THERAPY OF ENDOCRINE DISEASE: Islet transplantation for type 1 diabetes: so close and yet so far away

in European Journal of Endocrinology
View More View Less
  • 1 Department of Stem Cells and Developmental Biology at Cell Science Research Center, Department of Regenerative Medicine at Cell Science Research Center, Endocrinology and Metabolism Research Institute, Diabetes Research Center, Division of Nephrology and Hypertension, Department of Developmental Biology, Royan Institute for Stem Cell Biology and Technology, ACECR, Tehran, Iran

Correspondence should be addressed to H Baharvand; Email: Baharvand@royaninstitute.org
Free access

Over the past decades, tremendous efforts have been made to establish pancreatic islet transplantation as a standard therapy for type 1 diabetes. Recent advances in islet transplantation have resulted in steady improvements in the 5-year insulin independence rates for diabetic patients. Here we review the key challenges encountered in the islet transplantation field which include islet source limitation, sub-optimal engraftment of islets, lack of oxygen and blood supply for transplanted islets, and immune rejection of islets. Additionally, we discuss possible solutions for these challenges.

Abstract

Over the past decades, tremendous efforts have been made to establish pancreatic islet transplantation as a standard therapy for type 1 diabetes. Recent advances in islet transplantation have resulted in steady improvements in the 5-year insulin independence rates for diabetic patients. Here we review the key challenges encountered in the islet transplantation field which include islet source limitation, sub-optimal engraftment of islets, lack of oxygen and blood supply for transplanted islets, and immune rejection of islets. Additionally, we discuss possible solutions for these challenges.

Introduction

Type 1 diabetes (T1D) is an autoimmune disease where the immune system destroys insulin-producing pancreatic β cells, leading to increased serum blood glucose levels. Despite tremendous efforts to tightly regulate blood glucose levels in diabetic patients by different methods of insulin therapy, pathologic processes that result in long-term complications exist (1). Another approach, transplantation of the pancreas as a pancreas-after-kidney or simultaneous pancreas–kidney transplant is used for the majority of T1D patients with end stage renal failure. Surgical complications and lifelong immunosuppression are among the major pitfalls of this treatment (2). Pancreatic islet transplantation has been introduced as an alternative approach to transplantation of the pancreas. This procedure does not require major surgery and few complications arise. However, lifelong immunosuppression is still needed to preserve the transplanted islets. Although during the past two decades significant progress in islet transplantation conditions and outcomes has been achieved, challenges remain that hinder the use of this therapy as a widely available treatment for T1D. After reviewing the history of islet transplantation, we classify the major challenges of islet transplantation into four distinct categories relative to the transplantation time point: islet source limitation, sub-optimal engraftment of islets, lack of oxygen and blood supply, and immune rejection (Fig. 1). We also discuss possible solutions to these challenges.

Figure 1
Figure 1

Major challenges and possible solutions for islet transplantation. In a time-dependent manner, major challenges of islet transplantation are divided into four categories. The possible solutions to overcome each challenge are mentioned below each category. Tx, transplantation; iPSCs, induced pluripotent stem cells; TSSCs, tissue specific stem cells; ECM, extracellular matrix. A full colour version of this figure is available at http://dx.doi.org/10.1530/EJE-15-0094.

Citation: European Journal of Endocrinology 173, 5; 10.1530/EJE-15-0094

History of islet transplantation and clinical results

The first clinical allogenic islet transplantation performed by Najarian et al. (3) at the University of Minnesota in 1977 resulted in an unsatisfactory outcome. In 1988, while Dr Camilio Ricordi was a postdoctoral researcher in Dr Lacy's laboratory, they introduced an automated method for isolation of human pancreatic islets (4). This research led to the first partially successful clinical islet transplantation at Washington University in 1989. By 1999, ∼270 patients received transplanted islets with an estimated 1 year insulin independence rate of 10%. In 2000, a successful trial was published by Shapiro et al. (5). In their study, all seven patients who underwent islet transplantation at the University of Alberta achieved insulin independence. Of these, five maintained insulin independence 1 year after transplantation. This strategy, known as the Edmonton protocol, had three major differences compared to the previous transplant procedures. These differences included a shorter time between preparation of islets and transplantation, use of islets from two or three donors (∼11 000 islet equivalents per kilogram of recipient body weight), and a steroid-free immune suppressant regimen (5). In their next year's report, it was shown that the risk-to-benefit ratio favored islet transplantation for patients with labile T1D (6). In a 5-year follow-up of 47 patients by the Edmonton group, ∼10% remained insulin-free and about 80% still had positive C-peptide levels. Other advantages of islet transplantation included well-controlled HbA1c levels, reduced episodes of hypoglycemia, and diminished fluctuations in blood glucose levels (7).

Two studies by Hering et al. at the University of Minnesota reported promising outcomes in achieving insulin independence from a single donor. In 2004, they reported achievement of insulin independence in four out of six islet transplant recipients (8). In their next report, all eight patients who underwent islet transplantation achieved insulin independence after a single transplant; five remained insulin-free 1 year later (9). Dr Warnock's group at the University of British Columbia showed better metabolic indices and slower progression of diabetes complications after islet transplantation compared to the best medical therapy program (10, 11, 12, 13).

The last decade has shown consistent improvement in the clinical outcomes of islet transplantation. A 2012 report from the Collaborative Islet Transplant Registry (CITR) evaluated 677 islet transplant-alone and islet after-kidney recipient outcomes for the early (1999–2002), mid (2003–2006) and recent (2007–2010) transplant era. The 3-year insulin independence rate increased considerably from 27% in the early transplant era to 37% during the mid and 44% in the most recent era (14). Another analysis at CITR and the University of Minnesota reported that the 5-year insulin independence after islet transplantation for selected groups (50%) approached the clinical results of pancreas transplantation (52%) according to the Scientific Registry of Transplant Recipients (15).

Islet source limitation

The first category of islet transplantation challenges refers to donor pancreatic islet limitations as a major concern prior to transplantation. The lack of donor pancreatic islets hinders widespread application of islet transplantation as a routine therapy for T1D patients.

Pre-existing islet sources

Currently, pancreata from brain dead donors (BDDs) are the primary source of islets for transplantation. Since whole pancreas transplantation takes precedence over islet transplantation due to the long-term results, the harvested pancreata are frequently not used for islet isolation. However, the long-term insulin independence rate after islet transplantation is approaching the outcome of whole pancreas transplantation (15). The rules for allocating harvested pancreas organs may change in the future and provide an increased source of pancreata for islet transplantation.

Non-heart-beating donors (NHBDs) may emerge as potential sources for islet isolation. Due to the potential ischemic damage to exocrine cells which may induce pancreatitis, NHBDs' pancreata are not preferred for whole pancreas transplantation. A study by Markmann et al. (16) has reported that the quality of ten NHBDs' pancreatic islets was proven to be similar to islets obtained from ten BDDs.

Xenogenic islets are another promising source of pre-existing islets for transplantation. Pig islets are the only source of xenogeneic islets that have been used for transplantation into humans, not only because of availability but also due to similarities in islet structure and physiology to human islets (17). Nonetheless the same challenges for allotransplantation, yet more severe, include limited engraftment and immune rejection following xenotransplantation of pig islets. Different strategies such as genetic engineering of pigs are underway to produce an ideal source of donor pigs for islet transplantation (18).

Human embryonic stem cell-derived β cells

In the future, generation of new β cells from human embryonic stem cells (hESCs) may provide an unlimited source of these cells for transplantation into T1D patients (Fig. 2). Research has made use of known developmental cues to mimic the stages of β cell development (19) and demonstrated that hESCs are capable of stepwise differentiation into definitive endoderm (DE), pancreatic progenitor (PP), endocrine progenitor, and insulin producing β-like cells (BLCs) (reviewed in (20)). The forced expression of some pancreatic transcription factors (TFs) such as Pdx (21), Mafa, Neurod1, Neurog3 (22) and Pax4 (23) in ESCs is an effective approach in this regard. Although this approach has yet to generate an efficient differentiation protocol, it provided the proof of principle for the concept of ‘cell-fate engineering’ towards a β cell-like state (24). The introduction of a chemical biology approach to the field of differentiation (reviewed in (25)) was a step forward in the reproduction of more efficient, universal, xeno-free, well-defined and less expensive differentiation methods. A number of these molecules such as CHIR (activator of Wnt signaling, DE stage) or SANT1 (inhibitor of Sonic hedgehog signaling, PP stage) have been routinely used in the most recent and efficient protocols (26). Attempts at producing efficient hESC-derived functional BLCs (hESC-BLCs) in vitro recently led both to static (27) and scalable (26) generation of hESC-BLCs with increased similarity to primary human β cells. These transplanted cells more rapidly ameliorated diabetes in diabetic mouse models compared to previous reports.

Figure 2
Figure 2

β cell sources for replacing damaged islets in type 1 diabetic (T1D) patients. Pre-existing islets can be harvested from brain dead donors (BDDs) or non-heart beating donors (NHBD) for allotransplantation and from other species for xenotransplantation. Expandable cell sources such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) can be differentiated into insulin producing cells (IPCs) in a stepwise manner through mimicking developmental steps that include the definitive endoderm (DE), pancreatic progenitor (PP) and endocrine progenitor (EP) stages. Patient-specific β cell sources can be derived from the following steps: (i) trans-differentiation of adult cells toward IPCs, (ii) reprogramming to iPSCs and (iii) differentiating toward IPCs. Differentiation of tissue specific stem cells (TSSCs) is another strategy to generate patient specific β cell sources. In vivo conversion of other cells to β cells through delivery of pancreatic transcription factors (TFs) is the last strategy described in this figure. A full colour version of this figure is available at http://dx.doi.org/10.1530/EJE-15-0094.

Citation: European Journal of Endocrinology 173, 5; 10.1530/EJE-15-0094

While studies on production of hESC-BLCs have continued, the immunogenicity challenge remains an important issue in the clinical application of these allogeneic cells. To overcome this problem, some groups have introduced macroencapsulation devices as immune-isolation tools for transplantation of hESC-BLCs into mouse models (28). In another strategy, Rong et al. produced knock-in hESCs that constitutively expressed immunosuppressive molecules such as cytotoxic T lymphocyte antigen 4-immunoglobulin fusion protein (CTLA4-Ig) and programmed death ligand-1. They reported immune-protection of these allogeneic cells in humanized mice (29).

Recently, Szot et al. showed that co-stimulation blockade could induce tolerance to transplanted xenogeneic hESC-derived pancreatic endoderm in a mouse model. This therapy led to production of islet-like structures and control of blood glucose levels. Co-stimulation blockade could prevent rejection of these cells by allogeneic human peripheral blood mononuclear cells in a humanized mouse model (30).

Patient-specific cell sources

Although the differentiation potential and expandability of hESCs make them a worthy cell source for islet replacement, immunological limitations exist as with other allotransplantations. Additionally, the use of human embryos to generate hESCs remains ethically controversial (31). Several approaches have been proposed to circumvent this hurdle as discussed in the following sections.

Induced pluripotent reprogramming

Human induced pluripotent stem cells (hiPSCs) are virtually considered the ‘autologous’ equivalent of hESCs. Several groups have differentiated hiPSCs along with hESCs into insulin producing cells through identical protocols and reported comparable differentiation efficiencies (26, 32).

Theoretically, iPSCs should be tolerated by the host without an immune rejection. However, even syngeneic iPSC-derived cells were immunogenic in syngeneic hosts (33), which possibly resulted from their genetic manipulation. Epigenetic studies of produced iPSCs traced epigenetic memory or reminiscent marks, such as residual DNA methylation signatures of the starting cell types during early passages of iPSCs (34, 35) which could explain the mechanisms behind such observations. Alternative strategies such as non-integrative vectors (36), adenoviruses (37), repeated mRNA transfection (38, 39, 40), protein transduction (41), and transposon-based transgene removal (42) have been successfully applied to develop transgene-free iPSC lines. This progression towards safe iPSC generation (reviewed in (43)) offers a promising technology for medical pertinence. The cost and time needed to generate ‘custom-made’ hiPSCs is another important consideration. Establishment of ‘off-the-shelf’ hiPSCs that contain the prevalent homozygous HLA combinations has been proposed as a solution (44). Such HLA-based hiPSC banks are assumed to provide a cost-effective cell source for HLA-compatible allotransplantations which may reduce the risk of immune rejection.

Differentiation of tissue-specific stem cells

The presence of populations of tissue-specific stem cells (TSSCs) in different organs of the human body provides another putative patient-specific cell source. As a long-known class of TSSCs, bone marrow (BM) stem cells are currently used in medical procedures and can be harvested through existing clinical protocols for a variety of uses (45). Although a preliminary report has suggested that BM stem cells can differentiate into β-cells in vivo (46), further experiments have demonstrated that transplantation of BM-derived stem cells reduces hyperglycemia through an immune-modulatory effect and causes the induction of innate mechanisms of islet regeneration (47, 48). Other in vitro murine studies have shown that BM mesenchymal stem cells (MSCs) can be directly differentiated into insulin producing cells capable of reversing hyperglycemia after transplantation in diabetic animals (49, 50). In vitro generation of insulin producing cells from human BM and umbilical cord MSCs have also been reported (51, 52). However, the functionality and glucose responsiveness of these cells are unclear.

Transdifferentiation (induced lineage reprogramming)

Transdifferentiation can be defined as direct fate switching from one somatic mature cell type to another functional mature or progenitor cell type without proceeding through a pluripotent intermediate (53). Studies of mouse gall bladder (54), human keratinocytes (55), α-TC1.6 cells (56), pancreatic islet α-cells (57), liver cells (58, 59) and skin fibroblasts (60, 61) demonstrate that non-β somatic cells may have potential as an alternative source for cell therapy in diabetes. Viral gene delivery of a triad of TFs (Pdx1, Neurog3 and Mafa) is another effective strategy for in situ transdifferentiation of both pancreatic exocrine cells (62) and liver cells (63) into functional insulin secreting cells.

