Point: steady progress and current challenges in clinical islet transplantation

Delivery of therapeutic agents and cells to pancreatic islets: Towards a new era in the treatment of diabetes

Pancreatic islet cells, and in particular insulin-producing beta cells, are centrally involved in the pathogenesis of diabetes mellitus. These cells are of paramount importance for the endocrine control of glycemia and glucose metabolism. In Type 1 Diabetes, islet beta cells are lost due to an autoimmune attack. In Type 2 Diabetes, beta cells become dysfunctional and insufficient to counterbalance insulin resistance in peripheral tissues. Therapeutic agents have been developed to support the function of islet cells, as well as to inhibit deleterious immune responses and inflammation. Most of these agents have undesired effects due to systemic administration and off-target effects. Typically, only a small fraction of therapeutic agent reaches the desired niche in the pancreas. Because islets and their beta cells are scattered throughout the pancreas, access to the niche is limited. Targeted delivery to pancreatic islets could dramatically improve the therapeutic effect, lower the dose requirements, and lower the side effects of agents administered systemically. Targeted delivery is especially relevant for those therapeutics for which the manufacturing is difficult and costly, such as cells, exosomes, and microvesicles. Along with therapeutic agents, imaging reagents intended to quantify the beta cell mass could benefit from targeted delivery. Several methods have been developed to improve the delivery of agents to pancreatic islets. Intra-arterial administration in the pancreatic artery is a promising surgical approach, but it has inherent risks. Targeted delivery strategies have been developed based on ligands for cell surface molecules specific to islet cells or inflamed vascular endothelial cells. Delivery methods range from nanocarriers and vectors to deliver pharmacological agents to viral and non-viral vectors for the delivery of genetic constructs. Several strategies demonstrated enhanced therapeutic effects in diabetes with lower amounts of therapeutic agents and lower off-target side effects. Microvesicles, exosomes, polymer-based vectors, and nanocarriers are gaining popularity for targeted delivery. Notably, liposomes, lipid-assisted nanocarriers, and cationic polymers can be bioengineered to be immune-evasive, and their advantages to transport cargos into target cells make them appealing for pancreatic islet-targeted delivery. Viral vectors have become prominent tools for targeted gene delivery. In this review, we discuss the latest strategies for targeted delivery of therapeutic agents and imaging reagents to pancreatic islet cells.

Extracellular HMGB1 exacerbates autoimmune progression and recurrence of type 1 diabetes by impairing regulatory T cell stability

AIMS/HYPOTHESIS

High-mobility group box 1 (HMGB1), an evolutionarily conserved chromosomal protein, was rediscovered to be a 'danger signal' (alarmin) that alerts the immune system once released extracellularly. Therefore, it has been recognised contributing to the pathogenesis of autoimmune diabetes, but its exact impact on the initiation and progression of type 1 diabetes, as well as the related molecular mechanisms, are yet to be fully characterised.

METHODS

In the current report, we employed NOD mice as a model to dissect the impact of blocking HMGB1 on the prevention, treatment and reversal of type 1 diabetes. To study the mechanism involved, we extensively examined the characteristics of regulatory T cells (Tregs) and their related signalling pathways upon HMGB1 stimulation. Furthermore, we investigated the relevance of our data to human autoimmune diabetes.

RESULTS

Neutralising HMGB1 both delayed diabetes onset and, of particular relevance, reversed diabetes in 13 out of 20 new-onset diabetic NOD mice. Consistently, blockade of HMGB1 prevented islet isografts from autoimmune attack in diabetic NOD mice. Using transgenic reporter mice that carry a Foxp3 lineage reporter construct, we found that administration of HMGB1 impairs Treg stability and function. Mechanistic studies revealed that HMGB1 activates receptor for AGE (RAGE) and toll-like receptor (TLR)4 to enhance phosphatidylinositol 3-kinase (PI3K)-Akt-mechanistic target of rapamycin (mTOR) signalling, thereby impairing Treg stability and functionality. Indeed, high circulating levels of HMGB1 in human participants with type 1 diabetes contribute to Treg instability, suggesting that blockade of HMGB1 could be an effective therapy against type 1 diabetes in clinical settings.

CONCLUSIONS/INTERPRETATION

The present data support the possibility that HMGB1 could be a viable therapeutic target to prevent the initiation, progression and recurrence of autoimmunity in the setting of type 1 diabetes.

Use of additives, scaffolds and extracellular matrix components for improvement of human pancreatic islet outcomes in vitro: A systematic review

Pancreatic islet transplantation is an established treatment to restore insulin independence in type 1 diabetic patients. Its success rates have increased lately based on improvements in immunosuppressive therapies and on islet isolation and culture. It is known that the quality and quantity of viable transplanted islets are crucial for the achievement of insulin independence and some studies have shown that a significant number of islets are lost during culture time. Thus, in an effort to improve islet yield during culture period, researchers have tested a variety of additives in culture media as well as alternative culture devices, such as scaffolds. However, due to the use of different categories of additives or devices, it is difficult to draw a conclusion on the benefits of these strategies. Therefore, the aim of this systematic review was to summarize the results of studies that described the use of medium additives, scaffolds or extracellular matrix (ECM) components during human pancreatic islets culture. PubMed and Embase repositories were searched. Of 5083 articles retrieved, a total of 37 articles fulfilled the eligibility criteria and were included in the review. After data extraction, articles were grouped as follows: 1) "antiapoptotic/anti-inflammatory/antioxidant," 2) "hormone," 3) "sulphonylureas," 4) "serum supplements," and 5) "scaffolds or ECM components." The effects of the reviewed additives, ECM or scaffolds on islet viability, apoptosis and function (glucose-stimulated insulin secretion - GSIS) were heterogeneous, making any major conclusion hard to sustain. Overall, some "antiapoptotic/anti-inflammatory/antioxidant" additives decreased apoptosis and improved GSIS. Moreover, islet culture with ECM components or scaffolds increased GSIS. More studies are needed to define the real impact of these strategies in improving islet transplantation outcomes.

