Autoimmunity after islet-cell allotransplantation

Biological functions and affected signaling pathways by Long Non-Coding RNAs in the immune system

Recently, the various regulative functions of long non-coding RNAs (LncRNAs) have been well determined. Recently, the vital role of LncRNAs as gene regulators has been identified in the immune system, especially in the inflammatory response. All cells of the immune system are governed by a complex and ever-changing gene expression program that is regulated through both transcriptional and post-transcriptional processes. LncRNAs regulate gene expression within the cell nucleus by influencing transcription or through post-transcriptional processes that affect the splicing, stability, or translation of messenger RNAs (mRNAs). Recent studies in immunology have revealed substantial alterations in the expression of lncRNAs during the activation of the innate immune system as well as the development, differentiation, and activation of T cells. These lncRNAs regulate key aspects of immune function, including the manufacturing of inflammatory molecules, cellular distinction, and cell movement. They do this by modulating protein-protein interactions or through base pairing with RNA and DNA. Here we review the current understanding of the mechanism of action of lncRNAs as novel immune-related regulators and their impact on physiological and pathological processes related to the immune system, including autoimmune diseases. We also highlight the emerging pattern of gene expression control in important research areas at the intersection between immunology and lncRNA biology.

Transplantation of chemically induced pluripotent stem-cell-derived islets under abdominal anterior rectus sheath in a type 1 diabetes patient

We report the 1-year results from one patient as the preliminary analysis of a first-in-human phase I clinical trial (ChiCTR2300072200) assessing the feasibility of autologous transplantation of chemically induced pluripotent stem-cell-derived islets (CiPSC islets) beneath the abdominal anterior rectus sheath for type 1 diabetes treatment. The patient achieved sustained insulin independence starting 75 days post-transplantation. The patient's time-in-target glycemic range increased from a baseline value of 43.18% to 96.21% by month 4 post-transplantation, accompanied by a decrease in glycated hemoglobin, an indicator of long-term systemic glucose levels at a non-diabetic level. Thereafter, the patient presented a state of stable glycemic control, with time-in-target glycemic range at >98% and glycated hemoglobin at around 5%. At 1 year, the clinical data met all study endpoints with no indication of transplant-related abnormalities. Promising results from this patient suggest that further clinical studies assessing CiPSC-islet transplantation in type 1 diabetes are warranted.

Allo Beta Cell transplantation: specific features, unanswered questions, and immunological challenge

Type 1 diabetes (T1D) presents a persistent medical challenge, demanding innovative strategies for sustained glycemic control and enhanced patient well-being. Beta cells are specialized cells in the pancreas that produce insulin, a hormone that regulates blood sugar levels. When beta cells are damaged or destroyed, insulin production decreases, which leads to T1D. Allo Beta Cell Transplantation has emerged as a promising therapeutic avenue, with the goal of reinstating glucose regulation and insulin production in T1D patients. However, the path to success in this approach is fraught with complex immunological hurdles that demand rigorous exploration and resolution for enduring therapeutic efficacy. This exploration focuses on the distinct immunological characteristics inherent to Allo Beta Cell Transplantation. An understanding of these unique challenges is pivotal for the development of effective therapeutic interventions. The critical role of glucose regulation and insulin in immune activation is emphasized, with an emphasis on the intricate interplay between beta cells and immune cells. The transplantation site, particularly the liver, is examined in depth, highlighting its relevance in the context of complex immunological issues. Scrutiny extends to recipient and donor matching, including the utilization of multiple islet donors, while also considering the potential risk of autoimmune recurrence. Moreover, unanswered questions and persistent gaps in knowledge within the field are identified. These include the absence of robust evidence supporting immunosuppression treatments, the need for reliable methods to assess rejection and treatment protocols, the lack of validated biomarkers for monitoring beta cell loss, and the imperative need for improved beta cell imaging techniques. In addition, attention is drawn to emerging directions and transformative strategies in the field. This encompasses alternative immunosuppressive regimens and calcineurin-free immunoprotocols, as well as a reevaluation of induction therapy and recipient preconditioning methods. Innovative approaches targeting autoimmune recurrence, such as CAR Tregs and TCR Tregs, are explored, along with the potential of stem stealth cells, tissue engineering, and encapsulation to overcome the risk of graft rejection. In summary, this review provides a comprehensive overview of the inherent immunological obstacles associated with Allo Beta Cell Transplantation. It offers valuable insights into emerging strategies and directions that hold great promise for advancing the field and ultimately improving outcomes for individuals living with diabetes.

Matching for HLA-DR excluding diabetogenic HLA-DR3 and HLA-DR4 predicts insulin independence after pancreatic islet transplantation

Introduction

In pancreatic islet transplantation, the exact contribution of human leukocyte antigen (HLA) matching to graft survival remains unclear. Islets may be exposed to allogenic rejection but also the recurrence of type 1 diabetes (T1D). We evaluated the HLA-DR matching, including the impact of diabetogenic HLA-DR3 or HLA-DR4 matches.

Methods

We retrospectively examined the HLA profile in 965 transplant recipients and 2327 islet donors. The study population was obtained from patients enrolled in the Collaborative Islet Transplant Registry. We then identified 87 recipients who received a single-islet infusion. Islet-kidney recipients, 2nd islet infusion, and patients with missing data were excluded from the analysis (n=878).

