Long-term graft function after allogeneic islet transplantation

Ten-year outcomes of islet transplantation in patients with type 1 diabetes: Data from the Swiss-French GRAGIL network

To describe the 10-year outcomes of islet transplantation within the Swiss-French GRAGIL Network, in patients with type 1 diabetes experiencing high glucose variability associated with severe hypoglycemia and/or with functional kidney graft. We conducted a retrospective analysis of all subjects transplanted in the GRAGIL-1c and GARGIL-2 islet transplantation trials and analyzed components of metabolic control, graft function and safety outcomes over the 10-year period of follow-up. Forty-four patients were included between September 2003 and April 2010. Thirty-one patients completed a 10-year follow-up. Ten years after islet transplantation, median HbA1c was 7.2% (6.2-8.0) (55 mmol/mol [44-64]) versus 8.0% (7.1-9.1) (64 mmol/mol [54-76]) before transplantation (p < .001). Seventeen of 23 (73.9%) recipients were free of severe hypoglycemia, 1/21 patients (4.8%) was insulin-independent and median C-peptide was 0.6 ng/ml (0.2-1.2). Insulin requirements (UI/kg/day) were 0.3 (0.1-0.5) versus 0.5 (0.4-0.6) before transplantation (p < .001). Median (IQR) β-score was 1 (0-4) (p < .05 when comparing with pre-transplantation values) and 51.9% recipients had a functional islet graft at 10 years. With a 10-year follow-up in a multicentric network, islet transplantation provided sustained improvement of glycemic control and was efficient to prevent severe hypoglycemia in almost 75% of the recipients.

Ten-Year Outcome of Islet Alone or Islet After Kidney Transplantation in Type 1 Diabetes: A Prospective Parallel-Arm Cohort Study

OBJECTIVE

The long-term outcome of allogenic islet transplantation is unknown. The aim of this study was to evaluate the 10-year outcome of islet transplantation in patients with type 1 diabetes and hypoglycemia unawareness and/or a functioning kidney graft.

RESEARCH DESIGN AND METHODS

We enrolled in this prospective parallel-arm cohort study 28 subjects with type 1 diabetes who received islet transplantation either alone (ITA) or after a kidney graft (IAK). Islet transplantation consisted of two or three intraportal infusions of allogenic islets administered within (median [interquartile range]) 68 days (43-92). Immunosuppression was induced with interleukin-2 receptor antibodies and maintained with sirolimus and tacrolimus. The primary outcome was insulin independence with A1C ≤6.5% (48 mmol/mol). Secondary outcomes were patient and graft survival, severe hypoglycemic events (SHEs), metabolic control, and renal function.

RESULTS

The primary outcome was met by (Kaplan-Meier estimates [95% CI]) 39% (22-57) and 28% (13-45) of patients 5 and 10 years after islet transplantation, respectively. Graft function persisted in 82% (62-92) and 78% (57-89) of case subjects after 5 and 10 years, respectively, and was associated with improved glucose control, reduced need for exogenous insulin, and a marked decrease of SHEs. ITA and IAK had similar outcomes. Primary graft function, evaluated 1 month after the last islet infusion, was significantly associated with the duration of graft function and insulin independence.

CONCLUSIONS

Islet transplantation with the Edmonton protocol can provide 10-year markedly improved metabolic control without SHEs in three-quarters of patients with type 1 diabetes, kidney transplanted or not.

Developing a Rapid Algorithm to Enable Rapid Characterization of Alginate Microcapsules

The islets of Langerhans are endocrine tissue clusters that secrete hormones that regulate the body's glucose, carbohydrate, and fat metabolism, the most important of which is insulin, a hormone secreted by β-cells within the islets. In certain instances, a person's own immune system attacks and destroys them, leading to the development of type 1 diabetes (T1D), a life-long condition that needs daily insulin administration to maintain health and prolong survival. Islet transplantation is a surgical procedure that has demonstrated the ability to normalize blood sugar levels for up to a few years, but the need for chronic immunosuppression relegates it to a last resort that is often only used sparingly and in seriously ill patients. Islet microencapsulation is a biomedical innovation designed to protect islets from the immune system by coating them with a biocompatible polymer, and this new technology has demonstrated various degrees of success in small- and large-animal studies. This success is significantly impacted by microcapsule morphology and encapsulation efficiency. Since hundreds of thousands of microcapsules are generated during the process, characterization of encapsulated islets without the help of some degree of automation would be difficult, time-consuming, and error prone due to inherent observer bias. We have developed an image analysis algorithm that can analyze hundreds of microencapsulated islets and characterize their size, shape, circularity, and distortion with minimal observer bias. This algorithm can be easily adapted to similar nano- or microencapsulation technologies to implement stricter quality control and improve biomaterial device design and success.

