Improved survival of intraportal pancreatic islet cell allografts in patients with type-1 diabetes mellitus by refined peritransplant management

Insulin independence following islet transplantation improves long-term metabolic outcomes

AIMS

Pancreatic islet allotransplantation is an effective therapy for type 1 diabetes mellitus, restoring glycaemic control and hypoglycaemic awareness in patients with recurrent severe hypoglycaemia. Insulin independence following transplant is being increasingly reported; however, this is not a primary endpoint in the UK. Having surpassed 10 years of islet transplantation in Scotland, we aimed to evaluate the impact of insulin independence following transplant on metabolic outcomes and graft survival.

METHODS

We conducted a retrospective analysis on data collected prospectively between 2011 and 2022. Patients who underwent islet transplantation in Scotland up to the 31st January 2020 were included. Primary endpoint was graft survival (stimulated C-peptide >50 pmol/L). Secondary endpoints included GOLD score, HbA1c, C-peptide and insulin requirement. Outcomes were compared between patients who achieved insulin independence at any point following transplant versus those who did not.

RESULTS

60 patients were included. 74.5% experienced >50 severe hypoglycaemic episodes in the year preceding transplant. There was a 55.0% decrease in insulin requirement following transplant and 30.0% achieved insulin independence. Mean graft survival time was 9.0 years (95% CI 7.2-10.9) in patients who achieved insulin independence versus 4.4 years (95% CI 3.4-5.3) in patients who did not. Insulin independence was associated with significantly improved graft function, glycaemic control and hypoglycaemic awareness at 1 year.

CONCLUSIONS

This is the largest UK single-centre study on islet transplant to date. Our findings demonstrate significantly improved outcomes in patients who achieved insulin independence following islet transplantation.

Pax4 Gene Delivery Improves Islet Transplantation Efficacy by Promoting β Cell Survival and α-to-β Cell Transdifferentiation

The transcription factor Pax4 plays an essential role in the development of insulin-producing β cells in pancreatic islets. Ectopic Pax4 expression not only promotes β cell survival but also induces α-to-β cell transdifferentiation. This dual functionality of Pax4 makes it an appealing therapeutic target for the treatment of insulin-deficient type 1 diabetes (T1D). In this study, we demonstrated that Pax4 gene delivery by an adenoviral vector, Ad5.Pax4, improved β cell function of mouse and human islets by promoting islet cell survival and α-to-β cell transdifferentiation, as assessed by multiple viability assays and lineage-tracing analysis. We then explored the therapeutic benefits of Pax4 gene delivery in the context of islet transplantation using T1D mouse models. Both mouse-to-mouse and human-to-mouse islet transplantation, via either kidney capsule or portal vein, were examined. In all settings, Ad5.Pax4-treated donor islets (mouse or human) showed substantially better therapeutic outcomes. These results suggest that Pax4 gene delivery into donor islets may be considered as an adjunct therapy for islet transplantation, which can either improve the therapeutic outcome of islet transplantation using the same amount of donor islets or allow the use of fewer donor islets to achieve normoglycemia.

New Frontiers in the Treatment of Type 1 Diabetes

Type 1 diabetes is an autoimmune disease caused by the immune-mediated destruction of pancreatic β cells that results in lifelong absolute insulin deficiency. For nearly a century, insulin replacement has been the only therapy for most people living with this disease. Recent advances in technology and our understanding of β cell development, glucose metabolism, and the underlying immune pathogenesis of the disease have led to innovative therapeutic and preventative approaches. A paradigm shift in immunotherapy development toward the targeting of islet-specific immune pathways involved in tolerance has driven the development of therapies that may allow for the prevention or reversal of this disease while avoiding toxicities associated with historical approaches that were broadly immunosuppressive. In this review, we discuss successes, failures, and emerging pharmacological therapies for type 1 diabetes that are changing how we approach this disease, from improving glycemic control to developing the "holy grail" of disease prevention.

Regenerating β cells of the pancreas - potential developments in diabetes treatment

INTRODUCTION

The etiology of diabetes is mainly attributed to insulin deficiency due to the lack of β cells (type 1), or to insulin resistance that eventually results in β cell dysfunction (type 2). Therefore, an ultimate cure for diabetes requires the ability to replace the lost insulin-secreting β cells. Strategies for regenerating β cells are under extensive investigation.

AREAS COVERED

Herein, the authors first summarize the mechanisms underlying embryonic β cell development and spontaneous adult β cell regeneration, which forms the basis for developing β cell regeneration strategies. Then the rationale and progress of each β cell regeneration strategy is reviewed. Current β cell regeneration strategies can be classified into two main categories: in vitro β cell regeneration using pluripotent stem cells and in vivo reprogramming of non-β cells into β cells. Each has its own advantages and disadvantages.

EXPERT OPINION

Regenerating β cells has shown its potential as a cure for the treatment of insulin-deficient diabetes. Much progress has been made, and β cell regeneration therapy is getting closer to a clinical reality. Nevertheless, more hurdles need to be overcome before any of the strategies suggested can be fully translated from bench to bedside.

Long-Term Insulin Independence following Repeated Islet Transplantation in Totally Pancreatectomized Diabetic Pigs

