Islet transplantation-immunological challenges and current perspectives

Pancreatic islet transplantation is a minimally invasive procedure aiming to reverse the effects of insulin deficiency in patients with type 1 diabetes(T1D)by transplanting pancreatic beta cells.Overall,pancreatic islet transplantation has improved to a great extent,and cellular replacement will likely become the mainstay treatment.We review pancreatic islet transplantation as a treatment for T1D and the immunological challenges faced.Published data demonstrated that the time for islet cell transfusion varied between 2 and 10 h.Approximately 54%of the patients gained insulin independence at the end of the first year,while only 20%remained insulin-free at the end of the second year.Eventually,most transplanted patients return to using some form of exogenous insulin within a few years after the transplantation,which imposed the need to improve immunological factors before transplantation.We also discuss the immunosuppressive regimens,apoptotic donor lymphocytes,anti-TIM-1 antibodies,mixed chimerism-based tolerance induction,induction of antigen-specific tolerance utilizing ethylene carbodiimide-fixed splenocytes,pretransplant infusions of donor apoptotic cells,B cell depletion,preconditioning of isolated islets,inducing local immunotolerance,cell encapsulation and immunoisolation,using of biomaterials,immunomodulatory cells,etc.

Islet transplantation for diabetic rats through the spleen

BACKGROUND: Islet transplantation is considered a po- tentially curative treatment for diabetic mellitus. The aim of this study was to assess the feasibility of islet transplant through the spleen. METHODS: Both donor and recipient Wistar rats (BW150± 20 g) were provided by the Animal Center of China Medi- cal University, Shenyang, China. Islets were isolated and purified with the modified Minnesota program. 600-800IE graft islets were handpicked and transplanted through the spleen of diabetic recipients. Blood glucose and insulin were evaluated after operation every other day. IVGTT was performed 10 days after transplantation. RESULTS: 300-400IE islet was procured from one donor rat. Secretion index (SI) of the glucose stress was 5.59± 0.62, showing the graft functioning well. The diabetic rats restored normal blood glucose levels of 3.4-5.4 mmol/L (mean 4.8 mmol/L). Their insulin levels were as normal as 8.5-12.2 μIU/ml. The K value of IVGTT in the rats after transplantation was similar to the normal one. CONCLUSIONS: The islets can be transplanted successfully through the spleen, while avoiding the complications caused by traditional transplantation through the portal vein, such as bleeding and portal vein hypertension. The graft islets loss can be reduced because of less centrifugation and mechanic pressure. In conclusion, transplantation through the spleen is a simple and feasible method.

Role of OX40 in mechanisms of memory T cells in islet transplant tolerance

Objective To investigate the role of OX40 in the mechanisms of memory T cells in islet transplant tolerance. Methods The expression of OX40 on native, like memory and memory CD8 + T cells was detected by RT - PCR. Splenic T ceels from B6 mice were injected into Rag - / - mice via the tail vein,and the Rag mice were divided into three groups ( n = 8 each) :

WJSC 6^(th) Anniversary Special Issues(2):Mesenchymal stem cells Mesenchymal stem cells help pancreatic islet transplantation to control type 1 diabetes

Islet cell transplantation has therapeutic potential to treat type 1 diabetes,which is characterized by autoimmune destruction of insulin-producing pancreatic isletβcells.It represents a minimal invasive approach forβcell replacement,but long-term blood control is still largely unachievable.This phenomenon can be attributed to the lack of islet vasculature and hypoxic environment in the immediate post-transplantation period that contributes to the acute loss of islets by ischemia.Moreover,graft failures continue to occur because of immunological rejection,despite the use of potent immunosuppressive agents.Mesenchymal stem cells(MSCs)have the potential to enhance islet transplantation by suppressing inflammatory damage and immune mediated rejection.In this review we discuss the impact of MSCs on islet transplantation and focus on the potential role of MSCs in protecting islet grafts from early graft failure and from autoimmune attack.

