Comparison of Sirolimus Alone With Sirolimus Plus Tacrolimus in Type 1 Diabetic Recipients of Cultured Islet Cell Grafts

Autoreactive T cell profiles are altered following allogeneic islet transplantation with alemtuzumab induction and re-emerging phenotype is associated with graft function

Islet transplantation is an effective therapy for life-threatening hypoglycemia, but graft function gradually declines over time in many recipients. We characterized islet-specific T cells in recipients within an islet transplant program favoring alemtuzumab (ATZ) lymphodepleting induction and examined associations with graft function. Fifty-eight recipients were studied: 23 pretransplant and 40 posttransplant (including 5 with pretransplant phenotyping). The proportion with islet-specific T cell responses was not significantly different over time (pre-Tx: 59%; 1-6 m posttransplant: 38%; 7-12 m: 44%; 13-24 m: 47%; and >24 m: 45%). However, phenotype shifted significantly, with IFN-γ-dominated response in the pretransplant group replaced by IL-10-dominated response in the 1-6 m posttransplant group, reverting to predominantly IFN-γ-oriented response in the >24 m group. Clustering analysis of posttransplant responses revealed two main agglomerations, characterized by IFN-γ and IL-10 phenotypes, respectively. IL-10-oriented posttransplant response was associated with relatively low graft function. Recipients within the IL-10⁺ cluster had a significant decline in C-peptide levels in the period preceding the IL-10 response, but stable graft function following the response. In contrast, an IFN-γ response was associated with subsequently decreased C-peptide. Islet transplantation favoring ATZ induction is associated with an initial altered islet-specific T cell phenotype but reversion toward pretransplant profiles over time. Posttransplant autoreactive T cell phenotype may be a predictor of subsequent graft function.

Treatment with Tacrolimus and Sirolimus Reveals No Additional Adverse Effects on Human Islets In Vitro Compared to Each Drug Alone but They Are Reduced by Adding Glucocorticoids

Tacrolimus and sirolimus are important immunosuppressive drugs used in human islet transplantation; however, they are linked to detrimental effects on islets and reduction of long-term graft function. Few studies investigate the direct effects of these drugs combined in parallel with single drug exposure. Human islets were treated with or without tacrolimus (30 μg/L), sirolimus (30 μg/L), or a combination thereof for 24 hrs. Islet function as well as apoptosis was assessed by glucose-stimulated insulin secretion (GSIS) and Cell Death ELISA. Proinflammatory cytokines were analysed by qRT-PCR and Bio-Plex. Islets exposed to the combination of sirolimus and tacrolimus were treated with or without methylprednisolone (1000 μg/L) and the expression of the proinflammatory cytokines was investigated. We found the following: (i) No additive reduction in function and viability in islets existed when tacrolimus and sirolimus were combined compared to the single drug. (ii) Increased expression of proinflammatory cytokines mRNA and protein levels in islets took place. (iii) Methylprednisolone significantly decreased the proinflammatory response in islets induced by the drug combination. Although human islets are prone to direct toxic effect of tacrolimus and sirolimus, we found no additive effects of the drug combination. Short-term exposure of glucocorticoids could effectively reduce the proinflammatory response in human islets induced by the combination of tacrolimus and sirolimus.

Calcineurin inhibitor-free immunosuppressive regimen in type 1 diabetes patients receiving islet transplantation: single-group phase 1/2 trial

BACKGROUND

Our final objective is to develop an adoptive therapy with tolerogenic donor-specific type 1 T regulatory cells for patients with type 1 diabetes undergoing islet transplantation. The achievement of this objective depends on the availability of an immunosuppressive treatment compatible with the survival, function, and expansion of type 1 T regulatory cells.

METHODS

For this purpose, we designed a single-group, phase 1 to 2 trial with an immunosuppression protocol including: (i) rapamycin treatment before the first islet infusion (starting ≥ 30 days before transplantation); (ii) induction therapy with anti-thymocyte globulin (ATG) instead of anti-interleukin-2Ra monoclonal antibody (after the first islet infusion only); (iii) short-term treatment with steroids and interleukin-1Ra (right before and for 2 weeks after each infusion); rapamycin+mycophenolate mofetil treatment as maintenance therapy. The target enrollment was 10 patients.