Coronary artery calcium may stabilize following islet cell transplantation in patients with type 1 diabetes

Islet cell transplantation can functionally cure type 1 diabetes and also improve carotid intima-media thickness. This study provides a preliminary description of changes in coronary artery calcium following islet transplantation, and associated factors. Coronary artery calcium was measured in 14 patients with type 1 diabetes (11 had measures both pre- and post-transplant [mean 2.3 years]) in the University of Illinois at Chicago's clinical trial. Multivariable mixed-effects linear regression of repeated measures was used to quantify calcium change and determine if this change was longitudinally associated with risk/protective factors. Thirteen of the patients were female, with mean baseline age, diabetes duration, and BMI of 47.6 and 28.7 years, and 23.1, respectively. Over half (57%) had detectable coronary artery calcium pre-transplant. Minimal change (0.39 mm³ /y, P = .02) occurred in coronary artery calcium levels pre- to post-transplant. No patient met criteria for calcium progression. Coronary artery calcium was positively associated with total and small VLDL particles (P ≤ .02), statin dose (P = .02), and urine albumin-to-creatinine ratio (P = .04) and negatively associated with free fatty acids (P = .03), total HDL (P = .03), large HDL particles (P = .005), and tacrolimus dose (P = .02). Islet transplant may stabilize coronary artery calcium, with optimal management of lipids and kidney function remaining key therapeutic targets. [NCT00679041].

Repression of COUP-TFI Improves Bone Marrow-Derived Mesenchymal Stem Cell Differentiation into Insulin-Producing Cells

Identifying molecular mechanisms that regulate insulin expression in bone marrow-derived mesenchymal stem cells (bmMSCs) can provide clues on how to stimulate the differentiation of bmMSCs into insulin-producing cells (IPCs), which can be used as a therapeutic approach against type 1 diabetes (T1D). As repression factors may inhibit differentiation, the efficiency of this process is insufficient for cell transplantation. In this study, we used the mouse insulin 2 (Ins2) promoter sequence and performed a DNA affinity precipitation assay combined with liquid chromatography-mass spectrometry to identify the transcription factor, chicken ovalbumin upstream promoter transcriptional factor I (COUP-TFI). Functionally, bmMSCs were reprogrammed into IPCs via COUP-TFI suppression and MafA overexpression. The differentiated cells expressed higher levels of genes specific for islet endocrine cells, and they released C-peptide and insulin in response to glucose stimulation. Transplantation of IPCs into streptozotocin-induced diabetic mice caused a reduction in hyperglycemia. Mechanistically, COUP-TFI bound to the DR1 (direct repeats with 1 spacer) element in the Ins2 promoter, thereby negatively regulating promoter activity. Taken together, the data provide a novel mechanism by which COUP-TFI acts as a negative regulator in the Ins2 promoter. The differentiation of bmMSCs into IPCs could be improved by knockdown of COUP-TFI, which may provide a novel stem cell-based therapy for T1D.

Co-combination of islets with bone marrow mesenchymal stem cells promotes angiogenesis

BACKGROUND

Islet transplantation is a commonly therapeutic strategy for diabetes mellitus. However, avascular phase and the poor formation of blood vessels in the late period lead to islet allograft loss which contributed to inefficiency and short-acting of islet transplantation. Recently, to speed up new angiogenesis and increase the density of blood vessels around transplanted islets became the hotspot in research of islet transplantation.

METHODS

In this study, we undergone co-combination transplantation of allogeneic islet and bone marrow mesenchymal stem cells (BM-MSCs) into non-obese diabetic (NOD) mice and investigated the influence of BM-MSCs in transplanted islet function and neovascularization.

RESULTS

In mice of co-combination transplantation of islet with BM-MSCs, level of blood glucose was improved compared with only BM-MSCs transplanted mice; proliferation of islet cell was enhanced while apoptosis of islet cell was reduced; 2, 4, and 8 weeks post transplantation, peripheral vascular density of islet grafts were significantly more than the islet transplantation group alone; donor lymphocytic chimerism in graft was increased. In result of immunofluorescence analysis, we observed that BM-MSCs can migrate to transplanted islet, differentiate into vascular smooth muscle cells (VSMC) and vascular endothelial cells (VEC), and also secrete vascular endothelial growth factor (VEGF).

CONCLUSION

BM-MSCs can migrate to transplanted islet and promote neovascularization. Also, it enhanced allograft immune tolerance of islet grafts via increasing donor lymphocytic chimerism.

Isolation of Pancreatic Islets from Nonhuman Primates

Nonhuman primates (NHP) constitute a highly relevant pre-clinical animal model to develop strategies for beta cell replacement. The close phylogenetic and immunologic relationship between NHP and humans results in cross-reactivity of various biological agents with NHP cells, as well as a very similar cytoarchitecture between islets from human and NHP that is strikingly different from that observed in rodent islets. The composition and location of endocrine cells in human or NHP islets, randomly distributed and associated with blood vessels, have functional consequences and a predisposition for paracrine interactions. Furthermore, translation of approaches that proved successful in rodent models to the clinic has been limited. Consequently, data collected from NHP studies can form the basis for an IND submission to the FDA. This chapter describes in detail the key aspects for isolation of islets from NHP, from organ procurement up to assessment of islet function, comparing and emphasizing the similarities between isolation procedures for human and NHP islets.

Exendin-4 protects rat islets against loss of viability and function induced by brain death

Islet quality loss after isolation from brain-dead donors still hinders the implementation of human islet transplantation for treatment of type 1 diabetes. In this scenario, systemic inflammation elicited by donor brain death (BD) is among the main factors influencing islet viability and functional impairment. Exendin-4 is largely recognized to promote anti-inflammatory and cytoprotective effects on β-cells. Therefore, we hypothesized that administration of exendin-4 to brain-dead donors might improve islet survival and insulin secretory capabilities. Here, using a rat model of BD, we demonstrate that exendin-4 administration to the brain-dead donors increases both islet viability and glucose-stimulated insulin secretion. In this model, exendin-4 treatment produced a significant decrease in interleukin-1β expression in the pancreas. Furthermore, exendin-4 treatment increased the expression of superoxide dismutase-2 and prevented BD-induced elevation in uncoupling protein-2 expression. Such observations were accompanied by a reduction in gene expression of two genes often associated with endoplasmic reticulum (ER) stress response in freshly isolated islets from treated animals, C/EBP homologous protein and immunoglobulin heavy-chain binding protein. As ER stress response has been shown to be triggered by and to participate in cytokine-induced β-cell death, we suggest that exendin-4 might exert its beneficial effects through alleviation of pancreatic inflammation and oxidative stress, which in turn could prevent islet ER stress and β-cell death. Our findings might unveil a novel strategy to preserve islet quality from brain-dead donors. After testing in the human pancreatic islet transplantation setting, this approach might sum to the ongoing effort to achieve consistent and successful single-donor islet transplantation.

