β-Cell Replacement in Mice Using Human Type 1 Diabetes Nuclear Transfer Embryonic Stem Cells

Glucose Transporters Are Key Components of the Human Glucostat

Mouse models are extensively used in metabolic studies. However, inherent differences between the species, notably their blood glucose levels, hampered data translation into clinical settings. In this study, we confirmed GLUT1 to be the predominantly expressed glucose transporter in both adult and fetal human β-cells. In comparison, GLUT2 is detected in a small yet significant subpopulation of adult β-cells and is expressed to a greater extent in fetal β-cells. Notably, GLUT1/2 expression in INS+ cells from human stem cell-derived islet-like clusters (SC-islets) exhibited a closer resemblance to that observed in fetal islets. Transplantation of primary human islets or SC-islets, but not murine islets, lowered murine blood glucose to the human glycemic range, emphasizing the critical role of β-cells in establishing species-specific glycemia. We further demonstrate the functional requirements of GLUT1 and GLUT2 in glucose uptake and insulin secretion through chemically inhibiting GLUT1 in primary islets and SC-islets and genetically disrupting GLUT2 in SC-islets. Finally, we developed a mathematical model to predict changes in glucose uptake and insulin secretion as a function of GLUT1/2 expression. Collectively, our findings illustrate the crucial roles of GLUTs in human β-cells, and identify them as key components in establishing species-specific glycemic set points.

ARTICLE HIGHLIGHTS

The efficiency of stem cell differentiation into functional beta cells for treating insulin-requiring diabetes: Recent advances and current challenges

In recent years, the potential of stem cells (SCs) to differentiate into various types of cells, including β-cells, has led to a significant boost in development. The efficiency of this differentiation process and the functionality of the cells post-transplantation are crucial factors for the success of stem cell therapy in diabetes. Herein, this article reviews the current advances and challenges faced by stem cell differentiation into functional β-cells for diabetes treatment. In vitro, researchers have sought to enhance the differentiation efficiency of functional β-cells by mimicking the normal pancreatic development process, using gene manipulation, pharmacological and culture conditions stimulation, three-dimensional (3D) and organoid culture, or sorting for functional β-cells based on mature islet cell markers. Furthermore, in vivo studies have also looked at suitable transplantation sites, the enhancement of the transplantation microenvironment, immune modulation, and vascular function reconstruction to improve the survival rate of functional β-cells, thereby enhancing the treatment of diabetes. Despite these advancements, developing stem cells to produce functional β-cells for efficacious diabetes treatment is a continuous research endeavor requiring significant multidisciplinary collaboration, for the stem-cell-derived beta cells to evolve into an effective cellular therapy.

Treatment of Donor Cells with Oxidative Phosphorylation Inhibitor CPI Enhances Porcine Cloned Embryo Development

Somatic cell nuclear transfer (SCNT) technology holds great promise for livestock industry, life science and human biomedicine. However, the development and application of this technology is limited by the low developmental potential of SCNT embryos. The developmental competence of cloned embryos is influenced by the energy metabolic status of donor cells. The purpose of this study was to investigate the effects of CPI, an oxidative phosphorylation inhibitor, on the energy metabolism pathways of pig fibroblasts and the development of subsequent SCNT embryos. The results showed that treatment of porcine fibroblasts with CPI changed the cellular energy metabolic pathways from oxidative phosphorylation to glycolysis and enhanced the developmental ability of subsequent SCNT embryos. The present study establishes a simple, new way to improve pig cloning efficiency, helping to promote the development and application of pig SCNT technology.

Preservation of β-Cells as a Therapeutic Strategy for Diabetes

The preservation of pancreatic islet β-cells is crucial in diabetes mellitus, encompassing both type 1 and type 2 diabetes. β-cell dysfunction, reduced mass, and apoptosis are central to insufficient insulin secretion in both types. Research is focused on understanding β-cell characteristics and the factors regulating their function to develop novel therapeutic approaches. In type 1 diabetes (T1D), β-cell destruction by the immune system calls for exploring immunosuppressive therapies, non-steroidal anti-inflammatory drugs, and leukotriene antagonists. Islet transplantation, stem cell therapy, and xenogeneic transplantation offer promising strategies for type 1 diabetes treatment. For type 2 diabetes (T2D), lifestyle changes like weight loss and exercise enhance insulin sensitivity and maintain β-cell function. Additionally, various pharmacological approaches, such as cytokine inhibitors and protein kinase inhibitors, are being investigated to protect β-cells from inflammation and glucotoxicity. Bariatric surgery emerges as an effective treatment for obesity and T2D by promoting β-cell survival and function. It improves insulin sensitivity, modulates gut hormones, and expands β-cell mass, leading to diabetes remission and better glycemic control. In conclusion, preserving β-cells offers a promising approach to managing both types of diabetes. By combining lifestyle modifications, targeted pharmacological interventions, and advanced therapies like stem cell transplantation and bariatric surgery, we have a significant chance to preserve β-cell function and enhance glucose regulation in diabetic patients.

Bioengineering and vascularization strategies for islet organoids: advancing toward diabetes therapy

Diabetes presents a pressing healthcare crisis, necessitating innovative solutions. Organoid technologies have rapidly advanced, leading to the emergence of bioengineering islet organoids as an unlimited source of insulin-producing cells for treating insulin-dependent diabetes. This advancement surpasses the need for cadaveric islet transplantation. However, clinical translation of this approach faces two major limitations: immature endocrine function and the absence of a perfusable vasculature compared to primary human islets. In this review, we summarize the latest developments in bioengineering functional islet organoids in vitro and promoting vascularization of organoid grafts before and after transplantation. We highlight the crucial roles of the vasculature in ensuring long-term survival, maturation, and functionality of islet organoids. Additionally, we discuss key considerations that must be addressed before clinical translation of islet organoid-based therapy, including functional immaturity, undesired heterogeneity, and potential tumorigenic risks.

Permanent neonatal diabetes-causing insulin mutations have dominant negative effects on beta cell identity

OBJECTIVE

Heterozygous coding sequence mutations of the INS gene are a cause of permanent neonatal diabetes (PNDM), requiring insulin therapy similar to T1D. While the negative effects on insulin processing and secretion are known, how dominant insulin mutations result in a continued decline of beta cell function after birth is not well understood.

METHODS

We explored the causes of beta cell failure in two PNDM patients with two distinct INS mutations using patient-derived iPSCs and mutated hESCs.

RESULTS

we detected accumulation of misfolded proinsulin and impaired proinsulin processing in vitro, and a dominant-negative effect of these mutations on beta-cell mass and function after transplantation into mice. In addition to anticipated ER stress, we found evidence of beta-cell dedifferentiation, characterized by an increase of cells expressing both Nkx6.1 and ALDH1A3, but negative for insulin and glucagon.