Results

HLA-DR3 and HLA-DR4 were present in 29.7% and 32.6% of T1D recipients and 11.6% and 15.8% of the donors, respectively. We identified 52 T1D islet recipients mismatched for HLA-DR (group A), 11 with 1 or 2 HLA-DR-matches but excluding HLA-DR3 and HLA- DR4 (group B), and 24 matched for HLA-DR3 or HLA-DR4 (group C). Insulin-independence was maintained in a significantly higher percentage of group B recipients from year one through five post-transplantation (p<0.01). At five-year post-transplantation, 78% of group B was insulin-independent compared to 24% (group A) and 35% (group C). Insulin-independence correlated with significantly better glycemic control (HbA1c <7%), fasting blood glucose, and reduced severe hypoglycemic events. Matching HLA-A-B-DR (≥3) independently of HLA- DR3 or HLA-DR4 matching did not improve graft survival.

Conclusion

This study suggests that matching HLA-DR but excluding the diabetogenic HLA-DR3 and/or 4 is a significant predictor for long-term islet survival.

Immunosuppressive PLGA TGF-β1 Microparticles Induce Polyclonal and Antigen-Specific Regulatory T Cells for Local Immunomodulation of Allogeneic Islet Transplants

Allogeneic islet transplantation is a promising cell-based therapy for Type 1 Diabetes (T1D). The long-term efficacy of this approach, however, is impaired by allorejection. Current clinical practice relies on long-term systemic immunosuppression, leading to severe adverse events. To avoid these detrimental effects, poly(lactic-co-glycolic acid) (PLGA) microparticles (MPs) were engineered for the localized and controlled release of immunomodulatory TGF-β1. The in vitro co-incubation of TGF-β1 releasing PLGA MPs with naïve CD4⁺ T cells resulted in the efficient generation of both polyclonal and antigen-specific induced regulatory T cells (iTregs) with robust immunosuppressive function. The co-transplantation of TGF-β1 releasing PLGA MPs and Balb/c mouse islets within the extrahepatic epididymal fat pad (EFP) of diabetic C57BL/6J mice resulted in the prompt engraftment of the allogenic implants, supporting the compatibility of PLGA MPs and local TGF-β1 release. The presence of the TGF-β1-PLGA MPs, however, did not confer significant graft protection when compared to untreated controls, despite measurement of preserved insulin expression, reduced intra-islet CD3⁺ cells invasion, and elevated CD3⁺Foxp3⁺ T cells at the peri-transplantation site in long-term functioning grafts. Examination of the broader impacts of TGF-β1/PLGA MPs on the host immune system implicated a localized nature of the immunomodulation with no observed systemic impacts. In summary, this approach establishes the feasibility of a local and modular microparticle delivery system for the immunomodulation of an extrahepatic implant site. This approach can be easily adapted to deliver larger doses or other agents, as well as multi-drug approaches, within the local graft microenvironment to prevent transplant rejection.

Immunological Monitoring in Beta Cell Replacement: Towards a Pathophysiology-Guided Implementation of Biomarkers

PURPOSE OF REVIEW

Grafted beta cells are lost because of recurrence of T1D and/or allograft rejection, two conditions diagnosed with pancreas graft biopsy, which is invasive and impossible in case of islet transplantation. This review synthetizes the current pathophysiological knowledge and discusses the interest of available immune biomarkers.

RECENT FINDINGS

Despite the central role of auto-(recurrence of T1D) and allo-(T-cell mediated rejection) immune cellular responses, the latter are not directly monitored in routine. In striking contrast, there have been undisputable progresses in monitoring of auto and alloantibodies. Except for pancreas recipients in whom anti-donor HLA antibodies can be directly responsible for antibody-mediated rejection, autoantibodies (and alloantibodies in islet recipients) have no direct pathogenic effect. However, their fluctuation offers a surrogate marker for the activation status of T cells (because antibody generation depends on T cells). This illustrates the necessity to understand the pathophysiology when interpreting a biomarker and selecting the appropriate treatment.

Cutting-edge biotechnological advancement in islet delivery using pancreatic and cellular approaches

There are approximately 1 billion prediabetic people worldwide, and the global cost for diabetes mellitus (DM) is estimated to be $825 billion. In regard to Type 1 DM, transplanting a whole pancreas or its islets has gained the attention of researchers in the last few decades. Recent studies showed that islet transplantation (ILT) containing insulin-producing β cells is the most notable advancement cure for Type 1 DM. However, this procedure has been hindered by shortage and lack of sufficient islet donors and the need for long-term immunosuppression of any potential graft rejection. The strategy of encapsulation may avoid the rejection of stem-cell-derived allogeneic islets or xenogeneic islets. This review article describes various biotechnology features in encapsulation-of-islet-cell therapy for humans, including the use of bile acids.

Noninvasive diagnosis of recurrent autoimmune type 1 diabetes after islet cell transplantation

Islet cell transplantation is curative therapy for patients with complicated autoimmune type 1 diabetes (T1D). We report the diagnostic potential of circulating transplant islet-specific exosomes to noninvasively distinguish pancreatic β cell injury secondary to recurrent autoimmunity vs immunologic rejection. A T1D patient with hypoglycemic unawareness underwent islet transplantation and maintained normoglycemia until posttransplant day 1098 before requiring exogenous insulin. Plasma analysis showed decreased donor islet exosome quantities on day 1001, before hyperglycemia onset. This drop in islet exosome quantity signified islet injury, but did not distinguish injury type. However, analysis of purified transplant islet exosome cargoes showed decrease in insulin-containing exosomes, but not glucagon-containing exosomes, indicating selective destruction of transplanted β cells secondary to recurrent T1D autoimmunity. Furthermore, donor islet exosome cargo analysis showed time-specific increase in islet autoantigen, glutamic acid decarboxylase 65 (GAD65), implicated in T1D autoimmunity. Time-matched analysis of plasma transplant islet exosomes in 3 control subjects undergoing islet cell transplantation failed to show changes in islet exosome quantities or intraexosomal cargo expression of insulin, glucagon, and GAD65. This is the first report of noninvasive diagnosis of recurrent autoimmunity after islet cell transplantation, suggesting that transplant tissue exosome platform may serve as a biomarker in islet transplant diagnostics.