RESULTS

Ten of 15 patients who started the pretransplant rapamycin treatment completed it. Nine of 10 patients did not complete the induction therapy with ATG, and three of 10 required adaptation of maintenance immunosuppression caused by side effects. Four of 10 patients acquired insulin independence which can be maintained up to year 3 after last infusion. All six other patients have lost their graft, and the early graft loss was associated with lower dose of ATG during induction.

CONCLUSION

This protocol resulted feasible, safe but less efficient in maintaining graft survival during the time than other T-cell depletion-based protocols. An adequate induction at the first infusion should be considered to improve the overall clinical outcome.

Early alteration of kidney function in nonuremic type 1 diabetic islet transplant recipients under tacrolimus-mycophenolate therapy

BACKGROUND

Transplant patients on tacrolimus therapy exhibit a reduced glomerular filtration rate (GFR). The type of graft and immune treatment protocol may influence the extent and reversibility of this side effect.

METHODS

The present single-center study is conducted in 48 nonuremic type 1 diabetic recipients of an intraportal islet-cell graft under maintenance immunosuppression (IS) with tacrolimus and mycophenolate mofetil. Estimated GFR (eGFR) and albuminuria were followed up to 5 years posttransplantation.

RESULTS

Mean eGFR values decreased by 19 mL/min/1.73 m after 1 to 2 weeks of IS (P<0.0001) and then remained stable throughout the complete treatment period. The decrease was related to predose trough tacrolimus concentrations or doses and disappeared upon its discontinuation; it was also associated with the presence of albuminuria at the time of transplantation. Tacrolimus treatment resulted in a reduction of albuminuria; its discontinuation restored albuminuria to the initial levels.

CONCLUSIONS

The use of tacrolimus in our islet-cell transplant protocol caused an initial 20% reduction in eGFR, which was reversible following its discontinuation, at least within the 5-year follow-up period. The associated reduction in albuminuria was also reversible, compatible with a tacrolimus-induced preglomerular vasoconstriction. These observations support further use of our tacrolimus regimen in this patient population.

Five-year follow-up of patients with type 1 diabetes transplanted with allogeneic islets: the UIC experience

This report summarizes a 5-year phase 1/2 allogeneic islet transplantation clinical trial conducted at the University of Illinois at Chicago (UIC). Ten patients were enrolled in this single center, open label, and prospective trial in which patients received 1-3 transplants. The first four subjects underwent islet transplantation with the Edmonton immunosuppressive regimen and the remaining six subjects received the UIC immunosuppressive protocol (Edmonton plus etanercept and exenatide). All 10 patients achieved insulin independence after 1-3 transplants. At 5 years of follow-up, 6 of the initial 10 patients were free of exogenous insulin. During the follow-up period, 7 of the 10 patients maintained positive C-peptide levels and a composite hypoglycemic score of 0. Most patients maintained HbA1c levels <6.0 % (42.1 mmol/mol) and a significantly improved β-score. In conclusion, this study demonstrated long-term islet graft function without using T cell depleting induction, with an encouraging outcome that includes 60 % of patients remaining insulin independent after 5 years of initial transplantation.

Predictive factors of allosensitization after immunosuppressant withdrawal in recipients of long-term cultured islet cell grafts

BACKGROUND

Islet transplantation has been reported to induce allosensitization in the majority of type 1 diabetic recipients of fresh or shortly incubated islet grafts prepared from one to three donors.

METHODS

We examined the appearance of human leukocyte antigen (HLA) antibodies after withdrawal of immunosuppressants in 35 type 1 diabetic recipients of islet cell grafts prepared from a median of 6 donors (range, 2-11), cultured for longer periods, and characterized for their cellular composition. Immunosuppression consisted of antithymocyte globulin induction followed by mycophenolate mofetil plus calcineurin inhibitors (n=28, with 7 also receiving steroids) or sirolimus with (n=3) or without calcineurin inhibitors (n=4). Both the complement-dependent cytotoxicity (CDC) assay (class I) and the solid-phase flow-based Luminex method (class I and II) were used to identify HLA antibodies.

RESULTS

Immunosuppressant withdrawal resulted in CDC positivity for class I antibodies in only 6% of patients. However, the majority became positive for class I antibodies (72%) or class II antibodies (72%) in the Luminex assay; positivity was not correlated to a higher number of donors or HLA mismatches, but with a lower β-cell purity; use of steroids reduced de novo positivity for Luminex class I antibodies.

CONCLUSION

Allosensitization to cultured human islet cell grafts was low when assessed by CDC assay but high in Luminex. No correlation was found with the number of donors but risk was higher for grafts with lower β-cell purity.