CONCLUSIONS

These results highlight a novel mechanism, the loss of beta cell identity, contributing to the loss and functional failure of human beta cells with specific insulin gene mutations.

Urine-derived stem cell therapy for diabetes mellitus and its complications: progress and challenges

Diabetes mellitus (DM) is a chronic and relentlessly progressive metabolic disease characterized by a relative or absolute deficiency of insulin in the body, leading to increased production of advanced glycosylation end products that further enhance oxidative and nitrosative stresses, often leading to multiple macrovascular (cardiovascular disease) and microvascular (e.g., diabetic nephropathy, diabetic retinopathy, and neuropathy) complications, representing the ninth leading cause of death worldwide. Existing medical treatments do not provide a complete cure for DM; thus, stem cell transplantation therapy has become the focus of research on DM and its complications. Urine-derived stem cells (USCs), which are isolated from fresh urine and have biological properties similar to those of mesenchymal stem cells (MSCs), were demonstrated to exert antiapoptotic, antifibrotic, anti-inflammatory, and proangiogenic effects through direct differentiation or paracrine mechanisms and potentially treat patients with DM. USCs also have the advantages of simple noninvasive sample collection procedures, minimal ethical issues, low cost, and easy cell isolation methods and thus have received more attention in regenerative therapies in recent years. This review outlines the biological properties of USCs and the research progress and current limitations of their role in DM and related complications. In summary, USCs have shown good versatility in treating hyperglycemia-impaired target organs in preclinical models, and many challenges remain in translating USC therapies to the clinic.

Incomplete reprogramming of DNA replication timing in induced pluripotent stem cells

Induced pluripotent stem cells (iPSCs) are the foundation of cell therapy. Differences in gene expression, DNA methylation, and chromatin conformation, which could affect differentiation capacity, have been identified between iPSCs and embryonic stem cells (ESCs). Less is known about whether DNA replication timing, a process linked to both genome regulation and genome stability, is efficiently reprogrammed to the embryonic state. To answer this, we compare genome-wide replication timing between ESCs, iPSCs, and cells reprogrammed by somatic cell nuclear transfer (NT-ESCs). While NT-ESCs replicate their DNA in a manner indistinguishable from ESCs, a subset of iPSCs exhibits delayed replication at heterochromatic regions containing genes downregulated in iPSCs with incompletely reprogrammed DNA methylation. DNA replication delays are not the result of gene expression or DNA methylation aberrations and persist after cells differentiate to neuronal precursors. Thus, DNA replication timing can be resistant to reprogramming and influence the quality of iPSCs.

Scalable Generation of 3D Pancreatic Islet Organoids from Human Pluripotent Stem Cells in Suspension Bioreactors

We describe a scalable method for the robust generation of 3D pancreatic islet-like organoids from human pluripotent stem cells using suspension bioreactors. Our protocol involves a 6-stage, 20-day directed differentiation process, resulting in the production of 104-105 organoids. These organoids comprise α- and β-like cells that exhibit glucose-responsive insulin and glucagon secretion. We detail methods for culturing, passaging, and cryopreserving stem cells as suspended clusters and for differentiating them through specific growth media and exogenous factors added in a stepwise manner. Additionally, we address quality control measures, troubleshooting strategies, and functional assays for research applications.

Scalable generation of 3D pancreatic islet organoids from human pluripotent stem cells in suspension bioreactors

Here, we present a protocol for producing 3D pancreatic-like organoids from human pluripotent stem cells in suspension bioreactors. We describe scalable techniques for generating 10,000-100,000 organoids that further mature in 4-5 weeks into α- and β-like cells with glucose-responsive insulin and glucagon release. We detail procedures for culturing, passaging, and cryopreserving stem cells as suspended clusters and specify growth media and differentiation factors for differentiation. Finally, we discuss functional assays for research applications. For complete details on the use and execution of this protocol, please refer to Alvarez-Dominguez et al.1.

The beta cell-immune cell interface in type 1 diabetes (T1D)

BACKGROUND

T1D is an autoimmune disease in which pancreatic islets of Langerhans are infiltrated by immune cells resulting in the specific destruction of insulin-producing islet beta cells. Our understanding of the factors leading to islet infiltration and the interplay of the immune cells with target beta cells is incomplete, especially in human disease. While murine models of T1D have provided crucial information for both beta cell and autoimmune cell function, the translation of successful therapies in the murine model to human disease has been a challenge.

SCOPE OF REVIEW

Here, we discuss current state of the art and consider knowledge gaps concerning the interface of the islet beta cell with immune infiltrates, with a focus on T cells. We discuss pancreatic and immune cell phenotypes and their impact on cell function in health and disease, which we deem important to investigate further to attain a more comprehensive understanding of human T1D disease etiology.

MAJOR CONCLUSIONS

The last years have seen accelerated development of approaches that allow comprehensive study of human T1D. Critically, recent studies have contributed to our revised understanding that the pancreatic beta cell assumes an active role, rather than a passive position, during autoimmune disease progression. The T cell-beta cell interface is a critical axis that dictates beta cell fate and shapes autoimmune responses. This includes the state of the beta cell after processing internal and external cues (e.g., stress, inflammation, genetic risk) that that contributes to the breaking of tolerance by hyperexpression of human leukocyte antigen (HLA) class I with presentation of native and neoepitopes and secretion of chemotactic factors to attract immune cells. We anticipate that emerging insights about the molecular and cellular aspects of disease initiation and progression processes will catalyze the development of novel and innovative intervention points to provide additional therapies to individuals affected by T1D.

Permanent Neonatal diabetes-causing Insulin mutations have dominant negative effects on beta cell identity

Heterozygous coding sequence mutations of the INS gene are a cause of permanent neonatal diabetes (PNDM) that results from beta cell failure. We explored the causes of beta cell failure in two PNDM patients with two distinct INS mutations. Using b and mutated hESCs, we detected accumulation of misfolded proinsulin and impaired proinsulin processing in vitro, and a dominant-negative effect of these mutations on the in vivo performance of patient-derived SC-beta cells after transplantation into NSG mice. These insulin mutations derange endoplasmic reticulum (ER) homeostasis, and result in the loss of beta-cell mass and function. In addition to anticipated apoptosis, we found evidence of beta-cell dedifferentiation, characterized by an increase of cells expressing both Nkx6.1 and ALDH1A3, but negative for insulin and glucagon. These results highlight both known and novel mechanisms contributing to the loss and functional failure of human beta cells with specific insulin gene mutations.

