Islet transplantation as a treatment for diabetes - a work in progress

Nanomedicine in the Treatment of Diabetes

Nanomedicine could improve the treatment of diabetes by exploiting various therapeutic mechanisms through the use of suitable nanoformulations. For example, glucose-sensitive nanoparticles can release insulin in response to high glucose levels, mimicking the physiological release of insulin. Oral nanoformulations for insulin uptake via the gut represent a long-sought alternative to subcutaneous injections, which cause pain, discomfort, and possible local infection. Nanoparticles containing oligonucleotides can be used in gene therapy and cell therapy to stimulate insulin production in β-cells or β-like cells and modulate the responses of T1DM-associated immune cells. In contrast, viral vectors do not induce immunogenicity. Finally, in diabetic wound healing, local delivery of nanoformulations containing regenerative molecules can stimulate tissue repair and thus provide a valuable tool to treat this diabetic complication. Here, we describe these different approaches to diabetes treatment with nanoformulations and their potential for clinical application.

Pancreatic beta-cell mass and function and therapeutic implications of using antidiabetic medications in type 2 diabetes

Nowadays, the focus of diabetes treatment has switched from lowering the glucose level to preserving glycemic homeostasis and slowing the disease progression. The main pathophysiology of both type 1 diabetes and long-standing type 2 diabetes is pancreatic β-cell mass loss and dysfunction. According to recent research, human pancreatic β-cells possess the ability to proliferate in response to elevated insulin demands. It has been demonstrated that in insulin-resistant conditions in humans, such as obesity or pregnancy, the β-cell mass increases. This ability could be helpful in developing novel treatment approaches to restore a functional β-cell mass. Treatment strategies aimed at boosting β-cell function and mass may be a useful tool for managing diabetes mellitus and stopping its progression. This review outlines the processes of β-cell failure and detail the many β-cell abnormalities that manifest in people with diabetes mellitus. We also go over standard techniques for determining the mass and function of β-cells. Lastly, we provide the therapeutic implications of utilizing antidiabetic drugs in controlling the mass and function of pancreatic β-cells.

Global scientific trends on the islet transplantation in the 21st century: A bibliometric and visualized analysis

BACKGROUND

Islet transplantation (IT) has emerged as a significant research area for the treatment of diabetes mellitus and has witnessed a surge in scholarly attention. Despite its growing importance, there is a lack of bibliometric analyses that encapsulate the evolution and scientific underpinnings of this field. This study aims to fill this gap by conducting a comprehensive bibliometric analysis to delineate current research hotspots and forecast future trajectories within the IT domain with a particular focus on evidence-based medicine practices.

METHODS

This analysis scrutinized literature from January 1, 2000, to October 1, 2023, using the Web of Science Core Collection (WoSCC). Employing bibliometric tools such as VOSviewer, CiteSpace, and the R package "bibliometrix," we systematically evaluated the literature to uncover scientific trends and collaboration networks in IT research.

RESULTS

The analysis revealed 8388 publications from 82 countries, predominantly the United States and China. However, global cross-institutional collaboration in IT research requires further strengthening. The number of IT-related publications has increased annually. Leading research institutions in this field include Harvard University, the University of Alberta, the University of Miami, and the University of Minnesota. "Transplantation" emerges as the most frequently cited journal in this area. Shapiro and Ricordi were the most prolific authors, with 126 and 121 publications, respectively. Shapiro also led to co-citations, totaling 4808. Key research focuses on IT sites and procedures as well as novel therapies in IT. Emerging research hotspots are identified by terms like "xenotransplantation," "apoptosis," "stem cells," "immunosuppression," and "microencapsulation."

CONCLUSIONS

The findings underscore a mounting anticipation for future IT research, which is expected to delve deeper into evidence-based methodologies for IT sites, procedures, and novel therapeutic interventions. This shift toward evidence-based medicine underscores the field's commitment to enhancing the efficacy and safety of IT for diabetes treatment, signaling a promising direction for future investigations aimed at optimizing patient outcomes.

Medical, pharmaceutical, and nutritional applications of 3D-printing technology in diabetes

AIMS

Despite numerous studies covering the various features of three-dimensional printing (3D printing) technology, and its applications in food science and disease treatment, no study has yet been conducted to investigate applying 3D printing in diabetes. Therefore, the present study centers on the utilization and impact of 3D printing technology in relation to the nutritional, pharmaceutical, and medicinal facets of diabetes management. It highlights the latest advancements, and challenges in this field.

METHODS

In this review, the articles focusing on the application and effect of 3D printing technology on medical, pharmaceutical, and nutritional aspects of diabetes management were collected from different databases.

RESULT

High precision of 3D printing in the placement of cells led to accurate anatomic control, and the possibility of bio-printing pancreas and β-cells. Transdermal drug delivery via 3D-printed microneedle (MN) patches was beneficial for the management of diabetes disease. 3D printing supported personalized medicine for Diabetes Mellitus (DM). For instance, it made it possible for pharmaceutical companies to manufacture unique doses of medications for every diabetic patient. Moreover, 3D printing allowed the food industry to produce high-fiber and sugar-free products for the individuals with DM.

CONCLUSIONS

In summary, applying 3D printing technology for diabetes management is in its early stages, and needs to be matured and developed to be safely used for humans. However, its rapid progress in recent years showed a bright future for the treatment of diabetes.

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.

Pancreatic Islet Biobanking Facilities in India: The Need of the Hour to Deal with Diabetes?

Endocrine pancreas regulates glucose homeostasis and prevents diabetes. Type-1 diabetes is characterized by destruction of the insulin secreting β-cells within the endocrine pancreatic islets, resulting in lower insulin release. People with type-1 diabetes can be transplanted with pancreatic islets obtained from deceased donors which restores the β-cell function. There are around 70 human islet isolation centers around the world which mostly collect endocrine pancreas from deceased donors. They assess the islet yield, functionality, viability, secretory capacity, and purity for transplantation and distribute this to donors. They also distribute a part of the pancreatic tissue for research, so that the cellular mechanisms in the human pancreatic tissue can be understood. This is crucial since human islet tissue has a unique cytoarchitecture compared to murine counterparts and therefore islet research with murine islets does not give complete picture of diabetes in humans. India is poised to take the mantle of the diabetes capital of the world in the near future. Despite this, there are no human islet isolation centers which can facilitate islet transplantation and diabetes research in India. This article highlights the glaring gap in the current infrastructure for diabetes care and provides critical insights into the role and potential of setting up islet tissue banks in the most populous country of the world.

