Strategic opportunities in clinical islet transplantation

Engineered extracellular vesicles from human skin cells induce pro-β-cell conversions in pancreatic ductal cells

Direct nuclear reprogramming has the potential to enable the development of β cell replacement therapies for diabetes that do not require the use of progenitor/stem cell populations. However, despite their promise, current approaches to β cell-directed reprogramming rely heavily on the use of viral vectors. Here we explored the use of extracellular vesicles (EVs) derived from human dermal fibroblasts (HDFs) as novel non-viral carriers of endocrine cell-patterning transcription factors, to transfect and transdifferentiate pancreatic ductal epithelial cells (PDCs) into hormone-expressing cells. Electrotransfection of HDFs with expression plasmids for Pdx1, Ngn3, and MafA (PNM) led to the release of EVs loaded with PNM at the gene, mRNA, and protein level. Exposing PDC cultures to PNM-loaded EVs led to successful transfection and increased PNM expression in PDCs, which ultimately resulted in endocrine cell-directed conversions based on the expression of insulin/c-peptide, glucagon, and glucose transporter 2 (Glut2). These findings were further corroborated in vivo in a mouse model following intraductal injection of PNM- vs sham-loaded EVs. Collectively these findings suggest that dermal fibroblast-derived EVs could potentially serve as a powerful platform technology for the development and deployment of non-viral reprogramming-based cell therapies for insulin-dependent diabetes.

Generation of a Beta-Cell Transplant Animal Model of Diabetes Using CRISPR Technology

Since insulin deficiency results from pancreatic beta-cell destruction, all type 1 and most type 2 diabetes patients eventually require life-long insulin injections. Insulin gene synthesis could also be impaired due to insulin gene mutations as observed in diabetic patients with MODY 10. At this point, insulin gene therapy could be very effective to recompense insulin deficiency under these circumstances. For this reason, an HIV-based lentiviral vector carrying the insulin gene under the control of insulin promoter (LentiINS) was generated, and its therapeutic efficacy was tested in a beta-cell transplant model lacking insulin produced by CRISPR/Cas9-mediated genetically engineered pancreatic beta cells. To generate an insulin knockout beta-cell transplant animal model of diabetes, a dual gene knockout plasmid system involving CRISPR/Cas9 was transfected into a mouse pancreatic beta cell line (Min6). Fluorescence microscopy and antibiotic selection were utilized to select the insulin gene knockout clones. Transplantation of the genetically engineered pancreatic beta cells under the kidney capsule of STZ-induced diabetic rats revealed LentiINS- but not LentiLacZ-infected Ins2KO cells transiently reduced hyperglycemia similar to that of MIN6 in diabetic animals. These results suggest LentiINS has the potential to functionally restore insulin production in an insulin knockout beta-cell transplant animal model of diabetes.

Fabrication of functional rat pseudo-islets after cryopreservation of pancreatic islets or dispersed islet cells

Dispersed single cells from pancreatic islets can configure the three-dimensional islet-like architecture (pseudo-islets) with insulin secretion potential and controllable size through their aggregation property. The present study was designed to investigate whether cryopreservation of islets or islet cells can contribute to the efficient pseudo-islet fabrication in the rat model. In control group (CT), islet single cells were prepared by trypsin digestion of 50-400-µm ø fresh control islets, and then cultured for 3 days in the U-bottom microwell to fabricate pseudo-islets. In vitrification-warming group (VW), islet single cells were prepared from postwarm islets cryopreserved by vitrification on nylon mesh device, and then cultured for 3 days. In freezing group (FR), islet single cells originated from fresh islets were subjected to a conventional Bicell® freezing, and postthaw cells were cultured for 3 days. To generate 1 islet equivalent pseudo-islets (150 µm ø) by the sphere culture, 1250 CT cells, 1250 VW cells, and 1500 FR cells were seeded to each microwell. The viability of the pseudo-islets was comparable among the three groups (93.9%-96.9%). Furthermore, the insulin secretion assay showed that those pseudo-islets responded sufficiently to the high glucose stimulation. Immunostaining for insulin and glucagon showed that the endocrine cell arrangement of those pseudo-islets is similar to that of native and isolated islets. These islets/pseudo-islets had the β-cells in core and the α-cells in mantle, which was typical characteristic of the rodent islets. However, some clusters of α-cells were observed inside the FR pseudo-islets. Interestingly, the VW pseudo-islets had significantly fewer α-cells than the CT or FR pseudo-islets. These results suggest that the sphere culture of islet cells is useful tool to generate the pseudo-islets with the customized size and normal functionality, even after islet cryopreservation.

Nanomedicine-Based Strategies for Diabetes: Diagnostics, Monitoring, and Treatment

Traditional methods for diabetes management require constant and tedious glucose monitoring (GM) and insulin injections, impacting quality of life. The global diabetic population is expected to increase to 439 million, with approximately US$490 billion in healthcare expenditures by 2030, imposing a significant burden on healthcare systems worldwide. Recent advances in nanotechnology have emerged as promising alternative strategies for the management of diabetes. For example, implantable nanosensors are being developed for continuous GM, new nanoparticle (NP)-based imaging approaches that quantify subtle changes in β cell mass can facilitate early diagnosis, and nanotechnology-based insulin delivery methods are being explored as novel therapies. Here, we provide a holistic summary of this rapidly advancing field compiling all aspects pertaining to the management of diabetes.

Long-term outcome of islet transplantation on insulin-dependent diabetes mellitus: An observational cohort study

AIMS/INTRODUCTION

To investigate the long-term efficacy and safety of islet transplantation (ITx) compared with multiple daily injections (MDI) or continuous subcutaneous insulin infusion (CSII).

MATERIALS AND METHODS

Among 619 patients diagnosed as insulin-dependent diabetes mellitus or type 1 diabetes at Kyoto University, Kyoto, Japan, seven patients were selected as the ITx group and 26 age-matched patients with no endogenous insulin secretion were selected as the MDI/CSII group. Hemoglobin A1c, aspartate aminotransferase/alanine aminotransferase (AST/ALT) and creatinine were assessed retrospectively at 1, 2, 5 and 10 years for both groups; serum C-peptide immunoreactivity was assessed for the ITx group. Major clinical events were also assessed.

RESULTS

Hemoglobin A1c improvement in ITx was significant at 1 year (8.4% [7.8-9.9%] at baseline to 7.1% [6.3-7.4%] in ITx vs 8.2% [7.4-9.8%] at baseline to 8.1% [7.3-9.5%] in MDI/CSII, P < 0.01 between groups), and was maintained at 2 years (7.4% [6.3-8.2%] vs 8.4% [7.4-9.6%], P = 0.11). The increase of stimulated C-peptide immunoreactivity was significant at 1 year (0.57 ng/mL [0.26-0.99 ng/mL], P < 0.05 from baseline) and 2 years (0.43 ng/mL [0.19-0.67 ng/mL], P < 0.05), although it became insignificant thereafter. There was no significant difference in AST/ALT or creatinine at 10 years, although a transient AST/ALT elevation was observed in ITx. In regard to clinical events, the occurrence of severe hypoglycemia was 14% vs 31% (relative risk 0.46, P = 0.64), that of infectious disease was 43% vs 12% (relative risk 3.71, P = 0.09) and digestive symptoms was 43% vs 7.7% (relative risk 5.57, P = 0.05) in ITx vs MDI/CSII, respectively. No patient died in either group.