Incomplete Reprogramming of DNA Replication Timing in Induced Pluripotent Stem Cells

Induced pluripotent stem cells (iPSC) are a widely used cell system and a foundation for cell therapy. Differences in gene expression, DNA methylation, and chromatin conformation, which have the potential to affect differentiation capacity, have been identified between iPSCs and embryonic stem cells (ESCs). Less is known about whether DNA replication timing - a process linked to both genome regulation and genome stability - is efficiently reprogrammed to the embryonic state. To answer this, we profiled and compared genome-wide replication timing between ESCs, iPSCs, and cells reprogrammed by somatic cell nuclear transfer (NT-ESCs). While NT-ESCs replicated their DNA in a manner indistinguishable from ESCs, a subset of iPSCs exhibit delayed replication at heterochromatic regions containing genes downregulated in iPSC with incompletely reprogrammed DNA methylation. DNA replication delays were not the result of gene expression and DNA methylation aberrations and persisted after differentiating cells to neuronal precursors. Thus, DNA replication timing can be resistant to reprogramming and lead to undesirable phenotypes in iPSCs, establishing it as an important genomic feature to consider when evaluating iPSC lines.

Single-nucleus multi-omics of human stem cell-derived islets identifies deficiencies in lineage specification

Insulin-producing β cells created from human pluripotent stem cells have potential as a therapy for insulin-dependent diabetes, but human pluripotent stem cell-derived islets (SC-islets) still differ from their in vivo counterparts. To better understand the state of cell types within SC-islets and identify lineage specification deficiencies, we used single-nucleus multi-omic sequencing to analyse chromatin accessibility and transcriptional profiles of SC-islets and primary human islets. Here we provide an analysis that enabled the derivation of gene lists and activity for identifying each SC-islet cell type compared with primary islets. Within SC-islets, we found that the difference between β cells and awry enterochromaffin-like cells is a gradient of cell states rather than a stark difference in identity. Furthermore, transplantation of SC-islets in vivo improved cellular identities overtime, while long-term in vitro culture did not. Collectively, our results highlight the importance of chromatin and transcriptional landscapes during islet cell specification and maturation.

Ca2+-Mediated Signaling Pathways: A Promising Target for the Successful Generation of Mature and Functional Stem Cell-Derived Pancreatic Beta Cells In Vitro

Diabetes mellitus is a chronic disease affecting over 500 million adults globally and is mainly categorized as type 1 diabetes mellitus (T1DM), where pancreatic beta cells are destroyed, and type 2 diabetes mellitus (T2DM), characterized by beta cell dysfunction. This review highlights the importance of the divalent cation calcium (Ca²⁺) and its associated signaling pathways in the proper functioning of beta cells and underlines the effects of Ca²⁺ dysfunction on beta cell function and its implications for the onset of diabetes. Great interest and promise are held by human pluripotent stem cell (hPSC) technology to generate functional pancreatic beta cells from diabetic patient-derived stem cells to replace the dysfunctional cells, thereby compensating for insulin deficiency and reducing the comorbidities of the disease and its associated financial and social burden on the patient and society. Beta-like cells generated by most current differentiation protocols have blunted functionality compared to their adult human counterparts. The Ca²⁺ dynamics in stem cell-derived beta-like cells and adult beta cells are summarized in this review, revealing the importance of proper Ca²⁺ homeostasis in beta-cell function. Consequently, the importance of targeting Ca²⁺ function in differentiation protocols is suggested to improve current strategies to use hPSCs to generate mature and functional beta-like cells with a comparable glucose-stimulated insulin secretion (GSIS) profile to adult beta cells.

Cellular therapies in liver and pancreatic diseases

Over the past two decades, developments in regenerative medicine in gastroenterology have been greatly enhanced by the application of stem cells, which can self-replicate and differentiate into any somatic cell. The discovery of induced pluripotent stem cells has opened remarkable perspectives on tissue regeneration, including their use as a bridge to transplantation or as supportive therapy in patients with organ failure. The improvements in DNA manipulation and gene editing strategies have also allowed to clarify the physiopathology and to correct the phenotype of several monogenic diseases, both in vivo and in vitro. Further progress has been made with the development of three-dimensional cultures, known as organoids, which have demonstrated morphological and functional complexity comparable to that of a miniature organ. Hence, owing to its protean applications and potential benefits, cell and organoid transplantation has become a hot topic for the management of gastrointestinal diseases. In this review, we describe current knowledge on cell therapies in hepatology and pancreatology, providing insight into their future applications in regenerative medicine.

The preclinical and clinical progress of cell sheet engineering in regenerative medicine

Cell therapy is an accessible method for curing damaged organs or tissues. Yet, this approach is limited by the delivery efficiency of cell suspension injection. Over recent years, biological scaffolds have emerged as carriers of delivering therapeutic cells to the target sites. Although they can be regarded as revolutionary research output and promote the development of tissue engineering, the defect of biological scaffolds in repairing cell-dense tissues is apparent. Cell sheet engineering (CSE) is a novel technique that supports enzyme-free cell detachment in the shape of a sheet-like structure. Compared with the traditional method of enzymatic digestion, products harvested by this technique retain extracellular matrix (ECM) secreted by cells as well as cell-matrix and intercellular junctions established during in vitro culture. Herein, we discussed the current status and recent progress of CSE in basic research and clinical application by reviewing relevant articles that have been published, hoping to provide a reference for the development of CSE in the field of stem cells and regenerative medicine.

A matrigel-free method for culture of pancreatic endocrine-like cells in defined protein-based hydrogels

The transplantation of pancreatic endocrine islet cells from cadaveric donors is a promising treatment for type 1 diabetes (T1D), which is a chronic autoimmune disease that affects approximately nine million people worldwide. However, the demand for donor islets outstrips supply. This problem could be solved by differentiating stem and progenitor cells to islet cells. However, many current culture methods used to coax stem and progenitor cells to differentiate into pancreatic endocrine islet cells require Matrigel, a matrix composed of many extracellular matrix (ECM) proteins secreted from a mouse sarcoma cell line. The undefined nature of Matrigel makes it difficult to determine which factors drive stem and progenitor cell differentiation and maturation. Additionally, it is difficult to control the mechanical properties of Matrigel without altering its chemical composition. To address these shortcomings of Matrigel, we engineered defined recombinant proteins roughly 41 kDa in size, which contain cell-binding ECM peptides derived from fibronectin (ELYAVTGRGDSPASSAPIA) or laminin alpha 3 (PPFLMLLKGSTR). The engineered proteins form hydrogels through association of terminal leucine zipper domains derived from rat cartilage oligomeric matrix protein. The zipper domains flank elastin-like polypeptides whose lower critical solution temperature (LCST) behavior enables protein purification through thermal cycling. Rheological measurements show that a 2% w/v gel of the engineered proteins display material behavior comparable to a Matrigel/methylcellulose-based culture system previously reported by our group to support the growth of pancreatic ductal progenitor cells. We tested whether our protein hydrogels in 3D culture could derive endocrine and endocrine progenitor cells from dissociated pancreatic cells of young (1-week-old) mice. We found that both protein hydrogels favored growth of endocrine and endocrine progenitor cells, in contrast to Matrigel-based culture. Because the protein hydrogels described here can be further tuned with respect to mechanical and chemical properties, they provide new tools for mechanistic study of endocrine cell differentiation and maturation.