Effects of immunosuppression on alpha and beta cell renewal in transplanted mouse islets

AIMS/HYPOTHESIS

Immunosuppressive drugs used in human islet transplantation interfere with the balance between beta cell renewal and death, and thus may contribute to progressive graft dysfunction. We analysed the influence of immunosuppressants on the proliferation of transplanted alpha and beta cells after syngeneic islet transplantation in streptozotocin-induced diabetic mice.

METHODS

C57BL/6 diabetic mice were transplanted with syngeneic islets in the liver and simultaneously abdominally implanted with a mini-osmotic pump delivering BrdU alone or together with an immunosuppressant (tacrolimus, sirolimus, everolimus or mycophenolate mofetil [MMF]). Glycaemic control was assessed for 4 weeks. The area and proliferation of transplanted alpha and beta cells were subsequently quantified.

RESULTS

After 4 weeks, glycaemia was significantly higher in treated mice than in controls. Insulinaemia was significantly lower in mice treated with everolimus, tacrolimus and sirolimus. MMF was the only immunosuppressant that did not significantly reduce beta cell area or proliferation, albeit its levels were in a lower range than those used in clinical settings.

CONCLUSIONS/INTERPRETATION

After transplantation in diabetic mice, syngeneic beta cells have a strong capacity for self-renewal. In contrast to other immunosuppressants, MMF neither impaired beta cell proliferation nor adversely affected the fractional beta cell area. Although human beta cells are less prone to proliferate compared with rodent beta cells, the use of MMF may improve the long-term outcome of islet transplantation.

Biomarkers for immune intervention trials in type 1 diabetes

After many efforts to improve and standardize assays for detecting immune biomarkers in type 1 diabetes (T1D), methods to identify and monitor such correlates of insulitis are coming of age. The ultimate goal is to use these correlates to predict disease progression before onset and regression following therapeutic intervention, which would allow performing smaller and shorter pilot clinical trials with earlier endpoints than those offered by preserved β-cell function or improved glycemic control. Here, too, progress has been made. With the emerging insight that T1D represents a heterogeneous disease, the next challenge is to define patient subpopulations that qualify for personalized medicine or that should be enrolled for immune intervention, to maximize clinical benefit and decrease collateral damage by ineffective or even adverse immune therapeutics. This review discusses the current state of the art, setting the stage for future efforts to monitor disease heterogeneity, progression and therapeutic intervention in T1D.

Adverse events in clinical islet transplantation: one institutional experience

Islet transplantation is one of the most promising treatments for an unstable form of type 1 diabetes. However, islet transplantation still has some obstacles, such as low success rate of islet isolation, difficulty to obtain long-term insulin freedom, and adverse events related to transplant protocol. We describe the adverse events of current clinical islet transplantation at our institute in this report. Nine type 1 diabetic patients received 17 islet infusions from March 2005 to October 2008. The islet infusion procedure and immunosuppression regimen were based on a modified Edmonton protocol. Severe adverse events (SAEs) were defined as events that were more than grade 3 according to the Terminology Criteria for Adverse Events in Trials of Adult Pancreatic Islet Transplantation, version 4.1 (Collaborative Islet Transplant Registry, CITR). Sixteen events were reported as SAEs and among them 12 events were probably or definitely related to transplant protocols; all occurred within 1 year after infusion except for one. Five adverse events (31%) occurred within 10 days after transplantation and were related to infusion procedures. Seven events (44%) occurred after 50 days and were related to immunosuppressive therapy. SAEs related to the protocol included three events of elevated liver enzymes, two of hemorrhage into gall bladder or peritoneal cavity, two of neutropenia, two of infection, one of vomiting, one of diarrhea, and one of renal dysfunction. All events were grade 3, except for one case that was grade 4 of neutropenia. All SAEs resolved with no sequelae. Neoplasms and deaths were not observed in our study. The present study suggests need to improve both infusion procedure and immunosuppressive strategy from the view of preventing SAEs.

Rotational co-culture of clonal β-cells with endothelial cells: effect of PPAR-γ agonism in vitro on insulin and VEGF secretion

AIM

Delayed graft revascularization impedes the success of human islet transplantation. This study utilized rotational co-culture of insulin secreting β-cells with human umbilical vein endothelial cells (HUVECs) and a peroxisome proliferator-activated receptor gamma (PPAR-γ) agonist to promote insulin and vascular endothelial growth factor (VEGF) secretory function.