CONCLUSIONS

The present findings showed that ITx was considered to contribute to the reduction of hypoglycemia and better glycemic control with tolerable, but attention-requiring, risks over a period of 10 years compared with MDI/CSII.

Supplementary cryoprotective effect of carboxylated ε-poly-l-lysine during vitrification of rat pancreatic islets

This study was designed to investigate whether cryosurvival of rat pancreatic islets can be improved by carboxylated ε-poly-l-lysine (CPLL). Islets isolated from Wistar × Brown-Norway F1 rats (101-200 μm in diameter) were cryopreserved in three vitrification solutions containing ethylene glycol (EG; 30%, v/v) and CPLL (0%, 10%, or 20%, v/v) by Cryotop^® protocol (10 islets per device). The post-warm survival rate of the islets vitrified in the presence of 20% CPLL (74%), assessed by FDA/PI double staining, was higher than those in 0% and 10% CPLL (65% and 66%, respectively). Decreased EG concentrations (10% and 20%) in the presence of 20% CPLL resulted in impaired post-warm islet survival rates (50% and 64%, respectively). Value of stimulus index (SI) for 20 mM/3 mM glucose-stimulated insulin secretion was 4.1 in islets vitrified-warmed in the presence of 30% EG and 20% CPLL, which was comparable with those in fresh control islets and vitrified islets in 30% EG alone (4.1 and 4.4, respectively). A large number of islets (50 islets per device) could be cryopreserved in the presence of 30% EG and 20% CPLL by using nylon mesh as the device, without considerable loss of post-warm survival (68%) and SI value (3.7). In conclusion, supplementation of antifreeze 20% CPLL was effective in improving the post-warm survival of isolated rat pancreatic islets when vitrification solution containing 30% EG was used.

Carnosine protects pancreatic beta cells and islets against oxidative stress damage

Islet transplantation is a valid therapeutic option for type 1 diabetes treatment. However, in this procedure one of the major problems is the oxidative stress produced during pancreatic islet isolation. The aim of our study was to evaluate potential protective effects of L-carnosine and its isomer D-carnosine against oxidative stress. We evaluated the carnosine effect on cell growth, cell death, insulin production, and the main markers of oxidative stress in rat and murine stressed beta cell lines as well as in human pancreatic islets. Both isomers clearly inhibited hydrogen peroxide induced cytotoxicity, with a decrease in intracellular reactive oxygen and nitrogen species, prevented hydrogen peroxide induced apoptosis/necrosis, nitrite production, and reduced glucose-induced insulin secretion. In addition, NF-κB expression/translocation and nitrated protein induced in stressed cells was significantly reduced. Furthermore, both isomers improved survival and function, and decreased reactive oxygen and nitrogen species, and nitrite and nitrotyrosine production in human islets cultured for 1, 3, and 7 days. These results seem to indicate that both L and D-carnosine have a significant cytoprotective effect by reducing oxidative stress in beta cell lines and human islets, suggesting their potential use to improve islet survival during the islet transplantation procedure.

Tissue-engineering approaches in pancreatic islet transplantation

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

Cell Loss during Pseudoislet Formation Hampers Profound Improvements in Islet Lentiviral Transduction Efficacy for Transplantation Purposes

Islet transplantation is a promising treatment in type 1 diabetes, but the need for chronic immunosuppression is a major hurdle to broad applicability. Ex vivo introduction of agents by lentiviral vectors—improving β-cell resistance against immune attack—is an attractive path to pursue. The aim of this study was to investigate whether dissociation of islets to single cells prior to viral infection and reaggregation before transplantation would improve viral transduction efficacy without cytotoxicity. This procedure improved transduction efficacy with a LV-pWPT-CMV-EGFP construct from 11.2 ± 4.1% at MOI 50 in whole islets to 80.0 ± 2.8% at MOI 5. Viability (as measured by Hoechst/PI) and functionality (as measured by glucose challenge) remained high. After transplantation, the transfected pseudoislet aggregates remained EGFP positive for more than 90 days and the expression of EGFP colocalized primarily with the insulin-positive β-cells. No increased vulnerability to immune attack was observed in vitro or in vivo. These data demonstrate that dispersion of islets prior to lentiviral transfection and reaggregation prior to transplantation is a highly efficient way to introduce genes of interest into islets for transplantation purposes in vitro and in vivo, but the amount of β-cells needed for normalization of glycemia was more than eightfold higher when using dispersed cell aggregates versus unmanipulated islets. The high price to pay to reach stable and strong transgene expression in islet cells is certainly an important cell loss.

Inactivation of p27kip1 Promoted Nonspecific Inflammation by Enhancing Macrophage Proliferation in Islet Transplantation

Islet transplantation suffers from low efficiency caused by nonspecific inflammation-induced graft loss after transplantation. This study reports increased islet loss and enhanced inflammatory response in p27-deficient mice (p27-/-) and proposes a possible mechanism. Compared with wild type, p27-/- mice showed more severe functional injury of islet, with increased serum levels of inflammatory cytokines IL-1 and TNF-α, inducing macrophage proliferation. Furthermore, the increased number, proapoptotic proteins, and nuclear factor-kappa b (NF-κB) phosphorylation status of the infiltrating macrophages were accompanied by increased TNF-α mRNA level of islet graft site in p27-/- mice. Moreover, in vitro, we found that macrophages were still activated and cocultured with islet and promoted islet loss even blocking the direct effect of TNF-α on islets. Malondialdehyde (MDA, an end product of lipid peroxidation) in islet and media were increased after cocultured with macrophages. p27 deficiency also increased macrophage proliferation and islet injury. Therefore, p27 inactivation promotes injury islet graft loss via the elevation of proliferation and inflammatory cytokines secretion in infiltrating macrophages which induced nonspecific inflammation independent of TNF-α/nuclear factor-kappa b pathway. This potentially represents a promising therapeutic target in improving islet graft survival.

Direct comparison of Cryotop® vitrification and Bicell® freezing on recovery of functional rat pancreatic islets

Two protocols, Bicell^® freeze-thawing and Cryotop^® vitrification-warming, were compared for suitability in cryopreserving rat pancreatic islets (101-150 μm in mean diameter). Immediate survival rates of post-thaw and post-warm islets (50 and 57%, respectively), assessed by FDA/PI double staining, were lower than that of fresh control islets (90%). Most of the PI-positive dead cells were detected in peripheral area of post-warm islets, and were removed after subsequent 24 h culture (survival rate; 85% vs 59% in post-thaw islets). Quantitative PCR analysis showed that Bicell^® freeze-thawing compromised expression of genes relating to β-cell function (Pdx1 and Glut2), but not to one of apoptotic pathways (Bax/Bcl2 ratio). Expression of these genes was maintained in islets before and after the Cryotop^® vitrification-warming. Values of stimulus index (SI) for 20 mM/3 mM glucose-stimulated insulin secretion were 6.7, 1.9 and 3.9 in fresh control, post-thaw and post-warm islets, respectively. The SI values after 24 h culture were 4.1, 1.9 and 3.1, respectively. Larger islets (>150 μm in diameter) had comparable survival rates, but lower SI values after Cryotop^® vitrification-warming when compared to smaller counterparts. These results suggest that rat pancreatic islets can be cryopreserved by Cryotop^® vitrification-warming rather than Bicell^® freeze-thawing, without considerable loss of in vitro β-cell function.

