Setting Of Islet Transplantation Research Articles

Firefly Rats: Illuminating the Scientific Community in Transplantation Research.

Fireflies produce light through luciferase-catalyzed reactions involving luciferin, oxygen, and adenosine triphosphate, distinct from other luminescent organisms. This unique feature has revolutionized molecular biology and physiology, serving as a valuable tool for cellular research. Luciferase-based bioluminescent imaging enabled the creation of transgenic animals, such as Firefly Rats. Firefly Rats, created in 2006, ubiquitously express luciferase and have become a critical asset in scientific investigations. These rats have significantly contributed to transplantation and tissue engineering studies. Their low immunogenicity reduces graft rejection risk, making them ideal for long-term tracking of organ/tissue/cellular engraftments. Importantly, in the islet transplantation setting, the ubiquitous luciferase expression in these rats does not alter islet morphology or function, ensuring accurate assessments of engrafted islets. Firefly Rats have illuminated the path of transplantation research worldwide for over a decade and continue accelerating scientific advancements in many fields.

Pancreatic Islet Cell Transplantation: Graft Stability and Metabolic Outcomes.

Pancreatic islet transplantation is a rapidly evolving field. It has been increasingly regarded as a promising approach for the correction of dysglycemia associated with type 1 diabetes mellitus (allogenic islet transplantation), or the prevention of surgical diabetes in chronic pancreatitis subjects undergoing total pancreatectomy (autologous islet transplantation). In this review, we discuss the latest literature pertaining to metabolic outcomes of autologous and allogenic islet transplantation, shedding close light on our own latest experience in the autologous islet transplantation setting.

ST8Sia6 generated α2,8-disialic acids mitigate hyperglycemia in multiple low dose streptozocin-induced diabetes

Abstract Type 1 diabetes is an autoimmune disease that destroys insulin-producing beta cells in the pancreatic islets. Although exogenous insulin replacement therapy is lifesaving, precise blood glucose management remains a significant challenge. Experimental islet transplantation restores normoglycemia, but the lack of available islets and graft rejection present major barriers to widespread adoption as standard therapy. The islet resident macrophage (IRM) is in close contact with beta cells, efficiently presents islet antigen to autoreactive T cells, and is critical to disease occurrence. We have demonstrated that murine IRMs express high levels of Siglec-E, an immune-regulatory receptor that preferentially binds α2,8-disialic acids in cis or in trans. When islets were exposed to streptozocin (STZ)-induced stress in culture, beta cells upregulated ligands for Siglec-E. To determine the biological significance of this, we generated a mouse model where ST8Sia6, the sialyltransferase that produces α2,8-disialic acids and thus Siglec-E ligands, is constitutively overexpressed in beta cells. This increased trans Siglec-E binding affinity to the beta cell surface, and mitigated hyperglycemia in the multiple low-dose STZ model of diabetes. Significant reduction in blood sugar was evident at 14 days post-initial injection of STZ, coinciding with T cell infiltration of islets. T cells from ST8Sia6+ islets were less activated when compared to littermates. This work reveals a novel and important role for Siglec-E in autoimmune diabetes and provides insight into how rational targeting of this immune receptor may instruct islet-residing antigen presenting cells to provide local tolerance signals in the setting of islet transplantation.

Mesenchymal stromal cells support endothelial cell interactions in an intramuscular islet transplantation model.

BackgroundMesenchymal stromal cells (MSC) have been under investigation for a number of therapies and have lately been in focus as immunosuppressive actors in the field of transplantation. Herein we have extended our previously published in vitro model of MSC-islets in an experimental setting of islet transplantation to the abdominal muscle.Human islets coated with luciferase-GFP transduced human MSC were transplanted to the abdomen muscle tissue of NOD-scid ILR2γnull mice and cellular interactions were investigated by confocal microscopy.ResultsThe MSC reduced fibrotic encapsulation and facilitated endothelial cell interactions. In particular, we show a decreased fraction of αSMA expressing fibrotic tissue surrounding the graft in presence of MSC-islets compared to islets solely distributed into the muscle tissue. Also, in the presence of MSC, human islet endothelial cells migrated from the center of the graft out into the surrounding tissue forming chimeric blood vessels with recipient endothelial cells. Further, in the graft periphery, MSC were seen interacting with infiltrating macrophages.ConclusionsHere, in our experimental in vivo model of composite human islets and luciferase-GFP-transduced human MSC, we enable the visualization of close interactions between the MSC and the surrounding tissue. In this model of transplantation the MSC contribute to reduced fibrosis and increased islet endothelial cell migration. Furthermore, the MSC interact with the recipient vasculature and infiltrating macrophages.Electronic supplementary materialThe online version of this article (doi:10.1186/s40340-015-0010-9) contains supplementary material, which is available to authorized users.