The clinical application of this approach faces a number of challenges such as efficiency, stability and functionality of the target cells, identification of proper induction factor(s), epigenetic memory, safety concerns, and immune rejection issues associated with genetic manipulation (reviewed in (53)).

β cell regeneration

Restoration of the endogenous β cell mass through regeneration is an attractive alternative approach. Replication of residual β cells (64, 65, 66), re-differentiation of dedifferentiated β cells (67), neogenesis from endogenous progenitors (68, 69) and trans-differentiation from (mature) non-β cells (62, 70) are proposed mechanisms for β cell regeneration.

β cell replication is the principal mechanism by which these cells are formed in the adult pancreas under normal physiological conditions (64, 66). Approaches that promote β cell replication and/or redirect dedifferentiated β cells toward insulin production can present an interesting strategy to restore the endogenous β cell mass.

In addition to β cells, evidence exists for the contribution of other pancreatic cell types such as acinar cells, α cells and pancreatic Neurog3 expressing cells (68) to the formation of new β cells in different mouse models. The signals that drive the endogenous regenerative mechanisms are only marginally understood. A role for paracrine signaling from the vasculature to β cell regeneration has been hypothesized. This hypothesis is supported by clear correlation between blood vessels and β cell mass adaptation during periods of increased demand and the impact of endothelial cell-derived hepatocyte growth factor (HGF) on the β cell phenotype. In addition to the putative role of paracrine signals from the vasculature, the possibility of an endocrine trigger for β cell proliferation and regeneration has been proposed. In this regard a fat and liver derived hormone, ANGPTL8/betatrophin, was suggested as a β cell proliferation trigger (71). Although new findings about lack of efficacy of this hormone in human islet transplantation (72) and knock-out mouse models (73) contradicted its expected utility for clinical application, the proposed possibility of endocrine regulation of β cell replication might provide an alternative approach for augmenting insulin based treatment or islet transplantation in the future. Several factors have been evaluated for their ability to promote β cell regeneration. Glucagon-like peptide-1, HGF, gastrin, epidermal growth factor (EGF) and ciliary neurotrophic factor are among these factors (74). While growth factors that promote β cell proliferation can be applied when a substantial residual β cell mass remains or has been restored, factors that promote cellular reprogramming towards a β cell fate and/or reactivate endogenous β cell progenitors are of great interest for T1D and end-stage type 2 diabetes patients. To revert to the diabetic state, a combination of exogenous regenerative stimuli and adequate immunotherapy is necessary to protect newly-formed β cells from auto-immune attacks in T1D patients.

Sub-optimal engraftment of islets

Significant portions of islets are lost in the early post-transplantation period due to apoptosis induced by damage to islets during islet preparation and after transplantation. During the islet isolation process, insults such as enzymatic damage to islets, oxidative stress and detachment of islet cells from the surrounding extracellular matrix (ECM) make them prone to apoptosis. Furthermore, while islets are transplanted within the intra-vascular space, inflammatory cytokines initiate a cascade of events that contribute to their destruction.

Improvement of pancreas procurement, islet isolation and culture techniques

The main source of islets for clinical islet transplantation is the pancreas of BDDs. Brain death causes up-regulation of pro-inflammatory cytokines in a time-dependent manner (75), hence islets are subject to different stresses during the pancreas procurement which can induce apoptosis. In the previous decades, several studies have shown that improvements in pancreas procurement, islet isolation and culture techniques result in increasing islet yield and subsequently favorable clinical outcomes. The islet isolation success rate is affected by factors such as donor characteristics, pancreas preservation, enzyme solutions, and density gradients for purification. Donor characteristics such as weight and BMI (>30) significantly affect islet yield (76, 77). Andres et al. (78) have claimed that a major pancreas injury which involves the main pancreatic duct during procurement is significantly associated with lower islet yield. In addition, the pancreas preservation method has undergone improvement in the past few years with the use of perfluorocarbon (PFC), which slowly releases oxygen. PFC in combination with University of Wisconsin (UW) solution is a two-layer method for pancreatic preservation during the cold ischemia time, which leads to a higher islet yield (77). In terms of enzyme solution effects in pancreas digestion and islet separation from acinar tissues (79, 80), although liberase HI has been determined to be very effective in pancreas digestion, its use in clinical islet isolation was discontinued due to the potential risk of bovine spongiform encephalopathy transmission (79, 80). Therefore, enzyme formulation has shifted to collagenase blend products such as a mixture of good manufacturing practice (GMP) grade collagenase and neutral protease (79, 80). The enzymes mixture and the controlled delivery of enzyme solutions into the main pancreatic duct facilitated the digestion of acinar tissue and their dispersement without islet damage (79, 81, 82).

Considering the importance of islet purification in their functionality, a number of studies have focused on improvements in islet purification methods. These methods include PentaStarch, which enters pancreatic acinar tissue and alters its density, a Biocoll-based gradient, and a COBE 2991 cell separator machine to increase post-purification islet yield (79, 80, 83). In addition, culturing the isolated, purified islets for 12–72 h causes enhancement of their purity and provides adequate time to obtain the data from islet viability assays as an important parameter in engraftment outcomes (80).

Due to the toxic nature of pancreatic acinar cells, it has been shown that islet loss after culture is higher in impure islet preparations. Supplementation of α-1 antitrypsin (A1AT) into the culture medium maintains islet cell mass and functional integrity (84). By the same mechanism, Pefabloc as a serine protease inhibitor, can inhibit serine proteases that affect islets during the isolation procedure (85). Supplementation of human islet culture medium with glial cell line-derived neurotrophic factor (GDNF) has been shown to improve human islet survival and post-transplantation function in diabetic mice (86). In addition, treatment of islets prior to transplantation by heparin and fusion proteins such as soluble TNF-α, which inhibit the inflammatory response, can improve engraftment and islet survival (79, 87, 88). The presence of human recombinant prolactin in islet culture medium improves human β cell survival (89).

Although early islet survival has been improved by the mentioned modifications, most patients require more than one islet infusion from multiple donors in order to achieve insulin independency and a functional graft over a 2–3 year period after transplantation (90). In 2014, Shapiro group et al. reported a significant association between single-donor islet transplantation and long-term insulin independence with older age and lower insulin requirements prior to transplantation (76). Moreover, higher weight and BMI of the donor resulted in a higher isolated islet mass and significant association with single-donor transplantation (76). The effectiveness of pre-transplant administration of insulin and heparin has been shown on achievement of insulin independence in single-donor islet transplantation (76).

Prevention of apoptosis, reduction of the effects of inflammatory cytokines and oxidative damage

Both intrinsic and extrinsic pathways are involved in the induction of islet apoptosis after transplantation (91). Different strategies are used to block these two pathways or the final common pathway to prevent islet apoptosis.

Several inflammatory cytokines exert detrimental effects on islets after transplantation which lead to apoptosis and death; the most important are IL1β, TNF-α and IFN-γ (92). Over-expression of IL1 receptor antagonist in islets (93), inhibition of TF NF-κB which mediates the detrimental effects of these cytokines on islets (94), inhibition of toll-like receptor 4 and blockade of high mobility group box 1 (HMGB1) with anti-HMGB1 mAb (95) are among the strategies used to inhibit inflammatory cytokines. There is decreased expression of anti-oxidants in pancreatic islets in comparison to most other tissues. Therefore, islets are sensitive to free oxygen radicals produced during the islet isolation process and after transplantation. According to research, over-expression of antioxidants such as manganese superoxide dismutase (SOD) (96) and metallothionein (97) in islets or systemic administration of antioxidants such as catalytic antioxidant redox modulator (98) protect the islets from oxidative damage. Inhibitors of inducible nitric oxide synthase are effective in protecting islets during the early post-transplantation period (99).

Prevention of anoikis

Interaction of islets with the ECM provides important survival signals that have been disrupted by enzymatic digestion of the ECM during the islet isolation process. This leads to an integrin-mediated islet cell death or anoikis (100). Integrins, located on the surface of pancreatic cells, normally bind to specific sequences of ECM proteins. Some synthetic peptide epitopes have been identified that mimic the effect of ECM proteins by binding to the integrins. Arginine-glycine-aspartic acid is the most extensively studied epitope which reduces the apoptosis rate of islets (101). Transplantation of islets in a fibroblast populated collagen matrix is also used to prevent anoikis in which fibroblasts produce fibronectin and growth factors to enhance viability and functionality of the islets (102).

Attenuating the instant blood-mediated inflammatory reaction

Islets are injected into the portal vein to reach the liver as the standard site for islet transplantation. When islets are in close contact with blood, an instant blood-mediated inflammatory reaction (IBMIR) occurs through activation of coagulation and the complement system. Platelets attach to the islet surface and leukocytes enter the islet. Finally, by formation of a clot around the islet and infiltration of different leukocyte subtypes, mainly polymorphonuclears, the integrity of the islet is disrupted (103).

Different strategies to attenuate IBMIR include inhibitors of complement and coagulation systems, coating the islet surface, and development of composite islet-endothelial cell grafts (103).

Tissue factor and macrophage chemoattractant protein (MCP-1) are among the most important mediators of IBMIR. Although culturing islets before transplantation enhances tissue factor expression in them (104), addition of nicotinamide to the culture medium significantly reduces tissue factor and MCP-1 expression (105). Islets treated with anti-tissue factor blocking antibody along with i.v. administration of this antibody to recipients after transplantation result in improved transplantation outcomes (106). These inhibitors of the coagulation cascade have been administered in order to attenuate IBMIR: (i) melagatran as a thrombin inhibitor (107), (ii) activated protein C (APC) as an anticoagulant enzyme (108) and (iii) tirofiban as a platelet glycoprotein IIb-IIIa inhibitor (109). Thrombomodulin is a proteoglycan produced by endothelial cells that induces activated protein C generation. Liposomal formulation of thrombomodulin (lipo-TM) leads to improved engraftment of islets and transplantation outcomes in the murine model (110, 111).

Retrospective evaluation of islet transplant recipients has shown that peri-transplant infusion of heparin is a significant factor associated with insulin independence and greater indices of islet engraftment (112). Low-molecular weight dextran sulfate (LMW-DS), a heparin-like anticoagulant and anti-complement agent, is an alternative to reduce IBMIR (113).

Bioengineering of the islet surface through attachment of heparin (87) and thrombomodulin (114) is an efficient technique to decrease IBMIR without increasing the risk of bleeding. Immobilization of soluble complement receptor 1 (sCR1), as a complement inhibitor on the islet surface through application of different bioengineering methods, decreases activation of the complement system that consequently leads to decreased IBMIR (115, 116). Endothelial cells prevent blood clotting, thus their co-transplantation with islets in composites has also been evaluated and proven to be an efficient strategy to attenuate IBMIR (117).

Sites of transplantation

Infusion through the portal vein is a commonly used method of islet transplantation where islets easily access oxygen and nutrients at this site. Drawbacks, however, include activation of the complement and coagulation system (IBMIR), surgical side effects such as intra-abdominal hemorrhage and portal vein thrombosis, and lack of a safe way to detect early graft rejection. BM (29) and the striated muscle, brachioradialis, (30) are alternative sites that have been tested successfully in human trials.

Lack of blood supply and oxygen delivery

Pancreatic islets are highly vascularized micro-organs with a dense network of capillaries. Despite the high demand of blood supply for intra-islet secretory cells there is a lag phase of up to 14 days for re-establishment of intra-graft blood perfusion which can contribute to a tremendous loss of functional islet mass in the early post-transplantation days. Furthermore, providing oxygen solely by gradient-driven passive diffusion during isolation and early post-transplantation can result in decreasing oxygen pressure in islets radially from the periphery to the core. In hypoxic conditions, β-cell mitochondrial oxidative pathways are compromised due to alterations in gene expression induced by activation of hypoxia-inducible factor (HIF-1α) which leads to changes from aerobic glucose metabolism to anaerobic glycolysis and nuclear pyknosis (118).

Enhancement of islet vasculature

The most prevalent strategies that enhance vascularization include the use of angiogenic growth factors, helper cells and the ECM components which we briefly discuss. Secretion of pro-angiogenic factors such as vascular endothelial growth factor (VEGF), fibroblast growth factor (FGFs), HGF, EGF and matrix metalloproteinase-9 from islets recruits the endothelial cells mostly from the recipient to form new blood vessels. Over-expression of these factors in islets or helper cells leads to accelerated revascularization of islets post-transplantation (119). According to a number of reports, a VEGF mimetic helical peptide (QK) can bind and activate VEGF receptors to enhance the revascularization process (120). Coverage of islets with an angiogenic growth factor through modification of the islet surface with an anchor molecule attracts endothelial cells and induces islet revascularization (121). Pretreatment of islets with stimulators of vascularization is another strategy (122).

Concomitant transplantation of islets with BM stem cells, vascular endothelial cells, endothelial progenitor cells (EPCs) and MSCs creates a suitable niche for promotion of revascularization and enhancement of grafted islet survival and function (123, 124, 125, 126).

ECM-based strategies can be used to enhance grafted islet vascularization. It has been shown that fibrin induces differentiation of human EPCs and provides a suitable niche for islet vascularization (127). Collagen and collagen mimetics have been used to stimulate islet vascularization (128, 129). Another possible solution is to prepare a pre-vascularized site before islet transplantation. A related novel idea is to create a sandwich comprised of two layers of pre-vascularized collagen gels around a central islet containing-collagen gel (130).

