Results Of Islet Transplantation Research Articles

Technical factors that minimize the occurrence of early graft failure in pancreas transplantation.

Pancreatic transplantation is the only treatment for insulin-dependent diabetes resulting in long-term euglycemia without exogenous insulin. However, pancreatic transplantation has become debatable following the improvements in the results of islet transplantation and artificial pancreas. Therefore, surgeons who perform pancreas transplants require the best surgical technique that can minimize technical failure. We aimed to report our experiences with pancreatic transplantations. We transplanted 65 pancreatic grafts between 2015 and 2020. Except for one death due to hypoxic brain damage after surgery, no postoperative technical failure was observed. We usually perform duodeno-duodenal anastomosis using the transperitoneal approach, with retrocolic placement of the graft pancreas. There was no leakage from the duodenum even after immunologic graft failure. To prevent venous thrombosis, which is the most common cause of technical failure, we used the inferior vena cava for anastomosis and added graft venoplasty with a patch of donor vena cava or aortic interposition graft to the bench procedure; subsequently, there were no cases of technical failure due to thrombosis post-transplantation. Therefore, the 1-year graft survival (insulin-free) rate was more than 95%. The improving the surgical technique will maintain pancreatic transplantation as the best treatment for insulin-dependent diabetes.

Mesenteric lymph nodes as alternative site for pancreatic islet transplantation in a diabetic rat model

BackgroundIslet transplantation has progressively become a safe alternative to pancreas transplantation for the treatment of type 1 diabetes. However, the long-term results of islet transplantation could be significantly increased by improving the quality of the islet isolation technique even exploring alternative islet transplantation sites to reduce the number of islets required to mitigate hyperglycemia. The goal of the study was to test the lymph node as a suitable anatomical location for islet engraftment in a rodent model.MethodsForty Lewis rats, 6–8 weeks old, body weight 250–300 g, have been used as islet donors and recipients in syngeneic islet transplantation experiments. Ten rats were rendered diabetic by one injection of 65 mg/Kg of streptozotocin. After pancreas retrieval from non diabetic donors, islet were isolated and transplanted in the mesenteric lymph nodes of 7 diabetic rats. Rats were followed for 30 days after islet transplantation.ResultsA total of 7 islet transplantations in mesenteric lymph nodes have been performed. Two rats died 24 and 36 h after transplantation due to complications. No transplanted rat acquired normal glucose blood levels and insulin independence after the transplantation. However, the mean blood levels of glycemia were significantly lower in transplanted rats compared with diabetic rats (470.4 mg/dl vs 605 mg/dl, p 0.04). Interestingly, transplanted rats have a significant weight increase after transplantation compared to diabetic rats (mean value 295 g in transplanted rats vs 245 g in diabetic rats, p < 0.05), with an overall improvement of social activities and health. Immunohistochemical analysis of the 5 mesenteric lymph nodes of transplanted rats demonstrated the presence of living islets in one lymph node.ConclusionsAlthough islet engraftment in lymph nodes is possible, islet transplantation in lymph nodes in rats resulted in few improvements of glucose parameters.

Has the gap between pancreas and islet transplantation closed?

Both pancreas and islet transplantations are therapeutic options for complicated type 1 diabetes. Until recent years, outcomes of islet transplantation have been significantly inferior to those of whole pancreas. Islet transplantation is primarily performed alone in patients with severe hypoglycemia, and recent registry reports have suggested that results of islet transplantation alone in this indication may be about to match those of pancreas transplant alone in insulin independence. Figures of 50% insulin independence at 5 years for either procedure have been cited. In this article, we address the question whether islet transplantation has indeed bridged the gap with whole pancreas. Looking at the evidence to answer this question, we propose that although pancreas may still be more efficient in taking recipients off insulin than islets, there are in fact numerous "gaps" separating both procedures that must be taken into the equation. These "gaps" relate to organ utilization, organ allocation, indication for transplantation, and morbidity. In-depth analysis reveals that islet transplantation, in fact, has an edge on whole pancreas in some of these aspects. Accordingly, attempts should be made to bridge these gaps from both sides to achieve the same level of success with either procedure. More realistically, it is likely that some of these gaps will remain and that both procedures will coexist and complement each other, to ensure that β cell replacement can be successfully implemented in the greatest possible number of patients with type 1 diabetes.

