Recurrence of autoimmunity in pancreas transplant patients: research update

Banff 2022 pancreas transplantation multidisciplinary report: Refinement of guidelines for T cell-mediated rejection, antibody-mediated rejection and islet pathology. Assessment of duodenal cuff biopsies and noninvasive diagnostic methods

The Banff pancreas working schema for diagnosis and grading of rejection is widely used for treatment guidance and risk stratification in centers that perform pancreas allograft biopsies. Since the last update, various studies have provided additional insight regarding the application of the schema and enhanced our understanding of additional clinicopathologic entities. This update aims to clarify terminology and lesion description for T cell-mediated and antibody-mediated allograft rejections, in both active and chronic forms. In addition, morphologic and immunohistochemical tools are described to help distinguish rejection from nonrejection pathologies. For the first time, a clinicopathologic approach to islet pathology in the early and late posttransplant periods is discussed. This update also includes a discussion and recommendations on the utilization of endoscopic duodenal donor cuff biopsies as surrogates for pancreas biopsies in various clinical settings. Finally, an analysis and recommendations on the use of donor-derived cell-free DNA for monitoring pancreas graft recipients are provided. This multidisciplinary effort assesses the current role of pancreas allograft biopsies and offers practical guidelines that can be helpful to pancreas transplant practitioners as well as experienced pathologists and pathologists in training.

Immunoengineering Biomaterials in Cell-Based Therapy for Type 1 Diabetes

Type 1 diabetes (T1D) is caused by low insulin production and chronic hyperglycemia due to the destruction of pancreatic β-cells. Cell transplantation is an attractive alternative approach compared to insulin injection. However, cell therapy has been limited by major challenges including life-long requirements for immunosuppressive drugs in order to prevent host immune responses. Encapsulation of the transplanted cells can solve the problem of immune rejection, by providing a physical barrier between the transplanted cells and the recipient's immune cells. Despite current disputes in cell encapsulation approaches, thanks to recent advances in the fields of biomaterials and transplantation immunology, extensive effort has been dedicated to immunoengineering strategies in combination with encapsulation technologies to overcome the problem of the host's immune responses. The current review summarizes the most commonly used encapsulation and immunoengineering strategies combined with cell therapy which has been applied as a novel approach to improve cell replacement therapies for the management of T1D. Recent advances in the fields of biomaterial design, nanotechnology, as well as deeper knowledge about immune modulation had significantly improved cell encapsulation strategies. However, further progress requires the combined application of novel immunoengineering approaches and islet/ß-cell transplantation.

Identification and characterisation of tertiary lymphoid organs in human type 1 diabetes

AIMS/HYPOTHESIS

We and others previously reported the presence of tertiary lymphoid organs (TLOs) in the pancreas of NOD mice, where they play a role in the development of type 1 diabetes. Our aims here are to investigate whether TLOs are present in the pancreas of individuals with type 1 diabetes and to characterise their distinctive features, in comparison with TLOs present in NOD mouse pancreases, in order to interpret their functional significance.

METHODS

Using immunofluorescence confocal microscopy, we examined the extracellular matrix (ECM) and cellular constituents of pancreatic TLOs from individuals with ongoing islet autoimmunity in three distinct clinical settings of type 1 diabetes: at risk of diabetes; at/after diagnosis; and in the transplanted pancreas with recurrent diabetes. Comparisons were made with TLOs from 14-week-old NOD mice, which contain islets exhibiting mild to heavy leucocyte infiltration. We determined the frequency of the TLOs in human type 1diabetes with insulitis and investigated the presence of TLOs in relation to age of onset, disease duration and disease severity.

RESULTS

TLOs were identified in preclinical and clinical settings of human type 1 diabetes. The main characteristics of these TLOs, including the cellular and ECM composition of reticular fibres (RFs), the presence of high endothelial venules and immune cell subtypes detected, were similar to those observed for TLOs from NOD mouse pancreases. Among 21 donors with clinical type 1 diabetes who exhibited insulitis, 12 had TLOs and had developed disease at younger age compared with those lacking TLOs. Compartmentalised TLOs with distinct T cell and B cell zones were detected in donors with short disease duration. Overall, TLOs were mainly associated with insulin-containing islets and their frequency decreased with increasing severity of beta cell loss. Parallel studies in NOD mice further revealed some differences in so far as regulatory T cells were essentially absent from human pancreatic TLOs and CCL21 was not associated with RFs.