Clinical islet transplantation (Tx) in type I diabetic patients has been successful so far only in a minority of cases, probably because of multiple factors, partly immunologic and partly nonimmunologic in nature. Pre-clinical studies of islet Tx in large animals are still needed to clarify the reasons and find possible solutions. In this study, we tested the feasibility of noninvasive, repeated intrahepatic allo-Tx of porcine pancreatic islets obtained from multiple donors, in pigs rendered diabetic by total pancreatectomy (Pct). In group I Yucatan miniature swine (n = 6), after induction of diabetes by Pct, repeated islet allo-Tx of ≥80% pure islets was performed. Islets obtained from two pigs of the Hanford breed were injected twice a week, half freshly isolated and half 48-h cultured, over a period of 11 days, for a total of 23,647 ± 1617 islet equivalents (IE)/kg recipient body weight (BW). In group II Yucatan miniature swine (n = 3), after Pct, a single allo-Tx of ≥80% pure islets, previously obtained from two donors of the Hanford breed, was performed, using a total of 22,416 ± 1124 IE/kg BW. In group III Yucatan miniature swine (n = 3), auto-Tx of 60–75% pure islets, averaging 2980 ± 424 IE/kg BW, was performed a few hours after Pct. Group IV Yucatan mini pigs (n = 3) underwent Pct and were used as diabetic controls. Group V animals (n = 3) were normal control Yucatan mini pigs. Porcine islets were isolated by a modification of the standard collagenase digestion and Ficoll gradient purification method. Donors and recipients were chosen on the basis of moderate to high mutual alloreactivity in mixed lymphocyte culture (MLC). In groups I and II, cyclosporine A (CsA) was started 4 days before allo-Tx, at the dose of 15 mg/kg IM, and then gradually reduced to 4 mg/kg IM. In all group I animals, normal fasting blood glucose (FBG) was restored within 2–3 weeks. Two normoglycemic pigs died of acute pneumonia at 33 and 112 days, respectively, and one animal became progressively hyperglycemic at 100 days. After 3 months, discontinuation of CsA treatment resulted in FBG increase in two group I animals. In one pig, CsA was stopped after 151 days, and normoglycemia persisted until euthanasia, after 8 months. In group II pigs, normoglycemia lasted 4–20 days, with a progressive increase of insulin requirement thereafter. In group III animals, after islet auto-Tx, normoglycemia lasted 7–10 days, while insulin daily requirement progressively increased thereafter, stabilizing at 0.4 IU/kg/day, corresponding to about one third of the amount required in diabetic controls. The single most important result in this series of experiments is that intraportal allo-Tx of a sufficient islet mass, divided in multiple subtherapeutic doses, produced a better metabolic long-term control in comparison to a single injection of the same amount of islets. The technique of multiple-donor repeated islet Tx may prove useful to overcome the problem of primary nonfunction or early graft failure, currently limiting the success of clinical islet Tx in most cases.

Hepatic Cells via Cava Vein Can Influence Allogenic Islet Rat Transplantation

We have reported, previously, some effect of allogenic hepatic cells for islet tolerance when they are injected mixed (hepatic cells and islets) in different proportions via portal vein, in diabetic Wistar rats. Now we have studied the role of allogenic hepatic cells injected sequentially 15 min before islets, comparing via the portal vein (A and B groups) and via the cava vein (C and D groups) with a control group of islets alone. The allogenic islets were always injected via portal vein, in similar conditions, while the ratio of hepatic cells/islets was 100:1 (A, C groups) or 200:1 (B, D groups). Islets and hepatic cells were obtained from several different rats. The transplanted rats were observed during 30 days and results compared among the different rat groups: porta-porta (P/P), cava-porta (C/P), and control group. Statistically, a significant interaction between type of transplant and proportion of hepatic cells was observed. Also, C plus D groups showed statistical difference with the control group (p < 0.017) and also all the groups together (p < 0.047). These results suggest that hepatic cells can induce, in some cases, islet graft prolongation in Wistar rats. Better results were obtained when hepatic cells were injected via the cava vein than via the portal vein. Because we used a liver cell suspension integrated for several kinds of cells, the study does not clarify if this effect can be related to some specific hepatic cell subpopulation. To confirm the results and to determine if the hypothetical mechanism can be attributed to a block of the immune system or to some factor secreted by hepatic cells, more studies must be performed.

Human islet transplantation: expectation versus reality

Although experimental islet isolation and transplantation has continued for over 25 years, the results of human islet transplantation in patients with type 1 diabetes were disappointing until June 2000 when the University of Alberta, Edmonton, Canada reported 100% insulin independence in a cohort of seven patients. The study introduced several innovations now under evaluation worldwide. In the United Kingdom, an Islet Transplant Consortium has been established to co-ordinate clinical trials in several centres. The Canadian results have renewed hope of establishing islet transplantation as a treatment for diabetes while highlighting the need to identify plentiful sources of insulin secreting tissue and alternatives to current immunosuppressive therapies.

Progress in islet transplantation in patients with type 1 diabetes mellitus

More than 500 patients with type 1 diabetes mellitus have now received islet transplants at over 50 institutions worldwide in the past 5 years. Rates of insulin independence at 1 year with current protocols are impressive. However, inexorable decay of islet function over time indicates that there are many opportunities for improvement. Improved control of glycosylated hemoglobin and reduced risk of recurrent hypoglycemia are seen as important benefits of islet transplantation, irrespective of the status regarding insulin independence. For the use of islet transplantation to expand it is essential that the donor-to-recipient ratio be reliably reduced to 1 : 1. Enormous opportunities lie ahead for the development of successful living donor islet transplantation, single donor protocols, improved engraftment, islet proliferation in vitro and in the recipient, alternative islet sources, and novel tolerizing drugs. With these emerging opportunities, islet transplantation may expand to include more patients with type 1 diabetes, including children, and will not be restricted to the most unstable forms of the disease, as it is today.

Impact of perioperative management of glycemia in severely obese diabetic patients undergoing gastric bypass surgery

BACKGROUND

Roux-en-Y gastric bypass (RYGB) surgery is associated with rapid postsurgical improvement in glycemic control in patients with type 2 diabetes mellitus (T2 DM). However, there is little outcome-based evidence to guide the glycemic management of this patient group preoperatively.

OBJECTIVES

We conducted 2 pilot studies randomizing patients to assess the impact of intensive glucose management pre- and post-RYGB on clinical outcomes after surgery.

SETTING

University hospital.

METHODS

In the GLUCOSURG-pre randomized controlled trial (RCT), 34 obese T2 DM patients with glycated hemoglobin (HbA1 c) ≥8.5% (69 mmol/mol) undergoing RYGB were randomly assigned to receive either glucose optimization or no optimization 3 months preoperatively. In the GLUCOSURG-post RCT, 35 obese T2 DM patients on insulin were randomly assigned to either intensive or conservative glucose management up to 2 weeks post- RYGB. HbA1c at 1 year post-RYGB was the primary outcome.

RESULTS

In GLUCOSURG-pre, the HbA1 c at 1 year postsurgery was -3.0% (51.9 mmol/mol) in the optimized and -4.0% (45.4 mmol/mol) in the nonoptimized groups (P = .06). In GLUCOSURG-post, there were no significant differences in HbA1 c at 1 year postsurgery between the intensive and conservative groups [-2.4% (44.3 mmol/mol)] versus [-2.3% (44.3 mmol/mol), P = .73)].