An insulin hypersecretion phenotype precedes pancreatic β cell failure in MODY3 patient-specific cells

MODY3 is a monogenic hereditary form of diabetes caused by mutations in the transcription factor HNF1A. The patients progressively develop hyperglycemia due to perturbed insulin secretion, but the pathogenesis is unknown. Using patient-specific hiPSCs, we recapitulate the insulin secretion sensitivity to the membrane depolarizing agent sulfonylurea commonly observed in MODY3 patients. Unexpectedly, MODY3 patient-specific HNF1A^+/R272C β cells hypersecrete insulin both in vitro and in vivo after transplantation into mice. Consistently, we identified a trend of increased birth weight in human HNF1A mutation carriers compared with healthy siblings. Reduced expression of potassium channels, specifically the K_ATP channel, in MODY3 β cells, increased calcium signaling, and rescue of the insulin hypersecretion phenotype by pharmacological targeting ATP-sensitive potassium channels or low-voltage-activated calcium channels suggest that more efficient membrane depolarization underlies the hypersecretion of insulin in MODY3 β cells. Our findings identify a pathogenic mechanism leading to β cell failure in MODY3.

Stem cell-based multi-tissue platforms to model human autoimmune diabetes

BACKGROUND

Type 1 diabetes (T1D) is an autoimmune disease in which pancreatic insulin-producing β cells are specifically destroyed by the immune system. Understanding the initiation and progression of human T1D has been hampered by the lack of appropriate models that can reproduce the complexity and heterogeneity of the disease. The development of platforms combining multiple human pluripotent stem cell (hPSC) derived tissues to model distinct aspects of T1D has the potential to provide critical novel insights into the etiology and pathogenesis of the human disease.

SCOPE OF REVIEW

In this review, we summarize the state of hPSC differentiation approaches to generate cell types and tissues relevant to T1D, with a particular focus on pancreatic islet cells, T cells, and thymic epithelium. We present current applications as well as limitations of using these hPSC-derived cells for disease modeling and discuss efforts to optimize platforms combining multiple cell types to model human T1D. Finally, we outline remaining challenges and emphasize future improvements needed to accelerate progress in this emerging field of research.

MAJOR CONCLUSIONS

Recent advances in reprogramming approaches to create patient-specific induced pluripotent stem cell lines (iPSCs), genome engineering technologies to efficiently modify DNA of hPSCs, and protocols to direct their differentiation into mature cell types have empowered the use of stem cell derivatives to accurately model human disease. While challenges remain before complex interactions occurring in human T1D can be modeled with these derivatives, experiments combining hPSC-derived β cells and immune cells are already providing exciting insight into how these cells interact in the context of T1D, supporting the viability of this approach.

Challenges with Cell-based Therapies for Type 1 Diabetes Mellitus

Type 1 diabetes (T1D) is a chronic, lifelong metabolic disease. It is characterised by the autoimmune-mediated loss of insulin-producing pancreatic β cells in the islets of Langerhans (β-islets), resulting in disrupted glucose homeostasis. Administration of exogenous insulin is the most common management method for T1D, but this requires lifelong reliance on insulin injections and invasive blood glucose monitoring. Replacement therapies with beta cells are being developed as an advanced curative treatment for T1D. Unfortunately, this approach is limited by the lack of donated pancreatic tissue, the difficulties in beta cell isolation and viability maintenance, the longevity of the transplanted cells in vivo, and consequently high costs. Emerging approaches to address these limitations are under intensive investigations, including the production of insulin-producing beta cells from various stem cells, and the development of bioengineered devices including nanotechnologies for improving islet transplantation efficacy without the need for recipients taking toxic anti-rejection drugs. These emerging approaches present promising prospects, while the challenges with the new techniques need to be tackled for ultimately clinical treatment of T1D. This review discussed the benefits and limitations of the cell-based therapies for beta cell replacement as potential curative treatment for T1D, and the applications of bioengineered devices including nanotechnology to overcome the challenges associated with beta cell transplantation.

Reduced calcium levels and accumulation of abnormal insulin granules in stem cell models of HNF1A deficiency

Mutations in HNF1A cause Maturity Onset Diabetes of the Young (HNF1A-MODY). To understand mechanisms of β-cell dysfunction, we generated stem cell-derived pancreatic endocrine cells with hypomorphic mutations in HNF1A. HNF1A-deficient β-cells display impaired basal and glucose stimulated-insulin secretion, reduced intracellular calcium levels in association with a reduction in CACNA1A expression, and accumulation of abnormal insulin granules in association with SYT13 down-regulation. Knockout of CACNA1A and SYT13 reproduce the relevant phenotypes. In HNF1A deficient β-cells, glibenclamide, a sulfonylurea drug used in the treatment of HNF1A-MODY patients, increases intracellular calcium, and restores insulin secretion. While insulin secretion defects are constitutive in β-cells null for HNF1A, β-cells heterozygous for hypomorphic HNF1A (R200Q) mutations lose the ability to secrete insulin gradually; this phenotype is prevented by correction of the mutation. Our studies illuminate the molecular basis for the efficacy of treatment of HNF1A-MODY with sulfonylureas, and suggest promise for the use of cell therapies.

Intrinsic epigenetic control of angiogenesis in induced pluripotent stem cell-derived endothelium regulates vascular regeneration

Human-induced pluripotent stem cell-derived endothelial cells (iECs) provide opportunities to study vascular development and regeneration, develop cardiovascular therapeutics, and engineer model systems for drug screening. The differentiation and characterization of iECs are well established; however, the mechanisms governing their angiogenic phenotype remain unknown. Here, we aimed to determine the angiogenic phenotype of iECs and the regulatory mechanism controlling their regenerative capacity. In a comparative study with HUVECs, we show that iECs increased expression of vascular endothelial growth factor receptor 2 (VEGFR2) mediates their highly angiogenic phenotype via regulation of glycolysis enzymes, filopodia formation, VEGF mediated migration, and robust sprouting. We find that the elevated expression of VEGFR2 is epigenetically regulated via intrinsic acetylation of histone 3 at lysine 27 by histone acetyltransferase P300. Utilizing a zebrafish xenograft model, we demonstrate that the ability of iECs to promote the regeneration of the amputated fin can be modulated by P300 activity. These findings demonstrate how the innate epigenetic status of iECs regulates their phenotype with implications for their therapeutic potential.