Pancreatic Islet Transplantation in Humans: Recent Progress and Future Directions

Pancreatic islet transplantation has become an established approach to β-cell replacement therapy for the treatment of insulin-deficient diabetes. Recent progress in techniques for islet isolation, islet culture, and peritransplant management of the islet transplant recipient has resulted in substantial improvements in metabolic and safety outcomes for patients. For patients requiring total or subtotal pancreatectomy for benign disease of the pancreas, isolation of islets from the diseased pancreas with intrahepatic transplantation of autologous islets can prevent or ameliorate postsurgical diabetes, and for patients previously experiencing painful recurrent acute or chronic pancreatitis, quality of life is substantially improved. For patients with type 1 diabetes or insulin-deficient forms of pancreatogenic (type 3c) diabetes, isolation of islets from a deceased donor pancreas with intrahepatic transplantation of allogeneic islets can ameliorate problematic hypoglycemia, stabilize glycemic lability, and maintain on-target glycemic control, consequently with improved quality of life, and often without the requirement for insulin therapy. Because the metabolic benefits are dependent on the numbers of islets transplanted that survive engraftment, recipients of autoislets are limited to receive the number of islets isolated from their own pancreas, whereas recipients of alloislets may receive islets isolated from more than one donor pancreas. The development of alternative sources of islet cells for transplantation, whether from autologous, allogeneic, or xenogeneic tissues, is an active area of investigation that promises to expand access and indications for islet transplantation in the future treatment of diabetes.

Characterization of Insulin-Secreting Porcine Bone Marrow Stromal Cells Ex Vivo and Autologous Cell Therapy in Vivo

Cell therapy could potentially meet the need for pancreas and islet transplantations in diabetes mellitus that far exceeds the number of available donors. Bone marrow stromal cells are widely used in clinical trials mainly for their immunomodulatory effects with a record of safety. However, less focus has been paid to developing these cells for insulin secretion by transfection. Although murine models of diabetes have been extensively used in gene and cell therapy research, few studies have shown efficacy in large preclinical animal models. Here we report optimized conditions for ex vivo expansion and characterization of porcine bone marrow stromal cells and their permissive expression of a transfected insulin gene. Our data show that these cells resemble human bone marrow stromal cells in surface antigen expression, are homogeneous, and can be reproducibly isolated from outbred Yorkshire–Landrace pigs. Porcine bone marrow stromal cells were efficiently expanded in vitro to >1010 cells from 20 ml of bone marrow and remained karyotypically normal during expansion. These cells were electroporated with an insulin expression plasmid vector with high efficiency and viability, and secreted human insulin and C-peptide indicating appropriate processing of proinsulin. We showed that autologous insulin-secreting bone marrow stromal cells implanted and engrafted in the liver of a streptozotocin-diabetic pig that modeled type 1 diabetes resulted in partial, but significant, improvement in hyperglycemia that could not be ascribed to regeneration of endogenous β-cells. Glucose-stimulated insulin secretion in vivo from implanted cells in the treated pig was documented by a rise in serum human C-peptide levels during intravenous glucose tolerance tests. Compared to a sham-treated control pig, this resulted in significantly reduced fasting hyperglycemia, a slower rise in serum fructosamine, and prevented weight loss. Taken together, this study suggests that bone marrow stromal cells merit further development as autologous cell therapy for diabetes.

Bioengineered stem cells as an alternative for islet cell transplantation

Type 1 diabetes is an autoimmune and increasingly prevalent condition caused by immunological destruction of beta cells. Insulin remains the mainstay of therapy. Endeavours in islet transplantation have clearly demonstrated that type 1 diabetes is treatable by cellular replacement. Many challenges remain with this approach. The opportunity to use bioengineered embryonic or adult pluripotential stem cells, or islets derived from porcine xenograft sources could address future demands, but are still associated with considerable challenges. This detailed review outlines current progress in clinical islet transplantation, and places this in perspective for the remarkable scientific advances now occurring in stem cell and regenerative medicine approaches in the treatment of future curative treatment of diabetes.

Monitoring Inflammation, Humoral and Cell-mediated Immunity in Pancreas and Islet Transplants

Type 1 diabetes (T1D) is caused by the chronic autoimmune destruction of insulin producing beta cells. Beta cell replacement therapy through whole pancreas or islet transplantation is a therapeutic option for patients in which a stable glucose control is not achievable with exogenous insulin therapy. Long-term insulin independence is, however, hampered by the recipient immune response that includes activation of inflammatory pathways and specific allo- and autoimmunity. The identification and monitoring of soluble and cellular biomarkers are of critical relevance for the prediction of graft damage, for the evaluation of responses to immune-modulating therapy, and for target pathways identification to generate novel drugs or therapeutic approaches. The final objective of immune monitoring is to find ways to improve the outcome of pancreas and islet transplantation. In this review, we discuss the available tools to monitor the innate, humoral and cellular responses after islet and pancreas transplantation, and the most relevant findings generated by these measurements.

Stem cell therapy. Use of differentiated pluripotent stem cells as replacement therapy for treating disease

Pluripotent stem cells (PSCs) directed to various cell fates holds promise as source material for treating numerous disorders. The availability of precisely differentiated PSC-derived cells will dramatically affect blood component and hematopoietic stem cell therapies and should facilitate treatment of diabetes, some forms of liver disease and neurologic disorders, retinal diseases, and possibly heart disease. Although an unlimited supply of specific cell types is needed, other barriers must be overcome. This review of the state of cell therapies highlights important challenges. Successful cell transplantation will require optimizing the best cell type and site for engraftment, overcoming limitations to cell migration and tissue integration, and occasionally needing to control immunologic reactivity, as well as a number of other challenges. Collaboration among scientists, clinicians, and industry is critical for generating new stem cell-based therapies.