Pancreatic islet transplantation

Type 1 diabetes mellitus is an autoimmune disease,which results in the permanent destruction of β-cells of the pancreatic islets of Langerhans.While exogenous insulin therapy has dramatically improved the quality of life,chronic diabetic complications develop in a substantial proportion of subjects and these complications generally progress and worsen over time.Although intensive insulin therapy has proven effective to delay and sometimes prevent the progression of complications such as nephropathy,neuropathy or retinopathy,it is difficult to achieve and maintain long term in most subjects.Reasons for this diff iculty include compliance issues and the increased risk of severe hypoglycemic episodes,which are generally associated with intensification of exogenous insulin therapy.Clinical studies have shown that transplantation of pancreas or purified pancreatic islets can support glucose homeostasis in type 1 diabetic patients.Islet transplantation carries the special advantages of being less invasive and resulting in fewer complications compared with the traditional pancreas or pancreas-kidney transplantation.However,islet transplantation efforts have limitations including the short supply of donor pancreata,the paucity of experienced islet isolation teams,side effects of immunosuppressants and poor long-term results.The purpose of this article is to review recent progress in clinical islet transplantation for the treatment of diabetes.

Current status of clinical islet transplantation

Islet transplantation(IT) is today a well-established treatment modality for selected patients with type 1 diabetes mellitus(T1DM). After the success of the University of Alberta group with a modified approach to the immune protection of islets, the international experience grew along with the numbers of transplants in highly specialized centers. Yet, long-term analysis of those initial results from the Edmonton group indicated that insulin-independence was not durable and most patients return to modest amounts of insulin around the fifth year, without recurrent hypoglycemia events. Many phenomena have been identified as limiting factor for the islet engraftment and survival, and today all efforts are aimed to improve the quality of islets and their engrafting process, as well as more optimized immunosuppression to facilitate tolerance and ultimately, better long term survival. This brief overview presents recent progress in IT. A concise historical perspective is provided, along with the latest efforts to improve islet engraftment, immune protection and ultimately, prolonged graft survival. It is apparent that as the community continues to work together further optimizing IT, it is hopeful a cure for T1 DM will soon be achievable.

Protective effect of glucocorticoid-free immunosuppressive regimen in allogenic islet transplantation

BACKGROUND: The most common complication after allogenic islet transplantation is rejection. This study was to evaluate the effect of anti-rejection of glucocorticoid-free immunosuppressive regimen on allogenic islet transplantation. METHODS: Tacrolimus(FK506)+mycophenolate mofetil (MMF) and FK506+MMF+prednisone (Pred) were administered respectively for 2 weeks to inhibit rejection after allogenic islet transplantation in rats, which were compared with the control group. The concentrations of blood glucose, insulin and C-peptide were determined dynamically in recipients and the sites of transplantation were observed morphologically. RESULTS: As compared with the control group without immunosuppressive agents, FK506+MMF and FK506+MMF+Pred could prolong the survival time of grafts significantly. There were many morphologically intact islets in the liver of recipients 2 months after transplantation. Group FK506+MMF kept normal levels of blood glucose, insulin and C-peptide beyond 60 days after transplantation. In contrast, group FK506+MMF+Pred secreted less C-peptide(P<0.05) and maintained a higher level of blood glucose concentration (P<0.01) after the operation. There was no significant difference in insulin concentrations between the two groups. The level of blood glucose beyond the first 2 weeks after drug withdrawal in group FK506+MMF+Pred decreased obviously (P<0.05), and the secretion of insulin and C-peptide increased. These results were compared with those the first 2 weeks after transplantation and the first 2 weeks after drug withdrawal. CONCLUSIONS: Both regimens of FK506+MMF and FK506+MMF+Pred could provide effective immunosup-pression. Moreover the combined glucocorticoid-free immunosuppressive strategy of low-dose FK506 and MMF could protect islet grafts in islet transplantation without diabetogenic side-effects.