Recent Progress of Research Regarding the Applications of Stem Cells for Treating Diabetes Mellitus

At present, the number of diabetes patients has exceeded 537 million worldwide and this number continues to increase. Stem cell therapy represents a new direction for the treatment of diabetes; the use of stem cells overcomes some shortcomings associated with traditional therapies. Functional β-cells play an important role in the pathogenesis of diabetes. As therapeutic targets, functional β-cells are restored by a variety of stem cells, including pluripotent stem cells, mesenchymal cells, and urine-derived stem cells. Although all types of stem cells have their own characteristics, they mainly promote the repair and regeneration of β-cells through directional differentiation, immunomodulation, and paracrine signaling after homing to the injured site. However, stem cell therapy still faces many obstacles, such as low long-term cell survival rate after transplantation, low maintenance time of blood glucose homeostasis, immune rejection, and tumorigenesis. Recently, genetically edited pluripotent stem cells and the co-transplantation of mesenchymal stem cells and islet cells have made significant progress in improving the efficacy of stem cell transplantation processes, also providing powerful tools for the study of the mechanisms underlying diabetes and disease modeling. In this review, we first focused on: (1) stem cells as a pool for the differentiation of insulin-producing cells; (2) stem cells as a source for regenerative repair of damaged islets and as a potential co-transplanted population with islets; (3) the potential of combining gene editing with stem cell therapy; and (4) selection of the stem cell transplantation approach. Based on these topics, we discuss the challenges within the field of adapting stem cell-supported and stem cell-derived transplantations, and the promising routes for overcoming these problems.

Stem Cell-Derived β Cells: A Versatile Research Platform to Interrogate the Genetic Basis of β Cell Dysfunction

Pancreatic β cell dysfunction is a central component of diabetes progression. During the last decades, the genetic basis of several monogenic forms of diabetes has been recognized. Genome-wide association studies (GWAS) have also facilitated the identification of common genetic variants associated with an increased risk of diabetes. These studies highlight the importance of impaired β cell function in all forms of diabetes. However, how most of these risk variants confer disease risk, remains unanswered. Understanding the specific contribution of genetic variants and the precise role of their molecular effectors is the next step toward developing treatments that target β cell dysfunction in the era of personalized medicine. Protocols that allow derivation of β cells from pluripotent stem cells, represent a powerful research tool that allows modeling of human development and versatile experimental designs that can be used to shed some light on diabetes pathophysiology. This article reviews different models to study the genetic basis of β cell dysfunction, focusing on the recent advances made possible by stem cell applications in the field of diabetes research.

OUP accepted manuscript

Insulin-producing stem cell-derived islets (SC-islets) provide a virtually unlimited cell source for diabetes cell replacement therapy. While SC-islets are less functional when first differentiated in vitro compared to isolated cadaveric islets, transplantation into mice has been shown to increase their maturation. To understand the effects of transplantation on maturation and function of SC-islets, we examined the effects of cell dose, transplantation strategy, and diabetic state in immunocompromised mice. Transplantation of 2 and 5, but not 0.75 million SC-islet cells underneath the kidney capsule successfully reversed diabetes in mice with pre-existing diabetes. SQ and intramuscular injections failed to reverse diabetes at all doses and had undetectable expression of maturation markers, such as MAFA and FAM159B. Furthermore, SC-islets had similar function and maturation marker expression regardless of diabetic state. Our results illustrate that transplantation parameters are linked to SC-islet function and maturation, providing ideal mouse models for preclinical diabetes SC therapy research.

OUP accepted manuscript

Although genome profiling provides important genetic and phenotypic details for applying precision medicine to diabetes, it is imperative to integrate in vitro human cell models, accurately recapitulating the genetic alterations associated with diabetes. The absence of the appropriate preclinical human models and the unavailability of genetically relevant cells substantially limit the progress in developing personalized treatment for diabetes. Human pluripotent stem cells (hPSCs) provide a scalable source for generating diabetes-relevant cells carrying the genetic signatures of the patients. Remarkably, allogenic hPSC-derived pancreatic progenitors and β cells are being used in clinical trials with promising preliminary results. Autologous hiPSC therapy options exist for those with monogenic and type 2 diabetes; however, encapsulation or immunosuppression must be accompanied with in the case of type 1 diabetes. Furthermore, genome-wide association studies-identified candidate variants can be introduced in hPSCs for deciphering the associated molecular defects. The hPSC-based disease models serve as excellent resources for drug development facilitating personalized treatment. Indeed, hPSC-based diabetes models have successfully provided valuable knowledge by modeling different types of diabetes, which are discussed in this review. Herein, we also evaluate their strengths and shortcomings in dissecting the underlying pathogenic molecular mechanisms and discuss strategies for improving hPSC-based disease modeling investigations.

Engineering islets from stem cells for advanced therapies of diabetes

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

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

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

Monogenic Diabetes Modeling: In Vitro Pancreatic Differentiation From Human Pluripotent Stem Cells Gains Momentum

The occurrence of diabetes mellitus is characterized by pancreatic β cell loss and chronic hyperglycemia. While Type 1 and Type 2 diabetes are the most common types, rarer forms involve mutations affecting a single gene. This characteristic has made monogenic diabetes an interesting disease group to model in vitro using human pluripotent stem cells (hPSCs). By altering the genotype of the original hPSCs or by deriving human induced pluripotent stem cells (hiPSCs) from patients with monogenic diabetes, changes in the outcome of the in vitro differentiation protocol can be analyzed in detail to infer the regulatory mechanisms affected by the disease-associated genes. This approach has been so far applied to a diversity of genes/diseases and uncovered new mechanisms. The focus of the present review is to discuss the latest findings obtained by modeling monogenic diabetes using hPSC-derived pancreatic cells generated in vitro. We will specifically focus on the interpretation of these studies, the advantages and limitations of the models used, and the future perspectives for improvement.

Gene-edited human stem cell-derived β cells from a patient with monogenic diabetes reverse preexisting diabetes in mice

Differentiation of insulin-producing pancreatic β cells from induced pluripotent stem cells (iPSCs) derived from patients with diabetes promises to provide autologous cells for diabetes cell replacement therapy. However, current approaches produce patient iPSC-derived β (SC-β) cells with poor function in vitro and in vivo. Here, we used CRISPR-Cas9 to correct a diabetes-causing pathogenic variant in Wolfram syndrome 1 (WFS1) in iPSCs derived from a patient with Wolfram syndrome (WS). After differentiation to β cells with our recent six-stage differentiation strategy, corrected WS SC-β cells performed robust dynamic insulin secretion in vitro in response to glucose and reversed preexisting streptozocin-induced diabetes after transplantation into mice. Single-cell transcriptomics showed that corrected SC-β cells displayed increased insulin and decreased expression of genes associated with endoplasmic reticulum stress. CRISPR-Cas9 correction of a diabetes-inducing gene variant thus allows for robust differentiation of autologous SC-β cells that can reverse severe diabetes in an animal model.

