Islet Transplantation Research Papers - Academia.edu (original) (raw)

Transplantation of islets of Langerhans represents a viable therapeutic approach for the treatment of type 1 diabetes. Unfortunately, transplanted islets are susceptible to allogeneic recognition and rejection, recurrence of autoimmunity, and destruction by local inflammation at the site of implantation. The last of these phenomena might not only result in functional impairment and death of islet cells but could also contribute to amplifying the subsequent specific immune response. Induction of islet cell protection against inflammation could therefore be postulated to be a powerful means to improve overall graft fate. Heme oxygenase-1 (HO-1) has been described as an inducible protein capable of cytoprotection via radical scavenging and apoptosis prevention. The purpose of the present study was to analyze whether HO-1 upregulation in a ␤-cell line and in freshly isolated murine islets could result in protection from apoptosis and improve in vivo functional performance. HO-1 upregulation was induced reproducibly with protoporphyrins and was correlated with protection from apoptosis induced in vitro with proinflammatory cytokines or Fas engagement. Furthermore, in vivo HO-1 upregulation resulted in improved islet function in a model of marginal mass islet transplantation in rodents. Strategies aimed at inducing HO-1 upregulation might result in improved success in islet transplantation. Diabetes 50: [1983][1984][1985][1986][1987][1988][1989][1990][1991] 2001 T ype 1 diabetes results from the autoimmune destruction of pancreatic ␤-cells (1). Conventional therapy, based on the administration of exogenous insulin, often is characterized by the occurrence of systemic complications, including angiopathy and neuropathy. Improvement in metabolic control, through intensive insulin therapy, results in decreased incidence and progression of complications, but it is often associated with the occurrence of severe hypoglycemic episodes (2). Conversely, transplantation of islets of Langerhans, when successful, is characterized by excellent metabolic control in the absence of hypoglycemia (3).

- by Thierry Berney
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- Immune response, Diabetes, Membrane Proteins, Apoptosis

Diffusion coefficient of alginate microcapsules used in pancreatic islet transplantation, a method to cure type 1 diabetes Avid Najdahmadi, Jonathan R. T. Lakey, Elliot Botvinick Avid Najdahmadi, Jonathan R. T. Lakey, Elliot Botvinick, "Diffusion coefficient of alginate microcapsules used in pancreatic islet transplantation, a method to cure type 1 diabetes, Abstract: Pancreatic islet transplantation is a promising approach of providing insulin in type 1 diabetes. One strategy to protect islets from the host immune system is encapsulation within a porous biocompatible alginate membrane. This encapsulation provides mechanical support to the cells and allows selective diffusion of oxygen, nutrients and insulin while blocking immunoglobulins. These hydrogels form by diffusion of calcium ions into the polymer network and therefore they are highly sensitive to environmental changes and fluctuations in temperature. We investigated the effects of gel concentration, crosslinking time and ambient conditions on material permeability, volume, and rigidity, all of which may change the immunoisolating characteristics of alginate. To measure diffusion coefficient as a method to capture structural changes we studied the diffusion of fluorescently tagged dextrans of different molecular weight into the midplane of alginate microcapsules, the diffusion coefficient is then calculated by fitting observed fluorescence dynamics to the mathematical solution of 1-D diffusion into a sphere. These measurements were performed after incubation in different conditions as well as after an in vivo experiment in six immunocompetent mice for seven days. Additionally, the changes in gel volume after incubation at different temperatures and environmental conditions as well as changes in compression modulus of alginate gels during crosslinking were investigated. Our result show that increase of polymer concentration and crosslinking time leads to a decrease in volume and increase in compression modulus. Furthermore, we found that samples crosslinked and placed in physiological environment, experience an increase in volume. As expected, these volume changes affect diffusion rates of fluorescent dextrans, where volume expansion is correlated with higher calculated diffusion coefficient. This observation is critical to islet protection since higher permeability due to the expansion in vivo may lead to increased permeability to immunoglobulins. Capsules from the in vivo study showed similar volume expansion and increased permeability, indicating our in vitro assay is a good predictor of volume change in vivo.

- by Avid Najdahmadi
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- Diabetes, Targeted Drug Delivery, Drug delivery, Hydrogels

For reducing the corticosteroid (CS)-related side-effects, especially cardiovascular events, CS-sparing protocols have become increasingly common in pancreas transplantation (PT). Lympho-depleting induction antibodies, such as rabbit anti-thymocyte globulin (rATG) or alemtuzumab, have been widely used in successful trials. The results of various CS-sparing protocols combining calcineurin inhibitors (CNI) and mycophenolate or sirolimus, have been mixed for rejection and survival rates. Most of the studies were uncontrolled trials of low-risk patients, therefore the grade of evidence is limited. Large-scale prospective studies with long-term follow up are necessary to assess risks and benefits of CS-sparing regimens in PT before recommending such strategies as standard practice. Islet allo-transplantation for patients with brittle type 1 diabetes mellitus, less invasive and safer procedure than PT, has been attempted since late 1980s, but diabetogenic immunosuppressants at maintenance, mainly CS and high-dose CNI, prevented satisfactory results (10% insulin-independence at 1-year post-transplant). Since 2000, CS-free and CNI-reducing protocols, including more potent induction [daclizumab, OKT3c1(ala-ala) anti-CD3 antibody, rATG] and maintenance (sirolimus, mycophenolate) agents, have significantly improved short-term outcomes whereas long-term are still inadequate (from 80% to 20% insulin-independence from 1-to 5-year posttransplant). Main limitations are allo-and autoimmunity, immunosuppressionrelated islet and systemic toxicity and transplant site unsuitability, which tolerogenic protocols and biotechnological solutions may solve.

