of the isoenzyme PKCe may improve islet survival and function. The current study assesses the effects of PKCe activation on islet graft function in a syngeneic streptozotocin-induced diabetic mouse model. Islets were isolated from wild-type BALB/c mice preconditioned with either a PKCe activator (ψεRACK) or a TAT carrier control peptide. Islets were further treated with the same agents during isolation, purification, and incubation prior to transplantation. Two hundred seventy-five islet equivalents were transplanted under the kidney capsule of streptozotocin-induced diabetic BALB/c mice. Islet function was assessed by measurement of blood glucose levels every 3 days for 42 days after transplant and through an intraperitoneal glucose tolerance test (IPGTT). The time for return to euglycemia in mice transplanted with islets treated with ψεRACK was improved at 14 ± 6 days versus 21 ± 6 days with TAT-treated islets. The IPGTT showed a 50% reduction in the area under the curve associated with an improved insulin response in mice transplanted with ψεRACK-treated islets compared to TAT-treated islets. A preconditioning regimen using PKCe agonist before pancreatic recovery and during islet isolation improves islet graft function and resistance to high glucose stress after transplantation.

Endogenous ω-3 polyunsaturated fatty acid production confers resistance to obesity, dyslipidemia, and diabetes in mice

Despite the well-documented health benefits of ω-3 polyunsaturated fatty acids (PUFAs), their use in clinical management of hyperglycemia and obesity has shown little success. To better define the mechanisms of ω-3 PUFAs in regulating energy balance and insulin sensitivity, we deployed a transgenic mouse model capable of endogenously producing ω-3 PUFAs while reducing ω-6 PUFAs owing to the expression of a Caenorhabditis elegans fat-1 gene encoding an ω-3 fatty acid desaturase. When challenged with high-fat diets, fat-1 mice strongly resisted obesity, diabetes, hypercholesterolemia, and hepatic steatosis. Endogenous elevation of ω-3 PUFAs and reduction of ω-6 PUFAs did not alter the amount of food intake but led to increased energy expenditure in the fat-1 mice. The requirements for the levels of ω-3 PUFAs as well as the ω-6/ω-3 ratios in controlling blood glucose and obesity are much more stringent than those in lipid metabolism. These metabolic phenotypes were accompanied by attenuation of the inflammatory state because tissue levels of prostaglandin E2, leukotriene B4, monocyte chemoattractant protein-1, and TNF-α were significantly decreased. TNF-α-induced nuclear factor-κB signaling was almost completely abolished. Consistent with the reduction in chronic inflammation and a significant increase in peroxisome proliferator-activated receptor-γ activity in the fat-1 liver tissue, hepatic insulin signaling was sharply elevated. The activities of prolipogenic regulators, such as liver X receptor, stearoyl-CoA desaturase-1, and sterol regulatory element binding protein-1 were sharply decreased, whereas the activity of peroxisome proliferator-activated receptor-α, a nuclear receptor that facilitates lipid β-oxidation, was markedly increased. Thus, endogenous conversion of ω-6 to ω-3 PUFAs via fat-1 strongly protects against obesity, diabetes, inflammation, and dyslipidemia and may represent a novel therapeutic modality to treat these prevalent disorders.

Beneficial effect of insulin treatment on islet transplantation outcomes in Akita mice

Islet transplantation is a promising potential therapy for patients with type 1 diabetes. The outcome of islet transplantation depends on the transplantation of a sufficient amount of β-cell mass. However, the initial loss of islets after transplantation is problematic. We hypothesized the hyperglycemic status of the recipient may negatively affect graft survival. Therefore, in the present study, we evaluated the effect of insulin treatment on islet transplantation involving a suboptimal amount of islets in Akita mice, which is a diabetes model mouse with an Insulin 2 gene missense mutation. Fifty islets were transplanted under the left kidney capsule of the recipient mouse with or without insulin treatment. For insulin treatment, sustained-release insulin implants were implanted subcutaneously into recipient mice 2 weeks before transplantation and maintained for 4 weeks. Islet transplantation without insulin treatment did not reverse hyperglycemia. In contrast, the group that received transplants in combination with insulin treatment exhibited improved fasting blood glucose levels until 18 weeks after transplantation, even after insulin treatment was discontinued. The group that underwent islet transplantation in combination with insulin treatment had better glucose tolerance than the group that did not undergo insulin treatment. Insulin treatment improved graft survival from the acute phase (i.e., 1 day after transplantation) to the chronic phase (i.e., 18 weeks after transplantation). Islet apoptosis increased with increasing glucose concentration in the medium or blood in both the in vitro culture and in vivo transplantation experiments. Expression profile analysis of grafts indicated that genes related to immune response, chemotaxis, and inflammatory response were specifically upregulated when islets were transplanted into mice with hyperglycemia compared to those with normoglycemia. Thus, the results demonstrate that insulin treatment protects islets from the initial rapid loss that is usually observed after transplantation and positively affects the outcome of islet transplantation in Akita mice.