The current state of pancreas transplantation

For many patients with type 1 diabetes mellitus and selected patients with type 2 diabetes mellitus, a successful pancreas transplant is the only definitive long-term treatment that both restores euglycaemia without the risk of severe hypoglycaemia and prevents, halts or reverses secondary complications. These benefits come at the cost of major surgery and lifelong immunosuppression. Nevertheless, pancreas transplants are safe and effective, with patient survival rates currently >95% at 1 year and >88% at 5 years; graft survival rates are almost 85% at 1 year and >60% at 5 years. The estimated half-life of a pancreas graft is now 7-14 years. The improvements in graft survival are attributable to considerable reductions in technical failures and in immunologic graft losses. Pancreas recipients have reduced mortality compared with waiting candidates or patients with diabetes mellitus who undergo a kidney transplant alone. Pancreas transplants should be more frequently offered to nonuraemic patients with brittle diabetes mellitus to prevent the development of secondary diabetic complications and to avoid the need for a kidney transplant. Although the results of islet transplantation have also improved, islet recipients rarely maintain long-term insulin independence despite the use of multiple organ donor pancreases. Pancreas transplants and islet transplants should be considered complementary, not mutually exclusive, procedures that are chosen on the basis of the individual patient's surgical risk.

The potential benefit of non-purified islets preparations for islet transplantation

Since the advent of islet transplantation, there has been a significant emphasis on the importance of islet purity despite an inevitable associated loss of islet mass during the purification process. One of the key elements of the 'Edmonton Protocol' for islet transplantation published in 2000 was an emphasis on the need for sequential transplants of highly purified islets (averaging 24% beta cell purity) and the close correlation between the numbers of islets transplanted and the success of the procedure. However, the emphasis on islet purity may warrant further consideration as auto transplantation of non-purified islets currently provides the most successful insulin independence rates within the field of islet transplantation. While the role of auto and allo immunity could contribute to the differences in the success rates it is clear that within the clinical setting, significant acinar and ductal contamination is well tolerated. However, one could go further and hypothesize that extra-insular tissue including acinar tissue, ductal tissue, peri-pancreatic lymph nodes and vascular tissue actually confer an advantage to islet survival/function and may even contribute to the insulin secreting capacity of the graft post transplant. As such this review will assess the influence of extra-insular pancreatic tissue on the results of islet transplantation based on published evidence and will also explore the possibility that non-islet pancreatic cells are capable of differentiating into a beta cell phenotype in vivo contributing to an ongoing regeneration of endocrine mass during the period following transplantation.

Pancreatic ductal transdifferentiation for β-cell neogenesis

Background: Transdifferentiation of exocrine pancreatic cells into insulin-secreting cells may be an alternative or a support to islet transplantation-based therapy of Type 1 diabetes. The application relates to a method of generating in vitro insulin-producing β-cells from dedifferentiated exocrine pancreatic cells using a new formulation of growth factors based on the combination of epidermal growth factor and leukemia-inhibitory factor. Objective/methods: This evaluation summarizes the current literature and the potential therapeutic application of the present patent for β-cell neogenesis. Results/conclusion: As suggested by this patent, the combination of growth factors acting on different intracellular pathways may reverse autoimmunity and increase the results of islet transplantation.

A New Preservation Solution Increases Islet Yield and Reduces Graft Immunogenicity in Pancreatic Islet Transplantation

The aim of the study was to test a new preservation solution containing polyethylene glycol (S.C.O.T. solution) as pancreatic islet isolation medium both to increase the islet yield and to prolong the allograft survival. In a model of islet transplantation in diabetic mouse, islets were isolated with S.C.O.T. in experimental groups and with Hank's balanced salt solution (HBSS) in control groups. The use of S.C.O.T. solution improved the islet yield (596+/-27 IEQ/pancreas) as compared to HBSS (456+/-11 IEQ/pancreas) (P<0.001). Allograft survival was prolonged in experimental group (17.3+/-4.3 days) versus controls (7.3+/-3.6 days) in a full mismatch combination (P<0.001) and in absence of recipient immunosuppression. The same prolongation (10 days) was also found in a strongly alloreactive transgenic combination. It is hypothesized that a transitory phenomenon of immunocamouflage of the graft surface antigens occurs, as shown by immunofluorescence studies. The use of this new solution could improve the results of islet transplantation in humans.

ATORVASTATIN DECREASES LOSS OF HUMAN PANCREATIC ISLET MASS RELATED TO INSTANT BLOOD-MEDIATED INFLAMMATORY REACTION BY DOWN-REGULATION OF TISSUE FACTOR AND MACROPHAGE CHEMOATTRACTANT PROTEIN EXPRESSION.