Biomedical importance of the ubiquitin-proteasome system in diabetes and metabolic transdifferentiation of pancreatic duct epithelial cells into β-cells

The ubiquitin-proteasome system (UPS) is a major pathway for cellular protein degradation. The molecular function of the UPS is the removal of damaged proteins, and this function is applied in many biological processes, including inflammation, proliferation, and apoptosis. Accumulating evidence also suggests that the UPS also has a key role in pancreatic β-cell transdifferentiation in diabetes and can be targeted for treatment of diabetic diseases. In this review, we summarized the mechanistic roles of the UPS in the biochemical activities of pancreatic β-cells, including the role of the UPS in insulin synthesis and secretion, as well as β-cell degradation. Also, we discuss how the UPS mediates the transdifferentiation of pancreatic duct epithelial cells into β-cells as the experimental basis for the development of new strategies for the treatment of diabetes in regenerative medicine.

Partially Oxidized Alginate as a Biodegradable Carrier for Glucose-Responsive Insulin Delivery and Islet Cell Replacement Therapy

Self-regulated insulin delivery that mimics native pancreas function has been a long-term goal for diabetes therapies. Two approaches towards this goal are glucose-responsive insulin delivery and islet cell transplantation therapy. Here, biodegradable, partially oxidized alginate carriers for glucose-responsive nanoparticles or islet cells are developed. Material composition and formulation are tuned in each of these contexts to enable glycemic control in diabetic mice. For injectable, glucose-responsive insulin delivery, 0.5 mm 2.5% oxidized alginate microgels facilitate repeat dosing and consistently provide 10 days of glycemic control. For islet cell transplantation, 1.5 mm capsules comprised of a blend of unoxidized and 2.5% oxidized alginate maintain cell viability and glycemic control over a period of more than 2 months while reducing the volume of nondegradable material implanted. These data show the potential of these biodegradable carriers for controlled drug and cell delivery for the treatment of diabetes with limited material accumulation in the event of multiple doses.

Islet allografts expressing a PD-L1 and IDO fusion protein evade immune rejection and reverse preexisting diabetes in immunocompetent mice without systemic immunosuppression

Allogeneic islet transplantation is a promising experimental therapy for poorly controlled diabetes. Despite pharmacological immunosuppression, long-term islet engraftment remains elusive. Here, we designed a synthetic fusion transgene coupling PD-L1 and indoleamine dioxygenase [hereafter PIDO] whose constitutive expression prevents immune destruction of genetically engineered islet allograft transplanted in immunocompetent mice. PIDO expressing murine islets maintain robust dynamic insulin secretion in vitro and when transplanted in allogeneic hyperglycemic murine recipients reverse pre-existing streptozotocin-induced and autoimmune diabetes in the absence of pharmacological immunosuppression for more than 50 and 8 weeks, respectively, and is dependent on host CD4 competence. Additionally, PIDO expression in allografts preserves endocrine functional viability of islets and promotes a localized tolerogenic milieu characterized by the suppression of host CD8 T cell and phagocyte recruitment and accumulation of FOXP3⁺ Tregs. Furthermore, in the canine model of xenogeneic islet transplantation, muscle implanted PIDO-expressing porcine islets displayed physiological glucose-responsive insulin secretion competency in euglycemic recipient for up to 20 weeks. In conclusion, the PIDO transgenic technology enables host CD4⁺ T cell-modulated immune evasiveness and long-term functional viability of islet allo- and xenografts in immune-competent recipients without the need for pharmacological immune suppression and would allow for improved outcomes for tissue transplantation.

Antigen-specific immunotherapies in type 1 diabetes

Type 1 diabetes mellitus (T1DM) is an autoimmune disease caused by the destruction of pancreatic beta cells, in which immune system disorder plays an important role. Finding a cure for T1DM and restoring beta cell function has been a long-standing goal. Research has shown that immune regulation with pancreatic islet auto-antigens may be the most specific and safe treatment for T1DM. Immunological intervention using diabetogenic auto-antigens as a target can help identify T1DM in high-risk individuals by early screening of autoantibodies (AAbs) before the loss of pancreatic islet function and thus achieve primary prevention of T1DM. However, induction of self-tolerance in patients with pre-diabetes can also slow down the attack of autoimmunity, and achieve secondary prevention. Antigen-based immune therapy opens up new avenues for the prevention and treatment of T1DM. The zinc transporter 8 (ZnT8) protein, presents in the serum of pre-diabetic and diabetic patients, is immunogenic and can cause T1D autoimmune responses. ZnT8 has become a potential target of humoral autoimmunity; it is of great significance for the early diagnosis of T1D. ZnT8-specific CD8⁺ T cells can be detected in most T1DM patients, and play a key role in the progression of T1D. As an immunotherapy target, it can improve the dysfunction of beta cells in T1DM and provide new ideas for the treatment of T1D. In this review, we summarize research surrounding antigen-specific immunotherapies (ASI) over the past 10 years and the ZnT8 antigen as an autoimmune target to induce self-tolerance for T1DM.

Nanotechnology in Kidney and Islet Transplantation: An Ongoing, Promising Field

Organ transplantation has evolved rapidly in recent years as a reliable option for patients with end-stage organ failure. However, organ shortage, surgical risks, acute and chronic rejection reactions and long-term immunosuppressive drug applications and their inevitable side effects remain extremely challenging problems. The application of nanotechnology in medicine has proven highly successful and has unique advantages for diagnosing and treating diseases compared to conventional methods. The combination of nanotechnology and transplantation brings a new direction of thinking to transplantation medicine. In this article, we provide an overview of the application and progress of nanotechnology in kidney and islet transplantation, including nanotechnology for renal pre-transplantation preservation, artificial biological islets, organ imaging and drug delivery.

Alpha-Lipoic Acid Inhibits Spontaneous Diabetes and Autoimmune Recurrence in Non-Obese Diabetic Mice by Enhancing Differentiation of Regulatory T Cells and Showed Potential for Use in Cell Therapies for the Treatment of Type 1 Diabetes

Type 1 diabetes (T1D) is caused by the destruction of β cells in pancreatic islets by autoimmune T cells. Islet transplantation has been established as an effective treatment for T1D. However, the survival of islet grafts is often disrupted by recurrent autoimmunity. Alpha-lipoic acid (ALA) has been reported to have immunomodulatory effects and, therefore, may have therapeutic potential in the treatment of T1D. In this study, we investigated the therapeutic potential of ALA in autoimmunity inhibition. We treated non-obese diabetic (NOD) mice with spontaneous diabetes and islet-transplantation mice with ALA. The onset of diabetes was decreased and survival of the islet grafts was extended. The populations of Th1 cells decreased, and regulatory T cells (Tregs) increased in ALA-treated mice. The in vitro Treg differentiation was significantly increased by treatment with ALA. The adoptive transfer of ALA-differentiated Tregs into NOD recipients improved the outcome of the islet grafts. Our results showed that in vivo ALA treatment suppressed spontaneous diabetes and autoimmune recurrence in NOD mice by inhibiting the Th1 immune response and inducing the differentiation of Tregs. Our study also demonstrated the therapeutic potential of ALA in Treg-based cell therapies and islet transplantation used in the treatment of T1D.