A novel resting strategy for improving islet engraftment in the liver

BACKGROUND

Several studies have revealed that posttransplant insulin treatment is beneficial to rest the islet grafts. However, insulin infusion per se is not enough to completely suppress the heavy workload arising caused by postprandial hyperglycemia. Therefore, the present study examined whether short-term fasting combined with insulin treatment could effectively prevent graft exhaustion after intraportal islet transplantation.

METHODS

A marginal dose of syngeneic rat islet grafts were transplanted intraportally into the control, insulin-treated, and insulin+rest groups of streptozotocin-induced diabetic rats. The control group fed freely without insulin treatment, and the other groups were continuously treated with an optimal amount of insulin to maintain normoglycemia. In addition, the insulin+rest group fasted and received total parenteral nutrition during the 2 weeks after transplantation.

RESULTS

The curative rate was significantly higher in both the insulin and insulin+rest groups than the control group (P<0.0001). The glucose tolerance, residual graft mass, and graft function were significantly ameliorated in the insulin+rest group, but not in the insulin group, compared to the control group (P<0.01, P=0.03, P=0.001).

CONCLUSIONS

These data suggest that short-term fasting combined with insulin treatment, especially during the avascular period of the grafts, could therefore be a promising regimen for improving pancreatic islet engraftment in the liver.

Islet cell transplantation

Islet transplantation has become a promising treatment for selected patients with type 1 diabetes. Here we provide an overview of the procedure including its history, the process of donor selection, and the techniques and procedures involved in a successful transplant. A brief overview of the current immunosuppressive regimens, the long-term follow-up and the reported outcomes will also be discussed. While islet transplantation is currently generally reserved for adults with type 1 diabetes with severe hypoglycemia or glycemic lability, we herein consider the possibility of its application to the pediatric population.

Preculturing Islets With Adipose-Derived Mesenchymal Stromal Cells Is an Effective Strategy for Improving Transplantation Efficiency at the Clinically Preferred Intraportal Site

We have recently shown that preculturing islets with kidney-derived mesenchymal stromal cells (MSCs) improves transplantation outcome in streptozotocin-diabetic mice implanted with a minimal mass of islets beneath the kidney capsule. In the present study, we have extended our previous observations to investigate whether preculturing islets with MSCs can also be used to enhance islet function at the clinically used intraportal site. We have used MSCs derived from adipose tissue, which are more readily accessible than alternative sources in human subjects and can be expanded to clinically efficacious numbers, to preculture islets throughout this study. The in vivo efficacy of grafts consisting of islets precultured alone or with MSCs was tested using a syngeneic streptozotocin-diabetic minimal islet mass model at the clinically relevant intraportal site. Blood glucose concentrations were monitored for 1 month. The vascularization of islets precultured alone or with MSCs was investigated both in vitro and in vivo, using immunohistochemistry. Islet insulin content was measured by radioimmunoassay. The effect of preculturing islets with MSCs on islet function in vitro was investigated using static incubation assays. There was no beneficial angiogenic influence of MSC preculture, as demonstrated by the comparable vascularization of islets precultured alone or with MSCs, both in vitro after 3 days and in vivo 1 month after islet transplantation. However, the in vitro insulin secretory capacity of MSC precultured islets was superior to that of islets precultured alone. In vivo, this was associated with improved glycemia at 7, 14, 21, and 28 days posttransplantation, in recipients of MSC precultured islets compared to islets precultured alone. The area of individual islets within the graft-bearing liver was significantly higher in recipients of MSC precultured islets compared to islets precultured alone. Our experimental studies suggest that preculturing islets with MSCs represents a favorable strategy for improving the efficiency of clinical islet transplantation.