Human islet function following 20 years of cryogenic biobanking

AIMS/HYPOTHESIS

There are potential advantages to the low-temperature (-196 °C) banking of isolated islets, including the maintenance of viable islets for future research. We therefore assessed the in vitro and in vivo function of islets cryopreserved for nearly 20 years.

METHODS

Human islets were cryopreserved from 1991 to 2001 and thawed between 2012 and 2014. These were characterised by immunostaining, patch-clamp electrophysiology, insulin secretion, transcriptome analysis and transplantation into a streptozotocin (STZ)-induced mouse model of diabetes.

RESULTS

The cryopreservation time was 17.6 ± 0.4 years (n = 43). The thawed islets stained positive with dithizone, contained insulin-positive and glucagon-positive cells, and displayed levels of apoptosis and transcriptome profiles similar to those of freshly isolated islets, although their insulin content was lower. The cryopreserved beta cells possessed ion channels and exocytotic responses identical to those of freshly isolated beta cells. Cells from a subset of five donors demonstrated similar perifusion insulin secretion profiles pre- and post-cryopreservation. The transplantation of cryopreserved islets into the diabetic mice improved their glucose tolerance but did not completely normalise their blood glucose levels. Circulating human insulin and insulin-positive grafts were detectable at 10 weeks post-transplantation.

CONCLUSIONS/INTERPRETATION

We have demonstrated the potential for long-term banking of human islets for research, which could enable the use of tissue from a large number of donors with future technologies to gain new insight into diabetes.

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

BACKGROUND

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

METHODS

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

RESULTS

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

CONCLUSION

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

Pancreatic islet cell transplantation: an update

Transplantation of pancreatic islets, as a therapeutic modality for type 1 diabetes mellitus (T1DM), at this stage of its development, is reserved for patients with severe glycemic variability, progressive diabetic complications, and life threatening hypoglycemia unawareness, regardless of intensive insulin management. It has not succeeded to become the method of choice for treating T1DM because of limited supply and suboptimal yields of procurement and isolation of islets, graft failure, and relatively high requirements, i.e., at least 10,000 functional Islet Equivalents per kg of patient weight, to achieve prolonged insulin independence and glucose stability. Efforts aimed at making islet transplantation a competitive alternative to exogenous insulin injections for treating T1DM have focused on improving the longevity and functionality of islet cells. In order to succeed, these efforts need to be complemented by others to optimize the rate and efficiency of encapsulation.

Outcome of adrenal tissue fragments allotransplantation: the impact of cryopreservation

Cryopreservation is thought to have the potential to preserve tissue for transplantation. In addition, it can also be used for decreasing tissue immunogenicity, which might be important for prolonging allograft survival. In the present study we examined the impact of cryopreservation at various cooling rates on the outcome of allotransplantation of murine adrenal tissue fragments (ATFr). ATFr were cryopreserved with a cooling rate at 1; 10; 40 and more than 100 °C/min. After thawing it was found that the number of the cells expressing markers of dendritic cells (CD11c) and macrophages (CD11b) in the suspension obtained from ATFr decreased with increasing cooling rate. After allotransplantation the survival rates of adrenalectomized mice and the blood serum levels of corticosterone were higher in recipients of cryopreserved ATFr. By immunohistochemistry, cryopreserved allografts displayed a decreased infiltration by CD4+ and CD8+ T-lymphocytes as compared to fresh grafts. These findings suggest that cryopreserved allografts cause a less severe rejection by decreasing graft immunogenicity.