A One-Step, Monolayer Culture and Chemical-Based Approach to Generate Insulin-Producing Cells From Human Adipose-Derived Stem Cells to Mitigate Hyperglycemia in STZ-Induced Diabetic Rats

The global population of individuals afflicted with diabetes mellitus has been increasing year by year, and this disease poses a serious threat to human health as well as the economies worldwide. Pancreatic or islet transplantations provide one of the most effective and long-term therapies available to treat diabetes, but the scarcity and quality of pancreatic islets limit their use in treatments. Here, we report the development of a one-step, monolayer culture, and chemical-based protocol that efficiently mediates the differentiation of human adipose-derived stem cells (hADSCs) into insulin-producing cells (IPCs). Our data indicate that hADSCs in monolayer culture that are allowed to differentiate into IPCs are superior to those in suspension cultures with respect to insulin secretion capacity (213-fold increase), cell viability (93.5 ± 3.27% vs. 41.67 ± 13.17%), and response to glucose stimulation. Moreover, the expression of genes associated with pancreatic lineage specification, such as PDX1, ISL1, and INS (encoding insulin), were expressed at significantly higher levels during our differentiation protocol (6-fold for PDX1 and ISL1, 11.5-fold for INS). Importantly, in vivo studies demonstrated that transplantation with IPCs significantly mitigated hyperglycemia in streptozotocin-induced diabetic rats. Our results indicate that this one-step, rapid protocol increases the efficiency of IPC generation and that the chemical-based approach for IPC induction may reduce safety concerns associated with the use of IPCs for clinical applications, thereby providing a safe and effective cell-based treatment for diabetes.

Adhesion Characteristics of Human Pancreatic Islets, Duct Epithelial Cells, and Acinar Cells to a Polymer Scaffold

We reported in 2018 that among several extracellular matrices, fibronectin, type I collagen, type IV collagen, laminin I, fibrinogen, and bovine serum albumin, fibronectin is particularly useful for adhesion of porcine pancreatic tissue. Subsequently, we developed a technology that enables the chemical coating of the constituent motifs of fibronectin onto cell culture dishes. In this experiment, we used islets (purity ≥ 90%), duct epithelial cells (purity ≥ 60%), and acinar cells (purity ≥ 99%) isolated from human pancreas according to the Edmonton protocol published in 2000 and achieved adhesion to the constituent motifs of fibronectin. A solution including cGMP Prodo Islet Media was used as the assay solution. In islets, adhesion was enhanced with the constitutive motifs of fibronectin compared with uncoated islets. In the functional evaluation of islets, insulin mRNA expression and insulin secretion were enhanced by the constitutive motif of fibronectin compared with non-coated islets. The stimulation index was comparable between non-coated islets and fibronectin motifs. In duct epithelial cells, adhesion was mildly promoted by the fibronectin component compared with non-coated component, while in acinar cells, adhesion was inhibited by the fibronectin component compared with the non-coated component. These data suggest that the constitutive motifs of fibronectin are useful for the adhesion of islets and duct epithelial cells.

Successful Islet Outcomes Using Australia-Wide Donors: A National Centre Experience

Cold ischemia and hence travel time can adversely affect outcomes of islet isolation. The aim of this study was to compare the isolation and transplant outcomes of donor pancreata according to the distance from islet isolation facility. Principally, those within a 50 km radius of the centre were compared with those from regional areas within the state and those from interstate donors within Australia. Organ donors were categorised according to distance from National Pancreas Transplant Unit Westmead (NPTU). Donor characteristics were analysed statistically against islet isolation outcomes. These were age, BMI, cause and mechanism of death, days in ICU, gender, inotrope and steroid use, cold ischemia time (CIT) and retrieval surgical team. Between March 2007 and December 2020, 297 islet isolations were performed at our centre. A total of 149 donor pancreata were local area, and 148 non-local regions. Mean distance from the isolation facility was 780.05 km. Mean pancreas CIT was 401.07 ± 137.71 min and was significantly different between local and non-local groups (297.2 vs. 487.5 min, p < 0.01). Mean age of donors was 45.22 years, mean BMI was 28.82, sex ratio was 48:52 F:M and mean time in ICU was 3.07 days. There was no significant difference between local and non-local for these characteristics. The mean CIT resulting in islet transplantation was 297.1 ± 91.5 min and longest CIT resulting in transplantation was 676 min. There was no significant difference in islet isolation outcomes between local and non-local donors for characteristics other than CIT. There was also no significant effect of distance from the isolation facility on positive islet transplant outcomes (C-peptide > 0.2 at 1 month post-transplant). Conclusions: Distance from the isolation centre did not impact on isolation or transplant outcomes supporting the ongoing nationwide use of shipping pancreata for islet isolation and transplantation.

Current treatment options and challenges in patients with Type 1 diabetes: Pharmacological, technical advances and future perspectives

Type 1 diabetes mellitus imposes a significant burden of complications and mortality, despite important advances in treatment: subjects affected by this disease have also a worse quality of life-related to disease management. To overcome these challenges, different new approaches have been proposed, such as new insulin formulations or innovative devices. The introduction of insulin pumps allows a more physiological insulin administration with a reduction of HbA1c level and hypoglycemic risk. New continuous glucose monitoring systems with better accuracy have allowed, not only better glucose control, but also the improvement of the quality of life. Integration of these devices with control algorithms brought to the creation of the first artificial pancreas, able to independently gain metabolic control without the risk of hypo- and hyperglycemic crisis. This approach has revolutionized the management of diabetes both in terms of quality of life and glucose control. However, complete independence from exogenous insulin will be obtained only by biological approaches that foresee the replacement of functional beta cells obtained from stem cells: this will be a major challenge but the biggest hope for the subjects with type 1 diabetes. In this review, we will outline the current scenario of innovative diabetes management both from a technological and biological point of view, and we will also forecast some cutting-edge approaches to reduce the challenges that hamper the definitive cure of diabetes.

Solid Organ Bioprinting: Strategies to Achieve Organ Function

The field of tissue engineering has advanced over the past decade, but the largest impact on human health should be achieved with the transition of engineered solid organs to the clinic. The number of patients suffering from solid organ disease continues to increase, with over 100 000 patients on the U.S. national waitlist and approximately 730 000 deaths in the United States resulting from end-stage organ disease annually. While flat, tubular, and hollow nontubular engineered organs have already been implanted in patients, in vitro formation of a fully functional solid organ at a translatable scale has not yet been achieved. Thus, one major goal is to bioengineer complex, solid organs for transplantation, composed of patient-specific cells. Among the myriad of approaches attempted to engineer solid organs, 3D bioprinting offers unmatched potential. This review highlights the structural complexity which must be engineered at nano-, micro-, and mesostructural scales to enable organ function. We showcase key advances in bioprinting solid organs with complex vascular networks and functioning microstructures, advances in biomaterials science that have enabled this progress, the regulatory hurdles the field has yet to overcome, and cutting edge technologies that bring us closer to the promise of engineered solid organs.