Oxygen delivery to the islets

Under hypoxic conditions, β-cell mitochondrial oxidative pathways are compromised due to alterations in gene expression induced by activation of HIF-1α. In addition, activation of HIF-1α reduces glucose uptake and changes aerobic glucose metabolism to anaerobic glycolysis. During isolation and early post-transplantation, providing oxygen solely by gradient-driven passive diffusion results in decreasing oxygen pressure in islets radially from the periphery to the core (131). Different strategies suggested to overcome the hypoxia challenge include hyperbaric oxygen (HBO) therapy (132), design of gas permeable devices (133), oxygen carrier agents (134) and in situ oxygen generators (135).

Hyperbaric oxygen therapy has been shown to mitigate hypoxic conditions during early post-islet transplantation in recipient animals frequently exposed to high pressure oxygen. This therapy improves functionality of islets transplanted intraportally or under the kidney capsule, reduces apoptosis, HIF-1α and VEGF expression, and enhances vessel maturation (132, 136).

Gas permeable devices are another strategy for oxygenation of islets during culture and transplantation. Due to hydrophobicity and oxygen permeability of silicone rubber membranes, culturing of islets on these membranes prevents hypoxia-induced death (133, 137).

Oxygen carrier agents such as hemoglobin and perfluorocarbons (PFCs) are alternative techniques to prevent hypoxia. The hemoglobin structure is susceptible to oxidization and converts to methemoglobin in the presence of hypoxia-induced free radicals and environmental radical stresses (138). Therefore, hemoglobin cross-linking and the use of antioxidant systems like ascorbate–glutathione have been employed (138). Hemoglobin conjugation with SOD and catalase (CAT), as antioxidant enzymes, can create an Hb-conjugate system (Hb–SOD–CAT) for oxygenation of islets (134). Perfluorocarbons are biologically inert and non-polar substances where all hydrogens are substituted by fluorine in the hydrocarbon chains without any reaction with proteins or enzymes in the biological environment (139). O2, CO2 and N2 can be physically dissolved in PFCs which lead to more rapid oxygen release from this structure compared to oxyhemoglobin (140, 141). Perflurorcarbons have been applied to oxygenate islets in culture, in addition to fibrin matrix as an oxygen diffusion enhancing medium to hinder hypoxia induced by islet encapsulation (142).

Hydration of solid peroxide can be an effective way for in situ generation of oxygen. Encapsulation of solid peroxide in polydimethylsiloxane (PDMS) as a hydrophobic polymer reduces the rate of hydration and provides sustained release of oxygen. Through this approach, metabolic function and glucose-dependent insulin secretion of the MIN6 cell line and islet cells under hypoxic in vitro conditions have been retained (135).

Alleviating hypoxia for protection of normal islet function results in reduced expression of pro-angiogenic factors and delayed revascularization (118). Therefore, hypoxia prevention methods are necessary to apply in combination with other methods to increase the islet revascularization process.

Immune rejection of transplanted islets

After allogeneic islet transplantation, both allogenic immune reactions and previously existing autoimmunity against islets contribute to allograft rejection. The ideal immune-modulation or immune-isolation approach should target both types of immune reactions.

Central tolerance induction

Central tolerance is achieved when B and T cells are rendered non-reactive to self in primary lymphoid organs, BM and the thymus by presentation of donor alloantigens to these organs. BM transplantation and intra-thymic inoculation of recipient antigen presenting cells (APCs) pulsed with donor islet antigens (143) have been successfully tested to develop central tolerance. Hematopoietic chimerism induced by body irradiation followed by BM transplantation eliminates alloimmune reactions (144, 145). To reduce the toxic effects of irradiation, a sub-lethal dose can be combined with co-stimulatory blockade or neutralizing antibodies to induce mixed hematopoietic tolerance (146).

Suppressor cells: tolerogenic dendritic cells, regulatory T cells and MSCs

Different suppressor cells are candidates to induce peripheral immune tolerance. Although tolerogenic dendritic cells (tol-DCs) are potent APCs that present antigens to T cells, they fail to present the adequate co-stimulatory signal or deliver net co-inhibitory signals. The major characteristics of tol-DCs include low production of interleukin-12p70 and high production of IL10 and indoleamine 2,3-dioxygenase (IDO), as well as the ability to generate alloantigen-specific regulatory T cells (Tregs) and promote apoptotic death of effector T cells (reviewed in (147)). These characteristics make tol-DCs good candidates for induction of immune tolerance in recipients of allogenic islets.

Application of donor tol-DCs mostly suppresses the direct allorecognition pathway while recipient tol-DCs pulsed with donor antigens prevent indirect allorecognition and chronic rejection of islets. These cells are not clinically favorable for transplantation from deceased donors because of the number of culture days needed to prepare donor derived DCs (147). Giannoukakis et al. (148) have conducted a phase I clinical trial on T1D patients and reported the safety and tolerability of autologous DCs in a native state or directed ex vivo toward a tolerogenic immunosuppressive state.

Blockade of NF-κB has been employed to maintain DCs in an immature state for transplantation. Blockade of co-stimulatory molecules, CD80 (B7-1) and CD86 (B7-2) on DCs (149), genetic modification of DCs with genes encoding immunoregulatory molecules such as IL10 and TGF-β (150, 151), and treatment of DCs with vitamin D3 (152) are among approaches to induce tol-DCs. Uptake of apoptotic cells by DCs converts these cells to tol-DCs that are resistant to maturation and able to induce Tregs (153). Due to limitations in clinical application of in vitro induced tol-DCs, systemic administration of either donor cells undergoing early apoptosis (154) or DC-derived exosomes (155) are more feasible approaches to induce donor allopeptide specific tol-DCs in situ.

Tregs are a specialized subpopulation of CD4+ T cells that participate in maintenance of immunological homeostasis and induction of tolerance to self-antigens. These cells hold promise as treatment of autoimmune diseases and prevention of transplantation rejection. Naturally occurring Tregs (nTregs) are selected in the thymus and represent ∼5–10% of total CD4+ T cells in the periphery. Type 1 regulatory T (Tr1) cells are a subset of induced Tregs (iTregs) induced in the periphery after encountering an antigen in the presence of IL10. They regulate immune responses through secretion of immunosuppressive cytokines IL10 and TGF-β (156).

It has been shown that antigen-specific Tr1 cells are more potent in induction of tolerance in islet transplantation compared to polyclonal Tr1 cells (157). Similarly, antigen-specificity of nTregs is an important factor in controlling autoimmunity and prevention of graft rejection in islet transplantation (158). Co-transplantation of islets and recipient Tregs induced in vitro through incubation of recipient CD4+ T cells with donor DCs in the presence of IL2 and TGF-β1 (159) or donor DCs conditioned with rapamycin (160) are effective in prevention of islet allograft rejection. Donor specific Tr1 cells can be induced in vivo through administration of IL10 and rapamycin to islet transplant recipients (161). Coating human pancreatic islets with CD4+ CD25high CD127 Treg cells has been used as a novel approach for the local immunoprotection of islets (162). The chemokine CCL22 can be used to recruit the endogenous Tregs toward islets in order to prevent an immune attack against them (163). Regulatory B cells can induce Tregs and contribute to tolerance induction against pancreatic islets by secretion of TGF-β (164). Attenuation of donor reactive T cells increases the efficacy of Tregs therapy in prevention of islet allograft rejection (165).

Several studies have proven the immunomodulatory effects of MSCs and efficacy of these cells to preserve islets from immune attack when co-transplanted (166, 167, 168, 169, 170). Different immunosuppressive mechanisms proposed for MSCs include Th1 suppression (167), Th1 to Th2 shift (166), reduction of CD25 surface expression on responding T-cells through MMP-2 and 9 (169), marked reduction of memory T cells (166), enhancement of IL10 producing CD4+ T cells (167), increase in peripheral blood Treg numbers (168), suppression of DC maturation and endocytic activity of these cells (166), as well as reduction of pro-inflammatory cytokines such as IFN-γ (170). An ongoing phase 1/2 clinical trial in China has assessed the safety and efficacy of intra-portal co-transplantation of islets and MSCs (ClinicalTrials.gov, identifier: NCT00646724).

Signal modification: co-stimulatory and trafficking signals

In addition to the signal coded by interaction of the peptide-MHC complex on APCs with T cell receptors, secondary co-stimulatory signals such as the B7-CD28 and CD40-CD154 families are needed for complete activation of T cells.

While CTLA4 is expressed on T cells its interaction with B7 family molecules transmits a tolerogenic signal. Efficacy of CTLA4-Ig to prevent rejection of transplanted islets has been proven in both rodents and clinical studies (171, 172). B7H4 is a co-inhibitory molecule of the B7 family expressed on APCs that interacts with CD28 on T cells. Over-expression of B7H4 in islets has been shown to increase their survival in a murine model of islet transplantation (173, 174).

Interaction of CD40 on APCs with CD40L (CD154) on T cells indirectly increases B7-CD28 signaling, enhances inflammatory cytokines, and activates T cell responses. Although blockade of B7-CD28 and CD40-CD154 pathways by CTLA4-Ig and anti-CD154 antibody can enhance the survival of islets in a mouse model of islet transplantation, rejection eventually occurs. This rejection may be due to the compensatory increase of another co-stimulatory signal through interaction of inducible co-stimulator (ICOS) on T cells with B7-related protein-1 (B7RP-1) on APCs. The combination of anti-ICOS mAb to the previous treatments increases islet survival (175).

Prevention of migration and recruitment of pro-inflammatory immune cells into the islets has emerged as an effective approach for inhibition of graft rejection. Expressions of chemokines such as RANTES (CCL5), IP-10 (CXCL10), I-TAC (CXCL11), MCP-1 (CCL2), and MIP-1 (CCL3) increase islet allograft rejection compared to isografts (176).

CXCL1 is highly released by mouse islets in culture and its serum concentration is increased within 24 h after intra-portal infusion of islets, as with CXCL8, the human homolog of CXCL1. Pharmacological blockade of CXCR1/2 (the chemokine receptor for CXCL1 and CXCL8) by reparixin has been shown to improve islet transplantation outcome both in a mouse model and in the clinical setting (177).

Encapsulation strategies

Encapsulated islets are surrounded by semi-permeable layers that allow diffusion of nutrients, oxygen, glucose and insulin while preventing entry of immune cells and large molecules such as antibodies. Three major devices developed for islet immune-isolation include intravascular macrocapsules, extravascular macrocapsules and microcapsules. Clinical application of intravascular macrocapsule devices is limited due to the risk of thrombosis, infection and need for major transplantation surgery (178, 179, 180). Extravascular devices are more promising as they can be implanted during minor surgery. These devices have a low surface-to-volume ratio; hence there is a limitation in seeding density of cells for sufficient diffusion of nutrients (181).

Microencapsulation surrounds a single islet or small groups of islets as a sheet or sphere. Due to the high surface to volume ratio, microcapsules have the advantage of high oxygen and nutrient transport rates. Although preliminary results in transplantation of encapsulated islets have shown promising results, further application in large animals is challenging due to the large implant size. Living Cell Technologies (LCT) uses the microencapsulation approach for immunoisolation of porcine pancreatic islet cells. The LCT clinical trial report in 1995–1996 has shown that porcine islets within alginate microcapsules remained viable after 9.5 years in one out of nine recipients. More recent clinical studies by this company have revealed that among seven patients who received encapsulated porcine islets, two became insulin independent. Currently, LCT is performing a phase IIb clinical trial with the intent to commercialize this product in 2016. Unlike microspheres, thin sheets have the advantages of high diffusion capacity of vital molecules and retrievability (182). Islet Sheet Medical is an islet-containing sheet made from alginate which has successfully passed the preclinical steps of development. A clinical trial will be started in the near future (161).

Recently, engineered macrodevices have attracted attention for islet immunoisolation. Viacyte Company has designed a net-like structure that encapsulates islet-like cells derived from hESCs. After promising results in an animal model, Viacyte began a clinical trial in 2014 (157). Another recent technology is Beta-O2, an islet-containing alginate macrocapsule surrounded by Teflon membrane that protects cells from the recipient immune system (158). Benefits of Beta-O2 include supplying oxygen with an oxygenated chamber around the islet-containing module. Its clinical application has shown that the device supports islet viability and function for at least 10 months after transplantation (183).

Immune suppression medication regimens

Induction of immunosuppression is an important factor that determines the durability of insulin independence. Daclizumab (IL2R antibody) has been widely used to induce immunosuppression in years after the Edmonton protocol. Although the primary results were promising, long-term insulin independence was a challenge to this regimen. Bellin et al. compared the long-term insulin independence in four groups of islet transplanted patients with different induction immunosuppressant therapies. Maintenance immunosuppressives were approximately the same in all groups and consisted of a calcineurin inhibitor, tacrolimus or cyclosporine, plus mycophenolate mofetil or a mammalian target of rapamycin (mTOR) inhibitor(sirolimus). The 5-year insulin independence was 50% for the group of patients that received anti-CD3 antibody (teplizumab) alone or T-cell depleting antibody (TCDAb), ATG, plus TNF-α inhibitor (TNF-α-i), etanercept, as the induction immunosuppressant. The next two groups that received TCDAb (ATG or alemtuzumab) with or without TNF-α-i had 5-year insulin independence rates of 50 and 0% respectively. The last group that received daclizumab as the induction immunosuppressant had a 5-year insulin independence rate of 20% (15). This study showed that potent induction immunosuppression (PII) regimens could improve long-term results of islet transplantation. This might be due to stronger protection of islets during early post-transplant and engraftment of a higher proportion of transplanted islets. Constant overstimulation of an inadequately low islet mass could cause their apoptosis. This would explain the unfavorable long-term insulin independence rate for daclizumab as the induction immunosuppressant.