Chemical combinations potentiate human pluripotent stem cell-derived 3D pancreatic progenitor clusters toward functional β cells

Human pluripotent stem cell (hPSC)-derived pancreatic β cells are an attractive cell source for treating diabetes. However, current derivation methods remain inefficient, heterogeneous, and cell line dependent. To address these issues, we first devised a strategy to efficiently cluster hPSC-derived pancreatic progenitors into 3D structures. Through a systematic study, we discovered 10 chemicals that not only retain the pancreatic progenitors in 3D clusters but also enhance their potentiality towards NKX6.1+/INS+ β cells. We further systematically screened signaling pathway modulators in the three steps from pancreatic progenitors toward β cells. The implementation of all these strategies and chemical combinations resulted in generating β cells from different sources of hPSCs with high efficiency. The derived β cells are functional and can reverse hyperglycemia in mice within two weeks. Our protocol provides a robust platform for studying human β cells and developing hPSC-derived β cells for cell replacement therapy.

Applications of iPSC-derived beta cells from patients with diabetes

Improved stem cell-derived pancreatic islet (SC-islet) differentiation protocols robustly generate insulin-secreting β cells from patient induced pluripotent stem cells (iPSCs). These advances are enabling in vitro disease modeling studies and the development of an autologous diabetes cell replacement therapy. SC-islet technology elucidates key features of human pancreas development and diabetes disease progression through the generation of pancreatic progenitors, endocrine progenitors, and β cells derived from diabetic and nondiabetic iPSCs. Combining disease modeling with gene editing and next-generation sequencing reveals the impact of diabetes-causing mutations and diabetic phenotypes on multiple islet cell types. In addition, the supply of SC-islets, containing β and other islet cell types, is unlimited, presenting an opportunity for personalized medicine and overcoming several disadvantages posed by donor islets. This review highlights relevant studies involving iPSC-β cells and progenitors, encompassing new conclusions involving cells from patients with diabetes and the therapeutic potential of iPSC-β cells.

Improved differentiation protocols generate pancreatic islet from patient stem cells

Diabetic stem cell-derived islet studies identified key markers for cell function

Gene editing aims to address unmet needs for stem cell therapy field

Stem cell-derived islets are a promising source for diabetes stem cell therapy

Diagnosis and treatment of type 1 diabetes at the dawn of the personalized medicine era

Type 1 diabetes affects millions of people globally and requires careful management to avoid serious long-term complications, including heart and kidney disease, stroke, and loss of sight. The type 1 diabetes patient cohort is highly heterogeneous, with individuals presenting with disease at different stages and severities, arising from distinct etiologies, and overlaying varied genetic backgrounds. At present, the “one-size-fits-all” treatment for type 1 diabetes is exogenic insulin substitution therapy, but this approach fails to achieve optimal blood glucose control in many individuals. With advances in our understanding of early-stage diabetes development, diabetes stratification, and the role of genetics, type 1 diabetes is a promising candidate for a personalized medicine approach, which aims to apply “the right therapy at the right time, to the right patient”. In the case of type 1 diabetes, great efforts are now being focused on risk stratification for diabetes development to enable pre-clinical detection, and the application of treatments such as gene therapy, to prevent pancreatic destruction in a sub-set of patients. Alongside this, breakthroughs in stem cell therapies hold great promise for the regeneration of pancreatic tissues in some individuals. Here we review the recent initiatives in the field of personalized medicine for type 1 diabetes, including the latest discoveries in stem cell and gene therapy for the disease, and current obstacles that must be overcome before the dream of personalized medicine for all type 1 diabetes patients can be realized.

Reduced replication fork speed promotes pancreatic endocrine differentiation and controls graft size

Limitations in cell proliferation are important for normal function of differentiated tissues and essential for the safety of cell replacement products made from pluripotent stem cells, which have unlimited proliferative potential. To evaluate whether these limitations can be established pharmacologically, we exposed pancreatic progenitors differentiating from human pluripotent stem cells to small molecules that interfere with cell cycle progression either by inducing G₁ arrest or by impairing S phase entry or S phase completion and determined growth potential, differentiation, and function of insulin-producing endocrine cells. We found that the combination of G₁ arrest with a compromised ability to complete DNA replication promoted the differentiation of pancreatic progenitor cells toward insulin-producing cells and could substitute for endocrine differentiation factors. Reduced replication fork speed during differentiation improved the stability of insulin expression, and the resulting cells protected mice from diabetes without the formation of cystic growths. The proliferative potential of grafts was proportional to the reduction of replication fork speed during pancreatic differentiation. Therefore, a compromised ability to enter and complete S phase is a functionally important property of pancreatic endocrine differentiation, can be achieved by reducing replication fork speed, and is an important determinant of cell-intrinsic limitations of growth.

Modeling different types of diabetes using human pluripotent stem cells

Diabetes mellitus (DM) is a metabolic disease characterized by chronic hyperglycemia as a result of progressive loss of pancreatic β cells, which could lead to several debilitating complications. Different paths, triggered by several genetic and environmental factors, lead to the loss of pancreatic β cells and/or function. Understanding these many paths to β cell damage or dysfunction could help in identifying therapeutic approaches specific for each path. Most of our knowledge about diabetes pathophysiology has been obtained from studies on animal models, which do not fully recapitulate human diabetes phenotypes. Currently, human pluripotent stem cell (hPSC) technology is a powerful tool for generating in vitro human models, which could provide key information about the disease pathogenesis and provide cells for personalized therapies. The recent progress in generating functional hPSC-derived β cells in combination with the rapid development in genomic and genome-editing technologies offer multiple options to understand the cellular and molecular mechanisms underlying the development of different types of diabetes. Recently, several in vitro hPSC-based strategies have been used for studying monogenic and polygenic forms of diabetes. This review summarizes the current knowledge about different hPSC-based diabetes models and how these models improved our current understanding of the pathophysiology of distinct forms of diabetes. Also, it highlights the progress in generating functional β cells in vitro, and discusses the current challenges and future perspectives related to the use of the in vitro hPSC-based strategies.