O384 Aims: Pancreatic islets (PI) constitutively express Tissue Factor (TF) and macrophage chemoattractant protein-1 (MCP-1). After exposure to blood, PI trigger a detrimental clotting reaction referred as instant blood-mediated inflammatory reaction (IBMIR), effect associated with significant reduction in islet mass after transplantation. TF as an initiator and MCP-1 as a chemoattractant have been demonstrated to play a critical role in this process. We hypothesized that statins, which decrease the activation of coagulation and inflammation, may down-regulate TF and MCP-1 expression in isolated human PI and therefore reduce loss of islet mass after islet exposure to blood. Methods: Immediately after isolation, groups of human hand-picked PI were incubated with Atorvastatin (10mmol/L) or vehicle for 3 days (n=5). TF and MCP-1 were determined from islet homogenates and supernatants by ELISA. To evaluate the effects of Atorvastatin on IBMIR, 5000 IEQ were perfused with ABO compatible human blood in vitro using loops of heparin-coated PVS (flow 45 mL/min, 37°C, 60 minutes). Plasma pro-insulin (hPI), β-tromboglobulin (TG) and thrombin-antithrombin (TAT) complexes were quantified by ELISA. Results: Atorvastatin decreased spontaneous PI loss during culture (day 3, 91.2±2.4% viable islet cells) compared with vehicle (82.1±3.1, P<0.05). A dose-dependent decrease in TF and MCP-1 was demonstrated after Atorvastatin treatment (10mmol/L, TF=12.3±6.4 pg/IEQ, MCP-1 3.8±2.1 pg/IEQ) compared with controls (TF=38.3±12.4, MCP-1 9.8±4.1, P<0.05). In vitro, Atorvastatin significantly reduced platelet aggregation after PI exposure to blood (platelet counts in the loops: PI media=289±21x109/L, PI=12.3±1.1x109/L, PI + Atorvastatin=160.1±2.1x109/L, n=6, P<0.001), platelet activation (TG: media=366±110 IU/mL; PI=891±156; PI+Atorvastatin=590±89, P<0.05), activation of coagulation (TAT: media=5.1±1.1 mg/L; PI=367±152; PI+Ator=122±88, P<0.05), and complement activation (C3: media=57.1±4 mg/dL; PI=16.3±7; PI+Atorvastatin 33.8±8.9= P<0.05). In parallel with activation of coagulation, PI destruction was higher in controls (proinsulin= 4998±324 pmol/L) compared with Atorvastatin-treated PI (2656±556, P<0.05). Immunohistochemical studies demonstrated reduced platelets, polymorphonuclear cells, monocytes, and fibrin surrounded the PI treated with Atorvastatin compared with controls after exposure to blood. Conclusions: Atorvastatin significantly reduced human islet expression of TF and MCP-1. This effect was associated with reduced loss of islet mass after exposure to blood. Our results suggest that the early use of statins may improve the results in islet transplantation.

Advances in long-term islet culture: the Memphis experience.

Long-term culture of human islets provides opportunity for improving results of islet transplantation. The techniques of long-term culture are reproducible and can result in improved function of the islet after transplantation into NOD-SCID mice. We have been able to cure streptozotocin-induced diabetes by islets cultured for more than 6 mo. Culture conditions play an important role in the success of the procedure. Culture success is dependent on the media type, additives, type of colloid or protein used, purity of the islets, and concentration and volume of the tissue. Cellular and structural changes occur over time in culture. These changes may explain the improved efficacy of the islet graft after short and intermediate culture periods. Further research into long-term culture of islets is necessary to fully explore the potential of the technique.

Vascularized islet-cell transplantation in miniature swine. I. Preparation of vascularized islet kidneys.