CONCLUSIONS/INTERPRETATION

We demonstrate a novel feature of pancreas pathology in type 1 diabetes. TLOs represent a potential site of autoreactive effector T cell generation in islet autoimmunity and our data from mouse and human tissues suggest that they disappear once the destructive process has run its course. Thus, TLOs may be important for type 1 diabetes progression.

Modulating the foreign body response of implants for diabetes treatment

Diabetes Mellitus is a group of diseases characterized by high blood glucose levels due to patients' inability to produce sufficient insulin. Current interventions often require implants that can detect and correct high blood glucose levels with minimal patient intervention. However, these implantable technologies have not reached their full potential in vivo due to the foreign body response and subsequent development of fibrosis. Therefore, for long-term function of implants, modulating the initial immune response is crucial in preventing the activation and progression of the immune cascade. This review discusses the different molecular mechanisms and cellular interactions involved in the activation and progression of foreign body response (FBR) and fibrosis, specifically for implants used in diabetes. We also highlight the various strategies and techniques that have been used for immunomodulation and prevention of fibrosis. We investigate how these general strategies have been applied to implants used for the treatment of diabetes, offering insights on how these devices can be further modified to circumvent FBR and fibrosis.

Evaluating the Prognostic Value of Islet Autoantibody Monitoring in Islet Transplant Recipients with Long-Standing Type 1 Diabetes Mellitus

(1) Background: The correlation between titers of islet autoantibodies (IAbs) and the loss of transplanted islets remains controversial. We sought to evaluate the prognostic utility of monitoring IAbs in diabetic patients after islet transplantation (ITx); (2) Methods: Twelve patients with Type 1 diabetes mellitus and severe hypoglycemia underwent ITx. Serum concentration of glutamic acid decarboxylase (GAD), insulinoma antigen 2 (IA-2), and zinc transport 8 (ZnT8) autoantibodies was assessed before ITx and 0, 7, and 75 days and every 3 months post-operatively; (3) Results: IA-2A (IA-2 antibody) and ZnT8A (ZnT8 antibody) levels were not detectable before or after ITx in all patients (median follow-up of 53 months (range 24–61)). Prior to ITx, GAD antibody (GADA) was undetectable in 67% (8/12) of patients. Of those, 75% (6/8) converted to GADA+ after ITx. In 67% (4/6) of patients with GADA+ seroconversion, GADA level peaked within 3 months after ITx and subsequently declined. All patients with GADA+ seroconversion maintained long-term partial or complete islet function (insulin independence) after 1 or 2 ITx. There was no correlation between the presence of IAb-associated HLA haplotypes and the presence of IAbs before or after ITx; (4) Conclusions: There is no association between serum GADA trends and ITx outcomes. IA-2A and ZnT8A were not detectable in any of our patients before or after ITx.

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.

Impact of Pancreatic Autoantibodies in Pancreas Graft Survival After Pancreas-Kidney Transplantation

BACKGROUND

In simultaneous pancreas-kidney transplantation (SPKT), persistence or recurrence of pancreatic autoantibodies (PAs) has been associated with pancreas graft (PG) autoimmune-driven injury. Our aim was to analyze the impact of PAs on PG survival.

METHODS

Between January 1, 2000, and December 31, 2017, we studied 139 patients with post-SPKT anti-glutamic acid decarboxylase (GAD) autoantibody. Alloimmune (ALI) events were defined as PG rejection and/or de novo donor-specific antibodies (DSA). Hence, 3 groups were defined: patients without ALI events or anti-GAD (n = 42), those with ALI events (n = 14), or those only with autoimmune events (positive for anti-GAD and no ALI events; n = 83).