Assessment of human islet grafts in frozen sections of CD-1 athymic nu/nu mouse liver for molecular analysis

BACKGROUND

Post-transplantation islet graft monitoring is hampered by a lack of efficient methods to locate and analyze islets in situ. We evaluated histologic methods to rapidly locate islets within the liver parenchyma post-transplantation, using several staining strategies, prior to analysis using laser capture microdissection.

METHODS

Human islets were isolated (n = 8) from brain dead, multiorgan donor pancreases at the McGill University Health Centre Islet Transplant Laboratory. Mean yield was 247,609 ± 195,272 IE and 3172 ± 1645 IE/g (purity and viability, respectively, 84.5 ± 8.6% and 95 ± 5% average; mean ± SD). Diabetic athymic CD-1 nu/nu mice (streptozotocin intraperitoneal injection, 200 mg/kg) were maintained with sustained release insulin pellets until a suitable islet preparation was available for transplant. Intraportal islet transplantation of 2000 IE/mouse was performed via the ileocecal vein, as previously described. Frozen sections of liver containing human islets were prepared from specimens collected on days 0, 4, and 30 post-transplant. Every twentieth slide from serial sectioned liver was stained using a rapid protocol to determine if islets were present. Sections were fixed and stained for 5 minutes with either an anti-human insulin fluorescein isothiocyanate (FITC)-conjugated primary antibody (Ins-FITC), Newport Green (NG), or diphenylthiocarbazone (dithizone, DZ).

RESULTS

Islets were readily localized using each technique, mostly toward the liver periphery. However, DZ had a faint appearance in 10-μm-thick sections and was best utilized to locate sections containing islets during sectioning.

CONCLUSION

Ins-FITC, NG, and DZ are all good candidates for a rapid islet staining protocol to evaluate human islet grafts in situ, with DZ being best for sectioning and Ins-FITC and NG being equal in locating islets during processing for laser capture microdissection.

Transplantation of Encapsulated Pancreatic Islets as a Treatment for Patients with Type 1 Diabetes Mellitus

Encapsulation of pancreatic islets has been proposed and investigated for over three decades to improve islet transplantation outcomes and to eliminate the side effects of immunosuppressive medications. Of the numerous encapsulation systems developed in the past, microencapsulation have been studied most extensively so far. A wide variety of materials has been tested for microencapsulation in various animal models (including nonhuman primates or NHPs) and some materials were shown to induce immunoprotection to islet grafts without the need for chronic immunosuppression. Despite the initial success of microcapsules in NHP models, the combined use of islet transplantation (allograft) and microencapsulation has not yet been successful in clinical trials. This review consists of three sections: introduction to islet transplantation, transplantation of encapsulated pancreatic islets as a treatment for patients with type 1 diabetes mellitus (T1DM), and present challenges and future perspectives.

Impact of islet size on pancreatic islet transplantation and potential interventions to improve outcome

Better results have been recently reported in clinical pancreatic islet transplantation (ITX) due mostly to improved isolation techniques and immunosuppression; however, some limitations still exist. It is known that following transplantation, 30% to 60% of the islets are lost. In our study, we have investigated 1) the role of size as a factor affecting islet engraftment and 2) potential procedural manipulations to increase the number of smaller functional islets that can be transplanted. C57/BL10 mice were used as donors and recipients in a syngeneic islet transplant model. Isolated islets were divided by size (large, >300 μm; medium 150-300 μm; small, <150 μm). Each size was transplanted in chemically induced diabetic mice as full (600 IEQ), suboptimal (400 IEQ), and marginal mass (200 IEQ). Control animals received all size islets. Engraftment was defined as reversal of diabetes by day 7 posttransplantation. When the superiority of smaller islets was observed, strategies of overdigestion and fragmentation were adopted during islet isolation in the attempt to reduce islet size and improve engraftment. Smaller islets were significantly superior in engraftment compared to medium, large, and control (all sizes) groups. This was more evident when marginal mass data were compared. In all masses, success decreased as islet size increased. Once islets were engrafted, functionality was not affected by size. When larger islets were fragmented, a significant decrease in islet functionality was observed. On the contrary, if pancreata were slightly overdigested, although not as successful as small naive islets, an increase in engraftment was observed when compared to the control group. In conclusion, smaller islets are superior in engraftment following islet transplantation. Fragmentation has a deleterious effect on islet engraftment. Islet isolations can be performed by reducing islet size with slight overdigestion, and it can be safely adopted to improve clinical outcome.

Update on islet transplantation

Clinical islet transplantation has progressed considerably over the past 12 years, and >750 patients with type 1 diabetes have received islet transplants internationally over this time. Many countries are beginning to accept the transition from research to accepted and funded clinical care, especially for patients with brittle control that cannot be stabilized by more conventional means. Major challenges remain, including the need for more than one donor, and the requirement for potent, chronic immunosuppression. Combining immunological tolerance both to allo- and autoantigens, and a limitless expandable source of stem cell- or xenograft-derived insulin-secreting cells represent remaining hurdles in moving this effective treatment to a potential cure for all those with type 1 or 2 diabetes.

