Long-Term Follow-Up of the Edmonton Protocol of Islet Transplantation in the United States

Innovations in bio-engineering and cell-based approaches to address immunological challenges in islet transplantation

Human allogeneic pancreatic islet transplantation is a life-changing treatment for patients with severe Type 1 Diabetes (T1D) who suffer from hypoglycemia unawareness and high risk of severe hypoglycemia. However, intensive immunosuppression is required to prevent immune rejection of the graft, that may in turn lead to undesirable side effects such as toxicity to the islet cells, kidney toxicity, occurrence of opportunistic infections, and malignancies. The shortage of cadaveric human islet donors further limits islet transplantation as a treatment option for widespread adoption. Alternatively, porcine islets have been considered as another source of insulin-secreting cells for transplantation in T1D patients, though xeno-transplants raise concerns over the risk of endogenous retrovirus transmission and immunological incompatibility. As a result, technological advancements have been made to protect transplanted islets from immune rejection and inflammation, ideally in the absence of chronic immunosuppression, to improve the outcomes and accessibility of allogeneic islet cell replacement therapies. These include the use of microencapsulation or macroencapsulation devices designed to provide an immunoprotective environment using a cell-impermeable layer, preventing immune cell attack of the transplanted cells. Other up and coming advancements are based on the use of stem cells as the starting source material for generating islet cells 'on-demand'. These starting stem cell sources include human induced pluripotent stem cells (hiPSCs) that have been genetically engineered to avoid the host immune response, curated HLA-selected donor hiPSCs that can be matched with recipients within a given population, and multipotent stem cells with natural immune privilege properties. These strategies are developed to provide an immune-evasive cell resource for allogeneic cell therapy. This review will summarize the immunological challenges facing islet transplantation and highlight recent bio-engineering and cell-based approaches aimed at avoiding immune rejection, to improve the accessibility of islet cell therapy and enhance treatment outcomes. Better understanding of the different approaches and their limitations can guide future research endeavors towards developing more comprehensive and targeted strategies for creating a more tolerogenic microenvironment, and improve the effectiveness and sustainability of islet transplantation to benefit more patients.

Could Transplantation into the Thyroid Gland Benefit Pancreatic Islet Grafting in Unstable Type 1 Diabetes (T1DM), Complicated Type 2 Diabetes (T2DM), and Patients with Total Pancreatectomy?

BACKGROUND

Insular allograft for unstable type 1 diabetes and autograft in pancreatectomy patients are nowadays considered established procedures with precise indications and predictable outcomes. The clinical outcome of islet transplantation is similar to that of pancreas transplantation, avoiding the complications associated with organ transplantation.

OBJECTIVE

We hypothesised that transplantation of islets of Langerhans within an endocrine organ could better promote their engraftment and function. This could help to resolve or ameliorate known pathological conditions such as unstable type 1 diabetes and complicated type 2 diabetes.

RATIONALE

Pancreatic islet transplantation is currently performed almost exclusively in the liver. The liver provides a sufficiently favourable environment, although not entirely. The hepatic parenchyma has a lower oxygen tension than the pancreatic parenchyma and the vascular structure of the liver is not typical of an exclusively endocrine organ. Moreover, islet transplantation into the liver is not without complications, including hematoma or portal vein thrombosis.

PROPOSED PROJECT

The thyroid gland is the endocrine gland proposed as a 'container'. In fact, it has all the characteristics of 'physio-compatibility' which can address the objectives assumed. It is indeed an ideal site because it is an easily accessible anatomical site that allows islets to be implanted using ultrasound-guided transcutaneous inoculation technique. Moreover, it has physiological and anatomical endocrine affinities with pancreatic islets and, if necessary, it can be removed, using hormone supplementation or replacement therapy.

CONCLUSIONS

The thyroid gland may be proposed as an ideal site for islet implantation due to its anatomical and physiocompatibility characteristics.

Encapsulation and immune protection for type 1 diabetes cell therapy

Type 1 Diabetes (T1D) involves the autoimmune destruction of insulin-producing β-cells in the pancreas. Exogenous insulin injections are the current therapy but are user-dependent and cannot fully recapitulate physiological insulin secretion dynamics. Since the emergence of allogeneic cell therapy for T1D, the Edmonton Protocol has been the most promising immunosuppression protocol for cadaveric islet transplantation, but the lack of donor islets, poor cell engraftment, and required chronic immunosuppression have limited its application as a therapy for T1D. Encapsulation in biomaterials on the nano-, micro-, and macro-scale offers the potential to integrate islets with the host and protect them from immune responses. This method can be applied to different cell types, including cadaveric, porcine, and stem cell-derived islets, mitigating the issue of a lack of donor cells. This review covers progress in the efforts to integrate insulin-producing cells from multiple sources to T1D patients as a form of cell therapy.

Thyroid Hormone Levels Correlate With the Maturation of Implanted Pancreatic Endoderm Cells in Patients With Type 1 Diabetes

BACKGROUND

Macroencapsulated pancreatic endoderm cells (PECs) can reverse diabetes in rodents and preclinical studies revealed that thyroid hormones in vitro and in vivo bias PECs to differentiate into insulin-producing cells. In an ongoing clinical trial, PECs implanted in macroencapsulation devices into patients with type 1 diabetes were safe but yielded heterogeneous outcomes. Though most patients developed meal responsive C-peptide, levels were heterogeneous and explanted grafts had variable numbers of surviving cells with variable distribution of endocrine cells.

METHODS

We measured circulating triiodothyronine and thyroxine levels in all patients treated at 1 of the 7 sites of the ongoing clinical trial and determined if thyroid hormone levels were associated with the C-peptide or glucagon levels and cell fate of implanted PECs.

RESULTS

Both triiodothyronine and thyroxine levels were significantly associated with the proportion of cells that adopted an insulin-producing fate with a mature phenotype. Thyroid hormone levels were inversely correlated to circulating glucagon levels after implantation, suggesting that thyroid hormones lead PECs to favor an insulin-producing fate over a glucagon-producing fate. In mice, hyperthyroidism led to more rapid maturation of PECs into insulin-producing cells similar in phenotype to PECs in euthyroid mice.

CONCLUSION

These data highlight the relevance of thyroid hormones in the context of PEC therapy in patients with type 1 diabetes and suggest that a thyroid hormone adjuvant therapy may optimize cell outcomes in some PEC recipients.

A bioengineered artificial interstitium supports long-term islet xenograft survival in nonhuman primates without immunosuppression

Cell-based therapies hold promise for many chronic conditions; however, the continued need for immunosuppression along with challenges in replacing cells to improve durability or retrieving cells for safety are major obstacles. We subcutaneously implanted a device engineered to exploit the innate transcapillary hydrostatic and colloid osmotic pressure generating ultrafiltrate to mimic interstitium. Long-term stable accumulation of ultrafiltrate was achieved in both rodents and nonhuman primates (NHPs) that was chemically similar to serum and achieved capillary blood oxygen concentration. The majority of adult pig islet grafts transplanted in non-immunosuppressed NHPs resulted in xenograft survival >100 days. Stable cytokine levels, normal neutrophil to lymphocyte ratio, and a lack of immune cell infiltration demonstrated successful immunoprotection and averted typical systemic changes related to xenograft transplant, especially inflammation. This approach eliminates the need for immunosuppression and permits percutaneous access for loading, reloading, biopsy, and recovery to de-risk the use of "unlimited" xenogeneic cell sources to realize widespread clinical translation of cell-based therapies.

A Supportive Role of Mesenchymal Stem Cells on Insulin-Producing Langerhans Islets with a Specific Emphasis on The Secretome

Type 1 Diabetes (T1D) is a chronic autoimmune disease characterized by a gradual destruction of insulin-producing β-cells in the endocrine pancreas due to innate and specific immune responses, leading to impaired glucose homeostasis. T1D patients usually require regular insulin injections after meals to maintain normal serum glucose levels. In severe cases, pancreas or Langerhans islet transplantation can assist in reaching a sufficient β-mass to normalize glucose homeostasis. The latter procedure is limited because of low donor availability, high islet loss, and immune rejection. There is still a need to develop new technologies to improve islet survival and implantation and to keep the islets functional. Mesenchymal stem cells (MSCs) are multipotent non-hematopoietic progenitor cells with high plasticity that can support human pancreatic islet function both in vitro and in vivo and islet co-transplantation with MSCs is more effective than islet transplantation alone in attenuating diabetes progression. The beneficial effect of MSCs on islet function is due to a combined effect on angiogenesis, suppression of immune responses, and secretion of growth factors essential for islet survival and function. In this review, various aspects of MSCs related to islet function and diabetes are described.