Comprehensive Analysis of a Vibrio parahaemolyticus Strain Extracellular Serine Protease VpSP37

Proteases play an important role in the field of tissue dissociation combined with regenerative medicine. During the years new sources of proteolytic enzymes have been studied including proteases from different marine organisms both eukaryotic and prokaryotic. Herein we have purified a secreted component of an isolate of Vibrio parahaemolyticus, with electrophoretic mobilities corresponding to 36 kDa, belonging to the serine proteases family. Sequencing of the N-terminus enabled the in silico identification of the whole primary structure consisting of 345 amino acid residues with a calculated molecular mass of 37.4 KDa. The purified enzyme, named VpSP37, contains a Serine protease domain between residues 35 and 276 and a canonical Trypsin/Chimotrypsin 3D structure. Functional assays were performed to evaluate protease activity of purified enzyme. Additionally the performance of VpSP37 was evaluated in tissue dissociations experiments and the use of such enzyme as a component of enzyme blend for tissue dissociation procedures is strongly recommended.

Fibrin gels engineered with pro-angiogenic growth factors promote engraftment of pancreatic islets in extrahepatic sites in mice

With a view toward reduction of graft loss, we explored pancreatic islet transplantation within fibrin matrices rendered pro-angiogenic by incorporation of minimal doses of vascular endothelial growth factor-A165 and platelet-derived growth factor-BB presented complexed to a fibrin-bound integrin-binding fibronectin domain. Engineered matrices allowed for extended release of pro-angiogenic factors and for their synergistic signaling with extracellular matrix-binding domains in the post-transplant period. Aprotinin addition delayed matrix degradation and prolonged pro-angiogenic factor availability within the graft. Both subcutaneous (SC) and epididymal fat pad (EFP) sites were evaluated. We show that in the SC site, diabetes reversal in mice transplanted with 1,000 IEQ of syngeneic islets was not observed for islets transplanted alone, while engineered matrices resulted in a diabetes median reversal time (MDRT) of 38 days. In the EFP site, the MDRT with 250 IEQ of syngeneic islets within the engineered matrices was 24 days versus 86 days for islets transplanted alone. Improved function of engineered grafts was associated with enhanced and earlier (by day 7) angiogenesis. Our findings show that by engineering the transplant site to promote prompt re-vascularization, engraftment and long-term function of islet grafts can be improved in relevant extrahepatic sites.

Human pancreatic islet transplantation: an update and description of the establishment of a pancreatic islet isolation laboratory

Type 1 diabetes mellitus (T1DM) is associated with chronic complications that lead to high morbidity and mortality rates in young adults of productive age. Intensive insulin therapy has been able to reduce the likelihood of the development of chronic diabetes complications. However, this treatment is still associated with an increased incidence of hypoglycemia. In patients with "brittle T1DM", who have severe hypoglycemia without adrenergic symptoms (hypoglycemia unawareness), islet transplantation may be a therapeutic option to restore both insulin secretion and hypoglycemic perception. The Edmonton group demonstrated that most patients who received islet infusions from more than one donor and were treated with steroid-free immunosuppressive drugs displayed a considerable decline in the initial insulin independence rates at eight years following the transplantation, but showed permanent C-peptide secretion, which facilitated glycemic control and protected patients against hypoglycemic episodes. Recently, data published by the Collaborative Islet Transplant Registry (CITR) has revealed that approximately 50% of the patients who undergo islet transplantation are insulin independent after a 3-year follow-up. Therefore, islet transplantation is able to successfully decrease plasma glucose and HbA1c levels, the occurrence of severe hypoglycemia, and improve patient quality of life. The goal of this paper was to review the human islet isolation and transplantation processes, and to describe the establishment of a human islet isolation laboratory at the Endocrine Division of the Hospital de Clínicas de Porto Alegre - Rio Grande do Sul, Brazil.

Re-engineering islet cell transplantation

We are living exciting times in the field of beta cell replacement therapies for the treatment of diabetes. While steady progress has been recorded thus far in clinical islet transplantation, novel approaches are needed to make cell-based therapies more reproducible and leading to long-lasting success. The multiple facets of diabetes impose the need for a transdisciplinary approach to attain this goal, by targeting immunity, promoting engraftment and sustained functional potency. We discuss herein the emerging technologies applied to this rapidly evolving field.

Pancreatic ductal perfusion at organ procurement enhances islet yield in human islet isolation

OBJECTIVE

Pancreas preservation is a major factor influencing the results of islet cell transplantation. This study evaluated the effects of 2 different solutions for pancreatic ductal perfusion (PDP) at organ procurement.

METHODS

Eighteen human pancreases were assigned to 3 groups: non-PDP (control), PDP with ET-Kyoto solution, and PDP with cold storage/purification stock solution. Pancreatic islets were isolated according to the modified Ricordi method.

RESULTS

No significant differences in donor characteristics, including cold ischemia time, were observed between the 3 groups. All islet isolations in the PDP groups had more than 400,000 islet equivalence in total islet yield after purification, a significant increase when compared with the control (P = 0.04 and P < 0.01). The islet quality assessments, including an in vivo diabetic nude mice assay and the response of high-mobility group box protein 1 to cytokine stimulation, also showed no significant differences. The proportion of terminal deoxynucleotidyl transferase dUTP nick-end labeling-positive cells showing apoptosis in islets in the PDP groups was significantly lower than in the control group (P < 0.05).

CONCLUSIONS

Both ET-Kyoto solution and cold storage/purification stock solution are suitable for PDP and consistently resulted in isolation success. Further studies with a larger number of pancreas donors should be done to compare the effects of the PDP solutions.

The fetal liver as cell source for the regenerative medicine of liver and pancreas

Patients affected by liver diseases and diabetes mellitus are in need for sources of new cells to enable a better transition into clinic programs of cell therapy and regenerative medicine. In this setting, fetal liver is becoming the most promising and available source of cells. Fetal liver displays unique characteristics given the possibility to isolate cell populations with a wide spectrum of endodermal differentiation and, the co-existence of endodermal and mesenchymal-derived cells. Thus, the fetal liver is a unique and highly available cell source contemporarily candidate for the regenerative medicine of both liver and pancreas. The purpose of this review is to revise the recent literature on the different stem cells populations isolable from fetal liver and candidate to cell therapy of liver diseases and diabetes and to discuss advantages and limitation with respect to other cell sources.

Imaging of the islet neural network

The islets of Langerhans receive signals from the circulation and nerves to modulate hormone secretion in response to physiological cues. Although the rich islet innervation has been documented in the literature dating as far back as Paul Langerhans' discovery of islets in the pancreas, it remains a challenging task for researchers to acquire detailed islet innervation patterns in health and disease due to the dispersed nature of the islet neurovascular network. In this article, we discuss the recent development of 3-dimensional (3D) islet neurohistology, in which transparent pancreatic specimens were prepared by optical clearing to visualize the islet microstructure, vasculature and innervation with deep-tissue microscopy. Mouse islets were used as an example to illustrate how to apply this 3D imaging approach to characterize (i) the islet parasympathetic innervation, (ii) the islet sympathetic innervation and its reinnervation after transplantation under the kidney capsule and (iii) the reactive cellular response of the Schwann cell network in islet injury. While presenting and characterizing the innervation patterns, we also discuss how to apply the signals derived from transmitted light microscopy, vessel painting and immunostaining of neural markers to verify the location and source of tissue information. In summary, the systematic development of tissue labelling, clearing and imaging methods to reveal the islet neuroanatomy offers insights to help study the neural-islet regulatory mechanisms and the role of neural tissue remodelling in the development of diabetes.

