Islet cell transplantation for the treatment of type 1 diabetes: recent advances and future challenges

Engineered tools to study endocrine dysfunction of pancreas

Pancreas, a vital organ with intricate endocrine and exocrine functions, is central to the regulation of the body's glucose levels and digestive processes. Disruptions in its endocrine functions, primarily regulated by islets of Langerhans, can lead to debilitating diseases such as diabetes mellitus. Murine models of pancreatic dysfunction have contributed significantly to the understanding of insulitis, islet-relevant immunological responses, and the optimization of cell therapies. However, genetic differences between mice and humans have severely limited their clinical translational relevance. Recent advancements in tissue engineering and microfabrication have ushered in a new era of in vitro models that offer a promising solution. This paper reviews the state-of-the-art engineered tools designed to study endocrine dysfunction of the pancreas. Islet on a chip devices that allow precise control of various culture conditions and noninvasive readouts of functional outcomes have led to the generation of physiomimetic niches for primary and stem cell derived islets. Live pancreatic slices are a new experimental tool that could more comprehensively recapitulate the complex cellular interplay between the endocrine and exocrine parts of the pancreas. Although a powerful tool, live pancreatic slices require more complex control over their culture parameters such as local oxygenation and continuous removal of digestive enzymes and cellular waste products for maintaining experimental functionality over long term. The combination of islet-immune and slice on chip strategies can guide the path toward the next generation of pancreatic tissue modeling for better understanding and treatment of endocrine pancreatic dysfunctions.

Unraveling the Enigma of Organismal Death: Insights, Implications, and Unexplored Frontiers

Significant knowledge gaps exist regarding the responses of cells, tissues, and organs to organismal death. Examining the survival mechanisms influenced by metabolism and environment, this research has the potential to transform regenerative medicine, redefine legal death, and provide insights into life's physiological limits, paralleling inquiries in embryogenesis.

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.

Targeted mapping and utilization of the perihepatic surface for therapeutic beta cell replacement and retrieval in diabetic non-human primates

Introduction

Successful diabetes reversal using pancreatic islet transplantation by various groups illustrates the significant achievements made in cell-based diabetes therapy. While clinically, intraportal islet delivery is almost exclusively used, it is not without obstacles, including instant blood-mediated inflammatory reaction (IBMIR), relative hypoxia, and loss of function over time, therefore hindering long-term success. Here we demonstrate the perihepatic surface of non-human primates (NHPs) as a potential islet delivery site maximizing favorable characteristics, including proximity to a dense vascular network for adequate oxygenation while avoiding IBMIR exposure, maintenance of portal insulin delivery, and relative ease of accessibility through minimally invasive surgery or percutaneous means. In addition, we demonstrate a targeted mapping technique of the perihepatic surface, allowing for the testing of multiple experimental conditions, including a semi-synthetic hydrogel as a possible three-dimensional framework to improve islet viability.

Methods

Perihepatic allo-islet cell transplants were performed in immunosuppressed cynomolgus macaques using a targeted mapping technique to test multiple conditions for biocompatibility. Transplant conditions included islets or carriers (including hydrogel, autologous plasma, and media) alone or in various combinations. Necropsy was performed at day 30, and histopathology was performed to assess biocompatibility, immune response, and islet viability. Subsequently, single-injection perihepatic allo-islet transplant was performed in immunosuppressed diabetic cynomolgus macaques. Metabolic assessments were measured frequently (i.e., blood glucose, insulin, C-peptide) until final graft retrieval for histopathology.

Results

Targeted mapping biocompatibility studies demonstrated mild inflammatory changes with islet-plasma constructs; however, significant inflammatory cell infiltration and fibrosis were seen surrounding sites with the hydrogel carrier affecting islet viability. In diabetic NHPs, perihepatic islet transplant using an autologous plasma carrier demonstrated prolonged function up to 6 months with improvements in blood glucose, exogenous insulin requirements, and HbA1c. Histopathology of these islets was associated with mild peri-islet mononuclear cell infiltration without evidence of rejection.

Discussion

The perihepatic surface serves as a viable site for islet cell transplantation demonstrating sustained islet function through 6 months. The targeted mapping approach allows for the testing of multiple conditions simultaneously to evaluate immune response to biomaterials at this site. Compared to traditional intraportal injection, the perihepatic site is a minimally invasive approach that allows the possibility for graft recovery and avoids IBMIR.

Transplantation of adipose derived stem cells in diabetes mellitus; limitations and achievements

Objectives

Diabetes mellitus (DM) is a complex metabolic disease that results from impaired insulin secreting pancreatic β-cells or insulin resistance. Although available medications help control the disease, patients suffer from its complications. Therefore, finding effective therapeutic approaches to treat DM is a priority. Adipose Derived Stem Cells (ADSCs) based therapy is a promising strategy in various regenerative medicine applications, but its systematic translational use is still somewhat out of reach. This review is aimed at clarifying achievements as well as challenges facing the application of ADSCs for the treatment of DM, with a special focus on the mechanisms involved.

Methods

Literature searches were carried out on "Scopus", "PubMed" and "Google Scholar" up to September 2022 to find relevant articles in the English language for the scope of this review.

Results

Recent evidence showed a significant role of ADSC therapies in DM by ameliorating insulin resistance and hyperglycemia, regulating hepatic glucose metabolism, promoting β cell function and regeneration, and functioning as a gene delivery tool. In addition, ADSCs could improve diabetic wound healing by promoting collagen deposition, inhibiting inflammation, and enhancing angiogenesis.

Conclusion

Overall, this literature review revealed the great clinical implications of ADSCs for translating into the clinical setting for the treatment of diabetes. However, further large-scale and controlled studies are needed to overcome challenges and confirm the safety and optimal therapeutic scheme before daily clinical application.

Supplementary Information

The online version contains supplementary material available at 10.1007/s40200-023-01280-8.

Subcutaneous device-free islet transplantation

Diabetes mellitus is a chronic metabolic disease, characterized by high blood sugar levels; it affects more than 500 million individuals worldwide. Type 1 diabetes mellitus (T1DM) is results from insufficient insulin secretion by islets; its treatment requires lifelong use of insulin injections, which leads to a large economic burden on patients. Islet transplantation may be a promising effective treatment for T1DM. Clinically, this process currently involves directly infusing islet cells into the hepatic portal vein; however, transplantation at this site often elicits immediate blood-mediated inflammatory and acute immune responses. Subcutaneous islet transplantation is an attractive alternative to islet transplantation because it is simpler, demonstrates lower surgical complication risks, and enables graft monitoring and removal. In this article, we review the current methods of subcutaneous device-free islet transplantation. Recent subcutaneous islet transplantation techniques with high success rate have involved the use of bioengineering technology and biomaterial cotransplantation-including cell and cell growth factor co-transplantation and hydrogel- or simulated extracellular matrix-wrapped subcutaneous co-transplantation. In general, current subcutaneous device-free islet transplantation modalities can simplify the surgical process and improve the posttransplantation graft survival rate, thus aiding effective T1DM management.

A new era of macrophage-based cell therapy

Macrophages are essential innate immune cells found throughout the body that have protective and pathogenic functions in many diseases. When activated, macrophages can mediate the phagocytosis of dangerous cells or materials and participate in effective tissue regeneration by providing growth factors and anti-inflammatory molecules. Ex vivo-generated macrophages have thus been used in clinical trials as cell-based therapies, and based on their intrinsic characteristics, they outperformed stem cells within specific target diseases. In addition to the old methods of generating naïve or M2 primed macrophages, the recently developed chimeric antigen receptor-macrophages revealed the potential of genetically engineered macrophages for cell therapy. Here, we review the current developmental status of macrophage-based cell therapy. The findings of important clinical and preclinical trials are updated, and patent status is investigated. Additionally, we discuss the limitations and future directions of macrophage-based cell therapy, which will help broaden the potential utility and clinical applications of macrophages.

