Transplantation of human embryonic stem cell-derived pancreatic endoderm reveals a site-specific survival, growth, and differentiation

Humanized Mouse Models for Evaluation of PSC Immunogenicity

New human pluripotent stem cell (hPSC)-derived therapies are advancing to clinical trials at an increasingly rapid pace. In addition to ensuring that the therapies function properly, there is a critical need to investigate the human immune response to these cell products. A robust allogeneic (or autologous) immune response could swiftly eliminate an otherwise promising cell therapy, even in immunosuppressed patients. In coming years, researchers in the regenerative medicine field will need to utilize a number of in vitro and in vivo assays and models to evaluate and better understand hPSC immunogenicity. Humanized mouse models-mice engrafted with functional human immune cell types-are an important research tool for investigating the mechanisms of the adaptive immune response to hPSC therapies. This article provides an overview of humanized mouse models relevant to the study of hPSC immunogenicity and explores central considerations for investigators seeking to utilize these powerful models in their research. © 2020 Wiley Periodicals LLC.

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.

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

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

Safety and Efficacy of Epigenetically Converted Human Fibroblasts Into Insulin-Secreting Cells: A Preclinical Study

Type 1 Diabetes Mellitus (T1DM) is a chronic disease that leads to loss of insulin secreting β-cells, causing high levels of blood glucose. Exogenous insulin administration is not sufficient to mimic the normal function of β-cells and, consequently, diabetes mellitus often progresses and can lead to major chronic complications and morbidity. The physiological control of glucose levels can only be restored by replacing the β-cell mass.We recently developed a new strategy that allows for epigenetic conversion of dermal fibroblasts into insulin-secreting cells (EpiCC), using a brief exposure to the demethylating agent 5-aza-cytidine (5-aza-CR), followed by a pancreatic induction protocol. This method has notable advantages compared to the alternative available procedures and may represent a promising tool for clinical translation as a therapy for T1DM. However, a thought evaluation of its therapeutic safety and efficacy is mandatory to support preclinical studies based on EpiCC treatment.We here report the data obtained using human fibroblasts isolated from diabetic and healthy individuals, belonging the two genders. EpiCC were injected into 650 diabetic severe combined immunodeficiency (SCID) mice and demonstrated to be able to restore and maintain glycemic levels within the physiological range. Cells had the ability to self-regulate and not to cause hypoglycemia, when transplanted in healthy animals. Efficacy tests showed that EpiCC successfully re-established normoglycemia in diabetic mice, using a dose range that appeared clinically relevant to the concentration 0.6 × 10⁶ EpiCC. Necropsy and histopathological investigations demonstrated the absence of malignant transformation and cell migration to organs and lymph nodes.The present preclinical study demonstrates safety and efficacy of human EpiCC in diabetic mice and supports the use of epigenetic converted cells for regenerative medicine of diabetes mellitus.

Implications of human induced pluripotent stem cells in metabolic disorders: from drug discovery toward precision medicine

Human induced pluripotent stem cells (hiPSCs) enable in vitro high-throughput pharmacological screening assays of diseased tissue. Together with recent genome-wide association studies (GWAS), hiPSCs enable the identification of key mutations for the development of effective treatments based on precise drugs. In concert with CRISPR/Cas9 systems, hiPSC technology can reveal therapeutic targets in metabolic disorders. The ex vivo CRISPR correction of autologous patient-derived hiPSCs has led to the development of replacement cell therapies, providing better patient prognoses.