Islets transplanted in immunoisolation devices: a review of the progress and the challenges that remain

The concept of using an immunoisolation device to facilitate the transplantation of islets without the need for immunosuppression has been around for more than 50 yr. Significant progress has been made in developing suitable materials that satisfy the need for biocompatibility, durability, and permselectivity. However, the search is ongoing for a device that allows sufficient oxygen transfer while maintaining a barrier to immune cells and preventing rejection of the transplanted tissue. Separating the islets from the rich blood supply in the native pancreas takes its toll. The immunoisolated islets commonly suffer from hypoxia and necrosis, which in turn triggers a host immune response. Efforts have been made to improve the supply of nutrients by using proangiogenic factors to augment the development of a vascular supply in the transplant site, by using small islet cell aggregates to reduce the barrier to diffusion of oxygen, or by creating scaffolds that are in close proximity to a vascular network such as the omental blood supply. Even if these efforts are successful, the shortage of donor islet tissue available for transplantation remains a major problem. To this end, a search for a renewable source of insulin-producing cells is ongoing; whether these will come from adult or embryonic stem cells or xenogeneic sources remains to be seen. Herein we will review the above issues and chart the progress made with various immunoisolation devices in small and large animal models and the small number of clinical trials carried out to date.

Evolution of β-Cell Replacement Therapy in Diabetes Mellitus: Islet Cell Transplantation

Diabetes mellitus remains one of the leading causes of morbidity and mortality worldwide. According to the Centers for Disease Control and Prevention, approximately 23.6 million people in the United States are affected. Of these individuals, 5 to 10% have been diagnosed with Type 1 diabetes mellitus (T1DM), an autoimmune disease. Although it often appears in childhood, T1DM may manifest at any age, leading to significant morbidity and decreased quality of life. Since the 1960s, the surgical treatment for diabetes mellitus has evolved to become a viable alternative to insulin administration, beginning with pancreatic transplantation. While islet cell transplantation has emerged as another potential alternative, its role in the treatment of T1DM remains to be solidified as research continues to establish it as a truly viable alternative for achieving insulin independence. In this paper, the historical evolution, procurement, current status, benefits, risks, and ongoing research of islet cell transplantation are explored.

Assessment of human islet labeling with clinical grade iron nanoparticles prior to transplantation for graft monitoring by MRI

Ex vivo labeling of islets with superparamagnetic iron oxide (SPIO) nanoparticles allows posttransplant MRI imaging of the graft. In the present study, we compare two clinical grade SPIOs (ferucarbotran and ferumoxide) in terms of toxicity, islet cellular uptake, and MRI imaging. Human islets (80-90% purity) were incubated for 24 h with various concentrations of SPIOs (14-280 μg/ml of iron). Static incubations were performed, comparing insulin response to basal (2.8 mM) or high glucose stimulation (16.7 mM), with or without cAMP stimulation. Insulin and Perl's (assessment of iron content) staining were performed. Electronic microscopy analysis was performed. Labeled islets were used for in vitro or in vivo imaging in MRI 1.5T. Liver section after organ removal was performed in the same plane as MRI imaging to get a correlation between histology and radiology. Postlabeling islet viability (80 ± 10%) and function (in vitro static incubation and in vivo engraftment of human islets in nude mice) were similar in both groups. Iron uptake assessed by electron microscopy showed iron inclusions within the islets with ferucarbotran, but not with ferumoxide. MRI imaging (1.5T) of phantoms and of human islets transplanted in rats, demonstrated a strong signal with ferucarbotran, but only a weak signal with ferumoxide. Signal persisted for >8 weeks in the absence of rejection. An excellent correlation was observed between radiologic images and histology. The hepatic clearance of intraportally injected ferucarbotran was faster than that of ferumoxide, generating less background. A rapid signal decrease was observed in rejecting xenogeneic islets. According to the present data, ferucarbotran is the most appropriate of available clinical grade SPIOs for human islet imaging.