Progress in islet transplantation in patients with type 1 diabetes mellitus

More than 500 patients with type 1 diabetes mellitus have now received islet transplants at over 50 institutions worldwide in the past 5 years. Rates of insulin independence at 1 year with current protocols are impressive. However, inexorable decay of islet function over time indicates that there are many opportunities for improvement. Improved control of glycosylated hemoglobin and reduced risk of recurrent hypoglycemia are seen as important benefits of islet transplantation, irrespective of the status regarding insulin independence. For the use of islet transplantation to expand it is essential that the donor-to-recipient ratio be reliably reduced to 1 : 1. Enormous opportunities lie ahead for the development of successful living donor islet transplantation, single donor protocols, improved engraftment, islet proliferation in vitro and in the recipient, alternative islet sources, and novel tolerizing drugs. With these emerging opportunities, islet transplantation may expand to include more patients with type 1 diabetes, including children, and will not be restricted to the most unstable forms of the disease, as it is today.

Stem Cells and Regenerative Medicine: Myth or Reality of the 21th Century

Since the 1960s and the therapeutic use of hematopoietic stem cells of bone marrow origin, there has been an increasing interest in the study of undifferentiated progenitors that have the ability to proliferate and differentiate into various tissues. Stem cells (SC) with different potency can be isolated and characterised. Despite the promise of embryonic stem cells, in many cases, adult or even fetal stem cells provide a more interesting approach for clinical applications. It is undeniable that mesenchymal stem cells (MSC) from bone marrow, adipose tissue, or Wharton's Jelly are of potential interest for clinical applications in regenerative medicine because they are easily available without ethical problems for their uses. During the last 10 years, these multipotent cells have generated considerable interest and have particularly been shown to escape to allogeneic immune response and be capable of immunomodulatory activity. These properties may be of a great interest for regenerative medicine. Different clinical applications are under study (cardiac insufficiency, atherosclerosis, stroke, bone and cartilage deterioration, diabetes, urology, liver, ophthalmology, and organ's reconstruction). This review focuses mainly on tissue and organ regeneration using SC and in particular MSC.

Regulation of the JNK3 signaling pathway during islet isolation: JNK3 and c-fos as new markers of islet quality for transplantation

Stress conditions generated throughout pancreatic islet processing initiate the activation of pro-inflammatory pathways and beta-cell destruction. Our goal is to identify relevant and preferably beta-specific markers to assess the activation of beta-cell stress and apoptotic mechanisms, and therefore the general quality of the islet preparation prior to transplantation. Protein expression and activation were analyzed by Western blotting and kinase assays. ATP measurements were performed by a luminescence-based assay. Oxygen consumption rate (OCR) was measured based on standard protocols using fiber optic sensors. Total RNA was used for gene expression analyzes. Our results indicate that pancreas digestion initiates a potent stress response in the islets by activating two stress kinases, c-Jun N-terminal Kinase (JNK) and p38. JNK1 protein levels remained unchanged between different islet preparations and following culture. In contrast, levels of JNK3 increased after islet culture, but varied markedly, with a subset of preparations bearing low JNK3 expression. The observed changes in JNK3 protein content strongly correlated with OCR measurements as determined by the Spearman's rank correlation coefficient rho in the matching islet samples, while inversely correlating with c-fos mRNA expression . In conclusion, pancreas digestion recruits JNK and p38 kinases that are known to participate to beta-cell apoptosis. Concomitantly, the islet isolation alters JNK3 and c-fos expression, both strongly correlating with OCR. Thus, a comparative analysis of JNK3 and c-fos expression before and after culture may provide for novel markers to assess islet quality prior to transplantation. JNK3 has the advantage over all other proposed markers to be islet-specific, and thus to provide for a marker independent of non-beta cell contamination.

Optimal method for short-term or long-term islet preservation: comparison of islet culture, cold preservation and cryopreservation

Islet preservation plays an important role for the success of islet transplantation. To determine the optimal method for islet preservation, we compared the outcomes of islet culture, cold preservation, and cryopreservation in this study. Isolated rat islets were divided into three groups: 37 °C group (conventional culture at 37 °C in RPMI-1640 medium), 4 °C group (cold preservation at 4 °C in University of Wisconsin (UW) solution), and -80 °C group (cryopreservation at -80 °C with dimethyl sulfoxide (DMSO)). Recovery rate, Calcein-AM/PI double staining, insulin release, mRNA level of hypoxia-inducible factor-1α (HIF-1α), and protein level of Bax in islets were examined after short-term (1 day) or long-term (7 days) preservation. After either short-term or long-term preservation, 4 °C group showed higher recovery rate of the islets number, lower percentage of PI positive area, better insulin release ability, and lower expression levels of HIF-1α and Bax in comparison to the 37 or -80 °C group. Meanwhile, islets in 37 °C group showed better function, and down-regulation of HIF-1α and Bax than those in -80 °C group on day 1; however, worse function of islets, up-regulated HIF-1α and Bax in 37 °C group were observed in comparison to -80 °C group on day 7. These results suggest that cold preservation at 4 °C in UW solution is the optimal method in comparison to the conventional culture at 37 °C or cryopreservation at -80 °C for short-term or long-term islet preservation. Furthermore, the potential mechanism may relate to, at least in part, apoptosis induced by the HIF-1α.

GLP-1-mediated gene therapy approaches for diabetes treatment

Glucagon-like peptide (GLP)-1 is an incretin hormone with several antidiabetic functions including stimulation of glucose-dependent insulin secretion, increase in insulin gene expression and beta-cell survival. Despite the initial technical difficulties and profound inefficiency of direct gene transfer into the pancreas that seriously restricted in vivo gene transfer experiments with GLP-1, recent exploitation of various routes of gene delivery and alternative means of gene transfer has permitted the detailed assessment of the therapeutic efficacy of GLP-1 in animal models of type 2 diabetes (T2DM). As a result, many clinical benefits of GLP-1 peptide/analogues observed in clinical trials involving induction of glucose tolerance, reduction of hyperglycaemia, suppression of appetite and food intake linked to weight loss have been replicated in animal models using gene therapy. Furthermore, GLP-1-centered gene therapy not only improved insulin sensitivity, but also reduced abdominal and/or hepatic fat associated with obesity-induced T2DM with drastic alterations in adipokine profiles in treated subjects. Thus, a comprehensive assessment of recent GLP-1-mediated gene therapy approaches with detailed analysis of current hurdles and resolutions, is discussed.

Rotational transport of islets: the best way for islets to get around?