Developments in stem cell-derived islet replacement therapy for treating type 1 diabetes

The generation of islet-like endocrine clusters from human pluripotent stem cells (hPSCs) has the potential to provide an unlimited source of insulin-producing β cells for the treatment of diabetes. In order for this cell therapy to become widely adopted, highly functional and well-characterized stem cell-derived islets (SC-islets) need to be manufactured at scale. Furthermore, successful SC-islet replacement strategies should prevent significant cell loss immediately following transplantation and avoid long-term immune rejection. This review highlights the most recent advances in the generation and characterization of highly functional SC-islets as well as strategies to ensure graft viability and safety after transplantation.

Whole-Organ Pancreas and Islets Transplantations in UK: An Overview and Future Directions

Whole-organ pancreas and islets transplantations are two therapeutic options to treat type 1 diabetic patients resistant to optimised medical treatment in whom severe complications develop. Selection of the best option for β-cell replacement depends on several factors such as kidney function, patient comorbidities, and treatment goals. For a patient with end-stage kidney disease, the treatment of choice is often a simultaneous transplant of the pancreas and kidney (SPK). However, it remains a major surgical procedure in patients with multiple comorbidities and therefore it is important to select those who will benefit from it. Additionally, in view of the organ shortage, new strategies to improve outcomes and reduce immune reactions have been developed, including dynamic organ perfusion technologies, pancreas bioengineering, and stem cell therapies. The purpose of this article is to review the indications, surgical techniques, outcomes, and future directions of whole-organ pancreas and islets transplantations.

Association between primary graft function and 5-year outcomes of islet allogeneic transplantation in type 1 diabetes: a retrospective, multicentre, observational cohort study in 1210 patients from the Collaborative Islet Transplant Registry

BACKGROUND

Allogeneic islet transplantation is a validated therapy in type 1 diabetes; however, there is decline of transplanted islet graft function over time and the mechanisms underlying this decline are unclear. We evaluated the distinct association between primary graft function (PGF) and 5-year islet transplantation outcomes.

METHODS

In this retrospective, multicentre, observational cohort study, we enrolled all patients from the Collaborative Islet Transplant Registry who received islet transplantation alone (ITA recipients) or islet-after-kidney transplantation (IAK recipients) between Jan 19, 1999, and July 17, 2020, with a calculable PGF (exposure of interest), measured 28 days after last islet infusion with a validated composite index of islet graft function (BETA-2 score). The primary outcome was cumulative incidence of unsuccessful islet transplantation, defined as an HbA_1c of 7·0% (53 mmol/mol) or higher, or severe hypoglycaemia (ie, requiring third-party intervention to correct), or a fasting C-peptide concentration of less than 0·2 ng/mL. Secondary outcomes were graft exhaustion (fasting C-peptide <0·3 ng/mL); inadequate glucose control (HbA_1c ≥7·0% [53 mmol/mol] or severe hypoglycaemia); and requirement for exogenous insulin therapy (≥14 consecutive days). Associations between PGF and islet transplantation outcomes were explored with a competing risk analysis adjusted for all covariates suspected or known to affect outcomes. A predictive model based on PGF was built and internally validated by using bootstraps resampling method.

FINDINGS

In 39 centres worldwide, we enrolled 1210 patients with a calculable PGF (of those without missing data, mean age 47 years [SD 10], 712 [59·5%] were female, and 865 (97·9%) were White), who received a median of 10·8 thousand islet-equivalents per kg of bodyweight (IQR 7·4-13·5). 986 (82·4%) were ITA recipients and 211 (17·6%) were IAK recipients. Of 1210 patients, 452 (37·4%) received a single islet infusion and 758 (62·6%) received multiple islet infusions. Mean PGF was 14·3 (SD 8·8). The 5-year cumulative incidence of unsuccessful islet transplantation was 70·7% (95% CI 67·2-73·9), and was inversely and linearly related to PGF, with an adjusted subhazard ratio (sHR) of 0·77 (95% CI 0·72-0·82) per 5-unit increase of BETA-2 score (p<0·0001). Secondary endpoints were similarly related to PGF. The model-adjusted median C-statistic values of PGF for predicting 5-year cumulative incidences of unsuccessful islet transplantation, graft exhaustion, inadequate glucose control, and exogenous insulin therapy were 0·70 (range 0·69-0·71), 0·76 (0·74-0·77), 0·65 (0·64-0·66), and 0·72 (0·71-0·73), respectively.

INTERPRETATION

This global multicentre study reports a linear and independent association between PGF and 5-year clinical outcomes of islet transplantation. The main study limitations are its retrospective design and the absence of analysis of complications.

FUNDING

Public Health Service Research, National Institutes of Health, Juvenile Diabetes Research Foundation International, Agence National de la Recherche, Fondation de l'Avenir, and Fonds de Dotation Line Renaud-Loulou Gasté.

Recent Developments in Islet Biology: A Review With Patient Perspectives

Navigating the coronavirus disease-2019 (COVID-19, now COVID) pandemic has required resilience and creativity worldwide. Despite early challenges to productivity, more than 2,000 peer-reviewed articles on islet biology were published in 2021. Herein, we highlight noteworthy advances in islet research between January 2021 and April 2022, focussing on 5 areas. First, we discuss new insights into the role of glucokinase, mitogen-activated protein kinase-kinase/extracellular signal-regulated kinase and mitochondrial function on insulin secretion from the pancreatic β cell, provided by new genetically modified mouse models and live imaging. We then discuss a new connection between lipid handling and improved insulin secretion in the context of glucotoxicity, focussing on fatty acid-binding protein 4 and fetuin-A. Advances in high-throughput "omic" analysis evolved to where one can generate more finely tuned genetic and molecular profiles within broad classifications of type 1 diabetes and type 2 diabetes. Next, we highlight breakthroughs in diabetes treatment using stem cell-derived β cells and innovative strategies to improve islet survival posttransplantation. Last, we update our understanding of the impact of severe acute respiratory syndrome-coronavirus-2 infection on pancreatic islet function and discuss current evidence regarding proposed links between COVID and new-onset diabetes. We address these breakthroughs in 2 settings: one for a scientific audience and the other for the public, particularly those living with or affected by diabetes. Bridging biomedical research in diabetes to the community living with or affected by diabetes, our partners living with type 1 diabetes or type 2 diabetes also provide their perspectives on these latest advances in islet biology.

Graft failure after allogeneic islet transplantation in a patient with type 1 diabetes and a high anti-glutamic acid decarboxylase antibody titer

Pancreatic islet transplantation is a β-cell replacement therapy for people with insulin-deficient diabetes who have difficulty in glycemic control and suffer from frequent severe hypoglycemia. However, the number of islet transplantations carried out is still limited in Asia. We report a case of allogeneic islet transplantation in a 45-year-old Japanese man with type 1 diabetes. Although the islet transplantation was successfully carried out, graft loss was observed on the 18th day. Immunosuppressants were used in accordance with the protocol, and donor-specific anti-human leukocyte antigen antibodies were not detected. Autoimmunity relapse was also not observed. However, the patient had a high titer of anti-glutamic acid decarboxylase antibody from before the islet transplantation, and autoimmunity might thus have affected the β-cells in the transplanted islet. The evidence is still scarce to reach conclusions, and further data accumulation is required to enable proper patient selection before islet transplantation.