Whereas clinical pancreatic transplantation has been highly successful in correcting the hyperglycemia of insulin-dependent diabetes mellitus (type 1), the results of islet transplantation have been disappointing. This discrepancy may be because of, at least in part, nonspecific loss of islets during the time required for revascularization. To test this hypothesis, we have designed composite kidney grafts containing vascularized autologous islets that can be used to compare the engraftment potential of vascularized versus nonvascularized islet tissue. (1) Islet-cell isolation: miniature swine underwent either partial pancreatectomy to isolate autologous islets or total pancreatectomy to isolate minor antigen-mismatched islets. Islets were purified from excised pancreatic tissue by enzymatic digestion and discontinuous density gradient purification. Isolated islets were cultured for 3 days before transplant. (2) Creation of vascularized islet kidneys (IK): autologous islets alone (n=6), minor-mismatched islets alone (n=3), and minor-mismatched islets plus simultaneous autologous thymic tissue (n=3) were transplanted beneath the renal capsule of juvenile miniature swine. Minor antigen-mismatched islets were also transplanted into both the vascularized thymic graft of a thymokidney (to produce a thymo-islet kidney [TIK]) and the contralateral native kidney (n=3) and both the host thymus and beneath the renal capsule (n=2). All recipients receiving minor-mismatched islets were treated with a 12-day intravenous (IV) course of either cyclosporine A (CsA) at 10 mg/kg per day or FK506 at 0.15 mg/kg per day. (3) Assessment of Function: to evaluate the function of the transplanted islets, three animals bearing TIK and IK underwent total pancreatectomy 3 months following islet transplantation. (1) Islet-cell yields: an average of 254,960+/-51,879 (4,452+/-932 islet equivalents [IEQ]/gram of pancreas) and 374,410+/-9,548 (4,183+/-721 IEQ/gram of pancreas) viable islets were obtained by partial pancreatectomy and complete pancreatectomy, respectively. (2) Creation of IK: autologous islets engrafted indefinitely, whereas recipients of minor-mismatched islets alone rejected the islets within 2 months. However, when minor-mismatched islets were implanted into both the thymokidney and the contralateral kidney of animals bearing a thymokidney, the islets engrafted indefinitely in both sites (>3 months). Simultaneous implantation of islets into the host thymus and under the renal capsule also led to permanent engraftment of minor-mismatched islets. (3) Function of vascularized islets: three animals with both a TIK and an IK in place for 3 months underwent total pancreatectomy. All three animals maintained normoglycemia thereafter. In two of these animals, the IKs were removed 2 months after the pancreatectomy, and in both cases normoglycemia was maintained thereafter by the TIK. The implantation of islets beneath the autologous renal capsule permitted the establishment of a vascular supply and thereby supported normal islet-cell growth and function. The presence of thymic tissue beneath the autologous renal capsule facilitated the engraftment of minor-mismatched islets, and such grafts achieved results similar to autologous islet transplants. Therefore, the ability to create vascularized islet grafts may provide a strategy for successful islet transplantation across allogeneic and potentially across xenogeneic barriers.

New therapeutic approaches to type 1 diabetes: from prevention to cellular or gene therapies.

New therapeutic approaches to type 1 diabetes: from prevention to cellular or gene therapies.

LONGTERM 3D COLLAGEN SPONGE MATRIX ISLET CULTURE-THE EFFECT OF HEPATOCYTE COCULTURE

119 We believe that a stable or growing culture of beta islets would provide advantages in availability, immune response, and numbers of islets that could improve the results in islet transplantation. Loss of function and mass of beta islets in cultures is a barrier to utilizing islets in transplantation. We hypothesized that islets would have improved survival and function when co-cultured with hepatocytes(HC). Methods: Islets were isolated with collagenase and differential (ficoll) centrifugation. HC were isolated using collagenase and percoll centrifugation. Routine viability was >95% by trypan blue. Islets were cultured in a collagen sponge matrix with HC at a ratio of 1:50, 1:25, or 0 HC. Insulin response is measured by static glucose stimulation (300mg/dl for 1 hr) and stimulation index (SI) calculated (stimulated insulin secretion/basal insulin secretion). All insulin was measured by RIA and reported as ng/ml/islet. Results: The 3-D sponge collagen matrix culture environment resulted stable viability and SI for 14wks. The benefit of HC co-culture in the insulin production and islet survival was seen in the 1:50 HC groups (see graph). The ratio of insulin release to static glucose stimulation at week 12 compared to week 1 p=0.038 1:50 HC(0.82) vs no HC(.064). The stimulation index did not change over the 14 weeks (see graph), but the absolute amount of insulin released during static glucose stimulation per islet decreased steadily in all culture groups. We have interpreted this as loss of islet mass even though BrDU uptake in the islets does indicate cell division. We conclude from this study that 3 dimensional collagen matrix allows long-term in vitro islet viability, HC co-culture does result in improved islet response to glucose stimulation during long-term culture, but that loss of islet mass is not halted by co-culture with HC.Figure