Pancreatic β cell regeneration induced by clinical and preclinical agents

Diabetes, one of the most common chronic diseases in the modern world, has pancreatic β cell deficiency as a major part of its pathophysiological mechanism. Pancreatic regeneration is a potential therapeutic strategy for the recovery of β cell loss. However, endocrine islets have limited regenerative capacity, especially in adult humans. Almost all hypoglycemic drugs can protect β cells by inhibiting β cell apoptosis and dedifferentiation via correction of hyperglycemia and amelioration of the consequent inflammation and oxidative stress. Several agents, including glucagon-like peptide-1 and γ-aminobutyric acid, have been shown to promote β cell proliferation, which is considered the main source of the regenerated β cells in adult rodents, but with less clarity in humans. Pancreatic progenitor cells might exist and be activated under particular circumstances. Artemisinins and γ-aminobutyric acid can induce α-to-β cell conversion, although some disputes exist. Intestinal endocrine progenitors can transdeterminate into insulin-producing cells in the gut after FoxO1 deletion, and pharmacological research into FoxO1 inhibition is ongoing. Other cells, including pancreatic acinar cells, can transdifferentiate into β cells, and clinical and preclinical strategies are currently underway. In this review, we summarize the clinical and preclinical agents used in different approaches for β cell regeneration and make some suggestions regarding future perspectives for clinical application.

Use of Induced Pluripotent Stem Cells to Build Isogenic Systems and Investigate Type 1 Diabetes

Type 1 diabetes (T1D) is a disease that arises due to complex immunogenetic mechanisms. Key cell-cell interactions involved in the pathogenesis of T1D are activation of autoreactive T cells by dendritic cells (DC), migration of T cells across endothelial cells (EC) lining capillary walls into the islets of Langerhans, interaction of T cells with macrophages in the islets, and killing of β-cells by autoreactive CD8⁺ T cells. Overall, pathogenic cell-cell interactions are likely regulated by the individual's collection of genetic T1D-risk variants. To accurately model the role of genetics, it is essential to build systems to interrogate single candidate genes in isolation during the interactions of cells that are essential for disease development. However, obtaining single-donor matched cells relevant to T1D is a challenge. Sourcing these genetic variants from human induced pluripotent stem cells (iPSC) avoids this limitation. Herein, we have differentiated iPSC from one donor into DC, macrophages, EC, and β-cells. Additionally, we also engineered T cell avatars from the same donor to provide an in vitro platform to study genetic influences on these critical cellular interactions. This proof of concept demonstrates the ability to derive an isogenic system from a single donor to study these relevant cell-cell interactions. Our system constitutes an interdisciplinary approach with a controlled environment that provides a proof-of-concept for future studies to determine the role of disease alleles (e.g. IFIH1, PTPN22, SH2B3, TYK2) in regulating cell-cell interactions and cell-specific contributions to the pathogenesis of T1D.

The Utility of Exosomes in Diagnosis and Therapy of Diabetes Mellitus and Associated Complications

Diabetes mellitus and the associated complications are metabolic diseases with high morbidity that result in poor quality of health and life. The lack of diagnostic methods for early detection results in patients losing the best treatment opportunity. Oral hypoglycemics and exogenous insulin replenishment are currently the most common therapeutic strategies, which only yield temporary glycemic control rather than curing the disease and its complications. Exosomes are nanoparticles containing bioactive molecules reflecting individual physiological status, regulating metabolism, and repairing damaged tissues. They function as biomarkers of diabetes mellitus and diabetic complications. Considering that exosomes are bioactive molecules, can be obtained from body fluid, and have cell-type specificity, in this review, we highlight the multifold effects of exosomes in the pathology and therapy of diabetes mellitus and diabetic complications.

Human Pluripotent Stem Cells to Model Islet Defects in Diabetes

Diabetes mellitus is characterized by elevated levels of blood glucose and is ultimately caused by insufficient insulin production from pancreatic beta cells. Different research models have been utilized to unravel the molecular mechanisms leading to the onset of diabetes. The generation of pancreatic endocrine cells from human pluripotent stem cells constitutes an approach to study genetic defects leading to impaired beta cell development and function. Here, we review the recent progress in generating and characterizing functional stem cell-derived beta cells. We summarize the diabetes disease modeling possibilities that stem cells offer and the challenges that lie ahead to further improve these models.

Human T Cells Expressing a CD19 CAR-T Receptor Provide Insights into Mechanisms of Human CD19-Positive β Cell Destruction

Autoimmune destruction of pancreatic β cells underlies type 1 diabetes (T1D). To understand T cell-mediated immune effects on human pancreatic β cells, we combine β cell-specific expression of a model antigen, CD19, and anti-CD19 chimeric antigen receptor T (CAR-T) cells. Coculturing CD19-expressing β-like cells and CD19 CAR-T cells results in T cell-mediated β-like cell death with release of activated T cell cytokines. Transcriptome analysis of β-like cells and human islets treated with conditioned medium of the immune reaction identifies upregulation of immune reaction genes and the pyroptosis mediator GSDMD as well as its activator CASP4. Caspase-4-mediated cleaved GSDMD is detected in β-like cells under inflammation and endoplasmic reticulum (ER) stress conditions. Among immune-regulatory genes, PDL1 is one of the most upregulated, and PDL1 overexpression partially protects human β-like cells transplanted into mice. This experimental platform identifies potential mechanisms of β cell destruction and may allow testing of therapeutic strategies.

CD19-expressing β-like cells differentiated from human ES cells are functional

Tractable in vitro and in vivo killing of CD19-expressing β-like cells by CAR-T cells

Upregulation of pyroptosis factors GSDMD and CAPS4 during β-like cell inflammation

PDL1-overexpressing in β-like cells partially protects against reactive T cells

Pluripotent stem cells with low differentiation potential contain incompletely reprogrammed DNA replication

Reprogrammed pluripotent stem cells (PSCs) are valuable for research and potentially for cell replacement therapy. However, only a fraction of reprogrammed PSCs are developmentally competent. Genomic stability and accurate DNA synthesis are fundamental for cell development and critical for safety. We analyzed whether defects in DNA replication contribute to genomic instability and the diverse differentiation potentials of reprogrammed PSCs. Using a unique single-molecule approach, we visualized DNA replication in isogenic PSCs generated by different reprogramming approaches, either somatic cell nuclear transfer (NT-hESCs) or with defined factors (iPSCs). In PSCs with lower differentiation potential, DNA replication was incompletely reprogrammed, and genomic instability increased during replicative stress. Reprogramming of DNA replication did not correlate with DNA methylation. Instead, fewer replication origins and a higher frequency of DNA breaks in PSCs with incompletely reprogrammed DNA replication were found. Given the impact of error-free DNA synthesis on the genomic integrity and differentiation proficiency of PSCs, analyzing DNA replication may be a useful quality control tool.

Programming pluripotent stem cells: Can't teach an old cell new DNA replication tricks

Pluripotent stem cells differentiate with varying efficiencies depending on the method of reprogramming that created them. In this issue, Paniza et al. (2020. J. Cell Biol.https://doi.org/10.1083/jcb.201909163) demonstrate that cells with lower differentiation potential retain some features of somatic DNA replication origin utilization and suffer more frequent DNA damage.