Deterioration of glycemic control after corticosteroid administration in islet autotransplant recipients: a cautionary tale

Islet autotransplantation (IAT) is performed at the time of total pancreatectomy (TP) to prevent or minimize post-surgical diabetes. Corticosteroids induce insulin resistance and present a risk to islet autografts, through glucotoxicity and increased metabolic demand on a marginal islet mass. We present four IAT recipients treated with oral or injected corticosteroids after transplant for medical conditions unrelated to chronic pancreatitis or TPIAT. Hyperglycemia or insulin resistance was evident in all four patients, including reversion to long-term insulin therapy in two patients. One patient receiving corticosteroid injections had a transient increase in hemoglobin A1c (+0.6% above baseline), and one patient given a one time dose of oral dexamethasone exhibited hyperglycemia despite high insulin (>200 mU/L) and C-peptide (15.3 ng/mL) production on an oral glucose tolerance test. IAT recipients have insufficient islet mass to compensate for the insulin resistance induced by corticosteroids. Caution should be given to using these agents in IAT recipients. When corticosteroids are medically necessary, insulin therapy should be administered temporarily to compensate for the increased metabolic demand and minimize long-term risks on the islet graft.

Long-term outcomes of total pancreatectomy and islet auto transplantation for hereditary/genetic pancreatitis

BACKGROUND

Chronic pancreatitis is a debilitating disease resulting from many causes. The subset with hereditary/genetic pancreatitis (HGP) not only has chronic pain, but also an increased risk for pancreatic cancer. Long-term outcomes of total pancreatectomy (TP) and islet autogeneic transplantation (IAT) for chronic pancreatitis due to HGP are not clear.

STUDY DESIGN

We reviewed a prospectively maintained database of 484 TP-IATs from 1977 to 2012 at a single center. The outcomes (eg, pain relief, narcotic use, β-cell function, health-related quality of life measures) of patients who received TP-IAT for HGP (protease trypsin 1, n = 38; serine protease inhibitor Kazal type 1, n = 9; cystic fibrosis transmembrane conductance regulator, n = 14; and familial, n = 19) were evaluated and compared with those with non-hereditary/nongenetic causes.

RESULTS

All 80 patients with HGP were narcotic dependent and failed endoscopic management or direct pancreatic surgery. Post TP-IAT, 90% of the patients were pancreatitis pain free with sustained pain relief; >65% had partial or full β-cell function. Compared with nonhereditary causes, HGP patients were younger (22 years old vs 38 years old; p ≤ 0.001), had pancreatitis pain of longer duration (11.6 ± 1.1 years vs 9.0 ± 0.4 years; p = 0.016), had a higher pancreas fibrosis score (7 ± 0.2 vs 4.8 ± 0.1; p ≤ 0.001), and trended toward lower islet yield (3,435 ± 361 islet cell equivalent vs 3,850 ± 128 islet cell equivalent; p = 0.28). Using multivariate logistic regression, patients with non-HGP causes (p = 0.019); lower severity of pancreas fibrosis (p < 0.001); shorter duration of years with pancreatitis (p = 0.008); and higher transplant islet cell equivalent per kilogram body weight (p ≤ 0.001) were more likely to achieve insulin independence (p < 0.001). There was a significant improvement in health-related quality of life from baseline by RAND 36-Item Short Form Health Survey and in physical and mental component health-related quality of life scores (p < 0.001). None of the patients in the entire cohort had cancer of pancreatic origin in the liver or elsewhere develop during 2,936 person-years of follow-up.

CONCLUSIONS

Total pancreatectomy and IAT in patients with chronic pancreatitis due to HGP cause provide long-term pain relief (90%) and preservation of β-cell function. Patients with chronic painful pancreatitis due to HGP with a high lifetime risk of pancreatic cancer should be considered earlier for TP-IAT before pancreatic inflammation results in a higher degree of pancreatic fibrosis and islet cell function loss.

Long-term outcomes of total pancreatectomy and islet auto transplantation for hereditary/genetic pancreatitis

BACKGROUND

Chronic pancreatitis is a debilitating disease resulting from many causes. The subset with hereditary/genetic pancreatitis (HGP) not only has chronic pain, but also an increased risk for pancreatic cancer. Long-term outcomes of total pancreatectomy (TP) and islet autogeneic transplantation (IAT) for chronic pancreatitis due to HGP are not clear.

STUDY DESIGN

We reviewed a prospectively maintained database of 484 TP-IATs from 1977 to 2012 at a single center. The outcomes (eg, pain relief, narcotic use, β-cell function, health-related quality of life measures) of patients who received TP-IAT for HGP (protease trypsin 1, n = 38; serine protease inhibitor Kazal type 1, n = 9; cystic fibrosis transmembrane conductance regulator, n = 14; and familial, n = 19) were evaluated and compared with those with non-hereditary/nongenetic causes.

