Transplantation of isolated pancreatic islets into the portal vein of diabetic rats

Total pancreatectomy sequelae and quality of life: results of islet autotransplantation as a possible mitigation strategy

Total pancreatectomy (TP) is a procedure weighed down not only by postoperative morbidity and mortality but also by long-term effects as a consequence of endocrine and exocrine pancreatic insufficiency. While the latter is now managed quite effectively with pancreatic enzyme replacement therapy, the former remains a challenge. The diabetes resulting after TP, with the complete loss of endogenous insulin and contraregulatory hormones, is characterized by important glycemic variations and is, therefore, frequently referred to as "brittle diabetes". One method to reduce the impact of brittle diabetes in patients undergoing TP is the re-infusion of autologous pancreatic islets isolated from the resected pancreas. Indications to islet autotransplantation (IAT), originally described for patients undergoing TP for chronic pancreatitis, have since been extended to selected patients with other benign and malignant diseases of pancreas. This review recaps on the literature regarding long-term postoperative complications, their impact on quality of life after TP and the role of IAT.

New Aspects of Diabetes Research and Therapeutic Development

Both type 1 and type 2 diabetes mellitus are advancing at exponential rates, placing significant burdens on health care networks worldwide. Although traditional pharmacologic therapies such as insulin and oral antidiabetic stalwarts like metformin and the sulfonylureas continue to be used, newer drugs are now on the market targeting novel blood glucose-lowering pathways. Furthermore, exciting new developments in the understanding of beta cell and islet biology are driving the potential for treatments targeting incretin action, islet transplantation with new methods for immunologic protection, and the generation of functional beta cells from stem cells. Here we discuss the mechanistic details underlying past, present, and future diabetes therapies and evaluate their potential to treat and possibly reverse type 1 and 2 diabetes in humans. SIGNIFICANCE STATEMENT: Diabetes mellitus has reached epidemic proportions in the developed and developing world alike. As the last several years have seen many new developments in the field, a new and up to date review of these advances and their careful evaluation will help both clinical and research diabetologists to better understand where the field is currently heading.

Human pancreatic tissue dissociation enzymes for islet isolation: Advances and clinical perspectives

BACKGROUND AND AIMS

Successful clinical human allo or auto-islet transplantation requires the recovery of a sufficient number of functional islets from either brain-dead or chronic pancreatitis pancreases respectively.

METHODS

In the last two decades (2000-2019), significant progress has been made in improving the human islet isolation procedures and in standardizing the use of different tissue dissociation enzyme (TDE; a mixture of collagenase and protease enzymes) blends to recover higher islet yields.

RESULTS AND CONCLUSIONS

This review presents information focusing on properties and role of TDE blends during the islet isolation process, particularly emphasizing on the current developments, associated challenges and future perspectives within the field.

3D Bioprinting of Functional Islets of Langerhans in an Alginate/Methylcellulose Hydrogel Blend

Transplantation of pancreatic islets is a promising strategy to alleviate the unstable blood-glucose control that some patients with diabetes type 1 exhibit and has seen many advances over the years. Protection of transplanted islets from the immune system can be accomplished by encapsulation within a hydrogel, the most investigated of which is alginate. In this study, islet encapsulation is combined with 3D extrusion bioprinting, an additive manufacturing method which enables the fabrication of 3D structures with a precise geometry to produce macroporous hydrogel constructs with embedded islets. Using a plottable hydrogel blend consisting of clinically approved ultrapure alginate and methylcellulose (Alg/MC) enables encapsulating pancreatic islets in macroporous 3D hydrogel constructs of defined geometry while retaining their viability, morphology, and functionality. Diffusion of glucose and insulin in the Alg/MC hydrogel is comparable to diffusion in plain alginate; the embedded islets continuously produce insulin and glucagon throughout the observation and still react to glucose stimulation albeit to a lesser degree than control islets.

Memory-like Liver Natural Killer Cells are Responsible for Islet Destruction in Secondary Islet Transplantation

We previously demonstrated the pivotal role of natural killer (NK) cells in islet graft loss during the early phase after intraportal syngeneic islet transplantation (IT). Liver-resident DX5^- NK cells were reported to possess memory-like properties, distinguishing them from conventional DX5⁺ NK cells. Here, we investigated the impact of primary IT-induced liver DX5^- NK cells on the engraftment of secondary-transplanted islets in mice. The culture of liver NK cells isolated from naive mice with TNF-α, IFN-γ, and IL-lβ, mimicking instant blood-mediated inflammatory reaction, led to significantly increased DX5^- NK cell percentage among total liver NK cells. Consistently, the prolonged expansion of DX5^- CD69⁺ TRAIL⁺ CXCR3⁺ NK cells was observed after intraportal IT of 300 syngeneic islets (marginal mass). In most diabetic mice, 400 syngeneic islets of primary IT were sufficient to achieve normoglycaemia, whereas the same mass after secondary IT failed to induce normoglycaemia in mice that received 200 syngeneic islets during primary IT. These findings indicated that liver-resident DX5^- NK cells significantly expanded even after syngeneic IT, and that these memory-like NK cells may target both originally engrafted and secondary-transplanted islets. Furthermore, anti-TNF-α treatment suppressed the expansion of liver-resident DX5^- NK cells, resulting in successful islet engraftment after sequential ITs.

A Novel Subcutaneous Site of Islet Transplantation Superior to the Liver

BACKGROUND

Islet transplantation is an attractive treatment for patients with insulin-dependent diabetes mellitus, and currently, the liver is the favored transplantation site. However, an alternative site is desirable because of the low efficiency of hepatic transplantation, requiring 2 to 3 donors for a single recipient, and because the transplanted islets cannot be accessed or retrieved.