RESULTS

Male sex was predominant (n = 72, 52%). Median age was 35 years (interquartile range: 31-39) and median follow-up was 6-7 years (interquartile range: 4.1-9.2). Regarding anti-GAD positivity post-SPKT (n = 90, 65%), no differences were observed concerning age, sex, anti-HLA antibodies, HLA mismatch number and de novo DSA. ALI events were present in 10% (n = 14). PG survival 15 years post-SPKT was better in patients without immune events (96%) followed by those with ALI (69%) and autoimmune events (63%) (P = .025). Anti-GAD was associated to higher annualized mean Hb1AC (P = .006) and lower mean C-peptide (P = .013). According to pre- and post-SPKT anti-GAD status, conversion from negative to positive was associated to worse (63%) 10-year PG survival (P = .044), compared to persistence of negative (100%) or positive anti-GAD (88%). Anti-islet cell and anti-insulin autoantibodies had no impact.

CONCLUSION

Anti-GAD presence post-SPKT was associated to higher pancreas disfunction and lower PG survival. De novo anti-GAD seems to offer a particular risk of PG failure.

Bioinformatic analysis of peripheral blood RNA-sequencing sensitively detects the cause of late graft loss following overt hyperglycemia in pig-to-nonhuman primate islet xenotransplantation

Clinical islet transplantation has recently been a promising treatment option for intractable type 1 diabetes patients. Although early graft loss has been well studied and controlled, the mechanisms of late graft loss largely remains obscure. Since long-term islet graft survival had not been achieved in islet xenotransplantation, it has been impossible to explore the mechanism of late islet graft loss. Fortunately, recent advances where consistent long-term survival (≥6 months) of adult porcine islet grafts was achieved in five independent, diabetic nonhuman primates (NHPs) enabled us to investigate on the late graft loss. Regardless of the conventional immune monitoring methods applied in the post-transplant period, the initiation of late graft loss could rarely be detected before the overt graft loss observed via uncontrolled blood glucose level. Thus, we retrospectively analyzed the gene expression profiles in 2 rhesus monkey recipients using peripheral blood RNA-sequencing (RNA-seq) data to find out the potential cause(s) of late graft loss. Bioinformatic analyses showed that highly relevant immunological pathways were activated in the animal which experienced late graft failure. Further connectivity analyses revealed that the activation of T cell signaling pathways was the most prominent, suggesting that T cell-mediated graft rejection could be the cause of the late-phase islet loss. Indeed, the porcine islets in the biopsied monkey liver samples were heavily infiltrated with CD3+ T cells. Furthermore, hypothesis test using a computational experiment reinforced our conclusion. Taken together, we suggest that bioinformatics analyses with peripheral blood RNA-seq could unveil the cause of insidious late islet graft loss.

Autoimmune Diabetes Recurrence After Pancreas Transplantation: Diagnosis, Management, and Literature Review

Background

Pancreas transplantation can be a viable treatment option for patients with type 1 diabetes mellitus (T1DM), especially for those who are candidates for kidney transplantation. T1DM may rarely recur after pancreas transplantation, causing the loss of pancreatic graft. The aim of this study was to describe the prevalence of T1DM recurrence after pancreas transplantation in our series.

Material/Methods

Eighty-one patients transplanted from 2002 to 2015 were included. Autoantibody testing (GADA and IA-2) was performed before pancreas transplantation and during the follow-up.

Results

The series includes 48 males and 33 females, mean age 37.4±5.7 years and mean duration of diabetes 25.5±6.5 years. Patients received simultaneous pancreas kidney (SPK) transplantation. After SPK transplantation, 56 patients retained pancreatic graft, 8 patients died, and 17 patients lost their pancreatic graft. T1DM recurrence occurred in 2 of the 81 transplanted patients, yielding a prevalence of 2.5%, with an average time of appearance of 3.3 years after transplant. Pancreatic enzymes were normal in the 2 patients, ruling out pancreatic rejection. T1DM recurrence was confirmed histologically, showing selective lymphoid infiltration of the pancreatic islets.

Conclusions

T1DM recurrence after pancreas transplantation is infrequent; however, it is one of the causes of pancreatic graft loss that should always be ruled out. Negative autoimmunity prior to transplantation does not ensure that T1DM does not recur.

