Enrichment of human embryonic stem cell-derived NKX6.1-expressing pancreatic progenitor cells accelerates the maturation of insulin-secreting cells in vivo

Oxygenation strategies for encapsulated islet and beta cell transplants

Human allogeneic islet transplantation (ITx) is emerging as a promising treatment option for qualified patients with type 1 diabetes. However, widespread clinical application of allogeneic ITx is hindered by two critical barriers: the need for systemic immunosuppression and the limited supply of human islet tissue. Biocompatible, retrievable immunoisolation devices containing glucose-responsive insulin-secreting tissue may address both critical barriers by enabling the more effective and efficient use of allogeneic islets without immunosuppression in the near-term, and ultimately the use of a cell source with a virtually unlimited supply, such as human stem cell-derived β-cells or xenogeneic (porcine) islets with minimal or no immunosuppression. However, even though encapsulation methods have been developed and immunoprotection has been successfully tested in small and large animal models and to a limited extent in proof-of-concept clinical studies, the effective use of encapsulation approaches to convincingly and consistently treat diabetes in humans has yet to be demonstrated. There is increasing consensus that inadequate oxygen supply is a major factor limiting their clinical translation and routine implementation. Poor oxygenation negatively affects cell viability and β-cell function, and the problem is exacerbated with the high-density seeding required for reasonably-sized clinical encapsulation devices. Approaches for enhanced oxygen delivery to encapsulated tissues in implantable devices are therefore being actively developed and tested. This review summarizes fundamental aspects of islet microarchitecture and β-cell physiology as well as encapsulation approaches highlighting the need for adequate oxygenation; it also evaluates existing and emerging approaches for enhanced oxygen delivery to encapsulation devices, particularly with the advent of β-cell sources from stem cells that may enable the large-scale application of this approach.

Stem cells in the treatment of diabetes mellitus - Focus on mesenchymal stem cells

Diabetes mellitus type 1 and type 2 have become a global epidemic with dramatically increasing incidences. Poorly controlled diabetes is associated with severe life-threatening complications. Beside traditional treatment with insulin and oral anti-diabetic drugs, clinicians try to improve patient's care by cell therapies using embryonic stem cells (ESC), induced pluripotent stem cells (iPSC) and adult mesenchymal stem cells (MSC). ESC display a virtually unlimited plasticity, including the differentiation into insulin producing β-cells, but they raise ethical concerns and bear, like iPSC, the risk of tumours. IPSC may further inherit somatic mutations and remaining somatic transcriptional memory upon incomplete re-programming, but allow the generation of patient/disease-specific cell lines. MSC avoid such issues but have not been successfully differentiated into β-cells. Instead, MSC and their pericyte phenotypes outside the bone marrow have been recognized to secrete numerous immunomodulatory and tissue regenerative factors. On this account, the term 'medicinal signaling cells' has been proposed to define the new conception of a 'drug store' for injured tissues and to stay with the MSC nomenclature. This review presents the biological background and the resulting clinical potential and limitations of ESC, iPSC and MSC, and summarizes the current status quo of cell therapeutic concepts and trials.

Generation of pancreatic β cells for treatment of diabetes: advances and challenges

Human embryonic stem cells (hESC) and induced pluripotent stem cells (hiPSC) are considered attractive sources of pancreatic β cells and islet organoids. Recently, several reports presented that hESC/iPSC-derived cells enriched with specific transcription factors can form glucose-responsive insulin-secreting cells in vitro and transplantation of these cells ameliorates hyperglycemia in diabetic mice. However, the glucose-stimulated insulin-secreting capacity of these cells is lower than that of endogenous islets, suggesting the need to improve induction procedures. One of the critical problems facing in vivo maturation of hESC/iPSC-derived cells is their low survival rate after transplantation, although this rate increases when the implanted pancreatic cells are encapsulated to avoid the immune response. Several groups have also reported on the generation of hESC/iPSC-derived islet-like organoids, but development of techniques for complete islet structures with the eventual generation of vascularized constructs remains a major challenge to their application in regenerative therapies. Many issues also need to be addressed before the successful clinical application of hESC/iPSC-derived cells or islet organoids. In this review, we summarize advances in the generation of hESC/iPSC-derived pancreatic β cells or islet organoids and discuss the limitations and challenges for their successful therapeutic application in diabetes.

(Re)generating Human Beta Cells: Status, Pitfalls, and Perspectives

Diabetes mellitus results from disturbed glucose homeostasis due to an absolute (type 1) or relative (type 2) deficiency of insulin, a peptide hormone almost exclusively produced by the beta cells of the endocrine pancreas in a tightly regulated manner. Current therapy only delays disease progression through insulin injection and/or oral medications that increase insulin secretion or sensitivity, decrease hepatic glucose production, or promote glucosuria. These drugs have turned diabetes into a chronic disease as they do not solve the underlying beta cell defects or entirely prevent the long-term complications of hyperglycemia. Beta cell replacement through islet transplantation is a more physiological therapeutic alternative but is severely hampered by donor shortage and immune rejection. A curative strategy should combine newer approaches to immunomodulation with beta cell replacement. Success of this approach depends on the development of practical methods for generating beta cells, either in vitro or in situ through beta cell replication or beta cell differentiation. This review provides an overview of human beta cell generation.

Concise Review: Human Pluripotent Stem Cells for the Modeling of Pancreatic β-Cell Pathology

Pancreatic β‐cells are the only source of insulin. Disturbances in β‐cell development or function may thus result in insulin deficiency or excess, presenting as hyper‐ or hypoglycemia. It is increasingly evident that common forms of diabetes (types 1 and 2) are pathogenically heterogeneous. Development of efficient therapies is dependent on reliable disease models. Although animal models are remarkably useful research tools, they present limitations because of species differences. As an alternative, human pluripotent stem cell technologies offer multiple possibilities for the study of human diseases in vitro. In the last decade, advances in the derivation of induced pluripotent stem cells from diabetic patients, combined with β‐cell differentiation protocols, have resulted in the generation of useful disease models for diabetes. First disease models have been focusing on monogenic diabetes. The development of genome editing technologies, more advanced differentiation protocols and humanized mouse models based on transplanted cells have opened new horizons for the modeling of more complex forms of β‐cell dysfunction. We present here the incremental progress made in the modeling of diabetes using pluripotent stem cells. We discuss the current challenges and opportunities of these approaches to dissect β‐cell pathology and devise new pharmacological and cell replacement therapies. stem cells2019;37:33–41

Pluripotent Stem Cell-Derived Pancreatic Progenitors and β-Like Cells for Type 1 Diabetes Treatment

In this review, we focus on the processes guiding human pancreas development and provide an update on methods to efficiently generate pancreatic progenitors (PPs) and β-like cells in vitro from human pluripotent stem cells (hPSCs). Furthermore, we assess the strengths and weaknesses of using PPs and β-like cell for cell replacement therapy for the treatment of Type 1 diabetes with respect to cell manufacturing, engrafting, functionality, and safety. Finally, we discuss the identification and use of specific cell surface markers to generate safer populations of PPs for clinical translation and to study the development of PPs in vivo and in vitro.