METHODS

We developed a novel procedure of islet transplantation to the inguinal subcutaneous white adipose tissue (ISWAT) of mice and described functional and morphological characteristics of transplanted syngeneic islets. Also, it was determined whether islet allograft rejection in the ISWAT can be prevented by immunosuppressive agents. Furthermore, it was examined whether human islets function when grafted in this particular site of immune-deficient mice.

RESULTS

In this site, transplanted islets are engrafted as clusters and function to reverse streptozotocin-induced diabetes in mice. Importantly, transplanted islets can be visualized by computed tomography and are easily retrievable, and allograft rejection is preventable by blockade of costimulatory signals. Of much importance, the efficiency of islet transplantation in this site is superior to the liver, in which hyperglycemia of diabetic recipient mice is ameliorated after transplantation of 200 syngeneic islets (the islet number yielded from 1 mouse pancreas) to the ISWAT but not to the liver. Furthermore, human islets transplanted in this particular site function to reverse diabetes in immune-deficient mice.

CONCLUSIONS

Thus, the ISWAT is superior to the liver as the site of islet transplantation, which may lead to improved outcome of clinical islet transplantation.

Tissue-engineering approaches in pancreatic islet transplantation

Pancreatic islet transplantation is a promising alternative to whole-pancreas transplantation as a treatment of type 1 diabetes mellitus. This technique has been extensively developed during the past few years, with the main purpose of minimizing the complications arising from the standard protocols used in organ transplantation. By using a variety of strategies used in tissue engineering and regenerative medicine, pancreatic islets have been successfully introduced in host patients with different outcomes in terms of islet survival and functionality, as well as the desired normoglycemic control. Here, we describe and discuss those strategies to transplant islets together with different scaffolds, in combination with various cell types and diffusible factors, and always with the aim of reducing host immune response and achieving islet survival, regardless of the site of transplantation.

Functional Role of Circular RNA in Regenerative Medicine

Every year, millions of people around the world suffer from different forms of tissue trauma. Regenerative medicine refers to therapy that replaces the injured organ or cells. Stem cells are the frontiers and hotspots of current regenerative medicine research. Circular RNAs (circRNAs) are essential for the early development of many species. It was found that they could guide stem cell differentiation through interacting with certain microRNAs (miRNAs). Based on this concept, it is meaningful to look into how circRNAs influence stem cells and its role in regenerative medicine. In this chapter we will discuss the functional roles of circRNAs in the prevention, repair, or progression of chronic diseases, through the communication between stem cells.

Endothelial chimerism and vascular sequestration protect pancreatic islet grafts from antibody-mediated rejection

Humoral rejection is the most common cause of solid organ transplant failure. Here, we evaluated a cohort of 49 patients who were successfully grafted with allogenic islets and determined that the appearance of donor-specific anti-HLA antibodies (DSAs) did not accelerate the rate of islet graft attrition, suggesting resistance to humoral rejection. Murine DSAs bound to allogeneic targets expressed by islet cells and induced their destruction in vitro; however, passive transfer of the same DSAs did not affect islet graft survival in murine models. Live imaging revealed that DSAs were sequestrated in the circulation of the recipients and failed to reach the endocrine cells of grafted islets. We used murine heart transplantation models to confirm that endothelial cells were the only accessible targets for DSAs, which induced the development of typical microvascular lesions in allogeneic transplants. In contrast, the vasculature of DSA-exposed allogeneic islet grafts was devoid of lesions because sprouting of recipient capillaries reestablished blood flow in grafted islets. Thus, we conclude that endothelial chimerism combined with vascular sequestration of DSAs protects islet grafts from humoral rejection. The reduced immunoglobulin concentrations in the interstitial tissue, confirmed in patients, may have important implications for biotherapies such as vaccines and monoclonal antibodies.

Cyclosporine Does not Inhibit the Process of Revascularization of Pancreatic Islet Transplantation

The immunosuppressive drug cyclosporin-A (CsA) has been widely used to prevent pancreatic islet allograft rejection. Because it has been suggested that CsA may inhibit the process of revascularization of transplanted islets, the purpose of the study was to analyze by a double indirect immunofluorescence technique the revascularization process of isolated islets grafted in the liver and in the renal subcapsular space of rats treated with immunosuppressive doses of CsA. Lewis rats were grafted with either Lewis (isografts) or Wistar (allografts) pancreatic islets obtained by collagenase digestion. Rats were killed at different days after implantation and the liver and kidney bearing the grafted islets were snap frozen and immunohistochemically stained with a double immunofluorescence technique using a rabbit antifactor-VIII antiserum (which labels endothelial cells) and a guinea pig antiinsulin antibody. Islets implanted into nonimmunosuppressed hosts completed revascularization by days 3-7 after transplantation, as shown by the detection of endothelial cells within and surrounding the islets. The identical staining pattern of revascularization was observed in nonrejecting allografts as well as in isografts treated with CsA. We conclude that CsA did not inhibit the process of revascularization of rat islets after free transplantation. This finding is relevant for human islet transplantation, where CsA is currently employed to prevent kidney and islet allograft rejection. Copyright © 1997 Elsevier Science Inc.

Effect of Fusidic Acid on Pancreatic Islet Allograft Rejection

We examined in fully mismatched rats, the survival of pancreatic islet allografts in recipients treated with either fusidic acid (FA), an antistaphyllococcal antibiotic that has been shown to possess an immunosuppressive effect in vitro and in vivo, or cyclosporin-A (CsA). Islets were isolated by collagenase digestion, separated from acinar tissue by handpicking under a dissecting microscope and transplanted into the liver by portal vein injection of streptozotocin(STZ)-induced diabetic rats. The results indicated that while a temporary immunosuppression with CsA achieved an indefinite islet allograft survival, FA administered to recipients daily was not able to prevent islet allograft rejection across a major histocompatibility barrier. We conclude that despite the fact that fusidic acid has been claimed to act as an immunosuppressant drug in vitro with effects similar to those of CsA, unlike CsA, FA given either orally or by s.c. injection was not effective to prolong islet allograft survival in vivo. Copyright © 1997 Elsevier Science Inc.