Direct and indirect pathways of immunity to pancreatic islet transplants

R esults from the Diabetes Control and Complications Trial demonstrated the importance of maintaining euglycemia for abating long-term disease complications.’ However, despite exogenous insulin therapy, complications continue to be the major source of morbidity and mortality in Type I diabetes. As such, the restoration of euglycemia through transplanting insulin-producing tissues in the form of whole organ pancreas or isolated islet tissue remains an important option for the treatment of insulin-dependent diabetes. To date, the results of pancreas transplantation has been greatly superior to islet transplantation for achieving insulin independence in Type I diabetic patients.2A However, islet transplantation continues to serve as an attractive alternative treatment due to the potential for modifling the graft (immunomodulation), the capacity for immunoisolating the grafted tissue, and for the possible use of xenogeneic donors. There are a number of obstacles that may add to the disappointing results of islet transplantation. Nonimmunologic factors may contribute to islet dysfunction, such as initial ischemia and failure of the tissue to engraft, long-term functional insufficiency in an ectopic site (eg, liver), and the potential deleterious effects of immunosuppressive agents such as cyclosporine and steroids on islet metabolism. Immunologic responses, including transplantation rejection and the recurrence of autoimmune pathogenesis associated with Type I diabetes, are also major barriers to successful islet transplantation. The focus of this discussion will be to examine the nature of T lymphocyte-dependent immune responses to pancreatic islet transplants. Emphasis will be placed on contrasting the nature of alloimmune, xenoimmune, and autoimmune responses in animal models of islet transplantation.

Results of Human Islet Allotransplantation in Cystic Fibrosis and Type I Diabetic Patients

TRANSPLANTATION of isolated islets of Langerhans is an alternative approach to whole organ pancreas transplantation. Before 1990, the results of islet transplantation in humans were frustrating, but with new isolation and purification techniques of human pancreases, clinical trials of islet transplantation have been reported in a few specialized centers worldwide. The International Islet Registry counted 305 human islet allografts at the end of 1995. Insulin independence at one year was achieved in 8% of the patients, but 20% of insulin-dependent cases showed a graft function with a normal basal C-peptide and improved glycemic regulation. We report herein our initial experience in human islet allotransplantation in six patients.

Influence of islet and bone marrow transplantation on the diabetes and immunodeficiency of BB rats

The results of islet transplantation in spontaneous autoimmune diabetes of BB rats were studied to determine whether this disease process might damage the transplanted islet tissue. Since BB rats are not genetically uniform, syngenetic grafts could not be used; therefore, allograft rejection was prevented by rendering BB rats immunologically tolerant of WF transplantation antigens by neonatal inoculation with bone marrow cells. Despite the resultant tolerant state, which permitted successful engraftment of WF skin allografts, the transplanted islets ameliorated the spontaneous diabetes of BB rats only briefly before they were destroyed by immune insulitis. BB rats from the diabetic stock were found to suffer from abnormalities in T lymphocytes and their subsets as well as defective immune response patterns. When analyzed with monoclonal antibodies specific for rat lymphocyte markers, BB rats of the diabetic stock were found to be lymphocytopenic. There was a reduction in helper T cells and a more severe deficit in the suppressor/cytotoxic subset. BB rats that were inoculated neonatally with bone marrow from normal donors were found to have a strikingly reduced incidence of diabetes. Moreover, the T cell functional, numerical, and microenvironmental defects that were present in noninoculated BB rats were restored in marrow-inoculated BB rats, findings possibly related to the decreased incidence of diabetes.

Transplantation of Islets and Bone Marrow Cells to Animals with Immune Insulitis

The results of islet transplantation in an animal model of spontaneous immune insulitis were studied to see whether this disease process might damage transplanted tissue. Since the insulitis occurs only in "BB" rats (which are not genetically uniform) syngeneic grafts could not be used, therefore allograft rejection was avoided by rendering "BB" rats tolerant of WF transplantation antigens by inoculating them neonatally with WF bone marrow cells. Despite the resultant tolerant state, which permitted successful engraftment of WF skin and islets transplanted to artificially diabetic "BB" rats, tolerant "BB" rats with spontaneous diabetes accepted transplanted WF islets only briefly before they were destroyed by immune insulitis. "BB" rats were found to have abnormalities in immune response (delayed skin graft rejection and decreased alloreactivity in mixed lymphocyte response). "BB" rats that were treated neonatally with WF bone marrow. Moreover, "BB" rats inoculated with WF bone marrow neonatally were found less likely to become diabetic than untreated "BB" controls. It is suggested that the chimeric state (persistence of WF bone marrow cells) may be responsible for the improved immune response and perhaps for the decreased susceptibility to diabetes.