Successful Islet Transplantation to Two Recipients From a Single Donor by Targeting Proinflammatory Cytokines in Mice

Aspects of the alternative host response to methacrylic acid containing biomaterials

Methacrylic acid (MAA)-based biomaterials promote a vascularized host response without the addition of exogenous factors such as cells or growth factors. We presume that materials containing MAA favor an alternative foreign body response, rather than the conventional fibrotic response. Here, we characterize selected aspects of the response to two different forms of MAA-a coating, which can be used to prevascularize the subcutaneous tissue for subsequent therapeutic cell delivery or an injectable hydrogel, which can be used to vascularize and deliver cells simultaneously. We show that the MAA-coating quickly vascularized the subcutaneous space compared to an uncoated silicone tube, and after 14 days of prevascularization, the tissue surrounding the MAA-coated tube presented fewer immune cells than the uncoated control. We also compared the host response to a MAA-PEG (polyethylene glycol) hydrogel at day 1, with pancreatic islets in immune-compromised SCID/bg mice and immune-competent Balb/c mice. The Balb/c mouse presented a more inflammatory response with increased IFN-γ production as compared to the SCID/bg. Together with previously published data, this work contributes to a further understanding of tissue responses to a biomaterial in different forms as used for cell delivery.

The Efficacy of the Hepatocyte Spheroids for Hepatocyte Transplantation

The safety and short-term efficacy of hepatocyte transplantation (HCTx) have been widely proven. However, issues such as reduced viability and/or function of hepatocytes, insufficient engraftment, and lack of a long-term effect have to be overcome for widespread application of HCTx. In this study, we evaluated hepatocyte spheroids (HSs), formed by self-aggregation of hepatocytes, as an alternative to hepatocytes in single-cell suspension. Hepatocytes were isolated from C57BL/6 J mice liver using a three-step collagenase perfusion technique and HSs were formed by the hanging drop method. After the spheroids formation, the HSs showed significantly higher mRNA expression of albumin, ornithine transcarbamylase, glucose-6-phosphate, alpha-1-antitrypsin, low density lipoprotein receptor, coagulation factors, and apolipoprotein E (ApoE) than 2 dimensional (2D)-cultured hepatocytes (p < 0.05). Albumin production by HSs was significantly higher than that by 2D-cultured hepatocytes (9.5 ± 2.5 vs 3.5 ± 1.8 μg/dL, p < 0.05). The HSs, but not single hepatocytes, maintained viability and albumin mRNA expression in suspension (92.0 ± 2.8% and 1.03 ± 0.09 at 6 h). HSs (3.6 × 10⁶ cells) or isolated hepatocytes (fSH, 3.6 × 10⁶ cells) were transplanted into the liver of ApoE knockout (KO-/-) mice via the portal vein. Following transplantation, serum ApoE concentration (ng/mL) of HS-transplanted mice (1w: 63.1 ± 56.7, 4w: 17.0 ± 10.9) was higher than that of fSH-transplanted mice (1 w: 33.4 ± 13.0, 4w: 13.7 ± 9.6). In both groups, the mRNA levels of pro-inflammatory cytokines (IL-6, IL-1β, TNF-α, MCP-1, and MIP-1β) were upregulated in the liver following transplantation; however, no significant differences were observed. Pathologically, transplanted HSs were observed as flat cell clusters in contact with the portal vein wall on day 7. Additionally, ApoE positive cells were observed in the liver parenchyma distant from the portal vein on day 28. Our results indicate that HS is a promising alternative to single hepatocytes and can be applied for HCTx.

Improvement of Islet Allograft Function Using Cibinetide, an Innate Repair Receptor Ligand

BACKGROUND

During intraportal pancreatic islet transplantation (PITx), early inflammatory reactions cause an immediate loss of more than half of the transplanted graft and potentiate subsequent allograft rejection. Previous findings suggest that cibinetide, a selective innate repair receptor agonist, exerts islet protective and antiinflammatory properties and improved transplant efficacy in syngeneic mouse PITx model. In a stepwise approach toward a clinical application, we have here investigated the short- and long-term effects of cibinetide in an allogeneic mouse PITx model.