Mitochondrial Respiration in Insulin-Producing β-Cells: General Characteristics and Adaptive Effects of Hypoxia.

ObjectiveTo provide novel insights on mitochondrial respiration in β-cells and the adaptive effects of hypoxia.Methods and DesignInsulin-producing INS-1 832/13 cells were exposed to 18 hours of hypoxia followed by 20–22 hours re-oxygenation. Mitochondrial respiration was measured by high-resolution respirometry in both intact and permeabilized cells, in the latter after establishing three functional substrate-uncoupler-inhibitor titration (SUIT) protocols. Concomitant measurements included proteins of mitochondrial complexes (Western blotting), ATP and insulin secretion.ResultsIntact cells exhibited a high degree of intrinsic uncoupling, comprising about 50% of oxygen consumption in the basal respiratory state. Hypoxia followed by re-oxygenation increased maximal overall respiration. Exploratory experiments in peremabilized cells could not show induction of respiration by malate or pyruvate as reducing substrates, thus glutamate and succinate were used as mitochondrial substrates in SUIT protocols. Permeabilized cells displayed a high capacity for oxidative phosphorylation for both complex I- and II-linked substrates in relation to maximum capacity of electron transfer. Previous hypoxia decreased phosphorylation control of complex I-linked respiration, but not in complex II-linked respiration. Coupling control ratios showed increased coupling efficiency for both complex I- and II-linked substrates in hypoxia-exposed cells. Respiratory rates overall were increased. Also previous hypoxia increased proteins of mitochondrial complexes I and II (Western blotting) in INS-1 cells as well as in rat and human islets. Mitochondrial effects were accompanied by unchanged levels of ATP, increased basal and preserved glucose-induced insulin secretion.ConclusionsExposure of INS-1 832/13 cells to hypoxia, followed by a re-oxygenation period increases substrate-stimulated respiratory capacity and coupling efficiency. Such effects are accompanied by up-regulation of mitochondrial complexes also in pancreatic islets, highlighting adaptive capacities of possible importance in an islet transplantation setting. Results also indicate idiosyncrasies of β-cells that do not respire in response to a standard inclusion of malate in SUIT protocols.

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.

Cross reactivity of allo and xenoimmune response in transplantation (TRAN2P.964)

Abstract Many type I diabetes patients are suffering from hypoglycaemia unawareness. And porcine islet transplantation is one of the promising modalities to treat the problematic condition in a physiologic manner. But by transplanting porcine islet, xenoantigen sensitization is inevitable. For clinical application of porcine islet transplantation, the knowledge of the outcome and consequent effects of xenoantigen sensitization needs to be fully established. Our focus was whether xenoantigen sensitization would influence subsequent allotransplantation in any way. We confirmed that xenoantigen sensitization does not induce alloreactive antibody. And by ELISpot assay we demonstrated that xenoreactive T cells are not responsive to alloantigen. Lastly, we confirmed that xenoantigen sensitized mice have the same graft survival day compared with non sensitized mice in allogeneic islet transplantation setting. With these results put together, we conclude that porcine antigen sensitization can not induce alloantigen sensitization in mice.

Regional Differences in Islet Distribution in the Human Pancreas - Preferential Beta-Cell Loss in the Head Region in Patients with Type 2 Diabetes

While regional heterogeneity in islet distribution has been well studied in rodents, less is known about human pancreatic histology. To fill gaps in our understanding, regional differences in the adult human pancreas were quantitatively analyzed including the pathogenesis of type 2 diabetes (T2D). Cadaveric pancreas specimens were collected from the head, body and tail regions of each donor, including subjects with no history of diabetes or pancreatic diseases (n = 23) as well as patients with T2D (n = 12). The study further included individuals from whom islets were isolated (n = 7) to study islet yield and function in a clinical setting of islet transplantation. The whole pancreatic sections were examined using an innovative large-scale image capture and unbiased detailed quantitative analyses of the characteristics of islets from each individual (architecture, size, shape and distribution). Islet distribution/density is similar between the head and body regions, but is >2-fold higher in the tail region. In contrast to rodents, islet cellular composition and architecture were similar throughout the pancreas and there was no difference in glucose-stimulated insulin secretion in islets isolated from different regions of the pancreas. Further studies revealed preferential loss of large islets in the head region in patients with T2D. The present study has demonstrated distinct characteristics of the human pancreas, which should provide a baseline for the future studies integrating existing research in the field and helping to advance bi-directional research between humans and preclinical models.