On the other hand, anti-CD3, ATG and alemtuzumab may help to restore immunological tolerance towards islet antigens by enhancing Treg cells and shift the balance away from effector cells towards a tolerogenic phenotype (184, 185). Toso et al. have studied the frequency of different fractions of immune cells within peripheral blood of islet recipients compared after induction of immunosuppression using either a depleting agent (alemtuzumab or ATG) or a non-depleting antibody (daclizumab). Both alemtuzumab and ATG led to prolonged lymphocyte depletion, mostly in CD4+ cells. Unlike daclizumab, alemtuzumab induced a transient reversible increase in relative frequency of Treg cells and a prolonged decrease in frequency of memory B cells (185). Positive effect of alemtuzumab on Treg cells has been further proved by in vitro exposure of peripheral blood mononuclear cells to this immunosuppressant (186). An anti-CD3 mAb was also shown to induce regulatory CD8+CD25+ T cells both in vitro and in patients with T1D (184).

In the study of Bellin et al., co-administration of TNF-α inhibitior at induction led to a higher insulin independence rate. This result could be attributed to the protective effect of the TNF-α inhibitior against detrimental action of TNF-α on transplanted islets at the time of infusion (187) in addition to its inducing impact on Treg expansion (188).

For the maintenance of immunosuppression, the Edmonton group used sirolimus (a macrolide antibiotic which inhibits mTOR) and tacrolimus (a calcineurin inhibitor). Tacrolimus has been shown to have toxicity on nephrons, neurons and β cells (189), and inhibit spontaneous proliferation of β cells (65). Froud et al. (189) showed that substitution of tacrolimus with mycophenolatemofetil (MMF) in an islet recipient with tacrolimus-induced-neurotoxicity resulted in resolution of symptoms, as well as an immediate improvement in glycemic control. Unlike MMF, tacrolimus has been shown to impair insulin exocytosis and disturb human islet graft function in diabetic NOD-scid mice (190). MMF is now more commonly used in islet transplantation clinical trials.

A relatively new generation of immunosuppressants relies on blockade of co-stimulation signaling of T cells. Abatacept (CTLA-4Ig) and belatacept (LEA29Y) – a high affinity mutant form of CTLA-4Ig, selectively block T-cell activation through linking to B7 family on APCs and prevent interaction of the B7 family with CD28 on T cells (191). Substitution of tacrolimus with belatacept in combination with sirolimus or MMF, as the maintenance therapy, and ATG, as the induction immunosuppressant, has been tested in clinical islet transplantation. All five patients treated with this protocol achieved insulin independence after a single transplant (171). In another study, successful substitution of tacrolimus with efalizumab, an anti-leukocyte function-associated antigen-1 (LFA-1) antibody, was reported for maintenance of an immunosuppressant regimen of islet transplant patients. However, as this medication was withdrawn from the market in 2009, long-term evaluation was not possible (192).

In the current clinical settings, islets are transplanted into the portal vein. Oral immunosuppressants first pass through the portal system after which their concentration increases dramatically in the portal vein where the islets reside (193). This phenomenon may impose adverse toxic effects on islets. Therefore, other routes of administration of immunosuppressants may be preferable for islet transplantation.

Conclusion

Even if all BDD pancreata can be successfully used for single donor allogeneic islet transplantation, abundant β cell sources are required to meet the needs to treat all diabetic patients. Therefore, investigating alternative sources of β cells obtained by either differentiation or transdifferentiation, as well as xenogenic islet sources is of great importance.

Low islet quality, anoikis, oxidative damage, apoptosis, effect of inflammatory cytokines, hypovascularization and hypoxia as well as activation of the coagulation and complement system contribute to limited engraftment of islets after transplantation. A combined approach applying the different aforementioned strategies to overcome these detrimental factors is probably necessary to optimize the engraftment rate of the transplanted islets. Recent advances in immunosuppressive medications have led to improved long-term outcome of islet transplantation. However, the final goal is to find a permanent treatment that induces/mediates tolerance of the immune system against the transplanted islet antigens.

Declaration of interest

The authors declare that there is no conflict of interest that could be perceived as prejudicing the impartiality of the review.

Funding

This study was funded by a grant provided by Royan Institute.

Author contribution statement

M Khosravi-Maharlooei, E Hajizadeh-Saffar, Y Tahamtani, M Basiri, L Montazeri, K Khalooghi, M Kazemi Ashtiani, A Farrokhi, N Aghdami, A Sadr Hashemi Nejad and N De Leu wrote the manuscript, contributed to the discussion. M-B Larijani contributed to the discussion and reviewed/edited the manuscript. H Heimberg, X Luo, and H Baharvand wrote the manuscript, contributed to the discussion, reviewed/edited the manuscript.

Acknowledgements

We thank the members of the Beta Cell Research Program at Royan Institute for their helpful suggestions and critical reading of the manuscript.

References

  • 1

    . The effect of intensive treatment of diabetes on the development and progression of long-term complications in insulin-dependent diabetes mellitus. The Diabetes Control and Complications Trial Research Group. New England Journal of Medicine 1993 329 977986. (doi:10.1056/NEJM199309303291401).

    • Search Google Scholar
    • Export Citation
  • 2

    Tavakoli A, Liong S. Pancreatic transplant in diabetes. Advances in Experimental Medicine and Biology 2012 771 420437.

  • 3

    Najarian JS, Sutherland DE, Matas AJ, Steffes MW, Simmons RL, Goetz FC. Human islet transplantation: a preliminary report. Transplantation Proceedings 1977 9 233236.

    • Search Google Scholar
    • Export Citation
  • 4

    Ricordi C, Lacy PE, Scharp DW. Automated islet isolation from human pancreas. Diabetes 1989 38 (Suppl 1) 140142. (doi:10.2337/diab.38.1.S140).

    • Search Google Scholar
    • Export Citation
  • 5

    Shapiro AM, Lakey JR, Ryan EA, Korbutt GS, Toth E, Warnock GL, Kneteman NM, Rajotte RV. Islet transplantation in seven patients with type 1 diabetes mellitus using a glucocorticoid-free immunosuppressive regimen. New England Journal of Medicine 2000 343 230238. (doi:10.1056/NEJM200007273430401).

    • Search Google Scholar
    • Export Citation
  • 6

    Ryan EA, Lakey JR, Rajotte RV, Korbutt GS, Kin T, Imes S, Rabinovitch A, Elliott JF, Bigam D, Kneteman NM et al.. Clinical outcomes and insulin secretion after islet transplantation with the Edmonton protocol. Diabetes 2001 50 710719. (doi:10.2337/diabetes.50.4.710).

    • Search Google Scholar
    • Export Citation
  • 7

    Ryan EA, Paty BW, Senior PA, Bigam D, Alfadhli E, Kneteman NM, Lakey JR, Shapiro AM. Five-year follow-up after clinical islet transplantation. Diabetes 2005 54 20602069. (doi:10.2337/diabetes.54.7.2060).

    • Search Google Scholar
    • Export Citation
  • 8

    Hering BJ, Kandaswamy R, Harmon JV, Ansite JD, Clemmings SM, Sakai T, Paraskevas S, Eckman PM, Sageshima J, Nakano M et al.. Transplantation of cultured islets from two-layer preserved pancreases in type 1 diabetes with anti-CD3 antibody. American Journal of Transplantation 2004 4 390401. (doi:10.1046/j.1600-6143.2003.00351.x).

    • Search Google Scholar
    • Export Citation
  • 9

    Hering BJ, Kandaswamy R, Ansite JD, Eckman PM, Nakano M, Sawada T, Matsumoto I, Ihm SH, Zhang HJ, Parkey J et al.. Single-donor, marginal-dose islet transplantation in patients with type 1 diabetes. Journal of the American Medical Association 2005 293 830835. (doi:10.1001/jama.293.7.830).

    • Search Google Scholar
    • Export Citation
  • 10

    Warnock GL, Meloche RM, Thompson D, Shapiro RJ, Fung M, Ao Z, Ho S, He Z, Dai LJ, Young L et al.. Improved human pancreatic islet isolation for a prospective cohort study of islet transplantation vs best medical therapy in type 1 diabetes mellitus. Archives of Surgery 2005 140 735744. (doi:10.1001/archsurg.140.8.735).

    • Search Google Scholar
    • Export Citation
  • 11

    Warnock GL, Thompson DM, Meloche RM, Shapiro RJ, Ao Z, Keown P, Johnson JD, Verchere CB, Partovi N, Begg IS et al.. A multi-year analysis of islet transplantation compared with intensive medical therapy on progression of complications in type 1 diabetes. Transplantation 2008 86 17621766. (doi:10.1097/TP.0b013e318190b052).

    • Search Google Scholar
    • Export Citation
  • 12

    Leitao CB, Tharavanij T, Cure P, Pileggi A, Baidal DA, Ricordi C, Alejandro R. Restoration of hypoglycemia awareness after islet transplantation. Diabetes Care 2008 31 21132115. (doi:10.2337/dc08-0741).

    • Search Google Scholar
    • Export Citation
  • 13

    Tharavanij T, Betancourt A, Messinger S, Cure P, Leitao CB, Baidal DA, Froud T, Ricordi C, Alejandro R. Improved long-term health-related quality of life after islet transplantation. Transplantation 2008 86 11611167. (doi:10.1097/TP.0b013e31818a7f45).

    • Search Google Scholar
    • Export Citation
  • 14

    Barton FB, Rickels MR, Alejandro R, Hering BJ, Wease S, Naziruddin B, Oberholzer J, Odorico JS, Garfinkel MR, Levy M et al.. Improvement in outcomes of clinical islet transplantation: 1999–2010. Diabetes Care 2012 35 14361445. (doi:10.2337/dc12-0063).

    • Search Google Scholar
    • Export Citation
  • 15

    Bellin MD, Barton FB, Heitman A, Harmon JV, Kandaswamy R, Balamurugan AN, Sutherland DE, Alejandro R, Hering BJ. Potent induction immunotherapy promotes long-term insulin independence after islet transplantation in type 1 diabetes. American Journal of Transplantation 2012 12 15761583. (doi:10.1111/j.1600-6143.2011.03977.x).

    • Search Google Scholar
    • Export Citation
  • 16

    Markmann JF, Deng S, Desai NM, Huang X, Velidedeoglu E, Frank A, Liu C, Brayman KL, Lian MM, Wolf B et al.. The use of non-heart-beating donors for isolated pancreatic islet transplantation. Transplantation 2003 75 14231429. (doi:10.1097/01.TP.0000061119.32575.F4).

    • Search Google Scholar
    • Export Citation
  • 17

    Dufrane D, Gianello P. Pig islet for xenotransplantation in human: structural and physiological compatibility for human clinical application. Transplantation Reviews 2012 26 183188. (doi:10.1016/j.trre.2011.07.004).

    • Search Google Scholar
    • Export Citation
  • 18

    van der Windt DJ, Bottino R, Kumar G, Wijkstrom M, Hara H, Ezzelarab M, Ekser B, Phelps C, Murase N, Casu A et al.. Clinical islet xenotransplantation: how close are we? Diabetes 2012 61 30463055. (doi:10.2337/db12-0033).

    • Search Google Scholar
    • Export Citation
  • 19

    Van Hoof D, D'Amour KA, German MS. Derivation of insulin-producing cells from human embryonic stem cells. Stem Cell Research 2009 3 7387. (doi:10.1016/j.scr.2009.08.003).

    • Search Google Scholar
    • Export Citation
  • 20

    Pagliuca FW, Melton DA. How to make a functional β-cell. Development 2013 140 24722483. (doi:10.1242/dev.093187).

  • 21

    Miyazaki S, Yamato E, Miyazaki J. Regulated expression of pdx-1 promotes in vitro differentiation of insulin-producing cells from embryonic stem cells. Diabetes 2004 53 10301037. (doi:10.2337/diabetes.53.4.1030).

    • Search Google Scholar
    • Export Citation
  • 22

    Xu H, Tsang KS, Chan JC, Yuan P, Fan R, Kaneto H, Xu G. The combined expression of Pdx1 and MafA with either Ngn3 or NeuroD improve the differentiation efficiency of mouse embryonic stem cells into insulin-producing cells. Cell Transplantation 2013 22 147158. (doi:10.3727/096368912X653057).

    • Search Google Scholar
    • Export Citation
  • 23

    Blyszczuk P, Czyz J, Kania G, Wagner M, Roll U, St-Onge L, Wobus AM. Expression of Pax4 in embryonic stem cells promotes differentiation of nestin-positive progenitor and insulin-producing cells. PNAS 2003 100 9981003. (doi:10.1073/pnas.0237371100).

    • Search Google Scholar
    • Export Citation
  • 24

    Morris SA, Cahan P, Li H, Zhao AM, San Roman AK, Shivdasani RA, Collins JJ, Daley GQ. Dissecting engineered cell types and enhancing cell fate conversion via CellNet. Cell 2014 158 889902. (doi:10.1016/j.cell.2014.07.021).

    • Search Google Scholar
    • Export Citation
  • 25

    Xu Y, Shi Y, Ding S. A chemical approach to stem-cell biology and regenerative medicine. Nature 2008 453 338344. (doi:10.1038/nature07042).

  • 26

    Pagliuca FW, Millman JR, Gurtler M, Segel M, Van Dervort A, Ryu JH, Peterson QP, Greiner D, Melton DA. Generation of functional human pancreatic β cells in vitro. Cell 2014 159 428439. (doi:10.1016/j.cell.2014.09.040).

    • Search Google Scholar
    • Export Citation
  • 27

    Rezania A, Bruin JE, Arora P, Rubin A, Batushansky I, Asadi A, O'Dwyer S, Quiskamp N, Mojibian M, Albrecht T et al.. Reversal of diabetes with insulin-producing cells derived in vitro from human pluripotent stem cells. Nature Biotechnology 2014 32 11211133. (doi:10.1038/nbt.3033).

    • Search Google Scholar
    • Export Citation
  • 28

    Schulz TC, Young HY, Agulnick AD, Babin MJ, Baetge EE, Bang AG, Bhoumik A, Cepa I, Cesario RM, Haakmeester C et al.. A scalable system for production of functional pancreatic progenitors from human embryonic stem cells. PLoS ONE 2012 7 e37004. (doi:10.1371/journal.pone.0037004).