METHODS

Clonal BRIN-BD11 (D11) cells were maintained in static culture (SC) and rotational culture (RC) ± HUVEC and ± the TZD (thiazolidinedione) rosiglitazone (10 mmol/l) as a specific PPAR-γ agonist. HUVECs were cultured in SC and RC ± D11 and ± TZD. D11 insulin secretion was induced by static incubation with low glucose (1.67 mmol/l), high glucose (16.7 mmol/l) and high glucose with 10 mmol/l theophylline (G+T) and assessed by enzyme-linked immunosorbent assay (ELISA). HUVEC proliferation was determined by ATP luminescence, whereas VEGF secretion was quantified by ELISA. Co-cultured cells were characterized by immunostaining for insulin and CD31.

RESULTS

D11 SC and RC showed enhanced insulin secretion in response to 16.7 mmol/l and G+T (p < 0.01); without significant alteration by the TZD. Co-culture with HUVEC in SC and RC also increased D11 insulin secretion when challenged with 16.7 mmol/l and G+T (p < 0.01), and this was slightly enhanced by the TZD. The presence of HUVEC increased D11 SC and RC insulin secretion in response to high glucose and G+T, respectively (p < 0.01). Addition of the TZD increased SC and RC HUVEC ATP content (p < 0.01) and VEGF production (p < 0.01) in the presence and absence of D11 cells.

CONCLUSIONS

Rotational co-culture of insulin secreting cells with endothelial cells, and exposure to a PPAR-γ agonist may improve the prospects for graft revascularization and function after implantation.

Immune and cell therapy in type 1 diabetes: too little too late?

INTRODUCTION

Type 1 diabetes is caused by autoimmune destruction of insulin-producing β-cells. Intensive insulin therapy protects most patients against chronic complications of diabetes, but exposes patients to acute complications like hypoglycaemia and impacts on quality of life. Therapies that aim at protecting or restoring endogenous insulin secretion might help in decreasing the risk of severe hypoglycemia and long-term complications.

AREAS COVERED

This article reviews the literature of clinical immunotherapy and β-cell transplantation in treatment of type 1 diabetes with specific focus on the effect on preserving and restoring β-cell mass.

EXPERT OPINION

Several studies in recent-onset type 1 diabetic patients have provided proof of principle that immunotherapy can preserve residual functional β-cell mass. The observation that this strategy is most effective early in the disease process opens possibilities of arresting and even preventing type 1 diabetes. In patients with too few or no surviving β-cells, current protocols of β-cell transplantation can restore functional β-cell mass up to 25% of levels in healthy controls. Unfortunately, both strategies to date are followed by progressive decline of endogenous insulin secretion later on. Strategies to restore functional β-cell mass to a higher level and to restore immune tolerance are thus needed.

Upgrading pretransplant human islet culture technology requires human serum combined with media renewal

BACKGROUND.: The original Edmonton protocol used fresh islets, but for obvious logistic advantages most transplant centers have implemented pretransplant culture in human albumin. The aim of this study was to improve current pretransplant human islet culture techniques. METHODS.: Clinical-grade purified human islets from a total of 24 donors were directly resuspended after isolation in CMRL 1066-based media at 37 degrees C, and media additions and renewal were tested. At days 1 and 5 of culture, in vitro quality controls included islet viability, insulin content and function, apoptosis, and in vivo islet potency assay in nude mice. RESULTS.: Replacing human albumin with human AB serum improved 1- and 5-day preservation of islet function and viability which was further enhanced with antioxidant Stem Ease, leading to the iCulture medium (enriched CMRL: pyruvate, zinc sulfate, insulin, transferrin, selenium, 2.5% human AB serum and Stem Ease). Major damage occurs in the first day of culture and frequent media renewal (25% vol/hr) in this period further improved viability, apoptosis, islet recovery, and function in vitro and in vivo, compared with only changing medium after overnight culture. CONCLUSIONS.: The described human islet culture technique (iCulture medium+renewal) seems to be the best choice for clinical human islet culture when short (1 day) or long (5 days) periods are used. Media choice and dilution play a major role in the function and survival of human islets in culture.