Islet transplantation in multicenter networks:the GRAGIL example

Purpose of review The enthusiasm generated by the results of the Edmonton protocol of islet transplantation is inciting a great number of institutions to start such programs.However,the procedure of islet isolation and purification is costly,complex and technically challenging.In order to share costs and to avoid facing the steep learning curve of the procedure,many centers interested in islet transplantation have looked into collaborating with experienced groups serving as core islet isolation facilities.Recent findings The proof of principle that remote islet processing and shipment could be successfully implemented with obtainng the Portland/Minneapolis,Huddinge/Giessen and Houston/Miami partnerships.Moreover,in order to increase both the donor pool and the number of patients gaining access to islet transplantation,multicenter networks,such as the Swiss-French GRAGIL consortium and the 4-country Nordic Network in Scandinavia have been built.The GRAGIL group has been fully operational since 1999,allowing the transplantation of 27 islet preparations processed in Geneva,Switzerland into 20 recipients in France over the course of 4.5 years.Organizational issues in the design of such networks are discussed based on the example of the GRAGIL experience.Summary The feasibility and the efficiency of islet transplantation in multicenter networks have been demonstrated.This strategy allows to increase the donor pool and the accessibility to islet transplantation in an extended population area.(J Intervent Radiol,2006,15: 626-631)

Immunosuppressive therapy in pancreas and islet transplant: Need for simultaneous assessment of insulin sensitivity and secretion

Diabetes mellitus is a metabolic disease possible to treat via pancreas/islet transplantation but most immunosuppressive drugs are diabetogenic. In this letter, we review current up to date methods to assess insulin action and secretion (using the surrogate indexes) suggesting their use in large studies in populations of pancreas/ islets transplanted patients.

Encapsulated islet transplantation for patients with type 1 diabetes mellitus

在过去的30多年间,为了改善胰岛移植的治疗效果和避免使用免疫抑制剂带来的不良反应,研究者们致力于微囊化胰岛移植技术的研究。随着许多胰岛封装系统的发展,胰岛微囊化被广泛地研究。在不同动物模型中包括非人灵长类动物,验证了各种微囊材料,其中一些材料能在没有免疫抑制的情况下起到保护胰岛的功能。虽然微囊化胰岛移植在NHP模型中取得了初步成功,但是在临床试验尚未成功。本文包括两部分内容:简要概述微囊化胰岛移植作为1型糖尿病患者的治疗方法,及目前遇到的挑战和未来展望。

Development of microfluidic devices for islet transplantation and islet physiologys

本文讨论了芝加哥伊利诺伊大学研发的几种用于人胰岛生理和病理生理学研究的微流体装置及其在人胰岛移植中的应用。首先介绍了作为l型糖尿病临床治疗的胰岛移植领域关键问题。随后,回顾了可以解决这些关键问题的微流体装置、每一种微流体装置的独特之处及他们的应用。此外,本文也简单地讨论了芝加哥伊利诺伊大学这几种微流体装置的设计和制造原理。

The establishment of pancreatic islet isolation in India-an update on human pancreatic islet transplantation

Background:Diabetes is a widespread disease with increasing prevalence.Transplantation of islets of Langerhans is a viable treatment for a selected group of patients with repeated hypoglycemic episodes in type 1 diabetes.The countries where islet transplantation has not been explored suffer from insufficient knowledge concerning key elements of the isolation process.Donor and organ procurement parameters impact human islet yield,although for research purposes,islet yield may be secondary in importance to islet function.This paper will analyze the feasibility of research-only human islet isolation and signify parameters underlying a successful yield in the Indian population.This eventually can make islet transplantation a clinical reality in India.Method:After receiving the consent for procuring brain-dead pancreas from the first-degree of relatives,samples were collected and transported in a transportation buffer at 4℃.The procedure consists of a mechanically enhanced enzymatic digestion of the pancreas,after which it was taken for purification using Ficoll method,followed by islet quality testing.Results:Through 15 isolations done over a span of approximately 2 years during the COVID pandemic in India,we confirm that ischemic time and glycated hemoglobin,each have a negative impact on isolation purity and yield.Notably,extending cold ischemic tim beyond the typical clinical isolation cutoff of 12 hours(to≥18 h)had a huge impact on islet function and yield.Age had a negative correlation with islet yield;however other biological parameters(specifically body mass index)and isolation variables appear to make a significant contribution to the heterogeneity of human islet yield.Our current work demonstrates the feasibility of extending acceptable cold ischemic time for research-focused human islet isolation and highlights the biological variation in isolation of human islets from donors with and without diabetes.Conclusion:India requires establishment of an islet transplant program using the current standard methods of“islet isolation”and donor program and process.Research should focus on improving standards in the islet preparation process to increase the number of successful preparations,shorten the isolation time,and increase patient safety so that the theoretical risk involved can become a practical reality.