    • Search Google Scholar
    • Export Citation
  • 29

    Rong Z, Wang M, Hu Z, Stradner M, Zhu S, Kong H, Yi H, Goldrath A, Yang YG, Xu Y et al.. An effective approach to prevent immune rejection of human ESC-derived allografts. Cell Stem Cell 2014 14 121130. (doi:10.1016/j.stem.2013.11.014).

    • Search Google Scholar
    • Export Citation
  • 30

    Szot GL, Yadav M, Lang J, Kroon E, Kerr J, Kadoya K, Brandon EP, Baetge EE, Bour-Jordan H, Bluestone JA. Tolerance induction and reversal of diabetes in mice transplanted with human embryonic stem cell-derived pancreatic endoderm. Cell Stem Cell 2015 16 148157. (doi:10.1016/j.stem.2014.12.001).

    • Search Google Scholar
    • Export Citation
  • 31

    Yarborough M, Tempkin T, Nolta J, Joyce N. The complex ethics of first in human stem cell clinical trials. AJOB Neuroscience 2012 3 1416. (doi:10.1080/21507740.2012.675010).

    • Search Google Scholar
    • Export Citation
  • 32

    Zhang D, Jiang W, Liu M, Sui X, Yin X, Chen S, Shi Y, Deng H. Highly efficient differentiation of human ES cells and iPS cells into mature pancreatic insulin-producing cells. Cell Research 2009 19 429438. (doi:10.1038/cr.2009.28).

    • Search Google Scholar
    • Export Citation
  • 33

    Zhao T, Zhang ZN, Rong Z, Xu Y. Immunogenicity of induced pluripotent stem cells. Nature 2011 474 212215. (doi:10.1038/nature10135).

  • 34

    Kim K, Doi A, Wen B, Ng K, Zhao R, Cahan P, Kim J, Aryee MJ, Ji H, Ehrlich LI et al.. Epigenetic memory in induced pluripotent stem cells. Nature 2010 467 285290. (doi:10.1038/nature09342).

    • Search Google Scholar
    • Export Citation
  • 35

    Lister R, Pelizzola M, Kida YS, Hawkins RD, Nery JR, Hon G, Antosiewicz-Bourget J, O'Malley R, Castanon R, Klugman S et al.. Hotspots of aberrant epigenomic reprogramming in human induced pluripotent stem cells. Nature 2011 471 6873. (doi:10.1038/nature09798).

    • Search Google Scholar
    • Export Citation
  • 36

    Okita K, Matsumura Y, Sato Y, Okada A, Morizane A, Okamoto S, Hong H, Nakagawa M, Tanabe K, Tezuka K et al.. A more efficient method to generate integration-free human iPS cells. Nature Methods 2011 8 409412. (doi:10.1038/nmeth.1591).

    • Search Google Scholar
    • Export Citation
  • 37

    Meng F, Chen S, Miao Q, Zhou K, Lao Q, Zhang X, Guo W, Jiao J. Induction of fibroblasts to neurons through adenoviral gene delivery. Cell Research 2012 22 436440. (doi:10.1038/cr.2011.185).

    • Search Google Scholar
    • Export Citation
  • 38

    Yoshioka N, Gros E, Li HR, Kumar S, Deacon DC, Maron C, Muotri AR, Chi NC, Fu XD, Yu BD et al.. Efficient generation of human iPSCs by a synthetic self-replicative RNA. Cell Stem Cell 2013 13 246254. (doi:10.1016/j.stem.2013.06.001).

    • Search Google Scholar
    • Export Citation
  • 39

    Warren L, Manos PD, Ahfeldt T, Loh YH, Li H, Lau F, Ebina W, Mandal PK, Smith ZD, Meissner A et al.. Highly efficient reprogramming to pluripotency and directed differentiation of human cells with synthetic modified mRNA. Cell Stem Cell 2010 7 618630. (doi:10.1016/j.stem.2010.08.012).

    • Search Google Scholar
    • Export Citation
  • 40

    Mandal PK, Rossi DJ. Reprogramming human fibroblasts to pluripotency using modified mRNA. Nature Protocols 2013 8 568582. (doi:10.1038/nprot.2013.019).

    • Search Google Scholar
    • Export Citation
  • 41

    Kim D, Kim C-H, Moon J-I, Chung Y-G, Chang M-Y, Han B-S, Ko S, Yang E, Cha KY, Lanza R et al.. Generation of human induced pluripotent stem cells by direct delivery of reprogramming proteins. Cell Stem Cell 2009 4 472476. (doi:10.1016/j.stem.2009.05.005).

    • Search Google Scholar
    • Export Citation
  • 42

    Yusa K, Rad R, Takeda J, Bradley A. Generation of transgene-free induced pluripotent mouse stem cells by the piggyBac transposon. Nature Methods 2009 6 363369. (doi:10.1038/nmeth.1323).

    • Search Google Scholar
    • Export Citation
  • 43

    Okano H, Nakamura M, Yoshida K, Okada Y, Tsuji O, Nori S, Ikeda E, Yamanaka S, Miura K. Steps toward safe cell therapy using induced pluripotent stem cells. Circulation Research 2013 112 523533. (doi:10.1161/CIRCRESAHA.111.256149).

    • Search Google Scholar
    • Export Citation
  • 44

    Taylor CJ, Peacock S, Chaudhry AN, Bradley JA, Bolton EM. Generating an iPSC bank for HLA-matched tissue transplantation based on known donor and recipient HLA types. Cell Stem Cell 2012 11 147152. (doi:10.1016/j.stem.2012.07.014).

    • Search Google Scholar
    • Export Citation
  • 45

    Burt RK, Loh Y, Pearce W, Beohar N, Barr WG, Craig R, Wen Y, Rapp JA, Kessler J. Clinical applications of blood-derived and marrow-derived stem cells for nonmalignant diseases. Journal of the American Medical Association 2008 299 925936. (doi:10.1001/jama.299.8.925).

    • Search Google Scholar
    • Export Citation
  • 46

    Ianus A, Holz GG, Theise ND, Hussain MA. In vivo derivation of glucose-competent pancreatic endocrine cells from bone marrow without evidence of cell fusion. Journal of Clinical Investigation 2003 111 843850. (doi:10.1172/JCI200316502).

    • Search Google Scholar
    • Export Citation
  • 47

    Hasegawa Y, Ogihara T, Yamada T, Ishigaki Y, Imai J, Uno K, Gao J, Kaneko K, Ishihara H, Sasano H et al.. Bone marrow (BM) transplantation promotes β-cell regeneration after acute injury through BM cell mobilization. Endocrinology 2007 148 20062015. (doi:10.1210/en.2006-1351).

    • Search Google Scholar
    • Export Citation
  • 48

    Hess D, Li L, Martin M, Sakano S, Hill D, Strutt B, Thyssen S, Gray DA, Bhatia M. Bone marrow-derived stem cells initiate pancreatic regeneration. Nature Biotechnology 2003 21 763770. (doi:10.1038/nbt841).

    • Search Google Scholar
    • Export Citation
  • 49

    Chen L-B, Jiang X-B, Yang L. Differentiation of rat marrow mesenchymal stem cells into pancreatic islet β-cells. World Journal of Gastroenterology 2004 10 30163020.

    • Search Google Scholar
    • Export Citation
  • 50

    Wu X-H, Liu C-P, Xu K-F, Mao X-D, Zhu J, Jiang J-J, Cui D, Zhang M, Xu Y, Liu C. Reversal of hyperglycemia in diabetic rats by portal vein transplantation of islet-like cells generated from bone marrow mesenchymal stem cells. World Journal of Gastroenterology 2007 13 33423349. (doi:10.1155/2014/757461).

    • Search Google Scholar
    • Export Citation
  • 51

    Chao KC, Chao KF, Fu YS, Liu SH. Islet-like clusters derived from mesenchymal stem cells in Wharton's Jelly of the human umbilical cord for transplantation to control type 1 diabetes. PLoS ONE 2008 3 e1451. (doi:10.1371/journal.pone.0001451).

    • Search Google Scholar
    • Export Citation
  • 52

    Lin H-Y, Tsai C-C, Chen L-L, Chiou S-H, Wang Y-J, Hung S-C. Fibronectin and laminin promote differentiation of human mesenchymal stem cells into insulin producing cells through activating Akt and ERK. Journal of Biomedical Science 2010 17 56. (doi:10.1186/1423-0127-17-56).

    • Search Google Scholar
    • Export Citation
  • 53

    Pournasr B, Khaloughi K, Salekdeh GH, Totonchi M, Shahbazi E, Baharvand H. Concise review: alchemy of biology: generating desired cell types from abundant and accessible cells. Stem Cells 2011 29 19331941. (doi:10.1002/stem.760).

    • Search Google Scholar
    • Export Citation
  • 54

    Hickey RD, Galivo F, Schug J, Brehm MA, Haft A, Wang Y, Benedetti E, Gu G, Magnuson MA, Shultz LD et al.. Generation of islet-like cells from mouse gall bladder by direct ex vivo reprogramming. Stem Cell Research 2013 11 503515. (doi:10.1016/j.scr.2013.02.005).

    • Search Google Scholar
    • Export Citation
  • 55

    Mauda-Havakuk M, Litichever N, Chernichovski E, Nakar O, Winkler E, Mazkereth R, Orenstein A, Bar-Meir E, Ravassard P, Meivar-Levy I et al.. Ectopic PDX-1 expression directly reprograms human keratinocytes along pancreatic insulin-producing cells fate. PLoS ONE 2011 6 e26298. (doi:10.1371/journal.pone.0026298).

    • Search Google Scholar
    • Export Citation
  • 56

    Watada H, Kajimoto Y, Miyagawa J, Hanafusa T, Hamaguchi K, Matsuoka T, Yamamoto K, Matsuzawa Y, Kawamori R, Yamasaki Y. PDX-1 induces insulin and glucokinase gene expressions in αTC1 clone 6 cells in the presence of betacellulin. Diabetes 1996 45 18261831. (doi:10.2337/diab.45.12.1826).

    • Search Google Scholar
    • Export Citation
  • 57

    Serup P, Jensen J, Andersen FG, Jorgensen MC, Blume N, Holst JJ, Madsen OD. Induction of insulin and islet amyloid polypeptide production in pancreatic islet glucagonoma cells by insulin promoter factor 1. PNAS 1996 93 90159020. (doi:10.1073/pnas.93.17.9015).

    • Search Google Scholar
    • Export Citation
  • 58

    Ber I, Shternhall K, Perl S, Ohanuna Z, Goldberg I, Barshack I, Benvenisti-Zarum L, Meivar-Levy I, Ferber S. Functional, persistent, and extended liver to pancreas transdifferentiation. Journal of Biological Chemistry 2003 278 3195031957. (doi:10.1074/jbc.M303127200).

    • Search Google Scholar
    • Export Citation
  • 59

    Ferber S, Halkin A, Cohen H, Ber I, Einav Y, Goldberg I, Barshack I, Seijffers R, Kopolovic J, Kaiser N et al.. Pancreatic and duodenal homeobox gene 1 induces expression of insulin genes in liver and ameliorates streptozotocin-induced hyperglycemia. Nature Medicine 2000 6 568572. (doi:10.1038/75050).

    • Search Google Scholar
    • Export Citation
  • 60

    Pennarossa G, Maffei S, Campagnol M, Tarantini L, Gandolfi F, Brevini TA. Brief demethylation step allows the conversion of adult human skin fibroblasts into insulin-secreting cells. PNAS 2013 110 89488953. (doi:10.1073/pnas.1220637110).

    • Search Google Scholar
    • Export Citation
  • 61

    Li K, Zhu S, Russ HA, Xu S, Xu T, Zhang Y, Ma T, Hebrok M, Ding S. Small molecules facilitate the reprogramming of mouse fibroblasts into pancreatic lineages. Cell Stem Cell 2014 14 228236. (doi:10.1016/j.stem.2014.01.006).

    • Search Google Scholar
    • Export Citation
  • 62

    Zhou Q, Brown J, Kanarek A, Rajagopal J, Melton DA. In vivo reprogramming of adult pancreatic exocrine cells to β-cells. Nature 2008 455 627632. (doi:10.1038/nature07314).

    • Search Google Scholar
    • Export Citation
  • 63

    Banga A, Akinci E, Greder LV, Dutton JR, Slack JM. In vivo reprogramming of Sox9+ cells in the liver to insulin-secreting ducts. PNAS 2012 109 1533615341. (doi:10.1073/pnas.1201701109).

    • Search Google Scholar
    • Export Citation
  • 64

    Dor Y, Brown J, Martinez OI, Melton DA. Adult pancreatic β-cells are formed by self-duplication rather than stem-cell differentiation. Nature 2004 429 4146. (doi:10.1038/nature02520).

    • Search Google Scholar
    • Export Citation
  • 65

    Nir T, Melton DA, Dor Y. Recovery from diabetes in mice by β cell regeneration. Journal of Clinical Investigation 2007 117 25532561. (doi:10.1172/JCI32959).

    • Search Google Scholar
    • Export Citation
  • 66

    Teta M, Rankin MM, Long SY, Stein GM, Kushner JA. Growth and regeneration of adult β cells does not involve specialized progenitors. Developmental Cell 2007 12 817826. (doi:10.1016/j.devcel.2007.04.011).

    • Search Google Scholar
    • Export Citation
  • 67

    Talchai C, Xuan S, Lin HV, Sussel L, Accili D. Pancreatic β cell dedifferentiation as a mechanism of diabetic β cell failure. Cell 2012 150 12231234. (doi:10.1016/j.cell.2012.07.029).