Functionalized Collagen/Poly(ethylene glycol) Diacrylate Interpenetrating Network Hydrogel Enhances Beta Pancreatic Cell Sustenance

Three-dimensional matrices are a new strategy used to tackle type I diabetes, a chronic metabolic disease characterized by the destruction of beta pancreatic cells. Type I collagen is an abundant extracellular matrix (ECM), a component that has been used to support cell growth. However, pure collagen possesses some difficulties, including a low stiffness and strength and a high susceptibility to cell-mediated contraction. Therefore, we developed a collagen hydrogel with a poly (ethylene glycol) diacrylate (PEGDA) interpenetrating network (IPN), functionalized with vascular endothelial growth factor (VEGF) to mimic the pancreatic environment for the sustenance of beta pancreatic cells. We analyzed the physicochemical characteristics of the hydrogels and found that they were successfully synthesized. The mechanical behavior of the hydrogels improved with the addition of VEGF, and the swelling degree and the degradation were stable over time. In addition, it was found that 5 ng/mL VEGF-functionalized collagen/PEGDA IPN hydrogels sustained and enhanced the viability, proliferation, respiratory capacity, and functionality of beta pancreatic cells. Hence, this is a potential candidate for future preclinical evaluation, which may be favorable for diabetes treatment.

In Vitro and In Vivo Improvement of Islet Quality and Transplantation Successes following Islet Treatment with Biomaterials in Diabetic Rats

Background

Loss of islet survival and function, caused by native niche disruption and oxidative stress induction during mechanical and enzymatic isolation, limits the effectiveness of islet transplantation. Reconstitution of islet microenvironment, vascularization, and decreased oxidative stress with biomaterials may improve islet quality and graft outcomes. We investigated effects of two biomaterials, platelet-rich plasma and pancreatic islets homogenate combination on islet recovery and quality by evaluating in vitro islet survival, secretory function, and oxidative stress parameters and assessing in vivo transplantation outcomes.

Methods

In vitro, islet viability and secretory function of isolated islets were assessed after 24 h and 72 h incubation with biomaterials. Also, oxidative stress markers were measured once after isolation and 24 h after incubation with biomaterials. For evaluating in vivo effects, cultured islets for 24 h were transplanted into subscapular space of diabetic rat kidney, and outcomes were analyzed by measuring serum glucose and insulin concentrations, glucose tolerance test, level of oxidative parameters, and pancreatic gene expression.

Results

Treating islets with biomaterials significantly increased their viability and secretory function, reduced MDA level, and elevate SOD and CAT activity. Decreased level of glucose and MDA improved insulin level, increased SOD activity, and also enhanced pdx1 and insulin gene expression in diabetic rats after islet transplantation.

Conclusions

Biomaterials used in the present study should be consider as beneficial materials for increasing islet transplantation outcome. These materials may hamper transplantation limitation to some extent.

Harnessing Human Pluripotent Stem Cell-Derived Pancreatic In Vitro Models for High-Throughput Toxicity Testing and Diabetes Drug Discovery

The long-standing goals in diabetes research are to improve β-cell survival, functionality and increase β-cell mass. Current strategies to manage diabetes progression are still not ideal for sustained maintenance of normoglycemia, thereby increasing demand for the development of novel drugs. Available pancreatic cell lines, cadaveric islets, and their culture methods and formats, either 2D or 3D, allow for multiple avenues of experimental design to address diverse aims in the research setting. More specifically, these pancreatic cells have been employed in toxicity testing, diabetes drug screens, and with careful curation, can be optimized for use in efficient high-throughput screenings (HTS). This has since spearheaded the understanding of disease progression and related mechanisms, as well as the discovery of potential drug candidates which could be the cornerstone for diabetes treatment. This book chapter will touch on the pros and cons of the most widely used pancreatic cells, including the more recent human pluripotent stem cell-derived pancreatic cells, and HTS strategies (cell models, design, readouts) that can be used for the purpose of toxicity testing and diabetes drug discovery.

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.

Microwell culture platform maintains viability and mass of human pancreatic islets

Background

Transplantation of the human pancreatic islets is a promising approach for specific types of diabetes to improve glycemic control. Although effective, there are several issues that limit the clinical expansion of this treatment, including difficulty in maintaining the quality and quantity of isolated human islets prior to transplantation. During the culture, we frequently observe the multiple islets fusing together into large constructs, in which hypoxia-induced cell damage significantly reduces their viability and mass. In this study, we introduce the microwell platform optimized for the human islets to prevent unsolicited fusion, thus maintaining their viability and mass in long-term cultures.

Method

Human islets are heterogeneous in size; therefore, two different-sized microwells were prepared in a 35 mm-dish format: 140 µm × 300 µm-microwells for <160 µm-islets and 200 µm × 370 µm-microwells for >160 µm-islets. Human islets (2,000 islet equivalent) were filtered through a 160 µm-mesh to prepare two size categories for subsequent two week-cultures in each microwell dish. Conventional flat-bottomed 35 mm-dishes were used for non-filtered islets (2,000 islet equivalent/2 dishes). Post-cultured islets are collected to combine in each condition (microwells and flat) for the comparisons in viability, islet mass, morphology, function and metabolism. Islets from three donors were independently tested.

Results

The microwell platform prevented islet fusion during culture compared to conventional flat bottom dishes, which improved human islet viability and mass. Islet viability and mass on the microwells were well-maintained and comparable to those in pre-culture, while flat bottom dishes significantly reduced islet viability and mass in two weeks. Morphology assessed by histology, insulin-secreting function and metabolism by oxygen consumption did not exhibit the statistical significance among the three different conditions.

Conclusion

Microwell-bottomed dishes maintained viability and mass of human islets for two weeks, which is significantly improved when compared to the conventional flat-bottomed dishes.

Regenerative medicine technologies applied to transplant medicine. An update

Regenerative medicine (RM) is changing how we think and practice transplant medicine. In regenerative medicine, the aim is to develop and employ methods to regenerate, restore or replace damaged/diseased tissues or organs. Regenerative medicine investigates using tools such as novel technologies or techniques, extracellular vesicles, cell-based therapies, and tissue-engineered constructs to design effective patient-specific treatments. This review illustrates current advancements in regenerative medicine that may pertain to transplant medicine. We highlight progress made and various tools designed and employed specifically for each tissue or organ, such as the kidney, heart, liver, lung, vasculature, gastrointestinal tract, and pancreas. By combing both fields of transplant and regenerative medicine, we can harbor a successful collaboration that would be beneficial and efficacious for the repair and design of de novo engineered whole organs for transplantations.