Transplant strategies for type 1 diabetes: whole pancreas, islet and porcine beta cell therapies

Whole-organ pancreas and islet transplantations are performed in a highly selected group of patients with diabetes mellitus, primarily those with type 1 diabetes mellitus, complicated by recurrent severe hypoglycaemia or renal failure requiring kidney transplantation. Clinical accessibility to pancreases or islets, and patient characteristics and therapeutic goals, may dictate choice of procedure. Pancreas transplantation is most often performed simultaneous with a kidney transplant, but patients with particularly labile type 1 diabetes may be considered for a pancreas transplant alone. While highly successful at restoring insulin independence, pancreas transplants carry the significant risks of major surgery and immunosuppression. Islet transplantation is a relatively minor procedure, usually performed for labile type 1 diabetes with severe hypoglycaemia. It is highly successful at resolving hypoglycaemia, but more than one pancreas donor may be required for insulin independence. Both pancreas and islet transplantation are limited in applicability by a paucity of deceased donors. Pigs provide one promising replenishable source of islets. Porcine islets can successfully reverse diabetes mellitus in non-human primates under the appropriate immunosuppressive conditions, with promise for eventually translating this success to a larger population of patients with diabetes mellitus in the future. Graphical abstract.

Pancreatic Islet Cell Transplantation: Graft Stability and Metabolic Outcomes

Pancreatic islet transplantation is a rapidly evolving field. It has been increasingly regarded as a promising approach for the correction of dysglycemia associated with type 1 diabetes mellitus (allogenic islet transplantation), or the prevention of surgical diabetes in chronic pancreatitis subjects undergoing total pancreatectomy (autologous islet transplantation). In this review, we discuss the latest literature pertaining to metabolic outcomes of autologous and allogenic islet transplantation, shedding close light on our own latest experience in the autologous islet transplantation setting.

Nanotechnology Approaches to Modulate Immune Responses to Cell-based Therapies for Type 1 Diabetes

Islet transplantation is a promising curative treatment option for type 1 diabetes (T1D) as it can provide physiological blood glucose control. The widespread utilization of islet transplantation is limited due to systemic immunosuppression requirements, persisting graft immunodestruction, and poor islet engraftment. Traditional macro- and micropolymeric encapsulation strategies can alleviate the need for antirejection immunosuppression, yet the increased graft volume and diffusional distances imparted by these coatings can be detrimental to graft viability and glucose control. Additionally, systemic administration of pro-engraftment and antirejection therapeutics leaves patients vulnerable to adverse off-target side effects. Nanoscale engineering techniques can be used to immunocamouflage islets, modulate the transplant microenvironment, and provide localized pro-engraftment cues. In this review, we discuss the applications of nanotechnology to advance the clinical potential of islet transplantation, with a focus on cell surface engineering, bioactive functionalization, and use of nanoparticles in T1D cell-based treatments.

The Clinical Efficacy and Safety of Stem Cell Therapy for Diabetes Mellitus: A Systematic Review and Meta-Analysis

Diabetes mellitus (DM) is a chronic metabolic disease with high morbidity and mortality. Recently, stem cell-based therapy for DM has shown considerable promise. Here, we undertook a systematic review and meta-analysis of published clinical studies to evaluate the efficacy and safety of stem cell therapy for both type 1 DM (T1DM) and type 2 DM (T2DM). The PubMed, Cochrane Central Register of Controlled Trials, EMBASE, and ClinicalTrials.gov databases were searched up to November 2018. We employed a fixed-effect model using 95% confidence intervals (CIs) when no statistically significant heterogeneity existed. Otherwise, a random-effects statistical model was used. Twenty-one studies met our inclusion criteria: ten T1DM studies including 226 patients and eleven T2DM studies including 386 patients. Stem cell therapy improved C-peptide levels (mean difference (MD), 0.41; 95% CI, 0.06 to 0.76) and glycosylated hemoglobin (HbA1c; MD, -3.46; 95% CI, -6.01 to -0.91) for T1DM patients. For T2DM patients, stem cell therapy improved C-peptide levels (MD, 0.33; 95% CI, 0.07 to 0.59), HbA1c (MD, -0.87; 95% CI, -1.37 to -0.37) and insulin requirements (MD, -35.76; 95% CI, -40.47 to -31.04). However, there was no significant change in fasting plasma glucose levels (MD, -0.52; 95% CI, -1.38 to 0.34). Subgroup analyses showed significant HbA1c and C-peptide improvements in patients with T1DM treated with bone marrow hematopoietic stem cells (BM-HSCs), while there was no significant change in the mesenchymal stem cell (MSC) group. In T2DM, HbA1c and insulin requirements decreased significantly after MSC transplantation, and insulin requirements and C-peptide levels were significantly improved after bone marrow mononuclear cell (BM-MNC) treatment. Stem cell therapy is a relatively safe and effective method for selected individuals with DM. The data showed that BM-HSCs are superior to MSCs in the treatment of T1DM. In T2DM, MSC and BM-MNC transplantation showed favorable therapeutic effects.

Translational Research Symposium-collaborative efforts as driving forces of healthcare innovation

The 5th Translational Research Symposium was organised at the annual meeting of the European Society for Biomaterials 2018, Maastricht, the Netherlands, with emphasis on the future of emerging and smart technologies for healthcare in Europe. Invited speakers from academia and industry highlighted the vision and expectations of healthcare in Europe beyond 2020 and the perspectives of innovation stakeholders, such as small and medium enterprises, large companies and Universities. The aim of the present article is to summarise and explain the main statements made during the symposium, with particular attention on the need to identify unmet clinical needs and their efficient translation into healthcare solutions through active collaborations between all the participants involved in the value chain.

Necrostatin-1 supplementation enhances young porcine islet maturation and in vitro function

BACKGROUND

Necroptosis has been demonstrated to be a primary mechanism of islet cell death. This study evaluated whether the supplementation of necrostatin-1 (Nec-1), a potent inhibitor of necroptosis, to islet culture media could improve the recovery, maturation, and function of pre-weaned porcine islets (PPIs).

METHODS

PPIs were isolated from pre-weaned Yorkshire piglets (8-15 days old) and either cultured in control islet culture media (n = 6) or supplemented with Nec-1 (100 µM, n = 5). On days 3 and 7 of culture, islets were assessed for recovery, insulin content, viability, cellular composition, GLUT2 expression in beta cells, differentiation of pancreatic endocrine progenitor cells, function, and oxygen consumption rate.