CONCLUSIONS

Our pilot studies suggested that neither intensive management of glycemia in the 3 months pre- RYGB, nor the first 2 weeks post-RYGB resulted in better glycemic control one year after surgery. RYGB has substantial effects on glucose control, and additional intensive glucose-lowering interventions do not confer clinical benefits compared to conservative approaches.

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

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

Regeneration and bioengineering of transplantable abdominal organs: current status and future challenges

INTRODUCTION

The most critical issue to organ transplantation is the identification of new sources of organs. The present manuscript illustrates the state-of-the-art regenerative medicine (RM) investigations aiming to manufacturing abdominal organs for transplant purposes.

AREAS COVERED

This manuscript focuses on research in the bioengineering and regeneration of kidneys, insulin-producing cells, livers and small bowel. The main technology currently under development exploits the seeding of cells on supporting scaffolding material. Despite favorable preliminary results obtained with relatively simple, hollow organs, when more complex organs are considered, the scenario changes dramatically. Investigations are still in early stages, and clinical translation is not yet foreseeable based on current knowledge and information. Obstacles are numerous but we believe the critical factor hampering success is lack of in-depth understanding of the extracellular matrix (ECM) and cell-ECM interactions, as well as the mechanisms with which organs develop in utero.

EXPERT OPINION

The success of RM to generate transplantable abdominal organs relies heavily on progress in (stem) cell therapies, developmental and ECM biology, and in the thorough understanding of the intricate relationship and interplay between cells and the ECM. This will require enormous investments in financial and medical resources, which ideally should be embarked upon by governments, the private sector and academia.

Molecular imaging: a promising tool to monitor islet transplantation

Replacement of insulin production by pancreatic islet transplantation has great potential as a therapy for type 1 diabetes mellitus. At present, the lack of an effective approach to islet grafts assessment limits the success of this treatment. The development of molecular imaging techniques has the potential to fulfill the goal of real-time noninvasive monitoring of the functional status and viability of the islet grafts. We review the application of a variety of imaging modalities for detecting endogenous and transplanted beta-cell mass. The review also explores the various molecular imaging strategies for assessing islet delivery, the metabolic effects on the islet grafts as well as detection of immunorejection. Here, we highlight the use of combined imaging and therapeutic interventions in islet transplantation and the in vivo monitoring of stem cells differentiation into insulin-producing cells.

Impact of islet transplantation on diabetes complications and quality of life

Insulin represents a life-saving therapy for patients with type 1 diabetes but, despite appropriate treatment, it prevents only partially long-term diabetic complications, while generating fatal hypoglycemic episodes. Islet transplantation gained attention because of its safety, effectiveness, and minimal invasiveness; however it remains a procedure reserved for a selected group of patients. The introduction of the Edmonton Protocol in 2000, based on a newly designed steroid-free immunosuppressive protocol, revamped the course of islet transplantation. The main goal of islet transplantation remains insulin independence, although the effect of islet transplantation can be more comprehensively evaluated in terms of frequency of hypoglycemic episodes and impact on diabetic complications and quality of life. Islet transplantation was shown to have positive consequences on cardiovascular, renal, neurologic, and ocular diabetic complications. The proof of concept for cellular replacement therapy in diabetes has been established with islet transplantation, it only needs to be improved and rendered widely available.

Circulating cytokines are associated with human islet graft function in type 1 diabetes

Islet cell transplantation has considerable potential as a cure for type 1 diabetes, but recurrent autoimmunity and allograft rejection in which both cytokines play an important role are major obstacles. Using a new approach considering confounders by regression analysis, we investigated circulating cytokines and their association with graft function in type 1 diabetes patients who underwent either simultaneous islet kidney (SIK) or islet after kidney (IAK) transplantation. After transplantation, interleukin (IL)-10 was lower in SIK recipients with subsequent loss of graft function in comparison to recipients maintaining graft function. Before transplantation, high IL-13 and IL-18 concentrations were prospectively associated for subsequent loss of graft function in IAK recipients, whereas in SIK recipients, high macrophage migration inhibitory factor (MIF) concentrations were associated with subsequent loss of graft function. Circulating cytokines are associated with islet graft function in patients with long-standing type 1 diabetes when considering confounders.

Pathogen inactivation of human serum facilitates its clinical use for islet cell culture and subsequent transplantation

Serum is regarded as an essential supplement to promote survival and growth of cells during culture. However, the potential risk of transmitting diseases disqualifies the use of serum for clinical cell therapy in most countries. Hence, most clinical cell therapy programs have replaced human serum with human serum albumin, which can result in inferior quality of released cell products. Photochemical treatment of different blood products utilizing Intercept® technology has been shown to inactivate a broad variety of pathogens of RNA and DNA origin. The present study assesses the feasibility of using pathogen-inactivated, blood group-compatible serum for use in human pancreatic islet culture. Isolated human islets were cultured at 37°C for 3-4 days in CMRL 1066 supplemented with 10% of either pathogen-inactivated or nontreated human serum. Islet quality assessment included glucose-stimulated insulin release (perifusion), ADP/ATP ratio, cytokine expression, and posttransplant function in diabetic nude mice. No differences were found between islets cultured in pathogen-inactivated or control serum regarding stimulated insulin release, intracellular insulin content, and ADP/ATP ratio. Whether media was supplemented with treated or nontreated serum, islet expression of IL-6, IL-8, MCP-1, or tissue factor was not affected. The final diabetes-reversal rate of mice receiving islets cultured in pathogen-inactivated or nontreated serum was 78% and 87%, respectively (NS). As reported here, pathogen-inactivated human serum does not affect viability or functional integrity of cultured human islets. The implementation of this technology for RNA- and DNA-based pathogen inactivation should enable reintroduction of human serum for clinical cell therapy.

Cooperative signaling for angiogenesis and neovascularization by VEGF and HGF following islet transplantation

BACKGROUND

Delayed angiogenesis remains a significant challenge to the survival of transplanted islets. In this study, using a murine model of subcutaneous islet transplantation with matrigel basement membrane matrix, we determined the role of the proangiogenic growth factors in enhancing the islet engraftment.