METHODS

Streptozotocin-induced diabetic C57BL/6N (H-2) mice were transplanted with 320 (marginal) or 450 (standard) islets from BALB/c (H-2) mice via the portal vein. Recipients were treated perioperative and thereafter daily during 14 d with cibinetide (120 µg/kg), with or without tacrolimus injection (0.4 mg/kg/d) during days 4-14 after transplantation. Graft function was assessed using nonfasting glucose measurements. Relative gene expressions of proinflammatory cytokines and proinsulin of the graft-bearing liver were assessed by quantitative polymerase chain reaction. Cibinetide's effects on dendritic cell maturation were investigated in vitro.

RESULTS

Cibinetide ameliorated the local inflammatory responses in the liver and improved glycemic control immediately after allogeneic PITx and significantly delayed the onset of allograft loss. Combination treatment with cibinetide and low-dose tacrolimus significantly improved long-term graft survival following allogeneic PITx. In vitro experiments indicated that cibinetide lowered bone-marrow-derived-immature-dendritic cell maturation and subsequently reduced allogeneic T-cell response.

CONCLUSIONS

Cibinetide reduced the initial transplantation-related severe inflammation and delayed the subsequent alloreactivity. Cibinetide, in combination with low-dose tacrolimus, could significantly improve long-term graft survival in allogeneic PITx.

Reduction of marginal mass required for successful islet transplantation in a diabetic rat model using adipose tissue-derived mesenchymal stromal cells

BACKGROUND AIMS

Adipose tissue-derived mesenchymal stromal cells (AT-MSCs), widely known as multipotent progenitors, release several cytokines that support cell survival and repair. There are in vitro and in vivo studies reporting the regenerative role of AT-MSCs possibly mediated by their protective effects on functional islet cells as well as their capacity to differentiate into insulin-producing cells (IPCs).

METHODS

On such a basis, our goal in the present study was to use three different models including direct and indirect co-cultures and islet-derived conditioned medium (CM) to differentiate AT-MSCs into IPCs and to illuminate the molecular mechanisms of the beneficial impact of AT-MSCs on pancreatic islet functionality. Furthermore, we combined in vitro co-culture of islets and AT-MSCs with in vivo assessment of islet graft function to assess whether co-transplantation of islets with AT-MSCs can reduce marginal mass required for successful islet transplantation and prolong graft function in a diabetic rat model.

RESULTS

Our findings demonstrated that AT-MSCs are suitable for creating a microenvironment favorable for the repair and longevity of the pancreas β cells through the improvement of islet survival and maintenance of cell morphology and insulin secretion due to their potent properties in differentiation. Most importantly, hybrid transplantation of islets with AT-MSCs significantly promoted survival, engraftment and insulin-producing function of the graft and reduced the islet mass required for reversal of diabetes.

CONCLUSIONS

This strategy might be of therapeutic potential solving the problem of donor islet material loss that currently limits the application of allogeneic islet transplantation as a more widespread therapy for type 1 diabetes.

Positron Emission Tomography and Autoradiography of (18)F-Fluorodeoxyglucose Labeled Islets With or Without Warm Ischemic Stress in Portal Transplanted Rats

OBJECTIVE

The use of positron-emission tomography (PET) with (18)F-fluorodeoxyglucose (FDG) -labeled islets has been considered to be a potential modality to visualize and quantify early engraftment of islet transplantation. The objective of this study was to evaluate the early islets' survival of the FDG-labeled islets with or without warm ischemic stress in portal transplanted rats using PET and autoradiography.

METHODS

Islets were isolated from Lewis rat pancreata with or without 30-minute warm ischemia times (WITs). For islets' labeling, 300 islets were incubated with 3 MBq FDG for 60 minutes. FDG-labeled islets were transplanted into the liver via portal vein. In in vivo study, a PET study was scanned for 90 minutes and the FDG uptake was expressed as percentage of liver injection dose (ID). In ex vivo study, the liver was exposed for 30 minutes with single fluorescence autoradiography.