In vitro generation of transplantable insulin-producing cells from canine adipose-derived mesenchymal stem cells

Canine mesenchymal stem cells (cMSCs) have potential applications for regenerative therapy, including the generation of insulin-producing cells (IPCs) for studying and treating diabetes. In this study, we established a useful protocol for generating IPCs from canine adipose mesenchymal stem cells (cAD-MSCs). Subsequently, in vitro preservation of pluronic F127-coated alginate (ALGPA)-encapsulated cAD-MSC-derived IPCs was performed to verify ready-to-use IPCs. IPCs were induced from cAD-MSCs with the modulated three-stepwise protocol. The first step of definitive endoderm (DE) induction showed that the cooperation of Chir99021 and Activin A created the effective production of Sox17-expressed DE cells. The second step for pancreatic endocrine (PE) progenitor induction from DE indicated that the treatment with taurine, retinoic acid, FGF2, EGF, TGFβ inhibitor, dorsomorphin, nicotinamide, and DAPT showed the significant upregulation of the pancreatic endocrine precursor markers Pdx1 and Ngn3. The last step of IPC production, the combination of taurine, nicotinamide, Glp-1, forskolin, PI3K inhibitor, and TGFβ inhibitor, yielded efficiently functional IPCs from PE precursors. Afterward, the maintenance of ALGPA-encapsulated cAD-MSC-derived IPCs with VSCBIC-1, a specialized medium, enhanced IPC properties. Conclusion, the modulated three-stepwise protocol generates the functional IPCs. Together, the encapsulation of cAD-MSC-derived IPCs and the cultivation with VSCBIC-1 enrich the maturation of generated IPCs.

Enhanced Differentiation Capacity and Transplantation Efficacy of Insulin-Producing Cell Clusters from Human iPSCs Using Permeable Nanofibrous Microwell-Arrayed Membrane for Diabetes Treatment

Although pancreatic islet transplantation is a potentially curative treatment for insulin-dependent diabetes, a shortage of donor sources, low differentiation capacity, and transplantation efficacy are major hurdles to overcome before becoming a standard therapy. Stem cell-derived insulin-producing cells (IPCs) are a potential approach to overcoming these limitations. To improve the differentiation capacity of the IPCs, cell cluster formation is crucial to mimic the 3D structure of the islet. This study developed a biodegradable polycaprolactone (PCL) electrospun nanofibrous (NF) microwell-arrayed membrane permeable to soluble factors. Based on the numerical analysis and experimental diffusion test, the NF microwell could provide sufficient nutrients, unlike an impermeable PDMS (polydimethylsiloxane) microwell. The IPC clusters in the NF microwells showed higher gene expression of insulin and PDX1 and insulin secretion than the PDMS microwells. The IPC clusters in the NF microwell-arrayed membrane could be directly transplanted. Transplanted IPC clusters in the microwells survived well and expressed PDX1 and insulin. Additionally, human c-peptide was identified in the blood plasma at two months after transplantation of the membranes. The NF microwell-arrayed membrane can be a new platform promoting IPC differentiation capacity and realizing an in situ transplantation technique for diabetic patients.

Mitogen Synergy: An Emerging Route to Boosting Human Beta Cell Proliferation

Decreased number and function of beta cells are a key aspect of diabetes mellitus (diabetes), a disease that remains an onerous global health problem. Means of restoring beta cell mass are urgently being sought as a potential cure for diabetes. Several strategies, such as de novo beta cell derivation via pluripotent stem cell differentiation or mature somatic cell transdifferentiation, have yielded promising results. Beta cell expansion is another promising strategy, rendered challenging by the very low proliferative capacity of beta cells. Many effective mitogens have been identified in rodents, but the vast majority do not have similar mitogenic effects in human beta cells. Extensive research has led to the identification of several human beta cell mitogens, but their efficacy and specificity remain insufficient. An approach based on the simultaneous application of several mitogens has recently emerged and can yield human beta cell proliferation rates of up to 8%. Here, we discuss recent advances in restoration of the beta cell population, focusing on mitogen synergy, and the contribution of RNA-sequencing (RNA-seq) to accelerating the elucidation of signaling pathways in proliferating beta cells and the discovery of novel mitogens. Together, these approaches have taken beta cell research up a level, bringing us closer to a cure for diabetes.

Discoveries in Pancreatic Physiology and Disease Biology Using Single-Cell RNA Sequencing

Transcriptome analysis is used to study gene expression in human tissues. It can promote the discovery of new therapeutic targets for related diseases by characterizing the endocrine function of pancreatic physiology and pathology, as well as the gene expression of pancreatic tumors. Compared to whole-tissue RNA sequencing, single-cell RNA sequencing (scRNA-seq) can detect transcriptional activity within a single cell. The scRNA-seq had an invaluable contribution to discovering previously unknown cell subtypes in normal and diseased pancreases, studying the functional role of rare islet cells, and studying various types of cells in diabetes as well as cancer. Here, we review the recent in vitro and in vivo advances in understanding the pancreatic physiology and pathology associated with single-cell sequencing technology, which may provide new insights into treatment strategy optimization for diabetes and pancreatic cancer.

Novel Functional Genes Involved in Transdifferentiation of Canine ADMSCs Into Insulin-Producing Cells, as Determined by Absolute Quantitative Transcriptome Sequencing Analysis

The transdifferentiation of adipose-derived mesenchymal stem cells (ADMSCs) into insulin-producing cells (IPCs) is a potential resource for the treatment of diabetes. However, the changes of genes and metabolic pathways on the transdifferentiation of ADMSCs into IPCs are largely unknown. In this study, the transdifferentiation of canine ADMSCs into IPCs was completed using five types of procedures. Absolute Quantitative Transcriptome Sequencing Analysis was performed at different stages of the optimal procedure. A total of 60,151 transcripts were obtained. Differentially expressed genes (DEGs) were divided into five groups: IPC1 vs. ADSC (1169 upregulated genes and 1377 downregulated genes), IPC2 vs. IPC1 (1323 upregulated genes and 803 downregulated genes), IPC3 vs. IPC2 (722 upregulated genes and 680 downregulated genes), IPC4 vs. IPC3 (539 upregulated genes and 1561 downregulated genes), and Beta_cell vs. IPC4 (2816 upregulated genes and 4571 downregulated genes). The gene ontology (GO) and Kyoto Encyclopedia of Genes and Genomes (KEGG) enrichment analysis of DEGs revealed that many genes and signaling pathways that are essential for transdifferentiation. Hnf1B, Dll1, Pbx1, Rfx3, and Foxa1 were screened out, and the functions of five genes were verified further by overexpression and silence. Foxa1, Pbx1, and Rfx3 exhibited significant effects, can be used as specific key regulatory factors in the transdifferentiation of ADMSCs into IPCs. This study provides a foundation for future work to understand the mechanisms of the transdifferentiation of ADMSCs into IPCs and acquire IPCs with high maturity.

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.

Withaferin A inhibits lymphocyte proliferation, dendritic cell maturation in vitro and prolongs islet allograft survival

The immunosuppressive regimen for clinical allogeneic islet transplantation uses beta cell–toxic compounds such as tacrolimus that cause islet graft loss. Previously we reported that the plant-derived steroidal lactone Withaferin A (WA) can protect islet grafts by inhibiting nuclear factor-kappa B (NF-κB). Since the NF-κB signaling pathway is essential for T-cell activation, we hypothesized that long-term WA administration may also provide an immunosuppressive effect. Treatment of BALB/c donor islets and C57BL/6N recipients with WA alone resulted in 80% islet graft long-term survival vs. 40% in low-dose FK506-treated mice. In vitro, WA significantly blocked mouse and human T-cell proliferation by CD3/CD28 bead stimulation and in mixed lymphocyte reaction assay. Treatment of immature dendritic cells with WA prevented their maturation in response to inflammatory stimuli, as seen by decreased expression of CD83 and human leukocyte antigen–DR isotype. Exosomes released by islets treated with WA contained significantly fewer proinflammatory molecules interleukin-6, interleukin-8, monocyte chemoattractant protein-1, interferon-gamma-induced protein-10, inducible nitric oxide synthase, and cyclooxygenase-2. In conclusion, WA treatment not only reduced inflammation but also prolonged allograft survival, possibly through suppression of dendritic cell maturation and T-cell proliferation. WA has the potential to inhibit both the innate and adaptive immune response to prolong allograft survival.