METHODS

BALB/c islets were transplanted subcutaneously in growth factor reduced (GFR) or growth factor supplemented (GFS) matrigel into diabetic severe combined immunodeficient mice. GFS matrigel was prepared by supplementing GFR with proangiogenic factors, vascular endothelial growth factor (VEGF) and hepatocyte growth factor (HGF). The functioning grafts were harvested at 15 days and vessel formation was analyzed histopathologically.

RESULTS

Our results demonstrate that suboptimal (250) islet equivalents in GFS-VEGF+HGF were able to restore normoglycemia, whereas those transplanted in GFR failed to reverse diabetes. Histopathology of the GFS-VEGF+HGF graft revealed 12±3 blood vessels per field, whereas GFR, GFS-VEGF, and GFS-HGF grafts had only 3±1, 6±2, and 4±1 blood vessels, respectively. Insulin staining demonstrated increased number of islets in matrigel supplemented with VEGF and HGF. Protein and mRNA analysis demonstrated enhanced intercellular adhesion molecule and vascular cell adhesion molecule within the islets when supplemented with both VEGF+HGF suggesting stable blood vessel formation. Transcription factors focal adhesion kinase phosphorylation and extracellular signal-regulated kinase1/2 phosphorylation were also increased (8-fold and 4.6-fold, respectively) when both the growth factors were present. There was weak expression of transcription factors when VEGF or HGF were supplemented alone.

CONCLUSION

We conclude that proangiogenic growth factors, VEGF and HGF, synergistically enhance angiogenesis after islet transplantation leading to stable engraftment.

Non-invasive detection of transplanted pancreatic islets

Type 1 diabetes (insulin-dependent, IDDM) results in immune-mediated destruction of pancreatic beta cells, which leads to a deficiency in insulin secretion and as a result, to hyperglycaemia. Keeping blood glucose levels under tight control represents the most effective way either to prevent the onset or to reduce the progression of the chronic complications of IDDM. At present, pancreatic islet transplantation is emerging as the most promising clinical modality, which can stop diabetes progression without increasing the incidence of hypoglycaemic events. Although early results of clinical trials using the Edmonton Protocol and its variations are very encouraging, it is still unclear how long the islets will survive and how often the transplantation procedure will be successful. In order to monitor transplantation efficiency and graft survival, reliable non-invasive imaging methods are critically needed. If such methods are introduced clinically, essential information regarding the location, function and viability of transplanted islets can be obtained repeatedly and non-invasively. This review will focus on the latest advancements in the field of in vivo imaging of islet transplantation and describe various islet labelling and imaging techniques. In addition, we will critically look into limitations and obstacles currently present on the way to successful clinical implementation of this approach.

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.

Beta-cell replacement in immunosuppressed recipients: old and new clinical indications

Islet transplantation is an appealing procedure able to improve glycemic control in type 1 diabetic patients. However, the possible side effects that may be induced by immunosuppressive therapy limit its application to a select number of patients for whom the risk of immunosuppressants' side effects can be justified. For patients with type 1 diabetes mellitus-who will take immunosuppressants regardless, as they require a solid organ transplant-islet infusion can be an interesting therapeutic option for improving metabolic compensation, whenever pancreas transplant is not possible. Hence, islet infusion can be an important therapeutic option for patients with secondary diabetes mellitus even when a minor pancreatic endocrine function remains. For these patients, results may be better than those obtained with islet infusion for patients with type 1 diabetes mellitus thanks to the lack of autoimmune reaction to the infused islets. The final result is the improvement of the glycemic compensation and most likely also an extension of the graft survival.

Allogeneic islet transplantation

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

[Therapy of diabetes mellitus. Pancreas transplantation, islet transplantation, stem cell and gene therapy]

The long-term normalization of glucose metabolism - a prerequisite for the prevention of secondary complications in patients with diabetes mellitus - is only possible by transplantation of a whole pancreas or a reasonable number of islets. An absolute indication for pancreas grafting is given in type 1 diabetic patients with end-stage renal disease. The 1-year survival after simultaneous kidney/pancreas transplantation is, according to the international registry, 94-100% for patients, 89-92% for kidneys and 85-87% for the pancreas. The high success rate with long lasting normalization of glucose metabolism leads to a stabilization and/or amelioration of secondary complications, to an increase in quality of life and, most importantly, to a significant reduction in mortality when compared to diabetic kidney recipients. The indications for islet transplantation are similar to those for pancreatic grafting. Islet grafting is only a minor surgical procedure, but islet isolation is difficult. The 1-year survival for the recipients is 98%, for the islets 82% and for insulin-independency 42%. There is a significant decline of islet function to 10% 5 years after transplantation. Stem cell therapy would provide a definitive treatment solution not only for patients with type 1 diabetes. So far, this therapeutic option is still at an early stage of development.

Islet cell transplantation today

INTRODUCTION

Long-term studies strongly suggest that tight control of blood glucose can prevent the development and retard the progression of chronic complications of type 1 diabetes mellitus. In contrast to conventional insulin treatment, replacement of a patient's islets of Langerhans either by pancreas organ transplantation or by isolated islet transplantation is the only treatment to achieve a constant normoglycemic state and avoiding hypoglycemic episodes, a typical adverse event of multiple daily insulin injections. However, the cost of this benefit is still the need for immunosuppressive treatment of the recipient with all its potential risks.

MATERIALS AND METHODS

Islet cell transplantation offers the advantage of being performed as a minimally invasive procedure in which islets can be perfused percutaneously into the liver via the portal vein. Between January 1990 and December 2004, 458 pancreatic islet transplants worldwide have been reported to the International Islet Transplant Registry (ITR) at our Third Medical Department, University of Giessen/Germany.

RESULTS

Data analysis of islet cell transplants performed in the last 5 years (1999-2004) shows at 1 year after adult islet transplantation a patient survival rate of 97%, a functioning islet graft in 82% of the cases, whereas insulin independence was meanwhile achieved in 43% of the cases. However, using a novel protocol established by the Edmonton Center/Canada, the insulin independence rates have improved significantly reaching meanwhile a 50-80% level.

CONCLUSION

Finally, the concept of islet cell or stem cell transplantation is most attractive, as it offers many perspectives: islet cell availability could become unlimited and islet or stem cells my be transplanted without life-long immunosuppressive treatment of the recipient, just to mention two of them.