Effects of Caffeine and Acetylcholine on Glucose-Stimulated Insulin Release from Islet Transplants in Mice

In mouse islet grafts under the kidney capsule, the potentiating responsiveness to acetylcholine was markedly attenuated after a few weeks. The question arose as to whether transplanted islets show an decreased responsiveness to potentiators in general. The effect of caffeine on glucose-induced insulin secretion was, therefore, examined. Intrastrain transplantation was performed in NMRI and BALB/c mice, and islet grafts were removed and perifused in vitro after 3 and 12 wk. In grafts from both NMRI and BALB/c mice, 16.7 mmol/L glucose induced a biphasic insulin release. When 1 or 5 mmol/L caffeine was included in the perifusion medium, there was a marked potentiation of the glucose-induced insulin release that was at least as responsiveness as fresh untransplanted islets. In the absence of caffeine, 3-wk-old BALB/c grafts reacted less strongly to acetylcholine than did untransplanted islets. The addition of 1 mmol/L caffeine did not enhance the potentiating effect of acetylcholine, whether in untransplanted or transplanted islets. Rather, the interaction between caffeine and acetylcholine appeared negative. We concluded that the glucose-induced insulin secretion exhibits a diminished potentiatory responsiveness to acetylcholine but not to caffeine. The displacement and denervation of transplanted islets is likely to affect either the cholinergic receptors or their mediated influence on intracellular calcium. Copyright © 1997 Elsevier Science Inc.

α-1 Antitrypsin Enhances Islet Engraftment by Suppression of Instant Blood-Mediated Inflammatory Reaction

Islet cell transplantation has limited effectiveness because of an instant blood-mediated inflammatory reaction (IBMIR) that occurs immediately after cell infusion and leads to dramatic β-cell death. In intraportal islet transplantation models using mouse and human islets, we demonstrated that α-1 antitrypsin (AAT; Prolastin-C), a serine protease inhibitor used for the treatment of AAT deficiency, inhibits IBMIR and cytokine-induced inflammation in islets. In mice, more diabetic recipients reached normoglycemia after intraportal islet transplantation when they were treated with AAT compared with mice treated with saline. AAT suppressed blood-mediated coagulation pathways by diminishing tissue factor production, reducing plasma thrombin-antithrombin complex levels and fibrinogen deposition on islet grafts, which correlated with less graft damage and apoptosis. AAT-treated mice showed reduced serum tumor necrosis factor-α levels, decreased lymphocytic infiltration, and decreased nuclear factor (NF)-κB activation compared with controls. The potent anti-inflammatory effect of AAT is possibly mediated by suppression of c-Jun N-terminal kinase (JNK) phosphorylation. Blocking JNK activation failed to further reduce cytokine-induced apoptosis in β-cells. Taken together, AAT significantly improves islet graft survival after intraportal islet transplantation by mitigation of coagulation in IBMIR and suppression of cytokine-induced JNK and NF-κB activation. AAT-based therapy has the potential to improve graft survival in human islet transplantation and other cellular therapies on the horizon.

Brief review: cell replacement therapies to treat type 1 diabetes mellitus

Human embryonic stem cells (hESCs) and induced pluripotent cells (iPSCs) have the potential to differentiate into any somatic cell, making them ideal candidates for cell replacement therapies to treat a number of human diseases and regenerate damaged or non-functional tissues and organs. Key to the promise of regenerative medicine is developing standardized protocols that can safely be applied in patients. Progress towards this goal has occurred in a number of fields, including type 1 diabetes mellitus (T1D). During the past 10 years, significant technological advances in hESC/iPSC biochemistry have provided a roadmap to generate sufficient quantities of glucose-responsive, insulin-producing cells capable of eliminating diabetes in rodents. Although many of the molecular mechanisms underlying the genesis of these cells remain to be elucidated, the field of cell-based therapeutics to treat T1D has advanced to the point where the first Phase I/II trials in humans have begun. Here, we provide a concise review of the history of cell replacement therapies to treat T1D from islet transplantations and xenotranplantation, to current work in hESC/iPSC. We also highlight the latest advances in efforts to employ insulin-producing, glucose-responsive β-like cells derived from hESC as therapeutics.

Evolution of Islet Transplantation for the Last 30 Years

In this article, we will review the changes that have occurred in islet transplantation at the birth of Pancreas 30 years ago. The first attempts at β-cell replacement in humans, pancreas and islet transplantation, were performed in the 1960s and 1970s. Although pancreas transplantation has been an accepted treatment for severe labile diabetes predating the emergence of the journal, allogeneic islet transplantation remains experimental. Current investigations within islet transplantation focus to improve islet function after transplantation. Improving islet viability during isolation, exploring ways to increase engraftment, and protection from the host immune system are some of the goals of these investigative efforts. The major barriers to clinical islet transplantation are shortage of human pancreas, the need for immunosuppression, and the inadequacy of the islet isolation process. It is generally accepted that islet encapsulation is an immunoisolation tool with good potential to address the first 2 of those barriers. We have therefore devoted a major part of this review to the critical factors needed to make it a clinical reality. With improved islet isolation techniques and determination of the best site of engraftment as well as improved encapsulation techniques, we hope that islet transplantation could someday achieve routine clinical use.