The Application of High-Throughput Approaches in Identifying Novel Therapeutic Targets and Agents to Treat Diabetes

During the past decades, unprecedented progress in technologies has revolutionized traditional research methodologies. Among these, advances in high-throughput drug screening approaches have permitted the rapid identification of potential therapeutic agents from drug libraries that contain thousands or millions of molecules. Moreover, high-throughput-based therapeutic target discovery strategies can comprehensively interrogate relationships between biomolecules (e.g., gene, RNA, and protein) and diseases and significantly increase the authors' knowledge of disease mechanisms. Diabetes is a chronic disease primarily characterized by the incapacity of the body to maintain normoglycemia. The prevalence of diabetes in modern society has become a severe public health issue that threatens the well-being of millions of patients. Although a number of pharmacological treatments are available, there is no permanent cure for diabetes, and discovering novel therapeutic targets and agents continues to be an urgent need. The present review discusses the technical details of high-throughput screening approaches in drug discovery, followed by introducing the applications of such approaches to diabetes research. This review aims to provide an example of the applicability of high-throughput technologies in facilitating different aspects of disease research.

HLA-B Matching Prolongs Allograft Survival in Islet Cell Transplantation

Islet cell transplantation (ITx) is an effective therapeutic approach for selected patients with type 1 diabetes with hypoglycemia unawareness and severe hypoglycemia events. In organ transplantation, human leukocyte antigen (HLA) mismatching between donor and recipient negatively impacts transplant outcomes. We aimed to determine whether HLA matching has an impact on islet allograft survival. Forty-eight patients were followed up after islet transplantation at our institution from 2000 to 2020 in a retrospective cohort. Patients underwent intrahepatic ITx or laparoscopic omental approach. Immunosuppression was dependent upon the protocol. We analyzed HLA data restricted to A, B, and DR loci on allograft survival using survival and subsequent multivariable analyses. Patients were aged 42.8 ± 8.4 years, and 64.3% were female. Diabetes duration was 28.6 ± 11.6 years. Patients matching all three HLA loci presented longer graft survival (P = 0.030). Patients with ≥1 HLA-B matching had longer graft survival compared with zero matching (P = 0.025). The number of HLA-B matching was positively associated with time of graft survival (Spearman's rho = 0.590; P = 0.034). Analyses adjusted for confounders showed that ≥1 matching for HLA-B decreased the risk of allograft failure (P = 0.009). Our data suggest that HLA-B matching between recipients and donors improved islet allograft survival. Matching all three HLA loci (A, B, and DR) was also associated with prolonged islet allograft survival. Prospective studies and a larger sample size are warranted to validate our findings.

Tissue engineering approaches and generation of insulin-producing cells to treat type 1 diabetes

Tissue engineering (TE) has become a new effective solution to a variety of medical problems, including diabetes. Mesenchymal stem cells (MSCs), which have the ability to differentiate into endodermal and mesodermal cells, appear to be appropriate for this function. The purpose of this review was to evaluate the outcomes of various researches on the insulin-producing cells (IPCs) generation from MSCs with TE approaches to increase efficacy of type 1 diabetes treatments. The search was performed in PubMed/Medline, Scopus and Embase databases until 2021. Studies revealed that MSCs could also differentiate into IPCs under certain conditions. Therefore, a wide range of protocols have been used for this differentiation, but their effectiveness is very different. Scaffolds can provide a microenvironment that enhances the MSCs to IPCs differentiation, improves their metabolic activity and up-regulate pancreatic-specific transcription factors. They also preserve IPCs architecture and enhance insulin production as well as protect against cell death. This systematic review offers a framework for prospective research based on data. In vitro and in vivo evidence suggests that scaffold-based TE can improve the viability and function of IPCs.

Fabrication of nanofibrous mat surrounded hydrogel scaffold as an encapsulation device for encapsulating pancreas β cells

The main barriers to cells or organ transplantation such as pancreatic β-cells are the need for lifelong immune suppression and the shortage of donors. It may be overcome via cell encapsulation and transplantation techniques. Hydrogels provide a suitable ECM-like microenvironment for cells to adhere, survive, and function, while weakly performing as an immune barrier. In this study, we aimed to macro-encapsulate islet cells in a dual encapsulation device with collagen hydrogel and PCL nanofiber to provide an immune-isolated environment for cells to function more efficiently, where immune cells are not allowed to enter but oxygen, insulin, and nutrients can pass through. PCL thin mats with the pores diameter of 500 nm were synthesized by electrospinning and characterized by scanning electron microscope, porosity measurement, tensile strength test, and contact angle measurement. Collagen hydrogel was fabricated by extracting collagen fibers from rat tail tendons and solving them in acetic acid. β-cells (CRI-D2 cell line) encapsulated after neutralizing collagen solution (pH ≈ 7.4). Cell-collagen gel complex was poured into the nanofibrous mat packets to fabricate the whole device. Histology evaluation, cell viability, and cell function tests were done in 10 days. Live/dead assay of Cri-D2 cells encapsulated within the device showed that cells have diffuse distribution at the core of the hydrogel and the device. Also, cluster formation was seen and shows these cells can live in groups. To identify cells' function within the device in these 10 days samples' supernatant insulin level was measured by chemiluminescent immunoassay. It just showed a positive result for existing insulin within the medium. Based on our results, this device presents adequate features to be a good immune-isolation device for cell transplanting.

In Vivo Bioluminescence for the Detection of the Fate of Pancreatic Islet Organoids Post-transplantation

Pancreatic islet transplantation is a promising cell replacement treatment for patients afflicted with type 1 diabetes (T1D), which is an autoimmune disease resulting in the destruction of insulin-producing islet β-cells. However, the shortage of donor pancreatic islets significantly hampers the widespread application of this strategy as routine therapy. Pluripotent stem cell-derived insulin-producing islet organoids constitute a promising alternative β-cell source for T1D patients. Early after transplantation, it is critical to know the fate of transplanted islet organoids, but determining their survival remains a significant technical challenge. Bioluminescence imaging (BLI) is an optical molecular imaging technique that detects the survival of living cells using light emitted from luciferase-expressing bioreporter cells. Through BLI, the post-transplantation fate of islet organoids can be evaluated over time in a noninvasive fashion with minimal intervention, thus making BLI an ideal tool to determine the success of the transplant and improving cell replacement therapy approaches for T1D.

3D-printed polyurethane immunoisolation bags with controlled pore architecture for macroencapsulation of islet clusters encapsulated in alginate gel

Diabetes mellitus is a fast-growing chronic metabolic condition caused by insulin deficiency or resistance, leading to lifelong insulin use. It has become one of the world's most difficult non-communicable diseases. The goal of this study was to view the effectiveness of the combined method of macro- and microencapsulation for islet transplantation. The process of 3D printing is used to make macroencapsulation bags with regulated diffusion properties thanks to the emerging small pored channels. The ink used to manufacture 3D-printed bags with controlled specifications was polyurethane solution (13% w/v). Swelling experiments revealed that there was very little swelling and that the membrane maintained its structural stability. Alginate beads (made from 5% w/v solution) were used to microencapsulate islet cell clusters. Direct contact assay was used to confirm in vitro cytocompatibility. The insulin release from the encapsulated rabbit islets was confirmed using a glucose challenge assay. When challenged with 20 mM glucose on day 7, the encapsulated islet cells released insulin at a rate of 9.72 ± 0.65 mU/L, which was identical to the RIN-5F islet cell line control, confirming the functioning of the encapsulated islets. After 21 days of culture, the islets were shown to be viable utilizing a live-dead assay. As a result, our work demonstrates that 3D printing for macroencapsulating cells, as well as microencapsulation with alginates, is a viable scale-up technology with great potential in the field of pancreatic islet transplantation.

Type 1 diabetes and engineering enhanced islet transplantation

The development of new therapeutic approaches to treat type 1 diabetes mellitus (T1D) relies on the precise understanding and deciphering of insulin-secreting β-cell biology, as well as the mechanisms responsible for their autoimmune destruction. β-cell or islet transplantation is viewed as a potential long-term therapy for the millions of patients with diabetes. To advance the field of insulin-secreting cell transplantation, two main research areas are currently investigated by the scientific community: (1) the identification of the developmental pathways that drive the differentiation of stem cells into insulin-producing cells, providing an inexhaustible source of cells; and (2) transplantation strategies and engineered transplants to provide protection and enhance the functionality of transplanted cells. In this review, we discuss the biology of pancreatic β-cells, pathology of T1D and current state of β-cell differentiation. We give a comprehensive view and discuss the different possibilities to engineer enhanced insulin-secreting cell/islet transplantation from a translational perspective.