RESULTS

In the PET study, the percentage of liver ID of the islets without WIT was 27.8 and that of the WIT islets was 20.1 at the end of islet transplantation. At 90 minutes after transplantation, the percentage of liver ID was decreased to 14.7 in the islets without WIT and 10.1 in the WIT islets. In the autoradiogram, the number of hot spots was more obviously visualized in the liver transplanted without WIT islets than in the liver transplanted with WIT islets.

CONCLUSION

Almost 50% of the islets were immediately lost in both the islets without WIT and those with WIT transplantation in the early period. However, islet survival was 1.4 times higher in the islets without WIT than that in those with WIT in the early engraftment phase.

A Nonhematopoietic Erythropoietin Analogue, ARA 290, Inhibits Macrophage Activation and Prevents Damage to Transplanted Islets

BACKGROUND

Erythropoietin exerts anti-inflammatory, antiapoptotic, and cytoprotective effects in addition to its hematopoietic action. A nonhematopoietic erythropoietin analogue, ARA 290, has similar properties. The efficacy of pancreatic islet transplantation (PITx) is reduced due to islet damage that occurs during isolation and from the severe inflammatory reactions caused by the transplantation procedure. We investigated whether ARA 290 protects islets and ameliorates inflammatory responses following PITx thus improving engraftment.

METHODS

The effects of ARA 290 on pancreatic islets of C57BL/6J (H-2) mice and on murine macrophages were investigated using an in vitro culture model. As a marginal PITx, 185 islets were transplanted into the liver of streptozotocin-induced diabetic mice (H-2) via the portal vein. Recipients were given ARA 290 (120 μg/kg) intraperitoneally just before and at 0, 6, and 24 hours after PITx. Liver samples were obtained at 12 hours after PITx, and expression levels of proinflammatory cytokines were assessed.

RESULTS

ARA 290 protected islets from cytokine-induced damage and apoptosis. Secretion of pro-inflammatory cytokines (IL-6, IL-12, and TNF-α) from macrophages was significantly inhibited by ARA 290. After the marginal PITx, ARA 290 treatment significantly improved the blood glucose levels when compared to those of control animals (P < 0.001). Upregulation of monocyte chemoattractant protein-1, macrophage inflammatory protein-1β, IL-1β, and IL-6 messenger RNA expression within the liver was suppressed by ARA 290 treatment.

CONCLUSIONS

ARA 290 protected pancreatic islets from cytokine-induced damage and apoptosis and ameliorated the inflammatory response after PITx. ARA 290 appears to be a promising candidate for improvement of PITx.

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

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

The Impact of c-Fos/Activator Protein-1 Inhibition on Allogeneic Pancreatic Islet Transplantation

Unpreventable allograft rejection is one of the main problems in pancreatic islet transplantation (PIT). Therefore, it is imperative to develop a more effective immunosuppressive strategy. The blockade of transcription factors has been a central part of T cell-depleting immunosuppressive therapies, as typified by the use of calcineurin inhibitors. The inhibition of activator protein-1 (AP-1) offers a novel strategy for immunosuppression in PIT, although to date, no reports on the effects of AP-1 inhibition are available. In this study, we investigated the immunosuppressive effects of T-5224, a c-Fos/AP-1-selective inhibitor, on murine T cells activated by αCD3+αCD28 mAbs. T-5224 inhibited proliferation, CD25 up-regulation, and the production of IL-2 and interferon-γ. In addition, T-5224 blocked the nuclear translocation of c-Fos/AP-1 in activated murine T cells. In BALB/c (H-2(d) )-to-C57BL/6J (H-2(b) ) mouse PIT, the 2-week administration of T-5224 prolonged survival of 600 islet allografts in a dose-dependent manner. When combined with a 2-week low-dose tacrolimus, the T-5224 treatment markedly prolonged allograft survival to over 300 days, while the efficacy was indeterminate when transplanted islet allograft mass was reduced to 300. We conclude that the c-Fos/AP-1 inhibition by T-5224 is a potentially attractive strategy for allogeneic PIT.