Successes and disappointments with clinical islet transplantation

Transplantation of pancreatic islets is considered a therapeutic option for patients with type 1 diabetes mellitus who have life-threatening hypoglycaemic episodes. After the procedure, a decrease in the frequency and severity of hypoglycaemic episodes and sustained graft function as indicated by detectable levels of C-peptide can be seen in the majority of patients. However, true insulin independence, if achieved, usually lasts for at most a few years. Apart from the low insulin independence rates, reasons for concern regarding this procedure are the side effects of the immunosuppressive therapy, allo-immunization, and the high costs. Moreover, whether islet transplantation prevents the progression of diabetic micro- and macrovascular complications is largely unknown. Areas of current research include the development of less toxic immunosuppressive regimens, the control of the inflammatory reaction immediately after transplantation, the identification of the optimal anatomical site for islet infusion, and the possibility to encapsulate transplanted islets to protect them from the allo-immune response. At present, pancreatic islet transplantation is still an experimental procedure, which is only indicated for a highly selected group of type 1 diabetic patients with life-threatening hypoglycaemic episodes.

Neovascularization Induced around an Artificial Device Implanted in the Abdomen by the Use of Gelatinized Fibroblast Growth Factor 2

The development of a bioartificial pancreas (BAP) with immunoisolating fashion has been gaining attention as a new method for treating diabetes. We have been proceeding with the development of a bag-type BAP that can be easily implanted and that allows for the optional injection or rejection of cells at any time. If fibrosis develops around a BAP device, then the permeability of substances transmitted through a semipermeable membrane will decrease, thereby reducing the reactivity with glucose, so it is necessary for the material of the device to have an excellent histocompatibility. Furthermore, in order to improve the efficacy of BAP treatment, it is important to maintain an environment of ample blood flow around the device. We have created a bag-type device for BAP that is 20 × 20 mm in size and comprises two layers of membranes. We have used an EVAL membrane for the outer membrane of the two layers. The EVAL membrane is a semipermeable membrane with good insulin permeability, which functions as an immunoisolation membrane. The inner membrane consists of PAU-coated HD-PE (nonwoven material processed with polyaminourethan) and it is designed to function as a scaffold for cells. We used Lewis rats to determine whether the effectiveness of fibroblast growth factor 2 (bFGF) can be improved by concomitantly using bFGF with a capacity for blood vessel regeneration as well as bFGF immersed in a sheet of gelatin. We placed the BAP in the abdominal cavity and covered it with the greater omentum. We were able to significantly increase the blood flow and the number of new blood vessels in the tissue surrounding the BAP device by using gelatinized bFGF. There were only a few instances of fibrosis as a biological reaction to the EVAL membrane, and the infiltration of inflammatory cells was mild. There were no adverse effects related to implantation of the device. We confirmed in this study that the use of an implantable BAP device and bFGF allowed for a better blood flow around the BAP device. There were only minor instances of fibrosis and inflammation reaction around the BAP, thus indicating the BAP that we are currently developing to have an excellent histocompatibility.

Relevance of cytotoxic alloreactivity under different immunosuppressive regimens in clinical islet cell transplantation

Islet or beta cell transplantation provides a promising cure for type 1 diabetes patients, but insulin-independency decreases frequently over time. Immunosuppressive regimens are implemented attempting to cope with both auto- and alloimmunity after transplantation. We analysed the influence of different immunotherapies on autoreactive and alloreactive T cell patterns and transplant outcome. Patients receiving three different immunosuppressive regimens were analysed. All patients received anti-thymocyte globulin induction therapy. Twenty-one patients received tacrolimus-mycophenolate mofetil maintenance immunosuppression, whereas the other patients received tacrolimus-sirolimus (SIR, n = 5) or SIR only (n = 5). Cellular autoreactivity and alloreactivity (CTL precursor frequency) were measured ex vivo. Clinical outcome in the first 6 months after transplantation was correlated with immunological parameters. C-peptide levels were significantly different between the three groups studied (P = 0.01). We confirm that C-peptide production was correlated negatively with pretransplant cellular autoreactivity and low graft size (P = 0.001, P = 0.007 respectively). Combining all three therapies, cellular autoimmunity after transplantation was not associated with delayed insulin-independence or C-peptide production. In combined tacrolimus-SIR and SIR-treated patients, CTL alloreactivity was associated with less insulin independence and C-peptide production (P = 0.03). The percentage of donors to whom high CTLp frequencies were measured was lower in insulin-independent recipients (P = 0.03). In this cohort of islet cell graft recipients, clinical outcome in the first 6 months after transplantation correlates with the applied immunosuppressive regimen. An association exists between insulin-independence and lower incidence of CTL alloreactivity towards donor human leucocyte antigen. This observational study demonstrates the usefulness of monitoring T cell reactivity against islet allografts to correlate immune function with graft survival.