MicroRNAs in islet immunobiology and transplantation

The ultimate goal of diabetes therapy is the restoration of physiologic metabolic control. For type 1 diabetes, research efforts are focused on the prevention or early intervention to halt the autoimmune process and preserve β cell function. Replacement of pancreatic β cells via islet transplantation reestablishes physiologic β cell function in patients with diabetes. Emerging research shows that microRNAs (miRNAs), noncoding small RNA molecules produced by a newly discovered class of genes, negatively regulate gene expression. MiRNAs recognize and bind to partially complementary sequences of target messenger RNA (mRNA), regulating mRNA translation and affecting gene expression. Correlation between miRNA signatures and genome-wide RNA expression allows identification of multiple miRNA-mRNA pairs in biological processes. Because miRNAs target functionally related genes, they represent an exciting and indispensable approach for biomarkers and drug discovery. We are studying the role of miRNA in the context of islet immunobiology. Our research aims at understanding the mechanisms underlying pancreatic β cell loss and developing clinically relevant approaches for preservation and restoration of β cell function to treat insulin-dependent diabetes. Herein, we discuss some of our recent efforts related to the study of miRNA in islet inflammation and islet engraftment. Our working hypothesis is that modulation of the expression of specific microRNAs in the transplant microenvironment will be of assistance in enhancing islet engraftment and promoting long-term function.

Transdisciplinary approach to restore pancreatic islet function

The focus of our research is on islet immunobiology. We are exploring novel strategies that could be of assistance in the treatment and prevention of type 1 diabetes, as well as in the restoration of metabolic control via transplantation of insulin producing cells (i.e., islet cells). The multiple facets of diabetes and β-cell replacement encompass different complementary disciplines, such as immunology, cell biology, pharmacology, and bioengineering, among others. Through their interaction and integration, a transdisciplinary dimension is needed in order to address and overcome all aspects of the complex puzzle toward a successful clinical translation of a biological cure for diabetes.

Biliary tree stem cells, precursors to pancreatic committed progenitors: evidence for possible life-long pancreatic organogenesis

Peribiliary glands (PBGs) in bile duct walls, and pancreatic duct glands (PDGs) associated with pancreatic ducts, in humans of all ages, contain a continuous, ramifying network of cells in overlapping maturational lineages. We show that proximal (PBGs)-to-distal (PDGs) maturational lineages start near the duodenum with cells expressing markers of pluripotency (NANOG, OCT4, and SOX2), proliferation (Ki67), self-replication (SALL4), and early hepato-pancreatic commitment (SOX9, SOX17, PDX1, and LGR5), transitioning to PDG cells with no expression of pluripotency or self-replication markers, maintenance of pancreatic genes (PDX1), and expression of markers of pancreatic endocrine maturation (NGN3, MUC6, and insulin). Radial-axis lineages start in PBGs near the ducts' fibromuscular layers with stem cells and end at the ducts' lumens with cells devoid of stem cell traits and positive for pancreatic endocrine genes. Biliary tree-derived cells behaved as stem cells in culture under expansion conditions, culture plastic and serum-free Kubota's Medium, proliferating for months as undifferentiated cells, whereas pancreas-derived cells underwent only approximately 8-10 divisions, then partially differentiated towards an islet fate. Biliary tree-derived cells proved precursors of pancreas' committed progenitors. Both could be driven by three-dimensional conditions, islet-derived matrix components and a serum-free, hormonally defined medium for an islet fate (HDM-P), to form spheroids with ultrastructural, electrophysiological and functional characteristics of neoislets, including glucose regulatability. Implantation of these neoislets into epididymal fat pads of immunocompromised mice, chemically rendered diabetic, resulted in secretion of human C-peptide, regulatable by glucose, and able to alleviate hyperglycemia in hosts. The biliary tree-derived stem cells and their connections to pancreatic committed progenitors constitute a biological framework for life-long pancreatic organogenesis.

Brain death-induced inflammatory activity in human pancreatic tissue: a case-control study

BACKGROUND

Long-term insulin independence after islet transplantation depends on engraftment of a large number of islets. However, the yield of pancreatic islets from brain-dead donors is negatively affected by the up-regulation of inflammatory mediators. Brain death is also believed to increase tissue factor (TF) expression, contributing to a low rate of engraftment.

METHODS

We conducted a case-control study to assess brain death-induced inflammatory effects in human pancreas. Seventeen brain-dead patients and 20 control patients undergoing pancreatectomy were studied. Serum tumor necrosis factor (TNF), interleukin (IL) 6, IL-1β, interferon (IFN) γ, and TF were measured using enzyme-linked immunosorbent assay kits. Gene expressions of these cytokines and TF were evaluated by reverse transcriptase quantitative polymerase chain reaction. Protein quantification was performed by immunohistochemistry in paraffin-embedded pancreas sections.

RESULTS

Brain-dead patients had higher serum concentrations of TNF and IL-6 and increased TNF protein levels compared to controls. The groups had similar TNF, IL-6, IL-1β, and IFN-γ messenger RNA levels in pancreatic tissue. Reverse transcriptase quantitative polymerase chain reaction revealed TF messenger RNA up-regulation in controls. Immunohistochemical analyses showed that brain-dead patients had increased TNF protein levels compared to controls.

CONCLUSIONS

Brain death induces inflammation evidenced by the up-regulation of TNF in serum and pancreatic tissue. Blocking the expression of key inflammatory mediators in brain-dead donors should be evaluated as a new approach to improve the outcomes of islet transplantation.