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

β-Cells derived from stem cells hold great promise for cell replacement therapy for diabetes. Here we examine the ability of nuclear transfer embryonic stem cells (NT-ESs) derived from a patient with type 1 diabetes to differentiate into β-cells and provide a source of autologous islets for cell replacement. NT-ESs differentiate in vitro with an average efficiency of 55% into C-peptide-positive cells, expressing markers of mature β-cells, including MAFA and NKX6.1. Upon transplantation in immunodeficient mice, grafted cells form vascularized islet-like structures containing MAFA/C-peptide-positive cells. These β-cells adapt insulin secretion to ambient metabolite status and show normal insulin processing. Importantly, NT-ES-β-cells maintain normal blood glucose levels after ablation of the mouse endogenous β-cells. Cystic structures, but no teratomas, were observed in NT-ES-β-cell grafts. Isogenic induced pluripotent stem cell lines showed greater variability in β-cell differentiation. Even though different methods of somatic cell reprogramming result in stem cell lines that are molecularly indistinguishable, full differentiation competence is more common in ES cell lines than in induced pluripotent stem cell lines. These results demonstrate the suitability of NT-ES-β-cells for cell replacement for type 1 diabetes and provide proof of principle for therapeutic cloning combined with cell therapy.

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.

Cell Viability of Human Embryonic Stem Cells Stored for a Period of 9 Years

OBJECTIVES

Human embryonic stem cells are pluripotent cell lines usually derived from human blastocysts. Their potential critically depends on long-term proliferative capacity, developmental potential after prolonged culture, and karyotypic stability. Cell viability is an important parameter for assessing cell sample quality. Here, we elaborate the stored human embryonic stem cell lines' viability in a ready to use form for a period of 9 years (from 2007 to 2015).

MATERIALS AND METHODS

Spare pre implantation stage in vitro fertilized ovum-derived cell lines were cultured in suitable media. Thereafter, they were centrifuged at 1000 revolutions/min over 5 minutes, and pellets were suspended in normal saline. Next, they were tested for viability from storage at -20°C. After being allowed to thaw slowly, the cells were stained with propidium iodide and analyzed using flow cytometry. Images of cells were taken at ×40 and ×100 magnification.

RESULTS

At ×100 magnification, cell population size ranged from 0.2 to 2 μm. The percentage of live cells was more than 95% throughout the 9 years. Cells frozen in 2015 showed cell viability of 96.8%.

CONCLUSIONS

We observed high cell viability in our cell lines for 9 years. Human embryonic stem cell lines in a ready-to-use form can be preserved for long-term purposes. Thus, they could be made available globally.

Capsule stiffness regulates the efficiency of pancreatic differentiation of human embryonic stem cells

Encapsulation of donor islets using a hydrogel material is a well-studied strategy for islet transplantation, which protects donor islets from the host immune response. Replacement of donor islets by human embryonic stem cell (hESC) derived islets will also require a means of immune-isolating hESCs by encapsulation. However, a critical consideration of hESC differentiation is the effect of surrounding biophysical environment, in this case capsule biophysical properties, on differentiation. The objective of this study, thus, was to evaluate the effect of capsule properties on growth, viability, and differentiation of encapsulated hESCs throughout pancreatic induction. It was observed that even in the presence of soluble chemical cues for pancreatic induction, substrate properties can significantly modulate pancreatic differentiation, hence necessitating careful tuning of capsule properties. Capsules in the range of 4-7kPa supported cell growth and viability, whereas capsules of higher stiffness suppressed cell growth. While an increase in capsule stiffness enhanced differentiation at the intermediate definitive endoderm (DE) stage, increased stiffness strongly suppressed pancreatic progenitor (PP) induction. Signaling pathway analysis indicated an increase in pSMAD/pAKT levels with substrate stiffness likely the cause of enhancement of DE differentiation. In contrast, sonic hedgehog inhibition was more efficient under softer gel conditions, which is necessary for successful PP differentiation.