Islet transplantation is a valid treatment option for patients suffering from type 1 diabetes mellitus. To assure optimal islet cell quality, specialized islet isolation facilities have been developed. Utilization of such facilities necessitates transportation of islet cells to distant institutions for transplantation. Despite its importance, a clinically feasible solution for the transport of islets has still not been established. We here compare the functionality of isolated islets from C57BL/6 mice directly after the isolation procedure as well as after two simulated transport conditions, static versus rotation. Islet cell quality was assessed using real-time live confocal microscopy. In vivo islet function after syngeneic transplantation was determined by weight and blood sugar measurements as well as by intraperitoneal glucose tolerance tests. Vascularization of islets was documented by fluorescence microscopy and immunohistochemistry. All viability parameters documented comparable cell viability in the rotary group and the group transplanted immediately after isolation. Functional parameters assessed in vivo displayed no significant difference between these two groups. Moreover, vascularization of islets was similar in both groups. In conclusion, rotary culture conditions allows the maintenance of highest islet quality for at least 15 h, which is comparable to that of freshly isolated islets.

Biologic agents in islet transplantation

Islet transplantation is today an accepted modality for treating selected patients with frequent hypoglycemic events or severe glycemic lability. Despite tremendous progress in islet isolation, culture, and preservation, clinical use is still restricted to a limited subset, and lifelong immunosuppression is required. Issues surrounding limited islet revascularization and immune destruction remain. One of the major challenges is to prevent alloreactivity and recurrence of autoimmunity against β-cells. These two hurdles can be effectively reduced by immunosuppressive therapy combining induction and maintenance treatments. The introduction of highly potent and selective biologic agents has significantly reduced the frequency of acute rejection and has prolonged graft survival, while minimizing the complications of this therapeutic scheme. This review will address the most important biological agents used in islet transplantation. We provide a historical perspective of their introduction into clinical practice and their role in current clinical protocols, aiming at improved engraftment efficiency, increased long-term survival, and better overall results of clinical islet transplantation.

Use of glucagon-like peptide-1 agonists to improve islet graft performance

Human islet transplantation is an effective and promising therapy for type I diabetes. However, long-term insulin independence is both difficult to achieve and inconsistent. De novo or early administration of incretin-based drugs is being explored for improving islet engraftment. In addition to its glucose-dependent insulinotropic effects, incretins also lower postprandial glucose excursion by inhibiting glucagon secretion, delaying gastric emptying, and can protect beta-cell function. Incretin therapy has so far proven clinically safe and tolerable with little hypoglycemic risk. The present review aims to highlight the new frontiers in research involving incretins from both in vitro and in vivo animal studies in the field of islet transplant. It also provides an overview of the current clinical status of incretin usage in islet transplantation in the management of type I diabetes.

Isolation of human cadaveric pancreatic islets for clinical transplantation

Diabetes is a debilitating condition which can lead to chronic vascular, renal, and ophthalmic disease. Type I or Juvenile Diabetes is caused by the destruction of beta cells within the islets of Langerhans within the pancreas. The beta cells are able to maintain tight control of blood glucose levels by virtue of their ability to secrete insulin in response to small increases in blood glucose concentration. In the absence of beta cells patients with Type I diabetes are dependent on the exogenous administration of insulin. This results in imperfect control of blood glucose levels. In early animal and human studies, it was shown that the transplantation of allogeneic pancreatic islets into the liver via the portal vein, coupled with low-dose immunosuppression, could lead to insulin independence and tight blood sugar control. Since these seminal studies, it has been clinically demonstrated that islets isolated from cadaveric pancreases and transplanted into the portal vein of immunosuppressed patients can maintain a state of insulin independence for upwards of 5 years. This chapter describes a method of isolating and formulating pancreatic islets from the human cadaveric pancreas.

Mesobiliverdin IXα Enhances Rat Pancreatic Islet Yield and Function

The aims of this study were to produce mesobiliverdin IXα, an analog of anti-inflammatory biliverdin IXα, and to test its ability to enhance rat pancreatic islet yield for allograft transplantation into diabetic recipients. Mesobiliverdin IXα was synthesized from phycocyanobilin derived from cyanobacteria, and its identity and purity were analyzed by chromatographic and spectroscopic methods. Mesobiliverdin IXα was a substrate for human NADPH biliverdin reductase. Excised Lewis rat pancreata infused with mesobiliverdin IXα and biliverdin IXα-HCl (1-100 μM) yielded islet equivalents as high as 86.7 and 36.5%, respectively, above those from non-treated controls, and the islets showed a high degree of viability based on dithizone staining. When transplanted into livers of streptozotocin-induced diabetic rats, islets from pancreata infused with mesobiliverdin IXα lowered non-fasting blood glucose (BG) levels in 55.6% of the recipients and in 22.2% of control recipients. In intravenous glucose tolerance tests, fasting BG levels of 56 post-operative day recipients with islets from mesobiliverdin IXα infused pancreata were lower than those for controls and showed responses that indicate recovery of insulin-dependent function. In conclusion, mesobiliverdin IXα infusion of pancreata enhanced yields of functional islets capable of reversing insulin dysfunction in diabetic recipients. Since its production is scalable, mesobiliverdin IXα has clinical potential as a protectant of pancreatic islets for allograft transplantation.

Tacrolimus inhibits the revascularization of isolated pancreatic islets

AIMS

Immunosuppressive drugs could be crucial factors for a poor outcome after islet allotransplantation. Unlike rapamycin, the effects of tacrolimus, the current standard immunosuppressant used in islet transplantation, on graft revascularization remain unclear. We examined the effects of tacrolimus on islet revascularization using a highly sensitive imaging system, and analyzed the gene expression in transplanted islets by introducing laser microdissection techniques.

METHODS

Islets isolated from C57BL/6-Tg (CAG-EGFP) mice were transplanted into the nonmetallic dorsal skinfold chamber on the recipients. Balb/c athymic mice were used as recipients and were divided into two groups: including a control group (n = 9) and tacrolimus-treated group (n = 7). The changes in the newly-formed vessels surrounding the islet grafts were imaged and semi-quantified using multi-photon laser-scanning microscopy and a Volocity system. Gene expression in transplanted islets was analyzed by the BioMark dynamic system.

RESULTS

The revascularization process was completed within 14 days after pancreatic islet transplantation at subcutaneous sites. The newly-formed vascular volume surrounding the transplanted islets in the tacrolimus-treated group was significantly less than that in the control group (p<0.05). Although the expression of Vegfa (p<0.05) and Ccnd1 (p<0.05) was significantly upregulated in the tacrolimus-treated group compared with that of the control group, no differences were observed between the groups in terms of other types of gene expression.

CONCLUSIONS

The present study demonstrates that tacrolimus inhibits the revascularization of isolated pancreatic islets without affecting the characteristics of the transplanted grafts. Further refinements of this immunosuppressive regimen, especially regarding the revascularization of islet grafts, could improve the outcome of islet allotransplantation.