Improving pancreatic islet in vitro functionality and transplantation efficiency by using heparin mimetic peptide nanofiber gels

Pancreatic islet transplantation is a promising treatment for type 1 diabetes. However, viability and functionality of the islets after transplantation are limited due to loss of integrity and destruction of blood vessel networks. Thus, it is important to provide a proper mechanically and biologically supportive environment for enhancing both in vitro islet culture and transplantation efficiency. Here, we demonstrate that heparin mimetic peptide amphiphile (HM-PA) nanofibrous network is a promising platform for these purposes. The islets cultured with peptide nanofiber gel containing growth factors exhibited a similar glucose stimulation index as that of the freshly isolated islets even after 7 days. After transplantation of islets to STZ-induced diabetic rats, 28 day-long monitoring displayed that islets that were transplanted in HM-PA nanofiber gels maintained better blood glucose levels at normal levels compared to the only islet transplantation group. In addition, intraperitoneal glucose tolerance test revealed that animals that were transplanted with islets within peptide gels showed a similar pattern with the healthy control group. Histological assessment showed that islets transplanted within peptide nanofiber gels demonstrated better islet integrity due to increased blood vessel density. This work demonstrates that using the HM-PA nanofiber gel platform enhances the islets function and islet transplantation efficiency both in vitro and in vivo.

The co-transplantation of bone marrow derived mesenchymal stem cells reduced inflammation in intramuscular islet transplantation

Aims/Hypothesis

Although the muscle is one of the preferable transplant sites in islet transplantation, its transplant efficacy is poor. Here we attempted to determine whether an intramuscular co-transplantation of mesenchymal stem cells (MSCs) could improve the outcome.

Methods

We co-cultured murine islets with MSCs and then analyzed the morphological changes, viability, insulin-releasing function (represented by the stimulation index), and gene expression of the islets. We also transplanted 500 islets intramuscularly with or without 5 × 10⁵ MSCs to diabetic mice and measured their blood glucose level, the glucose changes in an intraperitoneal glucose tolerance test, and the plasma IL-6 level. Inflammation, apoptosis, and neovascularization in the transplantation site were evaluated histologically.

Results

The destruction of islets tended to be prevented by co-culture with MSCs. The stimulation index was significantly higher in islets co-cultured with MSCs (1.78 ± 0.59 vs. 7.08 ± 2.53; p = 0.0025). In terms of gene expression, Sult1c2, Gstm1, and Rab37 were significantly upregulated in islets co-cultured with MSCs. Although MSCs were effective in the in vitro assays, they were only partially effective in facilitating intramuscular islet transplantation. Co-transplanted MSCs prevented an early inflammatory reaction from the islets (plasma IL-6; p = 0.0002, neutrophil infiltration; p = 0.016 inflammatory area; p = 0.021), but could not promote neovascularization in the muscle, resulting in the failure of many intramuscular transplanted islets to engraft.

Conclusions

In conclusion, co-culturing and co-transplanting MSCs is potentially useful in islet transplantation, especially in terms of anti-inflammation, but further augmentation for an anti-apoptosis effect and neovascularization is necessary.

HMGB1-Mediated Early Loss of Transplanted Islets Is Prevented by Anti-IL-6R Antibody in Mice

OBJECTIVES

The limited success in achieving insulin independence of patients with type 1 diabetes mellitus after islet transplantation from a single donor, mainly due to early loss of transplanted islets, hampers clinical application of islet transplantation. Previously, we have shown in mice that the early loss of transplanted islets in the liver, the site of islet transplantation, is caused by innate immune rejection triggered by high-mobility group box 1 (HMGB1) protein released from transplanted islets. We herein determined whether the HMGB1-mediated early loss of transplanted mouse islets is prevented by anti-interleukin-6 receptor (IL-6R) antibody.

METHODS

The effect of anti-IL-6R antibody on amelioration of hyperglycemia in streptozocin-induced diabetic mice receiving 200 islets into the liver from a single donor was evaluated in association with HMGB1-stimulated interferon-γ production of hepatic mononuclear cells.

RESULTS

Hyperglycemia of diabetic mice receiving 200 syngeneic islets was ameliorated with down-regulation of interferon-γ production of hepatic natural killer T cells and neutrophils when anti-IL-6R was administered at the time of transplantation. This beneficial effect was also seen in allografts when alloimmune rejection was prevented by anti-CD4 antibody.

CONCLUSIONS

These findings demonstrate that anti-IL-6R antibody prevented the early loss of intrahepatic islet grafts with inhibiting HMGB1-induced immune activation after islet transplantation.

Stem cell therapy. Use of differentiated pluripotent stem cells as replacement therapy for treating disease

Pluripotent stem cells (PSCs) directed to various cell fates holds promise as source material for treating numerous disorders. The availability of precisely differentiated PSC-derived cells will dramatically affect blood component and hematopoietic stem cell therapies and should facilitate treatment of diabetes, some forms of liver disease and neurologic disorders, retinal diseases, and possibly heart disease. Although an unlimited supply of specific cell types is needed, other barriers must be overcome. This review of the state of cell therapies highlights important challenges. Successful cell transplantation will require optimizing the best cell type and site for engraftment, overcoming limitations to cell migration and tissue integration, and occasionally needing to control immunologic reactivity, as well as a number of other challenges. Collaboration among scientists, clinicians, and industry is critical for generating new stem cell-based therapies.

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.

Chronic pancreatitis and primary sclerosing cholangitis--first report of intrahepatic autologous islet transplantation

BACKGROUND

We are reporting first successful intrahepatic autologous islet transplantation after total pancreatectomy in a patient with chronic pancreatitis and primary sclerosing cholangitis.

METHODS

Total pancreatectomy and subsequent islet autotransplantation were performed in a 16-year-old boy with intractable pain due to chronic pancreatitis in the setting of ulcerative colitis and primary sclerosing cholangitis (PSC). Liver biopsy revealed PSC with focal bridging fibrosis. The pancreas was surgically removed and digested, and islets were isolated, highly purified, and infused intraportally.