RESULTS

Nec-1 supplementation induced a 2-fold increase in the insulin content of PPIs on day 7 of culture. When compared to untreated islets, Nec-1 treatment doubled the beta- and alpha-cell composition and accelerated the development of delta cells. Additionally, beta cells of Nec-1-treated islets had a significant upregulation in GLUT2 expression. The enhanced development of major endocrine cells and GLUT2 expression after Nec-1 treatment subsequently led to a significant increase in the amount of insulin secreted in response to in vitro glucose challenge. Islet recovery, viability, and oxygen consumption rate were unaffected by Nec-1.

CONCLUSION

This study underlines the importance of necroptosis in islet cell death after isolation and demonstrates the novel effects of Nec-1 to increase islet insulin content, enhance pancreatic endocrine cell development, facilitate GLUT2 upregulation in beta cells, and augment insulin secretion. Nec-1 supplementation to culture media significantly improves islet quality prior to xenotransplantation.

Targeted therapy in chronic diseases using nanomaterial-based drug delivery vehicles

The application of nanomedicines is increasing rapidly with the promise of targeted and efficient drug delivery. Nanomedicines address the shortcomings of conventional therapy, as evidenced by several preclinical and clinical investigations indicating site-specific drug delivery, reduced side effects, and better treatment outcome. The development of suitable and biocompatible drug delivery vehicles is a prerequisite that has been successfully achieved by using simple and functionalized liposomes, nanoparticles, hydrogels, micelles, dendrimers, and mesoporous particles. A variety of drug delivery vehicles have been established for the targeted and controlled delivery of therapeutic agents in a wide range of chronic diseases, such as diabetes, cancer, atherosclerosis, myocardial ischemia, asthma, pulmonary tuberculosis, Parkinson's disease, and Alzheimer's disease. After successful outcomes in preclinical and clinical trials, many of these drugs have been marketed for human use, such as Abraxane®, Caelyx®, Mepact®, Myocet®, Emend®, and Rapamune®. Apart from drugs/compounds, novel therapeutic agents, such as peptides, nucleic acids (DNA and RNA), and genes have also shown potential to be used as nanomedicines for the treatment of several chronic ailments. However, a large number of extensive clinical trials are still needed to ensure the short-term and long-term effects of nanomedicines in humans. This review discusses the advantages of various drug delivery vehicles for better understanding of their utility in terms of current medical needs. Furthermore, the application of a wide range of nanomedicines is also described in the context of major chronic diseases.

Bioprinting an Artificial Pancreas for Type 1 Diabetes

PURPOSE OF REVIEW

Pancreatic islet cell transplantation is currently the only curative cell therapy for type 1 diabetes mellitus. However, its potential to treat many more patients is limited by several challenges. The emergence of 3D bioprinting technology from recent advances in 3D printing, biomaterials, and cell biology has provided the means to overcome these challenges.

RECENT FINDINGS

3D bioprinting allows for the precise fabrication of complex 3D architectures containing spatially distributed cells, biomaterials (bioink), and bioactive factors. Different strategies to capitalize on this ability have been investigated for the 3D bioprinting of pancreatic islets. In particular, with co-axial bioprinting technology, the co-printability of islets with supporting cells such as endothelial progenitor cells and regulatory T cells, which have been shown to accelerate revascularization of islets and improve the outcome of various transplantations, respectively, has been achieved. 3D bioprinting of islets for generation of an artificial pancreas is a newly emerging field of study with a vast potential to improve islet transplantation.

Autologous Mesenchymal Stem Cell Transplant in Patients with Type 1 Diabetes Mellitus

OBJECTIVES

Our goal was to determine the efficacy of autologous mesenchymal stem cell transplant for treatment in patients with type 1 diabetes mellitus.

MATERIALS AND METHODS

We examined 5 patients (4 male, 1 female; age 20-42 y) with type 1 diabetes mellitus who received autologous mesenchymal stem cell transplant (cells were obtained from the patient's iliac crest and cultured for 3-4 weeks) performed by intravenous infusion. The quantity of autologous mesenchymal stem cells infused was 95 to 97 × 106. We analyzed daily insulin dosages and leptin and glycated hemoglobin levels in patients before and 1, 2, and 3 months after their autologous mesenchymal stem cell transplant procedure.

RESULTS

In patients with type 1 diabetes mellitus, autologous mesenchymal stem cell transplant led to a decrease in daily insulin dosage levels, from 63 ± 8.83 to 50.2 ± 12.1 U (P = .064) after 1 month, with significantly increased leptin levels and trend to decreased glycated hemoglobin levels, from 6.86 to 10.77 ng/mL (P = .016) and 9.11% to 8.74% (P = .84) after 3 months, respectively.

CONCLUSIONS

Daily insulin dosage level decreased within 1 month and leptin levels increased significantly within 3 months after autologous mesenchymal stem cell transplant in patients with type 1 diabetes mellitus.

Polymeric Approaches to Reduce Tissue Responses Against Devices Applied for Islet-Cell Encapsulation

Immunoisolation of pancreatic islets is a technology in which islets are encapsulated in semipermeable but immunoprotective polymeric membranes. The technology allows for successful transplantation of insulin-producing cells in the absence of immunosuppression. Different approaches of immunoisolation are currently under development. These approaches involve intravascular devices that are connected to the bloodstream and extravascular devices that can be distinguished in micro- and macrocapsules and are usually implanted in the peritoneal cavity or under the skin. The technology has been subject of intense fundamental research in the past decade. It has co-evolved with novel replenishable cell sources for cure of diseases such as Type 1 Diabetes Mellitus that need to be protected for the host immune system. Although the devices have shown significant success in animal models and even in human safety studies most technologies still suffer from undesired tissue responses in the host. Here we review the past and current approaches to modulate and reduce tissue responses against extravascular cell-containing micro- and macrocapsules with a focus on rational choices for polymer (combinations). Choices for polymers but also choices for crosslinking agents that induce more stable and biocompatible capsules are discussed. Combining beneficial properties of molecules in diblock polymers or application of these molecules or other anti-biofouling molecules have been reviewed. Emerging are also the principles of polymer brushes that prevent protein and cell-adhesion. Recently also immunomodulating biomaterials that bind to specific immune receptors have entered the field. Several natural and synthetic polymers and even combinations of these polymers have demonstrated significant improvement in outcomes of encapsulated grafts. Adequate polymeric surface properties have been shown to be essential but how the surface should be composed to avoid host responses remains to be identified. Current insight is that optimal biocompatible devices can be created which raises optimism that immunoisolating devices can be created that allows for long term survival of encapsulated replenishable insulin-producing cell sources for treatment of Type 1 Diabetes Mellitus.

Tri-modal In vivo Imaging of Pancreatic Islets Transplanted Subcutaneously in Mice

PURPOSE

Transplantation of pancreatic islets (PIs) is a promising therapeutic approach for type 1 diabetes. The main obstacle for this strategy is that the outcome of islet engraftment depends on the engraftment site. It was our aim to develop a strategy for using non-invasive imaging techniques to assess the location and fate of transplanted PIs longitudinally in vivo.