    • Search Google Scholar
    • Export Citation
  • 68

    Xu X, D'Hoker J, Stange G, Bonne S, De Leu N, Xiao X, Van de Casteele M, Mellitzer G, Ling Z, Pipeleers D et al.. Beta cells can be generated from endogenous progenitors in injured adult mouse pancreas. Cell 2008 132 197207. (doi:10.1016/j.cell.2007.12.015).

    • Search Google Scholar
    • Export Citation
  • 69

    Collombat P, Xu X, Ravassard P, Sosa-Pineda B, Dussaud S, Billestrup N, Madsen OD, Serup P, Heimberg H, Mansouri A. The ectopic expression of Pax4 in the mouse pancreas converts progenitor cells into α and subsequently β cells. Cell 2009 138 449462. (doi:10.1016/j.cell.2009.05.035).

    • Search Google Scholar
    • Export Citation
  • 70

    Thorel F, Nepote V, Avril I, Kohno K, Desgraz R, Chera S, Herrera PL. Conversion of adult pancreatic α-cells to β-cells after extreme β-cell loss. Nature 2010 464 11491154. (doi:10.1038/nature08894).

    • Search Google Scholar
    • Export Citation
  • 71

    Yi P, Park JS, Melton DA. Betatrophin: a hormone that controls pancreatic β cell proliferation. Cell 2013 153 747758. (doi:10.1016/j.cell.2013.04.008).

    • Search Google Scholar
    • Export Citation
  • 72

    Jiao Y, Le Lay J, Yu M, Naji A, Kaestner KH. Elevated mouse hepatic betatrophin expression does not increase human β-cell replication in the transplant setting. Diabetes 2014 63 12831288. (doi:10.2337/db13-1435).

    • Search Google Scholar
    • Export Citation
  • 73

    Gusarova V, Alexa CA, Na E, Stevis PE, Xin Y, Bonner-Weir S, Cohen JC, Hobbs HH, Murphy AJ, Yancopoulos GD et al.. ANGPTL8/betatrophin does not control pancreatic β cell expansion. Cell 2014 159 691696. (doi:10.1016/j.cell.2014.09.027).

    • Search Google Scholar
    • Export Citation
  • 74

    Alvarez-Perez JC, Ernst S, Demirci C, Casinelli GP, Mellado-Gil JM, Rausell-Palamos F, Vasavada RC, Garcia-Ocana A. Hepatocyte growth factor/c-Met signaling is required for ss-cell regeneration. Diabetes 2014 63 216223. (doi:10.2337/db13-0333).

    • Search Google Scholar
    • Export Citation
  • 75

    Contreras JL, Eckstein C, Smyth CA, Sellers MT, Vilatoba M, Bilbao G, Rahemtulla FG, Young CJ, Thompson JA, Chaudry IH et al.. Brain death significantly reduces isolated pancreatic islet yields and functionality in vitro and in vivo after transplantation in rats. Diabetes 2003 52 29352942. (doi:10.2337/diabetes.52.12.2935).

    • Search Google Scholar
    • Export Citation
  • 76

    Al-Adra DP, Gill RS, Imes S, O'Gorman D, Kin T, Axford SJ, Shi X, Senior PA, Shapiro AM. Single-donor islet transplantation and long-term insulin independence in select patients with type 1 diabetes mellitus. Transplantation 2014 98 10071012. (doi:10.1097/TP.0000000000000217).

    • Search Google Scholar
    • Export Citation
  • 77

    Matsumoto S, Noguchi H, Naziruddin B, Onaca N, Jackson A, Nobuyo H, Teru O, Naoya K, Klintmalm G, Levy M. Improvement of pancreatic islet cell isolation for transplantation. Proceedings (Baylor University. Medical Center) 2007 20 357362.

    • Search Google Scholar
    • Export Citation
  • 78

    Andres A, Kin T, O'Gorman D, Bigam D, Kneteman N, Senior P, Shapiro AJ. Impact of adverse pancreatic injury at surgical procurement upon islet isolation outcome. Transplant International 2014 27 11351142. (doi:10.1111/tri.12392).

    • Search Google Scholar
    • Export Citation
  • 79

    Ahearn AJ, Parekh JR, Posselt AM. Islet transplantation for type 1 diabetes: where are we now? Expert Review of Clinical Immunology 2015 11 5968. (doi:10.1586/1744666X.2015.978291).

    • Search Google Scholar
    • Export Citation
  • 80

    Szot GL, Lee MR, Tavakol MM, Lang J, Dekovic F, Kerlan RK, Stock PG, Posselt AM. Successful clinical islet isolation using a GMP-manufactured collagenase and neutral protease. Transplantation 2009 88 753756. (doi:10.1097/TP.0b013e3181b443ae).

    • Search Google Scholar
    • Export Citation
  • 81

    Lakey JR, Aspinwall CA, Cavanagh TJ, Kennedy RT. Secretion from islets and single islet cells following cryopreservation. Cell Transplantation 1999 8 691698.

    • Search Google Scholar
    • Export Citation
  • 82

    Lakey JR, Warnock GL, Shapiro AM, Korbutt GS, Ao Z, Kneteman NM, Rajotte RV. Intraductal collagenase delivery into the human pancreas using syringe loading or controlled perfusion. Cell Transplantation 1999 8 285292. (doi:10.1016/S0041-1345(97)01306-7).

    • Search Google Scholar
    • Export Citation
  • 83

    Barbaro B, Salehi P, Wang Y, Qi M, Gangemi A, Kuechle J, Hansen MA, Romagnoli T, Avila J, Benedetti E et al.. Improved human pancreatic islet purification with the refined UIC-UB density gradient. Transplantation 2007 84 12001203. (doi:10.1097/01.tp.0000287127.00377.6f).

    • Search Google Scholar
    • Export Citation
  • 84

    Loganathan G, Dawra RK, Pugazhenthi S, Guo Z, Soltani SM, Wiseman A, Sanders MA, Papas KK, Velayutham K, Saluja AK et al.. Insulin degradation by acinar cell proteases creates a dysfunctional environment for human islets before/after transplantation: benefits of α-1 antitrypsin treatment. Transplantation 2011 92 12221230. (doi:10.1097/TP.0b013e318237585c).

    • Search Google Scholar
    • Export Citation
  • 85

    Rose NL, Palcic MM, Shapiro AM, Lakey JR. An evaluation of the activation of endogenous pancreatic enzymes during human islet isolations. Transplantation Proceedings 2003 35 24552457. (doi:10.1016/j.transproceed.2003.08.025).

    • Search Google Scholar
    • Export Citation
  • 86

    Mwangi SM, Usta Y, Shahnavaz N, Joseph I, Avila J, Cano J, Chetty VK, Larsen CP, Sitaraman SV, Srinivasan S. Glial cell line-derived neurotrophic factor enhances human islet posttransplantation survival. Transplantation 2011 92 745751. (doi:10.1097/TP.0b013e31822bc95a).

    • Search Google Scholar
    • Export Citation
  • 87

    Cabric S, Sanchez J, Lundgren T, Foss A, Felldin M, Kallen R, Salmela K, Tibell A, Tufveson G, Larsson R et al.. Islet surface heparinization prevents the instant blood-mediated inflammatory reaction in islet transplantation. Diabetes 2007 56 20082015. (doi:10.2337/db07-0358).

    • Search Google Scholar
    • Export Citation
  • 88

    Farney AC, Xenos E, Sutherland DE, Widmer M, Stephanian E, Field MJ, Kaufman DB, Stevens RB, Blazar B, Platt J et al.. Inhibition of pancreatic islet β cell function by tumor necrosis factor is blocked by a soluble tumor necrosis factor receptor. Transplantation Proceedings 1993 25 865866.

    • Search Google Scholar
    • Export Citation
  • 89

    Yamamoto T, Mita A, Ricordi C, Messinger S, Miki A, Sakuma Y, Timoneri F, Barker S, Fornoni A, Molano RD et al.. Prolactin supplementation to culture medium improves β-cell survival. Transplantation 2010 89 13281335. (doi:10.1097/TP.0b013e3181d98af1).

    • Search Google Scholar
    • Export Citation
  • 90

    Shapiro AM. State of the art of clinical islet transplantation and novel protocols of immunosuppression. Current Diabetes Reports 2011 11 345354. (doi:10.1007/s11892-011-0217-8).

    • Search Google Scholar
    • Export Citation
  • 91

    Emamaullee JA, Shapiro AM. Interventional strategies to prevent β-cell apoptosis in islet transplantation. Diabetes 2006 55 19071914. (doi:10.2337/db05-1254).

    • Search Google Scholar
    • Export Citation
  • 92

    Barshes NR, Wyllie S, Goss JA. Inflammation-mediated dysfunction and apoptosis in pancreatic islet transplantation: implications for intrahepatic grafts. Journal of Leukocyte Biology 2005 77 587597. (doi:10.1189/jlb.1104649).

    • Search Google Scholar
    • Export Citation
  • 93

    Giannoukakis N, Rudert WA, Ghivizzani SC, Gambotto A, Ricordi C, Trucco M, Robbins PD. Adenoviral gene transfer of the interleukin-1 receptor antagonist protein to human islets prevents IL-1β-induced β-cell impairment and activation of islet cell apoptosis in vitro. Diabetes 1999 48 17301736. (doi:10.2337/diabetes.48.9.1730).

    • Search Google Scholar
    • Export Citation
  • 94

    Rink JS, Chen X, Zhang X, Kaufman DB. Conditional and specific inhibition of NF-κB in mouse pancreatic β cells prevents cytokine-induced deleterious effects and improves islet survival posttransplant. Surgery 2012 151 330339. (doi:10.1016/j.surg.2011.07.011).

    • Search Google Scholar
    • Export Citation
  • 95

    Gao Q, Ma LL, Gao X, Yan W, Williams P, Yin DP. TLR4 mediates early graft failure after intraportal islet transplantation. American Journal of Transplantation 2010 10 15881596. (doi:10.1111/j.1600-6143.2010.03151.x).

    • Search Google Scholar
    • Export Citation
  • 96

    Bertera S, Crawford ML, Alexander AM, Papworth GD, Watkins SC, Robbins PD, Trucco M. Gene transfer of manganese superoxide dismutase extends islet graft function in a mouse model of autoimmune diabetes. Diabetes 2003 52 387393. (doi:10.2337/diabetes.52.2.387).

    • Search Google Scholar
    • Export Citation
  • 97

    Li X, Chen H, Epstein PN. Metallothionein protects islets from hypoxia and extends islet graft survival by scavenging most kinds of reactive oxygen species. Journal of Biological Chemistry 2004 279 765771. (doi:10.1074/jbc.M307907200).

    • Search Google Scholar
    • Export Citation
  • 98

    Sklavos MM, Bertera S, Tse HM, Bottino R, He J, Beilke JN, Coulombe MG, Gill RG, Crapo JD, Trucco M et al.. Redox modulation protects islets from transplant-related injury. Diabetes 2010 59 17311738. (doi:10.2337/db09-0588).

    • Search Google Scholar
    • Export Citation
  • 99

    Brandhorst D, Brandhorst H, Zwolinski A, Nahidi F, Bretzel RG. Prevention of early islet graft failure by selective inducible nitric oxide synthase inhibitors after pig to nude rat intraportal islet transplantation. Transplantation 2001 71 179184. (doi:10.1097/00007890-200101270-00002).

    • Search Google Scholar
    • Export Citation
  • 100

    Gibly RF, Graham JG, Luo X, Lowe WL Jr, Hering BJ, Shea LD. Advancing islet transplantation: from engraftment to the immune response. Diabetologia 2011 54 24942505. (doi:10.1007/s00125-011-2243-0).

    • Search Google Scholar
    • Export Citation
  • 101

    Pinkse GG, Bouwman WP, Jiawan-Lalai R, Terpstra OT, Bruijn JA, de Heer E. Integrin signaling via RGD peptides and anti-β1 antibodies confers resistance to apoptosis in islets of Langerhans. Diabetes 2006 55 312317. (doi:10.2337/diabetes.55.02.06.db04-0195).

    • Search Google Scholar
    • Export Citation
  • 102

    Jalili RB, Moeen Rezakhanlou A, Hosseini-Tabatabaei A, Ao Z, Warnock GL, Ghahary A. Fibroblast populated collagen matrix promotes islet survival and reduces the number of islets required for diabetes reversal. Journal of Cellular Physiology 2011 226 18131819. (doi:10.1002/jcp.22515).

    • Search Google Scholar
    • Export Citation
  • 103

    Nilsson B, Ekdahl KN, Korsgren O. Control of instant blood-mediated inflammatory reaction to improve islets of Langerhans engraftment. Current Opinion in Organ Transplantation 2011 16 620626. (doi:10.1097/MOT.0b013e32834c2393).

    • Search Google Scholar
    • Export Citation
  • 104

    Takahashi H, Goto M, Ogawa N, Saito Y, Fujimori K, Kurokawa Y, Doi H, Satomi S. Superiority of fresh islets compared with cultured islets. Transplantation Proceedings 2009 41 350351. (doi:10.1016/j.transproceed.2008.08.143).

    • Search Google Scholar
    • Export Citation
  • 105

    Moberg L, Olsson A, Berne C, Felldin M, Foss A, Kallen R, Salmela K, Tibell A, Tufveson G, Nilsson B et al.. Nicotinamide inhibits tissue factor expression in isolated human pancreatic islets: implications for clinical islet transplantation. Transplantation 2003 76 12851288. (doi:10.1097/01.TP.0000098905.86445.0F).

    • Search Google Scholar
    • Export Citation
  • 106

    Berman DM, Cabrera O, Kenyon NM, Miller J, Tam SH, Khandekar VS, Picha KM, Soderman AR, Jordan RE, Bugelski PJ et al.. Interference with tissue factor prolongs intrahepatic islet allograft survival in a nonhuman primate marginal mass model. Transplantation 2007 84 308315. (doi:10.1097/01.tp.0000275401.80187.1e).