Pharmacological Targeting of GLUT1 to Control Autoreactive T Cell Responses

An increasing body of evidence indicates that bio-energetic metabolism of T cells can be manipulated to control T cell responses. This potentially finds a field of application in the control of the T cell responses in autoimmune diseases, including in type 1 diabetes (T1D). Of the possible metabolic targets, Glut1 gained considerable interest because of its pivotal role in glucose uptake to fuel glycolysis in activated T cells, and the recent development of a novel class of small molecules that act as selective inhibitor of Glut1. We believe we can foresee a possible application of pharmacological Glut1 blockade approach to control autoreactive T cells that destroy insulin producing beta cells. However, Glut1 is expressed in a broad range of cells in the body and off-target and side effect are possible complications. Moreover, the duration of the treatment and the age of patients are critical aspects that need to be addressed to reduce toxicity. In this paper, we will review recent literature to determine whether it is possible to design a pharmacological Glut1 blocking strategy and how to apply this to autoimmunity in T1D.

Immune Response to Extracellular Vesicles From Human Islets of Langerhans in Patients With Type 1 Diabetes

The autoimmune response that characterizes type 1 diabetes (T1D) has no clear cause. Extracellular vesicles (EVs) play an important role in triggering the immune response in other contexts. Here, we propose a model by which EVs isolated from human islets stimulate proinflammatory immune responses and lead to peripheral blood mononuclear cell (PBMC) activation. We show that human islet EVs are internalized by monocytes and B cells and lead to an increase in T-helper 1, 2, and 17 cytokine expression, as well as T and B cell proliferation. Importantly, we demonstrate memory T and B cell activation by EVs selectively in PBMCs of patients with T1D. Additionally, human islet EVs induce an increase in antibodies against glutamic acid decarboxylase 65 (GAD65) in T1D PBMCs. Furthermore, pretreatment of T1D PBMCs with ibrutinib, an inhibitor of Bruton tyrosine kinase, dampens EV-induced memory B cell activation and GAD65 antibody production. Collectively, our findings indicate a role for human islet EVs in mediating activation of B and T cells and GAD65 autoantibody production.

Regenerative Medicine and Diabetes: Targeting the Extracellular Matrix Beyond the Stem Cell Approach and Encapsulation Technology

According to the Juvenile Diabetes Research Foundation (JDRF), almost 1. 25 million people in the United States (US) have type 1 diabetes, which makes them dependent on insulin injections. Nationwide, type 2 diabetes rates have nearly doubled in the past 20 years resulting in more than 29 million American adults with diabetes and another 86 million in a pre-diabetic state. The International Diabetes Ferderation (IDF) has estimated that there will be almost 650 million adult diabetic patients worldwide at the end of the next 20 years (excluding patients over the age of 80). At this time, pancreas transplantation is the only available cure for selected patients, but it is offered only to a small percentage of them due to organ shortage and the risks linked to immunosuppressive regimes. Currently, exogenous insulin therapy is still considered to be the gold standard when managing diabetes, though stem cell biology is recognized as one of the most promising strategies for restoring endocrine pancreatic function. However, many issues remain to be solved, and there are currently no recognized treatments for diabetes based on stem cells. In addition to stem cell resesarch, several β-cell substitutive therapies have been explored in the recent era, including the use of acellular extracellular matrix scaffolding as a template for cellular seeding, thus providing an empty template to be repopulated with β-cells. Although this bioengineering approach still has to overcome important hurdles in regards to clinical application (including the origin of insulin producing cells as well as immune-related limitations), it could theoretically provide an inexhaustible source of bio-engineered pancreases.

Caerulomycin A suppresses the differentiation of naïve T cells and alleviates the symptoms of experimental autoimmune encephalomyelitis

Multiple sclerosis (MS) is a highly detrimental autoimmune disease of the central nervous system. There is no cure for it but the treatment typically focuses on subsiding severity and recurrence of the disease. Experimental autoimmune encephalomyelitis (EAE) is an animal model of MS. It is characterized by frequent relapses due to the generation of memory T cells. Caerulomycin A (CaeA) is known to suppress the Th1 cells, Th2 cells, and Th17 cells. Interestingly, it enhances the generation of regulatory T cells (Tregs). Th1 cells and Th17 cells are known to aggravate EAE, whereas Tregs suppress the disease symptoms. Consequently, in the current study we evaluated the influence of CaeA on EAE. Intriguingly, we observed by whole body imaging that CaeA regressed the clinical symptoms of EAE. Further, there was reduction in the pool of Th1 cells, Th17 cells, and CD8 T cells. The mechanism involved in suppressing the EAE symptoms was due to the inhibition in the generation of effector and central memory T cells and induction of the expansion of Tregs. In essence, these findings implicate that CaeA may be considered as a potent future immunosuppressive drug.