Antiapoptotic Actions of Exendin-4 against Hypoxia and Cytokines Are Augmented by CREB

Islets isolated from cadaveric donor pancreas are functionally viable and can be transplanted in diabetic patients to reduce insulin requirements. This therapeutic approach is less efficient because a significant portion of functional islets is lost due to oxidative stress, inflammation, and hypoxia. Exendin-4, a glucagon-like peptide-1 receptor agonist, is known to improve islet survival through activation of the transcription factor, cAMP response element binding protein (CREB). However, isolated human islets are exposed to several stresses known to down-regulate CREB. The objective of the present study was to determine whether the cytoprotective actions of exendin-4 in human islets can be augmented by increasing the levels of CREB. Simulation of ischemia/reperfusion injury and exposure to hypoxic conditions in cultured human islets resulted in decreased CREB activation and induction of apoptosis. Islets were transduced with adenoviral CREB followed by exposure to exendin-4 as a strategy for improving their survival. This combination increased the levels of several proteins needed for β-cell survival and function, including insulin receptor substrate-2, Bcl-2, and baculoviral IAP repeat-containing 3, and suppressed the expression of proapoptotic and inflammatory genes. A combination of CREB and exendin-4 exerted enhanced antiapoptotic action in cultured islets against hypoxia and cytokines. More significantly, transplantation of human islets transduced with adenoviral CREB and treated with exendin-4 showed improved glycemic control over a 30-d period in diabetic athymic nude mice. These observations have significant implications in the therapeutic potential of exendin-4 and CREB in the islet transplantation setting as well as in preserving β-cell mass of diabetic patients.

The role of macrophage migration inhibitory factor on glucose metabolism and diabetes

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine involved in many inflammatory reactions and disorders, and it has become evident that it also affects glucose homeostasis. The protein is produced by pancreatic beta cells and can promote the release of insulin. It also modulates glucose uptake, glycolysis and insulin resistance in insulin target cells such as the adipocyte, myocyte and cardiomyocyte. Possessing both immunological and endocrinological properties, MIF has been associated with the development of type 1 and type 2 diabetes, and it may be important in the setting of islet transplantation. The present review summarises our current knowledge, based on clinical and research data, on the impact of MIF on both physiological and pathological aspects of glucose metabolism.

Amelioration of Diabetes in Mice after Single-Donor Islet Transplantation Using the Controlled Release of Gelatinized FGF-2

Fibroblast growth factor (FGF)-2 has been recognized to be a key element involved in angiogenesis and a putative factor involved in stem cell-mediated islet regeneration. However, the usefulness of FGF-2 in an islet transplantation setting has not yet been explored. We therefore evaluated the effect of FGF-2 on both islet culture and islet transplantation. Isolated islets were cultured in the presence of 100 ng/ml FGF-2 for a week and then the glucose-responding insulin secretion and insulin contents were measured. Gelatinized FGF-2 (100 ng), which allowed the controlled release of FGF-2, was used for islet transplantation of streptozotocin-induced diabetic mice. Islets (150 IEQ), obtained from a single donor, mixed with gelatinized FGF-2, were transplanted into the subrenal capsule of the mice and the animals were observed for 30 days. Revascularization around the islet grafts was examined. The blood glucose levels were measured and the intraperitoneal glucose tolerance test (IPGTT) was performed. The supplementation of FGF-2 maintained proper insulin secretion and insulin contents in an in vitro culture. The use of gelatinized FGF-2 facilitated revascularization and favorable islet engraftment, thus resulting in an amelioration of the blood glucose levels in diabetic mice. The utilization of FGF-2 showed increased contents of insulin in the islet grafts and revealed a similar pattern as that of normal healthy mice in IPGTT. In contrast, the transplantation of islets without FGF-2 supplementation showed poor revascularization and failed to control the blood glucose levels in the diabetic mice.

Prevention of core cell damage in isolated islets of Langerhans by low temperature preconditioning

To study the core cell damage in isolated islets of Langerhans and its prevention by low temperature preconditioning (26 degrees). Islets were cultured at 37 degrees for 7-14 d after isolation, and then at 26 degrees for 2, 4 and 7 d before additional culture at 37 degrees for another 7 d. Core cell damage in the isolated islets was monitored by video-microscopy and analyzed quantitatively by use of a computer-assisted image analysis system. The analysis included daily measurement of the diameter and the area of the isolated islets and the area of the core cell damage that developed in those islets over time during culture. Histology and TdT-mediated dUTP-biotin nick end labeling (TUNEL) assay were used to characterize the cell damage and to monitor islet function. Microscopic analysis showed that during the 7 to 14 d of culture at 37 degrees, core cell damage occurred in the larger islets with diameters >200 microm, which included both necrotic and apoptotic cell death. Low temperature (26 degrees) culture could prevent core cell damage of isolated islets. The 7-d culture procedure at 26 degrees could inhibit most of the core cell (excluding diameters >300 microm) damages when the islets were re-warmed at 37 degrees. Our results indicate that core cell damage within isolated islets of Langerhans correlates with the size of islets. Low temperature (26 degrees) culture can prevent core cell damage in isolated islets, and successfully precondition these islets for incubation at 37 degrees. These novel findings may help to understand the pathophysiology of early loss of islet tissue after transplantation, and may provide a new strategy to improve graft function in the clinical setting of islet transplantation.