Therapeutic Advances in Diabetes, Autoimmune, and Neurological Diseases

Since 2015, 170 small molecules, 60 antibody-based entities, 12 peptides, and 15 gene- or cell-therapies have been approved by FDA for diverse disease indications. Recent advancement in medicine is facilitated by identification of new targets and mechanisms of actions, advancement in discovery and development platforms, and the emergence of novel technologies. Early disease detection, precision intervention, and personalized treatments have revolutionized patient care in the last decade. In this review, we provide a comprehensive overview of current and emerging therapeutic modalities developed in the recent years. We focus on nine diseases in three major therapeutics areas, diabetes, autoimmune, and neurological disorders. The pathogenesis of each disease at physiological and molecular levels is discussed and recently approved drugs as well as drugs in the clinic are presented.

Subcutaneous transplantation of engineered islet/adipose-derived mesenchymal stem cell sheets in diabetic pigs with total pancreatectomy

Introduction

Intraportal islet transplantation is a promising therapeutic approach for patients with type 1 diabetes mellitus (T1DM). However, despite being minimally invasive, the method has some limitations, such as short-term graft loss, portal venous thrombosis, and difficulty in collecting adequate amounts of islets. Subcutaneous islet transplantation on adipose-derived mesenchymal stem cell (ADSC) sheets has been suggested to overcome these limitations, and in this study, we have examined its feasibility in T1DM pigs.

Methods

Inguinal subcutaneous fat was harvested from young pigs and then isolated and cultured adequate ADSCs to prepare sheets. Islets were isolated from the pancreases of mature pigs and seeded on the ADSC sheets. T1DM pigs were generated by total pancreatectomy, and ADSC sheets with transplanted islets were administered subcutaneously to the waist (n = 2). The effects of the islets on the ADSC sheets and on blood glucose levels were evaluated. Insulin secretion was measured by insulin stimulation index.

Results

Islet viability was higher on ADSCs compared to islets alone (91.8 ± 4.3 vs. 81.7 ± 4.1%). The insulin stimulation index revealed higher glucose sensitivity of islets on ADSC sheets compared to islets alone (2.8 ± 2.0 vs. 0.8 ± 0.3). After transplantation, the blood glucose levels of two pigs were within the normal range, and sensitive insulin secretion was confirmed by intravenous glucose tolerance tests. After graftectomy, decreased insulin secretion and hyperglycemia were observed.

Conclusions

Subcutaneous islet transplantation using ADSC sheets can regulate the blood glucose levels of T1DM pigs.

•

The adipose-derived mesenchymal stem cell sheet is useful to protect the islets.

•

Subcutaneous islet transplantation on sheet normalized blood glucose in diabetic pig.

•

Subcutaneous islet transplantation on sheet can be a useful tool.

Improvement of the therapeutic capacity of insulin-producing cells trans-differentiated from human liver cells using engineered cell sheet

BACKGROUND

Although pancreatic islet transplantation therapy is ideal for diabetes patients, several hurdles have prevented it from becoming a standard treatment, including donor shortage and low engraftment efficacy. In this study, we prepared insulin-producing cells trans-differentiated from adult human liver cells as a new islet source. Also, cell sheet formation could improve differentiation efficiency and graft survival.

METHODS

Liver cells were expanded in vitro and trans-differentiated to IPCs using adenovirus vectors carrying human genes for PDX1, NEUROD1, and MAFA. IPCs were seeded on temperature-responsive culture dishes to form cell sheets. Differentiation efficiency was confirmed by ß cell-specific gene expression, insulin production, and immunohistochemistry. IPC suspension was injected by portal vein (PV), and IPC sheet was transplanted on the liver surface of the diabetic nude mouse. The therapeutic effect of IPC sheet was evaluated by comparing blood glucose control, weight gain, histological evaluation, and hepatotoxicity with IPC injection group. Also, cell biodistribution was assessed by in vivo/ex vivo fluorescence image tagging.

RESULTS

Insulin gene expression and protein production were significantly increased on IPC sheets compared with those in IPCs cultured on conventional culture dishes. Transplanted IPC sheets displayed significantly higher engraftment efficiency and fewer transplanted cells in other organs than injected IPCs, and also lower liver toxicity, improved blood glucose levels, and weight gain. Immunohistochemical analyses of liver tissue revealed positive staining for PDX1 and insulin at 1, 2, and 4 weeks after IPC transplantation.

CONCLUSIONS

In conclusion, cell sheet formation enhanced the differentiation function and maturation of IPCs in vitro. Additionally, parameters for clinical application such as distribution, therapeutic efficacy, and toxicity were favorable. The cell sheet technique may be used with IPCs derived from various cell sources in clinical applications.

Hypoxia-Preconditioned Wharton's Jelly-Derived Mesenchymal Stem Cells Mitigate Stress-Induced Apoptosis and Ameliorate Human Islet Survival and Function in Direct Contact Coculture System

Protection of isolated pancreatic islets against hypoxic and oxidative damage-induced apoptosis is essential during a pretransplantation culture period. A beneficial approach to maintain viable and functional islets is the coculture period with mesenchymal stem cells (MSCs). Hypoxia preconditioning of MSCs (Hpc-MSCs) for a short time stimulates the expression and secretion of antiapoptotic, antioxidant, and prosurvival factors. The aim of the present study was to evaluate the survival and function of human islets cocultured with Hpc-MSCs. Wharton's jelly-derived MSCs were subjected to hypoxia (5% O₂: Hpc) or normoxia (20% O₂: Nc) for 24 hours and then cocultured with isolated human islets in direct and indirect systems. Assays of viability and apoptosis, along with the production of reactive oxygen species (ROS), hypoxia-inducible factor 1-alpha (HIF-1α), apoptotic pathway markers, and vascular endothelial growth factor (VEGF) in the islets, were performed. Insulin and C-peptide secretions as islet function were also evaluated. Hpc-MSCs and Nc-MSCs significantly reduced the ROS production and HIF-1α protein aggregation, as well as downregulation of proapoptotic proteins and upregulation of antiapoptotic marker along with increment of VEGF secretion in the cocultured islet. However, the Hpc-MSCs groups were better than Nc-MSCs cocultured islets. Hpc-MSCs in both direct and indirect coculture systems improved the islet survival, while promotion of function was only significant in the direct cocultured cells. Hpc potentiated the cytoprotective and insulinotropic effects of MSCs on human islets through reducing stressful markers, inhibiting apoptosis pathway, enhancing prosurvival factors, and promoting insulin secretion, especially in direct coculture system, suggesting the effective strategy to ameliorate the islet quality for better transplantation outcomes.