Alloantibody and autoantibody monitoring predicts islet transplantation outcome in human type 1 diabetes

Long-term clinical outcome of islet transplantation is hampered by the rejection and recurrence of autoimmunity. Accurate monitoring may allow for early detection and treatment of these potentially compromising immune events. Islet transplant outcome was analyzed in 59 consecutive pancreatic islet recipients in whom baseline and de novo posttransplant autoantibodies (GAD antibody, insulinoma-associated protein 2 antigen, zinc transporter type 8 antigen) and donor-specific alloantibodies (DSA) were quantified. Thirty-nine recipients (66%) showed DSA or autoantibody increases (de novo expression or titer increase) after islet transplantation. Recipients who had a posttransplant antibody increase showed similar initial performance but significantly lower graft survival than patients without an increase (islet autoantibodies P < 0.001, DSA P < 0.001). Posttransplant DSA or autoantibody increases were associated with HLA-DR mismatches (P = 0.008), induction with antithymocyte globulin (P = 0.0001), and pretransplant panel reactive alloantibody >15% in either class I or class II (P = 0.024) as independent risk factors and with rapamycin as protective (P = 0.006) against antibody increases. DSA or autoantibody increases after islet transplantation are important prognostic markers, and their identification could potentially lead to improved islet cell transplant outcomes.

Transplanted human pancreatic islets after long-term insulin independence

Long-term insulin independence after islets of Langerhans transplantation is rarely achieved. The aims of this study were to identify the histological and immunological features of islets transplanted in a type 1 diabetic patient who died of a cerebral hemorrhage after >13 years insulin independence. Islets were pooled from two donors with respectively one and five HLA mismatches. Insulin-positive islets were found throughout the right and left liver, and absent in the pancreas. Two- and three-dimensional analysis showed that islets lost their initial rounded and compact morphology, had a mean diameter of 136 μm and were constituted of an unfolded epithelial band of 39.1 μm. Leukocyte phenotyping showed no evidence of a tolerogenic environment in the islet-containing portal spaces. Finally, HLA typing of microdissected islets showed HLA from the best matched donor in all 23 microdissection samples, compared to 1/23 for the least matched donor. This case report demonstrates that allogeneic islets can survive over 13 years while maintaining insulin independence. Allogeneic islets had unique morphologic features and implanted in the liver regardless of their size. Finally, our results suggest that, in this case, rejection had been prevalent over autoimmunity, although this hypothesis warrants further investigation.

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

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

Theranostic magnetic resonance imaging of type 1 diabetes and pancreatic islet transplantation

Type 1 diabetes mellitus results in impaired insulin production by pancreatic islets due to autoimmunity. Islet transplantation has recently emerged as a promising treatment for this disease. To visualize and monitor endogenous and transplanted islets, non-invasive strategies are currently being developed. These include strategies for in vivo magnetic resonance imaging of microvascular changes during diabetes development, tracking the recruitment of diabetogenic T cells to the pancreas, and imaging of endogenous and transplanted islet mass. The combination of MR imaging agents with therapy is a novel state-of-the-art theranostic approach that has a tremendous potential for type 1 diabetes management. Though still in its infancy, theranostic MR imaging has shown certain encouraging progress. Here we provide an overview of the latest accomplishments in this area as it applies to changes in islet vasculature during diabetes development, monitoring autoimmune attack mediated by T cells, and imaging of transplanted islets. Future challenges and opportunities in the area of theranostic MRI are discussed as well.

A theranostic small interfering RNA nanoprobe protects pancreatic islet grafts from adoptively transferred immune rejection

Islet transplantation has recently emerged as an acceptable clinical modality for restoring normoglycemia in patients with type 1 diabetes mellitus (T1DM). The long-term survival and function of islet grafts is compromised by immune rejection-related factors. Downregulation of factors that mediate immune rejection using RNA interference holds promise for improving islet graft resistance to damaging factors after transplantation. Here, we used a dual-purpose therapy/imaging small interfering (si)RNA magnetic nanoparticle (MN) probe that targets β(2) microglobulin (B2M), a key component of the major histocompatibility class I complex (MHC I). In addition to serving as a siRNA carrier, this MN-siB2M probe enables monitoring of graft persistence noninvasively using magnetic resonance imaging (MRI). Human islets labeled with these MNs before transplantation into B2M (null) NOD/scid mice showed significantly improved preservation of graft volume starting at 2 weeks, as determined by longitudinal MRI in an adoptive transfer model (P < 0.05). Furthermore, animals transplanted with MN-siB2M-labeled islets demonstrated a significant delay of up to 23.8 ± 4.8 days in diabetes onset after the adoptive transfer of T cells relative to 6.5 ± 4.5 days in controls. This study demonstrated that our approach could protect pancreatic islet grafts from immune rejection and could potentially be applied to allotransplantation and prevention of the autoimmune recurrence of T1DM in islet transplantation or endogenous islets.

Endogenous expansion of regulatory T cells leads to long-term islet graft survival in diabetic NOD mice

Donor pancreatic lymph node cells (PLNC) protect islet transplants in Non-obese diabetic (NOD) mice. We hypothesized that induced FoxP3(+) regulatory T cells (Tregs) were required for long-term islet engraftment. NOD or NOD.NON mice were treated with ALS (antilymphocyte serum) and transplanted with NOR islets +/-PLNC (5 × 10(7) ). In vivo proliferation and expansion of FoxP3(+) Tregs was monitored in spleen and PLN from ALS- and ALS/PLNC-treated recipient mice. Anti-CD25 depletion was used to determine the necessity of Tregs for tolerance. FoxP3(+) numbers significantly increased in ALS/PLNC-treated recipients compared to ALS-treated mice. In ALS/PLNC-treated mice, recipient-derived Tregs localized to the transplanted islets, and this was associated with intact, insulin-producing β cells. Proliferation and expansion of FoxP3(+) Tregs was markedly increased in PLNC-treated mice with accepted islet grafts, but not in diabetic mice not receiving PLNC. Deletion of Tregs with anti-CD25 antibodies prevented islet graft tolerance and resulted in rejection. Adoptive transfer of Tregs to secondary NOD.scid recipients inhibited autoimmunity by cotransferred NOD effector T cells. Treg expansion induced by ALS/PLNC-treatment promoted long term islet graft survival. Strategies leading to Treg proliferation and localization to the transplant site represent a therapeutic approach to controlling recurrent autoimmunity.