Assessment of Immune Isolation of Allogeneic Mouse Pancreatic Progenitor Cells by a Macroencapsulation Device

BACKGROUND

Embryonic stem cell (ESC)-derived β cells hold the promise of providing a renewable source of tissue for the treatment of insulin-dependent diabetes. Encapsulation may allow ESC-derived β cells to be transplanted without immunosuppression, thus enabling wider application of this therapy.

METHODS

In this study, we investigated the immunogenicity of mouse pancreatic progenitor cells and efficacy of a new macroencapsulation device in protecting these cells against alloimmune and autoimmune responses in mouse models.

RESULTS

Mouse pancreatic progenitor cells activated the indirect but not the direct pathway of alloimmune response and were promptly rejected in immune competent hosts. The new macroencapsulation device abolished T cell activation induced by allogeneic splenocytes and protected allogeneic MIN6 β cells and pancreatic progenitors from rejection even in presensitized recipients. In addition, the device was effective in protecting MIN6 cells in spontaneously diabetic nonobese diabetic recipients against both alloimmune and recurring autoimmune responses.

CONCLUSIONS

Our results demonstrate that macroencapsulation can effectively prevent immune sensing and rejection of allogeneic pancreatic progenitor cells in fully sensitized and autoimmune hosts.

The Effect of Corticosteroid Withdrawal on Glucose Metabolism and Anti-GAD Antibodies in Simultaneous Pancreas-Kidney Transplant Patients

CONTEXT

Corticosteroid withdrawal may reduce insulin resistance; however, it could also influence pancreatic autoantibody profile in simultaneous pancreas-kidney (SPK) transplant patients.

OBJECTIVE

To evaluate the effect of corticosteroid withdrawal on glucose metabolism and anti-glutamic acid decarboxylase (GAD) antibody titers in SPK patients with type 1 diabetes after 12 months of follow-up.

DESIGN

In this retrospective study, fasting glucose and glycated hemoglobin (A1c) were compared before and after 3, 6, and 12 months of corticosteroid withdrawal in 80 SPK patients. In addition, weight, anti-GAD, and C-peptide levels were compared before and after withdrawal. Finally, fasting and postglucose, insulin, and C-peptide levels were compared before and after withdrawal in 25 patients undergoing oral glucose tolerance test (OGTT).

RESULTS

Fasting glucose levels did not change during corticosteroid discontinuation. After 12 months, A1c slightly increased from 4.6% (0.4%) to 4.8% (0.6%) (P < .01) and C-peptide decreased from 2.8 (1.1) ng/mL to 2.4 (1.3) ng/mL (P <. 01). In patients submitted to OGTT, glucose, insulin, and C-peptide levels did not change. There was no alteration in the proportion of anti-GAD positive tests (41% vs 45%). Anti-GAD titers remained stable or decreased in 70% of positive patients.

CONCLUSION

Corticosteroid withdrawal has no significant effect on glucose metabolism and on anti-GAD profile among SPK patients.

Skin deep: from dermal fibroblasts to pancreatic beta cells

Type I diabetes (T1D) is a chronic autoimmune disease caused by pancreatic β-cell destruction induced by autoantibodies and autoreactive T cells. After significant reduction of the β-cell mass, diabetes sets in and can cause significant complications. It is estimated that more than 3 million Americans have T1D, and its prevalence among young individuals is progressively rising; however, the reasons for this increase are not known. Islet transplantation is recognized as the ultimate cure for T1D, but unfortunately, the severe scarcity of available islets makes it necessary to establish alternative sources of β-cells. Our lab seeks to establish human-induced pluripotent stem cells as an unlimited, novel source of insulin-producing cells (IPCs) that are patient-specific, obviating the requirement for immunosuppression. Although several reports have emerged demonstrating successful derivation of IPCs from human pluripotent stem cells, the efficiencies of derivation are inadequate and these IPCs do not respond to glucose stimulation in vitro. We reasoned that the use of a growth factor sequestering bioscaffold and promotion of cell-cell signaling through 3D clustering would enhance the generation of functionally superior IPCs compared to those derived by 2D differentiation. Here, we discuss a novel 3D platform for the generation of highly efficient human IPCs.