Imaging Beta-Cell Function in the Pancreas of Non-Human Primates Using a Zinc-Sensitive MRI Contrast Agent

Non-invasive beta cell function measurements may provide valuable information for improving diabetes diagnostics and disease management as the integrity and function of pancreatic beta cells have been found to be compromised in Type-1 and Type-2 diabetes. Currently, available diabetes assays either lack functional information or spatial identification of beta cells. In this work, we introduce a method to assess the function of beta cells in the non-human primate pancreas non-invasively with MRI using a Gd-based zinc(II) sensor as a contrast agent, Gd-CP027. Additionally, we highlight the role of zinc(II) ions in the paracrine signaling of the endocrine pancreas via serological measurements of insulin and c-peptide. Non-human primates underwent MRI exams with simultaneous blood sampling during a Graded Glucose Infusion (GGI) with Gd-CP027 or with a non-zinc(II) sensitive contrast agent, gadofosveset. Contrast enhancement of the pancreas resulting from co-release of zinc(II) ion with insulin was observed focally when using the zinc(II)-specific agent, Gd-CP027, whereas little enhancement was detected when using gadofosveset. The contrast enhancement detected by Gd-CP027 increased in parallel with an increased dose of infused glucose. Serological measurements of C-peptide and insulin indicate that Gd-CP027, a high affinity zinc(II) contrast agent, potentiates their secretion only as a function of glucose stimulation. Taken in concert, this assay offers the possibility of detecting beta cell function in vivo non-invasively with MRI and underscores the role of zinc(II) in endocrine glucose metabolism.

Cryopreservation: An Overview of Principles and Cell-Specific Considerations

The origins of low-temperature tissue storage research date back to the late 1800s. Over half a century later, osmotic stress was revealed to be a main contributor to cell death during cryopreservation. Consequently, the addition of cryoprotective agents (CPAs) such as dimethyl sulfoxide (DMSO), glycerol (GLY), ethylene glycol (EG), or propylene glycol (PG), although toxic to cells at high concentrations, was identified as a necessary step to protect against rampant cell death during cryopreservation. In addition to osmotic stress, cooling and thawing rates were also shown to have significant influence on cell survival during low temperature storage. In general, successful low-temperature cell preservation consists of the addition of a CPA (commonly 10% DMSO), alone or in combination with additional permeating or non-permeating agents, cooling rates of approximately 1ºC/min, and storage in either liquid or vapor phase nitrogen. In addition to general considerations, cell-specific recommendations for hepatocytes, pancreatic islets, sperm, oocytes, and stem cells should be observed to maximize yields. For example, rapid cooling is associated with better cryopreservation outcomes for oocytes, pancreatic islets, and embryonic stem cells while slow cooling is recommended for cryopreservation of hepatocytes, hematopoietic stem cells, and mesenchymal stem cells. Yields can be further maximized by implementing additional pre-cryo steps such as: pre-incubation with glucose and anti-oxidants, alginate encapsulation, and selecting cells within an optimal age range and functional ability. Finally, viability and functional assays are critical steps in determining the quality of the cells post-thaw and improving the efficiency of the current cryopreservation methods.

Dose-dependent effects of necrostatin-1 supplementation to tissue culture media of young porcine islets

Previous studies have shown that necrostatin-1 (Nec-1) supplementation improved the viability of murine islets following exposure to nitric oxide, increased the survival of human islets during hypoxic culture, and augmented the maturation of pre-weaned porcine islets (PPIs) after 7 days of tissue culture. A limitation of these studies is that only one concentration of Nec-1 was used, and no studies have determined the optimal dose of Nec-1 for PPIs. Thus, the present study examined the effects of Nec-1 on PPIs at four different doses—0, 25, 50, 100, and 200 μM—after 7 days of tissue culture when supplemented on day 3. PPIs were isolated from pancreata of pre-weaned Yorkshire piglets (8–15 days old) and cultured in a specific islet maturation media added with Nec-1 on day 3 of tissue culture at 4 different doses—0, 25, 50, 100, and 200 μM (n = 6 for each dose). After 7 days of tissue culture, islets were assessed for recovery, viability, endocrine cellular content, GLUT2 expression in beta cells, and insulin secretion after glucose challenge. Nec-1 did not affect the viability of both intact islets and dissociated islets cells during tissue culture regardless of doses. Islets cultured in media supplemented with Nec-1 at 100 μM, but not 25, 50, or 200 μM, had a significantly higher recovery, composition of endocrine cells, GLUT2 expression in beta cells, and insulin secretion capacity than control islets cultured in media without Nec-1 supplementation. Moreover, culturing islets in 200 μM Nec-1 supplemented media not only failed to improve the insulin release but resulted in a lower glucose-induced insulin stimulation index compared to islets cultured in media added with 100 μM Nec-1. Xenotransplantation using porcine islets continues to demonstrate scientific advances to justify this area of research. Our findings indicate that Nec-1 supplementation at 100 μM was most effective to enhance the in vitro maturation of PPIs during tissue culture.

Review: Ischemia Reperfusion Injury-A Translational Perspective in Organ Transplantation

Thanks to the development of new, more potent and selective immunosuppressive drugs together with advances in surgical techniques, organ transplantation has emerged from an experimental surgery over fifty years ago to being the treatment of choice for many end-stage organ diseases, with over 139,000 organ transplants performed worldwide in 2019. Inherent to the transplantation procedure is the fact that the donor organ is subjected to blood flow cessation and ischemia during harvesting, which is followed by preservation and reperfusion of the organ once transplanted into the recipient. Consequently, ischemia/reperfusion induces a significant injury to the graft with activation of the immune response in the recipient and deleterious effect on the graft. The purpose of this review is to discuss and shed new light on the pathways involved in ischemia/reperfusion injury (IRI) that act at different stages during the donation process, surgery, and immediate post-transplant period. Here, we present strategies that combine various treatments targeted at different mechanistic pathways during several time points to prevent graft loss secondary to the inflammation caused by IRI.

Exosomes derived from human mesenchymal stem cells preserve mouse islet survival and insulin secretion function

Islet cell death and loss of function after isolation and before transplantation is considered a key barrier to successful islet transplantation outcomes. Mesenchymal stem cells (MSCs) have been used to protect isolated islets owing to their paracrine potential partially through the secretion of vascular endothelial growth factor (VEGF). The paracrine functions of MSCs are also mediated, at least in part, by the release of extracellular vesicles including exosomes. In the present study, we examined (i) the effect of exosomes from human MSCs on the survival and function of isolated mouse islets and (ii) whether exosomes contain VEGF and the potential impact of exosomal VEGF on the survival of mouse islets. Isolated mouse islets were cultured for three days with MSC-derived exosomes (MSC-Exo), MSCs, or MSC-conditioned media without exosomes (MSC-CM-without-Exo). We investigated the effects of the exosomes, MSCs, and conditioned media on islet viability, apoptosis and function. Besides the expression of apoptotic and pro-survival genes, the production of human and mouse VEGF proteins was evaluated. The MSCs and MSC-Exo, but not the MSC-CM-without-Exo, significantly decreased the percentage of apoptotic cells and increased islet viability following the downregulation of pro-apoptotic genes and the upregulation of pro-survival factors, as well as the promotion of insulin secretion. Human VEGF was observed in the isolated exosomes, and the gene expression and protein production of mouse VEGF significantly increased in islets cultured with MSC-Exo. MSC-derived exosomes are as efficient as parent MSCs for mitigating cell death and improving islet survival and function. This cytoprotective effect was probably mediated by VEGF transfer, suggesting a pivotal strategy for ameliorating islet transplantation outcomes.

Effects of platelet-rich plasma on the pancreatic islet survival and function, islet transplantation outcome and pancreatic pdx1 and insulin gene expression in streptozotocin-induced diabetic rats

Platelet-rich plasma (PRP) is a therapeutic option in different fields based on its growth factors. We investigated influence of PRP on islet survival, function, transplantation outcomes, and pancreatic genes expression in diabetic rats. In vitro: pancreatic isolated islets were incubated with/without PRP then viability, insulin secretion, and content were assessed. In vivo: Series 1 were designed to determine whether islet treatment with PRP improves transplantation outcome in diabetic rats by evaluating plasma glucose and insulin concentrations and oxidative parameters. Series 2, effects of PRP subcutaneous injection were evaluated on pancreatic genes expression and glucose tolerance test in diabetic rats. PRP enhanced viability and secretary function of islet. Reduced glucose and malondialdehyde levels as well as increased insulin levels, superoxide dismutase activity, and expressions of pdx1 and insulin were observed in diabetic rats. PRP treatment has positive effects on islet viability, function, transplantation outcome, and pancreatic genes expression in diabetic rats.