RESULTS

Over 18-month follow-up, the patient did not show progression of chronic liver disease or signs of portal hypertension. Magnetic resonance cholangiopancreatography revealed no new changes, and liver biopsy did not show progression of the periportal fibrosis. Pain medication was weaned over 12 months at which time glycemic control was excellent without exogenous insulin supplementation. HbgA1c was 5.9. Fifteen months after the procedure, stimulation with a mixed meal led to a fourfold increase of serum C-peptide and an eightfold increase of insulin level.

CONCLUSION

Pancreatic autologous islets can be successfully transplanted into a liver affected by PSC without compromising hepatic or graft function. Durability of the procedure may be limited in the future by the natural course of the liver injury caused by PSC.

Regenerative medicine for diabetes: differentiation of human pluripotent stem cells into functional β-cells in vitro and their proposed journey to clinical translation

Diabetes is a group of metabolic diseases, rising globally at an alarming rate. Type 1 (juvenile diabetes) is the autoimmune version of diabetes where the pancreas is unable to produce insulin, whereas type 2 (adult onset diabetes) is caused due to insulin resistance of the cells. In either of the cases, elevated blood glucose levels are observed which leads to progressive comorbidity like renal failure, cardiovascular disease, retinopathy, etc. Metformin, sulphonyl urea group of drugs, as well as insulin injections are the available therapies. In advanced cases of diabetes, the drug alone or drug in combination with insulin injections are not able to maintain a steady level of blood glucose. Moreover, frequent insulin injections are rather cumbersome for the patient. So, regenerative medicine could be a permanent solution for fighting diabetes. Islet transplantation has been tried with a limited amount of success on a large population of diabetics because of the shortage of cadaveric pancreas. Therefore, the best proposed alternative is regenerative medicine involving human pluripotent stem cell (hPSC)-derived beta islet transplantation which can be obtained in large quantities. Efficient protocols for in vitro differentiation of hPSC into a large number of sustained insulin-producing beta cells for transplantation will be considered to be a giant leap to address global rise in diabetic cases. Although most of the protocols mimic in vivo pancreatic development in humans, considerable amount of lacuna persists for near-perfect differentiation strategies. Moreover, beta islets differentiated from hPSC have not yet been successfully translated under clinical scenario.

Nonhuman primate models of type 1 diabetes mellitus for islet transplantation

Islet transplantation is an attractive treatment of type 1 diabetes mellitus (T1DM). Animal models of diabetes mellitus (DM) contribute a lot to the experimental studies of islet transplantation and to evaluations of isolated islet grafts for future clinical applications. Diabetic nonhuman primates (NHPs) represent the suitable models of DMs to better evaluate the effectiveness of islet transplantation, to assess new strategies for controlling blood glucose (BG), relieving immune rejection, or prolonging islet survival, and eventually to translate the preclinical data into tangible clinical practice. This review introduces some NHP models of DM, clarifies why and how the models should be used, and elucidates the usefulness and limitations of the models in islet transplantation.

Pretreatment of donor islets with the Na(+) /Ca(2+) exchanger inhibitor improves the efficiency of islet transplantation

Pancreatic islet transplantation is an attractive therapy for the treatment of insulin-dependent diabetes mellitus. However, the low efficiency of this procedure necessitating sequential transplantations of islets with the use of 2-3 donors for a single recipient, mainly due to the early loss of transplanted islets, hampers its clinical application. Previously, we have shown in mice that a large amount of HMGB1 is released from islets soon after their transplantation and that this triggers innate immune rejection with activation of DC, NKT cells and neutrophils to produce IFN-γ, ultimately leading to the early loss of transplanted islets. Thus, HMGB1 release plays an initial pivotal role in this process; however, its mechanism remains unclear. Here we demonstrate that release of HMGB1 from transplanted islets is due to hypoxic damage resulting from Ca(2+) influx into β cells through the Na(+) /Ca(2+) exchanger (NCX). Moreover, the hypoxia-induced β cell damage was prevented by pretreatment with an NCX-specific inhibitor prior to transplantation, resulting in protection and long-term survival of transplanted mouse and human islets when grafted into mice. These findings suggest a novel strategy with potentially great impact to improve the efficiency of islet transplantation in clinical settings by targeting donor islets rather than recipients.

Potential role of mesenchymal stromal cells in pancreatic islet transplantation

Pancreatic islet transplantation is an attractive option for treatment of type 1 diabetes mellitus but maintaining long term islet function remains challenging. Mesenchymal stromal cells (MSCs), derived from bone marrow or other sources, are being extensively investigated in the clinical setting for their immunomodulatory and tissue regenerative properties. Indeed, MSCs have been already tested in some feasibility studies in the context of islet transplantation. MSCs could be utilized to improve engraftment of pancreatic islets by suppressing inflammatory damage and immune mediated rejection. In addition to their immunomodulatory effects, MSCs are known to provide a supportive microenvironmental niche by secreting paracrine factors and depositing extracellular matrix. These properties could be used for in vivo co-transplantation to improve islet engraftment, or for in vitro co-culture to prime freshly isolated islets prior to implantation. Further, tissue specific pancreatic islet derived MSCs may open new opportunities for its use in islet transplantation as those cells might be more physiological to pancreatic islets.

Animal models of diabetes mellitus for islet transplantation

Due to current improvements in techniques for islet isolation and transplantation and protocols for immunosuppressants, islet transplantation has become an effective treatment for severe diabetes patients. Many diabetic animal models have contributed to such improvements. In this paper, we focus on 3 types of models with different mechanisms for inducing diabetes mellitus (DM): models induced by drugs including streptozotocin (STZ), pancreatomized models, and spontaneous models due to autoimmunity. STZ-induced diabetes is one of the most commonly used experimental diabetic models and is employed using many specimens including rodents, pigs or monkeys. The management of STZ models is well established for islet studies. Pancreatomized models reveal different aspects compared to STZ-induced models in terms of loss of function in the increase and decrease of blood glucose and therefore are useful for evaluating the condition in total pancreatomized patients. Spontaneous models are useful for preclinical studies including the assessment of immunosuppressants because such models involve the same mechanisms as type 1 DM in the clinical setting. In conclusion, islet researchers should select suitable diabetic animal models according to the aim of the study.