Pancreatic islet transplantation in type 1 diabetes: 20-year experience from a single-centre cohort in Canada

BACKGROUND

Islet transplantation offers an effective treatment for selected people with type 1 diabetes and intractable hypoglycaemia. Long-term experience, however, remains limited. We report outcomes from a single-centre cohort up to 20 years after islet transplantation.

METHODS

This cohort study included patients older than 18 years with type 1 diabetes undergoing allogeneic islet transplantation between March 11, 1999, and Oct 1, 2019, at the University of Alberta Hospital (Edmonton, AB, Canada). Patients who underwent islet-after-kidney transplantation and islet transplantation alone or islet transplantation before whole-pancreas transplantation (follow-up was censored at the time of whole-pancreas transplantation) were included. Patient survival, graft survival (fasting plasma C-peptide >0·1 nmol/L), insulin independence, glycaemic control, and adverse events are reported. To identify factors associated with prolonged graft survival, recipients with sustained graft survival (≥90% of patient follow-up duration) were compared with those who had non-sustained graft survival (<90% of follow-up duration). Multivariate binary logistic regression analyses were done to determine predictors of sustained graft survival.

FINDINGS

Between March 11, 1999, and Oct 1, 2019, 255 patients underwent islet transplantation and were included in the analyses (149 [58%] were female and 218 [85%] were White). Over a median follow-up of 7·4 years (IQR 4·4-12·2), 230 (90%) patients survived. Median graft survival was 5·9 years (IQR 3·0-9·5), and graft failure occurred in 91 (36%) patients. 178 (70%) recipients had sustained graft survival, and 77 (30%) had non-sustained graft survival. At baseline, compared with patients with non-sustained graft survival, those with sustained graft survival had longer median type 1 diabetes duration (33·5 years [IQR 24·3-41·7] vs 26·2 years [17·0-35·5]; p=0·0003), median older age (49·4 years [43·5-56·1] vs 44·2 years [35·4-54·2]; p=0·0011), and lower median insulin requirements (0·53 units/kg per day [0·45-0·67] vs 0·59 units/kg per day [0·48-0·70]; p=0·032), but median HbA_1c concentrations were similar (8·2% [7·5-9·0] vs 8·5% [7·8-9·2]; p=0·23). 201 (79%) recipients had insulin independence, with a Kaplan-Meier estimate of 61% (95% CI 54-67) at 1 year, 32% (25-39) at 5 years, 20% (14-27) at 10 years, 11% (6-18) at 15 years, and 8% (2-17) at 20 years. Patients with sustained graft survival had significantly higher rates of insulin independence (160 [90%] of 178 vs 41 [53%] of 77; p<0·0001) and sustained improvements in glycaemic control mixed-main-effects model group effect, p<0·0001) compared with those with non-sustained graft survival. Multivariate analyses identified the combined use of anakinra plus etanercept (adjusted odds ratio 7·5 [95% CI 2·7-21·0], p<0·0001) and the BETA-2 score of 15 or higher (4·1 [1·5-11·4], p=0·0066) as factors associated with sustained graft survival. In recipients with sustained graft survival, the incidence of procedural complications was lower (23 [5%] of 443 infusions vs 17 [10%] of 167 infusions; p=0·027), whereas the incidence of cancer was higher (29 of [16%] of 178 vs four [5%] of 77; p=0·015) than in those with non-sustained graft survival; most were skin cancers (22 [67%] of 33). End-stage renal disease and severe infections were similar between groups.

INTERPRETATION

We present the largest single-centre cohort study of long-term outcomes following islet transplantation. Although some limitations with our study remain, such as the retrospective component, a relatively small sample size, and the absence of non-transplant controls, we found that the combined use of anakinra plus etanercept and the BETA-2 score were associated with improved outcomes, and therefore these factors could inform clinical practice.

FUNDING

None.

Preferences for Risks and Benefits of Islet Cell Transplantation for Persons With Type 1 Diabetes With History of Episodes of Severe Hypoglycemia: A Discrete-Choice Experiment to Inform Regulatory Decisions

BACKGROUND

The advisory panel for US Food and Drug Administration (FDA) recently endorsed pancreatic islet cell transplantation (ICT) therapy for suboptimally controlled type 1 diabetes (T1D), and FDA approval is under consideration. An important part of regulatory approval includes the patient perspective, through discrete choice. We developed a discrete-choice instrument and used it to determine how 90 people with T1D weigh the risks and benefits of ICT to inform regulatory decisions.

METHODS

Sawtooth software created a random, full-profile, balanced-overlap experimental design for a measure with 8 attributes of ICT risks/benefits, each with 3 to 5 levels. We asked 18 random task pairs, sociodemographics, diabetes management, and hypoglycemia questions. Analysis was performed using random parameters logistic regression technique.

RESULTS

The strongest preference was for avoiding the highest chance (15%) of serious procedure-related complications (β = -2.03, P < 0.001). The strongest positive preference was for gaining 5-y insulin independence (β = 1.75, P < 0.001). The desire for 5-y HbA1C-defined clinical treatment success was also strong (β = 1.39, P < 0.001). Subgroup analysis suggested strong gender differences with women showing much higher preferences for all benefits (68% higher for 5-y insulin independence), and men were generally more risk averse than women. Those with high versus low diabetes distress showed 3 times stronger preference for 5-y insulin independence but also twice preference to avoid risks of serious complications.

CONCLUSION

Despite showing the most preference for avoiding serious ICT complications, people with T1D had a strong preference for achieving ICT benefits, especially insulin independence. We identified important attributes of ICT and demonstrated that patients are willing to make these trade-offs, showing support for the introduction of ICT.

Prolonged Islet Allograft Function is Associated With Female Sex in Patients After Islet Transplantation

BACKGROUND

Islet transplantation (ITx) has proved to be effective in preventing severe hypoglycemia and improving metabolic control in selected subjects with type 1 diabetes. Long-term graft function remains a challenge. Estrogens have been shown to protect β cells from metabolic stresses and improve revascularization of transplanted human islets in the mouse. We aimed to evaluate the influence of sex in allograft survival of ITx recipients.

METHODS

We analyzed a retrospective cohort of ITx recipients (n = 56) followed-up for up to 20 years. Allograft failure was defined as a stimulated C-peptide <0.3 ng/mL during a mixed-meal tolerance test. Subjects were divided into recipients of at least 1 female donor (group 1) and recipients of male donors only (group 2).

RESULTS

Group 1 subjects (n = 25) were aged 41.5 ± 8.4 years and group 2 subjects (n = 22) 45.9 ± 7.3 years (P = 0.062). Female recipient frequency was 44.8% (n = 13) in group 1 and 55.2% (n = 16) in group 2 (P = 0.145). Group 2 developed graft failure earlier than group 1 (680 [286-1624] vs 1906 [756-3256] days, P = 0.038). We performed additional analyses on female recipients only from each group (group 1, n = 16; group 2, n = 20). Female recipients in group 1 exhibited prolonged allograft function compared with group 2, after adjustment for confounders (odds ratio, 28.6; 95% CI, 1.3-619.1; P < 0.05).

CONCLUSION

Recipients of islets from at least 1 female donor exhibited prolonged graft survival compared with recipients of islets from exclusively male donors. In addition, female recipients exhibited prolonged survival compared with male recipients following ITx of at least 1 female donor.

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.

The Human Islet: Mini-Organ With Mega-Impact

This review focuses on the human pancreatic islet-including its structure, cell composition, development, function, and dysfunction. After providing a historical timeline of key discoveries about human islets over the past century, we describe new research approaches and technologies that are being used to study human islets and how these are providing insight into human islet physiology and pathophysiology. We also describe changes or adaptations in human islets in response to physiologic challenges such as pregnancy, aging, and insulin resistance and discuss islet changes in human diabetes of many forms. We outline current and future interventions being developed to protect, restore, or replace human islets. The review also highlights unresolved questions about human islets and proposes areas where additional research on human islets is needed.