Microelectrode Array based Functional Testing of Pancreatic Islet Cells

Electrophysiological techniques to characterize the functionality of islets of Langerhans have been limited to short-term, one-time recordings such as a patch clamp recording. We describe the use of microelectrode arrays (MEAs) to better understand the electrophysiology of dissociated islet cells in response to glucose in a real-time, non-invasive method over prolonged culture periods. Human islets were dissociated into singular cells and seeded onto MEA, which were cultured for up to 7 days. Immunofluorescent imaging revealed that several cellular subtypes of islets; β, δ, and γ cells were present after dissociation. At days 1, 3, 5, and 7 of culture, MEA recordings captured higher electrical activities of islet cells under 16.7 mM glucose (high glucose) than 1.1 mM glucose (low glucose) conditions. The fraction of the plateau phase (FOPP), which is the fraction of time with spiking activity recorded using the MEA, consistently showed distinguishably greater percentages of spiking activity with high glucose compared to the low glucose for all culture days. In parallel, glucose stimulated insulin secretion was measured revealing a diminished insulin response after day 3 of culture. Additionally, MEA spiking profiles were similar to the time course of insulin response when glucose concentration is switched from 1.1 to 16.7 mM. Our analyses suggest that extracellular recordings of dissociated islet cells using MEA is an effective approach to rapidly assess islet functionality, and could supplement standard assays such as glucose stimulate insulin response.

Subcutaneous transplantation of bone marrow derived stem cells in macroencapsulation device for treating diabetic rats; clinically transplantable site

Background/aim

Diabetes mellitus (DM) is a serious, chronic and epidemic disease. Its effective therapy with exogenous insulin places an overwhelming burden on the patient's lifestyle. Moreover, pancreatic islet transplantation is limited by the scarceness of donors and the need for chronic immunosuppression. Cell-based therapy is considered an alternative source of insulin-producing cells (IPCs); encapsulating such cellular grafts in immunoisolating devices would protect the graft from immune attack without the need for immunosuppression. Herein, we investigate the ability of TheraCyte capsule as an immunoisolating device to promote the maturation of differentiated rat bone marrow derived mesenchymal stem cells (BM-MSCs), transplanted subcutaneously to treat diabetic rats in comparison with intratesticular transplantation.

Main methods

Rat BM-MSC were differentiated into IPCs, and either encapsulated in TheraCyte capsules for subcutaneous transplantation or transplanted intratesticular into diabetic rats. Serum insulin, C-peptide & blood glucose levels of transplanted animals were monitored. Retrieved cells were further characterized by immunofluorescence staining and gene expression analysis.

Key findings

Differentiated rat BM-MSC were able to produce insulin in vitro, ameliorate hyperglycemia in vivo and survive for 6 months post transplantation. Transplanted cells induced higher levels of insulin and C-peptide, lower levels of blood glucose in the cured animals of both experimental groups. Gene expression revealed a further in vivo maturation of the implanted cells.

Significance

These data suggest that TheraCyte encapsulation of allogeneic differentiated stem cells are capable of reversing hyperglycemia, which holds a great promise as a new cell based, clinically applicable therapies for diabetes.

Small Molecule-Induced Pancreatic β-Like Cell Development: Mechanistic Approaches and Available Strategies

Diabetes is a metabolic disease which affects not only glucose metabolism but also lipid and protein metabolism. It encompasses two major types: type 1 and 2 diabetes. Despite the different etiologies of type 1 and 2 diabetes mellitus (T1DM and T2DM, respectively), the defining features of the two forms are insulin deficiency and resistance, respectively. Stem cell therapy is an efficient method for the treatment of diabetes, which can be achieved by differentiating pancreatic β-like cells. The consistent generation of glucose-responsive insulin releasing cells remains challenging. In this review article, we present basic concepts of pancreatic organogenesis, which intermittently provides a basis for engineering differentiation procedures, mainly based on the use of small molecules. Small molecules are more auspicious than any other growth factors, as they have unique, valuable properties like cell-permeability, as well as a nonimmunogenic nature; furthermore, they offer immense benefits in terms of generating efficient functional beta-like cells. We also summarize advances in the generation of stem cell-derived pancreatic cell lineages, especially endocrine β-like cells or islet organoids. The successful induction of stem cells depends on the quantity and quality of available stem cells and the efficient use of small molecules.

Antidiabetic Properties of Curcumin I: Evidence from In Vitro Studies

Type 2 diabetes mellitus (T2DM) is a growing metabolic disease characterized by insulin resistance and hyperglycemia. Current preventative and treatment strategies for T2DM and insulin resistance lack in efficacy resulting in the need for new approaches to prevent and manage/treat the disease better. In recent years, epidemiological studies have suggested that diets rich in fruits and vegetables have beneficial health effects including protection against insulin resistance and T2DM. Curcumin, a polyphenol found in turmeric, and curcuminoids have been reported to have antioxidant, anti-inflammatory, hepatoprotective, nephroprotective, neuroprotective, immunomodulatory and antidiabetic properties. The current review (I of II) summarizes the existing in vitro studies examining the antidiabetic effects of curcumin, while a second (II of II) review summarizes evidence from existing in vivo animal studies and clinical trials focusing on curcumin’s antidiabetic properties.

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.

Using a barcoded AAV capsid library to select for clinically relevant gene therapy vectors

While gene transfer using recombinant adeno-associated viral (rAAV) vectors has shown success in some clinical trials, there remain many tissues that are not well transduced. Because of the recent success in reprogramming islet-derived cells into functional β cells in animal models, we constructed 2 highly complex barcoded replication competent capsid shuffled libraries and selected for high-transducing variants on primary human islets. We describe the generation of a chimeric AAV capsid (AAV-KP1) that facilitates transduction of primary human islet cells and human embryonic stem cell-derived β cells with up to 10-fold higher efficiency compared with previously studied best-in-class AAV vectors. Remarkably, this chimeric capsid also enabled transduction of both mouse and human hepatocytes at very high levels in a humanized chimeric mouse model, thus providing a versatile vector that has the potential to be used in both preclinical testing and human clinical trials for liver-based diseases and diabetes.

Establishment of a diabetes mellitus type 1 model in the common marmoset

Common marmosets have attracted considerable attention as a small standard primate model in biomedical research. However, no marmoset diabetes model is available. Here, we established a marmoset diabetes model via the combination of partial pancreatectomy and intravenous streptozotocin (STZ). A partial pancreatectomy was performed in 11 common marmosets and multiple STZ doses were intravenously administered. Diabetes was diagnosed upon sustained hyperglycaemia (nonfasting blood glucose level >200 mg/dl). Blood glucose and biochemistry were periodically assessed, in addition to glucose tolerance testing, continual blood glucose determination using a continuous glucose monitoring system, urine testing and histological evaluation. In 8 of the 11 animals (73%), diabetes mellitus was induced. The diabetic marmosets also showed abnormal intravenous and oral glucose tolerance test results. Blood glucose levels decreased in response to human insulin administration. The hyperglycaemic state was irreversible and persisted for more than 3 months, and the animals’ condition was manageable via daily insulin administration. Thus, diabetes can be successfully induced and maintained in the common marmoset via partial pancreatectomy and STZ administration. This protocol effectively generates a valuable animal model for studying disease pathogenesis, risk factors and therapeutic interventions, including islet transplantation.