Three-dimensional islet graft histology: panoramic imaging of neural plasticity in sympathetic reinnervation of transplanted islets under the kidney capsule

Microscopic examination of transplanted islets in an ectopic environment provides information to evaluate islet engraftment, including revascularization and reinnervation. However, because of the dispersed nature of blood vessels and nerves, global visualization of the graft neurovascular network has been difficult. In this research we revealed the neurovascular network by preparing transparent mouse islet grafts under the kidney capsule with optical clearing to investigate the sympathetic reinnervation via three-dimensional confocal microscopy. Normoglycemic and streptozotocin-induced diabetic mice were used in syngeneic islet transplantation, with both groups maintaining euglycemia after transplantation. Triple staining of insulin/glucagon, blood vessels, and tyrosine hydroxylase (sympathetic marker) was used to reveal the graft microstructure, vasculature, and sympathetic innervation. Three weeks after transplantation, we observed perigraft sympathetic innervation similar to the peri-islet sympathetic innervation in the pancreas. Six weeks after transplantation, prominent intragraft, perivascular sympathetic innervation was achieved, resembling the pancreatic intraislet, perivascular sympathetic innervation in situ. Meanwhile, in diabetic recipients, a higher graft sympathetic nerve density was found compared with grafts in normoglycemic recipients, indicating the graft neural plasticity in response to the physiological difference of the recipients and the resolving power of this imaging approach. Overall, this new graft imaging method provides a useful tool to identify the islet neurovascular complex in an ectopic environment to study islet engraftment.

Correction of diabetes mellitus by transplanting minimal mass of syngeneic islets into vascularized small intestinal segment

Transplantation of mature islets into portal vein has been most effective thus far, although attrition of transplanted islets constitutes a major limitation, and alternative approaches are required. We analyzed the mechanisms by which islets engrafted, vascularized and functioned over the long term in the small intestinal submucosa. To determine engraftment, survival and function, 350 syngenic islets were transplanted into either intestinal segments or portal vein of diabetic rats. Islet reorganization, vascularization and function were analyzed by histological analysis, RT-PCR analysis as well as glycemic control over up to 1 year. Transplantation of syngeneic islets in marginal numbers successfully restored normoglycemia in diabetic rats. Transplantation of semi-pure islet preparation did not impair their engraftment, vascularization and function. Islets were morphologically intact and expressed insulin as well as glucagon over the year. Expression of angiogenic genes permitted revascularization of transplanted islets. We identified the expression of transcription factors required for maintenance of beta cells. These studies demonstrated that marginal mass of transplanted islets was sufficient to restore euglycemia in streptozotocin-treated rats. These superior results were obtained despite use of an impure preparation of islets in animals with small intestinal segment. Our findings will help advance new horizons for cell therapy in patients with diabetes.

Multicenter Australian trial of islet transplantation: improving accessibility and outcomes

Whilst initial rates of insulin independence following islet transplantation are encouraging, long-term function using the Edmonton Protocol remains a concern. The aim of this single-arm, multicenter study was to evaluate an immunosuppressive protocol of initial antithymocyte globulin (ATG), tacrolimus and mycophenolate mofetil (MMF) followed by switching to sirolimus and MMF. Islets were cultured for 24 h prior to transplantation. The primary end-point was an HbA1c of <7% and cessation of severe hypoglycemia. Seventeen recipients were followed for ≥ 12 months. Nine islet preparations were transported interstate for transplantation. Similar outcomes were achieved at all three centers. Fourteen of the 17 (82%) recipients achieved the primary end-point. Nine (53%) recipients achieved insulin independence for a median of 26 months (range 7-39 months) and 6 (35%) remain insulin independent. All recipients were C-peptide positive for at least 3 months. All subjects with unstimulated C-peptide >0.2 nmol/L had cessation of severe hypoglycemia. Nine of the 17 recipients tolerated switching from tacrolimus to sirolimus with similar graft outcomes. There was a small but significant reduction in renal function in the first 12 months. The combination of islet culture, ATG, tacrolimus and MMF is a viable alternative for islet transplantation.

Diabetes Mellitus: New Challenges and Innovative Therapies

Diabetes is a common chronic disease affecting an estimated 285 million adults worldwide. The rising incidence of diabetes, metabolic syndrome, and subsequent vascular diseases is a major public health problem in industrialized countries. This chapter summarizes current pharmacological approaches to treat diabetes mellitus and focuses on novel therapies for diabetes mellitus that are under development.

There is great potential for developing a new generation of therapeutics that offer better control of diabetes, its co-morbidities and its complications. Preclinical results are discussed for new approaches including AMPK activation, the FGF21 target, cell therapy approaches, adiponectin mimetics and novel insulin formulations. Gene-based therapies are among the most promising emerging alternatives to conventional treatments. Therapies based on gene silencing using vector systems to deliver interference RNA to cells (i.e. against VEGF in diabetic retinopathy) are also a promising therapeutic option for the treatment of several diabetic complications.

In conclusion, treatment of diabetes faces now a new era that is characterized by a variety of innovative therapeutic approaches that will improve quality of life in the near future.

Genetic modification of primate amniotic fluid-derived stem cells produces pancreatic progenitor cells in vitro

Insulin therapy for type 1 diabetes does not prevent serious long-term complications including vascular disease, neuropathy, retinopathy and renal failure. Stem cells, including amniotic fluid-derived stem (AFS) cells - highly expansive, multipotent and nontumorigenic cells - could serve as an appropriate stem cell source for β-cell differentiation. In the current study we tested whether nonhuman primate (nhp)AFS cells ectopically expressing key pancreatic transcription factors were capable of differentiating into a β-cell-like cell phenotype in vitro. nhpAFS cells were obtained from Cynomolgus monkey amniotic fluid by immunomagnetic selection for a CD117 (c-kit)-positive population. RT-PCR for endodermal and pancreatic lineage-specific markers was performed on AFS cells after adenovirally transduced expression of PDX1, NGN3 and MAFA. Expression of MAFA was sufficient to induce insulin mRNA expression in nhpAFS cell lines, whereas a combination of MAFA, PDX1 and NGN3 further induced insulin expression, and also induced the expression of other important endocrine cell genes such as glucagon, NEUROD1, NKX2.2, ISL1 and PCSK2. Higher induction of these and other important pancreatic genes was achieved by growing the triply infected AFS cells in media supplemented with a combination of B27, betacellulin and nicotinamide, as well as culturing the cells on extracellular matrix-coated plates. The expression of pancreatic genes such as NEUROD1, glucagon and insulin progressively decreased with the decline of adenovirally expressed PDX1, NGN3 and MAFA. Together, these experiments suggest that forced expression of pancreatic transcription factors in primate AFS cells induces them towards the pancreatic lineage.

25 YEARS OF THE RICORDI AUTOMATED METHOD FOR ISLET ISOLATION

The year 2013 marks the 25th anniversary of the Automated Method for islet isolation. The dissociation chamber at the core of the Automated Method was developed by Dr. Camillo Ricordi in 1988 to enhance the disassembling of the pancreatic tissue via a combined enzymatic and mechanical digestion while preserving endocrine cell cluster integrity. This method has ever since become the gold standard for human and large animal pancreas processing, contributing to the success and increasing number of clinical trials of islet transplantation worldwide. Herein we offer an attempt to a comprehensive, yet unavoidably incomplete, historical review of the progress in the field of islet cell transplantation to restore beta-cell function in patients with diabetes.