Clinical utility of insulin and insulin analogs

Diabetes is a pandemic disease characterized by autoimmune, genetic and metabolic abnormalities. While insulin deficiency manifested as hyperglycemia is a common sequel of both Type-1 and Type-2 diabetes (T1DM and T2DM), it does not result from a single genetic defect--rather insulin deficiency results from the functional loss of pancreatic β cells due to multifactorial mechanisms. Since pancreatic β cells of patients with T1DM are destroyed by autoimmune reaction, these patients require daily insulin injections. Insulin resistance followed by β cell dysfunction and β cell loss is the characteristics of T2DM. Therefore, most patients with T2DM will require insulin treatment due to eventual loss of insulin secretion. Despite the evidence of early insulin treatment lowering macrovascular (coronary artery disease, peripheral arterial disease and stroke) and microvascular (diabetic nephropathy, neuropathy and retinopathy) complications of T2DM, controversy exists among physicians on how to initiate and intensify insulin therapy. The slow acting nature of regular human insulin makes its use ineffective in counteracting postprandial hyperglycemia. Instead, recombinant insulin analogs have been generated with a variable degree of specificity and action. Due to the metabolic variability among individuals, optimum blood glucose management is a formidable task to accomplish despite the presence of novel insulin analogs. In this article, we present a recent update on insulin analog structure and function with an overview of the evidence on the various insulin regimens clinically used to treat diabetes.

Combined strategy of endothelial cells coating, Sertoli cells coculture and infusion improves vascularization and rejection protection of islet graft

Improving islet graft revascularization and inhibiting rejection become crucial tasks for prolonging islet graft survival. Endothelial cells (ECs) are the basis of islet vascularization and Sertoli cells (SCs) have the talent to provide nutritional support and exert immunosuppressive effects. We construct a combined strategy of ECs coating in the presence of nutritious and immune factors supplied by SCs in a co-culture system to investigate the effect of vascularization and rejection inhibition for islet graft. In vivo, the combined strategy improved the survival and vascularization as well as inhibited lymphocytes and inflammatory cytokines. In vitro, we found the combinatorial strategy improved the function of islets and the effect of ECs-coating on islets. Combined strategy treated islets revealed higher levels of anti-apoptotic signal molecules (Bcl-2 and HSP-32), survival and function related molecules (PDX-1, Ki-67, ERK1/2 and Akt) and demonstrated increased vascular endothelial growth factor receptor 2 (KDR) and angiogenesis signal molecules (FAk and PLC-γ). SCs effectively inhibited the activation of lymphocyte stimulated by islets and ECs. Predominantly immunosuppressive cytokines could be detected in culture supernatants of the SCs coculture group. These results suggest that ECs-coating and Sertoli cells co-culture or infusion synergistically enhance islet survival and function after transplantation.

Islet transplantation in type 1 diabetes: ongoing challenges, refined procedures, and long-term outcome

Remarkable progress has been made in islet transplantation over a span of 40 years. Once just an experimental curiosity in mice, this therapy has moved forward, and can now provide robust therapy for highly selected patients with type 1 diabetes (T1D), refractory to stabilization by other means. This progress could not have occurred without extensive dynamic international collaboration. Currently, 1,085 patients have undergone islet transplantation at 40 international sites since the Edmonton Protocol was reported in 2000 (752 allografts, 333 autografts), according to the Collaborative Islet Transplant Registry. The long-term results of islet transplantation in selected centers now match registry data of pancreas-alone transplantation, with 6 sites reporting five-year insulin independence rates ≥50%. Islet transplantation has been criticized for the use of multiple donor pancreas organs, but progress has also occurred in single-donor success, with 10 sites reporting increased single-donor engraftment. The next wave of innovative clinical trial interventions will address instant blood-mediated inflammatory reaction (IBMIR), apoptosis, and inflammation, and will translate into further marked improvements in single-donor success. Effective control of auto- and alloimmunity is the key to long-term islet function, and high-resolution cellular and antibody-based assays will add considerable precision to this process. Advances in immunosuppression, with new antibody-based targeting of costimulatory blockade and other T-B cellular signaling, will have further profound impact on the safety record of immunotherapy. Clinical trials will move forward shortly to test out new human stem cell derived islets, and in parallel trials will move forward, testing pig islets for compatibility in patients. Induction of immunological tolerance to self-islet antigens and to allografts is a difficult challenge, but potentially within our grasp.

Micro/nanoscale technologies for the development of hormone-expressing islet-like cell clusters

Insulin-expressing islet-like cell clusters derived from precursor cells have significant potential in the treatment of type-I diabetes. Given that cluster size and uniformity are known to influence islet cell behavior, the ability to effectively control these parameters could find applications in the development of anti-diabetic therapies. In this work, we combined micro and nanofabrication techniques to build a biodegradable platform capable of supporting the formation of islet-like structures from pancreatic precursors. Soft lithography and electrospinning were used to create arrays of microwells (150-500 μm diameter) structurally interfaced with a porous sheet of micro/nanoscale polyblend fibers (~0.5-10 μm in cross-sectional size), upon which human pancreatic ductal epithelial cells anchored and assembled into insulin-expressing 3D clusters. The microwells effectively regulated the spatial distribution of the cells on the platform, as well as cluster size, shape and homogeneity. Average cluster cross-sectional area (~14000-17500 μm(2)) varied in proportion to the microwell dimensions, and mean circularity values remained above 0.7 for all microwell sizes. In comparison, clustering on control surfaces (fibers without microwells or tissue culture plastic) resulted in irregularly shaped/sized cell aggregates. Immunoreactivity for insulin, C-peptide and glucagon was detected on both the platform and control surfaces; however, intracellular levels of C-peptide/cell were ~60 % higher on the platform.

Insulin gene therapy from design to beta cell generation

Despite the fact that insulin injection can protect diabetic patients from developing diabetes-related complications, recent meta-analyses indicate that rapid and long-acting insulin analogues only provide a limited benefit compared with conventional insulin regarding glycemic control. As insulin deficiency is the main sequel of type-1 diabetes (T1D), transfer of the insulin gene-by-gene therapy is becoming an attractive treatment modality even though T1D is not caused by a single genetic defect. In contrast to human insulin and insulin analogues, insulin gene therapy targets to supplement patients not only with insulin but also with C-peptide. So far, insulin gene therapy has had limited success because of delayed and/or transient gene expression. Sustained insulin gene expression is now feasible using current gene-therapy vectors providing patients with basal insulin coverage, but management of postprandial hyperglycaemia is still difficult to accomplish because of the inability to properly control insulin secretion. Enteroendocrine cells of the gastrointestinal track (K cells and L cells) may be ideal targets for insulin gene therapy, but cell-targeting difficulties have limited practical implementation of insulin gene therapy for diabetes treatment. Therefore, recent gene transfer technologies developed to generate authentic beta cells through transdifferentiation are also highlighted in this review.