- by George Burke
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- Side Effects, Toxicity, Islet Transplantation, Immunosuppression

The present investigation deals with the microstructural evolution and mechanical properties optimization of a new titanium based TNTZ (Ti-29Nb-13Ta-4.6Zr) alloy through applying a proper heat treatment strategy. The TNTZ alloy was subjected to solution treatment and cooling procedure via different medias including liquid nitrogen, water, oil, static air and vacuum furnace. The slow cooling in vacuum furnace and static air resulted in precipitation of x phase. The formation of this phase secures an increase in the strength and hardness value, however stands detrimental to the ductility. The a 00 martensite is formed due to accelerated cooling in liquid nitrogen, water and oil. This phase remains neutral to the ductility of the alloy, while its excessive formation increases the hardness and shear strength. This study proposes the liquid nitrogen quenching as a process that optimizes the mechanical properties by rendering the highest strength while preserving the ductility.

- by Avid Najdahmadi
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- Diabetes, Biopolymers, Islet Transplantation

A B S T R A C T This review focuses on Type 1 diabetes mellitus (T1DM) and the role of bioengineering, nanotechnology and cell therapy in its treatment. T1DM is discussed in terms of its prevalence as well as the role of the extra cellular matrix (ECM) of the pancreas in its development and mode of action. Surface engineering strategies and the chemistries behind important cell encapsulation techniques, which are emerging from recent research in immunosuppression, are described. Key enabling technologies such as therapeutic agent immobilization on cells, oxygen releasing systems, gene delivery and bio imaging are assessed with respect to T1DM. These latest cell surface technologies provide unlimited possibilities for control of cell/ cell and cell/ECM interactions, allowing the ability to confer " immune camouflage ". Finally, we provide an outlook to the future of cell-based technologies for T1DM treatment and their likely deployment in clinical trials.

- by Fernanda Zamboni and +1
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- Stem cell and Regenerative medicine, Diabetes, Biomaterials and Tissue Engineering, Cell Encapsulation

Despite substantial advances in islet isolation methods and immunosuppressive protocol, pancreatic islet cell transplantation remains an experimental procedure currently limited to the most severe cases of type 1 diabetes mellitus. The objectives of this treatment are to prevent severe hypoglycemic episodes in patients with hypoglycemia unawareness and to achieve a more physiological metabolic control. Insulin independence and long termgraft function with improvement of quality of life have been obtained in several international islet transplant centers. However, experimental trials of islet transplantation clearly highlighted several obstacles that remain to be overcome before the procedure could be proposed to a much larger patient population. This review provides a brief historical perspective of islet transplantation, islet isolation techniques, the transplant procedure, immunosuppressive therapy, and outlines current challenges and future directions in clinical islet transplantation.

- by Hirohito Ichii
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- Surgery, Quality of life, Insulin, Islet Transplantation

Glycation is the nonenzymatic reaction of glucose, alpha-oxoaldehydes, and other saccharide derivatives with proteins, nucleotides, and lipids. Early glycation adducts (fructosamines) and advanced glycation adducts (AGEs) are formed. "Glycoxidation" is a term used for glycation processes involving oxidation. Sural, peroneal, and saphenous nerves of human diabetic subjects contained AGEs in the perineurium, endothelial cells, and pericytes of endoneurial microvessels and in myelinated and unmyelinated fibres localized to irregular aggregates in the cytoplasm and interstitial collagen and basement membranes. Pentosidine content was increased in cytoskeletal and myelin protein extracts of the sural nerve of human subjects and cytoskeletal proteins of the sciatic nerve of streptozotocin-induced diabetic rats. AGEs in the sciatic nerve of diabetic rats were decreased by islet transplantation. Improved glycemic control of diabetic patients may be expected to decrease protein gly...

- by Paul Thornalley
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- Cognitive Science, Oxidative Stress, Neurobiology, Antioxidants

Human Leukocyte Antigen (HLA) antibodies posttransplant have been associated with an increased risk of early graft failure in kidney transplants. Whether this also applies to islet transplantation is not clear. To achieve insulin independence after islet transplants multiple donor infusions may be required. Hence, islet transplant recipients are at risk of sensitization after transplantation. Islet transplant recipients were screened for HLA antibodies posttransplant by flow-based methods. A total of 98 patients were studied. Twenty-nine patients (31%) developed de novo donor specific antibodies (DSA) posttransplant. Twenty-three patients developed DSA while on immunosuppression (IS). Among recipients who have discontinued IS, 10/14 (71%) are broadly sensitized with panel reactive antibody (PRA) ≥50%. The risk of becoming broadly sensitized after transplant was 11/69 (16%) if the recipient was unsensitized prior to transplant. The majority of these antibodies have persisted over time. Appearance of HLA antibodies posttransplant is concerning, and the incidence rises abruptly in subjects weaned completely from IS. This may negatively impact the ability of these individuals to undergo further islet, pancreas or kidney transplantation and should be discussed upfront during evaluation of candidates for islet transplantation.

- by abdul salam
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- Islet Transplantation, Immunization, American, T lymphocytes

A melhor compreensão das causas da instabilidade dos níveis da glicemia em pacientes com diabetes melito tipo 1 (DMT1) e a disponibilidade de novas alternativas para enfrentá-la com sucesso, como a bomba de infusão contínua de insulina e os análogos das insulinas, tornaram relevante o questionamento sobre a existência do diabetes hiperlábil como uma entidade bem como a necessidade de defini-lo. O presente artigo pretendeu descrever o conceito de diabetes hiperlábil à luz dos novos avanços na terapia do DMT1 e propor critérios objetivos para a quantificação da labilidade da glicemia. Arq Bras Endocrinol Metab. 2009;53(4):466-9.