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.

Autoimmune diabetes recurrence should be routinely monitored after pancreas transplantation

Autoimmune type 1 diabetes recurrence in pancreas grafts was first described 30 years ago, but it is not yet completely understood. In fact, the number of transplants affected and possibly lost due to this disease may be falsely low. There may be insufficient awareness to this entity by clinicians, leading to underdiagnosis. Some authors estimate that half of the immunological losses in pancreas transplantation are due to autoimmunity. Pancreas biopsy is the gold standard for the definitive diagnosis. However, as an invasive procedure, it is not the ideal approach to screen the disease. Pancreatic autoantibodies which may be detected early before graft dysfunction, when searched for, are probably the best initial tool to establish the diagnosis. The purpose of this review is to revisit the autoimmune aspects of type 1 diabetes and to analyse data about the identified autoantibodies, as serological markers of the disease. Therapeutic strategies used to control the disease, though with unsatisfactory results, are also addressed. In addition, the author’s own experience with the prospective monitoring of pancreatic autoantibodies after transplantation and its correlation with graft outcome will be discussed.

Salivary proteins associated with hyperglycemia in diabetes: a proteomic analysis

Effective monitoring of glucose levels is necessary for patients to achieve greater control over their diabetes. However, only about a quarter of subjects with diabetes who requires close serum glucose monitoring, regularly check their serum glucose daily. One of the potential barriers to patient compliance is the blood sampling requirement. Saliva and its protein contents can be altered in subjects with diabetes, possibly due to changes in glycemic control. We propose here that salivary proteomes of subjects with diabetes may be different based on their glycemic control as reflected in A1C levels. A total of 153 subjects with type 1 or 2 diabetes were recruited. Subjects in each type of diabetes were divided into 5 groups based on their A1C levels; <7, 7-8, 8-9, 9-10, >10. To examine the global proteomic changes associated with A1C, the proteomic profiling of pooled saliva samples from each group was created using label-free quantitative proteomics. Similar proteomic analysis for individual subjects (N=4, for each group) were then applied to examine proteins that may be less abundant in pooled samples. Principle component analysis (PCA) and cluster analysis (p<0.01 and p<0.001) were used to define the proteomic differences. We, therefore, defined the salivary proteomic changes associated with A1C changes. This study demonstrates that differences exist between salivary proteomic profiles in subjects with diabetes based on the A1C levels.

Pancreatic autoantibodies after pancreas-kidney transplantation - do they matter?

Type 1 diabetes recurrence has been documented in simultaneous pancreas-kidney transplants (SPKT), but this diagnosis may be underestimated. Antibody monitoring is the most simple, noninvasive, screening test for pancreas autoimmune activity. However, the impact of the positive autoimmune markers on pancreas graft function remains controversial. In our cohort of 105 SPKT, we studied the cases with positive pancreatic autoantibodies. They were immunosuppressed with antithymocyte globulin, tacrolimus, mycophenolate, and steroids. The persistence or reappearance of these autoantibodies after SPKT and factors associated with their evolution and with graft outcome were analyzed. Pancreatic autoantibodies were prospectively monitored. Serum samples were collected before transplantation and at least once per year thereafter. At the end of the follow-up (maximum 138 months), 43.8% of patients were positive (from pre-transplant or after recurrence) for at least one autoantibody - the positive group. Antiglutamic acid decarboxylase was the most prevalent (31.4%), followed by anti-insulin (8.6%) and anti-islet cell autoantibodies (3.8%). Bivariate analysis showed that the positive group had higher fasting glucose, higher glycated hemoglobin (HbA1c), lower C-peptide levels, and a higher number of HLA-matches. Analyzing the sample divided into four groups according to pre-/post-transplant autoantibodies profile, the negative/positive group tended to present the higher HbA1c values. Multivariate analysis confirmed the significant association between pancreas autoimmunity and HbA1c and C-peptide levels. Positivity for these autoantibodies pre-transplantation did not influence pancreas survival. The unfavorable glycemic profile observed in the autoantibody-positive SPKT is a matter of concern, which deserves further attention.