Accumulation of intrahepatic islet amyloid in a nonhuman primate transplant model

Islet amyloid is hypothesized to play a role in nonimmunologic transplanted islet graft loss. We performed a quantitative histologic analysis of liver biopsies from intrahepatic islet grafts transplanted in streptozotocin-induced diabetic cynomolgus macaques. Seven animals treated with antithymocyte globulin (ATG) and rapamycin or ATG and rituximab experienced islet graft rejection with lymphocytic infiltrates present on islet graft biopsies. Except for one case involving the oldest and largest donor where amyloid was present on initial biopsy 1 month after transplant, none of the six other cases with rejection contained amyloid, including one case biopsied serially to 25 months. In contrast, four out of six animals treated with ATG and rituximab and rapamycin had no evidence of rejection at the time of biopsy (two animals that discontinued rapamycin had mild periislet lymphocytes), and all four cases followed more than 4 months demonstrated amyloid deposition at subsequent time points. Amyloid severity increased with time after transplant (r = 0.68; P < 0.05) and with decreasing islet β-cell area (r = -0.68; P < 0.05). In two islet recipients with no evidence of rejection and still normoglycemic and insulin independent at the first detection of amyloid, β-cell secretory capacity declined over time coincident with increasing amyloid severity and decreasing β-cell area, with both animals eventually becoming hyperglycemic and insulin dependent. Transplanted islet amyloid also developed in autologous islets placed sc. These results indicate that in cynomolgus macaques, transplanted islets may accumulate amyloid over time associated with subsequent decline in β-cell mass and function and support the development of intrahepatic islet amyloid as a potential mechanism for nonimmunologic islet graft loss.

HLA class I sensitization in islet transplant recipients: report from the Collaborative Islet Transplant Registry

Pancreatic islet transplantation is a promising treatment option for patients severely affected with type 1 diabetes. This report from CITR presents pre- and posttransplant human leukocyte antigen (HLA) class I sensitization rates in islet-alone transplantation. Data came from 303 recipients transplanted with islet-alone between January 1999 and December 2008. HLA class I sensitization was determined by the presence of anti-HLA class I antibodies. Panel-reactive antibodies (PRA) from prior to islet infusion and at 6 months, and yearly posttransplant was correlated to measures of islet graft failure. The cumulative number of mismatched HLA alleles increased with each additional islet infusion from a median of 3 for one infusion to 9 for three infusions. Pretransplant PRA was not predictive of islet graft failure. However, development of PRA >20% posttransplant was associated with 3.6-fold (p < 0.001) increased hazard ratio for graft failure. Patients with complete graft loss who had discontinued immunosuppression had significantly higher rate of PRA ≥ 20% compared to those with functioning grafts who remained on immunosuppression. Exposure to repeat HLA class I mismatch at second or third islet infusions resulted in less frequent development of de novo HLA class I antibodies when compared to increased class I mismatch. The development of HLA class I antibodies while on immunosuppression is associated with subsequent islet graft failure. The risk of sensitization may be reduced by minimizing the number of islet donors used per recipient, and in the absence of donor-specific anti-HLA antibodies, repeating HLA class I mismatches with subsequent islet infusions.

Expression of pro- and antiapoptotic molecules of the Bcl-2 family in human islets postisolation

Human islets are subjected to a number of stresses before and during their isolation that may influence their survival and engraftment after transplantation. Apoptosis is likely to be activated in response to these stresses. Apoptosis due to intrinsic stresses is regulated by pro- and antiapoptotic members of the Bcl-2 family. While the role of the Bcl-2 family in apoptosis of rodent islets is becoming increasingly understood, little is known about which of these molecules are expressed or required for apoptosis of human islets. This study investigated the expression of the Bcl-2 family of molecules in isolated human islets. RNA and protein lysates were extracted from human islets immediately postisolation. At the same time, standard quality control assays including viability staining and β-cell content were performed on each islet preparation. Microarrays, RT-PCR, and Western blotting were performed on islet RNA and protein. The prosurvival molecules Bcl-xl and Mcl-1, but not Bcl-2, were highly expressed. The multidomain proapoptotic effector molecule Bax was expressed at higher levels than Bak. Proapoptotic BH3-only molecules were expressed at low levels, with Bid being the most abundant. The proapoptotic molecules BNIP3, BNIP3L, and Beclin-1 were all highly expressed, indicating exposure of islets to oxygen and nutrient deprivation during isolation. Our data provide a comprehensive analysis of expression levels of pro- and antiapoptotic Bcl-2 family members in isolated human islets. Knowledge of which molecules are expressed will guide future research to understand the apoptotic pathways activated during isolation or after transplantation. This is crucial for the design of methods to achieve improved transplantation outcomes.

Recurrence of autoimmunity in pancreas transplant patients: research update

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

Silencing inducible nitric oxide synthase protects rat pancreatic islet

OBJECTIVE

To investigate the effect of inducible nitric oxide synthase (iNOS) RNA interference on cytokine-induced injury of pancreatic islet in rats.

MATERIALS AND METHODS

Islets from Wistar rats were cultured in vitro and then randomly divided into five groups: group A, islets were cultured exclusively; group B, islets were transfected with negative control siRNA; group C, islets were transfected with iNOS siRNA; group D, islets were transfected with iNOS siRNA and then treated with TNF-alpha+IL-1beta; group E, islets were treated with TNF-alpha+IL-1beta. The expression of iNOS, Bax and Fas was determined by RT-PCR and Western blot. The viability of islet was examined by AO/EB staining and function was examined by glucose-stimulated insulin secretion (GSIS) assay.