Hypoparathyroidism: State of the Art on Cell and Tissue Therapies

Hypoparathyroidism is an endocrine disorder characterized by low serum calcium levels, high serum phosphorus levels, and by inappropriate or absent secretion of the parathyroid hormone (PTH). The most common therapeutic strategy to treat this condition is hormone replacement therapy with calcium and vitamin D but, unfortunately, in the long term this treatment may not be sufficient to compensate for the loss of endocrine function. Glandular autotransplantation is considered the most effective technique in place of replacement therapy. Although it leads to excellent results in most cases, autotransplantation is not always possible. Allograft is a good way to treat patients who have not been able to undergo autograft, but this technique has limited success due to side effects related to tissue rejection. This therapy is supported by systemic immunosuppression, which leads to the onset of serious side effects in patients, with a risk of endocrine toxicity. Today, research on endocrine disorders is focused on discovering alternative graft therapies that can allow optimal results with the fewest possible side effects. In this review, we will make an update on the current state of the art about the cell and tissue therapy as treatment for hypoparathyroidism, to identify which type of therapeutic strategy could be valid for a future clinical use.

Fibroblast growth factor 7 releasing particles enhance islet engraftment and improve metabolic control following islet transplantation in mice with diabetes

Transplantation of islets in type 1 diabetes (T1D) is limited by poor islet engraftment into the liver, with two to three donor pancreases required per recipient. We aimed to condition the liver to enhance islet engraftment to improve long-term graft function. Diabetic mice received a non-curative islet transplant (n = 400 islets) via the hepatic portal vein (HPV) with fibroblast growth factor 7-loaded galactosylated poly(DL-lactide-co-glycolic acid) (FGF7-GAL-PLGA) particles; 26-µm diameter particles specifically targeted the liver, promoting hepatocyte proliferation in short-term experiments: in mice receiving 0.1-mg FGF7-GAL-PLGA particles (60-ng FGF7) vs vehicle, cell proliferation was induced specifically in the liver with greater efficacy and specificity than subcutaneous FGF7 (1.25 mg/kg ×2 doses; ~75-µg FGF7). Numbers of engrafted islets and vascularization were greater in liver sections of mice receiving islets and FGF7-GAL-PLGA particles vs mice receiving islets alone, 72 h posttransplant. More mice (six of eight) that received islets and FGF7-GAL-PLGA particles normalized blood glucose concentrations by 30-days posttransplant, versus zero of eight mice receiving islets alone with no evidence of increased proliferation of cells within the liver at this stage and normal liver function tests. This work shows that liver-targeted FGF7-GAL-PLGA particles achieve selective FGF7 delivery to the liver-promoting islet engraftment to help normalize blood glucose levels with a good safety profile.

Engineering islets from stem cells for advanced therapies of diabetes

Diabetes mellitus is a metabolic disorder that affects more than 460 million people worldwide. Type 1 diabetes (T1D) is caused by autoimmune destruction of β-cells, whereas type 2 diabetes (T2D) is caused by a hostile metabolic environment that leads to β-cell exhaustion and dysfunction. Currently, first-line medications treat the symptomatic insulin resistance and hyperglycaemia, but do not prevent the progressive decline of β-cell mass and function. Thus, advanced therapies need to be developed that either protect or regenerate endogenous β-cell mass early in disease progression or replace lost β-cells with stem cell-derived β-like cells or engineered islet-like clusters. In this Review, we discuss the state of the art of stem cell differentiation and islet engineering, reflect on current and future challenges in the area and highlight the potential for cell replacement therapies, disease modelling and drug development using these cells. These efforts in stem cell and regenerative medicine will lay the foundations for future biomedical breakthroughs and potentially curative treatments for diabetes.

Generation of insulin-producing pancreatic β cells from multiple human stem cell lines

We detail a six-stage planar differentiation methodology for generating human pluripotent stem cell-derived pancreatic β cells (SC-β cells) that secrete high amounts of insulin in response to glucose stimulation. This protocol first induces definitive endoderm by treatment with Activin A and CHIR99021, then generates PDX1+/NKX6-1+ pancreatic progenitors through the timed application of keratinocyte growth factor, SANT1, TPPB, LDN193189 and retinoic acid. Endocrine induction and subsequent SC-β-cell specification is achieved with a cocktail consisting of the cytoskeletal depolymerizing compound latrunculin A combined with XXI, T3, ALK5 inhibitor II, SANT1 and retinoic acid. The resulting SC-β cells and other endocrine cell types can then be aggregated into islet-like clusters for analysis and transplantation. This differentiation methodology takes ~34 d to generate functional SC-β cells, plus an additional 1-2 weeks for initial stem cell expansion and final cell assessment. This protocol builds upon a large body of previous work for generating β-like cells. In this iteration, we have eliminated the need for 3D culture during endocrine induction, allowing for the generation of highly functional SC-β cells to be done entirely on tissue culture polystyrene. This change simplifies the differentiation methodology, requiring only basic stem cell culture experience as well as familiarity with assessment techniques common in biology laboratories. In addition to expanding protocol accessibility and simplifying SC-β-cell generation, we demonstrate that this planar methodology is amenable for differentiating SC-β cells from a wide variety of cell lines from various sources, broadening its applicability.

Modulating the foreign body response of implants for diabetes treatment

Diabetes Mellitus is a group of diseases characterized by high blood glucose levels due to patients' inability to produce sufficient insulin. Current interventions often require implants that can detect and correct high blood glucose levels with minimal patient intervention. However, these implantable technologies have not reached their full potential in vivo due to the foreign body response and subsequent development of fibrosis. Therefore, for long-term function of implants, modulating the initial immune response is crucial in preventing the activation and progression of the immune cascade. This review discusses the different molecular mechanisms and cellular interactions involved in the activation and progression of foreign body response (FBR) and fibrosis, specifically for implants used in diabetes. We also highlight the various strategies and techniques that have been used for immunomodulation and prevention of fibrosis. We investigate how these general strategies have been applied to implants used for the treatment of diabetes, offering insights on how these devices can be further modified to circumvent FBR and fibrosis.

Carbohydrate antigen microarray analysis of serum IgG and IgM antibodies before and after adult porcine islet xenotransplantation in cynomolgus macaques

Understanding the anti-carbohydrate antibody response toward epitopes expressed on porcine cells, tissues, and organs is critical to advancing xenotransplantation toward clinical application. In this study, we determined IgM and IgG antibody specificities and relative concentrations in five cynomolgus monkeys at baseline and at intervals following intraportal xenotransplantation of adult porcine islets. This study utilized a carbohydrate antigen microarray that comprised more than 400 glycoconjugates, including historically reported α-Gal and non-α-Gal carbohydrate antigens with various modifications. The elicited anti-carbohydrate antibody responses were predominantly IgM compared to IgG in 4 out of 5 monkeys. Patterns of elicited antibody responses greater than 1.5 difference (log2 base units; 2.8-fold on a linear scale) from pre-serum to post-serum sampling specific for carbohydrate antigens were heterogeneous and recipient-specific. Increases in the elicited antibody response to α-Gal, Sda, GM2 antigens, or Lexis X antigen were found in individual monkeys. The novel carbohydrate structures Galβ1-4GlcNAcβ1-3Galβ1 and N-linked glycans with Manα1-6(GlcNAcβ1-2Manα1-3)Manβ1-4GlcNAcβ structure were common targets of elicited IgM antibodies. These results provide important insights into the carbohydrate epitopes that elicit antibodies following pig-to-monkey islet xenotransplantation and reveal possible targets for gene editing.

Tailored generation of insulin producing cells from canine mesenchymal stem cells derived from bone marrow and adipose tissue

The trend of regenerative therapy for diabetes in human and veterinary practices has conceptually been proven according to the Edmonton protocol and animal models. Establishing an alternative insulin-producing cell (IPC) resource for further clinical application is a challenging task. This study investigated IPC generation from two practical canine mesenchymal stem cells (cMSCs), canine bone marrow-derived MSCs (cBM-MSCs) and canine adipose-derived MSCs (cAD-MSCs). The results illustrated that cBM-MSCs and cAD-MSCs contain distinct pancreatic differentiation potential and require the tailor-made induction protocols. The effective generation of cBM-MSC-derived IPCs needs the integration of genetic and microenvironment manipulation using a hanging-drop culture of PDX1-transfected cBM-MSCs under a three-step pancreatic induction protocol. However, this protocol is resource- and time-consuming. Another study on cAD-MSC-derived IPC generation found that IPC colonies could be obtained by a low attachment culture under the three-step induction protocol. Further, Notch signaling inhibition during pancreatic endoderm/progenitor induction yielded IPC colonies through the trend of glucose-responsive C-peptide secretion. Thus, this study showed that IPCs could be obtained from cBM-MSCs and cAD-MSCs through different induction techniques. Also, further signaling manipulation studies should be conducted to maximize the protocol’s efficiency.