The long-term function of human pancreatic islet grafts may depend on the neogenesis of beta cells from epithelial precursors within the grafted tissue. We have developed an in vitro model for human islet neogenesis. In this study, we have investigated the morphological signs of maturation in cultivated human islet buds (CHIBs) before and after transplantation. Clusterin is a molecule associated with beta-cell differentiation in rodents. In adult human islets, clusterin expression was located only in alpha-and PP-cells, but in CHIBs and human fetal islets, it was distributed in all four types of endocrine cells. Some immature endocrine cells in the CHIBs co-expressed insulin and glucagon. After transplantation, CHIBs became mature with one type of hormone per endocrine cell, and clusterin expression became restricted in alpha-cells. Cells co-expressing endocrine markers and cytokeratin 19, as a sign of ductal to endocrine cell transition, were frequently detected in both fresh islets and CHIBs after transplantation. We conclude that clusterin may be involved in the development of islets, and the in vitro-derived islets become mature after transplantation into nude mice. Ductal cell differentiation into endocrine cells may be an important factor in sustaining the long-term function of islet transplants.

- by Timo Otonkoski
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- Biological Sciences, Cell Differentiation, Molecular and cellular biology, Insulin

Albino Oxford rats made diabetic with 75 mg/kg streptozotocin were intraperitoneally transplanted with 2500-2900 alginate-polylysine microencapsulated Lewis islets (n = 9, total islet tissue volume 8.0-11.0 btl), or a similar volume of non-encapsulated Lewis islets (n = 5). All rats with microencapsulated islets became normoglycaemic, and remained normoglycaemic for 5-16 weeks. In rats with non-encapsulated islet grafts, only a temporary decrease in blood glucose was observed, and all were again severely hyperglycaemic at 1 week after implantation. At 5-6 weeks after transplantation, glucose tolerance in rats with microencapsulated islets was tested by intravenous glucose infusion (10mg/min over 20min) and test meal administration (n = 4). During glucose infusion, maximum glucose levels were 13.0_+0.4mmol/1 in rats with microcapsules and 8.9 + 0.4 mmol/1 in healthy control rats (p < 0.01). Concomi-tant maximum plasma insulin levels were 215 _+ 17 pmol/1 in rats with microcapsules and 715_+85pmol/1 in controls (p < 0.001). After the test meal, maximum blood glucose was 10.6_+0.9mmol/1 in rats with microcapsules and 6.2+ 0.1 mmol/1 in controls (p < 0.001), with concomitant maximum plasma insulin levels of 247_+11pmol/1 and 586+ 59 pmol/1, respectively (p < 0.001). In conclusion, although the glucose tolerance is impaired and plasma insulin responses to intravenous glucose-load and test-meal are reduced, the alginate-polylysine membrane does provide adequate immunoisolation for the prolongation of allograft survival, resulting in prolonged normoglycaemia in streptozotocin diabetic rats.

- by Wilbert Fritschy
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- Blood Glucose, Insulin, Islet Transplantation, Eating

In type I diabetes mellitus, islet transplantation provides a moment-to-moment fine regulation of insulin. Success rates vary widely, however, necessitating suitable methods to monitor islet delivery, engraftment and survival. Here magnetic resonance-trackable magnetocapsules have been used simultaneously to immunoprotect pancreatic b-cells and to monitor, non-invasively in real-time, hepatic delivery and engraftment by magnetic resonance imaging (MRI). Magnetocapsules were detected as single capsules with an altered magnetic resonance appearance on capsule rupture. Magnetocapsules were functional in vivo because mouse b-cells restored normal glycemia in streptozotocin-induced diabetic mice and human islets induced sustained C-peptide levels in swine. In this large-animal model, magnetocapsules could be precisely targeted for infusion by using magnetic resonance fluoroscopy, whereas MRI facilitated monitoring of liver engraftment over time. These findings are directly applicable to ongoing improvements in islet cell transplantation for human diabetes, particularly because our magnetocapsules comprise clinically applicable materials.

- by Wesley Gilson and +1
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- Magnetic Resonance Imaging, Mice, Islet Transplantation, Magnetic Resonance

Transplantation of pancreatic islets of Langerhans (islets) is a promising method to treat insulin-dependent diabetes mellitus. Control of complement activation is necessary to improve graft survival in alloislet and xenoislet transplantation. In this study, human soluble complement receptor 1 (sCR1) was immobilized on the islet cell surface through poly(ethylene glycol)-conjugated phospholipid (PEG-lipid) without loss of islet cell viability or insulin secretion ability. sCR1 on islets effectively inhibits complement activation and protects islets against attack by xenoreactive antibodies and complement. This method will be an efficient means to control early islet loss in clinical islet transplantation and realize xenoislet transplantation in the future.

- by NGUYEN CONG LUAN
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- Chemistry, Biomaterials, Complement activation, Phospholipids