Wearable and implantable pancreas substitutes

A lifelong-implanted and completely automated artificial or bioartificial pancreas (BAP) is the holy grail for type 1 diabetes treatment, and could be a definitive solution even for other severe pathologies, such as pancreatitis and pancreas cancer. Technology has made several important steps forward in the last years, providing new hope for the realization of such devices, whose feasibility is strictly connected to advances in glucose sensor technology, subcutaneous and intraperitoneal insulin pump development, the design of closed-loop control algorithms for mechatronic pancreases, as well as cell and tissue engineering and cell encapsulation for biohybrid pancreases. Furthermore, smart integration of the mentioned components and biocompatibility issues must be addressed, bearing in mind that, for mechatronic pancreases, it is most important to consider how to recharge implanted batteries and refill implanted insulin reservoirs without requiring periodic surgical interventions. This review describes recent advancements in technologies and concepts related to artificial and bioartificial pancreases, and assesses how far we are from a lifelong-implanted and self-working pancreas substitute that can fully restore the quality of life of a diabetic (or other type of) patient.

Management of adverse side-effects after chemotherapy in macaques as exemplified by streptozotocin: case studies and recommendations

The chemotherapeutic streptozotocin is used for induction of diabetes in animal models including non-human primates. Being a cytotoxic nitrosourea compound, it can be associated with adverse events (AEs), mainly nausea and emesis, nephrotoxicity, elevated liver transaminase levels, pulmonary oedema and, most prominently, metabolic acidosis: these can be severe in some cases. The incidence and gravity are to some extent related to the characteristics of the individual animal, diagnostic tools, prompt recognition of symptoms and supportive measures. Careful animal selection, dose adaptation and supportive actions such as renal protective hydration are the main tools in managing AEs, but do not fully eliminate unavoidable and sometimes life-threatening conditions. In our centre we have built experience in a cohort of 78 cynomolgus and rhesus macaques in which six cases manifested severe AEs (8%). This experience has prompted implementation of strategies for early detection and management of adverse effects, together with an animal refinement programme. We present here specific pretreatment regimens, post-infusion laboratory evaluations, and flow charts to assess/treat metabolic acidosis and precipitating factors. Case reports of the six animals with severe AEs are presented to illustrate management of AEs, especially metabolic acidosis, and criteria for early euthanasia where appropriate. We conclude that improved monitoring and validated tools allow for optimal management of adverse effects in an early stage of their manifestation. Reduced morbidity and mortality not only improve individual animal wellbeing but also avoid model-induced confounding that diminishes the translational value of the experimental protocol.

Pancreatic islet cell transplantation: an update for interventional radiologists

Pancreatic islet cell transplantation is a promising cellular-based therapy for type 1 diabetes mellitus. This procedure involves portal venous injection of islet cells and affords 1-year insulin independence in as many as 80% of recipients. Although transplant surgeons represent historical drivers of islet therapy, requirement for image guidance and transcatheter techniques has fostered collaboration with interventional radiologists, who are positioned to play a significant role in clinical performance of islet transplantation and in basic science research in this field. This review article aims to familiarize interventional radiologists with islet cell transplantation patient selection, procedure technique, clinical outcomes, and future clinical and research avenues.

Islet transplantation in rodents. Do encapsulated islets really work?

CONTEXT

Diabetes mellitus type I affects around 240 million people in the world and only in the USA 7.8% of the population. It has been estimated that the costs of its complications account for 5% to 10% of the total healthcare spending around the world. According to World Health Organization, 300 million people are expected to develop diabetes mellitus by the year 2025. The pancreatic islet transplantation is expected to be less invasive than a pancreas transplant, which is currently the most commonly used approach.

OBJECTIVES

To compare the encapsulated and free islet transplantation in rodents looking at sites of islet implantation, number of injected islets, viability and immunosuppression.

METHODS

A literature search was conducted using MEDLINE/PUBMED and SCIELO with terms about islet transplantation in the rodent from 2000 to 2010. We found 2,636 articles but only 56 articles from 2000 to 2010 were selected.

RESULTS

In these 56 articles used, 34% were encapsulated and 66% were nonencapsulated islets. Analyzing both types of islets transplantation, the majority of the encapsulated islets were implanted into the peritoneal cavity and the nonencapsulated islets into the liver, through the portal vein. In addition, the great advantage of the peritoneal cavity as the site of islet transplantation is its blood supply. Both vascular endothelial cells and vascular endothelial growth factor were used to stimulate angiogenesis of the islet grafts, increasing the vascularization rapidly after implantation. It also has been proven that there is influence of the capsules, since the larger the capsule more chances there are of central necrosis. In some articles, the use of immunosuppression demonstrated to increase the life expectancy of the graft.

CONCLUSION

While significant progress has been made in the islets transplantation field, many obstacles remain to be overcome. Microencapsulation provides a means to transplant islets without immunosuppressive agents and may enable the performance of xenotransplantation. The use of alternative donor sources, fewer islets per capsule and the appropriate deployment location, such as the peritoneal cavity, may give a future perspective to the application of immunoprotective capsules and viability in clinical practice. A variety of strategies, such as genetic engineering, co-encapsulation, improvement in oxygen supply or the establishment of hypoxia resistance will also improve the islet transplantation performance. It remains to be determined which combination of strategies with encapsulation can fulfill the promise of establishing a simple and safe transplantation as a cure for diabetes.