Effects of mycophenolate mofetil vs cyclosporine administration on graft survival and function after islet allotransplantation in diabetic rats

AIM: To develop an experimental model of islet allotransplantation in diabetic rats and to determine the positive or adverse effects of MMF as a single agent. METHODS: Thirty-six male Wistar rats and 18 male Lewis rats were used as recipients and donors respectively. Diabetes was induced by the use of streptozotocin (60 mg/kg) intraperitoneally. Unpurified islets were isolated using the collagenase digestion technique and transplanted into the splenic parenchyma. The recipients were randomly assigned to one of the following three groups: group A (control group) had no immunosuppression; group B received cyclosporine (CsA) (5 mg/kg); group C receivedmycophenolate mofetil (MMF) (20 mg/kg). The animalswere killed on the 12th d. Blood and grafted tissues were obtained for laboratory and histological assessment. RESULTS: Median allograft survival was significantly higher in the two therapy groups than that in the controls (10 and 12 d for CsA and MMF respectively vs 0 d for the control group, P＜0.01). No difference in allograft survival between the CsA and MMF groups was found. However,MMF had less renal and hepatic toxicity and allowed weight gain.CONCLUSION: Monotherapy with MMF for immunosu ppression was safe in an experimental model of islet allotransplantation and was equally effective with cyclosporine, with less toxicity.

Is islet transplantation ready for widespread use in diabetes？

Up till 2000 when Edmonton group introduced islet transplant procedure in conjunction with a novel glucocorticoid-free immunosuppressive regimen rendering 100% （n=7） of patients with type 1 diabetes insulin-independent for at least 1 year, islet transplant was taken into the clinic. Although significant progress in clinical islet transplant has occurred during recent years, challenges remain, including shortage of available donor organs, technical aspects of islet preparation and transplantation, immunological rejection post-transplant, unclear long-term outcomes of islet transplantation. Special attention is given to current limitation in islet transplantation together with new possible strategies that raise expectations for the widespread use of islet transplantation in the future.

Combined laparoscopic spleen-preserving distal pancreatectomy and islet autotransplantation for benign pancreatic neoplasm

AIM: To evaluate the safety and feasibility of laparoscopic spleen-preserving distal pancreatectomy (LSPDP) with autologous islet transplantation (AIT) for benign tumors of the pancreatic body-neck.

Induction of xenogeneic islet transplantation tolerance by simultaneously blocking CD28-B7 and OX40-OX40L co-stimulatory pathways

It has been demonstrated that prolonged graft survival can be achieved through inhibiting the activation of T cells,and addition of soluble CTLA4Ig and OX40Ig proteins to mixed lymphocyte reactions can effectively inhibit T cell proliferation.To explore the potential of this type of treatment in xenotransplantation,we infected streptozotocin-induced diabetic BalB/c mice(H-2d)(200 mg/kg,IV)with 5×108 pfu AdCTLA4Ig-IRES-OX40Ig on day 1 before islets trans-plantation through the tail vein.The results showed that this treatment prolonged the islet xeno-grafts survival significantly.The reaction to exogenous glucose stimulation was normal and the cytokine secretion of the type Th1 cells was inhibited.The AdCTLA4Ig-IRES-OX40Ig-mediated treatment effectively induced the T cells into anergy and the Th1/Th2 cells into deviation.These results strongly supported the therapeutic potential of blockade of costimulation by Ad-CTLA4Ig-IRES-OX40Ig genes transfer in inducing the organ transplantation tolerance.