Studies involving the transplantation of human islets in Type I diabetics have been of significant value both in documenting the potential importance of islet transplantation as a therapeutic modality, and in defining some of the problems which must be overcome before this approach can be used in large numbers of patients. The currently limited supply of adult human pancreatic glands, and the fact that chronic immunosuppression is required to successfully transplant islets into patients, indicate that techniques must be further developed and refined for alloand xenografting of isolated islets from human and animal sources to diabetic patients. An increasing body of evidence using microencapsulation techniques strongly suggests that this will be achieved during the next few years. Data from our laboratory in rodents and dogs indicate that these systems can function for extended periods of time. In one study, insulin independence was achieved in spontaneously diabetic dogs by islet microencapsulation inside uncoated alginate gel spheres (M r exclusion >600 kD). No synthetic materials or membrane coatings were employed in this study. Spheres containing canine islets were implanted into the peritoneum of 4 diabetic dogs. The animals received low-dose CsA (levels below readable limits by HPLC at 3 weeks). Implantation of these spheres completely supplanted exogenous insulin therapy in the dogs for 60 to >175 days. Blood glucose concentration averaged 122±4 mg/dl for these animals during the first 2 months. The glycosylated hemoglobin (Hb AIC ) levels during this period dropped from 6.7±0.5% to 4.2±0.2% (P<0.001). IVGTT K-values at 1 and 2 months postimplantation were 1.6±0.1 (P<0.002) and 1.9±0.1 (P<0.001), respectively compared with 0.71±0.3 before implantation. In a second group of studies, bovine islets were immobilized inside a new type of selectively permeable "microreactor" (M r exclusion <150 kD) and implanted into the peritoneum of 33 STZ-induced diabetic rats without any immunosuppression. Diabetes was promptly reversed, and normoglycemia maintained for periods of several weeks to months. Immunohistochemical staining of microreactors recovered from these animals revealed well-granulated β-cells consistent with functionally active insulin synthesis and secretion. To test further the secretory function of the islets, some of the explanted microreactors were incubated in media containing either basal or stimulatory concentrations of glucose. The islets responded with an approximately 3-to 5-fold average increase above basal insulin secretion. These results are encouraging, and may have important implications in assessing the potential role of these microencapsulation systems as therapy for human insulin-dependent diabetes.

- by Willem Kuhtreiber
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- Molecular Medicine, Treatment, Dogs, Microencapsulation

Mesenchymal stem cells (MSC) are uniquely capable of crossing germinative layers borders (i.e. are able to differentiate towards ectoderm-, mesoderm-and endodermderived cytotypes) and are viewed as promising cells for regenerative medicine approaches in several diseases. Type I diabetes therapy should potentially benefit from such differentiated cells: the search for alternatives to organ/islet transplantation strategies via stem cells differentiation is an ongoing task, significant goals having been achieved in most experimental settings (e.g. insulin production and euglycaemia restoration), though caution is still needed to ensure safe and durable effects in vivo. MSC are obtainable in high numbers via ex vivo culture and can be differentiated towards insulinproducing cells (IPC). Moreover, recent reports evidenced that MSC possess immunomodulatory activities (acting on both innate and acquired immunity effectors) which should result in a reduction of the immunogenicity of transplanted cells, thus limiting rejection. Moreover it has been proposed that MSC administration should be used to attenuate the autoimmune processes which lead to the destruction of beta cells. This review illustrates the recent advances made in differentiating human MSC to IPC. In particular, we compare the effectiveness of the differentiation protocols applied, the markers and functional assays used to characterize differentiated progeny, and the in vivo controls. We further speculate on how MSC derived from Wharton's jelly of human umbilical cord may represent a more promising regenerative medicine tool, as recently demonstrated for endoderm-derived organs (as liver) in human subjects, also considering their peculiar immunomodulatory features compared to other MSC populations.

- by Antonino di Stefano
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- Technology, Regeneration, Adult Stem Cells, Stem Cell

This study investigates the potential of bone marrow (BM-MSCs) versus adipose mesenchymal stem cells (AMSCs) to potentiate the oxygenation of encapsulated islets in a subcutaneous bioartificial pancreas. Oxygen pressures (inside subcutaneous implants) were followed in vivo (by electronic paramagnetic resonance) in non-diabetic/diabetic rats transplanted with encapsulated porcine islets or empty implants up to 4 weeks post-transplantation. After graft explantation, neoangiogenesis surrounding the implants was assessed by histomorphometry. Angiogenic properties of BM-MSCs and AMSCs were first assessed in vitro by incubation of the cells in hypoxia chambers, under normoxic/hypoxic and hypo-/hyperglycemic conditions, followed by quantification of vascular endothelial growth factor (VEGF) release. Second, the in vivo aspect was studied by subcutaneous transplantation of encapsulated BM-MSCs and AMSCs in diabetic rats and assessment of the cells' angiogenic properties as described above. Diabetic state and islet encapsulation induced a significant decrease of oxygenation of the subcutaneous implant and an increased number of cells expressing VEGF. AMSCs demonstrated a significantly higher VEGF secretion than BM-MSCs in vitro. In vivo, AMSCs improved the implant's oxygenation and vascularization. Diabetes and islet encapsulation significantly reduced the oxygenation of a subcutaneous bioartificial pancreas. AMSCs can improve oxygenation by VEGF release in hypoxia and hyperglycemia states.

- by Bénédicte Jordan
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- Biomaterials, Flow Cytometry, Stem Cell, Multidisciplinary

on antiviral prophylaxis, morbidity/mortality, donor selection and hospital stay. We evaluated CMV prevalence in our islet transplant candidates (ITC) in comparison with organ donors. We correlated the CMV serological status of our ITC with serology for Epstein-Barr virus and Parvovirus B19, auto-antibodies, patient's age, age at DM onset, duration of DM, gender, race, ABO group, HLA haplotype and C-peptide levels. Cytomegalovirus transmission after islet transplant using the Edmonton regimen was also evaluated. Cytomegalovirus seropositivity varied according to patient group, age, gender and race. Type 1 DM patients had reduced odds of CMV seropositivity when compared with organ donors. In all groups studied, older patients, females, and non-Caucasians were more likely to be CMV seropositive. In addition, no CMV reactivation, infection or disease was observed among our transplanted patients using this steroid-free regimen even after donor/recipient CMV mismatch.