Pancreatic resident endocrine progenitors demonstrate high islet neogenic fidelity and committed homing towards diabetic mice pancreas

Pancreatic progenitors have been explored for their profound characteristics and unique commitment to generate new functional islets in regenerative medicine. Pancreatic resident endocrine progenitors (PREPs) with mesenchymal stem cell (MSC) phenotype were purified from BALB/c mice pancreas and characterized. PREPs were differentiated into mature islet clusters in vitro by activin-A and swertisin and functionally characterized. A temporal gene and protein profiling was performed during differentiation. Furthermore, PREPs were labeled with green fluorescent protein (GFP) and transplanted intravenously into streptozotocin (STZ) diabetic mice while monitoring their homing and differentiation leading to amelioration in the diabetic condition. PREPs were positive for unique progenitor markers and transcription factors essential for endocrine pancreatic homeostasis along with having the multipotent MSC phenotype. These cells demonstrated high fidelity for islet neogenesis in minimum time (4 days) to generate mature functional islet clusters (shortest reported period for any isolated stem/progenitor). Furthermore, GFP-labeled PREPs transplanted in STZ diabetic mice migrated and localized within the injured pancreas without trapping in any other major organ and differentiated rapidly into insulin-producing cells without an external stimulus. A rapid decrease in fasting blood glucose levels toward normoglycemia along with significant increase in fasting serum insulin levels was observed, which ameliorated the diabetic condition. This study highlights the unique potential of PREPs to generate mature islets within the shortest period and their robust homing toward the damaged pancreas, which ameliorated the diabetic condition suggesting PREPs affinity toward their niche, which can be exploited and extended to other stem cell sources in diabetic therapeutics.

Pancreatic Beta Cell Differentiation From Human Pluripotent Stem Cells

Insulin-expressing beta cells are crucial for the maintenance of systemic glucose homeostasis. Elucidation of the molecular and cellular mechanisms of beta cell development, expansion, survival, and function are required for full understanding of the molecular pathogenesis of diabetes. However, access to human beta cells for such studies is limited by virtue of the logistics of acquisition, prior medical status of donor, and imperfect culture systems for maintaining beta cell identity and function after isolation from human pancreas. Here, a technique for generation of beta cells from human pluripotent stem cells (hPSCs) by modification of key signaling pathways during islet development is described. Up to 70% C-peptide-positive beta cells can be obtained from endodermal anlagen after 27 days of differentiation with specific growth factors and small molecules. Although 50% of them are monohormonal C-peptide-positive cells and have molecular and cellular characteristics consistent with human beta cells in the Islets of Langerhans, a sub-population co-expressing other endocrine markers are also generated, indicating the immaturity of these cells. © 2018 by John Wiley & Sons, Inc.

Generation and selection of pluripotent stem cells for robust differentiation to insulin-secreting cells capable of reversing diabetes in rodents

Induced pluripotent stem cell (iPSC) technology enables the creation and selection of pluripotent cells with specific genetic traits. This report describes a pluripotent cell line created specifically to form replacement pancreatic cells as a therapy for insulin-dependent diabetes. Beginning with primary pancreatic tissue acquired through organ donation, cells were isolated, re-programmed using non-integrating vectors and exposed to a four day differentiation protocol to generate definitive endoderm, a developmental precursor to pancreas. The best performing iPSC lines were then subjected to a 12-day basic differentiation protocol to generate endocrine pancreas precursors. The line that most consistently generated highly pure populations was selected for further development. This approach created an iPSC-variant cell line, SR1423, with a genetic profile correlated with preferential differentiation toward endodermal lineage at the loss of mesodermal potential. This report further describes an improved differentiation protocol that, coupled with SR1423, generated populations of greater than 60% insulin-expressing cells that secrete insulin in response to glucose and are capable of reversing diabetes in rodents. Created and banked following cGMP guidelines, SR1423 is a candidate cell line for the production of insulin-producing cells useful for the treatment of diabetes.

3D heterogeneous islet organoid generation from human embryonic stem cells using a novel engineered hydrogel platform

Organoids, which exhibit spontaneous organ specific organization, function, and multi-cellular complexity, are in essence the in vitro reproduction of specific in vivo organ systems. Recent work has demonstrated human pluripotent stem cells (hPSCs) as a viable regenerative cell source for tissue-specific organoid engineering. This is especially relevant for engineering islet organoids, due to the recent advances in generating functional beta-like cells from human pluripotent stem cells. In this study, we report specific engineering of regenerative islet organoids of precise size and cellular heterogeneity, using a novel hydrogel system, Amikagel. Amikagel facilitated controlled and spontaneous aggregation of human embryonic stem cell derived pancreatic progenitor cells (hESC-PP) into robust homogeneous spheroids. This platform further allowed fine control over the integration of multiple cell populations to produce heterogeneous spheroids, which is a necessity for complex organoid engineering. Amikagel induced hESC-PP spheroid formation enhanced pancreatic islet-specific Pdx-1 and NKX6.1 gene and protein expression, while also increasing the percentage of committed population. hESC-PP spheroids were further induced towards mature beta-like cells which demonstrated increased Beta-cell specific INS1 gene and C-peptide protein expression along with functional insulin production in response to in vitro glucose challenge. Further integration of hESC-PP with biologically relevant supporting endothelial cells resulted in multicellular organoids which demonstrated spontaneous maturation towards islet-specific INS1 gene and C-peptide protein expression along with a significantly developed extracellular matrix support system. These findings establish Amikagel -facilitated platform ideal for islet organoid engineering.

Microporous Polymer Scaffolds for the Transplantation of Embryonic Stem Cell Derived Pancreatic Progenitors to a Clinically Translatable Site for the Treatment of Type I Diabetes

Type I diabetes mellitus, which affects an estimated 1.5 million Americans, is caused by autoimmune destruction of the pancreatic beta cells that results in the need for life-long insulin therapy. Allogeneic islet transplantation for the treatment of type I diabetes is a therapy in which donor islets are infused intrahepatically, which has led to the transient reversal of diabetes. However, therapeutic limitations of allogeneic transplantation, which include a shortage of donor islets, long-term immunosuppression, and high risk of tissue rejection, have led to the investigation of embryonic or induced pluripotent stem cells as an unlimited source of functional beta-cells. Herein, we investigate the use of microporous scaffolds for their ability to promote the engraftment of stem cell derived pancreatic progenitors and their maturation toward mono-hormonal insulin producing β-cells at a clinically translatable, extrahepatic site. Initial studies demonstrated that microporous scaffolds supported cell engraftment, and their maturation to become insulin positive; however, the number of insulin positive cells and the levels of C-peptide secretion were substantially lower than what was observed with progenitor cell transplantation into the kidney capsule. The scaffolds were subsequently modified to provide a sustained release of exendin-4, which has previously been employed to promote maturation of pancreatic progenitors in vitro and has been employed to promote engraftment of transplanted islets in the peritoneal fat. Transplantation of stem cell derived pancreatic progenitors on scaffolds releasing exendin-4 led to significantly increased C-peptide production compared to scaffolds without exendin-4, with C-peptide and blood glucose levels comparable to the kidney capsule transplantation cohort. Image analysis of insulin and glucagon producing cells indicated that monohormonal insulin producing cells were significantly greater compared to glucagon producing and polyhormonal cells in scaffolds releasing exendin-4, whereas a significantly decreased percentage of insulin-producing cells were present among hormone producing cells in scaffolds without exendin-4. Collectively, a microporous scaffold, capable of localized and sustained delivery of exendin-4, enhanced the maturation and function of pluripotent stem cell derived pancreatic progenitors that were transplanted to a clinically translatable site.