Extracellular Matrix Scaffold Technology for Bioartificial Pancreas Engineering: State of the Art and Future Challenges

Emergent technologies in regenerative medicine may soon overcome the limitations of conventional diabetes therapies. Collaborative efforts across the subfields of stem cell technology, islet encapsulation, and biomaterial carriers seek to produce a bioengineered pancreas capable of restoring endocrine function in patients with insulin-dependent diabetes. These technologies rely on a robust understanding of the extracellular matrix (ECM), the supportive 3-dimensional network of proteins necessary for cellular attachment, proliferation, and differentiation. Although these functions can be partially approximated by biosynthetic carriers, novel decellularization protocols have allowed researchers to discover the advantages afforded by the native pancreatic ECM. The native ECM has proven to be an optimal platform for recellularization and whole-organ pancreas bioengineering, an exciting new field with the potential to resolve the dire shortage of transplantable organs. This review seeks to contextualize recent findings, discuss current research goals, and identify future challenges of regenerative medicine as it applies to diabetes management.

Pretransplantation GAD-autoantibody status to guide prophylactic antibody induction therapy in simultaneous pancreas and kidney transplantation

BACKGROUND

Daclizumab and antithymocyte globulin (ATG) have been shown to reduce allograft rejection. We assessed the safety and efficacy of daclizumab or ATG prophylaxis in combination with triple immunotherapy in simultaneous pancreas-kidney transplant (SPKT) recipients.

METHODS

Thirty-nine type 1 diabetic patients scheduled for primary SPKT were randomized to receive prophylactic therapy with either daclizumab or ATG. A group of 27 patients without prophylactic antibodies was used for retrospective comparison. All patients received cyclosporine and mycophenolate mofetil and gradually tapered prednisone. Autoantibodies and cellular autoreactivity were measured to assess recurrent autoreactive responses.

RESULTS

Baseline and transplant characteristics were comparable among groups. Both daclizumab and ATG therapy resulted in a significant reduction in acute rejection episodes. The incidence of rejection episodes was significantly higher in pretransplantation GAD autoantibody-positive daclizumab-treated recipients compared with GAD autoantibody-negative or ATG-treated recipients. IA-2 islet autoantibodies showed no association with rejection. There were no significant differences between the groups for in vitro autoreactivity, clinical outcome, or functional parameters.

CONCLUSIONS

Daclizumab or ATG combined with a maintenance immunosuppressive regime consisting of cyclosporine, mycophenolate mofetil, and prednisolone were well tolerated and equally effective in reducing the incidence of acute rejection episodes in SPKT recipients. Up to 3 years, no adverse sequelae of the immunoprophylaxis or clinical and ex vivo recurrent autoimmunity were observed. We propose that the pretransplantation existence of GAD65 autoantibodies serves as a marker guiding the choice for prophylactic therapy in pancreas transplantation.

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.

Transplantation of the pancreas

Pancreas transplantation consistently induces insulin-independence in beta-cell-penic diabetic patients, but at the cost of major surgery and life-long immunosuppression. One year after grafting, patient survival rate now exceeds 95 % across recipient categories, while insulin independence is maintained in some 85 % of simultaneous pancreas and kidney recipients and in nearly 80 % of solitary pancreas transplant recipients. The half-life of the pancreas graft currently averages 16.7 years, being the longest among extrarenal grafts, and substantially matching the one of renal grafts from deceased donors. The difference between expected (100 %) and actual insulin-independence rate is mostly explained by technical failure in the postoperative phase, and rejection in the long-term period. Death with a functioning graft remains a further major issue, especially in uremic patients who have undergone prolonged periods of dialysis. Refinements in graft preservation, surgical techniques, immunosuppression, and prophylactic treatments are expected to further improve the results of pancreas transplantation.

T cell autoreactivity in the transplant milieu

Autoreactive T cell responses in autoimmune disease are directed to tissue antigens but differ from allospecific T cells in several important respects, reflecting the circumstances of their selection, activation and expansion in vivo. Both genetic and acquired traits conspire to generate autoreactive effector cells that are refractory to normal control mechanisms, resulting in persistent and deleterious immunity to tissue antigens. When these same tissue antigens are reintroduced into an autoimmune setting, such as with pancreas or islet transplantation into a type 1 diabetic individual, the potential for recurrent activation of the underlying effector memory response presents a therapeutic challenge.