Bilirubin Promotes De Novo Generation of T Regulatory Cells

We have previously demonstrated that bilirubin administration to the recipient induces tolerance towards islet cell transplants across a complete MHC mismatch in a mouse model. Here we assess the mechanisms of such protection. Bilirubin treatment of recipients improved function of islet allografts by suppressing expressions of proinflammatory and proapoptotic genes in those islets and by increasing Foxp3+ T regulatory (Treg) cells at the site of transplanted islets at various days after transplantation. No prolongation of graft survival was observed in recipients treated with bilirubin when CD4+CD25+ T cells were predepleted from those recipients, indicating that Treg cells are necessary for the protective effect of bilirubin. Adoptive transfer of Treg cells from tolerant mice into Rag1-/- recipients resulted in long-term acceptance of skin allografts in an alloantigen-specific manner, suggesting that Treg cells are sufficient to induce tolerance. In addition, bilirubin treatment promoted de novo generation of Treg cells in Rag1-/- recipients. Thus, bilirubin treatment to the recipients prolongs islet allograft survival via a Treg-dependent manner in which CD4+CD25+ Treg cells are both necessary and sufficient for tolerance induction and graft acceptance. Bilirubin treatment promotes de novo generation of Treg cells that might account for the protective effects of bilirubin given to recipients.

Comparative study of the cellular pharmacodynamics of calcineurin inhibitors between patients with chronic renal failure awaiting renal transplantation and cirrhosis patients awaiting liver transplantation

The in vitro response of peripheral blood mononuclear cells (PBMCs) to the suppressive effects of calcineurin inhibitors is known to correlate with the clinical efficacy of drugs used in renal transplantations. The present study was conducted to examine the differences of PBMC responses to calcineurin inhibitors between chronic renal failure (CRF) patients awaiting renal transplantation and cirrhosis patients awaiting liver transplantation. The study included 99 CRF patients awaiting renal transplantation and 27 cirrhosis patients awaiting liver transplantation. Twenty milliliters of venous blood was taken 1-7 days before transplantation. The in vitro drug concentrations giving 50% inhibition of PBMC blastogenesis stimulated with concanavalin A (IC(50)s) were calculated. The suppressive effects of tacrolimus against PBMC blastogenesis were more than 10-100 times stronger than those of cyclosporine. The median IC(50) value for cyclosporine against the CRF PBMCs was not significantly different from the median IC(50) value against the cirrhosis PBMCs. In contrast, tacrolimus sensitivity in cirrhosis PBMCs is approximately seven times higher than that in CRF PBMCs. The median IC(50) value for tacrolimus against cirrhosis PBMCs was significantly lower and therefore the effect was stronger in comparison to the CRF PBMCs (p < 0.001). These data suggest that the PBMCs of cirrhosis patients, in comparison to those of CRF patients, are highly sensitive to the suppressive effect of tacrolimus. However, PBMC sensitivity to cyclosporine was not significantly different between the CRF and cirrhosis patients. These observations raise the possibility that treatment with tacrolimus, rather than cyclosporine, may therefore be a better choice to reduce the risks of allograft rejection in liver transplantation.

Progress towards the clinical use of CD3 monoclonal antibodies in the treatment of autoimmunity

PURPOSE OF REVIEW

A major problem in the field of clinical transplantation, as well as in autoimmunity, is that conventional treatments rely on chronic immunosuppression that is not specific for the antigens involved and that increases the risk of infections and tumours. A major need and challenge is, therefore, to achieve 'operational tolerance', namely an inhibition of pathogenic responses in the absence of chronic immunosuppression.

RECENT FINDINGS

Here we review data showing that monoclonal antibodies to the CD3 complex, the signal transducing element of the T cell receptor, promote immune tolerance. This strategy has been the matter of extensive experimental studies in models of autoimmunity and has recently led to a successful clinical translation.

SUMMARY

Results from controlled trials in autoimmune insulin-dependent diabetes showed that CD3 monoclonal antibodies afford long-term effects following a short administration. The present challenge is to build on these results, first, to set the use of CD3 monoclonal antibodies as an established therapy in well selected subsets of patients with autoimmunity, and second, given the similarities of immune mechanisms underlying T cell-mediated autoimmune diseases and allograft rejection, to address if and how this therapeutic strategy could be extended to organ transplantation in the not-too-distant future.