RESULTS

The expression of iNOS and the promoting apoptosis gene Bax and Fas were significantly up-regulated by the induction of IL-1beta and TNF-alpha. Thus they led to apoptosis increase and the insulin secretion index decrease (1.87+/-0.31 vs 3.83+/-1.40, P<0.01). Silencing iNOS by RNAi prevented the up-regulation of Bax and Fas induced by cytokine, thus reduced apoptosis of islets and recovered the insulin secretion index (3.43+/-0.24 vs 1.87+/-0.31, P<0.01).

CONCLUSION

The apoptosis from cytokines to islets mediated by iNOS could be suppressed by RNA interference, which favors the survival and function of islets.

Histologic graft assessment after clinical islet transplantation

BACKGROUND

An accurate monitoring would help understanding the fate of islet grafts after transplantation.

METHODS

This work assessed the feasibility of needle biopsy monitoring after intraportal islet transplantation (n=16), and islet graft morphology was studied with the addition of autopsy samples (n=2). Pancreas autopsy samples from two nondiabetic individuals were used as control.

RESULTS

Islet tissue was found in five needle samples (31%). Sampling success was related to size (100% sampling for the four biopsies of 1.8 cm in length or higher, P<or=0.01). Mild liver abnormalities included localized steatosis (n=8), mild nodular regenerative hyperplasia and mild portal venopathy (n=3), and hepatocyte swelling (n=2). Endocrine cell composition and distribution were similar between islet grafts and normal islets within the native pancreas. There was no or minimal immune cell infiltrate in patients on and off exogenous insulin, including two patients with ongoing negative metabolic events (increasing HbA1c or insulin requirement). The infiltrate was mainly composed of CD4- and CD8-positive cells.

CONCLUSION

This study demonstrates that needle biopsy is feasible after clinical islet transplantation but with a limited practical value because of its low islet sampling rate using current sampling and analysis methods. Both biopsy and autopsy samples demonstrated the well-preserved islet endocrine composition after transplantation and the presence of focal areas of steatosis. Islet grafts showed no or minimal immune cell infiltration, even in the case of ongoing islet loss. On the basis of the findings, possible reasons for allograft islet loss are discussed.

Primary graft function, metabolic control, and graft survival after islet transplantation

OBJECTIVE To investigate the influence of primary graft function (PGF) on graft survival and metabolic control after islet transplantation with the Edmonton protocol. RESEARCH DESIGN AND METHODS A total of 14 consecutive patients with brittle type 1 diabetes were enrolled in this phase 2 study and received median 12,479 islet equivalents per kilogram of body weight (interquartile range 11,072-15,755) in two or three sequential infusions within 67 days (44-95). PGF was estimated 1 month after the last infusion by the beta-score, a previously validated index (range 0-8) based on insulin or oral treatment requirements, plasma C-peptide, blood glucose, and A1C. Primary outcome was graft survival, defined as insulin independence with A1C < or =6.5%. RESULTS All patients gained insulin independence within 12 days (6-23) after the last infusion. PGF was optimal (beta-score > or =7) in nine patients and suboptimal (beta-score < or =6) in five. At last follow-up, 3.3 years (2.8-4.0) after islet transplantation, eight patients (57%) remained insulin independent with A1C < or =6.5%, including seven patients with optimal PGF (78%) and one with suboptimal PGF (20%) (P = 0.01, log-rank test). Graft survival was not significantly influenced by HLA mismatches or by preexisting islet autoantibodies. A1C, mean glucose, glucose variability (assessed with continuous glucose monitoring system), and glucose tolerance (using an oral glucose tolerance test) were markedly improved when compared with baseline values and were significantly lower in patients with optimal PGF than in those with suboptimal PGF. CONCLUSIONS Optimal PGF was associated with prolonged graft survival and better metabolic control after islet transplantation. This early outcome may represent a valuable end point in future clinical trials.

Early metabolic markers of islet allograft dysfunction

BACKGROUND

Islet transplantation can restore normoglycemia to patients with unstable type 1 diabetes mellitus, but long-term insulin independence is usually not sustained. Identification of predictor(s) of islet allograft dysfunction (IGD) might allow for early intervention(s) to preserve functional islet mass.

METHODS

Fourteen islet transplantation recipients with long-term history of type 1 diabetes mellitus underwent metabolic testing by mixed meal tolerance test, intravenous glucose tolerance test, and arginine stimulation test every 3 months postislet transplant completion. Metabolic responses were compared between subjects who maintained insulin independence at 18 months (group 1; n=5) and those who restarted insulin within 18 months (group 2; n=9). Data were analyzed before development of islet graft dysfunction and while insulin independent.

RESULTS

The 90-min glucose, time-to-peak C-peptide, and area under the curve for glucose were consistently higher in group 2 and increased as a function of time. At 12 months, acute insulin release to glucose in group 2 was markedly reduced as compared with baseline (5.62+/-1.21 microIU/mL, n=4 vs. 16.14+/-3.69 microIU/mL, n=8), whereas it remained stable in group 1 (22.36+/-4.98 microIU/mL, n=5 vs. 27.70+/-2.83 microIU/mL, n=5). Acute insulin release to glucose, acute C-peptide release to glucose (ACpRg), and mixed meal stimulation index were significantly decreased and time-to-peak C-peptide, 90-min glucose, and area under the curve for glucose were significantly increased when measured at time points preceding intervals where IGD occurred compared with intervals where there was no IGD.

CONCLUSIONS

The intravenous glucose tolerance test and mixed meal tolerance test may be useful in the prediction of IGD and should be essential components of the metabolic testing of islet transplant recipients.