Macroporous three-dimensional PDMS scaffolds for extrahepatic islet transplantation

Clinical islet transplantation has demonstrated success in treating type 1 diabetes. A current limitation is the intrahepatic portal vein transplant site, which is prone to mechanical stress and inflammation. Transplantation of pancreatic islets into alternative sites is preferable, but challenging, as it may require a three-dimensional vehicle to confer mechanical protection and to confine islets to a well-defined, retrievable space where islet neovascularization can occur. We have fabricated biostable, macroporous scaffolds from poly(dimethylsiloxane) (PDMS) and investigated islet retention and distribution, metabolic function, and glucose-dependent insulin secretion within these scaffolds. Islets from multiple sources, including rodents, nonhuman primates, and humans, were tested in vitro. We observed high islet retention and distribution within PDMS scaffolds, with retention of small islets (< 100 µm) improved through the postloading addition of fibrin gel. Islets loaded within PDMS scaffolds exhibited viability and function comparable to standard culture conditions when incubated under normal oxygen tensions, but displayed improved viability compared to standard two-dimensional culture controls under low oxygen tensions. In vivo efficacy of scaffolds to support islet grafts was evaluated after transplantation in the omental pouch of chemically induced diabetic syngeneic rats, which promptly achieved normoglycemia. Collectively, these results are promising in that they indicate the potential for transplanting islets into a clinically relevant, extrahepatic site that provides spatial distribution of islets as well as intradevice vascularization.

A new enzyme mixture to increase the yield and transplant rate of autologous and allogeneic human islet products

BACKGROUND

The optimal enzyme blend that maximizes human islet yield for transplantation remains to be determined. In this study, we evaluated eight different enzyme combinations (ECs) in an attempt to improve islet yield. The ECs consisted of purified, intact or truncated class 1 (C1) and class 2 (C2) collagenases from Clostridium histolyticum (Ch), and neutral protease (NP) from Bacillus thermoproteolyticus rokko (thermolysin) or Ch (ChNP).

METHODS

We report the results of 249 human islet isolations, including 99 deceased donors (research n=57, clinical n=42) and 150 chronic pancreatitis pancreases. We prepared a new enzyme mixture (NEM) composed of intact C1 and C2 collagenases and ChNP in place of thermolysin. The NEM was first tested in split pancreas (n=5) experiments and then used for islet autologous (n=21) and allogeneic transplantation (n=10). Islet isolation outcomes from eight different ECs were statistically compared using multivariate analysis.

RESULTS

The NEM consistently achieved higher islet yields from pancreatitis (P<0.003) and deceased donor pancreases (P<0.001) than other standard ECs. Using the NEM, islet products met release criteria for transplantation from 8 of 10 consecutive pancreases, averaging 6510 ± 2150 islet equivalent number/gram (IEQ/g) pancreas and 694,681 ± 147,356 total IEQ/transplantation. In autologous isolation, the NEM yielded more than 200,000 IEQ from 19 of 21 pancreases (averaging 422,893 ± 181,329 total IEQ and 5979 ± 1469 IEQ/kg recipient body weight) regardless of the severity of fibrosis.

CONCLUSIONS

A NEM composed of ChNP with CIzyme high intact C1 collagenase recovers higher islet yield from deceased and pancreatitis pancreases while retaining islet quality and function.

β-Cells with relative low HIMP1 overexpression levels in a transgenic mouse line enhance basal insulin production and hypoxia/hypoglycemia tolerance

Rodent pancreatic β-cells that naturally lack hypoglycemia/hypoxia inducible mitochondrial protein 1 (HIMP1) are susceptible to hypoglycemia and hypoxia influences. A linkage between the hypoglycemia/hypoxia susceptibility and the lack of HIMP1 is suggested in a recent study using transformed β-cells lines. To further illuminate this linkage, we applied mouse insulin 1 gene promoter (MIP) to control HIMP1-a isoform cDNA and have generated three lines (L1 to L3) of heterozygous HIMP1 transgenic (Tg) mice by breeding of three founders with C57BL/6J mice. In HIMP1-Tg mice/islets, we performed quantitative polymerase chain reaction (PCR), immunoblot, histology, and physiology studies to investigate HIMP1 overexpression and its link to β-cell function/survival and body glucose homeostasis. We found that the HIMP1 level increased steadily in β-cells of L1 to L3 heterozygous HIMP1-Tg mice. HIMP1 overexpression at relatively lower levels in L1 heterozygotes results in a negligible decline in blood glucose concentrations and an insignificant elevation in blood insulin levels, while HIMP1 overexpression at higher levels are toxic, causing hyperglycemia in L2/3 heterozygotes. Follow-up studies in 5-30-week-old L1 heterozygous mice/islets found that HIMP1 overexpression at relatively lower levels in β-cells has enhanced basal insulin biosynthesis, basal insulin secretion, and tolerances to low oxygen/glucose influences. The findings enforced the linkage between the hypoglycemia/hypoxia susceptibility and the lack of HIMP1 in β-cells, and show a potential value of HIMP1 overexpression at relatively lower levels in modulating β-cell function and survival.

Differentiation of mesenchymal stem cells derived from pancreatic islets and bone marrow into islet-like cell phenotype

BACKGROUND

Regarding regenerative medicine for diabetes, accessible sources of Mesenchymal Stem Cells (MSCs) for induction of insular beta cell differentiation may be as important as mastering the differentiation process itself.

METHODOLOGY/PRINCIPAL FINDINGS

In the present work, stem cells from pancreatic islets (human islet-mesenchymal stem cells, HI-MSCs) and from human bone marrow (bone marrow mesenchymal stem cells, BM-MSCs) were cultured in custom-made serum-free medium, using suitable conditions in order to induce differentiation into Islet-like Cells (ILCs). HI-MSCs and BM-MSCs were positive for the MSC markers CD105, CD73, CD90, CD29. Following this induction, HI-MSC and BM-MSC formed evident islet-like structures in the culture flasks. To investigate functional modifications after induction to ILCs, ultrastructural analysis and immunofluorescence were performed. PDX1 (pancreatic duodenal homeobox gene-1), insulin, C peptide and Glut-2 were detected in HI-ILCs whereas BM-ILCs only expressed Glut-2 and insulin. Insulin was also detected in the culture medium following glucose stimulation, confirming an initial differentiation that resulted in glucose-sensitive endocrine secretion. In order to identify proteins that were modified following differentiation from basal MSC (HI-MSCs and BM-MSCs) to their HI-ILCs and BM-ILCs counterparts, proteomic analysis was performed. Three new proteins (APOA1, ATL2 and SODM) were present in both ILC types, while other detected proteins were verified to be unique to the single individual differentiated cells lines. Hierarchical analysis underscored the limited similarities between HI-MSCs and BM-MSCs after induction of differentiation, and the persistence of relevant differences related to cells of different origin.