Significant improvement in islet yield and survival with modified ET-Kyoto solution: ET-Kyoto/Neutrophil elastase inhibitor

Although islet transplantation can achieve insulin independence in patients with type 1 diabetes, sufficient number of islets derived from two or more donors is usually required to achieve normoglycemia. Activated neutrophils and neutrophil elastase (NE), which is released from these neutrophils, can directly cause injury in islet grafts. We hypothesized that inhibition of NE improves islet isolation and islet allograft survival. We tested our hypothesis by examining the effects of modified ET-Kyoto solution supplemented with sivelestat, a NE inhibitor (S-Kyoto solution), on islet yield and viability in islet isolation and the effect of intraperitoneally injected sivelestat on islet graft survival in a mouse allotransplant model. NE and proinflammatory cytokines such as tumor necrosis factor (TNF)-α and interleukin (IL)-6 increased markedly at the end of warm digestion during islet isolation and exhibited direct cytotoxic activity against the islets causing their apoptosis. The use of S-Kyoto solution significantly improved islet yield and viability. Furthermore, treatment with sivelestat resulted in significant prolongation of islet allograft survival in recipient mice. Furthermore, serum levels of IL-6 and TNF-α at 1 and 2 weeks posttransplantation were significantly higher in islet recipients than before transplantation. Our results indicated that NE released from activated neutrophils negatively affects islet survival and that its suppression both in vitro and in vivo improved islet yield and prolonged islet graft survival. The results suggest that inhibition of NE activity could be potentially useful in islet transplantation for patients with type 1 diabetes mellitus.

Effects of astragalosides on cultured islets after cryopreservation in rats

OBJECTIVE

To explore the effects of AST (astragalosides) on cultured rat islet yield, purity, and function after cryopreservation in rats.

METHODS

Pancreatic islets were isolated from 30 Sprague-Dawley rats using the standard technique of collagenase P digestion and discontinuous Ficoll gradient purification. After thaw, the islets were randomly divided into AST group and control group (n=15). Next, the islet cells were cultured in AST-containing medium or standard medium for 7, 14, and 21 days after cryopreservation and thaw. The quantity, purity, and survival rate were calculated in the two groups before and after culture. Then the in vitro and in vivo function was observed in diabetic rats after islet transplantation.

RESULTS

The quantity and purity of islets had no difference between the two groups before culture (P>.05) while the difference after culture was significantly (P<.05). The survival rate of islets was 48% in AST group and 32% in the control group 21 days after thaw (P<.05). After 3 days, there was significantly a higher simulation index in the AST group than in the control group (P<.05). There was a significant difference in blood glucose and insulin concentrations between the groups after 3 days (P<.05).

CONCLUSION

AST can be added to the culture medium to reduce the loss of islet cryopreservation and be intravenously injected to improve culture islet function in vitro and prolong islet graft survival in diabetic rats.

Pancreatic islet cell transplantation: an update for interventional radiologists

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

Encapsulated islets transplantation: Past, present and future

Islet transplantation could become an ideal treatment for severe diabetes to prevent hypoglycemia shock and irreversible diabetic complications, once some of the major and unresolved obstacles are overcome, including limited donor supplies and side effects caused by permanent immunosuppressant use. Approximately 30 years ago, some groups succeeded in improving the blood glucose of diabetic animals by transplanting encapsulated islets with semi-permeable membranes consisting of polymer. A semi-permeable membrane protects both the inner islets from mechanical stress and the recipient's immune system (both cellular and humoral immunities), while allowing bidirectional diffusion of nutrients, oxygen, glucose, hormones and wastes, i.e., immune-isolation. This device, which enables immune-isolation, is called encapsulated islets or bio-artificial pancreas. Encapsulation with a semi-permeable membrane can provide some advantages: (1) this device protects transplanted cells from the recipient's immunity even if the xenogeneic islets (from large animals such as pig) or insulin-producing cells are derived from cells that have the potential for differentiation (some kinds of stem cells). In other words, the encapsulation technique can resolve the problem of limited donor supplies; and (2) encapsulation can reduce or prevent chronic administration of immunosuppressants and, therefore, important side effects otherwise induced by immunosuppressants. And now, many novel encapsulated islet systems have been developed and are being prepared for testing in a clinical setting.

Late cytomegalovirus transmission and impact of T-depletion in clinical islet transplantation

The epidemiology of cytomegalovirus infection (CMV) in islet transplantation (IT) is not well defined. This study defines incidence, transmission and clinical sequelae of CMV reactivation or disease in 121 patients receiving 266 islet infusions at a single institution. The donor (D)/recipient (R) serostatus was D+/R- 31.2%, D+/R+ 26.3%, D-/R+ 13.2% and D-/R- 29.3%. CMV prophylaxis with oral ganciclovir/valganciclovir was given in 68%. CMV infection occurred in 14/121 patients (11.6%); six had asymptomatic seroconversion and eight others had positive viremia (six asymptomatic and two with CMV febrile symptoms). Median peak viral loads were 1755 copies/mL (range 625-9 100 000). Risk factors for viremia included lymphocyte depletion (thymoglobulin or alemtuzumab, p < 0.001). Viremia was more common in D+/R+ versus D+/R- (p = 0.12), occurring mostly late after transplant (median 306 days). Presumed transmission from IT occurred in 8/83 of D+/R- procedures (9.6%). Of the two cases of CMV disease, one resulted from islet transmission from a CMV positive donor (D+/R-); the other was due to de novo exogenous infection (D-/R-). Therefore, CMV transmission presents rarely after IT and with low incidence compared to solid organ transplantation, but occurs late posttransplant. The use of lymphocyte depleting therapies is a primary risk factor.

Improvement of pancreatic islet cell isolation for transplantation

Pancreatic islet transplantation is a promising treatment for diabetes but still faces several challenges. Poor islet isolation efficiency and poor long-term insulin independence are currently two major issues, although donor shortage and the need for immunosuppressants also need to be addressed. We established the Kyoto islet isolation method (KIIM), which has enabled us to isolate and transplant islets even from non-heart-beating donors. KIIM involves 1) cooling the donor pancreas in situ, 2) preserving the ducts with modified Kyoto solution, 3) using a modified two-layer pancreas preservation method, and 4) adjusting the density of the density gradient centrifugation and using an iodixanol-based solution for purification. KIIM has enabled us to transplant 17 islet preparations out of 21 isolations (an 81% success rate). All transplanted islets functioned, and all transplanted patients had improved glycemic control without hypoglycemic unawareness. Recently, we used KIIM for islet isolation from a brain-dead donor at Baylor, which resulted in a very high islet yield (789,984 IE) with high viability (100% by fluorescein diacetate/propidium iodide staining and a stimulation index of 4.7). This preliminary evidence suggests that KIIM may also be promising for islet isolation from brain-dead donors. In addition, to assess engrafted islet mass, we developed a secretory unit of islet transplant objects (SUITO) index: fasting C-peptide (ng/dL) / [fasting blood glucose (mg/dL) - 63] x 1500. This simple index has enabled us to monitor the engrafted islet mass. This index should be useful when deciding whether to perform additional islet transplantations to maintain insulin independence. Poor islet isolation efficacy and poor long-term results could be resolved with ongoing research.

Mesenchymal Stromal Cells as a Therapeutic Strategy to Support Islet Transplantation in Type 1 Diabetes Mellitus

Type 1 diabetes is an autoimmune disorder that leads to destruction of pancreatic β islet cells and is a growing global health issue. While insulin replacement remains the standard therapy for type 1 diabetes, exogenous insulin does not mimic the physiology of insulin secretion. Transplantation of pancreatic islets has the potential to cure this disease; however, there are several major limitations to widespread implementation of islet transplants. The use of mesenchymal stromal cells (MSCs) in the treatment of type 1 diabetes has been investigated as an adjunct therapy during islet graft administration to prevent initial islet loss and promote engraftment and revascularization of islets. In this review we will discuss the results of recent MSC studies in animal models of diabetes with a focus on islet transplantation and explore the potential for these findings to be extended to clinical use for the treatment of type 1 diabetes.