The role of macrophage migration inhibitory factor in mouse islet transplantation

BACKGROUND

Macrophage migration inhibitory factor (MIF) is a proinflammatory cytokine produced by many tissues including pancreatic beta-cells.

METHODS

This study investigates the impact of MIF on islet transplantation using MIF knock-out (MIFko) mice.

RESULTS

Early islet function, assessed with a syngeneic marginal islet mass transplant model, was enhanced when using MIFko islets (P<0.05 compared with wild-type [WT] controls). This result was supported by increased in vitro resistance of MIFko islets to apoptosis (terminal deoxynucleotide tranferase-mediated dUTP nick-end labeling assay), and by improved glucose metabolism (lower blood glucose levels, reduced glucose areas under curve and higher insulin release during intraperitoneal glucose challenges, and in vitro in the absence of MIF, P<0.01). The beneficial impact of MIFko islets was insufficient to delay allogeneic islet rejection. However, the rejection of WT islet allografts was marginally delayed in MIFko recipients by 6 days when compared with WT recipient (P<0.05). This effect is supported by the lower activity of MIF-deficient macrophages, assessed in vitro and in vivo by cotransplantation of islet/macrophages. Leukocyte infiltration of the graft and donor-specific lymphocyte activity (mixed lymphocyte reaction, interferon gamma ELISPOT) were similar in both groups.

CONCLUSION

These data indicate that targeting MIF has the potential to improve early function after syngeneic islet transplantation, but has only a marginal impact on allogeneic rejection.

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

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

The use of exenatide in islet transplant recipients with chronic allograft dysfunction: safety, efficacy, and metabolic effects

BACKGROUND

A current limitation of islet transplantation is reduced long-term graft function. The glucagon-like peptide-1 receptor agonist, exenatide (Byetta, Amylin Pharmaceuticals, CA) has properties that could improve existing islet function, prevent further loss of islet mass and possibly even stimulate islet regeneration.

METHODS

This prospective study evaluated the safety, efficacy, and metabolic effects of exenatide in subjects with type 1 diabetes mellitus and islet allograft dysfunction requiring exogenous insulin.

RESULTS

Sixteen subjects commenced exenatide, 12 continue (follow-up 214+/-57 days; range 108-287), four (25%) discontinued medication because of side effects. At 6 months, exogenous insulin was significantly reduced with stable glycemic control (0.15+/-0.02 vs. 0.11+/-0.025 U/kg per day; P<0.0001); three subjects discontinued insulin from 4, 5, and 9 U/day, respectively, two sustained insulin independence with A1c reduction below graft dysfunction criteria. Postprandial capillary blood glucose was significantly decreased (129.4+/-3.8 vs. 118.7+/-4.6 mg/dL; P<0.001), C-peptide and C-peptide-to-glucose ratio increased significantly by 5th and 6th months of treatment (ratio, 1.09+/-0.15 vs. 1.52+/-0.18; P<0.05). Weight loss more than 3 kg occurred in 8 of 12 (67%) subjects. Stimulation testing demonstrated improved glucose disposal and C-peptide secretion (glucose area under the curve 52,332+/-3,219 vs. 42,072+/-1,965; P=0.002 mg x min x dL, mixed meal stimulation index 0.50+/-0.06 vs. 0.66+/-0.09; P=0.03 pmol x mL), with marked suppression of glucagon secretion and progressive increase in amylin secretion. Side effects were more frequent and severe compared with published reports in type 2 diabetes, tolerated doses were lower.

CONCLUSIONS

Exenatide was tolerated in this patient population after appropriate dose titration and there appeared to be gradual but sustained positive effects on glycemic control and islet graft function.

Acute insulin responses to glucose and arginine as predictors of beta-cell secretory capacity in human islet transplantation

Islet transplantation for type 1 diabetes can enable the achievement of near-normal glycemic control without severe hypoglycemic episodes. How much an islet (beta-cell) graft may be contributing to glycemic control can be quantified by stimulatory tests of insulin (or C-peptide) secretion. Glucose-potentiation of arginine-induced insulin secretion provides a measure of functional beta-cell mass, the beta-cell secretory capacity, as either AIR(pot) or AIR(max), but requires conduct of a hyperglycemic clamp. We sought to determine whether acute insulin responses to intravenous glucose (AIR(glu)) or arginine (AIR(arg)) could predict beta-cell secretory capacity in islet recipients. AIR(arg) was a better predictor of both AIR(pot) and AIR(max) (n=10, r2=0.98, P<0.0001 and n=7, r2=0.97, P<0.0001) than was AIR(glu) (n=9, r2=0.78, P=0.002 and n=6, r2=0.76, P=0.02). Also, the measures of beta-cell secretory capacity were highly correlated (n=7, r2=0.98, P<0.0001). These results support the use of AIR(arg) as a surrogate indicator of beta-cell secretory capacity in islet transplantation.

Allogeneic islet transplantation

Significant progress has been made in the field of beta-cell replacement therapies by islet transplantation in patients with unstable Type 1 diabetes mellitus (T1DM). Recent clinical trials have shown that islet transplantation can reproducibly lead to insulin independence when adequate islet numbers are implanted. Benefits include improvement of glycemic control, prevention of severe hypoglycemia and amelioration of quality of life. Numerous challenges still limit this therapeutic option from becoming the treatment of choice for T1DM. The limitations are primarily associated with the low islet yield of human pancreas isolations and the need for chronic immunosuppressive therapies. Herein the authors present an overview of the historical progress of islet transplantation and outline the recent advances of the field. Cellular therapies offer the potential for a cure for patients with T1DM. The progress in beta-cell replacement treatment by islet transplantation as well as those of emerging immune interventions for the restoration of self tolerance justify great optimism for years to come.