Advances and challenges in islet transplantation: islet procurement rates and lessons learned from suboptimal islet transplantation

The initial step in successful islet transplantation is procurement of healthy donor islets. Given the limited number of donor pancreata selected for islet isolation and that islets from multiple donors are typically required to obtain insulin independence, it is critical to improve pancreas procurement rates and yield of islets for transplantation. Islets are delicate microorgans that are susceptible to apoptosis, hypoxia, and ischemia during isolation, culture, and the peritransplant period. Once the islets are engrafted, both prompt revascularization and protection from beta-cell death and graft rejection are key to secure long-term survival and function. To facilitate the engraftment of more robust islets suitable for combating the challenging isolation period and proinflammatory transplantation milieu, numerous approaches have been employed to prevent beta-cell dysfunction and death including immune modulation, prevention of apoptosis and hypoxia, as well as stimulation of growth factors, angiogenesis, and reinnervation. In addition to briefly discussing islet isolation procedures, procurement rates, and islet transplantation, the relevant literature pertaining to successful suboptimal islet transplantation is reviewed to provide insight into potential approaches to balance the limited supply of available donor islets.

Islet versus pancreas transplantation in Brazil: Defining criteria for pancreas allocation decision

BACKGROUND

Many studies have evaluated whether there are characteristics related to pancreas donors and the islet isolation process that can influence pancreatic islet yield. However, this analysis has not yet been performed in Brazil, one of the world leaders in whole pancreas organ transplantation (WOPT), where pancreas allocation for pancreatic islet transplantation (PIT) has no officially defined criteria. Definition of parameters that would predict the outcome of islet isolation from local pancreas donors would be useful for defining allocation priority in Brazil.

OBJECTIVE

To analyze the relationship between multiple donor-related and islet isolation variables with the total number of isolated pancreatic islet equivalents (IEQ) in a brazilian sample of pancreas donors.

METHODS

Several variables were analyzed in 74 pancreata relative to the outcome of total IEQs obtained at the end of the process.

RESULTS

In univariate analysis, body mass index (BMI) (p = 0.003), the presence of fatty infiltrates in the pancreas as observed during harvesting (p = 0.042) and pancreas digestion time (p = 0.046) were identified as variables related to a greater IEQ yield. In a multivariate analysis a statistically significant contribution to the variability of islet yield was found only for the BMI (p = 0.017). A ROC curve defined a BMI = 30 as a cut-off point, with pancreata from donors with BMI > 30 yielding more islets than donors with BMI < 30 (p< 0.001).

CONCLUSION

These data reinforce the importance of the donor BMI as a defining parameter for successful islet isolation and establishes this variable as a potential pancreas allocation criterion in Brazil, where there is unequal competition for good quality organs between WOPT and PIT.

Liposomal Formulations of Thrombomodulin Increase Engraftment after Intraportal Islet Transplantation

Early destruction of donor islet grafts due to an instant blood-mediated inflammatory reaction (IBMIR) remains a major obstacle in islet transplantation. Thrombomodulin plays an important role in limiting coagulation and inflammatory events through a variety of effects. In this study, we investigated the ability of thrombomodulin (TM), when reconstituted as a liposomal formulation, to enhance early syngeneic islet engraftment by minimizing or abrogating the IBMIR. Administration of TM significantly improved early engraftment of syngeneic islets after intraportal transplantation in diabetic mice. In the absence of treatment, conversion to euglycemia was observed among 46.6% (7/15) of recipients. In contrast, administration of TM led to euglycemia in 93.3% (14/15) of recipients ( p = 0.0142). Recipients that received TM exhibited a lower incidence of primary nonfunction and better glucose control over a 30-day period after transplantation. Fibrin deposition ( p < 0.05), neutrophil infiltration ( p < 0.05), expression of TNF-α and IL-β mRNA ( p < 0.05), as well as NF-κB activity ( p < 0.05) were significantly reduced in the liver of islet recipients having been treated with liposomal TM. These data demonstrate that TM significantly improves early syngeneic islet engraftment through effects that target both coagulation and inflammatory pathways.

Reversal of hyperglycemia in diabetic mouse models using induced-pluripotent stem (iPS)-derived pancreatic beta-like cells

Diabetes mellitus is characterized by either the inability to produce insulin (type 1 diabetes) or as insensitivity to insulin secreted by the body (type 2 diabetes). In either case, the body is unable to move blood glucose efficiently across cell membranes to be used. This leads to a variety of local and systemic detrimental effects. Current treatments for diabetes focus on exogenous insulin administration and dietary control. Here, we describe a potential cure for diabetes using a cellular therapy to ameliorate symptoms associated with both reduced insulin secretion and insulin sensitivity. Using induced pluripotent stem (iPS) cells, we were able to derive beta-like cells similar to the endogenous insulin-secreting cells in mice. These beta-like cells secreted insulin in response to glucose and corrected a hyperglycemic phenotype in two mouse models of type 1 and 2 diabetes via an iPS cell transplant. Long-term correction of hyperglycemia was achieved, as determined by blood glucose and hemoglobin A1c levels. These data provide an initial proof of principle for potential clinical applications of reprogrammed somatic cells in the treatment of diabetes type 1 or 2.

The isolated pancreatic islet as a micro-organ and its transplantation to cure diabetes: celebrating the legacy of Paul Lacy

Over the past three decades the pancreatic islet of Langerhans has taken center stage as an endocrine micro-organ whose glucoregulatory function is highly explicable on the basis of the increasingly well understood activities of three highly interactive secretory cells. Islet dysfunction underlies both type 1 and type 2 diabetes mellitus (DM); its protection from immune attack and gluco-and lipo-toxicity may prevent the development of DM; and its replacement by non-surgical transplantation may be curative of DM. During a career marked by vision, focus and tenacity, Paul Lacy contributed substantially to the development of each of these concepts. In this review we focus on Lacy's contribution to the development of the concept of the islet as a micro-organ, how this foreshadowed our current detailed understanding of single cell function and cell-cell interactions and how this led to a reduced model of islet function encouraging islet transplantation. Next, we examine how clinical allotransplantation, first undertaken by Lacy, has contributed to a more complex view of the interaction of islet endocrine cells with its circulation and neighboring tissues, both "in situ" and after transplantation. Lastly, we consider recent developments in some alternative approaches to treatment of DM that Lacy could glimpse on the horizon but did not have the chance to participate in.