PROCEDURES

In order to overcome the limitations of individual imaging techniques and cross-validate findings by different modalities, we have combined fluorine magnetic resonance imaging (F-19 MRI), fluorescence imaging (FLI), and bioluminescent imaging (BLI) for studying subcutaneously transplanted PIs and beta cell-like cells (INS-1E cell line) in vivo. We optimized the transduction (using lentiviral vectors) and labeling procedures (using perfluoro crown ether nanoparticles with a fluorescence dye) for PIs and INS-1E cell imaging.

RESULTS

The feasibility of using the proposed imaging methods for PI assessment was demonstrated both in vitro and in vivo. Our data suggested that F-19 MRI is suitable for high-resolution localization of transplanted cells and PIs; FLI is essential for confirmation of contrast localization by histology; and BLI is a reliable method to assess cell viability and survival after transplantation. No significant side effects on cell viability and function have been observed.

CONCLUSIONS

The proposed tri-modal imaging platform is a valuable approach for the assessment of engrafted PIs in vivo. It is potentially suitable for comparing different transplantation sites and evaluating novel strategies for improving PI transplantation technique in the future.

Development of a Coaxial 3D Printing Platform for Biofabrication of Implantable Islet-Containing Constructs

Over the last two decades, pancreatic islet transplantations have become a promising treatment for Type I diabetes. However, although providing a consistent and sustained exogenous insulin supply, there are a number of limitations hindering the widespread application of this approach. These include the lack of sufficient vasculature and allogeneic immune attacks after transplantation, which both contribute to poor cell survival rates. Here, these issues are addressed using a biofabrication approach. An alginate/gelatin-based bioink formulation is optimized for islet and islet-related cell encapsulation and 3D printing. In addition, a custom-designed coaxial printer is developed for 3D printing of multicellular islet-containing constructs. In this work, the ability to fabricate 3D constructs with precise control over the distribution of multiple cell types is demonstrated. In addition, it is shown that the viability of pancreatic islets is well maintained after the 3D printing process. Taken together, these results represent the first step toward an improved vehicle for islet transplantation and a potential novel strategy to treat Type I diabetes.

Local release of rapamycin by microparticles delays islet rejection within the anterior chamber of the eye

The anterior chamber of the eye (ACE) has emerged as a promising clinical islet transplantation site because of its multiple advantages over the conventional intra-hepatic portal site. This includes reduced surgical invasiveness and increased islet graft survival rate. It also allows for enhanced accessibility and monitoring of the islets. Although the ACE is initially an immuno-privileged site, this privilege is disrupted once the islet grafts are re-vascularized. Given that the ACE is a confined space, achieving graft immune tolerance through local immunosuppressive drug delivery is therefore feasible. Here, we show that islet rejection in the ACE of mice can be significantly suppressed through local delivery of rapamycin by carefully designed sustained-release microparticles. In this 30-day study, allogeneic islet grafts with blank microparticles were completely rejected 18 days post-transplantation into mice. Importantly, allogeneic islet grafts co-injected with rapamycin releasing microparticles into a different eye of the same recipient were preserved much longer, with some grafts surviving for more than 30 days. Hence, islet allograft survival was enhanced by a localized and prolonged delivery of an immunosuppressive drug. We envisage that this procedure will relieve diabetic transplant recipients from harsh systemic immune suppression, while achieving improved glycemic control and reduced insulin dependence.

The effect of different surface treatment methods on the physical, chemical and biological performances of a PGA scaffold

In order to improve the adhesion between a PGA scaffold and islet cells, it is necessary to find a suitable method to modify the scaffold. In this study, the PGA scaffold surface was modified by plasma, polylysine coating and plasma combined with polylysine coating (P–P-PGA). The surface adhesion of the modified PGA scaffold was examined, and the stretchability and infiltration of the PGA scaffold were also tested. Then, the PGA scaffold treated under the optimal treatment conditions was selected to co-culture with rat islet cells, and the survival activity of the rat islet cells on the untreated PGA scaffold and the P–P-PGA scaffold was examined via the MTT method. Rhodamine staining and DAPI staining were used to detect the number of islet cells adhered to four groups of scaffolds at different culture time points. The PGA-islet graft in the leg muscle of rats was stained with HE to perform the PGA-islet graft pathological examination. The experimental results showed that when the plasma treatment power was 240 W, the processing time was 4 min; the concentration of the polylysine coating solution was 2 mg ml⁻¹, the tensile strength of the PGA scaffold was 320.45 MPa and the amount of infiltration of the PGA scaffold by the serum medium presented the maximum value: 3.17 g g⁻¹. The MTT survival activity test results showed that after 3 d of culture, the survival activity of the islet cells of the treated PGA scaffold culture group (2.02 ± 0.13) was significantly different from the survival activity of the islet cells of the untreated PGA scaffold culture group (1.93 ± 0.10). The survival activities of the islet cells in the experimental groups (1.60 ± 0.13, 1.40 ± 0.12) were still higher than those of the control groups (0.96 ± 013, 0.69 ± 0.09) at 15 and 21 d. The results of the rhodamine and DAPI staining showed that with the increase in culture time, the number of the adherent cells in each group increased, and the number of the adherent islet cells in the experimental group was higher than that in the untreated group. The HE staining results showed that the islet cells on the P–P-PGA scaffold were more than those on the untreated PGA scaffold. After modification of the PGA scaffold, the adhesion of the islet cells improved, which was conducive to the growth of islet cells. These results confirmed that the plasma combined with polylysine coating treatment could enhance the adhesion of the PGA scaffold surface, so that the scaffold and the islet cells exhibited better adhesion and biocompatibility, and the modified PGA scaffold (P–P-PGA) could be used as a promising islet cell scaffold.

In order to improve the adhesion between a PGA scaffold and islet cells, it is necessary to find a suitable method to modify the scaffold.

Reduction of marginal mass required for successful islet transplantation in a diabetic rat model using adipose tissue-derived mesenchymal stromal cells

BACKGROUND AIMS

Adipose tissue-derived mesenchymal stromal cells (AT-MSCs), widely known as multipotent progenitors, release several cytokines that support cell survival and repair. There are in vitro and in vivo studies reporting the regenerative role of AT-MSCs possibly mediated by their protective effects on functional islet cells as well as their capacity to differentiate into insulin-producing cells (IPCs).

METHODS

On such a basis, our goal in the present study was to use three different models including direct and indirect co-cultures and islet-derived conditioned medium (CM) to differentiate AT-MSCs into IPCs and to illuminate the molecular mechanisms of the beneficial impact of AT-MSCs on pancreatic islet functionality. Furthermore, we combined in vitro co-culture of islets and AT-MSCs with in vivo assessment of islet graft function to assess whether co-transplantation of islets with AT-MSCs can reduce marginal mass required for successful islet transplantation and prolong graft function in a diabetic rat model.