Loss of the transcription factor MAFB limits β-cell derivation from human PSCs

Next generation sequencing studies have highlighted discrepancies in β-cells which exist between mice and men. Numerous reports have identified MAF BZIP Transcription Factor B (MAFB) to be present in human β-cells postnatally, while its expression is restricted to embryonic and neo-natal β-cells in mice. Using CRISPR/Cas9-mediated gene editing, coupled with endocrine cell differentiation strategies, we dissect the contribution of MAFB to β-cell development and function specifically in humans. Here we report that MAFB knockout hPSCs have normal pancreatic differentiation capacity up to the progenitor stage, but favor somatostatin- and pancreatic polypeptide–positive cells at the expense of insulin- and glucagon-producing cells during endocrine cell development. Our results describe a requirement for MAFB late in the human pancreatic developmental program and identify it as a distinguishing transcription factor within islet cell subtype specification. We propose that hPSCs represent a powerful tool to model human pancreatic endocrine development and associated disease pathophysiology.

The MAF bZIP transcription factor B (MAFB) is present in postnatal human beta cells but its role is unclear. Here, the authors show that MAFB regulates endocrine pancreatic cell fate specification.

Targeting the cytoskeleton to direct pancreatic differentiation of human pluripotent stem cells

Generation of pancreatic β cells from human pluripotent stem cells (hPSCs) holds promise as a cell replacement therapy for diabetes. In this study, we establish a link between the state of the actin cytoskeleton and the expression of pancreatic transcription factors that drive pancreatic lineage specification. Bulk and single-cell RNA sequencing demonstrated that different degrees of actin polymerization biased cells toward various endodermal lineages and that conditions favoring a polymerized cytoskeleton strongly inhibited neurogenin 3-induced endocrine differentiation. Using latrunculin A to depolymerize the cytoskeleton during endocrine induction, we developed a two-dimensional differentiation protocol for generating human pluripotent stem-cell-derived β (SC-β) cells with improved in vitro and in vivo function. SC-β cells differentiated from four hPSC lines exhibited first- and second-phase dynamic glucose-stimulated insulin secretion. Transplantation of islet-sized aggregates of these cells rapidly reversed severe preexisting diabetes in mice at a rate close to that of human islets and maintained normoglycemia for at least 9 months.

GLP-1 receptor agonists synergize with DYRK1A inhibitors to potentiate functional human β cell regeneration

Glucagon-like peptide-1 receptor (GLP1R) agonists and dipeptidyl peptidase 4 inhibitors are widely prescribed diabetes drugs due to their ability to stimulate insulin secretion from remaining β cells and to reduce caloric intake. Unfortunately, they fail to increase human β cell proliferation. Small-molecule inhibitors of dual-specificity tyrosine-regulated kinase 1A (DYRK1A) are able to induce adult human β cell proliferation, but rates are modest (~2%), and their specificity to β cells is limited. Here, we provide evidence that combining any member of the GLP1R agonist class with any member of the DYRK1A inhibitor class induces a synergistic increase in human β cell replication (5 to 6%) accompanied by an actual increase in numbers of human β cells. GLP1R agonist-DYRK1A inhibitor synergy required combined inhibition of DYRK1A and an increase in cAMP and did not lead to β cell dedifferentiation. These beneficial effects on proliferation were seen in both normal human β cells and β cells derived from individuals with type 2 diabetes. The ability of the GLP1R agonist-DYRK1A inhibitor combination to enhance human β cell proliferation, human insulin secretion, and blood glucose control extended in vivo to studies of human islets transplanted into euglycemic and streptozotocin-diabetic immunodeficient mice. No adverse events were observed in the mouse studies during a 1-week period. Because of the relative β cell specificity of GLP1R agonists, the combination provides an improved, although not complete, degree of human β cell specificity.

Murine Perinatal β-Cell Proliferation and the Differentiation of Human Stem Cell-Derived Insulin-Expressing Cells Require NEUROD1

Inactivation of the β-cell transcription factor NEUROD1 causes diabetes in mice and humans. In this study, we uncovered novel functions of NEUROD1 during murine islet cell development and during the differentiation of human embryonic stem cells (HESCs) into insulin-producing cells. In mice, we determined that Neurod1 is required for perinatal proliferation of α- and β-cells. Surprisingly, apoptosis only makes a minor contribution to β-cell loss when Neurod1 is deleted. Inactivation of NEUROD1 in HESCs severely impaired their differentiation from pancreatic progenitors into insulin-expressing (HESC-β) cells; however, survival or proliferation was not affected at the time points analyzed. NEUROD1 was also required in HESC-β cells for the full activation of an essential β-cell transcription factor network. These data reveal conserved and distinct functions of NEUROD1 during mouse and human β-cell development and maturation, with important implications about the function of NEUROD1 in diabetes.

Human stem cell models: lessons for pancreatic development and disease

A comprehensive understanding of mechanisms that underlie the development and function of human cells requires human cell models. For the pancreatic lineage, protocols have been developed to differentiate human pluripotent stem cells (hPSCs) into pancreatic endocrine and exocrine cells through intermediates resembling in vivo development. In recent years, this differentiation system has been employed to decipher mechanisms of pancreatic development, congenital defects of the pancreas, as well as genetic forms of diabetes and exocrine diseases. In this review, we summarize recent insights gained from studies of pancreatic hPSC models. We discuss how genome-scale analyses of the differentiation system have helped elucidate roles of chromatin state, transcription factors, and noncoding RNAs in pancreatic development and how the analysis of cells with disease-relevant mutations has provided insight into the molecular underpinnings of genetically determined diseases of the pancreas.

Advances in β-cell replacement therapy for the treatment of type 1 diabetes

The main goal of treatment for type 1 diabetes is to control glycaemia with insulin therapy to reduce disease complications. For some patients, technological approaches to insulin delivery are inadequate, and allogeneic islet transplantation is a safe alternative for those patients who have had severe hypoglycaemia complicated by impaired hypoglycaemia awareness or glycaemic lability, or who already receive immunosuppressive drugs for a kidney transplant. Since 2000, intrahepatic islet transplantation has proven efficacious in alleviating the burden of labile diabetes and preventing complications related to diabetes, whether or not a previous kidney transplant is present. Age, body-mass index, renal status, and cardiopulmonary status affect the choice between pancreas or islet transplantation. Access to transplantation is limited by the number of deceased donors and the necessity of immunosuppression. Future approaches might include alternative sources of islets (eg, xenogeneic tissue or human stem cells), extrahepatic sites of implantation (eg, omental, subcutaneous, or intramuscular), and induction of immune tolerance or encapsulation of islets.