    • Search Google Scholar
    • Export Citation
  • 107

    Ozmen L, Ekdahl KN, Elgue G, Larsson R, Korsgren O, Nilsson B. Inhibition of thrombin abrogates the instant blood-mediated inflammatory reaction triggered by isolated human islets: possible application of the thrombin inhibitor melagatran in clinical islet transplantation. Diabetes 2002 51 17791784. (doi:10.2337/diabetes.51.6.1779).

    • Search Google Scholar
    • Export Citation
  • 108

    Contreras JL, Eckstein C, Smyth CA, Bilbao G, Vilatoba M, Ringland SE, Young C, Thompson JA, Fernandez JA, Griffin JH et al.. Activated protein C preserves functional islet mass after intraportal transplantation: a novel link between endothelial cell activation, thrombosis, inflammation, and islet cell death. Diabetes 2004 53 28042814. (doi:10.2337/diabetes.53.11.2804).

    • Search Google Scholar
    • Export Citation
  • 109

    Akima S, Hawthorne WJ, Favaloro E, Patel A, Blyth K, Mudaliar Y, Chapman JR, O'Connell PJ. Tirofiban and activated protein C synergistically inhibit the Instant Blood Mediated Inflammatory Reaction (IBMIR) from allogeneic islet cells exposure to human blood. American Journal of Transplantation 2009 9 15331540. (doi:10.1111/j.1600-6143.2009.02673.x).

    • Search Google Scholar
    • Export Citation
  • 110

    Cui W, Angsana J, Wen J, Chaikof EL. Liposomal formulations of thrombomodulin increase engraftment after intraportal islet transplantation. Cell Transplantation 2010 19 13591367. (doi:10.3727/096368910X513964).

    • Search Google Scholar
    • Export Citation
  • 111

    Cui W, Wilson JT, Wen J, Angsana J, Qu Z, Haller CA, Chaikof EL. Thrombomodulin improves early outcomes after intraportal islet transplantation. American Journal of Transplantation 2009 9 13081316. (doi:10.1111/j.1600-6143.2009.02652.x).

    • Search Google Scholar
    • Export Citation
  • 112

    Koh A, Senior P, Salam A, Kin T, Imes S, Dinyari P, Malcolm A, Toso C, Nilsson B, Korsgren O et al.. Insulin-heparin infusions peritransplant substantially improve single-donor clinical islet transplant success. Transplantation 2010 89 465471. (doi:10.1097/TP.0b013e3181c478fd).

    • Search Google Scholar
    • Export Citation
  • 113

    Goto M, Johansson H, Maeda A, Elgue G, Korsgren O, Nilsson B. Low-molecular weight dextran sulfate abrogates the instant blood-mediated inflammatory reaction induced by adult porcine islets both in vitro and in vivo. Transplantation Proceedings 2004 36 11861187. (doi:10.1016/j.transproceed.2004.04.028).

    • Search Google Scholar
    • Export Citation
  • 114

    Wilson JT, Haller CA, Qu Z, Cui W, Urlam MK, Chaikof EL. Biomolecular surface engineering of pancreatic islets with thrombomodulin. Acta Biomaterialia 2010 6 18951903. (doi:10.1016/j.actbio.2010.01.027).

    • Search Google Scholar
    • Export Citation
  • 115

    Luan NM, Teramura Y, Iwata H. Layer-by-layer co-immobilization of soluble complement receptor 1 and heparin on islets. Biomaterials 2011 32 64876492. (doi:10.1016/j.biomaterials.2011.05.048).

    • Search Google Scholar
    • Export Citation
  • 116

    Luan NM, Teramura Y, Iwata H. Immobilization of the soluble domain of human complement receptor 1 on agarose-encapsulated islets for the prevention of complement activation. Biomaterials 2010 31 88478853. (doi:10.1016/j.biomaterials.2010.08.004).

    • Search Google Scholar
    • Export Citation
  • 117

    Kim HI, Yu JE, Lee SY, Sul AY, Jang MS, Rashid MA, Park SG, Kim SJ, Park CG, Kim JH et al.. The effect of composite pig islet-human endothelial cell grafts on the instant blood-mediated inflammatory reaction. Cell Transplantation 2009 18 3137. (doi:10.3727/096368909788237113).

    • Search Google Scholar
    • Export Citation
  • 118

    Cantley J, Grey ST, Maxwell PH, Withers DJ. The hypoxia response pathway and β-cell function. Diabetes, Obesity & Metabolism 2010 12 (Suppl 2) 159167. (doi:10.1111/j.1463-1326.2010.01276.x).

    • Search Google Scholar
    • Export Citation
  • 119

    Zhang N, Richter A, Suriawinata J, Harbaran S, Altomonte J, Cong L, Zhang H, Song K, Meseck M, Bromberg J et al.. Elevated vascular endothelial growth factor production in islets improves islet graft vascularization. Diabetes 2004 53 963970. (doi:10.2337/diabetes.53.4.963).

    • Search Google Scholar
    • Export Citation
  • 120

    Finetti F, Basile A, Capasso D, Di Gaetano S, Di Stasi R, Pascale M, Turco CM, Ziche M, Morbidelli L, D'Andrea LD. Functional and pharmacological characterization of a VEGF mimetic peptide on reparative angiogenesis. Biochemical Pharmacology 2012 84 303311. (doi:10.1016/j.bcp.2012.04.011).

    • Search Google Scholar
    • Export Citation
  • 121

    Cabric S, Sanchez J, Johansson U, Larsson R, Nilsson B, Korsgren O, Magnusson PU. Anchoring of vascular endothelial growth factor to surface-immobilized heparin on pancreatic islets: implications for stimulating islet angiogenesis. Tissue Engineering. Part A 2010 16 961970. (doi:10.1089/ten.tea.2009.0429).

    • Search Google Scholar
    • Export Citation
  • 122

    Olsson R, Maxhuni A, Carlsson PO. Revascularization of transplanted pancreatic islets following culture with stimulators of angiogenesis. Transplantation 2006 82 340347. (doi:10.1097/01.tp.0000229418.60236.87).

    • Search Google Scholar
    • Export Citation
  • 123

    Luo L, Badiavas E, Luo JZ, Maizel A. Allogeneic bone marrow supports human islet β cell survival and function over six months. Biochemical and Biophysical Research Communications 2007 361 859864. (doi:10.1016/j.bbrc.2007.07.105).

    • Search Google Scholar
    • Export Citation
  • 124

    Song HJ, Xue WJ, Li Y, Tian XH, Ding XM, Feng XS, Song Y, Tian PX. Prolongation of islet graft survival using concomitant transplantation of islets and vascular endothelial cells in diabetic rats. Transplantation Proceedings 2010 42 26622665. (doi:10.1016/j.transproceed.2010.06.003).

    • Search Google Scholar
    • Export Citation
  • 125

    Cantaluppi V, Biancone L, Figliolini F, Beltramo S, Medica D, Deregibus MC, Galimi F, Romagnoli R, Salizzoni M, Tetta C et al.. Microvesicles derived from endothelial progenitor cells enhance neoangiogenesis of human pancreatic islets. Cell Transplantation 2012 21 13051320. (doi:10.3727/096368911X627534).

    • Search Google Scholar
    • Export Citation
  • 126

    Al-Khaldi A, Eliopoulos N, Martineau D, Lejeune L, Lachapelle K, Galipeau J. Postnatal bone marrow stromal cells elicit a potent VEGF-dependent neoangiogenic response in vivo. Gene Therapy 2003 10 621629. (doi:10.1038/sj.gt.3301934).

    • Search Google Scholar
    • Export Citation
  • 127

    Barsotti MC, Magera A, Armani C, Chiellini F, Felice F, Dinucci D, Piras AM, Minnocci A, Solaro R, Soldani G et al.. Fibrin acts as biomimetic niche inducing both differentiation and stem cell marker expression of early human endothelial progenitor cells. Cell Proliferation 2011 44 3348. (doi:10.1111/j.1365-2184.2010.00715.x).

    • Search Google Scholar
    • Export Citation
  • 128

    Sigrist S, Mechine-Neuville A, Mandes K, Calenda V, Legeay G, Bellocq JP, Pinget M, Kessler L. Induction of angiogenesis in omentum with vascular endothelial growth factor: influence on the viability of encapsulated rat pancreatic islets during transplantation. Journal of Vascular Research 2003 40 359367. (doi:10.1159/000072700).

    • Search Google Scholar
    • Export Citation
  • 129

    Davis GE, Senger DR. Endothelial extracellular matrix: biosynthesis, remodeling, and functions during vascular morphogenesis and neovessel stabilization. Circulation Research 2005 97 10931107. (doi:10.1161/01.RES.0000191547.64391.e3).

    • Search Google Scholar
    • Export Citation
  • 130

    Hiscox AM, Stone AL, Limesand S, Hoying JB, Williams SK. An islet-stabilizing implant constructed using a preformed vasculature. Tissue Engineering. Part A 2008 14 433440. (doi:10.1089/tea.2007.0099).

    • Search Google Scholar
    • Export Citation
  • 131

    Dionne KE, Colton CK, Yarmush ML. Effect of hypoxia on insulin secretion by isolated rat and canine islets of Langerhans. Diabetes 1993 42 1221. (doi:10.2337/diab.42.1.12).

    • Search Google Scholar
    • Export Citation
  • 132

    Sakata N, Chan NK, Ostrowski RP, Chrisler J, Hayes P, Kim S, Obenaus A, Zhang JH, Hathout E. Hyperbaric oxygen therapy improves early posttransplant islet function. Pediatric Diabetes 2010 11 471478. (doi:10.1111/j.1399-5448.2009.00629.x).

    • Search Google Scholar
    • Export Citation
  • 133

    Ludwig B, Rotem A, Schmid J, Weir GC, Colton CK, Brendel MD, Neufeld T, Block NL, Yavriyants K, Steffen A et al.. Improvement of islet function in a bioartificial pancreas by enhanced oxygen supply and growth hormone releasing hormone agonist. PNAS 2012 109 50225027. (doi:10.1073/pnas.1201868109).

    • Search Google Scholar
    • Export Citation
  • 134

    Nadithe V, Mishra D, Bae YH. Poly(ethylene glycol) cross-linked hemoglobin with antioxidant enzymes protects pancreatic islets from hypoxic and free radical stress and extends islet functionality. Biotechnology and Bioengineering 2012 109 23922401. (doi:10.1002/bit.24501).

    • Search Google Scholar
    • Export Citation
  • 135

    Pedraza E, Coronel MM, Fraker CA, Ricordi C, Stabler CL. Preventing hypoxia-induced cell death in β cells and islets via hydrolytically activated, oxygen-generating biomaterials. PNAS 2012 109 42454250. (doi:10.1073/pnas.1113560109).

    • Search Google Scholar
    • Export Citation
  • 136

    Miao G, Ostrowski RP, Mace J, Hough J, Hopper A, Peverini R, Chinnock R, Zhang J, Hathout E. Dynamic production of hypoxia-inducible factor-1α in early transplanted islets. American Journal of Transplantation 2006 6 26362643. (doi:10.1111/j.1600-6143.2006.01541.x).

    • Search Google Scholar
    • Export Citation
  • 137

    Papas KK, Avgoustiniatos ES, Tempelman LA, Weir GC, Colton CK, Pisania A, Rappel MJ, Friberg AS, Bauer AC, Hering BJ. High-density culture of human islets on top of silicone rubber membranes. Transplantation Proceedings 2005 37 34123414. (doi:10.1016/j.transproceed.2005.09.086).

    • Search Google Scholar
    • Export Citation
  • 138

    Simoni J, Villanueva-Meyer J, Simoni G, Moeller JF, Wesson DE. Control of oxidative reactions of hemoglobin in the design of blood substitutes: role of the ascorbate-glutathione antioxidant system. Artificial Organs 2009 33 115126. (doi:10.1111/j.1525-1594.2008.00695.x).

    • Search Google Scholar
    • Export Citation
  • 139

    Spiess BD. Perfluorocarbon emulsions as a promising technology: a review of tissue and vascular gas dynamics. Journal of Applied Physiology 2009 106 14441452. (doi:10.1152/japplphysiol.90995.2008).

    • Search Google Scholar
    • Export Citation
  • 140

    Maillard E, Juszczak MT, Langlois A, Kleiss C, Sencier MC, Bietiger W, Sanchez-Dominguez M, Krafft MP, Johnson PR, Pinget M et al.. Perfluorocarbon emulsions prevent hypoxia of pancreatic β-cells. Cell Transplantation 2012 21 657669. (doi:10.3727/096368911X593136).

    • Search Google Scholar
    • Export Citation
  • 141

    Riess JG. Fluorocarbon-based oxygen carriers: new orientations. Artificial Organs 1991 15 408413.

  • 142

    Maillard E, Juszczak MT, Clark A, Hughes SJ, Gray DR, Johnson PR. Perfluorodecalin-enriched fibrin matrix for human islet culture. Biomaterials 2011 32 92829289. (doi:10.1016/j.biomaterials.2011.08.044).

    • Search Google Scholar
    • Export Citation
  • 143

    Oluwole OO, Depaz HA, Gopinathan R, Ali A, Garrovillo M, Jin MX, Hardy MA, Oluwole SF. Indirect allorecognition in acquired thymic tolerance: induction of donor-specific permanent acceptance of rat islets by adoptive transfer of allopeptide-pulsed host myeloid and thymic dendritic cells. Diabetes 2001 50 15461552. (doi:10.2337/diabetes.50.7.1546).

    • Search Google Scholar
    • Export Citation
  • 144

    Britt LD, Scharp DW, Lacy PE, Slavin S. Transplantation of islet cells across major histocompatibility barriers after total lymphoid irradiation and infusion of allogeneic bone marrow cells. Diabetes 1982 31 (Suppl 4) 6368. (doi:10.2337/diab.31.4.S63).