Tracing of islet graft survival by way of in vivo fluorescence imaging

BACKGROUND

To increase the success rate in xenogeneic islet transplantation, proper assessment of graft mass is required following transplantation. For this reason, we aimed to develop a suitable fluorescence imaging system to monitor islet xenograft survival in diabetic mice.

METHODS

Adenovirus vector encoding enhanced green fluorescent protein-transduced rat pancreatic islets were transplanted under the renal capsule of streptozotocin-induced diabetic mice and the fluorescence signal was quantified over time using a cooled charge-coupled device. Non-fasting blood glucose levels were recorded during the same period. Insulin release from transduced and control islets was detected via enzyme-linked immunosorbent assay.

RESULTS

Adenovirus vector encoding enhanced green fluorescent protein infection did not alter the function or survival of pancreatic islets post transduction. A direct correlation was found between the number of islets (250-750) transplanted under the kidney capsule and the blood glucose recovery.

CONCLUSIONS

Fluorescence imaging appears to be a useful tool for quantitative assessment of islet cell viability post transplantation and could permit earlier detection of graft rejection.

Similar islet function in islet allotransplant and autotransplant recipients, despite lower islet mass in autotransplants

BACKGROUND

Despite high initial rates of insulin independence after islet allotransplant for type 1 diabetes, long-term islet function is suboptimal. Possible contributing factors include autoimmune recurrence, alloimmune rejection, or immunosuppressant medication toxicity. In contrast, islet autografts, infused at the time of pancreatectomy for chronic pancreatitis, are not subject to these variables. Islet function was compared in autograft and allograft recipients.

METHODS

Eight autograft and eight allograft recipients, insulin independent or requiring minimal insulin, were matched for similar duration posttransplant (mean 2.1±1.2 years). Eleven healthy control subjects were also enrolled. Subjects underwent oral and intravenous glucose tolerance testing and arginine stimulation testing.

RESULTS

Age, gender, body mass index, duration posttransplant, and hemoglobin A1c levels were similar between groups. Glucose tolerance was worse in transplant recipients compared with controls. Alloislet recipients received significantly more islet equivalents per kg body weight (IE/kg) than autograft recipients (9958±6229 IE/kg vs. 4589±1232 IE/kg, P=0.03). However, the glycemic response to oral glucose tolerance testing, the acute insulin response to glucose, and the acute insulin response to arginine did not differ significantly between islet allograft and autograft recipients.

CONCLUSIONS

Insulin secretion and glucose excursion were similar in allograft and autograft recipients, despite the latter group receiving less than half as many islets. Better preservation of islet mass in the autograft setting is likely related to the lack of autoimmunity, alloimmunity, and immunosuppressive drug toxicity, highlighting the potential for better outcomes in islet allotransplant for type 1 diabetes mellitus with refinements in immunosuppression.

Selective depletion of cross-presenting dendritic cells enhances islet allograft survival

MHC class I presentation of peptides derived from exogenous antigens (not synthesized within the antigen-presenting cell) is called cross-presentation and is mediated by selective subsets of dendritic cells (DC). A proportion of both donor and host DC may cross-present. Although there has been many studies that have investigated the role of donor versus host DC (i.e., direct vs. indirect pathway), what role cross-presenting DC play in allograft rejection has not been determined. We recently identified an agent, cytochrome c (cytc), that selectively depletes cross-presenting DC in vivo. By administering cytc we were able to study the impact of cross-presenting DC on rejection of islets grafted into fully mismatched mice. We found that cytc protected about half of the islet allografts from rejection. Our results indicate that cross-presenting DC can make potent contributions to the immune response to islet allografts, and contend that agents such as cytc that selectively target DC heralds a novel method of immunosuppression.

Binding of the fibronectin-mimetic peptide, PR_b, to alpha5beta1 on pig islet cells increases fibronectin production and facilitates internalization of PR_b functionalized liposomes

Islet transplantation is a promising treatment for type 1 diabetes. Recent studies have demonstrated that human islet allografts can restore insulin independence to patients with this disease. As islet isolation and immunotherapeutic techniques improve, the demand for this cell-based therapy will dictate the need for other sources of islets. Pig islets could provide an unlimited supply for xenotransplantation and have shown promise as an alternative to human islet allografts. However, stresses imposed during islet isolation and transplantation decrease islet viability, leading to loss of graft function. In this study, we investigated the ability of a fibronectin-mimetic peptide, PR_b, which specifically binds to the alpha(5)beta(1) integrin, to re-establish lost extracellular matrix (ECM) around isolated pig islets and increase internalization of liposomes. Confocal microscopy and Western blotting were used to show the presence of the integrin alpha(5)beta(1) on the pig islets on day 0 (day of isolation) as well as on different days of islet culture. Islets cultured in medium supplemented with free PR_b for 48 h were found to have increased levels of ECM fibronectin secretion compared to islets in normal culture conditions. Using confocal microscopy and flow cytometry, we found that PR_b peptide-amphiphile functionalized liposomes delivered to the pig islets internalized into the cells in a PR_b concentration dependent manner and nonfunctionalized liposomes showed minimal internalization. These studies proved that the fibronectin-mimetic peptide, PR_b, is an appropriate peptide bullet for applications involving alpha(5)beta(1) expressing pig islet cells. Fibronectin production stimulated through alpha(5)beta(1) PR_b binding may decrease apoptosis and therefore increase islet viability in culture. In addition, PR_b peptide-amphiphile functionalized liposomes may be used for targeted delivery of different agents to pig islet cells.

Diabetes prevention by immunomodulatory FTY720 treatment in the LEW.1AR1-iddm rat despite immune cell activation

The prevention of diabetes by the immunomodulatory agent FTY720 (fingolimod) was studied in the LEW.1AR1-iddm (IDDM) rat, an animal model of human type 1 diabetes. Immune cell subtypes and cytokine profiles in pancreatic islets, secondary lymphoid tissue, and serum were analyzed for signs of immune cell activation. Animals were treated with FTY720 (1 mg/kg body weight) for 40 d starting on d 50 of life. Changes in gene and protein expression of cytokines, CD8 markers, monocyte chemoattractant protein-1, inducible NO synthase, and caspase 3 were evaluated. Treatment with FTY720 prevented diabetes manifestation and islet infiltration around d 60 of life, the usual time of spontaneous diabetes development. On d 120, 30 d after the end of FTY720 therapy, diabetes prevention persisted. However, six of 12 treated animals showed increased gene expression of IL-1beta, TNF-alpha, and CD8 markers in pancreas-draining lymph nodes, indicating immune cell activation. In parallel, serum concentrations of these proinflammatory cytokines were increased. These six animals also showed macrophage infiltration without proinflammatory cytokine expression in a small minority (2-3%) of islets. Interestingly, regulatory T lymphocytes were significantly increased in the efferent vessels of the pancreas-draining lymph nodes only in animals without signs of immune cell activation but not in the rats with immune cell activation. This provides an indication for a lack of protective capacity in the animals with activated immune cells. Thus, FTY720 treatment prevented the manifestation of diabetes by promoting the retention of activated immune cells in the lymph nodes, thereby avoiding islet infiltration and beta-cell destruction by proinflammatory cytokines.