CONCLUSIONS/SIGNIFICANCE

Proteomic analysis highlighted differences in the MSCs according to site of origin, reflecting spontaneous differentiation and commitment. A more detailed understanding of protein assets may provide insights required to master the differentiation process of HI-MSCs to functional beta cells based only upon culture conditioning. These findings may open new strategies for the clinical use of BM-MSCs in diabetes.

Validation of Islet Transport From a Geographically Distant Isolation Center Enabling Equitable Access and National Health Service Funding of a Clinical Islet Transplant Program for England

Islet transplantation has become established as a successful treatment for type 1 diabetes complicated by recurrent severe hypoglycemia. In the UK access has been limited to a few centrally located units. Our goal was to validate a quality-assured system for safe/effective transport of human islets in the UK and to successfully undertake the first transplants with transported islets. Pancreases were retrieved from deceased donors in the north of England and transported to King's College London using two-layer method (TLM) or University of Wisconsin solution alone. Islets were isolated and transported back to Newcastle in standard blood transfusion or gas-permeable bags with detailed evaluation pre- and posttransport. In the preclinical phase, islets were isolated from 10 pancreases with mean yield of 258,000 islet equivalents. No significant differences were seen between TLM and University of Wisconsin solution organ preservation. A significant loss of integrity was demonstrated in islets shipped in gas-permeable bags, whereas sterility, number, purity, and viability were maintained in blood transfusion bags. Maintenance of secretory granules and glucose-stimulated insulin secretion was confirmed following transport. A Standard Operating Procedure enabling final pretransplant quality control from a simple side-arm sample was validated. Moreover, levels of insulin and cytokines in transport medium were low, enabling transplant without centrifugation/resuspension at the recipient site. Six clinical transplants of transported islets were undertaken in five recipients with 100% primary graft function and resolution of severe hypoglycemia. Safe and clinically effective islet transport has been established facilitating sustainable NHS funding of a clinical islet transplant program for the UK.

Effect of exenatide on gastric emptying and graft survival in islet allograft recipients

OBJECTIVE

To evaluate the effect of exenatide on gastric emptying and long-term metabolic control.

METHODS

Ten islet allograft recipients treated with exenatide up to 4 years. Data from a mixed meal test with (MMT+) versus without (MMT-) administration of exenatide before boost ingestion were analyzed at 6, 12, 24, 36, or 48 months after initiation of exenatide treatment. None of the subjects were symptomatic for gastroparesis before or during the study. The c-peptide, acetaminophen absorption and glucose responses to MMT were analyzed by Student t test and analysis of variance.

RESULTS

Average exenatide dose was 12.75 ± 9.46 μg/dL. The MMT subjects included two groups those with acetaminophen peak ≤120 minutes ("good gastric emptying; n = 4") versus those with an acetaminophen peak ≥180 minutes ("delayed gastric emptying"). Among the MMT+, acetaminophen absorption was the same in both groups (P = .27). Up to 48 months exenatide delayed time to peak of glucose, c-peptide, and acetaminophen as well as suppressed the glucagon response to MMT mean peak: 70.89 ± 12.45 versus 43.24 ± 4.67. The mean values of c-peptide and glucose responses to MMT were not significantly different.

CONCLUSIONS

Long-term exenatide administration up to 4 years was safe in islet transplant recipients, even in the presence of delayed gastric emptying. The effects of exenatide were acute and reversible when the agent was withdrawn. The main difficulty with the use of exenatide in islet transplant subjects is their poor tolerability, although the physiological effects are clearly evident even at low doses. Approximately 63% of total subjects under exenatide treatment discontinued the drug due to nausea and vomiting. The use of new GLP1 analogs with longer half lives and fewer side effects may help to attain higher GLP1 levels, therefore improving islet function and survival.

Evaluation of viable β-cell mass is useful for selecting collagenase for human islet isolation: comparison of collagenase NB1 and liberase HI

The selection of enzyme blend is critical for the success of human islet isolations. Liberase HI collagenase (Roche) was introduced in the 1990s and had been widely used for clinical islet transplantation. More recently, a blend collagenase NB1 has been rendered available. The aim of this study was to evaluate the isolation outcomes and islet quality comparing human islet cells processed using NB1 and Liberase HI. A total of 90 isolations processed using NB1 (n = 40) or Liberase HI (n = 50) was retrospectively analyzed. Islet yield, function in vitro and in vivo, cellular (including β-cell-specific) viability and content, as well as isolation-related factors were compared. No significant differences in donor-related factors were found between the groups. There were also no significant differences in islet yields (NB1 vs. Liberase: 263,389 ± 21,550 vs. 324,256 ± 27,192 IEQ; p = n.s., respectively). The pancreata processed with NB1 showed a significantly longer digestion time (18.6 ± 0.7 vs. 14.5 ± 0.5 min, p < 0.01), lower β-cell viability (54.3 ± 3.4% vs. 72.0 ± 2.1%, p < 0.01), β-cell mass (93,671 ± 11,150 vs. 148,961 ± 12,812 IEQ, p < 0.01), and viable β-cell mass (47,317 ± 6,486 vs. 106,631 ± 10,228 VβIEQ, p < 0.01) than Liberase HI. In addition, islets obtained with Liberase showed significantly better graft function in in vivo assessment of islet potency. The utilization of collagenase NB1 in human islet isolation was associated with significantly lower β-cell viability, mass, and islet potency in vivo in our series when compared to Liberase HI, even though there was no significant difference in islet yields between the groups. Evaluation of viable β-cell mass contained in human islet preparations will be useful for selecting enzyme blends.