NKX6.1 induced pluripotent stem cell reporter lines for isolation and analysis of functionally relevant neuronal and pancreas populations

Recent studies have reported significant advances in the differentiation of human pluripotent stem cells to clinically relevant cell types such as the insulin producing beta-like cells and motor neurons. However, many of the current differentiation protocols lead to heterogeneous cell cultures containing cell types other than the targeted cell fate. Genetically modified human pluripotent stem cells reporting the expression of specific genes are of great value for differentiation protocol optimization and for the purification of relevant cell populations from heterogeneous cell cultures. Here we present the generation of human induced pluripotent stem cell (iPSC) lines with a GFP reporter inserted in the endogenous NKX6.1 locus. Characterization of the reporter lines demonstrated faithful GFP labelling of NKX6.1 expression during pancreas and motor neuron differentiation. Cell sorting and gene expression profiling by RNA sequencing revealed that NKX6.1-positive cells from pancreatic differentiations closely resemble human beta cells. Furthermore, functional characterization of the isolated cells demonstrated that glucose-stimulated insulin secretion is mainly confined to the NKX6.1-positive cells. We expect that the NKX6.1-GFP iPSC lines and the results presented here will contribute to the further refinement of differentiation protocols and characterization of hPSC-derived beta cells and motor neurons for disease modelling and cell replacement therapies.

Rho-Associated Kinases and Non-muscle Myosin IIs Inhibit the Differentiation of Human iPSCs to Pancreatic Endoderm

There has been increasing success with the generation of pancreatic cells from human induced pluripotent stem cells (hiPSCs); however, the molecular mechanisms of the differentiation remain elusive. The purpose of this study was to reveal novel molecular mechanisms for differentiation to PDX1⁺NKX6.1⁺ pancreatic endoderm cells, which are pancreatic committed progenitor cells. PDX1⁺ posterior foregut cells differentiated from hiPSCs failed to differentiate into pancreatic endoderm cells at low cell density, but Rho-associated kinase (ROCK) or non-muscle myosin II (NM II) inhibitors rescued the differentiation potential. Consistently, the expression of phosphorylated myosin light chain 2 and NM IIA was downregulated in aggregation culture. Notably, the soluble factors we tested were substantially effective only with ROCK-NM II inhibition. The PDX1⁺NKX6.1⁺ cells induced with NM II inhibitors were successfully engrafted and maturated in vivo. Taken together, these results suggest that NM IIs play inhibitory roles for the differentiation of hiPSCs to pancreatic endoderm cells.

Differentiation of human pluripotent stem cells into two distinct NKX6.1 populations of pancreatic progenitors

BACKGROUND

The expression of a specific combination of transcription factors (TFs) in the multipotent progenitor cells (MPCs) is critical for determining pancreatic cell fate. NKX6.1 expression in PDX1⁺ MPCs is required for functional β cell generation. We have recently demonstrated the generation of a novel population of human pluripotent stem cell (hPSC)-derived MPCs that exclusively express NKX6.1, independently of PDX1 (PDX1^-/NKX6.1⁺). Therefore, the aim of this study was to characterize this novel population to elucidate its role in pancreatic development.

METHODS

The hPSCs were exposed to two differentiation protocols to generate MPCs that were analyzed using different techniques.

RESULTS

Based on the expression of PDX1 and NKX6.1, we generated three different populations of MPCs, two of them were NKX6.1⁺. One of these NKX6.1 populations coexpressed PDX1 (PDX1⁺/NKX6.1⁺) which is known to mature into functional β cells, and an additional novel population did not express PDX1 (PDX1^-/NKX6.1⁺) with an undefined role in pancreatic cell fate. This novel population was enriched using our recently established protocol, allowing their reorganization in three-dimensional (3D) structures. Since NKX6.1 induction in MPCs can direct them to endocrine and/or ductal cells in humans, we examined the coexpression of endocrine and ductal markers. We found that the expression of the pancreatic endocrine progenitor markers chromogranin A (CHGA) and neurogenin 3 (NGN3) was not detected in the NKX6.1⁺ 3D structures, while few structures were positive for NKX2.2, another endocrine progenitor marker, thereby shedding light on the origin of this novel population and its role in pancreatic endocrine development. Furthermore, SOX9 was highly expressed in the 3D structures, but cytokeratin 19, a main ductal marker, was not detected in these structures.

CONCLUSIONS

These data support the existence of two independent NKX6.1⁺ MPC populations during human pancreatic development and the novel PDX1^-/NKX6.1⁺ population may be involved in a unique trajectory to generate β cells in humans.

Sex Differences in Maturation of Human Embryonic Stem Cell-Derived β Cells in Mice

Pancreatic progenitors derived from human embryonic stem cells (hESCs) are now in clinical trials for insulin replacement in patients with type 1 diabetes. Animal studies indicate that pancreatic progenitor cells can mature into a mixed population of endocrine cells, including glucose-responsive β cells several months after implantion. However, it remains unclear how conditions in the recipient may influence the maturation and ultimately the function of these hESC-derived cells. Here, we investigated the effects of (1) pregnancy on the maturation of human stage 4 (S4) pancreatic progenitor cells and (2) the impact of host sex on both S4 cells and more mature stage 7 (S7) pancreatic endocrine cells implanted under the kidney capsule of immunodeficient SCID-beige mice. Pregnancy led to increased proliferation of endogenous pancreatic β cells, but did not appear to affect proliferation or maturation of S4 cells at midgestation. Interestingly, S4 and S7 cells both acquired glucose-stimulated C-peptide secretion in females before males. Moreover, S4 cells lowered fasting blood glucose levels in females sooner than in males, whereas the responses with S7 cells were similar. These data indicate that the host sex may impact the maturation of hESC-derived cells in vivo and that this effect can be minimized by more advanced differentiation of the cells before implantation.

Functional Beta Cell Mass from Device-Encapsulated hESC-Derived Pancreatic Endoderm Achieving Metabolic Control

Human stem cells represent a potential source for implants that replace the depleted functional beta cell mass (FBM) in diabetes patients. Human embryonic stem cell-derived pancreatic endoderm (hES-PE) can generate implants with glucose-responsive beta cells capable of reducing hyperglycemia in mice. This study with device-encapsulated hES-PE (4 × 10⁶ cells/mouse) determines the biologic characteristics at which implants establish metabolic control during a 50-week follow-up. A metabolically adequate FBM was achieved by (1) formation of a sufficient beta cell number (>0.3 × 10⁶/mouse) at >50% endocrine purity and (2) their maturation to a functional state comparable with human pancreatic beta cells, as judged by their secretory responses during perifusion, their content in typical secretory vesicles, and their nuclear NKX6.1-PDX1-MAFA co-expression. Assessment of FBM in implants and its correlation with in vivo metabolic markers will guide clinical translation of stem cell-derived grafts in diabetes.