An update on preventive and regenerative therapies in diabetes mellitus

Type 1A (immune-mediated) and type 2 diabetes mellitus are two of the most common severe chronic illnesses, affecting over 230 million people worldwide with an estimated global prevalence of 5.1%. Although type 1 and type 2 diabetes differ greatly in modes of pathogenesis, these illnesses share a common pathology and consequences characterized by loss of functional beta-cell mass and subsequent dysregulation of carbohydrate and lipid metabolism. Since therapy for diabetes and the associated complications poses enormous public health and economic burdens, novel preventive and regenerative therapies have emerged in the past decade with the aim to preserve beta-cell mass and delay the onset of diabetes. The goal of this review is to provide a comprehensive overview of current efforts in the fight against diabetes, and attempts to document all strategies that have emerged in clinical studies within the past 25 years. First, strategies to identify individuals at risk, ranging from whole-genome scans to autoantibody screening, will be discussed. Second, novel approaches to prevent or delay the onset of disease will be covered. Particular focus is given on emerging strategies for individuals at risk for type 1 diabetes that target T-cell regulation and induction of tolerance, while new pharmaceutical concepts in combination with lifestyle interventions are discussed within the scope of type 2 diabetes prevention. Lastly, important efforts to halt disease progression with emphasis on beta-cell regeneration are presented.

Minimization and withdrawal of steroids in pancreas and islet transplantation

For reducing the corticosteroid (CS)-related side-effects, especially cardiovascular events, CS-sparing protocols have become increasingly common in pancreas transplantation (PT). Lympho-depleting induction antibodies, such as rabbit anti-thymocyte globulin (rATG) or alemtuzumab, have been widely used in successful trials. The results of various CS-sparing protocols combining calcineurin inhibitors (CNI) and mycophenolate or sirolimus, have been mixed for rejection and survival rates. Most of the studies were uncontrolled trials of low-risk patients, therefore the grade of evidence is limited. Large-scale prospective studies with long-term follow up are necessary to assess risks and benefits of CS-sparing regimens in PT before recommending such strategies as standard practice. Islet allo-transplantation for patients with brittle type 1 diabetes mellitus, less invasive and safer procedure than PT, has been attempted since late 1980s, but diabetogenic immunosuppressants at maintenance, mainly CS and high-dose CNI, prevented satisfactory results (10% insulin-independence at 1-year post-transplant). Since 2000, CS-free and CNI-reducing protocols, including more potent induction [daclizumab, OKT3gamma1(ala-ala) anti-CD3 antibody, rATG] and maintenance (sirolimus, mycophenolate) agents, have significantly improved short-term outcomes whereas long-term are still inadequate (from 80% to 20% insulin-independence from 1- to 5-year post-transplant). Main limitations are allo- and autoimmunity, immunosuppression-related islet and systemic toxicity and transplant site unsuitability, which tolerogenic protocols and biotechnological solutions may solve.

Rapamycin in islet transplantation: friend or foe?

The Edmonton protocol was undoubtedly a major step forward in the history of islet transplantation. Its immunosuppression regimen was largely based on the mTOR inhibitor rapamycin (sirolimus), which remains the most frequently used immunosuppressive drug in clinical islet transplant protocols. As time reveals the somewhat disappointing long-term results achieved with the Edmonton protocol, a number of publications have appeared addressing the potential beneficial or deleterious role of rapamycin on islet cell engraftment, function survival and regeneration, as well as on its side-effects in human subjects. This paper reviews the sometimes contradictory evidence on the impact of rapamycin in islet transplantation.

Current challenges in islet transplantation

Allogeneic islet transplantation is becoming a treatment option for patients with unstable type 1 diabetes mellitus (T1DM). Around 80% of the islet recipients achieve insulin independence after one or two islet infusions under "Edmonton-like" immunosuppressive protocol, but only 10% will remain insulin independent over the long term. Islet transplantation leads to glucose stabilization, and severe hypoglycemia is prevented even in patients back on insulin injections. Thus, islet transplantation has achieved the proposed targets in patients with unstable T1DM: normalizing blood glucose and hemoglobin A(1c), preventing severe hypoglycemic episodes, and improving quality of life. The current aims of islet transplantation programs are to maintain the success achieved and to overcome remaining obstacles and limitations.