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

OBJECTIVES

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

METHODS

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

RESULTS

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

CONCLUSIONS

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

Efficacy of DHMEQ, a NF-κB inhibitor, in islet transplantation: II. Induction DHMEQ treatment ameliorates subsequent alloimmune responses and permits long-term islet allograft acceptance

BACKGROUND

Long-term graft deterioration remains a major obstacle in the success of pancreatic islet transplantation (PITx). Antigen-independent inflammatory and innate immune responses strengthen subsequent antigen-dependent immunity; further, activation of nuclear factor (NF)-κB plays a key role during these responses. In this study, we tested our hypothesis that, by the inhibition of NF-κB activation, the suppression of these early responses after PITx could facilitate graft acceptance.

METHODS

Full major histocompatibility complex (MHC)-mismatched BALB/c (H-2) mice islets were transplanted into streptozotocin-induced diabetic C57BL/6 (B6: H-2) mice. The NF-κB inhibitor dehydroxymethylepoxyquinomicin (DHMEQ) was administered for either 3 or 14 days after PITx. To some PITx recipients, tacrolimus was also administered. Islet allograft survival, alloimmune responses, and in vitro effects of DHMEQ on dendritic cells (DCs) were assessed.

RESULTS

With a vehicle treatment, 600 islet allografts were promptly rejected after PITx. In contrast, 3-day treatment with DHMEQ, followed by 2-week treatment with tacrolimus, allowed permanent acceptance of islet allografts. The endogenous danger-signaling molecule high mobility group complex 1 (HMGB1) was elevated in sera shortly after PITx, whereas DHMEQ administration abolished this elevation. DHMEQ suppressed HMGB1-driven cellular activation and proinflammatory cytokine secretion in mouse bone marrow-derived DCs and significantly reduced the capacity of DCs to prime allogeneic T-cell proliferation in vitro. Finally, the DHMEQ plus tacrolimus regimen reverted the diabetic state with only 300 islet allografts.

CONCLUSIONS

Inhibition of NF-κB activation by DHMEQ shortly after PITx suppresses HMGB1, which activates DCs and strengthens the magnitude of alloimmune responses; this permits long-term islet allograft acceptance, even in case of fewer islet allografts.

Mesenchymal stem cells as a gene delivery vehicle for successful islet transplantation

PURPOSE

To evaluate the efficacy of human bone marrow-derived mesenchymal stem cells (hBMSCs) as gene delivery vehicles to simultaneously express human hepatocyte growth factor (HGF) and interleukin 1 receptor antagonist (IL-1Ra) to improve the outcome of islet transplantation.

METHODS

Morphology and islet-binding affinity of hBMSCs were checked by microscope. The expression of target genes and endogenous genes was determined by ELISA. Protection of islets by hBMSCs was evaluated in vitro by Calcein-AM/Propidium Iodide staining and in vivo by allogeneic islet transplantation study. Function and revascularization of islets was evaluated by immune fluorescence study.

RESULTS

Non-donor-specific hBMSCs showed strong binding affinity to human islets and protected viability and function. Transduction of hBMSCs with adenovirus encoding human HGF and human IL-1Ra (Adv-hHGF-hIL-1Ra) prior to co-culturing with islets further protected from apoptotic cell death, helped maintain 3D structures and morphology, and enhanced insulin secretion. Transplantation of human islets reconstituted with Adv-hHGF-hIL-1Ra transduced hBMSCs under the kidney capsule of streptozotocin-induced diabetic non-obese diabetic/severe combined immunodeficient (NOD-SCID) mice reversed diabetes by reducing blood glucose levels to ≤ 200 mg/dL for up to 15 weeks and reduced the number of islets required to achieving normoglycemia. Blood glucose levels of mice transplanted with islets alone reversed to ≥ 500 mg/dL 4 weeks post-transplantation.

CONCLUSIONS

Results indentified hBMSCs as effective gene delivery vehicles to improve the outcome of islet transplantation.