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Human stem cell-derived pancreatic precursors generate functional beta cell mass

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Cellular markers identify metabolically adequate human stem cell-generated implants

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Significance of determining beta cell number and maturation in implants

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Functional implants differ in endocrine composition from endocrine pancreas

Enhanced differentiation of human pluripotent stem cells into pancreatic progenitors co-expressing PDX1 and NKX6.1

Background

Pancreatic progenitors (PPs) co-expressing the two transcription factors (TFs) PDX1 and NKX6.1 are recognized as the indispensable precursors of functional pancreatic β cells. Here, we aimed to establish an efficient protocol for maximizing generation of PDX1⁺/NKX6.1⁺ PPs from human pluripotent stem cells (hPSCs).

Methods

In order to enhance the PDX1⁺/NKX6.1⁺ population, we manipulated in vitro culture conditions during differentiation by dissociating densely formed endodermal cells and re-plating them at different densities. These dissociated cells were subjected to an augmented duration of retinoid and fibroblast growth factor (FGF)10 signaling to induce higher PDX1 and NKX6.1 expression.

Results

Our optimized protocol dramatically increased the expression of NKX6.1, leading to an increase in the proportion of PDX1⁺/NKX6.1⁺ progenitors (~90%) in monolayer, higher than the previously published protocols, as well as upregulated key TFs controlling pancreatic development. The improved efficiency of pancreatic differentiation was complemented by an inhibited hepatic specification and an increased proliferation of NKX6.1⁺ cells. Interestingly, we were able to enrich a novel PDX1^–/NKX6.1⁺ population by manipulating the re-plating density; these oriented themselves in three-dimensional clusters. Further differentiation validated the ability of our PDX1⁺/NKX6.1⁺ progenitors to generate NGN3⁺ endocrine progenitors.

Conclusions

We provide a novel technique that facilitates appropriate cellular rearrangement in monolayer culture to yield a high proportion of PDX1⁺/NKX6.1⁺ PPs with an elevated self-replicating capacity, thereby aiding scalable production of functional β cells from hPSCs in vitro. Our innovative method also enriches a novel NKX6.1⁺/PDX1^– population, with characteristics of proposed endocrine precursors, allowing further studies on deciphering routes to β-cell development.

Electronic supplementary material

The online version of this article (doi:10.1186/s13287-017-0759-z) contains supplementary material, which is available to authorized users.

An arduous journey from human pluripotent stem cells to functional pancreatic β cells

Type 1 and type 2 diabetes are caused by a destruction and decrease in the number of functional insulin-producing β cells, respectively; therefore, the generation of functional β cells from human embryonic stem cells and human induced pluripotent stem cells, collectively known as human pluripotent stem cells (hPSCs), for potential cell replacement therapy and disease modelling is an intensely investigated area. Recent scientific breakthroughs enabled derivation of large quantities of human pancreatic β-like cells in vitro, although with varied glucose-stimulated insulin secretion kinetics. In the present review, we comprehensively summarize, compare and critically analyze the intricacies of these developing technologies, including differentiation platforms, robustness of protocols, and methodologies used to characterize hPSC-derived β-like cells. We also discuss experimental issues that need to be resolved before these β-like cells can be used clinically.

Evaluating KIND1 human embryonic stem cell-derived pancreatic progenitors to ameliorate streptozotocin-induced diabetes in mice

Background & objectives:

Diabetes is a global disease burden. Various stem cell types are being explored to serve as an alternative source of islets. This study was conducted to evaluate the ability of in-house developed human embryonic stem (hES) cells-derived pancreatic progenitors to ameliorate diabetic symptoms in mice.

Methods:

Pancreatic progenitors were packed in macro-capsules and transplanted into six male Swiss mice and four mice were taken as controls. Thirty days post-transplantation, diabetes was induced by streptozotocin treatment. Mice were then followed up for >100 days and body weight and blood glucose levels were regularly monitored.

Results:

Control mice lost weight, maintained high glucose levels and did not survive beyond 40 days, whereas transplanted group maintained body weight and four of the six mice had lowered blood glucose levels. About five-fold increase was observed in human C-peptide levels in the recipients of progenitor transplants as compared to diabetic control.

Interpretation & conclusions:

The beneficial effect of transplanted cells was not long-lasting. Further studies are required to critically evaluate and compare the potential of endogenous pluripotent stem cells and hES cells-derived progenitors before moving from bench to the bedside.

Efficient Generation of Glucose-Responsive Beta Cells from Isolated GP2+ Human Pancreatic Progenitors

Stem cell-based therapy for type 1 diabetes would benefit from implementation of a cell purification step at the pancreatic endoderm stage. This would increase the safety of the final cell product, allow the establishment of an intermediate-stage stem cell bank, and provide a means for upscaling β cell manufacturing. Comparative gene expression analysis revealed glycoprotein 2 (GP2) as a specific cell surface marker for isolating pancreatic endoderm cells (PECs) from differentiated hESCs and human fetal pancreas. Isolated GP2⁺ PECs efficiently differentiated into glucose responsive insulin-producing cells in vitro. We found that in vitro PEC proliferation declines due to enhanced expression of the cyclin-dependent kinase (CDK) inhibitors CDKN1A and CDKN2A. However, we identified a time window when reducing CDKN1A or CDKN2A expression increased proliferation and yield of GP2⁺ PECs. Altogether, our results contribute tools and concepts toward the isolation and use of PECs as a source for the safe production of hPSC-derived β cells.

Beta-cell replacement strategies for diabetes

Diabetes is characterized by elevated levels of blood glucose as a result of insufficient production of insulin from loss or dysfunction of pancreatic islet β-cells. Here, we review several approaches to replacing β-cells that were recently discussed at a symposium held in Kyoto, Japan. Transplant of donor human islets can effectively treat diabetes and eliminate the need for insulin injections, supporting research aimed at identifying abundant supplies of cells. Studies showing the feasibility of producing mouse islets in rats support the concept of generating pigs with human pancreas that can serve as donors of human islets, although scientific and ethical challenges remain. Alternatively, in vitro differentiation of both human embryonic stem cells and induced pluripotent stem cells is being actively pursued as an islet cell source, and embryonic stem cell-derived pancreatic progenitor cells are now in clinical trials in North America in patients with diabetes. Macro-encapsulation devices are being used to contain and protect the cells from immune attack, and alternate strategies of immune-isolation are being pursued, such as islets contained within long microfibers. Recent advancements in genetic engineering tools offer exciting opportunities to broaden therapeutic strategies and to probe the genetic involvement in β-cell failure that contributes to diabetes. Personalized medicine might eventually become a possibility with genetically edited patient-induced pluripotent stem cells, and the development of simplified robust differentiation protocols that ideally become standardized and automated. Additional efforts to develop a safe and effective β-cell replacement strategy to treat diabetes are warranted.