- by Muhammad Hafiz
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- Adolescent, Islet Transplantation, Cytomegalovirus, Regression Analysis

Alginate-polylysine microencapsulation has been proposed as a method of protecting transplanted pancreatic islets against immunological attack. Using this technique, prolonged graft survival has been reported in some diabetic animals. However, in the spontaneously diabetic insulindependent BB/E rat we found that intraperitoneal implantation of microencapsulated islets had only a short-lived effect on hyperglycaemia. Recovered microcapsules (both those implanted empty and containing islets) were surrounded by a foreign body type cellular overgrowth and, although many capsules remained intact, encapsulated islets were observed to be disintegrating. Loss of Beta cells was confirmed by immunohistology. Various polymer materials used in artificial membranes have been shown to activate macrophages involved in foreign body reactions and induce synthesis of in-terleukin-lfl, a known Beta-cell toxin. Reduced secretion of insulin and progressive islet damage (indicated by a significant reduction in residual islet insulin and DNA content) were demonstrated when microencapsulated islets were incubated with interleukin-lflin vitro for 9 days. Similar effects were seen following exposure to a combination of gamma interferon and alpha tumour necrosis factor. Successful use of microencapsulation in islet transplantation depends upon the development of biocompatible membranes. The exclusion of smaller molecules, such as cytokines, which may be involved in foreign body mediated damage and microencapsulated islet graft rejection, could also be important.

- by Martin Waterfall
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- Glucose, Blood Glucose, Insulin, Plant tissue Culture Techniques

Previous studies suggest that multiple transplantations might be equally efficient to a single regimen for human adult islets. The aim of this study was to compare metabolic parameters after each of the two regimens of human fetal islet (HFI) transplantation in type 1 diabetics. In group A (single transplant, n ϭ 9), 180 Ϯ 20 ϫ 1000 HFI equivalents (IEQs) were implanted by a single IM injection; in group B (multiple transplants, n ϭ 8) islets were implanted as three consecutive injections (60 Ϯ 10 ϫ 1000 IEQs) at 7-day intervals. We analyzed the metabolic parameters on days Ϫ1, 30, 60, 90, 120, 150, and 180 after the procedure. Among the metabolic parameters, we evaluated insulin secretion capacity-ISC (C peptide, RIA), metabolic control (HbA1c, chromatography), and insulin daily dose IDD. We found that C peptide levels increased, peaking on day 90 (A: 0.38 Ϯ 0.15; B: 0.34 Ϯ 0.19 nmol/L, P ϭ NS) and then rapidly decreasing without differences, the HbA1c levels and IDD decreased in the same manner without differences between the groups. Our results demonstrate that multiple and single islet transplant regimens are equally efficient to temporarily restore a significant ISC with improvement of metabolic and clinical parameters. The results imply that the two regimens have an equal clinical value.

- by Vladimir Bumbasirevic
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- Type 2 Diabetes, Transplantation, Insulin, Glucagon

Neonatal porcine islets within alginate microcapsules transplanted intraperitoneally (IP) or within semi-permeable macrocapsules (TheraCyte) and transplanted subcutaneously (SC) survive and reverse diabetes for up to 16 weeks in diabetic autoimmune nonobese diabetic (NOD) mice. The islets in microcapsules transplanted IP into nondiabetic cynomolgus monkeys survived for 8 weeks. Similar results were shown with islets transplanted in TheraCytes. Neither species showed adverse effects or evidence of infection with porcine endogenous retroviruses or other endemic pig viruses. Proof of principle is illustrated for successful xenotransplantation in humans.

- by Giuseppina Basta
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- Transplantation, Mice, Islet Transplantation, Swine

Mesenchymal stem cells (MSC) are multipotent non-haematopoietic progenitors, which have been explored as a promising treatment in tissue regeneration. Although their immunomodulatory properties are not yet completely understood, their low immunogenic potential together with their complex and profound effects on immune responses can be used as a therapeutic tool not only for regenerative medicine, but also for the treatment of variate autoimmune pathologies, such as graftversus-host (GVH) disease after transplantation. Several severe refractory autoimmune diseases as well as the prevention of organ rejection Phase I-II clinical trials are testing the therapeutic efficiency of MSCs as such or in several autoimmune pathologies such as GVH disease, and systemic sclerosis. Type 1 Diabetes is characterised by T-cell mediated autoimmune destruction of pancreatic β cells. While insulin replacement represent the current therapy of this disease, the metabolic control is still difficult and limited by the fact that exogenous insulin cannot mimic exactly the physiology of insulin secretion. Pancreatic or pancreatic islet transplantation can provide exogenous insulin independence, but the scarce availability of transplantation material and the thrombotic complications associated, limitate significantly the benefits and the success of the procedure. In this context, stem cell therapy based on generation of insulin producing cells (IPCs) from MSC, might represent an attractive perspective. In this review we provide a brief characterisation of the immunomodulatory effects promoted by MSCs, and present the state of experimental evidence ( in vitro as in vivo) related to the effects of the transplantation of mesenchymal stem cells in diabetes.

- by Lavinia Vija
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- Immune response, Diabetes, Stem cell Therapy, Cell Differentiation

The activation of c-jun N-terminal kinase (JNK) in pancreatic islets is associated with impaired function and viability, and JNK inhibitory peptides (JNKIs) are cytoprotective. In particular, L-isoforms of JNKIs were shown to improve islets viability, while the D-retroinverso isoform of JNKI (RI-JNKI), with a higher therapeutic potential due to longer half-life, has not been studied. We compared the cytoprotective properties of L-JNKI and RI-JNKI. Treatment of murine islets with L-JNKI resulted in preservation of islet equivalents and greater percentage of viable b-cells in culture. In contrast, RI-JNKI was not protective. We found that L-JNKI but not RI-JNKI prevents endogenous c-jun phosphorylation in insulinoma cells. Moreover, RI-JNKI induced islet cells necrosis and activates the p-38 kinase. In conclusion, L-JNKI directly affects b-cells and ameliorates islet viability and function, while RI-JNKI has toxic effects, limiting its biological application to islet cell biology.