Development of anti-human leukocyte antigen class 1 antibodies following allogeneic islet cell transplantation

Currently there is minimal concern that islet allograft failure could result from the development of anti-human leukocyte antigen (HLA) antibodies reactive to the allograft. We report here a case of islet allograft failure where the recipient developed immunoglobulin G anti-HLA class I antibodies reactive to HLA antigens present in two of the three islet cell donors. The patient had no detectable anti-HLA antibodies prior to the transplant but these antibodies were detected approximately 4 months posttransplant. Of concern, these antibodies developed despite induction with anti-IL2R antibodies (Zenapex) prior to intraportal islet cell infusion, low-dose tacrolimus (12-hour troughs 3 to 5 ng/mL) and rapammune (target troughs 12 to 15 ng/mL). The patient was not presensitized with blood products or a previous allograft. Her husband, however, shared antigens present in one of the islet donors and the recipient could have been presensitized to her husband during her two pregnancies. This case clearly demonstrates that islet allografts can lead to development of anti-HLA antibodies, which can cause islet allograft failure, as is the case with solid organ transplants, and hence emphasizes the need to monitor for such antibodies pre- and posttransplant. Additionally it appears that currently recommended immunosuppression may not be sufficient to inhibit a humoral response to both alloantigens and autoantigens.

Islet transplantation: progress and challenge

For over 30 years, investigators have explored islet transplantation as a logical approach to restoring glucose homeostasis in persons with diabetes. Islet transplantation can currently provide improved glycemic control, relief from recurrent severe hypoglycemia, and potentially insulin independence. In this review, we describe details of the evolution of modern islet transplantation and provide insight into ongoing clinical and basic research efforts to overcome current obstacles for this promising therapy.

The Rap-B-Raf signalling pathway is activated by glucose and glucagon-like peptide-1 in human islet cells

AIMS/HYPOTHESIS

Glucose and glucagon-like peptide-1 have been shown to activate extracellular signal-regulated kinase (ERK) and phosphoinositide 3-kinase in beta cells. We examined the contributions of the small GTPases Rap and Ras and the serine-threonine kinases B-Raf and Raf-1 to the activation of these kinases in human islet cells.

METHODS

The expression of Rap, Ras, B-Raf and Raf-1 in human islets was examined by immunohistochemistry and immunoblotting. Human islets were incubated in glucose at concentrations of 2.5 and 15 mmol/l and were stimulated with 10 nmol/l glucagon-like peptide-1. The activation of ERK and Raf kinases was examined by phosphorylation-specific antibodies and immuno-complexed kinase assays. The activation of Rap and Ras was determined by pull-down assays. Stimulation of phosphoinositide 3-kinase was detected by immuno-complexed lipid kinase assays.

RESULTS

Extracellular-regulated kinase and protein kinase B (a downstream target of phosphoinositide 3-kinase) were activated in islets stimulated with glucose and glucagon-like peptide-1. In these islets, the Rap-B-Raf signalling pathway was activated preferentially compared with Ras and Raf-1, and activated Rap and B-Raf mediated ERK stimulation in kinase assays in vitro. In addition, Rap rather than Ras mediated activation of phosphoinositide 3-kinase in islets stimulated with glucose and glucagon-like peptide-1.

CONCLUSIONS/INTERPRETATION

In human islet cells, glucose and glucagon-like peptide-1 activate the Rap and B-Raf signalling module, which mediates ERK activation in assays in vitro. Rap also activates phosphoinositide 3-kinase, delineating central roles for Rap and B-Raf as therapeutic targets for beta cell growth in diabetes mellitus.

Nonhuman primate models in type 1 diabetes research

The recent success of "steroid-free" immunosuppressive protocols and improvements in islet preparation techniques have proven that pancreatic islet transplantation (PIT) is a valid therapeutic approach for patients with type 1 diabetes. However, there are major obstacles to overcome before PIT can become a routine therapeutic procedure, such as the need for chronic immunosuppression, the loss of functional islet mass after transplantation requiring multiple islet infusion to achieve euglycemia without exogenous administration of insulin, and the shortage of human tissue for transplantation. With reference to the first obstacle, stable islet allograft function without immunosuppressive therapy has been achieved after tolerance was induced in diabetic primates. With reference to the second obstacle, different strategies, including gene transfer of antiapoptotic genes, have been used to protect isolated islets before and after transplantation. With reference to the third obstacle, pigs are an attractive islet source because they breed rapidly, there is a long history of porcine insulin use in humans, and there is the potential for genetic engineering. To accomplish islet transplantation, experimental opportunities must be balanced by complementary characteristics of basic mouse and rat models and preclinical large animal models. Well-designed preclinical studies in primates can provide the quality of information required to translate islet transplant research safely into clinical transplantation.

Disseminated periportal fatty degeneration after allogeneic intraportal islet transplantation in a patient with type 1 diabetes mellitus: a case report

Insulin independence after islet transplantation has been significantly improved by using new steroid-free immunosuppressive protocols and increased islet mass. Only little is known about the influence on the morphology of the liver of intraportally transplanted islets. We describe a case of disseminated periportal fatty degeneration after allogeneic intraportal islet transplantation (ITx). A 35-year-old patient with type-1 diabetes mellitus who was suffering from repeated severe hypoglycemic episodes received two sequential intraportal islet grafts. Liver structure was normal before the first ITx, based upon ultrasound and magnetic resonance imaging (MRI). One week after the first ITx, ultrasound demonstrated normal liver morphology. Four months later, at the second ITx, we detected small, disseminated, and hypodense hepatic lesions (1 to 3 mm) by ultrasound, which were confirmed by MRI and interpreted to be fatty degenerations. Histologically we found focal drop-shaped fatty degenerations with signs of mild periportal chronic inflammation. These liver alterations without clinical symptoms or pathological liver function tests matched the predicted distribution of infused islets. Glucose metabolism markedly improved after the first ITx, namely 58.6% reduction of daily insulin requirements, 1.4% decrease in HbA1c, basal C-peptide of 0.8 to 1.3 ng/dl with no severe hypoglycemia. We interpreted these benign changes in liver morphology as reactions to a local hyperinsulinemia in the neighborhood of the transplanted islets. We hypothesized that a steroid-free immunosuppression with rapamycin and tacrolimus may have contributed to changes in the portal microenvironment.