Immunosuppressive PLGA TGF-β1 Microparticles Induce Polyclonal and Antigen-Specific Regulatory T Cells for Local Immunomodulation of Allogeneic Islet Transplants

Allogeneic islet transplantation is a promising cell-based therapy for Type 1 Diabetes (T1D). The long-term efficacy of this approach, however, is impaired by allorejection. Current clinical practice relies on long-term systemic immunosuppression, leading to severe adverse events. To avoid these detrimental effects, poly(lactic-co-glycolic acid) (PLGA) microparticles (MPs) were engineered for the localized and controlled release of immunomodulatory TGF-β1. The in vitro co-incubation of TGF-β1 releasing PLGA MPs with naïve CD4⁺ T cells resulted in the efficient generation of both polyclonal and antigen-specific induced regulatory T cells (iTregs) with robust immunosuppressive function. The co-transplantation of TGF-β1 releasing PLGA MPs and Balb/c mouse islets within the extrahepatic epididymal fat pad (EFP) of diabetic C57BL/6J mice resulted in the prompt engraftment of the allogenic implants, supporting the compatibility of PLGA MPs and local TGF-β1 release. The presence of the TGF-β1-PLGA MPs, however, did not confer significant graft protection when compared to untreated controls, despite measurement of preserved insulin expression, reduced intra-islet CD3⁺ cells invasion, and elevated CD3⁺Foxp3⁺ T cells at the peri-transplantation site in long-term functioning grafts. Examination of the broader impacts of TGF-β1/PLGA MPs on the host immune system implicated a localized nature of the immunomodulation with no observed systemic impacts. In summary, this approach establishes the feasibility of a local and modular microparticle delivery system for the immunomodulation of an extrahepatic implant site. This approach can be easily adapted to deliver larger doses or other agents, as well as multi-drug approaches, within the local graft microenvironment to prevent transplant rejection.

Progress in Translational Regulatory T Cell Therapies for Type 1 Diabetes and Islet Transplantation

Regulatory T cells (Tregs) have become highly relevant in the pathophysiology and treatment of autoimmune diseases, such as type 1 diabetes (T1D). As these cells are known to be defective in T1D, recent efforts have explored ex vivo and in vivo Treg expansion and enhancement as a means for restoring self-tolerance in this disease. Given their capacity to also modulate alloimmune responses, studies using Treg-based therapies have recently been undertaken in transplantation. Islet transplantation provides a unique opportunity to study the critical immunological crossroads between auto- and alloimmunity. This procedure has advanced greatly in recent years, and reports of complete abrogation of severe hypoglycemia and long-term insulin independence have become increasingly reported. It is clear that cellular transplantation has the potential to be a true cure in T1D, provided the remaining barriers of cell supply and abrogated need for immune suppression can be overcome. However, the role that Tregs play in islet transplantation remains to be defined. Herein, we synthesize the progress and current state of Treg-based therapies in T1D and islet transplantation. We provide an extensive, but concise, background to understand the physiology and function of these cells and discuss the clinical evidence supporting potency and potential Treg-based therapies in the context of T1D and islet transplantation. Finally, we discuss some areas of opportunity and potential research avenues to guide effective future clinical application. This review provides a basic framework of knowledge for clinicians and researchers involved in the care of patients with T1D and islet transplantation.

Insights from single cell studies of human pancreatic islets and stem cell-derived islet cells to guide functional beta cell maturation in vitro

There is now a sizeable number of single cell transcriptomics studies performed on human and rodent pancreatic islets that have shed light on the unique gene signatures and level of heterogeneity within each individual islet cell type. Following closely from these studies, there is also rapidly-growing activity on characterizing islet-like cells derived from in vitro differentiation of human pluripotent stem cells (hPSCs) at the single cell level. The overall consensus across the studies so far suggests that the first few stages of differentiation are largely uniform, whereas during pancreatic endocrine commitment, cell trajectories start to diverge, resulting in multiple end-stage pancreatic cells that include progenitor-like, endocrine and non-endocrine cells. Comprehensive transcriptional profiling is important for understanding how and why islet cells, especially the insulin-secreting beta cells, exist in subpopulations that differ in maturity, proliferation rate, sensitivity to stress, and insulin secretion function. For hPSC-derived beta cells to be used confidently for cell therapy, optimal differentiation and thorough characterization is required. The key questions to address are-What is the trajectory of differentiation? Is heterogeneity a natural occurrence or is it a consequence of imperfect differentiation protocols? Can lessons be drawn from the extensive single cell transcriptomic data to help guide maturation of beta cells in vitro? This book chapter seeks to address some of these questions, and facilitate ongoing efforts in improving the beta cell differentiation pipeline or enriching for desired beta cell populations following differentiation, to make way for better mechanistic studies and future clinical translation.

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

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

Advancements in transplantation therapy for diabetes: Pancreas, islet and stem cell

Pancreas transplantation and islet transplantation are now established in the treatment of IDDM. Several trials of stem cell-derived cell transplantation therapy are underway and may offer an alternative to the limited supply of donor islets in the near future. This article summarizes recent developments in transplantation therapy for diabetes as well as research on the use of stem cells for complications of diabetes.

Development of a Bioartificial Vascular Pancreas

Transplantation of pancreatic islets has been shown to be effective, in some patients, for the long-term treatment of type 1 diabetes. However, transplantation of islets into either the portal vein or the subcutaneous space can be limited by insufficient oxygen transfer, leading to islet loss. Furthermore, oxygen diffusion limitations can be magnified when islet numbers are increased dramatically, as in translating from rodent studies to human-scale treatments. To address these limitations, an islet transplantation approach using an acellular vascular graft as a vascular scaffold has been developed, termed the BioVascular Pancreas (BVP). To create the BVP, islets are seeded as an outer coating on the surface of an acellular vascular graft, using fibrin as a hydrogel carrier. The BVP can then be anastomosed as an arterial (or arteriovenous) graft, which allows fully oxygenated arterial blood with a pO2 of roughly 100 mmHg to flow through the graft lumen and thereby supply oxygen to the islets. In silico simulations and in vitro bioreactor experiments show that the BVP design provides adequate survivability for islets and helps avoid islet hypoxia. When implanted as end-to-end abdominal aorta grafts in nude rats, BVPs were able to restore near-normoglycemia durably for 90 days and developed robust microvascular infiltration from the host. Furthermore, pilot implantations in pigs were performed, which demonstrated the scalability of the technology. Given the potential benefits provided by the BVP, this tissue design may eventually serve as a solution for transplantation of pancreatic islets to treat or cure type 1 diabetes.

Non-invasive Beta-cell Imaging: Visualization, Quantification, and Beyond

Pancreatic beta (β)-cell dysfunction and reduced mass play a central role in the development and progression of diabetes mellitus. Conventional histological β-cell mass (BCM) analysis is invasive and limited to cross-sectional observations in a restricted sampling area. However, the non-invasive evaluation of BCM remains elusive, and practical in vivo and clinical techniques for β-cell-specific imaging are yet to be established. The lack of such techniques hampers a deeper understanding of the pathophysiological role of BCM in diabetes, the implementation of personalized BCM-based diabetes management, and the development of antidiabetic therapies targeting BCM preservation and restoration. Nuclear medical techniques have recently triggered a major leap in this field. In particular, radioisotope-labeled probes using exendin peptides that include glucagon-like peptide-1 receptor (GLP-1R) agonist and antagonist have been employed in positron emission tomography and single-photon emission computed tomography. These probes have demonstrated high specificity to β cells and provide clear images accurately showing uptake in the pancreas and transplanted islets in preclinical in vivo and clinical studies. One of these probes, ¹¹¹indium-labeled exendin-4 derivative ([Lys¹²(¹¹¹In-BnDTPA-Ahx)]exendin-4), has captured the longitudinal changes in BCM during the development and progression of diabetes and under antidiabetic therapies in various mouse models of type 1 and type 2 diabetes mellitus. GLP-1R-targeted imaging is therefore a promising tool for non-invasive BCM evaluation. This review focuses on recent advances in non-invasive in vivo β-cell imaging for BCM evaluation in the field of diabetes; in particular, the exendin-based GLP-1R-targeted nuclear medicine techniques.