- by Antonello Pileggi
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- Cell Biology, Apoptosis, Mice, Islet Transplantation

Islet cell transplantation has recently emerged as one of the most promising therapeutic approaches to improving glycometabolic control in diabetic patients and, in many cases, achieving insulin independence. Unfortunately, many persistent flaws still prevent islet transplantation from becoming the gold standard treatment for type 1 diabetic patients. We review the state of the art of islet transplantation, outcomes, immunosuppression and-most important-the impact on patients' survival and long-term diabetic complications and eventual alternative options. Finally, we review the many problems in the field and the challenges to islet survival after transplantation. The rate of insulin independence 1 year after islet cell transplantation has significantly improved in recent years (60% at 1 year posttransplantation compared with 15% previously). Recent data indicate that restoration of insulin secretion after islet cell transplantation is associated with an improvement in quality of life, with a reduction in hypoglycemic episodes and potentially with a reduction in long-term diabetic complications. Once clinical islet transplantation has been successfully established, this treatment could even be offered to diabetic patients long before the onset of diabetic complications.

- by Paolo Fiorina
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- Quality of life, Treatment Outcome, Insulin, Islet Transplantation

Insulin represents a life-saving therapy for patients with type 1 diabetes but, despite appropriate treatment, it prevents only partially long-term diabetic complications, while generating fatal hypoglycemic episodes. Islet transplantation gained attention because of its safety, effectiveness, and minimal invasiveness; however it remains a procedure reserved for a selected group of patients. The introduction of the Edmonton Protocol in 2000, based on a newly designed steroid-free immunosuppressive protocol, revamped the course of islet transplantation. The main goal of islet transplantation remains insulin independence, although the effect of islet transplantation can be more comprehensively evaluated in terms of frequency of hypoglycemic episodes and impact on diabetic complications and quality of life. Islet transplantation was shown to have positive consequences on cardiovascular, renal, neurologic, and ocular diabetic complications. The proof of concept for cellular replacement therapy in diabetes has been established with islet transplantation, it only needs to be improved and rendered widely available.

- by Jane Holmes-Walker
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- Islet Transplantation

sure of islets to hyperglycemia results in beta cell loss (Biarnes et al., 2002 ; Gray et al., 1989). In this animal study we attempted to reassess the role of hyperglycemic stress in isogeneic pancreatic islet transplantation. Material and Methods & Animals Male inbred DA (RT1 a), PVG (RT1 c) and Lewis (RT1 Ј) rats (approximately 200 grams) were used as islet donors and recipients. Islet preparation, culture and transplantation Pancreatic islets were prepared by collagenase digestion and hand picking technique as previously described (Rajotte et al., 1984). Varying numbers of islets were transplanted beneath the kidney capsule of the recipients. Fresh islets were

- by Evangelos Athanasiou
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- Animal Studies, Hyperglycemia, Islet Transplantation, Clinical Sciences

Covalent attachment of polymers to cells and tissues could be used to solve a variety of problems associated with cellular therapies. Insulin-dependent diabetes mellitus is a disease resulting from the autoimmune destruction of the b cells of the islets of Langerhans in the pancreas. Transplantation of islets into diabetic patients is an attractive form of treatment, provided that the islets could be protected from the host's immune system to prevent graft rejection, and smaller numbers of islets transplanted in smaller volumes could be sufficient to reverse diabetes. Therefore, a need exists to develop islet encapsulation strategies that minimize transplant volume. In this study, we demonstrate the formation of nano-thin, poly(ethylene glycol) (PEG)-rich functional conformal coatings on individual islets via layer-by-layer assembly technique. The surface of the islets is modified with biotin-PEG-N-hydroxysuccinimide (NHS), and the islets are further covered by streptavidin (SA) and biotin-PEG-peptide conjugates using the layer-by-layer method. An insulinotropic ligand, glucagon-like peptide-1 (GLP-1), is conjugated to biotin-PEG-NHS. The insulinotropic effect of GLP-1 is investigated through layer-by-layer encapsulation of islets using the biotin-PEG-GLP-1 conjugate. The effect of islet surface modification using the biotin-PEG-GLP-1 conjugate on insulin secretion in response to glucose challenge is compared via static incubation and dynamic perifusion assays. The results show that islets coated with the functional PEG conjugate are capable of secreting more insulin in response to high glucose levels compared to control islets. Finally, the presence of SA is confirmed by indirect fluorescent staining with SA-Cy3, and the presence of PEGpeptide on the surface of the islets after treatment with biotin-PEG-GLP-1 is confirmed by indirect fluorescent staining with biotin-PEG-fluorescein isothiocyanate (FITC) and separately with an anti-GLP-1 antibody. This work demonstrates the feasibility of treating pancreatic islets with reactive polymeric segments and provides the foundation for a novel means of potential immunoisolation. With this technique, it may be possible to encapsulate and/or modify islets before portal vein transplantation and reduce transplantation volume significantly, and promote islet viability and insulin secretion due to the presence of insulinotropic peptides on the islet surface. Layer-by-layer self-assembly of PEG-GLP-1 offers a unique approach to islet encapsulation to stimulate insulin secretion in response to high glucose levels.