Regenerative medicine and cell-based approaches to restore pancreatic function

The pancreas is a complex organ with exocrine and endocrine components. Many pathologies impair exocrine function, including chronic pancreatitis, cystic fibrosis and pancreatic ductal adenocarcinoma. Conversely, when the endocrine pancreas fails to secrete sufficient insulin, patients develop diabetes mellitus. Pathology in either the endocrine or exocrine pancreas results in devastating economic and personal consequences. The current standard therapy for treating patients with type 1 diabetes mellitus is daily exogenous insulin injections, but cell sources of insulin provide superior glycaemic regulation and research is now focused on the goal of regenerating or replacing β cells. Stem-cell-based models might be useful to study exocrine pancreatic disorders, and mesenchymal stem cells or secreted factors might delay disease progression. Although the standards that bioengineered cells must meet before being considered as a viable therapy are not yet established, any potential therapy must be acceptably safe and functionally superior to current therapies. Here, we describe progress and challenges in cell-based methods to restore pancreatic function, with a focus on optimizing the site for cell delivery and decreasing requirements for immunosuppression through encapsulation. We also discuss the tools and strategies being used to generate exocrine pancreas and insulin-producing β-cell surrogates in situ and highlight obstacles to clinical application.

Single-Cell Gene Expression Analysis of a Human ESC Model of Pancreatic Endocrine Development Reveals Different Paths to β-Cell Differentiation

The production of insulin-producing β cells from human embryonic stem cells (hESCs) in vitro represents a promising strategy for a cell-based therapy for type 1 diabetes mellitus. To explore the cellular heterogeneity and temporal progression of endocrine progenitors and their progeny, we performed single-cell qPCR on more than 500 cells across several stages of in vitro differentiation of hESCs and compared them with human islets. We reveal distinct subpopulations along the endocrine differentiation path and an early lineage bifurcation toward either polyhormonal cells or β-like cells. We uncover several similarities and differences with mouse development and reveal that cells can take multiple paths to the same differentiation state, a principle that could be relevant to other systems. Notably, activation of the key β-cell transcription factor NKX6.1 can be initiated before or after endocrine commitment. The single-cell temporal resolution we provide can be used to improve the production of functional β cells.

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Single-cell qPCR identifies subpopulations on hESC to endocrine differentiation paths

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All hESC-derived endocrine cells transcribe multiple hormones in vitro

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A subpopulation of hESC-derived INS⁺ cells transcriptionally resembles adult β cells

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NKX6.1 onset before or after endocrine commitment leads to β-cell differentiation

Glycoprotein 2 is a specific cell surface marker of human pancreatic progenitors

PDX1+/NKX6-1+ pancreatic progenitors (PPs) give rise to endocrine cells both in vitro and in vivo. This cell population can be successfully differentiated from human pluripotent stem cells (hPSCs) and hold the potential to generate an unlimited supply of β cells for diabetes treatment. However, the efficiency of PP generation in vitro is highly variable, negatively impacting reproducibility and validation of in vitro and in vivo studies, and consequently, translation to the clinic. Here, we report the use of a proteomics approach to phenotypically characterize hPSC-derived PPs and distinguish these cells from non-PP populations during differentiation. Our analysis identifies the pancreatic secretory granule membrane major glycoprotein 2 (GP2) as a PP-specific cell surface marker. Remarkably, GP2 is co-expressed with NKX6-1 and PTF1A in human developing pancreata, indicating that it marks the multipotent pancreatic progenitors in vivo. Finally, we show that isolated hPSC-derived GP2+ cells generate β-like cells (C-PEPTIDE+/NKX6-1+) more efficiently compared to GP2- and unsorted populations, underlining the potential therapeutic applications of GP2.Pancreatic progenitors (PPs) can be derived from human pluripotent stem cells in vitro but efficiency of differentiation varies, making it hard to sort for insulin-producing cells. Here, the authors use a proteomic approach to identify the secretory granule membrane glycoprotein 2 as a marker for PDX1+/NKX6-1+ PPs.

Reprogramming human gallbladder cells into insulin-producing β-like cells

The gallbladder and cystic duct (GBCs) are parts of the extrahepatic biliary tree and share a common developmental origin with the ventral pancreas. Here, we report on the very first genetic reprogramming of patient-derived human GBCs to β-like cells for potential autologous cell replacement therapy for type 1 diabetes. We developed a robust method for large-scale expansion of human GBCs ex vivo. GBCs were reprogrammed into insulin-producing pancreatic β-like cells by a combined adenoviral-mediated expression of hallmark pancreatic endocrine transcription factors PDX1, MAFA, NEUROG3, and PAX6 and differentiation culture in vitro. The reprogrammed GBCs (rGBCs) strongly induced the production of insulin and pancreatic endocrine genes and these responded to glucose stimulation in vitro. rGBCs also expressed an islet-specific surface marker, which was used to enrich for the most highly reprogrammed cells. More importantly, global mRNA and microRNA expression profiles and protein immunostaining indicated that rGBCs adopted an overall β-like state and these rGBCs engrafted in immunodeficient mice. Furthermore, comparative global expression analyses identified putative regulators of human biliary to β cell fate conversion. In summary, we have developed, for the first time, a reliable and robust genetic reprogramming and culture expansion of primary human GBCs—derived from multiple unrelated donors—into pancreatic β-like cells ex vivo, thus showing that human gallbladder is a potentially rich source of reprogrammable cells for autologous cell therapy in diabetes.

Identification of a small molecule that facilitates the differentiation of human iPSCs/ESCs and mouse embryonic pancreatic explants into pancreatic endocrine cells

AIMS/HYPOTHESIS

Pancreatic beta-like cells generated from human induced pluripotent stem cells (hiPSCs) or human embryonic stem cells (hESCs) offer an appealing donor tissue source. However, differentiation protocols that mainly use growth factors are costly. Therefore, in this study, we aimed to establish efficient differentiation protocols to change hiPSCs/hESCs to insulin (INS)⁺ cells using novel small-molecule inducers.

METHODS

We screened small molecules that increased the induction rate of INS⁺ cells from hESC-derived pancreatic and duodenal homeobox 1 (PDX1)⁺ pancreatic progenitor cells. The differentiation protocol to generate INS⁺ cells from hiPSCs/hESCs was optimised using hit compounds, and INS⁺ cells induced with the compounds were characterised for their in vitro and in vivo functions. The inducing activity of the hit compounds was also examined using mouse embryonic pancreatic tissues in an explant culture system. Finally, RNA sequencing analyses were performed on the INS⁺ cells to elucidate the mechanisms of action by which the hit compounds induced pancreatic endocrine differentiation.

RESULTS

One hit compound, sodium cromoglicate (SCG), was identified out of approximately 1250 small molecules screened. When SCG was combined with a previously described protocol, the induction rate of INS⁺ cells increased from a mean ± SD of 5.9 ± 1.5% (n = 3) to 16.5 ± 2.1% (n = 3). SCG induced neurogenin 3-positive cells at a mean ± SD of 32.6 ± 4.6% (n = 3) compared with 14.2 ± 3.6% (n = 3) for control treatment without SCG, resulting in an increased generation of endocrine cells including insulin-producing cells. Similar induction by SCG was confirmed using mouse embryonic pancreatic explants. We also confirmed that the mechanisms of action by which SCG induced pancreatic endocrine differentiation included the inhibition of bone morphogenetic protein 4 signalling.