Bilirubin protects grafts against nonspecific inflammation-induced injury in syngeneic intraportal islet transplantation

Nonspecific inflammatory response is the major cause for failure of islet grafts at the early phase of intraportal islet transplantation (IPIT). Bilirubin, a natural product of heme catabolism, has displayed anti-oxidative and anti-inflammatory activities. The present study has demonstrated that bilirubin protected islet grafts by inhibiting nonspecific inflammatory response in a syngeneic rat model of IPIT. The inflammation-induced cell injury was mimicked by exposing cultured rat insulinoma INS-1 cells to cytokines (IL-1β, TNF-α and IFN-γ) in in vitro assays. At appropriate lower concentrations, bilirubin significantly attenuated the reduced cell viability and enhanced cell apoptosis induced by cytokines, and protected the insulin secretory function of INS-1 cells. Diabetic inbred male Lewis rats induced by streptozotocin underwent IPIT at different islet equivalents (IEQs) (optimal dose of 1000, and suboptimal doses of 750 or 500), and bilirubin was administered to the recipients every 12 h, starting from one day before transplantation until 5 days after transplantation. Administration of bilirubin improved glucose control and enhanced glucose tolerance in diabetic recipients, and reduced the serum levels of inflammatory mediators including IL-1β, TNF-α, soluble intercellular adhesion molecule 1, monocyte chemoattractant protein-1 and NO, and inhibited the infiltration of Kupffer cells into the islet grafts, and restored insulin-producing ability of transplanted islets.

Surgical protocol involving the infusion of paramagnetic microparticles for preferential incorporation within porcine islets

INTRODUCTION

Despite significant advances, widespread applicability of islet cell transplantation remains elusive. Refinement of current islet isolation protocols may improve transplant outcomes. Islet purification by magnetic separation has shown early promise. However, surgical protocols must be optimized to maximize the incorporation of paramagnetic microparticles (MP) within a greater number of islets. This study explores the impact of MP concentration and infusion method on optimizing MP incorporation within islets.

METHODS

Five porcine pancreata were procured from donors after cardiac death. Splenic lobes were isolated and infused with varying concentrations of MP (8, 16, and 32 × 10(8) MP/L of cold preservation solution) and using one of two delivery techniques (hanging bag versus hand-syringe). After procurement and infusion, pancreata were stored at 0°C to 4°C during transportation (less than 1 hour), fixed in 10% buffered formalin, and examined by standard magnetic resonance imaging (MRI) and histopathology.

RESULTS

T2*-weighted MRI showed homogeneous distribution of MP in all experimental splenic lobes. In addition, histologic analysis confirmed that MP were primarily located within the microvasculature of islets (82% to 85%), with few MP present in acinar tissue (15% to 18%), with an average of five to seven MP per islet (within a 5-μm thick section). The highest MP incorporation was achieved at a concentration of 16 × 10(8) MP/L using the hand-syringe technique.

CONCLUSION

This preliminary study suggests that optimization of a surgical protocol, MP concentrations, and applied infusion pressures may enable more uniform distribution of MP in the porcine pancreas and better control of MP incorporation within islets. These results may have implications in maximizing the efficacy of islet purification by magnetic separation.

Oxygenation of the portal vein by intraperitoneal administration of oxygenated perfluorochemical improves the engraftment and function of intraportally transplanted islets

OBJECTIVES

One of the major obstacles for successful intraportal islet transplantation (IPIT) is early graft loss due to hypoxia. We therefore examined the effect of intraperitoneal oxygenated perfluorochemical (PFC) on oxygenation of the portal vein with respect to islet engraftment and function after IPIT in a rat model.

METHODS

First, we measured the oxygen tension and saturation in the portal vein of Lewis rats before and after intraperitoneal injection of oxygenated PFC. Second, blood glucose levels, glucose tolerance, and the number of surviving islets were measured after IPIT with oxygenated PFC (group 1), with PFC saturated by nitrogen (group 2), and without any PFC (control).

RESULTS

Both oxygen tension and saturation in the portal vein significantly increased after injection of oxygenated PFC. In IPIT, the functional success rate in group 1 was 83.3%, compared with 16.7% in group 2 and 16.7% in the control. On the 28th posttransplantation day, the number of engrafted islets in the liver in group 1 (12.8 [SD, 3.3]) was significantly higher than that in group 2 (4.7 [SD, 3.0]) and in the control group (6.5 [SD, 3.3]).

CONCLUSIONS

We clearly demonstrated the effect of intraperitoneal oxygenated PFC on oxygenation of the portal vein, resulting in better IPIT outcomes.