Bone marrow cells produce nerve growth factor and promote angiogenesis around transplanted islets

AIM:To clarify the mechanism by which bone marrow cells promote angiogenesis around transplanted islets.METHODS: Streptozotocin induced diabetic BALB/ c mice were transplanted syngeneically under the kidney capsule with the following: (1) 200 islets (islet group: n=12), (2) 1-5×106 bone marrow cells (bone marrow group: n=11), (3) 200 islets and 1-5×106 bone marrow cells (islet + bone marrow group: n= 13), or (4) no cells (sham group:n=5). All mice were evaluated for blood glucose, serum insulin, serum nervegrowth factor (NGF) and glucose tolerance (GTT) up to postoperative day (POD) 14. Histological assessment for insulin, von Willebrand factor (vWF) and NGF was performed at POD 3, 7 and 14.RESULTS: Blood glucose level was lowest and serum insulin was highest in the islet + bone marrow group. Serum NGF increased in islet, bone marrow, and islet + bone marrow groups after transplantation, and there was a significant difference (P=0.0496, ANOVA) between the bone marrow and sham groups. The number of vessels within the graft area was signif icantly increased in both the bone marrow and islet + bone marrow groups at POD 14 as compared to the islet alone group (21.2 ± 3.6 in bone marrow, P=0.01, vs islet group, 22.6 ± 1.9 in islet + bone marrow, P = 0.0003, vs islet group, 5.3 ± 1.6 in islet-alone transplants). NGF was more strongly expressed in bone marrow cells compared with islets. CONCLUSION: Bone marrow cells produce NGF and promote angiogenesis. Islet co-transplantation with bone marrow is associated with improvement of islet graft function.

Review of experimental attempts of islet allotransplantation in rodents:Parameters involved and viability of the procedure

The purpose of the present study was to organize the parameters involved in experimental allotransplantation in rodents to elaborate the most suitable model to supply the scarcity of islet donors. We used the PubMed database to systematically search for published articles containing the keywords &#x0201c;rodent islet transplantation&#x0201d; to review. We included studies that involved allotransplantation experiments with rodents&#x02019; islets, and we reviewed the reference lists from the eligible publications that were retrieved. We excluded articles related to isotransplantation, autotransplantation and xenotransplantation, i.e., transplantation in other species. A total of 25 studies related to allotransplantation were selected for systematic review based on their relevance and updated data. Allotransplantation in rodents is promising and continues to develop. Survival rates of allografts have increased with the discovery of new immunosuppressive drugs and the use of different graft sites. These successes suggest that islet transplantation is a promising method to overcome the scarcity of islet donors and advance the treatment options for type 1 diabetes.

Induction of islet transplantation tolerance with anti-CD_4, anti-CD_8 immunotoxins and donor soluble antigen

Objective To induce islet grafting tolerance by intravenous injection of anti CD 4, anti CD 8 immunotoxins and donor soluble antigen Methods Fourteen days or 7 days prior to transplantation, the immunotoxin of anti CD 4, anti CD 8 200?μg respectively, and donor soluble antigen 500?μg were intravenously injected and then 500 donor islets were transplanted under the left renal subcapsular space of diabetes recipients (Sprague Dawley rats) Results The islet grafting survival time for those recipients pretreated with immunotoxin and donor soluble antigen was >60 days ( P <0 01) The immunotoxins, donor soluble antigen treatment alone might only slightly prolong the grafting survival time Conclusion The anti CD 4, anti CD 8 immunotoxins jointly used with donor soluble antigen can induce donor specific immunotolerance

Monitoring of clinical islet transplantation

Islet transplantation has recently emerged as one of the most promising therapeutic approaches to improving glycometabolic control in diabetic patients. The Edmonton trials demonstrated a marked improvement in the short-term rate of success of islet transplantation, with an 80% rate of insulin-independence being at 1 year after transplantation, as reported by several institutions worldwide. Unfortunately, this rate consistently decreases to 10% by 5 years post-transplantation.