CONCLUSIONS/INTERPRETATION

SCG improves the generation of pancreatic endocrine cells from multiple hiPSC/hESC lines and mouse embryonic pancreatic explants by facilitating the differentiation of endocrine precursors. This discovery will contribute to elucidating the mechanisms of pancreatic endocrine development and facilitate cost-effective generation of INS⁺ cells from hiPSCs/hESCs.

DATA AVAILABILITY

The RNA sequencing data generated during the current study are available in the Gene Expression Omnibus ( www.ncbi.nlm.nih.gov/geo ) with series accession number GSE89973.

Cell Therapy for Type 1 Diabetes: Current and Future Strategies

PURPOSE OF THE REVIEW

Type 1 diabetes (T1D) is defined by an autoimmune destruction of insulin producing β-cells located in the endocrine part of the pancreas, the islets of Langerhans. As exogenous insulin administration fails at preventing severe complications associated with this disease, cell replacement therapies are being considered as a means to treat T1D. The purpose of this manuscript is to review the challenges associated with current strategies and discuss the potential of stem cell therapy for the treatment of T1D.

RECENT FINDINGS

The most prominent therapy offered to T1D patients is exogenous insulin administration which, despite formulations improvement, remains a suboptimal treatment, due to the frequency of injections and the issues associated with precise dosing. As immunotherapy approaches have remained unsuccessful, the only cure for T1D is transplantation of donor-derived pancreas or islets. However, donor scarcity, graft loss, and immune response to the foreign tissue are issues challenging this approach and limiting the number of patients who can benefit from such treatments. In this review, we discuss the causes of T1D and the shortcomings of the current treatments. Furthermore, we summarize the cutting edge research that aims to tackle the current challenges in reaching a quality-controlled product with long-term effects, with a focus on regenerative medicine approaches using human pluripotent stem cells.

Advances in islet encapsulation technologies

Type 1 diabetes is an autoimmune disorder in which the immune system attacks and destroys insulin-producing islet cells of the pancreas. Although islet transplantation has proved to be successful for some patients with type 1 diabetes, its widespread use is limited by islet donor shortage and the requirement for lifelong immunosuppression. An encapsulation strategy that can prevent the rejection of xenogeneic islets or of stem cell-derived allogeneic islets can potentially eliminate both of these barriers. Although encapsulation technology has met several challenges, the convergence of expertise in materials, nanotechnology, stem cell biology and immunology is allowing us to get closer to the goal of encapsulated islet cell therapy for humans.

MicroRNA expression profiles of human iPSCs differentiation into insulin-producing cells

AIMS

MicroRNAs are a class of small noncoding RNAs, which control gene expression by inhibition of mRNA translation. MicroRNAs are involved in the control of biological processes including cell differentiation. Here, we aim at characterizing microRNA expression profiles during differentiation of human induced pluripotent stem cells (hiPSCs) into insulin-producing cells.

METHODS

We differentiated hiPSCs toward endocrine pancreatic lineage following a 18-day protocol. We analyzed genes and microRNA expression levels using RT real-time PCR and TaqMan microRNA arrays followed by bioinformatic functional analysis.

RESULTS

MicroRNA expression profiles analysis of undifferentiated hiPSCs during pancreatic differentiation revealed that 347/768 microRNAs were expressed at least in one time point of all samples. We observed 18 microRNAs differentially expressed: 11 were upregulated (miR-9-5p, miR-9-3p, miR-10a, miR-99a-3p, miR-124a, miR-135a, miR-138, miR-149, miR-211, miR-342-3p and miR-375) and 7 downregulated (miR-31, miR-127, miR-143, miR-302c-3p, miR-373, miR-518b and miR-520c-3p) during differentiation into insulin-producing cells. Selected microRNAs were further evaluated during differentiation of Sendai-virus-reprogrammed hiPSCs using an improved endocrine pancreatic beta cell derivation protocol and, moreover, in differentiated NKX6.1⁺ sorted cells. Following Targetscan7.0 analysis of target genes of differentially expressed microRNAs and gene ontology classification, we found that such target genes belong to categories of major significance in pancreas organogenesis and development or exocytosis.

CONCLUSIONS

We detected a specific hiPSCs microRNAs signature during differentiation into insulin-producing cells and demonstrated that differentially expressed microRNAs target several genes involved in pancreas organogenesis.

GATA6 Plays an Important Role in the Induction of Human Definitive Endoderm, Development of the Pancreas, and Functionality of Pancreatic β Cells

Induced pluripotent stem cells were created from a pancreas agenesis patient with a mutation in GATA6. Using genome-editing technology, additional stem cell lines with mutations in both GATA6 alleles were generated and demonstrated a severe block in definitive endoderm induction, which could be rescued by re-expression of several different GATA family members. Using the endodermal progenitor stem cell culture system to bypass the developmental block at the endoderm stage, cell lines with mutations in one or both GATA6 alleles could be differentiated into β-like cells but with reduced efficiency. Use of suboptimal doses of retinoic acid during pancreas specification revealed a more severe phenotype, more closely mimicking the patient’s disease. GATA6 mutant β-like cells fail to secrete insulin upon glucose stimulation and demonstrate defective insulin processing. These data show that GATA6 plays a critical role in endoderm and pancreas specification and β-like cell functionality in humans.

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GATA6 is required for definitive endoderm specification in human ES/iPS cells

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Bypassing the endoderm defect allows GATA6 mutants to generate β-like cells

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Suboptimal retinoic acid signaling blocks pancreas specification in GATA6 mutants

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GATA6 is critical for human β cell function in vitro

Development of Islet Organoids from H9 Human Embryonic Stem Cells in Biomimetic 3D Scaffolds

Success in the differentiating human embryonic stem cells (hESCs) into insulin-secreting β cells raises new hopes for diabetes treatment. In this work, we demonstrated the feasibility of developing islet organoids from hESCs within biomimetic 3D scaffolds. We showed that such a 3D microenvironment is critical to the generation of pancreatic endoderm and endocrine from hESCs. The organoids formed consisted of pancreatic α, β, δ, and pancreatic polypeptide (PP) cells. A high-level co-expression of PDX1, NKX6.1, and NGN3 in these cells suggests the characteristics of pancreatic β cells. More importantly, most insulin-secreting cells generated did not express glucagon, somatostatin, or PP. The expression of mature β cell marker genes such as Pdx1, Ngn3, Insulin, MafA, and Glut2 was detected in these 3D-induced cell clusters. A high-level expression of C-peptide confirmed the de novo endogenous insulin production in these 3D induced cells. Insulin-secretory granules, an indication of β cell maturity, were detected in these cells as well. Glucose challenging experiments suggested that these cells are sensitive to glucose levels due to their elevated maturity. Exposing the cells to a high concentration of glucose induced a sharp increase in insulin secretion.