Interleukin-targeted therapy for metabolic syndrome and type 2 diabetes

Interleukin-1β Interleukin-1β (IL-1β) is a key regulator of the body's inflammatory response and is produced after infection, injury, and an antigenic challenge. Cloned in 1984, the single polypeptide IL-1β has been shown to exert numerous biological effects. It plays a role in various diseases, including autoimmune diseases such as rheumatoid arthritis, inflammatory bowel diseases, and Type 1 diabetes, as well as in diseases associated with metabolic syndrome such as atherosclerosis, chronic heart failure, and Type 2 diabetes. The macrophage is the primary source of IL-1β, but epidermal, epithelial, lymphoid, and vascular tissues also synthesize IL-1. Recently, IL-1β production and secretion have also been reported from pancreatic islets. Insulin-producing β-cells β-cells within the pancreatic islets are specifically prone to IL-β-induced destruction and loss of function. Macrophage-derived IL-1β production in insulin-sensitive organs leads to the progression of inflammation inflammation and induction of insulin resistance in obesity. This chapter explains the mechanisms involved in the inflammatory response during diabetes progression with specific attention to the IL-1β signal effects influencing insulin action and insulin secretion insulin secretion . We highlight recent clinical studies, rodent and in vitro experiments with isolated islets using IL-1β as a potential target for the therapy of Type 2 diabetes.

Generation of rat pancreas in mouse by interspecific blastocyst injection of pluripotent stem cells

The complexity of organogenesis hinders in vitro generation of organs derived from a patient's pluripotent stem cells (PSCs), an ultimate goal of regenerative medicine. Mouse wild-type PSCs injected into Pdx1(-/-) (pancreatogenesis-disabled) mouse blastocysts developmentally compensated vacancy of the pancreatic "developmental niche," generating almost entirely PSC-derived pancreas. To examine the potential for xenogenic approaches in blastocyst complementation, we injected mouse or rat PSCs into rat or mouse blastocysts, respectively, generating interspecific chimeras and thus confirming that PSCs can contribute to xenogenic development between mouse and rat. The development of these mouse/rat chimeras was primarily influenced by host blastocyst and/or foster mother, evident by body size and species-specific organogenesis. We further injected rat wild-type PSCs into Pdx1(-/-) mouse blastocysts, generating normally functioning rat pancreas in Pdx1(-/-) mice. These data constitute proof of principle for interspecific blastocyst complementation and for generation in vivo of organs derived from donor PSCs using a xenogenic environment.

Induction of chimerism permits low-dose islet grafts in the liver or pancreas to reverse refractory autoimmune diabetes

OBJECTIVE

To test whether induction of chimerism lowers the amount of donor islets required for reversal of diabetes and renders the pancreas a suitable site for islet grafts in autoimmune diabetic mice.

RESEARCH DESIGN AND METHODS

The required donor islet dose for reversal of diabetes in late-stage diabetic NOD mice after transplantation into the liver or pancreas was compared under immunosuppression or after induction of chimerism. Recipient mice were monitored for blood glucose levels and measured for insulin-secretion capacity. Islet grafts were evaluated for beta-cell proliferation, beta-cell functional gene expression, and revascularization.

RESULTS

With immunosuppression, transplantation of 1,000, but not 600, donor islets was able to reverse diabetes when transplanted into the liver, but transplantation of 1,000 islets was not able to reverse diabetes when transplanted into the pancreas. In contrast, after induction of chimerism, transplantation of as few as 100 donor islets was able to reverse diabetes when transplanted into either the liver or pancreas. Interestingly, when lower doses (50 or 25) of islets were transplanted, donor islets in the pancreas were much more effective in reversal of diabetes than in the liver, which was associated with higher beta-cell replication rate, better beta-cell functional gene expression, and higher vascular density of graft islets in the pancreas.

CONCLUSIONS

Induction of chimerism not only provides immune tolerance to donor islets, but also markedly reduces the required amount of donor islets for reversal of diabetes. In addition, this process renders the pancreas a more superior site than the liver for donor islets in autoimmune mice.