Protective effect of nobiletin on isolated human islets survival and function against hypoxia and oxidative stress-induced apoptosis

Islets transplantation, as a treatment of type 1 diabetes, faces challenges, including the loss of islets in the process of isolation and pre-transplantation due to cellular stresses-induced apoptosis. Accordingly, the optimization of culture plays a decisive role in the transplantation success. In this study, we evaluated the effect of nobiletin on the cultured human islets. Isolated human islets were treated by different concentrations of nobiletin and cultured for 24 and 72 hours. Then, the islets viability, apoptosis, insulin and C-peptide secretion, and apoptosis markers were evaluated. Also, the production of reactive oxygen species (ROS), hypoxia inducible factor 1 alpha (HIF-1α), and its target genes in the islets were examined. Our findings showed that the islets were encountered with hypoxia and oxidative stress after isolation and during culture. These insults induced apoptosis and reduced viability during culture period. Moreover, the secretion of insulin and C-peptide decreased. Nobiletin treatments significantly improved the islets survival through reduction of HIF-1α and ROS production and suppression of apoptosis, along with increased islets function. Islet protective effect of nobiletin might be related to its anti-oxidant, anti-apoptotic and insulinotropic properties. Hence, in order to achieve viable and functional islets for clinical transplantation, the application of nobiletin during pre-transplantation period is useful.

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.

Clathrin-mediated Endocytosis of Alpha-1 Antitrypsin is Essential for its Protective Function in Islet Cell Survival

Cytokine-induced pancreatic β cell death plays a pivotal role in both type 1 and type 2 diabetes. Our previous study showed that alpha-1 antitrypsin (AAT) inhibits β cell death through the suppression of cytokine-induced c-Jun N-terminal kinase (JNK) activation in an islet transplantation model. The aim of this study was to further understand how AAT impacts β cells by studying AAT endocytosis in human islets and a βTC3 murine insulinoma cell line.

Methods: In vitro, human islets and βTC3 cells were stimulated with cytokines in the presence or absence of chlorpromazine (CPZ), a drug that disrupts clathrin-mediated endocytosis. Western blot, real-time PCR and cell death ELISA were performed to investigate β cell death. The oxygen consumption rate (OCR) was measured on human islets. In vivo, islets were harvested from C57BL/6 donor mice treated with saline or human AAT and transplanted into the livers of syngeneic mice that had been rendered diabetic by streptozotocin (STZ). Islet graft survival and function were analyzed.

Results: AAT was internalized by β cells in a time- and dose-dependent manner. AAT internalization was mediated by clathrin as treatment with CPZ, profoundly decreased AAT internalization, cytokine-induced JNK activation and the downstream upregulation of c-Jun mRNA expression. Similarly, addition of CPZ attenuated cytokine-induced caspase 9 cleavage (c-casp 9) and DNA fragmentation, which was suppressed by AAT. Treatment of donor mice with AAT produced AAT internalization in islets, and resulted in a higher percentage of recipients reaching normoglycemia after syngeneic intraportal islet transplantation.

Conclusion: Our results suggest that AAT is internalized by β cells through clathrin-mediated endocytosis that leads to the suppression of caspase 9 activation. This process is required for the protective function of AAT in islets when challenged with proinflammatory cytokines or after islet transplantation.

Synthetic poly(ethylene glycol)-based microfluidic islet encapsulation reduces graft volume for delivery to highly vascularized and retrievable transplant site

Transplant of hydrogel-encapsulated allogeneic islets has been explored to reduce or eliminate the need for chronic systemic immunosuppression by creating a physical barrier that prevents direct antigen presentation. Although successful in rodents, translation of alginate microencapsulation to large animals and humans has been hindered by large capsule sizes (≥500 μm diameter) that result in suboptimal nutrient diffusion in the intraperitoneal space. We developed a microfluidic encapsulation system that generates synthetic poly(ethylene glycol)-based microgels with smaller diameters (310 ± 14 μm) that improve encapsulated islet insulin responsiveness over alginate capsules and allow transplant within vascularized tissue spaces, thereby reducing islet mass requirements and graft volumes. By delivering poly(ethylene glycol)-encapsulated islets to an isolated, retrievable, and highly vascularized site via a vasculogenic delivery vehicle, we demonstrate that a single pancreatic donor syngeneic islet mass exhibits improved long-term function over conventional alginate capsules and close integration with transplant site vasculature. In vivo tracking of bioluminescent allogeneic encapsulated islets in an autoimmune type 1 diabetes murine model showed enhanced cell survival over unencapsulated islets in the absence of chronic systemic immunosuppression. This method demonstrates a translatable alternative to intraperitoneal encapsulated islet transplant.

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

Background

Islet transplantation has progressively become a safe alternative to pancreas transplantation for the treatment of type 1 diabetes. However, the long-term results of islet transplantation could be significantly increased by improving the quality of the islet isolation technique even exploring alternative islet transplantation sites to reduce the number of islets required to mitigate hyperglycemia. The goal of the study was to test the lymph node as a suitable anatomical location for islet engraftment in a rodent model.

Methods

Forty Lewis rats, 6–8 weeks old, body weight 250–300 g, have been used as islet donors and recipients in syngeneic islet transplantation experiments. Ten rats were rendered diabetic by one injection of 65 mg/Kg of streptozotocin. After pancreas retrieval from non diabetic donors, islet were isolated and transplanted in the mesenteric lymph nodes of 7 diabetic rats. Rats were followed for 30 days after islet transplantation.

Results

A total of 7 islet transplantations in mesenteric lymph nodes have been performed. Two rats died 24 and 36 h after transplantation due to complications. No transplanted rat acquired normal glucose blood levels and insulin independence after the transplantation. However, the mean blood levels of glycemia were significantly lower in transplanted rats compared with diabetic rats (470.4 mg/dl vs 605 mg/dl, p 0.04). Interestingly, transplanted rats have a significant weight increase after transplantation compared to diabetic rats (mean value 295 g in transplanted rats vs 245 g in diabetic rats, p < 0.05), with an overall improvement of social activities and health. Immunohistochemical analysis of the 5 mesenteric lymph nodes of transplanted rats demonstrated the presence of living islets in one lymph node.

Conclusions

Although islet engraftment in lymph nodes is possible, islet transplantation in lymph nodes in rats resulted in few improvements of glucose parameters.