RESULTS

All 80 patients with HGP were narcotic dependent and failed endoscopic management or direct pancreatic surgery. Post TP-IAT, 90% of the patients were pancreatitis pain free with sustained pain relief; >65% had partial or full β-cell function. Compared with nonhereditary causes, HGP patients were younger (22 years old vs 38 years old; p ≤ 0.001), had pancreatitis pain of longer duration (11.6 ± 1.1 years vs 9.0 ± 0.4 years; p = 0.016), had a higher pancreas fibrosis score (7 ± 0.2 vs 4.8 ± 0.1; p ≤ 0.001), and trended toward lower islet yield (3,435 ± 361 islet cell equivalent vs 3,850 ± 128 islet cell equivalent; p = 0.28). Using multivariate logistic regression, patients with non-HGP causes (p = 0.019); lower severity of pancreas fibrosis (p < 0.001); shorter duration of years with pancreatitis (p = 0.008); and higher transplant islet cell equivalent per kilogram body weight (p ≤ 0.001) were more likely to achieve insulin independence (p < 0.001). There was a significant improvement in health-related quality of life from baseline by RAND 36-Item Short Form Health Survey and in physical and mental component health-related quality of life scores (p < 0.001). None of the patients in the entire cohort had cancer of pancreatic origin in the liver or elsewhere develop during 2,936 person-years of follow-up.

CONCLUSIONS

Total pancreatectomy and IAT in patients with chronic pancreatitis due to HGP cause provide long-term pain relief (90%) and preservation of β-cell function. Patients with chronic painful pancreatitis due to HGP with a high lifetime risk of pancreatic cancer should be considered earlier for TP-IAT before pancreatic inflammation results in a higher degree of pancreatic fibrosis and islet cell function loss.

Emerging roles for A20 in islet biology and pathology

A20 is most characteristically described in terms relating to inflammation and inflammatory pathologies. The emerging understanding of inflammation in the etiology of diabetes mellitus lays the framework for considering a central role for A20 in this disease process. Diabetes mellitus is considered a major health issue, and describes a group of common metabolic disorders pathophysiologically characterized by hyperglycemia. Within islets of Langherhans, the endocrine powerhouse of the pancreas, are the insulin-producing pancreatic beta-cells. Loss of beta-cell mass and function to inflammation and apoptosis is a major contributing factor to diabetes. Consequently, restoring functional beta-cell mass via transplantation represents a therapeutic option for diabetes. Unfortunately, transplanted islets also suffers from loss of beta-cell function and mass fueled by a multifactorial inflammatory cycle triggered by islet isolation prior to transplantation, the ischemic environment at transplantation as well as allogeneic or recurrent auto-immune responses. Activation of the transcription factor NF-kappaB is a central mediator of inflammatory mediated beta-cell dysfunction and loss. Accordingly, a plethora of strategies to block NF-kappaB activation in islets and hence limit beta-cell loss have been explored, with mixed success. We propose that the relatively poor efficacy of NF-kappaB blockade in beta-cells is due to concommittant loss of the important, NF-kappaB regulated anti-apoptotic and anti-inflammatory protein A20. A20 has been identified as a beta-cell expressed gene, raising questions about its role in beta-cell development and function, and in beta-cell related pathologies. Involvement of apoptosis, inflammation and NF-kappaB activation as beta-cell factors contributing to the pathophysiology of diabetes, coupled with the knowledge that beta-cells express the A20 gene, implies an important role for A20 in both normal beta-cell biology as well as beta-cell related pathology. Genome wide association studies (GWAS) linking single nucleotide polymorphisms in the A20 gene with the occurrence of diabetes and its complications support this hypothesis. In this chapter we review data supporting the role of A20 in beta-cell health and disease. Furthermore, by way of their specialized function in metabolism, pancreatic beta-cells also provide opportunities to explore the biology of A20 in scenarios beyond inflammation.

Death and dysfunction of transplanted β-cells: lessons learned from type 2 diabetes?

β-Cell replacement by islet transplantation is a potential curative therapy for type 1 diabetes. Despite advancements in islet procurement and immune suppression that have increased islet transplant survival, graft function progressively declines, and many recipients return to insulin dependence within a few years posttransplant. The progressive loss of β-cell function in islet transplants seems unlikely to be explained by allo- and autoimmune-mediated mechanisms alone and in a number of ways resembles β-cell failure in type 2 diabetes. That is, both following transplantation and in type 2 diabetes, islets exhibit decreased first-phase glucose-stimulated insulin secretion, impaired proinsulin processing, inflammation, formation of islet amyloid, signs of oxidative and endoplasmic reticulum stress, and β-cell death. These similarities suggest common mechanisms may underlie loss of insulin production in both type 2 diabetes and islet transplantation and point to the potential for therapeutic approaches used in type 2 diabetes that target the β-cell, such as incretin-based therapies, as adjuncts for immunosuppression in islet transplantation.