RESULTS

Our findings demonstrated that AT-MSCs are suitable for creating a microenvironment favorable for the repair and longevity of the pancreas β cells through the improvement of islet survival and maintenance of cell morphology and insulin secretion due to their potent properties in differentiation. Most importantly, hybrid transplantation of islets with AT-MSCs significantly promoted survival, engraftment and insulin-producing function of the graft and reduced the islet mass required for reversal of diabetes.

CONCLUSIONS

This strategy might be of therapeutic potential solving the problem of donor islet material loss that currently limits the application of allogeneic islet transplantation as a more widespread therapy for type 1 diabetes.

A Comparison of Pancreatic Islet Purification using Iodixanol with University of Wisconsin Solution and with Na-Lactobionate and Histidine Solution

Purification of pancreatic islets is an important step in islet isolation for islet transplantation. In this study, to investigate how a solution composed mainly of Na-lactobionate and histidine (HL) influences the purification of islets, iodixanol was added to a purified solution for porcine islet isolation. A solution (IU) made by adding iodixanol to University of Wisconsin solution and a solution (IHL) made by adding iodixanol to HL solution were used to evaluate the islet isolation performance. We noted no significant differences between the two purification methods with regard to the islet yield, survival rate or purity, score, or stimulation index. These results show that IHL solution is as useful as IU solution for islet purification.

Adhesion characteristics of porcine pancreatic islets and exocrine tissue to coating materials

Since the report of the Edmonton protocol in 2000, islet transplantation has been implemented worldwide, and xenotransplantation using porcine islets has also been reported. In addition, many basic experiments using pancreatic islets and exocrine tissue after isolation have been reported. Recently, exocrine cells have been found to be essential for inducing the differentiation of pancreatic islets. Therefore, the importance of the culture conditions for pancreatic tissue when conducting experiments using pancreatic tissue is also increasing. In this study, we focused on the coat material and examined the adhesive properties of porcine pancreatic islets and exocrine tissue after isolation. Porcine islet isolation was performed, and isolated islets (purity ≥95%) and exocrine tissue (purity ≥99%) were used to achieve adhesion to several extracellular matrixes, fibronectin, collagen type I, collagen type IV, laminin I, fibrinogen, and bovine serum albumin (BSA). DMEM with 0.5% FBS was used as the assay medium. For exocrine tissue, the adhesion was promoted in fibronectin, collagen type I, laminin I, and fibrinogen. The adhesive ability to fibronectin was more than twice that to BSA, while the adhesive ability to collagen type I, laminin I, and fibrinogen was less than twice that to BSA. For islets, the adhesive ability to fibronectin was weaker than that of exocrine tissue. Furthermore, the adhesion effect in fibronectin was obtained within 30 minutes and in medium containing little serum for both islets and exocrine tissues. These data suggest that fibronectin may be useful for the adhesion of pancreatic tissue.

Sequential Coating of Insulin Secreting Beta Cells within Multilayers of Polysaccharide Nanogels

Pancreatic islet transplantation has emerged as a promising treatment for type-1 diabetes (T1D); however, its clinical application is still limited by the life-long use of immunosuppressive drugs, insufficient number of islets to achieve normoglycemia, and large transplantation volume. This paper reports a unique approach for nanothin coating of insulin secreting beta cell aggregates. The coating is based on hydrophobic and covalent interactions between natural acrylate modified cholesterol bearing pullulan (CHPOA) nanogels and MIN6 beta cell aggregates. Beta cell aggregates are prepared as spheroids through hanging drop method, which is optimized with respect to hanging drop volume and initial number of beta cells. These aggregates, defined as pseudoislets, are coated with sequential layers of nanogels and are evaluated as viable and functional for insulin secretion. Coating experiments are carried out using physiologically compatible medium, where pseudoislets are not brought in contact with toxic prepolymer solutions used in existing approaches. This study offers new opportunities through coating of islets with advanced functional materials under completely physiological conditions for clinical translation of cell transplantation technology. The technique developed here will establish a new paradigm for creating tolerable grafts for other chronic diseases such as anemia, cancer, central nervous system (CNS) diseases.

Transforming Growth Factor β1 in Patients with Type 2 Diabetes Mellitus After Fetal Pancreatic Stem Cell Transplant

OBJECTIVES

Our objective was to determine transforming growth factor β1 levels in patients with type 2 diabetes mellitus after fetal pancreatic stem cell transplant.

MATERIALS AND METHODS

We examined 10 patients (age range, 41-65 y) with type 2 diabetes mellitus, which we subsequently divided into 2 groups. Group 1 comprised 5 patients who received fetal pancreatic stem cell transplant (cells were 16-18 wk gestation) performed by intravenous infusion. Group 2 comprised 5 patients (control group) who were on hypoglycemic tablet therapy or insulin therapy. The quantity of fetal stem cells infused was 5 to 6 × 106. We analyzed transforming growth factor β1, C-peptide, and glycated hemoglobin levels in patients before and 3 months after fetal pancreatic stem cell transplant.

RESULTS

In patients with type 2 diabetes mellitus, fetal pancreatic stem cell transplant led to a significant increase in transforming growth factor β1 levels, from 16 364.8 to 35 730.4 ng/mL (P = .008), with trend in decreased glycated hemoglobin levels, from 7.96% to 6.98% (P = .088) after 3 months.

CONCLUSIONS

Transforming growth factor β1 levels increased significantly within 3 months after fetal pancreatic stem cell transplant in patients with type 2 diabetes mellitus.

Isl1β Overexpression With Key β Cell Transcription Factors Enhances Glucose-Responsive Hepatic Insulin Production and Secretion

Adenoviral gene transfer of key β cell developmental regulators including Pdx1, Neurod1, and Mafa (PDA) has been reported to generate insulin-producing cells in the liver. However, PDA insulin secretion is transient and glucose unresponsive. Here, we report that an additional β cell developmental regulator, insulin gene enhancer binding protein splicing variant (Isl1β), improved insulin production and glucose-responsive secretion in PDA mice. Microarray gene expression analysis suggested that adenoviral PDA transfer required an additional element for mature β cell generation, such as Isl1 and Elf3 in the liver. In vitro promoter analysis indicated that splicing variant Isl1, or Isl1β, is an important factor for transcriptional activity of the insulin gene. In vivo bioluminescence monitoring using insulin promoter-luciferase transgenic mice verified that adenoviral PDA + Isl1β transfer produced highly intense luminescence from the liver, which peaked at day 7 and persisted for more than 10 days. Using insulin promoter-GFP transgenic mice, we further confirmed that Isl1β supplementation to PDA augmented insulin-producing cells in the liver, insulin production and secretion, and β cell‒related genes. Finally, the PDA + Isl1β combination ameliorated hyperglycemia in diabetic mice for 28 days and enhanced glucose tolerance and responsiveness. Thus, our results suggest that Isl1β is a key additional transcriptional factor for advancing the generation of insulin-producing cells in the liver in combination with PDA.