Comparison of the portal vein and kidney subcapsule as sites for primate islet autotransplantation

To date, the portal vein has been the primary site for clinical islet transplantation. Despite success, potential complications such as portal vein thrombosis still exist. The kidney subcapsule has been used successfully in rodent models of islet transplantation. We hypothesized that the kidney subcapsule as a site for islet transplantation in the nonhuman primate model would be as effective as the portal vein. Diabetes was induced in the primate Macaca fascicularis via a total pancreatectomy. Animals were kept under anesthesia during the isolation procedure. Islet isolation was performed using intraductal infusion with Liberase HI and mechanical digestion in the Ricordi chamber, and were purified using a continuous Ficoll gradient. Purified islets were autotransplanted either into the portal vein (n = 6) or the left kidney subcapsule (n = 5) of pancreatectomized animals. Intravenous glucose tolerance tests were performed prior to pancreatectomy and 10 days following transplantation. Three animals underwent pancreatectomy and served as diabetic controls. Of the six animals receiving islets in the portal vein, one developed portal vein thrombosis. All remaining autotransplanted animals in this group remained normoglycemic with glucose-induced insulin secretion that was not different from that prior to pancreatectomy. Of the five animals undergoing transplantation into the kidney subcapsule, only one maintained normoglycemia and elicited insulin secretion in response to glucose stimulation. The other four animals remained hyperglycemic. We conclude that the portal vein is superior to the kidney subcapsule as a site for islet transplantation in nonhuman primates 10 days posttransplantation.

Clinical Significance of the Cellular Pharmacodynamics of Tacrolimus in Living-Donor Liver Transplantation

Successful immunosuppressive therapy is critical for liver transplantation; however, a considerable number of patients experience fatal rejection or alternatively exhibit serious infection resulting from excessive immunosuppression. The in vitro tacrolimus response of peripheral blood mononuclear cells (PBMCs) before transplantation was compared to the clinical outcome up to 4 weeks after operation in 28 living-donor liver transplant recipients treated with tacrolimus. The tacrolimus IC50 values against concanavalin A-induced PBMC blastogenesis in vitro were calculated. These recipients were classified into two groups with the mean tacrolimus IC50 (0.18 ng/ml) as the cutoff point, after which the clinical outcome between the patient groups was compared. The allograft rejection incidence in the low-sensitivity group (IC50 < 0.18 ng/ml; n = 16) was 6/12 (50.0%), which was significantly higher than the incidence of 2/16 (12.5%) in the high-sensitivity group (IC50 > 0.18 ng/ml; n = 12) ( p = 0.0297). In contrast, the infection incidence in the high-sensitivity group was 6/16 (37.5%), which was significantly higher than that of the low-sensitivity group (1/12; 8.3%) ( p = 0.0401). These data suggest that patients exhibiting a low PBMC sensitivity to tacrolimus have a risk of rejection, whereas highly sensitive patients have a risk of infection in living-donor liver transplantations under tacrolimus therapy.

A novel human stem cell coculture system that maintains the survival and function of culture islet-like cell clusters

Islet-like cell clusters (ICCs) have been suggested to be a source of insulin-producing tissue for xenotransplantation in type 1 diabetes. We designed an approach to maintain the cultured rat pancreatic ICC survival and function, when cocultured with human umbilical cord mesenchymal stem cells (HUMSCs). HUMSCs in coculture have the ability to maintain ICC survival and function, for which number and insulin secretion of ICCs are increasing and lasting for 3 months, while ICCs gradually crash, which results in cell death after a period of 12 days of culture without HUMSCs. Cytokine protein array showed it has more than a twofold increase in levels of several cytokines (interleukin-6, tissue inhibitor of metalloproteinases-1, tissue inhibitor of metalloproteinases-2, monocyte chemoattractant protein-1, growth related oncogene, hepatocyte growth factor, insulin-like growth factor binding proteins 4, and interleukin-8) on coculture medium, implying an important role of these cytokines in this coculture system. These findings suggest that coculture with HUMSCs may have a significant potential to protect ICCs from damage during culture, and may be employed in a novel culture approach to maintain islet cell survival and function before transplantation.

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.