Activation of macrophage-associated molecules after brain death in islets.

Islet transplantation is now established as an optional treatment for type I diabetes. However, rates of insulin independence in islet transplant recipients are still low. Although the major source of allograft is derived from brain-dead patient, the nonphysiologic state of brain death (BD) deteriorates organs such as liver and kidney. To determine the effects of BD on islets, a rodent model of BD has been used. Histologically, islets of BD rats showed decreased permeability and impaired integrity of the cell membranes. Flow cytometric analysis showed that CD11b/c-positive cells within islets were slightly increased in BD. This result suggests that BD induces macrophage infiltration into the islets. Moreover, RT-PCR revealed significant augmentation of macrophages-associated inflammatory molecules (IL-1beta, IL-6, TNF-alpha, and MCP-1) in islets from a BD donor. Inducible nitric oxide synthase (iNOS) was weakly expressed, although not reaching statistical significance compared with control. Our results indicate that islets from a BD donor are immunologically activated and have a potential risk factor for early graft loss and a poor long-term function of grafts in clinical setting of islet transplantation. Immunomodulation, to eliminate intraislet immunocytes and/or activated macro phage-associated molecules, might be necessary for the better outcome after islet graft from BD donors.

Transduction of human and mouse pancreatic islet cells using a bicistronic recombinant adeno-associated viral vector.

Recent reports indicate successful transduction of pancreatic islets using recombinant adeno-associated viral (rAAV) vectors. This advance offers new possibilities in rendering islets resistant to rejection and recurrence of autoimmune destruction in the setting of islet transplantation as treatment of type 1 diabetes. Most gene delivery approaches using islets have thus far involved transduction with a single gene. However, the concomitant delivery of more than one gene encoding cytoprotective and/or immunoregulatory molecules may offer superior clinical utility. Here, we have generated a bicistronic rAAV (serotype 2) vector incorporating a viral internal ribosome entry site (IRES), derived from polio virus type 1, to allow for translation of two coupled cDNAs from a single mRNA transcript. Our study demonstrates the ability of this vector to produce significant expression of two reporter proteins in human and mouse islets in vitro. This expression did not interfere with beta-cell function. Transduction was maintained in vivo following transplantation of mouse islets. These data are the first report of efficient islet cell transduction with two genes using a single bicistronic rAAV vector and have direct implications for strategies aimed at enhancing islet transplant survival.

Contribution of adenoviral-mediated superoxide dismutase gene transfer to the reduction in nitric oxide-induced cytotoxicity on human islets and INS-1 insulin-secreting cells.

Vulnerability of pancreatic islets to oxygen free radicals and nitric oxide contributes to islet transplantation obstacles. This susceptibility can be linked to the low expression levels of antioxidant enzymes in islets. Our aim was to investigate the effect of overexpressing Cu/Zn superoxide dismutase in human islets through a simple procedure on the cytotoxic effects of two nitric oxide donors: 3-morpholinosydnonimine (SIN-1) and S-Nitroso-N-acetyl-D,L-penicillamine (SNAP). Cultured human islets and INS-1 rat-derived insulin-secreting cells were transfected by an E1-deleted adenovirus carrying Cu/Zn SOD cDNA under the control of a cytomegalovirus (CMV) promoter (AdSOD). The viability of the cells was tested by the WST-1 assay (Roche, Indianapolis, Ind., USA). The AdSOD procedure allowed SOD activity to increase by twofold to threefold for 2 to 8 days following transfection. Adenovirus-driven SOD overexpression was associated with a significant reduction of SIN-1-induced cytotoxicity on human islets (69.9 +/- 10.5% protection at 200 micromol/l and 40.5 +/- 8.9% protection at 400 micromol/l) and INS-1 cells (82.2 8.8% protection at 200 micromol/l and 31.1 +/- 5.8% protection at 400 micromol/l). Protection against increasing doses of SNAP was AdSOD dose-dependent. Transfected islets released significantly more insulin than control islets in glucose-theophylline-stimulated conditions, without or following exposure to SNAP. We thus established that adenoviral-induced overexpression of Cu/Zn SOD can be beneficial to human islet endocrine function and resistance to nitric oxide cytotoxicity. These data could be relevant for the development of new strategies aimed at preventing NO-induced beta-cell damage in an islet transplantation setting.