Biomolecular surface engineering of pancreatic islets with thrombomodulin

Islet transplantation has emerged as a promising treatment for Type 1 diabetes, but its clinical impact remains limited by early islet destruction mediated by prothrombotic and innate inflammatory responses elicited upon transplantation. Thrombomodulin (TM) acts as an important regulator of thrombosis and inflammation through its capacity to channel the catalytic activity of thrombin towards generation of activated protein C (APC), a potent anticoagulant and anti-inflammatory agent. We herein describe a novel biomolecular strategy for re-engineering the surface of pancreatic islets with TM. A biosynthetic approach was employed to generate recombinant human TM (rTM) bearing a C-terminal azide group, which facilitated site-specific biotinylation of rTM through Staudinger ligation. Murine pancreatic islets were covalently biotinylated through targeting of cell surface amines and aldehydes and both islet viability and the surface density of streptavidin were maximized through optimization of biotinylation conditions. rTM was immobilized on islet surfaces through streptavidin-biotin interactions, resulting in a nearly threefold increase in the catalytic capacity of islets to generate APC.

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

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

Marginal mass islet transplantation with autologous mesenchymal stem cells promotes long-term islet allograft survival and sustained normoglycemia

Allogeneic islet transplantation is an option to treat diabetes however there are obstacles that are limiting its clinical use. We have examined whether mesenchymal stem cells (MSC) improve islet graft survival and whether such therapy allows for better graft acceptance with reduced requirement for immunosuppression. In vitro-expanded syngeneic bone marrow-derived MSC were co-transplanted with islets into omental pouch in a rat model of streptozotocin-induced diabetes. Marginal mass syngeneic islet transplantation into the omentum with MSC promoted sustained normoglycemia. Interestingly, allogeneic islets +MSC, but not islets alone, with short-term use of immunosuppression enhanced long-term islet graft survival, insulin expression in the grafts and induced normal serum insulin levels and normoglycemia. T cells from recipients transplanted with allogeneic islets +MSC produced low levels of IFN-gamma and TNF-alpha upon ex-vivo activation, and this transplantation protocol promoted the generation of IL-10-secreting CD4(+) T cells. These data encourage further preclinical and eventually, clinical MSC-based islet transplantation to improve the outcome of allogeneic islet transplantation in the treatment of diabetes.

Clinical islet transplantation in Japan

INTRODUCTION

The results of clinical islet transplantation in Japan are, here in, reported and discussed its efficacy and problems.

METHODS

Since the first islet transplantation was performed in 2004, 65 islet isolations and 34 islet transplantations to 18 type 1 diabetic patients have been performed in Japan.

RESULTS

Following islet transplantation, patients experienced decreased insulin requirements and lower hemoglobin A1C levels, and positive serum C-peptide levels. All patients achieved stabilized blood glucose levels and the disappearance of hypoglycemic unawareness. Although three patients achieved insulin independency for a limited period, persistent islet graft function was difficult to maintain. Overall islet graft survival was 86.5% at 6 months, 78.7% at 1 year, and 62.9% at 2 years after the first islet transplantation. In our institution, we carried out 23 islet isolations and six islet transplantations to four patients. Although insulin independency was not achieved, all patients showed a disappearance of hypoglycemic unawareness.

CONCLUSIONS

Using data from the Japanese Trial of Islet Transplantation, the effectiveness of islet transplantation was shown even when using the pancreata from non-heart-beating donors. Although there are a number of problems to be solved and further improvement is needed, we can state that the introduction of clinical islet transplantation offers hope for type 1 diabetic patients.

Thrombosis and inflammation in intraportal islet transplantation: a review of pathophysiology and emerging therapeutics

With the inception of the Edmonton Protocol, intraportal islet transplantation (IPIT) has re-emerged as a promising cell-based therapy for type 1 diabetes. However, current clinical islet transplantation remains limited, in part, by the need to transplant islets from 2-4 donor organs, often through several separate infusions, to reverse diabetes in a single patient. Results from clinical islet transplantation and experimental animal models now indicate that the majority of transplanted islets are destroyed in the immediate post-transplant period, a process largely facilitated by deleterious inflammatory responses triggered by islet-derived procoagulant and proinflammatory mediators. Herein, mechanisms that underlie the pathophysiology of thrombosis and inflammation in IPIT are reviewed, and emerging approaches to improve islet engraftment through attenuation of inflammatory responses are discussed.