Zebrafish Pancreas Development and Regeneration: Fishing for Diabetes Therapies

The zebrafish pancreas shares its basic organization and cell types with the mammalian pancreas. In addition, the developmental pathways that lead to the establishment of the pancreatic islets of Langherhans are generally conserved from fish to mammals. Zebrafish provides a powerful tool to probe the mechanisms controlling establishment of the pancreatic endocrine cell types from early embryonic progenitor cells, as well as the regeneration of endocrine cells after damage. This knowledge is, in turn, applicable to refining protocols to generate renewable sources of human pancreatic islet cells that are critical for regulation of blood sugar levels. Here, we review how previous and ongoing studies in zebrafish and beyond are influencing the understanding of molecular mechanisms underlying various forms of diabetes and efforts to develop cell-based approaches to cure this increasingly widespread disease.

Effective endothelial cell and human pluripotent stem cell interactions generate functional insulin-producing beta cells

AIMS/HYPOTHESIS

Endothelial cells (ECs) play an essential role in pancreatic organogenesis. We hypothesise that effective in vitro interactions between human microvascular endothelial cells (HMECs) and human pluripotent stem cells (hPSCs) results in the generation of functional pancreatic beta cells.

METHODS

Embryoid bodies (EBs) derived from hPSCs were cultured alone (controls) or with ECs in collagen gels. Subsequently, cells were analysed for pancreatic beta cell markers, and then isolated and expanded. Insulin secretion in response to glucose was evaluated in vitro by static and dynamic (perifusion) assays, and in vivo by EB transplantation into immunodeficient mice.

RESULTS

Co-cultured EBs had a higher expression of mature beta cells markers and enhanced insulin secretion in vitro, compared with controls. In mice, transplanted EBs had higher levels of human C-peptide secretion with a significant reduction in hyperglycaemia after the selective destruction of native pancreatic beta cells. In addition, there was significant in vitro upregulation of bone morphogenetic proteins 2 and 4 (BMP-2, 4) in co-cultured cells, compared with controls.

CONCLUSIONS/INTERPRETATION

ECs provide essential signalling in vitro, such as activation of the BMP pathway, for derivation of functional insulin-producing beta cells from hPSCs.

The state of the art of islet transplantation and cell therapy in type 1 diabetes

In patients with type 1 diabetes (T1D), pancreatic β cells are destroyed by a selective autoimmune attack and their replacement with functional insulin-producing cells is the only possible cure for this disease. The field of islet transplantation has evolved significantly from the breakthrough of the Edmonton Protocol in 2000, since significant advances in islet isolation and engraftment, together with improved immunosuppressive strategies, have been reported. The main limitations, however, remain the insufficient supply of human tissue and the need for lifelong immunosuppression therapy. Great effort is then invested in finding innovative sources of insulin-producing β cells. One old alternative with new recent perspectives is the use of non-human donor cells, in particular porcine β cells. Also the field of preexisting β cell expansion has advanced, with the development of new human β cell lines. Yet, large-scale production of human insulin-producing cells from stem cells is the most recent and promising alternative. In particular, the optimization of in vitro strategies to differentiate human embryonic stem cells into mature insulin-secreting β cells has made considerable progress and recently led to the first clinical trial of stem cell treatment for T1D. Finally, the discovery that it is possible to derive human induced pluripotent stem cells from somatic cells has raised the possibility that a sufficient amount of patient-specific β cells can be derived from patients through cell reprogramming and differentiation, suggesting that in the future there might be a cell therapy without immunosuppression.

Xeno-Transplantation of macro-encapsulated islets and Pluripotent Stem Cell-Derived Pancreatic Progenitors without Immunosuppression

Islet transplantation effectively treats diabetes but relies on immune suppression and is practically limited by the number of cadaveric islets available. An alternative cellular source is insulin-producing cells derived from pluripotent cell sources. Three animal cohorts were used in the current study to evaluate whether an oxygen-providing macro-encapsulation device, 'βAIR', could function in conjunction with human embryonic stem cells (hESCs) and their derivatives. The first cohort received macro-encapsulated undifferentiated hESCs, a second cohort received hESCs differentiated to a pancreatic progenitor state with limited endocrine differentiation. A reference cohort received human islets. Macro-encapsulation devices were implanted subcutaneously and monitored for up to 4 months. Undifferentiated pluripotent stem cells did not form teratoma but underwent cell death following implantation. Human C-peptide (hC- peptide) was detectable in host serum one week after implantation for both other cohorts. hC-peptide levels decreasing over time but remained detectable up to the end of the study. Key factors associated with mature endocrine cells were observed in grafts recovered from cohorts containing islets and hESC-derivatives including C-peptide, insulin, glucagon and urocortin 3. We conclude that the 'βAIR' macroencapsulation device is compatible with both human islets and pluripotent derivatives, but has a limited capability of sustaining undifferentiated pluripotent cells.

Replacing and safeguarding pancreatic β cells for diabetes

Pluripotent stem cells are a scalable source of pancreatic cells for transplantation into patients with diabetes. Here, we describe how the field is gaining momentum toward a β cell replacement therapy.

Revisiting the immunocytochemical detection of Neurogenin 3 expression in mouse and man

During embryonic development, endocrine cells of the pancreas are specified from multipotent progenitors. The transcription factor Neurogenin 3 (NEUROG3) is critical for this development and it has been shown that all endocrine cells of the pancreas arise from endocrine progenitors expressing NEUROG3. A thorough understanding of the role of NEUROG3 during development, directed differentiation of pluripotent stem cells and in models of cellular reprogramming, will guide future efforts directed at finding novel sources of β-cells for cell replacement therapies. In this article, we review the expression and function of NEUROG3 in both mouse and human and present the further characterization of a monoclonal antibody directed against NEUROG3. This antibody has been previously been used for detection of both mouse and human NEUROG3. However, our results suggest that the epitope recognized by this antibody is specific to mouse NEUROG3. Thus, we have also generated a monoclonal antibody specifically recognizing human NEUROG3 and present the characterization of this antibody here. Together, these antibodies will provide useful tools for future studies of NEUROG3 expression, and the data presented in this article suggest that recently described expression patterns of NEUROG3 in human foetal and adult pancreas should be re-examined.

Is Transforming Stem Cells to Pancreatic Beta Cells Still the Holy Grail for Type 2 Diabetes?

Diabetes is a progressive disease affecting millions of people worldwide. There are several medications and treatment options to improve the life quality of people with diabetes. One of the strategies for the treatment of diabetes could be the use of human pluripotent stem cells or induced pluripotent stem cells. The recent advances in differentiation of stem cells into insulin-secreting beta-like cells in vitro make the transplantation of the stem cell-derived beta-like cells an attractive approach for treatment of type 1 and type 2 diabetes. While stem cell-derived beta-like cells provide an unlimited cell source for beta cell replacement therapies, these cells can also be used as a platform for drug screening or modeling diseases.