One hundred human pancreatic islet isolations at Baylor Research Institute

The effectiveness of pancreatic islet isolation must be maximized to make islet cell transplantation (ICT) a standard therapy. We have performed 100 human islet isolations at Baylor Research Institute including islet isolations for research, for clinical allogeneic transplantation, and for autologous islet transplantation. In this study, we analyzed the results of these isolations. First, we assessed 79 islet isolations using brain-dead donors to determine variables associated with successful islet isolation. Univariate logistic regression analysis revealed that seven variables influenced the success of islet isolation for allogeneic ICT: cause of death, mechanism of death, techniques for pancreas procurement and preservation, heavy fatty infiltration, collagenase type, dilution time, and islet purification method. Multivariate regression analysis revealed that only the current isolation protocol, the Baylor Islet Isolation Method (BIIM)-with its four required elements of pancreas procurement by the team, pancreatic ductal injection, the two-layer method with perfluorocarbon, and density-adjusted density gradient purification-had a significant positive impact on successful islet isolation (P = 0.02). Second, we compared allogeneic and autologous ICT using the BIIM. There were no significant differences in islet yields between allogeneic and autologous ICT using the BIIM; total islet yield after purification was 628 ± 84 × 10(3) IE in allogeneic ICT vs. 576 ± 49 × 10(3) IE in autologous ICT (P = 0.59). This retrospective study revealed that the BIIM provided favorable outcomes for both autologous and allogeneic ICT.

A recent survey confirms the efficacy and the safety of implanted insulin pumps during long-term use in poorly controlled type 1 diabetes patients

BACKGROUND

This article reports a prolonged trial with insulin pumps implanted in patients with type 1 diabetes showing poor glucose control and a high rate of complications.

METHODS

We reviewed data from 181 patients undergoing implanted insulin pump therapy. Analysis included hemoglobin A1c (HbA1c) values, body weight, and diabetes complications status.

RESULTS

At implantation, the mean age was 43 (range, 19-72) years, mean duration of diabetes was 22.2 (2-52) years, and mean body weight was 68.6 (43-104) kg. The complication status involved retinopathy (62% of patients), neuropathy (34.6%), nephropathy (26%), and cardiovascular disease (14%). Patients' previous insulin treatment regimen was multiple daily injections (17.1%) or continuous subcutaneous insulin infusion (82.9%). HbA1c levels significantly dropped from 7.9 ± 1.2% to 7.6 ± 1.2% after 1 year (P < 0.01) and remained within the range of 7.5-7.6% for up to 5 years. No significant variation of body weight or complications status occurred.

CONCLUSIONS

Implanted insulin pump therapy demonstrates long-term benefits in type 1 diabetes patients who have poor prognosis under intensive subcutaneous treatment.

Assessment of beta cell viability

This unit contains detailed protocols for the simultaneous identification of the human pancreatic β cells and determination of their viability by flow cytometry. The enumeration of β cells is based on the ability of the cell-permeable form of the zinc-selective dye, FluoZin-3-AM, to bind intracellular labile zinc stored at higher levels in these cells than any other types of cells in the body. Although staining of intracellular labile zinc by FluoZin-3-AM is dependent on the metabolic activity of β cells, co-staining with a mitochondrial transmembrane potential indicator allows the accurate determination of viability. Simultaneous measurement of intracellular antioxidant thiols is also compatible with the detection of β cells containing metabolically active mitochondria. The method for assessing the mitochondrial functionality by flow cytometry described herein is simple to perform and sufficient to detect the viability of β cells in human islet preparations.

Alterations of the female reproductive system in islet recipient receiving immunosuppression

Pancreatic islet allotransplantation is an option for patients with unstable type 1 diabetes mellitus (T1DM). Major improvements in islet isolation techniques and the implementation of steroid-free immunosuppressive regimens can maintain insulin independence in the majority of T1DM for at least 1 year after transplantation. Recent studies have emphasized the impact of sirolimus on female reproductive tract. In this communication we report on the alterations of the female reproductive tract in 18 chronically immunosuppressed patients with T1DM following allogenic islet transplantation. Previous research has shown development of ovarian cysts in islet transplant patients receiving sirolimus. We extensively reevaluated this and other possible side effects on the female reproductive system. These side effects have been underestimated, although they are significant, requiring surgical or intensive medical treatment. Pre- and posttransplant gynecological evaluation should be performed to address the development of complications secondary to sirolimus in order to intervene sooner with alternative therapies.

Recurrence of autoimmunity in pancreas transplant patients: research update

Type 1 diabetes is an autoimmune disorder leading to loss of pancreatic β-cells and insulin secretion, followed by insulin dependence. Islet and whole pancreas transplantation restore insulin secretion. Pancreas transplantation is often performed together with a kidney transplant in patients with end-stage renal disease. With improved immunosuppression, immunological failures of whole pancreas grafts have become less frequent and are usually categorized as chronic rejection. However, growing evidence indicates that chronic islet autoimmunity may eventually lead to recurrent diabetes, despite immunosuppression to prevent rejection. Thus, islet autoimmunity should be included in the diagnostic work-up of graft failure and ideally should be routinely assessed pretransplant and on follow-up in Type 1 diabetes recipients of pancreas and islet cell transplants. There is a need to develop new treatment regimens that can control autoimmunity, as this may not be effectively suppressed by conventional immunosuppression.

Gut microbiota in health and disease

Gut microbiota is an assortment of microorganisms inhabiting the length and width of the mammalian gastrointestinal tract. The composition of this microbial community is host specific, evolving throughout an individual's lifetime and susceptible to both exogenous and endogenous modifications. Recent renewed interest in the structure and function of this "organ" has illuminated its central position in health and disease. The microbiota is intimately involved in numerous aspects of normal host physiology, from nutritional status to behavior and stress response. Additionally, they can be a central or a contributing cause of many diseases, affecting both near and far organ systems. The overall balance in the composition of the gut microbial community, as well as the presence or absence of key species capable of effecting specific responses, is important in ensuring homeostasis or lack thereof at the intestinal mucosa and beyond. The mechanisms through which microbiota exerts its beneficial or detrimental influences remain largely undefined, but include elaboration of signaling molecules and recognition of bacterial epitopes by both intestinal epithelial and mucosal immune cells. The advances in modeling and analysis of gut microbiota will further our knowledge of their role in health and disease, allowing customization of existing and future therapeutic and prophylactic modalities.

Pancreas vs. islet transplantation: a call on the future

PURPOSE OF REVIEW

The aim of this article is to review recent reports on whole pancreas and islet cell transplantation. It focuses on 'what the call to the future looks like' for both therapies as treatment options for those type 1 diabetes patients who do not respond well to conventional therapy.

RECENT FINDINGS

The major benefit of pancreas transplantation is the reversal of diabetes improvement of diabetes complications. Although the procedure requires major surgery and life-long immunosuppression, it remains the gold standard for a specific population of patients who suffer from type 1 diabetes and who do not respond to conventional therapy. Allogeneic islet transplantation is a promising alternative to pancreas transplantation, but patient outcomes remain less than optimal and significant progress is required in order for this procedure to be considered a reliable therapy.

CONCLUSION

Several factors have to be taken into consideration before making the decision of which of these procedures would better suit a patient with type 1 diabetes.