High-mobility group box 1 is involved in the initial events of early loss of transplanted islets in mice

Islet transplantation for the treatment of type 1 diabetes mellitus is limited in its clinical application mainly due to early loss of the transplanted islets, resulting in low transplantation efficiency. NKT cell-dependent IFN-gamma production by Gr-1(+)CD11b(+) cells is essential for this loss, but the upstream events in the process remain undetermined. Here, we have demonstrated that high-mobility group box 1 (HMGB1) plays a crucial role in the initial events of early loss of transplanted islets in a mouse model of diabetes. Pancreatic islets contained abundant HMGB1, which was released into the circulation soon after islet transplantation into the liver. Treatment with an HMGB1-specific antibody prevented the early islet graft loss and inhibited IFN-gamma production by NKT cells and Gr-1(+)CD11b(+) cells. Moreover, mice lacking either of the known HMGB1 receptors TLR2 or receptor for advanced glycation end products (RAGE), but not the known HMGB1 receptor TLR4, failed to exhibit early islet graft loss. Mechanistically, HMGB1 stimulated hepatic mononuclear cells (MNCs) in vivo and in vitro; in particular, it upregulated CD40 expression and enhanced IL-12 production by DCs, leading to NKT cell activation and subsequent NKT cell-dependent augmented IFN-gamma production by Gr-1(+)CD11b(+) cells. Thus, treatment with either IL-12- or CD40L-specific antibody prevented the early islet graft loss. These findings indicate that the HMGB1-mediated pathway eliciting early islet loss is a potential target for intervention to improve the efficiency of islet transplantation.

Thrombomodulin improves early outcomes after intraportal islet transplantation

Primary islet nonfunction due to an instant blood mediated inflammatory reaction (IBMIR) leads to an increase in donor islet mass required to achieve euglycemia. In the presence of thrombin, thrombomodulin generates activated protein C (APC), which limits procoagulant and proinflammatory responses. In this study, we postulated that liposomal formulations of thrombomodulin (lipo-TM), due to its propensity for preferential uptake in the liver, would enhance intraportal engraftment of allogeneic islets by inhibiting the IBMIR. Diabetic C57BL/6J mice underwent intraportal transplantation with B10.BR murine islets. In the absence of treatment, conversion to euglycemia was observed among 29% of mice receiving 250 allo-islets. In contrast, a single infusion of lipo-TM led to euglycemia in 83% of recipients (p = 0.0019). Fibrin deposition (p < 0.0001), neutrophil infiltration (p < 0.0001), as well as expression TNF-alpha and IL-beta (p < 0.03) were significantly reduced. Significantly, thrombotic responses mediated by human islets in contact with human blood were also reduced by this approach. Lipo-TM improves the engraftment of allogeneic islets through a reduction in local thrombotic and inflammatory processes. As an enzyme-based pharmacotherapeutic, this strategy offers the potential for local generation of APC at the site of islet infusion, during the initial period of elevated thrombin production.

Islet transplantation: the quest for an ideal source

The progress of islet transplantation as a new therapy for patients with diabetes mellitus depends directly upon the development of efficient and practical immunoisolation methods for the supply of sufficient quantities of islet cells. Without these methods, large scale clinical application of this therapy would be impossible. Two eras of advances can be identified in the development of islet transplantation. The first was an era of experimental animal and human research that centered on islet isolation procedures and transplantation in different species as evidence that transplanted islets have the capability to reverse diabetes. The second was the era of the Edmonton protocol, when the focus became the standardization of isolation procedures and introduction of new immunosuppressive drugs to maintain human allograft transplantation. The quest for an alternative source for islets (xenographs, stem cells and cell cultures) to overcome the shortage of human islets was an important issue during these eras. This paper reviews the history of islet transplantation and the current procedures in human allotransplantation, as well as different types of immunoisolation methods. It explores novel approaches to enhancing transplantation site vascularity and islet cell function, whereby future immunoisolation technology could offer additional therapeutic advantages to human islet allotransplantation.

The Choice of Anatomical Site for Islet Transplantation

Islet transplantation into the portal vein is the current clinical practice. However, it has now been recognized that this implantation site has several characteristics that can hamper islet engraftment and survival, such as low oxygen tension, an active innate immune system, and the provocation of an inflammatory response (IBMIR). These factors result in the loss of many transplanted islets, mainly during the first hours or days after transplantation, which could in part explain the necessity for the transplantation of islets from multiple pancreas donors to cure type 1 diabetes. This increases the burden on the limited pool of donor organs. Therefore, an alternative anatomical site for islet transplantation that offers maximum engraftment, efficacious use of produced insulin, and maximum patient safety is urgently needed. In this review, the experience with alternative sites for islet implantation in clinical and experimental models is discussed. Subcutaneous transplantation guarantees maximum patient safety and has become clinically applicable. Future improvements could be achieved with innovative designs for devices to induce neovascularization and protect the islets from cellular rejection. However, other sites, such as the omentum, offer drainage of produced insulin into the portal vein for direct utilization in the liver. The use of pigs would not only overcome the shortage of transplantable islets, but genetic modification could result in the expression of human genes, such as complement regulatory or “anticoagulation” genes in the islets to overcome some site-specific disadvantages. Eventually, the liver will most likely be replaced by a site that allows long-term survival of islets from a single donor to reverse type 1 diabetes.