The role of current product release criteria for identification of human islet preparations suitable for clinical transplantation

BACKGROUND

Alloimmunity, autoimmunity, and nonspecific inflammation are known to be potential determinants for long-term islet survival and insulin independence. Sufficient islet mass is a key determinant. But islet engraftment and posttransplant survival may also depend on functional characteristics of the graft. This study investigated the significance of current product release criteria for the transplantation outcome.

METHODS

Fourty five consecutive transplanted human islet preparations and their functional outcomes were analyzed. Islet mass was determined according to standard criteria: purity by light microscopy, viability by dye exclusion and Insulin secretory response to static glucose incubation. Islet graft function was monitored for > or = 1 year. Islet function was defined as full (FF), partial (PF), or nonfunction (NF) based on serum C-peptide levels and insulin independence.

RESULTS

All islet grafts displayed primary function. Islet mass [IEQ/kg BW]: 7331.3 +/- 679.7 (FF), 5821.3 +/- 546.7 (PF), 6468.6 +/- 658.5 (NF), (FF vs PF p = .032) Purity [%] 86.9 +/- 3.1 (FF), 76.0 +/- 2.87 (PF), 88.2 +/- 2.3 (NF) (FF vs PF P =.045, PF vs NF, P = 0.01). (4) Viability [%]:89.2 +/- 2 (FF), 86.2 +/- 1.7 (PF), 87.3 +/- 1.8 (NF) (ns). Stimulation index (SI): 20 +/- 6.3 (FF), 80.2 +/- 28.2 (PF), 21.6 +/- 3.5 (NF) (ns) No correlation was observed between SI and any other parameter nor between SI and C-peptide levels. Islet mass significantly correlated with C-peptide levels at 6 and 12 months after transplantation for functioning grafts.

CONCLUSIONS

Stringent product release criteria allow identification of islet preparations suitable for clinical transplantation. However, currently used parameters are not predictive of long-term graft function, indicating that further refined quality assessments including apoptosis and resistance to early inflammation, are required to assess the primary engrafted islet mass.

Islet transplantation: a realistic alternative for the treatment of insulin deficient diabetes mellitus

Diabetes mellitus is a devastating disease and the WHO [World Health Report, World Health Organization, 2002] (World Health Organization) expects that the number of diabetic patients will increase to 300 million by the year 2025. Type 1 diabetes results from an autoimmune-mediated destruction of the insulin-secreting beta-cells in the islets of Langerhans of the pancreas, whereas Type 2 diabetes is a disease of the older population which is due to systemic insulin resistance and reduced insulin secretion by the pancreatic beta-cells. Surgical resection of the pancreas may also cause insulin-dependent diabetes depending on the size of the remaining pancreas. The long-term complications of diabetes are a direct result of the constantly elevated levels of blood glucose in the absence of an effective insulin treatment. Recent prospective studies such as the diabetes control and complication trial (DCCT) [N. Engl. J. Med. 329 (1993) 977] and the UK prospective diabetes study [Lancet 352 (1998) 837] have convincingly demonstrated that improved blood glucose control in all type diabetes reduces the risk of the development of the secondary complications of diabetes. Despite intensive insulin therapy, most individuals with insulin deficient diabetes are unable to maintain a blood glucose level in the normal range at all times. Therefore, the only way to ensure the long-term health of patients with diabetes is find a way of maintaining constant normoglycemia. It seems logical that the replacement of the islet tissue itself, either by transplanting a vascularized pancreatic allograft or by transplanting purified pancreatic islet cells, offers a better approach than simply replacing insulin that has been lost. In this article, we outline the major achievements made recently in the development of therapeutic islet transplantation applications and offer an explanation as to why islet transplantation seems to be an ideal solution for absolute insulin deficient diabetes.

Insulin-induced normoglycemia reduces islet number needed to achieve normoglycemia after allogeneic islet transplantation in diabetic mice

The Edmonton protocol established that insulin independence could be reached with the transplantation of an appropriate number of islet cells. However, to effect a cure, islets from two or three pancreases are needed. The aim of this study was to examine whether normoglycemia, with insulin treatment before and after transplantation, reduces the islet number needed to achieve normoglycemia in allogeneic islet transplantation. Swiss mice were used as donors and recipients. Diabetes was induced by i.p. administration of streptozotocin (180 mg/kg BW). Diabetic mice were transplanted with 300 (n = 16), 400 (n = 16), or 500 (n = 16) islets under the left kidney capsule. For every group, half the animals were kept normoglycemic with insulin treatment from day 4 before transplantation to day 10 after transplantation. At the end of the study, all normoglycemic mice were given an i.p. glucose tolerance test (IPGTT). For statistical analysis, paired or unpaired Student's t-test or ANOVA was used. Only insulin-treated mice achieved normoglycemia by the end of the study (37.5% of animals transplanted with 400 islets and 50% transplanted with 300 or 500 islets). At the end of the study, normoglycemic mice transplanted with 300 allogeneic islets showed better glycosylated hemoglobin (HbA1C) than did normoglycemic mice transplanted with 500 islets (300 islets: 2.7 +/- 0.2%; 500 islets: 3.6 +/- 0.2%; p < 0.05). After the IPGTT, insulin-treated mice transplanted with 500 islets showed abnormal glucose tolerance; however, insulin-treated mice transplanted with 300 or 400 islets showed normal glucose tolerance. Insulin treatment reduced the islet number needed to achieve normoglycemia in allogeneic islet transplantation. The HbA1C and IPGTT results suggest that transplanting smaller numbers of allogeneic islets improves beta-cell function; some studies suggest that this may be due to lower immunogenicity, hypoxia, and inflammation.