- by Michael Millis
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- Biomedical Engineering, Glucose, Insulin, Insulin Secretion

Immune rejection and scarcity of donor tissues are the restrictions of islets transplantation. In this study, the cytoprotection of chitosan hydrogels in xenogeneic islet transplantation was demonstrated. Wistar rat islets encapsulated in chitosan hydrogels were performed glucose challenge test and live/dead cell staining in vitro. Islets/chitosan hydrogels were transplanted into the renal subcapsular space of diabetic C57BL/6 mice. Non-fasting blood glucose level (NFBG), body weight, intraperitoneal glucose tolerance test (IPGTT), and glucose disappearance rate were determined perioperatively. The serum insulin level was analyzed, and the kidney transplanted with islets/chitosan hydrogels were retrieved for histological examination after sacrifice. The present results showed that islets encapsulated in chitosan hydrogels secreted insulin in response to the glucose stimulation as naked islets with higher cell survival. The NFBG of diabetic mice transplanted with islets/chitosan hydrogels decreased from 487±46 to 148±32 at one day postoperation and maintained in the range of 201±36 mg/dl for four weeks with an increase in body weight. IPGTT showed the glucose disappearance rate of mice transplanted with islets/chitosan hydrogels was significant faster than that of mice transplanted with naked islets; the serum insulin level increased from 0.29±0.06 to 1.69±0.65 μg/dl postoperatively. Histological examination revealed that the islets successfully engrafted at renal subcapsular space with positive insulin staining. The immunostain was negative for neither the T-cell lineages nor the monocyte/macrophages. This study indicates that the chitosan hydrogels deliver and protect encapsulated islets successfully in xenotransplantation.

- by Feng-huei Lin
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- Chitosan, Hydrogels, Blood Glucose, Insulin

Poly-L-Lysine (PLL) is the most widely used biomaterial for providing perm-selectivity in alginate microcapsules for islet transplantation. We had previously reported that Poly-L-Ornithine (PLO) is less immunogenic than PLL, and in the present study, we have compared the physical characteristics of PLO-and PLL-coated hollow alginate microcapsules. Microspheres made with 1.5% alginate were divided into 2 groups that were first coated with either 0.1% PLO or PLL, followed by a second coating with 0.25% alginate. After liquefaction of the inner alginate core with sodium citrate, the microcapsules were washed with saline and used for experiments. Pore size exclusion studies were performed with FITC-labeled lectins incubated with encapsulated pig islets followed by examination for fluorescence activity. Mechanical strength was assessed by an osmotic pressure test and by 36 h of mechanical agitation of microcapsules with inert soda lime beads. The pore size exclusion limit of microcapsules after 20 min of coating was significantly smaller with PLO. While the mean7SEM diameter of PLL-coated microcapsules increased from 718717 to 821717 mm (po0:05) during 14 days incubation at 37 1C, the PLO group did not change in size. Also, PLL group had a higher percentage of broken capsules (52.774.9%) compared to 3.172.05% for PLO capsules (po0:0001; n ¼ 6). We conclude that PLOcoated alginate microcapsules are mechanically stronger and provide better perm-selectivity than PLL-coated microcapsules.

- by Emmanuel Opara
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- Biomaterials, Multidisciplinary, Elasticity, Microencapsulation

Insulin-dependent diabetes mellitus is an autoimmune disease that causes a progressive destruction of the pancreatic beta cells. As a result, the patient requires exogenous insulin to maintain normal blood glucose levels. Both the pancreas and the islets of Langerhans have been transplanted successfully in humans and in animal models, resulting in full normalization of glucose homeostasis. However, insulin independence, transient or persistent, was documented in only a small fraction of cases until recently. The chronic immunosuppression required to avoid immunological rejection appears to be toxic to the islets and adds the risk of lymphoproliferative disease reported earlier. For islet transplantation to become the method of choice, it is essential first to identify islet-friendly immunosuppressive regimens and/or to develop methods that induce donor-specific tolerance and improve islet isolation and transplantation protocols. Indeed, researchers have already successfully allografted islets in the presence of nonsteroidal immunosuppression in a process known as the Edmonton protocol. An alternative method, gene therapy, could replace these other methods and better meet the insulin requirement of an individual without requiring pancreatic or islet transplantation. This alternative, however, requires animal models to develop and test clinical protocols and to demonstrate the feasibility of preclinical trials. Nonhuman primates are ideally suited to achieve these goals. The efforts toward developing a nonhuman primate diabetic model with demonstrable insulin dependence are discussed and include pancreatic and islet transplant trials to reverse the diabetic state and achieve insulin independence. Also described are the various protocols that have been tested in primates to circumvent immunosuppression by using tolerance induction strategies in lieu of immunosuppression, thus exploring the field of donorspecific tolerance that extends beyond islet transplantation.

- by Lakshmi Gaur
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- Gene Therapy, Type 2 Diabetes, Biological Sciences, Blood Glucose

The aim of any pancreatic islet isolation is obtaining pure, viable and functional pancreatic islets, either for in vitro or in vivo purposes. The islets of Langerhans are complex microorgans with the important role of regulating glucose homeostasis. Imbalances in glucose homeostasis lead to diabetes, which is defined by the American Diabetes Association as a " group of metabolic diseases characterized by hyperglycemia resulting from defects in insulin secretion, insulin action or both " (American Diabetes Association 2011). Currently, the rising demand of human islets is provoking a shortage of this tissue, limiting research and clinical practice on this field. In this scenario, it is essential to investigate and improve islet isolation procedures in animal models, while keeping in mind the anatomical and functional differences between species. This chapter discusses the main aspects of mouse islet isolation research, highlighting the critical factors and shortcomings to take into account for the selection and/or optimization of a mouse islet isolation protocol.

- by Richard Allen
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- Transplantation, Islet Transplantation, Immunosuppression, Pancreas Transplantation

Substantial amounts of nonendocrine cells are implanted as part of human islet grafts, and a possible influence of nonendocrine cells on clinical islet transplantation outcome has been postulated. There are currently no product release criteria specific for nonendocrine cells due to lack of available methods. The aims of this study were to develop a method for the evaluation of pancreatic ductal cells (PDCs) for clinical islet transplantation and to characterize them regarding phenotype, viability, and function. We assessed 161 human islet preparations using laser scanning cytometry (LSC/iCys) for phenotypic analysis of nonendocrine cells and flow cytometry (FACS) for PDC viability. PDC and b-cells obtained from different density fractions during the islet cell purification were compared in terms of viability. Furthermore, we examined PDC ability to produce proinflammatory cytokines/chemokines, vascular endothelial growth factor (VEGF) and tissue factor (TF) relevant to islet graft ...