BH3 mimetics antagonizing restricted prosurvival Bcl-2 proteins represent another class of selective immune modulatory drugs

Death by apoptosis shapes tissue homeostasis. Apoptotic mechanisms are so universal that harnessing them for tailored immune intervention would seem challenging; however, the range and different expression levels of pro- and anti-apoptotic molecules among tissues offer hope that targeting only a subset of such molecules may be therapeutically useful. We examined the effects of the drug ABT-737, a mimetic of the killer BH3 domain of the Bcl-2 family of proteins that induces apoptosis by antagonizing Bcl-2, Bcl-X(L), and Bcl-W (but not Mcl-1 and A1), on the mouse immune system. Treatment with ABT-737 reduced the numbers of selected lymphocyte and dendritic cell subpopulations, most markedly in lymph nodes. It inhibited the persistence of memory B cells, the establishment of newly arising bone marrow plasma cells, and the induction of a cytotoxic T cell response. Preexisting plasma cells and germinal centers were unaffected. Notably, ABT-737 was sufficiently immunomodulatory to allow long-term survival of pancreatic allografts, reversing established diabetes in this model. These results provide an insight into the selective mechanisms of immune cell survival and how this selectivity avails a different strategy for immune modulation.

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.

Inhibition of Hes1 activity in gall bladder epithelial cells promotes insulin expression and glucose responsiveness

The biliary system has a close developmental relationship with the pancreas, evidenced by the natural occurrence of small numbers of biliary-derived beta-cells in the biliary system and by the replacement of biliary epithelium with pancreatic tissue in mice lacking the transcription factor Hes1. In normal pancreatic development, Hes1 is known to repress endocrine cell formation. Here we show that glucose-responsive insulin secretion can be induced in biliary epithelial cells when activity of the transcription factor Hes1 is antagonised. We describe a new culture system for adult murine gall bladder epithelial cells (GBECs), free from fibroblast contamination. We show that Hes1 is expressed both in adult murine gall bladder and in cultured GBECs. We have created a new dominant negative Hes1 (DeltaHes1) by removal of the DNA-binding domain, and show that it antagonises Hes1 function in vivo. When DeltaHes1 is introduced into the GBEC it causes expression of insulin RNA and protein. Furthermore, it confers upon the cells the ability to secrete insulin following exposure to increased external glucose. GBEC cultures are induced to express a wider range of mature beta cell markers when co-transduced with DeltaHes1 and the pancreatic transcription factor Pdx1. Introduction of DeltaHes1 and Pdx1 can therefore initiate a partial respecification of phenotype from biliary epithelial cell towards the pancreatic beta cell.

Islet cell transplantation for Type 1 diabetes

Islet transplantation is an attractive concept for the treatment of Type 1 diabetes because of its potential high efficacy and minimal invasion to patients. The treatment may effectively control blood glucose for brittle Type 1 diabetes, resulting in a marked reduction in hypoglycemic episodes and improvements in HbA1c. In addition, approximately 70% of transplanted Type 1 diabetic patients have achieved insulin independence. However, there are still important issues to be addressed before this treatment is widely applicable, including difficulty in maintaining insulin independence, low islet isolation success rate, multiple donor requirements, and side effects associated with the use of immunosuppressants. Donor shortage is another dilemma. To address the issue of donor shortage, living donor islet transplantation and bioartificial islet transplantation using pig islets are being evaluated. Bioartificial islet transplantation could be the ultimate solution of the donor shortage. Currently, overcoming immunological hurdles, establishing reliable islet isolation methods, and controlling porcine endogenous retrovirus are the primary obstacles to the implementation of this treatment. If bioartificial islet transplant becomes a clinical reality, it may even be applicable in the treatment of select Type 2 diabetic patients. β-Cell regeneration from naïve pancreas and β-cell generation from embryonic stem cells or induced pluripotent stem cells are the next-generation treatments for Type 1 diabetes.

SUITO index for evaluation of efficacy of single donor islet transplantation

Evaluation of engrafted islets mass is important for clinical care of patients after islet transplantation. Recently, we developed the secretory unit of islet transplant objects (SUITO) index, which reflected engrafted islet mass. In this study, we evaluated the SUITO index for the prediction of clinical outcome after single islet transplantation. Single islet transplantations were performed into six type 1 diabetic patients. Isolated islets were quantitatively assessed at the time of transplantation. The SUITO index was calculated as follows: fasting C-peptide (ng/dl)/[fasting blood glucose (mg/dl) - 63] x 1500. Islet yield/recipient's body weight and SUITO index were evaluated, along with HbA(1C), relative insulin dose (insulin dose posttransplant/pretransplant), and M-values. HbA(1C) improved in all cases, irrespective of the SUITO index score or islet yield/body weight. The average SUITO index from postoperative days 3 to 30 (R(2) = 0.728, p < 0.04), but not islet yield/body weight (R(2) = 0.259, p = 0.303), correlated with relative insulin dose. The daily SUITO index strongly correlated with the daily relative insulin dose (R(2) = 0.558, p < 0.0001) and weakly correlated with the daily M-values (R(2) = 0.207, p < 0.02). A SUITO index score of less than 10 was associated with increasing insulin dose even after islet transplantation. The SUITO index seems to be a better predictor of success of islet transplantations than islet yield/body weight. SUITO index is recommended to assess clinical outcome of islet transplantation.

Anti-inflammatory peptide-functionalized hydrogels for insulin-secreting cell encapsulation

Pancreatic islet encapsulation within semi-permeable materials has been proposed for transplantation therapy of type I diabetes mellitus. Polymer hydrogel networks used for this purpose have been shown to provide protection from islet destruction by immunoreactive cells and antibodies. However, one of the fundamental deficiencies with current encapsulation methods is that the permselective barriers cannot protect islets from cytotoxic molecules of low molecular weight that are diffusible into the capsule material, which subsequently results in beta-cell destruction. Use of materials that can locally inhibit the interaction between the permeable small cytotoxic factors and islet cells may prolong the viability and function of encapsulated islet grafts. Here we report the design of anti-inflammatory hydrogels supporting islet cell survival in the presence of diffusible pro-inflammatory cytokines. We demonstrated that a poly(ethylene glycol)-containing hydrogel network, formed by native chemical ligation and presenting an inhibitory peptide for islet cell surface IL-1 receptor, was able to maintain the viability of encapsulated islet cells in the presence of a combination of cytokines including IL-1 beta, TNF-alpha, and INF-gamma. In stark contrast, cells encapsulated in unmodified hydrogels were mostly destroyed by cytokines which diffused into the capsules. At the same time, these peptide-modified hydrogels were able to efficiently protect encapsulated cells against beta-cell specific T-lymphocytes and maintain glucose-stimulated insulin release by islet cells. With further development, the approach of encapsulating cells and tissues within hydrogels presenting anti-inflammatory agents may represent a new strategy to improve cell and tissue graft function in transplantation and tissue engineering applications.