Activated effector and memory T cells contribute to circulating sCD30: potential marker for islet allograft rejection

T-cell activation up-regulates CD30 resulting in an increase in serum soluble CD30 (sCD30). CD4+ T cells, a major source for sCD30, play a significant role in the pathogenesis of rejection. In this study, sCD30 was measured pre- and posttransplant in mouse islet allograft models and human islet allograft recipients. sCD30 was measured by ELISA in diabetic C57BL/6, CD4Knockout (KO) and CD8KO islet allograft recipients. sCD30 increased significantly prior to rejection (1.8 +/- 1 days) in 80% of allograft recipients. Sensitization with donor splenocytes, or a second graft, further increased sCD30 (282.5 +/- 53.5 for the rejecting first graft vs. 374.6 +/- 129 for the rejecting second graft) prior to rejection suggesting memory CD4+ T cells contribute to sCD30. CD4KO failed to reject islet allograft and did not demonstrate sCD30 increase. CD8KO showed elevated (227 +/- 107) sCD30 (1 day) prior to rejection. High pretransplant sCD30 (>20 U/ml) correlated with poor outcome in human islet allograft recipients. Further, increase in sCD30 posttransplant preceded (3-4 months) loss of islet function. We conclude that sCD30 is released from activated CD4 T cells prior to islet allograft rejection and monitoring sCD30 can be a valuable adjunct in the follow-up of islet transplant recipients.

Glucocorticoids reduce pro-inflammatory cytokines and tissue factor in vitro and improve function of transplanted human islets in vivo

Factors that upregulate the inflammatory status of islets probably contribute to detrimental processes leading to islet loss and impaired post-transplant function. Glucocorticoids have the potential to counteract inflammation and thus improve islet quality and function. However, glucocorticoids have diabetogenic properties and are known to hamper islet function in vivo. We examined the effect of glucocorticoids on human islets in vitro and in vivo after 48 h of exposure to different concentrations of methylprednisolone. Protein and/or mRNA levels of insulin, interleukin (IL)-8, macrophage chemoattractant protein (MCP)-1, tissue factor (TF), and IL-10 were assessed by enzyme immunosorbent assay and real time quantitative reverse transcription-polymerase chain reaction. Viability was assessed with fluorescein diacetate-propidium iodide staining, adenosine triphosphate (ATP) content and caspase activity. Six-hundred islet equivalents (IEQ) were transplanted to severe combined immunodeficiency disease mice and graft function assessed by glucose measurements and intraperitoneal glucose tolerance tests. Glucocorticoids reduce mRNA and protein levels of TF, MCP-1 and IL-8, and enhance ATP content. Insulin secretion was initially inhibited; however, after 7 days in culture, it was superior to controls. Islets exposed to methylprednisolone cured diabetic mice more effectively than control islets. In conclusion, glucocorticoids have potent anti-inflammatory properties on human islets without permanent effects on insulin metabolism. Brief glucocorticoid exposure improves function of transplanted human islets in vivo.

Challenges and emerging technologies in the immunoisolation of cells and tissues

Protection of transplanted cells from the host immune system using immunoisolation technology will be important in realizing the full potential of cell-based therapeutics. Microencapsulation of cells and cell aggregates has been the most widely explored immunoisolation strategy, but widespread clinical application of this technology has been limited, in part, by inadequate transport of nutrients, deleterious innate inflammatory responses, and immune recognition of encapsulated cells via indirect antigen presentation pathways. To reduce mass transport limitations and decrease void volume, recent efforts have focused on developing conformal coatings of micron and submicron scale on individual cells or cell aggregates. Additionally, anti-inflammatory and immunomodulatory capabilities are being integrated into immunoisolation devices to generate bioactive barriers that locally modulate host responses to encapsulated cells. Continued exploration of emerging paradigms governed by the inherent challenges associated with immunoisolation will be critical to actualizing the clinical potential of cell-based therapeutics.