Protection of Pancreatic Islets Using Theranostic Silencing Nanoparticles in a Baboon Model of Islet Transplantation

The long-term success of pancreatic islet transplantation (Tx) as a cure for type 1 diabetes remains limited. Islet loss after Tx related to apoptosis, inflammation, and other factors continues to limit Tx efficacy. In this project, we demonstrate a novel approach aimed at protecting islets before Tx in nonhuman primates (NHPs) (baboons) by silencing a gene (caspase-3) responsible for induction of apoptosis. This was done using siRNA (siCas-3) conjugated to magnetic nanoparticles (MNs). In addition to serving as carriers for siCas-3, these nanoparticles also act as reporters for MRI, so islets labeled with MN-siCas-3 can be monitored in vivo after Tx. In vitro studies showed the antiapoptotic effect of MN-siCas-3 on islets in culture, resulting in minimal islet loss. For in vivo studies, donor baboon islets were labeled with MN-siCas-3 and infused into recipient diabetic subjects. A dramatic reduction in insulin requirements was observed in animals transplanted with even a marginal number of labeled islets compared with controls. By demonstrating the protective effect of MN-siCas-3 in the challenging NHP model, this study proposes a novel strategy to minimize the number of donor islets required from either cadaveric or living donors.

Beta Cell Imaging-From Pre-Clinical Validation to First in Man Testing

There are presently no reliable ways to quantify human pancreatic beta cell mass (BCM) in vivo, which prevents an accurate understanding of the progressive beta cell loss in diabetes or following islet transplantation. Furthermore, the lack of beta cell imaging hampers the evaluation of the impact of new drugs aiming to prevent beta cell loss or to restore BCM in diabetes. We presently discuss the potential value of BCM determination as a cornerstone for individualized therapies in diabetes, describe the presently available probes for human BCM evaluation, and discuss our approach for the discovery of novel beta cell biomarkers, based on the determination of specific splice variants present in human beta cells. This has already led to the identification of DPP6 and FXYD2ga as two promising targets for human BCM imaging, and is followed by a discussion of potential safety issues, the role for radiochemistry in the improvement of BCM imaging, and concludes with an overview of the different steps from pre-clinical validation to a first-in-man trial for novel tracers.

Pancreatectomy, Islet Cell Transplantation, and Nutrition Considerations

Pancreatic islet transplantation is a reliable approach for treating insulin-deficient diabetes. This established β-cell replacement approach has shown considerable improvements in the last 2 decades. It has helped achieve metabolic homeostasis and safe outcomes for a subset of patients with type 1 diabetes and severe pancreatitis. Nutrition support, until recently, was considered as a secondary factor, merely identified as a means of providing all the necessary nutrients for such patients. However, new literature suggests that several factors, such as the route, timing, quantity, and composition of all the nutrients administered, have key disease-altering properties and are vital during the perioperative management of such patients. This review will highlight the benefits of performing the clinical islet transplantation on a subgroup of patients with type 1 diabetes and pancreatitis and summarize new data that identify the pivotal role of nutrition support as a critical intervention in their management.

In Vivo Differentiation of Stem Cell-derived Human Pancreatic Progenitors to Treat Type 1 Diabetes

Type 1 diabetes mellitus (T1DM) is an autoimmune disease that results from the loss of the pancreatic β-cells. The autoimmune destruction of the β-cells causes the loss of insulin production from the islets of the pancreas, resulting in the loss of blood glucose regulation. This loss of regulation, if not treated, can lead to a plethora of long-term complications in patients. Subsequently, T1DM patients rely on the administration of exogenous insulin sources to maintain their blood glucose levels. In this review, we summarize the history of T1DM therapy and current treatment options. Although treatments for T1DM have progressed substantially, none of the available treatment options allow the patient to live autonomously. Therefore, the challenge to develop a therapy that will fully reverse the disease still remains. A promising field of T1DM therapies is cell replacement therapies derived from human pluripotent stem cells. Here, we specifically review studies that employ stem-cell derived pancreatic progenitors transplanted for in vivo differentiation/maturation and discuss, in detail, the complications that arise post transplantation, including heterogeneity, graft immaturity, and host foreign bodyresponse. We also discuss efforts to induce human stem cell-derived mature β-cells in vitro and compare strategies regarding transplantation of pancreatic progenitors versus mature β-cells cells. Finally, we review key approaches that address critical limitations of in vivo progenitor differentiation including vascularization, oxygenation, and transplant location. The field of islet replacement therapy has made tremendous progress in the last two decades. If the strengths and limitations of the field continue to be identified and addressed, future studies will lead to an ideal treatment for T1DM. Graphical abstract.

Alginate/Pluronic F127-based encapsulation supports viability and functionality of human dental pulp stem cell-derived insulin-producing cells

BACKGROUND

Current approach for diabetes treatment remained several adverse events varied from gastrointestinal to life-threatening symptoms. Regenerative therapy regarding Edmonton protocol has been facing serious limitations involving protocol efficiency and safety. This led to the study for alternative insulin-producing cell (IPC) resource and transplantation platform. In this study, evaluation of encapsulated human dental pulp-derived stem cell (hDPSC)-derived IPCs by alginate (ALG) and pluronic F127-coated alginate (ALGPA) was performed.

RESULTS

The results showed that ALG and ALGPA preserved hDPSC viability and allowed glucose and insulin diffusion in and out. ALG and ALGPA-encapsulated hDPSC-derived IPCs maintained viability for at least 336 h and sustained pancreatic endoderm marker (NGN3), pancreatic islet markers (NKX6.1, MAF-A, ISL-1, GLUT-2 and INSULIN), and intracellular pro-insulin and insulin expressions for at least 14 days. Functional analysis revealed a glucose-responsive C-peptide secretion of ALG- and ALGPA-encapsulated hDPSC-derived IPCs at 14 days post-encapsulation.

CONCLUSION

ALG and ALGPA encapsulations efficiently preserved the viability and functionality of hDPSC-derived IPCs in vitro and could be the potential transplantation platform for further clinical application.

Integrative protocols for an in vitro generation of pancreatic progenitors from human dental pulp stem cells

Efficiency of the induction protocol is crucial for the generation of insulin-producing cells (IPCs) from human dental pulp stem cells (hDPSCs). Here, we established the integrative induction protocol by merging genetic manipulation technique with our previous published 3-step induction protocol aiming to enhance the pancreatic progenitor commitment and production yield. We found that the overexpression of PDX1 following with 3-step induction protocol were able to generate the 3-dimensional (3D) colony structure of pancreatic progenitors (PPs) with the beneficial trends of pancreatic endoderm commitment and production yield, while other protocols using the prolong maintenance of PDX1-overexpressed hDPSCs and the PDX1 overexpression after definitive endoderm induction were unable to generate and sustain the 3D structure of the colonies. Further Notch signaling manipulation by DAPT treatment showed lesser degree of positive effects on progenitor commitment and production yield. Although the generated PPs from the integrative protocol expressed pancreatic mRNA markers along with pro-insulin and insulin proteins, they still contained the defective glucose-responsive C-peptide secretion. Only basal secreted C-peptide level was observed. In summary, the integrative induction protocol potentially enhanced the PP generation with high colony production yield and could serve as an efficient platform for further hDPSC-derived IPC production and maturation.