Evaluation of [68Ga]DO3A-VS-Cys40-Exendin-4 as a PET Probe for Imaging Human Transplanted Islets in the Liver

[⁶⁸Ga]DO3A-VS-Cys⁴⁰-Exendin-4, a glucagon-like peptide 1 receptor agonist, was evaluated as a potential PET tracer for the quantitation of human islets transplanted to the liver. The short-lived PET radionuclide ⁶⁸Ga, available on a regular basis from a ⁶⁸Ge/⁶⁸Ga generator, is an attractive choice. Human C-peptide was measured to evaluate human islet function post-transplantation and prior to microPET imaging. [⁶⁸Ga]DO3A-VS-Cys⁴⁰-Exendin-4 was radiosynthesized and evaluated for PET imaging of transplanted human islets in the liver of healthy NOD/SCID mice. The biodistribution of the tracer was evaluated to determine the uptake into various organs, and qPCR of liver samples was conducted to confirm engrafted islet numbers after PET imaging. Measurement of human C-peptide indicated that higher engrafted islet mass resulted in higher human C-peptide levels in post-transplantation. The microPET imaging yielded high resolution images of liver-engrafted islets and also showed significant retention in mouse livers at 8 weeks post-transplantation. Biodistribution studies in mice revealed that liver uptake of [⁶⁸Ga]DO3A-VS-Cys⁴⁰-Exendin-4 was approximately 6-fold higher in mice that received 1000 islet equivalent (IEQ) than in non-transplanted mice. qPCR analysis of insulin expression suggested that islet engraftment numbers were close to 1000 IEQ transplanted. In conclusion, human islets transplanted into the livers of mice exhibited significant uptake of [⁶⁸Ga]DO3A-VS-Cys⁴⁰-Exendin-4 compared to the livers of untreated mice; and imaging of the mice using PET showed the human islets clearly with high contrast against liver tissue, enabling accurate quantitation of islet mass. Further validation of [⁶⁸Ga]DO3A-VS-Cys⁴⁰-Exendin-4 as an islet imaging probe for future clinical application is ongoing.

Antidiabetic Effects of a Short Peptide of Potato Protein Hydrolysate in STZ-Induced Diabetic Mice

Alcalase- generated potato protein hydrolysate (APPH) is a potential bioactive peptide against diabetes mellitus (DM) and DM-associated secondary effects in animal models. The aim of the present study was to find the efficiency of a deca-peptide DIKTNKPVIF (DF) from APPH against DM. Six-week-old male ICR mice were divided into the following groups: Control, Control+DF (received 50 mg/kg DF), streptozotocin (STZ)-induced DM group, DM+Acarbose group (20 mg/kg of acarbose), DM+DF-L (25 mg/kg of DF), DM+DF-H (50 mg/kg of DF), and DM+APPH (50 mg/kg of APPH). Comparable to APPH, treatment with DF effectively regulated blood glucose level and also controlled plasma total glycerol (TG), total cholesterol (TC), insulin, and HbA1c levels in DM animals. DF treatment also showed evidence of ameliorating DM-associated damages in the pancreatic islets and in the liver, heart, and kidney tissues. Therefore, the results demonstrate that the short synthetic peptide-DF may effectively provide protection against DM-associated damages.

Characterization of Polyethylene Glycol-Reinforced Alginate Microcapsules for Mechanically Stable Cell Immunoisolation

Islet transplantation within mechanically stable microcapsules offers the promise of long-term diabetes reversal without chronic immunosuppression. Reinforcing the ionically gelled network of alginate (ALG) hydrogels with covalently linked polyethylene glycol (PEG) may create hybrid structures with desirable mechanical properties. This report describes the fabrication of hybrid PEG-ALG interpenetrating polymer networks and the investigation of microcapsule swelling, surface modulus, rheology, compression, and permeability. It is demonstrated that hybrid networks are more resistant to bulk swelling and compressive deformation and display improved shape recovery and long-term resilience. Interestingly, it is shown that PEG-ALG networks behave like ALG during microscale surface deformation and small amplitude shear while exhibiting similar permeability properties. The results from this report's in vitro characterization are interpreted according to viscoelastic polymer theory and provide new insight into hybrid hydrogel mechanical behavior. This new understanding of PEG-ALG mechanical performance is then linked to previous work that demonstrated the success of hybrid polymer immunoisolation devices in vivo.

Adipose tissue-derived mesenchymal stem cells rescue the function of islets transplanted in sub-therapeutic numbers via their angiogenic properties

A significant proportion of islets are lost following transplantation due to hypoxia and inflammation. We hypothesize that adipose tissue-derived mesenchymal stem cells (AD-MSCs) can rescue a sub-therapeutic number of transplanted islets by helping them establish a new blood supply and reducing inflammation. Diabetic mice received syngeneic transplantation with 75 (minimal), 150 (sub-therapeutic), or 225 (therapeutic) islets, with or without 1 × 10⁶ mouse AD-MSCs. Fasting blood glucose (FBG) values were measured over 6 weeks with tissue samples collected for islet structure and morphology (H&E, insulin/glucagon staining). Histological and immunohistochemical analyses of islets were also performed at 2 weeks in animals transplanted with a sub-therapeutic number of islets, with and without AD-MSCs, to determine new blood vessel formation, the presence of pro-angiogenic factors facilitating revascularization, and the degree of inflammation. AD-MSCs had no beneficial effect on FBG values when co-transplanted with a minimal or therapeutic number of islets. However, AD-MSCs significantly reduced FBG values and restored glycemic control in diabetic animals transplanted with a sub-therapeutic number of islets. Islets co-transplanted with AD-MSCs preserved their native morphology and organization and exhibited less aggregation when compared to islets transplanted alone. In the sub-therapeutic group, AD-MSCs significantly increased islet revascularization and the expression of angiogenic factors including hepatocyte growth factor (HGF) and angiopoietin-1 (Ang-1) while also reducing inflammation. AD-MSCs can rescue the function of islets when transplanted in a sub-therapeutic number, for at least 6 weeks, via their ability to maintain islet architecture while concurrently facilitating islet revascularization and reducing inflammation.

Generation of Human Stem Cell-Derived Pancreatic Organoids (POs) for Regenerative Medicine

Insulin-dependent diabetes mellitus or type 1 diabetes mellitus (T1DM) is an auto-immune condition characterized by the loss of pancreatic β-cells. The curative approach for highly selected patients is the pancreas or the pancreatic islet transplantation. Nevertheless, these options are limited by a growing shortage of donor organs and by the requirement of immunosuppression.Xenotransplantation of porcine islets has been extensively investigated. Nevertheless, the strong xenoimmunity and the risk of transmission of porcine endogenous retroviruses, have limited their application in clinic. Generation of β-like cells from stem cells is one of the most promising strategies in regenerative medicine. Embryonic, and more recently, adult stem cells are currently the most promising cell sources exploited to generate functional β-cells in vitro. A number of studies demonstrated that stem cells could generate functional pancreatic organoids (POs), able to restore normoglycemia when implanted in different preclinical diabetic models. Nevertheless, a gradual loss of function and cell dead are commonly detected when POs are transplanted in immunocompetent animals. So far, the main issue to be solved is the post-transplanted islet loss, due to the host immune attack. To avoid this hurdle, nanotechnology has provided a number of polymers currently under investigation for islet micro and macro-encapsulation. These new approaches, besides conferring PO immune protection, are able to supply oxygen and nutrients and to preserve PO morphology and long-term viability.Herein, we summarize the current knowledge on bioengineered POs and the stem cell differentiation platforms. We also discuss the in vitro strategies used to generate functional POs, and the protocols currently used to confer immune-protection against the host immune attack (micro- and macro-encapsulation). In addition, the most relevant ongoing clinical trials, and the most relevant hurdles met to move towards clinical application are revised.

Concise Review: Lessons Learned from Islet Transplant Clinical Trials in Developing Stem Cell Therapies for Type 1 Diabetes

We examined data and patterns in clinical islet transplant studies registered on ClinicalTrials.gov (CTgov) for treatment of type 1 diabetes (T1D), with a goal of extracting insights to apply in the design of a pluripotent stem cell‐derived islet therapy. Clinical islet transplantation, as a cell therapy (rather than solid organ transplant) is a unique precedent for stem cell‐based islet therapies. Registration activity shows that the field is not growing significantly, and newer registrations suggest that the reasons for stagnation include need for a more optimal site of infusion/transplantation, and especially a need for better immune protective strategies to advance a more effective and durable therapy for T1D. stem cells translational medicine2019;8:209&214