Genome-edited human stem cell-derived beta cells: a powerful tool for drilling down on type 2 diabetes GWAS biology

Type 2 diabetes (T2D) is a disease of pandemic proportions, one defined by a complex aetiological mix of genetic, epigenetic, environmental, and lifestyle risk factors. Whilst the last decade of T2D genetic research has identified more than 100 loci showing strong statistical association with disease susceptibility, our inability to capitalise upon these signals reflects, in part, a lack of appropriate human cell models for study. This review discusses the impact of two complementary, state-of-the-art technologies on T2D genetic research: the generation of stem cell-derived, endocrine pancreas-lineage cells and the editing of their genomes. Such models facilitate investigation of diabetes-associated genomic perturbations in a physiologically representative cell context and allow the role of both developmental and adult islet dysfunction in T2D pathogenesis to be investigated. Accordingly, we interrogate the role that patient-derived induced pluripotent stem cell models are playing in understanding cellular dysfunction in monogenic diabetes, and how site-specific nucleases such as the clustered regularly interspaced short palindromic repeats (CRISPR)-Cas9 system are helping to confirm genes crucial to human endocrine pancreas development. We also highlight the novel biology gleaned in the absence of patient lines, including an ability to model the whole phenotypic spectrum of diabetes phenotypes occurring both in utero and in adult cells, interrogating the non-coding 'islet regulome' for disease-causing perturbations, and understanding the role of other islet cell types in aberrant glycaemia. This article aims to reinforce the importance of investigating T2D signals in cell models reflecting appropriate species, genomic context, developmental time point, and tissue type.

V-Maf Musculoaponeurotic Fibrosarcoma Oncogene Homolog A Synthetic Modified mRNA Drives Reprogramming of Human Pancreatic Duct-Derived Cells Into Insulin-Secreting Cells

: β-Cell replacement therapy represents the most promising approach to restore β-cell mass and glucose homeostasis in patients with type 1 diabetes. Safety and ethical issues associated with pluripotent stem cells stimulated the search for adult progenitor cells with endocrine differentiation capacities. We have already described a model for expansion and differentiation of human pancreatic duct-derived cells (HDDCs) into insulin-producing cells. Here we show an innovative and robust in vitro system for large-scale production of β-like cells from HDDCs using a nonintegrative RNA-based reprogramming technique. Synthetic modified RNAs for pancreatic transcription factors (pancreatic duodenal homeobox 1, neurogenin3, and V-Maf musculoaponeurotic fibrosarcoma oncogene homolog A [MAFA]) were manufactured and daily transfected in HDDCs without strongly affecting immune response and cell viability. MAFA overexpression was efficient and sufficient to induce β-cell differentiation of HDDCs, which acquired a broad repertoire of mature β-cell markers while downregulating characteristic epithelial-mesenchymal transition markers. Within 7 days, MAFA-reprogrammed HDDC populations contained 37% insulin-positive cells and a proportion of endocrine cells expressing somatostatin and pancreatic polypeptide. Ultrastructure analysis of differentiated HDDCs showed both immature and mature insulin granules with light-backscattering properties. Furthermore, in vitro HDDC-derived β cells (called β-HDDCs) secreted human insulin and C-peptide in response to glucose, KCl, 3-isobutyl-1-methylxanthine, and tolbutamide stimulation. Transplantation of β-HDDCs into diabetic SCID-beige mice confirmed their functional glucose-responsive insulin secretion and their capacity to mitigate hyperglycemia. Our data describe a new, reliable, and fast procedure in adult human pancreatic cells to generate clinically relevant amounts of new β cells with potential to reverse diabetes.

SIGNIFICANCE

β-Cell replacement therapy represents the most promising approach to restore glucose homeostasis in patients with type 1 diabetes. This study shows an innovative and robust in vitro system for large-scale production of β-like cells from human pancreatic duct-derived cells (HDDCs) using a nonintegrative RNA-based reprogramming technique. V-Maf musculoaponeurotic fibrosarcoma oncogene homolog A overexpression was efficient and sufficient to induce β-cell differentiation and insulin secretion from HDDCs in response to glucose stimulation, allowing the cells to mitigate hyperglycemia in diabetic SCID-beige mice. The data describe a new, reliable, and fast procedure in adult human pancreatic cells to generate clinically relevant amounts of new β cells with the potential to reverse diabetes.

Concise Review: Markers for Assessing Human Stem Cell-Derived Implants as β-Cell Replacement in Type 1 Diabetes

: A depleted β-cell mass causes diabetes complications that cannot be avoided by insulin administration. β-Cell replacement can stop their development when restoring insulin's homeostatic role. This requires a sufficient number and an adequate functional state of the β cells, together defined as "functional β-cell mass." Intraportal implants of human pancreatic islet cells correct hyperglycemia in patients with type 1 diabetes, but this effect is transient and often incomplete. Studies to improve outcome are hindered by shortage in donor pancreases. Human pluripotent stem cells are a candidate source for mass production of grafts for β-cell replacement. Their in vitro differentiation to pancreatic endoderm (stage 4) and to β-cell-containing preparations (stage 7) provides grafts that generate β-cell implants in mice. In vivo markers indicated a better outcome of device-encapsulated stage 4 cells and microencapsulated stage 7 cells as compared with nonencapsulated grafts. Encapsulation also offers the advantage of representative implant retrieval for direct analysis by ex vivo markers. Combination of in vitro, in vivo, and ex vivo markers allows comparison of different stem cell-derived grafts and implants, with each other and with clinical islet cell preparations that serve as reference. Data in mice provide insights into the biology of stem cell-generated β-cell implants, in particular their capacity to establish and sustain a functional β-cell mass. They can thus be indicative for translation of a graft to similar studies in patients, where metabolic benefit will be an additional marker of primordial importance.

SIGNIFICANCE

Human stem cell-derived preparations can generate insulin-producing implants in immune-incompetent mice. Steps are undertaken for translation to patients with type 1 diabetes. Their therapeutic significance will depend on their capacity to establish a functional β-cell mass that provides metabolic benefit. This study proposes the combined use of in vitro, in vivo, and ex vivo markers to assess this potential in preclinical models and in clinical studies.

Anterior-Posterior Patterning of Definitive Endoderm Generated from Human Embryonic Stem Cells Depends on the Differential Signaling of Retinoic Acid, Wnt-, and BMP-Signaling

As known from model organisms, such as frog, fish, mouse, and chicken, the anterior-posterior patterning of the definitive endoderm (DE) into distinct domains is controlled by a variety of signaling interactions between the DE and its surrounding mesoderm. This includes Wnt/FGFs and BMPs in the posterior half and all-trans-retinoic acid, TGF-β-ligands, Wnt-, and BMP-inhibitors in the anterior half of the DE sheet. However, it is currently unclear how these embryonic tissue interactions can be translated into a defined differentiation protocol for human embryonic stem cells. Activin A has been proposed to direct DE into a SOX2-positive foregut-like cell type. Due to the pleiotropic nature of SOX2 in pluripotency and developing cells of the foregut, we purified DE-cells by magnetic cell sorting and tested the effects of anteriorizing and posteriorizing factors on pure endoderm. We show in contrast to previous studies that the generation of the foregut marked by SOX2/FOXA2 double-positive cells does not depend on activin A/TGF-β-signaling but is mediated by the inhibition of Wnt- and BMP-signaling. Retinoic acid can posteriorize and at the same time dorsalize the foregut toward a PDX1-positive pancreatic duodenal cell type whereas active Wnt/beta-catenin signaling synergistically with FGF-2, BMP-4, and RA induces the formation of CDX2-positive posterior endoderm. Thus, these results provide new insights into the mechanisms behind cell specification of human DE derived from pluripotent stem cells. Stem Cells 2016;34:2635-2647.