Improvement of human pancreatic islet quality after co-culture with human adipose-derived stem cells

The aim of this study was to investigate whether co-culture of human islets with adipose-derived stem cells (ASCs) can improve islet quality and to evaluate which factors play a role in the protective effect of ASCs against islet dysfunction. Islets and ASCs were cultured in three experimental groups for 24 h, 48 h, and 72 h: 1) indirect co-culture of islets with ASC monolayer (Islets/ASCs); 2) islets alone; and 3) ASCs alone. Co-culture with ASCs improved islet viability and function in all culture time-points analyzed. VEGFA, HGF, IL6, IL8, IL10, CCL2, IL1B, and TNF protein levels were increased in supernatants of islet/ASC group compared to islets alone, mainly after 24 h. Moreover, VEGFA, IL6, CCL2, HIF1A, XIAP, CHOP, and NFKBIA genes were differentially expressed in islets from the co-culture condition compared to islets alone. In conclusion, co-culture of islets with ASCs promotes improvements in islet quality.

β-Cell and renal transplantation options for diabetes

Despite major advances in structured education, insulin delivery and glucose monitoring, diabetes self-management remains an unremitting challenge. Insulin therapy is inextricably linked to risk of dangerous hypoglycaemia and sustained hyperglycaemia remains a leading cause of renal failure. This review sets out to demystify transplantation for diabetes multidisciplinary teams, facilitating consideration and incorporation within holistic overall person-centred management. Deceased and living donor kidney, whole pancreas and isolated islet transplant procedures, indications and potential benefits are described, in addition to outcomes within the integrated UK transplant programme.

Long-term outcome of islet transplantation on insulin-dependent diabetes mellitus: An observational cohort study

AIMS/INTRODUCTION

To investigate the long-term efficacy and safety of islet transplantation (ITx) compared with multiple daily injections (MDI) or continuous subcutaneous insulin infusion (CSII).

MATERIALS AND METHODS

Among 619 patients diagnosed as insulin-dependent diabetes mellitus or type 1 diabetes at Kyoto University, Kyoto, Japan, seven patients were selected as the ITx group and 26 age-matched patients with no endogenous insulin secretion were selected as the MDI/CSII group. Hemoglobin A1c, aspartate aminotransferase/alanine aminotransferase (AST/ALT) and creatinine were assessed retrospectively at 1, 2, 5 and 10 years for both groups; serum C-peptide immunoreactivity was assessed for the ITx group. Major clinical events were also assessed.

RESULTS

Hemoglobin A1c improvement in ITx was significant at 1 year (8.4% [7.8-9.9%] at baseline to 7.1% [6.3-7.4%] in ITx vs 8.2% [7.4-9.8%] at baseline to 8.1% [7.3-9.5%] in MDI/CSII, P < 0.01 between groups), and was maintained at 2 years (7.4% [6.3-8.2%] vs 8.4% [7.4-9.6%], P = 0.11). The increase of stimulated C-peptide immunoreactivity was significant at 1 year (0.57 ng/mL [0.26-0.99 ng/mL], P < 0.05 from baseline) and 2 years (0.43 ng/mL [0.19-0.67 ng/mL], P < 0.05), although it became insignificant thereafter. There was no significant difference in AST/ALT or creatinine at 10 years, although a transient AST/ALT elevation was observed in ITx. In regard to clinical events, the occurrence of severe hypoglycemia was 14% vs 31% (relative risk 0.46, P = 0.64), that of infectious disease was 43% vs 12% (relative risk 3.71, P = 0.09) and digestive symptoms was 43% vs 7.7% (relative risk 5.57, P = 0.05) in ITx vs MDI/CSII, respectively. No patient died in either group.

CONCLUSIONS

The present findings showed that ITx was considered to contribute to the reduction of hypoglycemia and better glycemic control with tolerable, but attention-requiring, risks over a period of 10 years compared with MDI/CSII.

Considerations for an Alternative Site of Islet Cell Transplantation

Islet cell transplantation has been limited most by poor graft survival. Optimizing the site of transplantation could improve clinical outcomes by minimizing required donor cells, increasing graft integration, and simplifying the transplantation and monitoring process. In this article, we review the history and significant human and animal data for clinically relevant sites, including the liver, spleen, and kidney subcapsule, and identify promising new sites for further research. While the liver was the first studied site and has been used the most in clinical practice, the majority of transplanted islets become necrotic. We review the potential causes for graft death, including the instant blood-mediated inflammatory reaction, exposure to immunosuppressive agents, and low oxygen tension. Significant research exists on alternative sites for islet cell transplantation, suggesting a promising future for patients undergoing pancreatectomy.

Targeting the receptor for advanced glycation end products (RAGE) in type 1 diabetes

Type 1 diabetes (T1D) is one of the most common chronic diseases manifesting in early life, with the prevalence increasing worldwide at a rate of approximately 3% per annum. The prolonged hyperglycaemia characteristic of T1D upregulates the receptor for advanced glycation end products (RAGE) and accelerates the formation of RAGE ligands, including advanced glycation end products, high-mobility group protein B1, S100 calcium-binding proteins, and amyloid-beta. Interestingly, changes in the expression of RAGE and these ligands are evident in patients before the onset of T1D. RAGE signals via various proinflammatory cascades, resulting in the production of reactive oxygen species and cytokines. A large number of proinflammatory ligands that can signal via RAGE have been implicated in several chronic diseases, including T1D. Therefore, it is unsurprising that RAGE has become a potential therapeutic target for the treatment and prevention of disease. In this review, we will explore how RAGE might be targeted to prevent the development of T1D.

Insulin-Producing Cell Transplantation Platform for Veterinary Practice

Diabetes mellitus (DM) remains a global concern in both human and veterinary medicine. Type I DM requires prolonged and consistent exogenous insulin administration to address hyperglycemia, which can increase the risk of diabetes complications such as retinopathy, nephropathy, neuropathy, and heart disorders. Cell-based therapies have been successful in human medicine using the Edmonton protocol. These therapies help maintain the production of endogenous insulin and stabilize blood glucose levels and may possibly be adapted to veterinary clinical practice. The limited number of cadaveric pancreas donors and the long-term use of immunosuppressive agents are the main obstacles for this protocol. Over the past decade, the development of potential therapies for DM has mainly focused on the generation of effective insulin-producing cells (IPCs) from various sources of stem cells that can be transplanted into the body. Another successful application of stem cells in type I DM therapies is transplanting generated IPCs. Encapsulation can be an alternative strategy to protect IPCs from rejection by the body due to their immunoisolation properties. This review summarizes current concepts of IPCs and encapsulation technology for veterinary clinical application and proposes a potential stem-cell-based platform for veterinary diabetic regenerative therapy.

Carbogen gas-challenge BOLD fMRI in assessment of liver hypoxia after portal microcapsules implantation

Background

Hypoxia is one of the key factors affecting the survival of islet cells transplanted via the portal vein. Blood oxygen level dependent functional magnetic resonance imaging (BOLD-fMRI) is the only imaging technique that can detect the level of blood oxygen level in vivo. However, so far no study has indicated that BOLD-fMRI can be applied to monitor the liver oxygen level after islet transplantation.

Objective

To evaluate the value of Carbogen-challenge BOLD MRI in assessing the level of hypoxia in liver tissue after portal microcapsules implanted.

Methods

Fifty-one New Zealand rabbits were randomly divided into three experimental groups (15 in each group) were transplanted microencapsulated 1000 microbeads/kg (PV1 group), 3000 microbeads/kg (PV2 group), 5000 microbeads/kg (PV3 group), and 6 rabbits were injected with the same amount of saline as the control group, BOLD-fMRI was performed following carbogen breathing in each group after transplantation on 1d, 2d, 3d and 7d, T2* weighted image, R2* value and ΔR2* value parameters for the liver tissue. Pathological examinations including liver gross pathology, H&E staining and pimonidazole immunohistochemistry were performed after BOLD-fMRI. The differences of pathological results among each group were compared. The ΔR2* values and transplanted doses were analyzed.

Results and conclusions

ΔR2* values at the 1-3d and 7d after transplantation were significantly different in each groups (P<0.05). ΔR2* values decreased gradually with the increase of transplanted dose, and was negatively correlated with transplant dose at 3d after transplantation (r = -0.929, P <0.001). Liver histopathological examination showed that the degree of hypoxia of liver tissue increased with the increase of transplanted doses, Carbogen-challenge BOLD-fMRI can assess the degree of liver hypoxia after portal microcapsules implanted, which provided a monitoring method for early intervention.