Bibliometric analysis of the top-cited articles on islet transplantation

AIMS

To identify and characterize the top-cited articles in the field of islet transplantation.

METHODS

We used the Science Citation Index Expanded database to identify the most frequently cited articles published after 1900. Articles were evaluated using the following characteristics: citation number, publication year, study design, references, country and institution of origin, authorship, and journal. Keyword analysis and citation networks were used to analyze research trends.

RESULTS

The most frequently cited articles received between 146 and 2988 citations; the median was 291. All of the most frequently cited articles were published between 1972 and 2012, and 85 articles were published after 1990. The most popular study design involved basic science (75 articles). The leading countries were the United States (US) and Canada, and the leading institutions were the University of Alberta, Canada, and the University of Minnesota, in the US. Journals specializing in diabetes or transplantation published more than half of the articles (n = 53, 52%), with the journal Diabetes publishing the largest number (n = 30). No association was found between a journal's impact factor and the number of top-cited articles it published. There was no correlation between the number of citations and the number of years since publication, authors, participating institutions, or countries involved. Top-cited articles focused on 2 themes: the use of antirejection immunotherapy or biocompatible encapsulations to prolong graft survival, and assessments of the efficacy of islet transplants, in particular, islet allografts.

CONCLUSIONS

Our study can help researchers to identify and decipher the characteristics of top-cited articles in the field of islet transplantation. Just as clinically successful allografts are carried out using the Edmonton protocol, autografts and xenografts should be similarly strengthened to solve problems relating to immune rejection and islet sources, respectively.

Encapsulation of Human Islets Using a Biomimetic Self-Assembled Nanomatrix Gel for Protection against Cellular Inflammatory Responses

The major concern of pancreatic islet transplantation is that the implanted islets are exposed to the immune system of the recipient. To overcome this challenge, the peptide amphiphile (PA) nanomatrix gel was used for immunoisolation of islets through microencapsulation. The PA can self-assemble to form a nanomatrix gel with an extracellular matrix-mimicking, islet nurturing microenvironment and a semipermeable immune barrier. In this study, the islet protective effect of the PA nanomatrix gel was evaluated by coculture of PA-encapsulated human islets with differentiated U937 cells (human monocyte cell-line) for 3 and 7 days. The coculture of the bare islets with the differentiated U937 cells stimulated proinflammatory cytokine (IL-1β and TNF-α) secretion and caused islet death after 7 days, which simulated an early inflammatory response environment after islet transplantation. The PA-encapsulated islets, however, did not stimulate proinflammatory cytokine secretion and maintained islet viability up to 7 days. More insulin-producing β cells were observed when islets were PA-encapsulated than control islets with the differentiated U937 cells for 7 days compared to the bare islets. This result was also confirmed by dithizone staining analysis. Further evaluation of islet functionality was assessed by a glucose-stimulated insulin secretion test. The PA-encapsulated islets showed greater insulin secretion response to glucose stimulation than the bare islets with the differentiated U937 cells after 3 and 7 days. These results demonstrated that islet encapsulation with the PA nanomatrix gel was able to improve islet survival and function in the presence of inflammatory responses, which will increase the success rate of islet engraftment and the efficacy of islet transplantation.

Inhibition of Y1 receptor signaling improves islet transplant outcome

Failure to secrete sufficient quantities of insulin is a pathological feature of type-1 and type-2 diabetes, and also reduces the success of islet cell transplantation. Here we demonstrate that Y1 receptor signaling inhibits insulin release in β-cells, and show that this can be pharmacologically exploited to boost insulin secretion. Transplanting islets with Y1 receptor deficiency accelerates the normalization of hyperglycemia in chemically induced diabetic recipient mice, which can also be achieved by short-term pharmacological blockade of Y1 receptors in transplanted mouse and human islets. Furthermore, treatment of non-obese diabetic mice with a Y1 receptor antagonist delays the onset of diabetes. Mechanistically, Y1 receptor signaling inhibits the production of cAMP in islets, which via CREB mediated pathways results in the down-regulation of several key enzymes in glycolysis and ATP production. Thus, manipulating Y1 receptor signaling in β-cells offers a unique therapeutic opportunity for correcting insulin deficiency as it occurs in the pathological state of type-1 diabetes as well as during islet transplantation.Islet transplantation is considered one of the potential treatments for T1DM but limited islet survival and their impaired function pose limitations to this approach. Here Loh et al. show that the Y1 receptor is expressed in β- cells and inhibition of its signalling, both genetic and pharmacological, improves mouse and human islet function.

Development of glucose-responsive 'smart' insulin systems

PURPOSE OF REVIEW

The complexity of modern insulin-based therapy for type I and type II diabetes mellitus and the risks associated with excursions in blood-glucose concentration (hyperglycemia and hypoglycemia) have motivated the development of 'smart insulin' technologies (glucose-responsive insulin, GRI). Such analogs or delivery systems are entities that provide insulin activity proportional to the glycemic state of the patient without external monitoring by the patient or healthcare provider. The present review describes the relevant historical background to modern GRI technologies and highlights three distinct approaches: coupling of continuous glucose monitoring (CGM) to deliver devices (algorithm-based 'closed-loop' systems), glucose-responsive polymer encapsulation of insulin, and molecular modification of insulin itself.

RECENT FINDINGS

Recent advances in GRI research utilizing each of the three approaches are illustrated; these include newly developed algorithms for CGM-based insulin delivery systems, glucose-sensitive modifications of existing clinical analogs, newly developed hypoxia-sensitive polymer matrices, and polymer-encapsulated, stem-cell-derived pancreatic β cells.

SUMMARY

Although GRI technologies have yet to be perfected, the recent advances across several scientific disciplines that are described in this review have provided a path towards their clinical implementation.

Generation of Islet-Like Hormone-Producing Cells In Vitro from Adult Human Pancreas

Transplantation of pancreatic islets can provide long-lasting insulin independence for diabetic patients, but the current islet supply is limited. Here we describe a new in vitro system that utilizes adult human pancreatic islet-enriched fractions to generate hormone-producing cells over 3–4 weeks of culture. By labeling proliferating cells with a retrovirus-expressing green fluorescent protein, we show that in this system hormone-producing cells are generated de novo. These hormone-producing cells aggregate to form islet-like cell clusters. The cell clusters, when tested in vitro, release insulin in response to glucose and other secretagogues. After transplantation into immunodeficient, nondiabetic mice, the islet-like cell clusters survive and release human insulin. We propose that this system will be useful as an experimental tool for investigating mechanisms for generating new islet cells from the postnatal pancreas, and for designing strategies to generate physiologically competent pancreatic islet cells ex vivo.