Successful simultaneous islet-kidney transplantation using a steroid-free immunosuppression: two-year follow-up

We report on the feasibility of a glucocorticoid-free immunosuppression (sirolimus, low-dose tacrolimus, and daclizumab) in simultaneous islet-kidney transplantation in nine patients with type 1 diabetes. There was one renal primary nonfunction. Renal function (n = 8) as assessed by creatinine and creatinine clearance over time was 103 +/- 6 micromol/L and 64 +/- 6 mL/min/1.73 m(2), respectively. Five out of six patients with >or= 2 islet transplantations became insulin independent. The mean HbA(1c) during the follow-up period for all patients after transplantation is 6.2 +/- 0.9% as compared with 8.7 +/- 1.9% prior to transplant. These results in patients with a median follow-up of 2.3 years suggest that kidney transplantation under a glucocorticoid-free immunosuppression is feasible, and that the rate of insulin independence of 80% can be achieved not only in patients with no or minimal diabetes complications, but also in patients with more advanced late complications and in conjunction with kidney transplantation.

Beta-cell replacement for type I diabetes

The ability to achieve insulin independence with either solid-organ pancreas or islet transplantation has increased the number of patients seeking beta-cell replacement as an alternative to insulin therapy. Despite dramatic improvements in the ability to achieve insulin independence following solid-organ pancreas transplantation, the secondary complications of long-standing diabetes are frequently irreversible by the time surgical intervention is justified based on the risk of this procedure. Pancreatic islet transplantation provides a safer and less invasive alternative for beta-cell replacement that could be justified earlier in the course of diabetes to prevent the development of secondary complications. Recent advances in the technology of islet isolation, as well as the ability to prevent the alloimmune and recurrent autoimmune response following islet transplantation with immunosuppressive regimens that are not toxic to beta cells, have rekindled an interest in this field. Widespread application of islet transplantation will depend on further improvements in selective immunosuppression, development of immunologic tolerance, and finding new sources of beta cells.

Immunosuppression for pancreatic islet transplantation

Protocols for islet transplantation have to take into account the diabetogenicity/islet toxicity of the immunosuppressive agents, namely corticosteroids and calcineurin inhibitors, most notably tacrolimus. The development by the Edmonton group of a sirolimus-based, steroid-free, low-tacrolimus regimen was a significant breakthrough that allowed the rate of insulin independence after islet transplantation to increase from 13% to 80% at 1 year. Drawbacks include the side effects of sirolimus and the reduction in insulin independence to 50% at 3 years, the latter being attributed to prolonged tacrolimus exposure. Currently explored alternatives to tacrolimus include cyclosporine, mycophenolate mofetil, and the novel agent FTY 720. Perspectives for the near future involve the achievement of "prope tolerance" by strategies using lymphocyte-depleting antibodies (anti-thymocyte globulin, campath-1H, hOKT3gamma1 [ala,ala]), or costimulatory blockade (anti-CD154 mAbs, CTLA4-Ig).

Clinical islet transplant: current and future directions towards tolerance

The ultimate goal of islet transplantation is to completely correct the diabetic state from an unlimited donor source, without the need for chronic immunosuppressive drug therapy. Although islet transplantation provides an opportunity to develop innovative strategies for tolerance in the clinic, both alloimmune and autoimmune barriers must be controlled, if stable graft function is to be maintained long-term. After islet extraction from the pancreas, the cellular graft may be stored in tissue culture or cryopreserved for banking, providing an opportunity not only to optimally condition the recipient but also to allow in vitro immunologic manipulation of the graft before transplantation, unlike solid organ grafts. As such, islets may be considered a "special case." Remarkable progress has occurred in the last three years, with dramatic improvements in outcomes after clinical islet transplantation. The introduction of a steroid-free, sirolimus-based, anti-rejection protocol and islets prepared from two (or rarely three) donors led to high rates of insulin independence. The "Edmonton Protocol" has been successfully replicated by other centers in an international multicenter trial. A number of key refinements in pancreas transportation, processing, purification on non-ficoll-based media, storage of islets in culture for two days and newer immunological conditioning and induction therapies have led to continued advancement through extensive collaboration between key centers. This review outlines the historical development of islet transplantation over the past 30 years, provides an update on current clinical outcomes, and summarizes a series of unique opportunities for development and early testing of tolerance protocols in patients.

Benefits and risks of solitary islet transplantation for type 1 diabetes using steroid-sparing immunosuppression: the National Institutes of Health experience

OBJECTIVE

The aim of this study was to describe the National Institutes of Health's experience initiating an islet isolation and transplantation center, including descriptions of our first six recipients, and lessons learned.

RESEARCH DESIGN AND METHODS

Six females with chronic type 1 diabetes, hypoglycemia unawareness, and no endogenous insulin secretion (undetectable serum C-peptide) were transplanted with allogenic islets procured from brain dead donors. To prevent islet rejection, patients received daclizumab, sirolimus, and tacrolimus.

RESULTS

All patients noted less frequent and less severe hypoglycemia, and one-half were insulin independent at 1 year. Serum C-peptide persists in all but one patient (follow-up 17-22 months), indicating continued islet function. Two major procedure-related complications occurred: partial portal vein thrombosis and intra-abdominal hemorrhage. While we observed no cytomegalovirus infection or malignancy, recipients frequently developed transient mouth ulcers, diarrhea, edema, hypercholesterolemia, weight loss, myelosuppression, and other symptoms. Three patients discontinued immunosuppressive therapy: two because of intolerable toxicity (deteriorating kidney function and sirolimus-induced pneumonitis) while having evidence for continued islet function (one was insulin independent) and one because of gradually disappearing islet function.

CONCLUSIONS

We established an islet isolation and transplantation program and achieved a 50% insulin-independence rate after at most two islet infusions. Our experience demonstrates that centers not previously engaged in islet transplantation can initiate a program, and our data and literature analysis support not only the promise of islet transplantation but also its remaining hurdles, which include the limited islet supply, procedure-associated complications, imperfect immunosuppressive regimens, suboptimal glycemia control, and loss of function over time.

Islet autotransplantation after left pancreatectomy for non-enucleable insulinoma

Insulinoma is a rare, almost always benign endocrine tumor of the pancreas, clinically characterized by hyperinsulinemic, hypoglycemic episodes. Surgical excision is the therapy of choice, which may lead to postpancreatectomy diabetes mellitus in the case of extensive pancreatic resection. We present the cases and the metabolic follow up of two patients, 81 and 73 years old, with insulinoma localized close to the main duct in the pancreatic neck. Both patients underwent an 80% left pancreatectomy, avoiding a pancreatico-enteric anastomosis. In order to prevent postpancreatectomy diabetes, the islets from the tumor-free part of the resected pancreas were isolated and injected via a right colic vein into the portal system. After a follow up of 6 and 3 years respectively, both patients remained insulin-independent without any dietary restrictions. Fasting and glucagon-stimulated C-peptide-levels and glycosylated hemoglobin remained within normal range. There were no signs of recurrent insulinoma. Liver biopsy performed in one patient at 1 year after autotransplantation, showed intact, insulin-producing islets within the portal spaces. In conclusion, autologous islet transplantation can preserve the insulin secretory reserve after extended left pancreatectomy for the treatment of benign tumors in the pancreatic neck.