- by Hirohito Ichii
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- Flow Cytometry, Islet Transplantation, Laser Scanning, Development Strategy

OBJECTIVE -The ␤-score is a highly regarded approach to the assessment of transplant functionality. Our aim was to develop an index of ␤-cell function that hinges on the pillars of the ␤-score (daily insulin requirement and A1C), has a... more

- by Lorenzo Luzi
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- Insulin, Islet Transplantation, Reproducibility of Results, Indexation

Islet transplantation is an established therapeutic procedure in which islets isolated from pancreas of cadaveric organ donors are transplanted into the portal vein of a subset of type 1 diabetic patients with complicated glycemic control. Over the last eight years, more than 850 islet transplants have been performed in more than 30 international transplant centers according to the International Islet Transplant Registry. Islet transplantation is being performed by normothermic perfusion, a minimally invasive procedure with fewer potential complications than full pancreas transplantation [1]. Clinical islet transplantation achieves insulin independence for up to 5 years post-transplant and provides patients with a stable glycemic control and a reduction of hypoglycemic events. Further, patients that have been transplanted and are back on insulin remain c-peptide positive and present an amelioration of glycated hemoglobin and a decrease in the progression of vascular complications.

- by Enliven: Surgery and Transplantation and +1
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- Orthopedic Surgery, Surgery, Plastic Surgery, Kidney transplantation

Canadian surgical contributions to the field of islet transplantation have a rich heritage and a promising future. In this article, some seminal Canadian contributions to this field are reviewed, including contributions at the basic... more

- by Xiaojie Wang
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- Canada, Islet Transplantation, Clinical Sciences, Rats

- by Seda Kizilel
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- Biomedical Engineering, Tissue Engineering, Fluorescence Microscopy, Self Assembly
- by Henry Randall
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- Liver, Islet Transplantation, Clinical Sciences, Transplant

Islet isolation exposes the islet to a variety of cellular stresses and disrupts the cell-matrix relationship--events known to be associated with apoptosis. The purpose of this study was to determine whether islet isolation leads invariably to islet cell death and to specify the mechanisms involved. Canine islets were isolated using Liberase CI and purified using a centrifuge. Islets were sampled for up to 5 days in culture and analyzed by routine histology, electron microscopy, immunocytochemistry, and reticulin staining for basement membrane. Apoptosis was assessed by cell death enzyme-linked immunosorbent assay and terminal deoxynucleotidyl transferase-mediated decoxyuridine triphosphate nick and labeling (TUNEL) assay. Activation of the prosurvival ERK1/2 and proapoptotic p38 and JNK were determined by immunoblotting. Immediately after isolation, the peri-insular basement membrane was absent, and integrin-alpha 5 expression diminished. DNA fragmentation rose from 2.5 +/- 1.8 (ar...

- by Dusica Maysinger
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- Surgery, Electron Microscopy, Apoptosis, Cell separation

Aims/hypothesis Islet transplantation is a promising treatment for type 1 diabetes but is hampered by a shortage of donor human tissue and early failure. Research on islet cell transplantation includes finding new sources of cells and immunoisolation to protect from immune assault and tumourigenic potential. Small islet cell aggregates were studied to determine if their survival and function were superior to intact islets within microcapsules because of reduced oxygen transport limitation and inflammatory mediators. Methods Islet cell aggregates were generated by dispersing rat islets into single cells and allowing them to re-aggregate in culture. Rat islets and islet cell aggregates were encapsulated in barium alginate capsules and studied when cultured in low (0.5% or 2%) or normal (20%) oxygen, or transplanted into mice.

- by J. Hollister-Lock and +1
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- Cell therapy, Mice, Islet Transplantation, Cell Transplantation

Background-Islet transplantation (IT) can restore normoglycemia to patients with unstable type 1 diabetes (T1DM) but long term insulin independence is usually not sustained. Identification of predictor(s) of islet allograft dysfunction... more

- by Raquel Faradji
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- Early Intervention, Transplantation, Blood Glucose, Insulin
- by Marcela Brissova
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- Transplantation, Mice, Islet Transplantation, Three Dimensional Imaging

- by abuhayat monnnsur
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- Immune response, Diabetes, Stem cell Therapy, Cell Differentiation

Autologous islet cell transplantation after near-total or total pancreatic resection can alleviate pain in patients with severe chronic pancreatitis and preserve endocrine function. From February 2000 to February 2003, a total of 22 patients, whose median age was 38 years, underwent pancreatectomy and autologous islet cell transplantation. Postoperative complications, metabolic studies, insulin usage, pain scores, and quality of life were recorded for all of these patients. The average number of islet cells harvested was 245,457 (range 20,850 to 607,466). Operative data revealed a mean estimated blood loss of 635 ml, an average operative time of 9 hours, and a mean length of hospital stay of 15 days. Sixty-eight percent of the patients had either a minor or major complication. Major complications included acute respiratory distress syndrome (n ϭ 2), intra-abdominal abscess (n ϭ 1), and pulmonary embolism (n ϭ 1). There were no deaths in our series. All patients demonstrated C-peptide and insulin production indicating graft function. Forty-one percent are insulin independent, and 27% required minimal amount of insulin or a sliding scale. All patients had preoperative pain and had been taking opioid analgesics; 82% no longer required analgesics postoperatively. Pancreatectomy with autologous islet cell transplantation can alleviate pain for patients with chronic pancreatitis and preserve endocrine function. ( J GASTROINTEST SURG 2003;7:978-989) Ć

- by Horacio Rodriguez
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- Pain, Quality of life, Treatment Outcome, Pancreatitis