    • Search Google Scholar
    • Export Citation
  • 145

    Li H, Kaufman CL, Boggs SS, Johnson PC, Patrene KD, Ildstad ST. Mixed allogeneic chimerism induced by a sublethal approach prevents autoimmune diabetes and reverses insulitis in nonobese diabetic (NOD) mice. Journal of Immunology 1996 156 380388.

    • Search Google Scholar
    • Export Citation
  • 146

    Nikolic B, Takeuchi Y, Leykin I, Fudaba Y, Smith RN, Sykes M. Mixed hematopoietic chimerism allows cure of autoimmune diabetes through allogeneic tolerance and reversal of autoimmunity. Diabetes 2004 53 376383. (doi:10.2337/diabetes.53.2.376).

    • Search Google Scholar
    • Export Citation
  • 147

    Morelli AE, Thomson AW. Tolerogenic dendritic cells and the quest for transplant tolerance. Nature Reviews. Immunology 2007 7 610621. (doi:10.1038/nri2132).

    • Search Google Scholar
    • Export Citation
  • 148

    Giannoukakis N, Phillips B, Finegold D, Harnaha J, Trucco M. Phase I (safety) study of autologous tolerogenic dendritic cells in type 1 diabetic patients. Diabetes Care 2011 34 20262032. (doi:10.2337/dc11-0472).

    • Search Google Scholar
    • Export Citation
  • 149

    Liang X, Lu L, Chen Z, Vickers T, Zhang H, Fung JJ, Qian S. Administration of dendritic cells transduced with antisense oligodeoxyribonucleotides targeting CD80 or CD86 prolongs allograft survival. Transplantation 2003 76 721729. (doi:10.1097/01.TP.0000076470.35404.49).

    • Search Google Scholar
    • Export Citation
  • 150

    Takayama T, Nishioka Y, Lu L, Lotze MT, Tahara H, Thomson AW. Retroviral delivery of viral interleukin-10 into myeloid dendritic cells markedly inhibits their allostimulatory activity and promotes the induction of T-cell hyporesponsiveness. Transplantation 1998 66 15671574. (doi:10.1097/00007890-199812270-00001).

    • Search Google Scholar
    • Export Citation
  • 151

    Lee WC, Zhong C, Qian S, Wan Y, Gauldie J, Mi Z, Robbins PD, Thomson AW, Lu L. Phenotype, function, and in vivo migration and survival of allogeneic dendritic cell progenitors genetically engineered to express TGF-β. Transplantation 1998 66 18101817. (doi:10.1097/00007890-199812270-00040).

    • Search Google Scholar
    • Export Citation
  • 152

    Ferreira GB, van Etten E, Verstuyf A, Waer M, Overbergh L, Gysemans C, Mathieu C. 25-dihydroxyvitamin D3 alters murine dendritic cell behaviour in vitro and in vivo. Diabetes/Metabolism Research and Reviews 2011 27 933941. (doi:10.1002/dmrr.1275).

    • Search Google Scholar
    • Export Citation
  • 153

    da Costa TB, Sardinha LR, Larocca R, Peron JP, Rizzo LV. Allogeneic apoptotic thymocyte-stimulated dendritic cells expand functional regulatory T cells. Immunology 2011 133 123132. (doi:10.1111/j.1365-2567.2011.03420.x).

    • Search Google Scholar
    • Export Citation
  • 154

    Morelli AE, Larregina AT, Shufesky WJ, Zahorchak AF, Logar AJ, Papworth GD, Wang Z, Watkins SC, Falo LD Jr, Thomson AW. Internalization of circulating apoptotic cells by splenic marginal zone dendritic cells: dependence on complement receptors and effect on cytokine production. Blood 2003 101 611620. (doi:10.1182/blood-2002-06-1769).

    • Search Google Scholar
    • Export Citation
  • 155

    Thery C, Zitvogel L, Amigorena S. Exosomes: composition, biogenesis and function. Nature Reviews. Immunology 2002 2 569579. (doi:10.1038/nri855).

    • Search Google Scholar
    • Export Citation
  • 156

    Roncarolo MG, Gregori S, Battaglia M, Bacchetta R, Fleischhauer K, Levings MK. Interleukin-10-secreting type 1 regulatory T cells in rodents and humans. Immunological Reviews 2006 212 2850. (doi:10.1111/j.0105-2896.2006.00420.x).

    • Search Google Scholar
    • Export Citation
  • 157

    Gagliani N, Jofra T, Stabilini A, Valle A, Atkinson M, Roncarolo MG, Battaglia M. Antigen-specific dependence of Tr1-cell therapy in preclinical models of islet transplant. Diabetes 2010 59 433439. (doi:10.2337/db09-1168).

    • Search Google Scholar
    • Export Citation
  • 158

    Masteller EL, Warner MR, Tang Q, Tarbell KV, McDevitt H, Bluestone JA. Expansion of functional endogenous antigen-specific CD4+CD25+ regulatory T cells from nonobese diabetic mice. Journal of Immunology 2005 175 30533059. (doi:10.4049/jimmunol.175.5.3053).

    • Search Google Scholar
    • Export Citation
  • 159

    Yang H, Cheng EY, Sharma VK, Lagman M, Chang C, Song P, Ding R, Muthukumar T, Suthanthiran M. Dendritic cells with TGF-β1 and IL-2 differentiate naive CD4+ T cells into alloantigen-specific and allograft protective Foxp3+ regulatory T cells. Transplantation 2012 93 580588.

    • Search Google Scholar
    • Export Citation
  • 160

    Pothoven KL, Kheradmand T, Yang Q, Houlihan JL, Zhang H, Degutes M, Miller SD, Luo X. Rapamycin-conditioned donor dendritic cells differentiate CD4CD25Foxp3 T cells in vitro with TGF-β1 for islet transplantation. American Journal of Transplantation 2010 10 17741784. (doi:10.1111/j.1600-6143.2010.03199.x).

    • Search Google Scholar
    • Export Citation
  • 161

    Battaglia M, Stabilini A, Draghici E, Gregori S, Mocchetti C, Bonifacio E, Roncarolo MG. Rapamycin and interleukin-10 treatment induces T regulatory type 1 cells that mediate antigen-specific transplantation tolerance. Diabetes 2006 55 4049. (doi:10.2337/diabetes.55.01.06.db05-0613).

    • Search Google Scholar
    • Export Citation
  • 162

    Marek N, Krzystyniak A, Ergenc I, Cochet O, Misawa R, Wang LJ, Golab K, Wang X, Kilimnik G, Hara M et al.. Coating human pancreatic islets with CD4(+)CD25(high)CD127(−) regulatory T cells as a novel approach for the local immunoprotection. Annals of Surgery 2011 254 512518.discussion 518–519 (doi:10.1097/SLA.0b013e31822c9ca7).

    • Search Google Scholar
    • Export Citation
  • 163

    Montane J, Bischoff L, Soukhatcheva G, Dai DL, Hardenberg G, Levings MK, Orban PC, Kieffer TJ, Tan R, Verchere CB. Prevention of murine autoimmune diabetes by CCL22-mediated Treg recruitment to the pancreatic islets. Journal of Clinical Investigation 2011 121 30243028. (doi:10.1172/JCI43048).

    • Search Google Scholar
    • Export Citation
  • 164

    Lee KM, Stott RT, Zhao G, SooHoo J, Xiong W, Lian MM, Fitzgerald L, Shi S, Akrawi E, Lei J et al.. TGF-β-producing regulatory B cells induce regulatory T cells and promote transplantation tolerance. European Journal of Immunology 2014 44 17281736. (doi:10.1002/eji.201344062).

    • Search Google Scholar
    • Export Citation
  • 165

    Lee K, Nguyen V, Lee KM, Kang SM, Tang Q. Attenuation of donor-reactive T cells allows effective control of allograft rejection using regulatory T cell therapy. American Journal of Transplantation 2014 14 2738. (doi:10.1111/ajt.12509).

    • Search Google Scholar
    • Export Citation
  • 166

    Li FR, Wang XG, Deng CY, Qi H, Ren LL, Zhou HX. Immune modulation of co-transplantation mesenchymal stem cells with islet on T and dendritic cells. Clinical and Experimental Immunology 2010 161 357363. (doi:10.1111/j.1365-2249.2010.04178.x).

    • Search Google Scholar
    • Export Citation
  • 167

    Solari MG, Srinivasan S, Boumaza I, Unadkat J, Harb G, Garcia-Ocana A, Feili-Hariri M. Marginal mass islet transplantation with autologous mesenchymal stem cells promotes long-term islet allograft survival and sustained normoglycemia. Journal of Autoimmunity 2009 32 116124. (doi:10.1016/j.jaut.2009.01.003).

    • Search Google Scholar
    • Export Citation
  • 168

    Berman DM, Willman MA, Han D, Kleiner G, Kenyon NM, Cabrera O, Karl JA, Wiseman RW, O'Connor DH, Bartholomew AM et al.. Mesenchymal stem cells enhance allogeneic islet engraftment in nonhuman primates. Diabetes 2010 59 25582568. (doi:10.2337/db10-0136).

    • Search Google Scholar
    • Export Citation
  • 169

    Ding Y, Xu D, Feng G, Bushell A, Muschel RJ, Wood KJ. Mesenchymal stem cells prevent the rejection of fully allogenic islet grafts by the immunosuppressive activity of matrix metalloproteinase-2 and -9. Diabetes 2009 58 17971806. (doi:10.2337/db09-0317).

    • Search Google Scholar
    • Export Citation
  • 170

    Longoni B, Szilagyi E, Quaranta P, Paoli GT, Tripodi S, Urbani S, Mazzanti B, Rossi B, Fanci R, Demontis GC et al.. Mesenchymal stem cells prevent acute rejection and prolong graft function in pancreatic islet transplantation. Diabetes Technology & Therapeutics 2010 12 435446. (doi:10.1089/dia.2009.0154).

    • Search Google Scholar
    • Export Citation
  • 171

    Posselt AM, Szot GL, Frassetto LA, Masharani U, Tavakol M, Amin R, McElroy J, Ramos MD, Kerlan RK, Fong L et al.. Islet transplantation in type 1 diabetic patients using calcineurin inhibitor-free immunosuppressive protocols based on T-cell adhesion or costimulation blockade. Transplantation 2010 90 15951601. (doi:10.1097/TP.0b013e3181fe1377).

    • Search Google Scholar
    • Export Citation
  • 172

    Vergani A, D'Addio F, Jurewicz M, Petrelli A, Watanabe T, Liu K, Law K, Schuetz C, Carvello M, Orsenigo E et al.. A novel clinically relevant strategy to abrogate autoimmunity and regulate alloimmunity in NOD mice. Diabetes 2010 59 22532264. (doi:10.2337/db09-1264).

    • Search Google Scholar
    • Export Citation
  • 173

    Wang X, Hao J, Metzger DL, Mui A, Lee IF, Akhoundsadegh N, Ao Z, Chen L, Ou D, Verchere CB et al.. Endogenous expression of B7-H4 improves long-term murine islet allograft survival. Transplantation 2013 95 9499. (doi:10.1097/TP.0b013e318277229d).

    • Search Google Scholar
    • Export Citation
  • 174

    Wang X, Hao J, Metzger DL, Mui A, Ao Z, Verchere CB, Chen L, Ou D, Warnock GL. Local expression of B7-H4 by recombinant adenovirus transduction in mouse islets prolongs allograft survival. Transplantation 2009 87 482490. (doi:10.1097/TP.0b013e318195e5fa).

    • Search Google Scholar
    • Export Citation
  • 175

    Nanji SA, Hancock WW, Anderson CC, Adams AB, Luo B, Schur CD, Pawlick RL, Wang L, Coyle AJ, Larsen CP et al.. Multiple combination therapies involving blockade of ICOS/B7RP-1 costimulation facilitate long-term islet allograft survival. American Journal of Transplantation 2004 4 526536. (doi:10.1111/j.1600-6143.2004.00384.x).

    • Search Google Scholar
    • Export Citation
  • 176

    Abdi R, Means TK, Luster AD. Chemokines in islet allograft rejection. Diabetes/Metabolism Research and Reviews 2003 19 186190. (doi:10.1002/dmrr.362).

    • Search Google Scholar
    • Export Citation
  • 177

    Citro A, Cantarelli E, Maffi P, Nano R, Melzi R, Mercalli A, Dugnani E, Sordi V, Magistretti P, Daffonchio L et al.. CXCR1/2 inhibition enhances pancreatic islet survival after transplantation. Journal of Clinical Investigation 2012 122 36473651. (doi:10.1172/JCI63089).

    • Search Google Scholar
    • Export Citation
  • 178

    de Vos P, Marchetti P. Encapsulation of pancreatic islets for transplantation in diabetes: the untouchable islets. Trends in Molecular Medicine 2002 8 363366. (doi:10.1016/S1471-4914(02)02381-X).

    • Search Google Scholar
    • Export Citation
  • 179

    O'Sullivan ES, Vegas A, Anderson DG, Weir GC. Islets transplanted in immunoisolation devices: a review of the progress and the challenges that remain. Endocrine Reviews 2011 32 827844. (doi:10.1210/er.2010-0026).

    • Search Google Scholar
    • Export Citation
  • 180

    Teramura Y, Iwata H. Bioartificial pancreas microencapsulation and conformal coating of islet of Langerhans. Advanced Drug Delivery Reviews 2010 62 827840. (doi:10.1016/j.addr.2010.01.005).

    • Search Google Scholar
    • Export Citation
  • 181

    Lacy PE, Hegre OD, Gerasimidi-Vazeou A, Gentile FT, Dionne KE. Maintenance of normoglycemia in diabetic mice by subcutaneous xenografts of encapsulated islets. Science 1991 254 17821784. (doi:10.1126/science.1763328).