Pancreatic Islet Cell Transplantation

Pancreatic islet cell transplantation as a treatment for diabetes has hitherto been confined to small patient cohorts with limited success. This article summarizes the results of islet cell transplantation before and after the advent of the new 'Edmonton protocol' of immunosuppression and management of the donor pancreas. Adopting this regimen has achieved unprecedented success and renewed interest in this potential cure for diabetes. Central to recent improvements in the technique has been the transplantation of an adequate islet mass. Improved methods to procure, isolate, and purify islets for clinical use are now being adopted as a new 'gold standard'. The use of new immunosuppressive drugs has further improved clinical results. Corticosteroid sparing-based regimens, and agents such as humanized monoclonal antibodies, are likely to form the mainstay of immunosuppressive protocols with the aim of achieving donor-specific tolerance. Alternative sources of islet cells are also required to expand the technique in an era of reduced numbers of donor pancreata. Manipulation of stem cells and xenotransplantation may yet yield sufficient islets to overcome the problem of donor shortage. Islet cell transplantation now forms the basis of a prospective multicenter trial under the aegis of the Immune Tolerance Network. The results of this are awaited, but it appears that islet cell transplantation may yet emerge as an effective treatment option for some members of the diabetic population.

Defining optimal immunosuppression for islet transplantation based on reduced diabetogenicity in canine islet autografts

BACKGROUND

The recent results of clinical islet transplantation have improved substantially with the introduction of a more potent but less diabetogenic immunosuppressant protocol. The successful development of this protocol was based in part on the outcomes of studies reported herein, addressing the diabetogenic potential of a series of immunosuppressant agents used alone or in combination in a canine islet autograft model. Although it is recognized that failure to achieve long-term insulin independence in human islet allotransplantation has been multifactorial, with low engraftment mass, acute or chronic rejection, autoimmune recurrence, loss of islet-acinar integrity, heterotopic site, denervation, and insulin resistance all being implicated to varying degrees, avoidance of diabetogenic immunosuppression has been pivotal to the enhanced outcomes of clinical islet transplantation. We here explore the effects of clinically relevant doses of cyclosporine or tacrolimus when given alone or in combination with glucocorticoids on long-term canine islet autograft function.

METHOD

Dogs (n=8) underwent total pancreatectomy, islet isolation, and intrasplenic autotransplantation and were normoglycemic with stable long-term graft function 3 months to 8 years posttransplant. The frequently sampled intravenous glucose tolerance test (FSIGT) was performed predrug (baseline), at 1 month of therapy (on drug), and again 1 month after withdrawal of therapy (postdrug).

RESULTS

Monotherapy treatments with low- or high-dose prednisone, Neoral, or tacrolimus had minimal impact on islet autograft function. The combination of Neoral and prednisone led to a marked impairment in glucose decay (25% decline from 1.77+/-0.2 to 1.24+/-0.2, P<0.05), without significant change in insulin responsiveness or glucose effectiveness. However, insulin sensitivity was markedly impaired while on therapy (7.10+/-1.2 to 3.10+/-0.5, P<0.01). Importantly, glucose decay and insulin sensitivity failed to return to baseline after withdrawal of therapy. The combination of tacrolimus and glucocorticoids led to permanent and irreversible diabetes in all recipients (n=6, P<0.001). Similar treatment of healthy control dogs led to a 44% decrease in glucose decay (P<0.01).

CONCLUSIONS

Immunosuppression must be specifically tailored for islet transplantation and be glucocorticoid free if insulin independence is to be sustained clinically.

First human trial of pancreatic islet allo-transplantation in Korea--focus on re-transplantation

Over the past 20 years, allo-transplantation of islet or whole pancreas for reaching and sustaining near-normoglycemia, as close as possible to the physiological model, have been undertaken. As previously known, even though islet transplantation is possible as a safe re-transplant, it is not well known whether re-transplantation of islets is suitable for patients who have lost the grafted islet function. We have performed a human islet allo-transplantation and re-transplantation on an IDDM patient for the first time in Asia and Korea. The recipient was a 32-year-old male and his insulin requirement was 75-85 U per day. After islet transplantation, the basal C-peptide increased from 0.6 to 2.1 ng/ml and insulin requirement decreased from 80 to 36 U per day, indicating that the grafted islets were functional. However, the grafted islets lost function 70 days after the transplantation. So, we performed re-transplantation of the islets. After the re-transplantation, the glucose profile became more stable and frequent episodes of severe hypoglycemia completely disappeared. His severe neuropathic pain improved dramatically and he could engage his ordinary daily life without any antineuropathic drugs. The success of this re-transplantation is one step closer to becoming a viable alternative for the millions of individuals who are suffering from diabetes.

Molecular detection of circulating beta-cells after islet transplantation

Islet transplantation is a promising treatment for type 1 diabetes. However, islet grafts are submitted to multiple injuries, including immunosuppressive drug toxicity, hyperglycemia, hypoxia, unspecific inflammatory reactions, as well as allo- and autoimmune destruction. Therapeutic approaches to these damage mechanisms require early detection of islet injury, which is currently not feasible because of the lack of efficient markers. Based on the hypothesis of islet dissociation and release of islet cells into the circulation during islet injury, we designed a highly sensitive and specific molecular assay, able to detect two beta-cells per milliliter of venous blood by RT-PCR of insulin mRNA. We report that circulating beta-cells can be demonstrated up to 10 weeks after intraportal islet transplantation, as assessed after six islet grafts in four type 1 diabetic patients. Furthermore, our results suggest that the time during which circulating islet cells can be detected may depend on the graft environment and the immunosuppressive regimen. This test may allow better estimation of islet cell loss and identification of factors involved in islet graft injury.