STATEMENT OF SIGNIFICANCE

Cell replacement therapy for type 1 diabetes (T1D), affecting millions of people worldwide, requires the immunoisolation of insulin-producing islets by encapsulation with a semi-impermeable material. Due to the shortage of donor islets, human pluripotent stem cell (hPSC) derived islets are an attractive alternative. However, properties of the encapsulating substrate are known to influence hPSC cell fate. In this work, we determine the effect of substrate stiffness on growth and pancreatic fate of encapsulated hPSCs. We precisely identify the range of substrate properties conducive for pancreatic cell fate, and also the mechanism by which substrate properties modify the cell signaling pathways and hence cell fate. Such information will be critical in driving regenerative cell therapy for long term treatment of T1D.

Role of BMP signaling in pancreatic progenitor differentiation from human embryonic stem cells

Transplantation of pancreatic progenitors derived from human embryonic stem cells (hESCs) is a promising way to treat diabetes. Strategies to obtain the required cell mass would rely on the up scaling of current differentiation protocols, or the proliferation of committed progenitors. We aimed at finding conditions that maintain a proliferating pancreatic progenitor pool and we assessed the role of BMP4 signaling in this process. hESCs were differentiated into PDX1 positive pancreatic progenitor stage following our established protocol with few modifications, and then the progenitor cells were passaged in a defined proliferation medium (PM). During passage, the effect of BMP4 signaling on the differentiation and proliferation of pancreatic progenitors was examined by RT-PCR and immunofluorescence analysis. We found that PDX1 positive pancreatic progenitors proliferated and gained NKX6.1 expression in the PM, whereas they failed to express NKX6.1 if BMP signaling was inhibited with Noggin. In this latter condition, part of the progenitors rather generated pro-endocrine cells denoted by NGN3 and synaptophysin expression. On the contrary, addition of BMP4 to the PM promoted the early derivation of PDX1 and NKX6.1 coexpressing pancreatic progenitors. Our findings are in line with mouse pancreas development, and indicate that BMP4 signaling is required for the derivation and maintenance of hESC-derived PDX1+NKX6.1+ pancreatic progenitors. These results are instructive for guiding the development of an efficient pancreas differentiation protocol in view of diabetes cell replacement therapy.

Cellular reprogramming for pancreatic β-cell regeneration: clinical potential of small molecule control

Recent scientific breakthroughs in stem cell biology suggest that a sustainable treatment approach to cure diabetes mellitus (DM) can be achieved in the near future. However, the transplantation complexities and the difficulty in obtaining the stem cells from adult cells of pancreas, liver, bone morrow and other cells is a major concern. The epoch-making strategy of transcription-factor based cellular reprogramming suggest that these barriers could be overcome, and it is possible to reprogram any cells into functional β cells. Contemporary biological and analytical techniques help us to predict the key transcription factors needed for β-cell regeneration. These β cell-specific transcription factors could be modulated with diverse reprogramming protocols. Among cellular reprogramming strategies, small molecule approach gets proclaimed to have better clinical prospects because it does not involve genetic manipulation. Several small molecules targeting certain epigenetic enzymes and/or signaling pathways have been successful in helping to induce pancreatic β-cell specification. Recently, a synthetic DNA-based small molecule triggered targeted transcriptional activation of pancreas-related genes to suggest the possibility of achieving desired cellular phenotype in a precise mode. Here, we give a brief overview of treating DM by regenerating pancreatic β-cells from various cell sources. Through a comprehensive overview of the available transcription factors, small molecules and reprogramming strategies available for pancreatic β-cell regeneration, this review compiles the current progress made towards the generation of clinically relevant insulin-producing β-cells.

Efficient definitive endoderm induction from mouse embryonic stem cell adherent cultures: a rapid screening model for differentiation studies

Definitive endoderm (DE) differentiation from mouse embryonic stem cell (mESC) monolayer cultures has been limited by poor cell survival or low efficiency. Recently, a combination of TGFβ and Wnt activation with BMP inhibition improved DE induction in embryoid bodies cultured in suspension. Based on these observations we developed a protocol to efficiently induce DE cells in monolayer cultures of mESCs. We obtained a good cell yield with 54.92% DE induction as shown by Foxa2, Sox17, Cxcr4 and E-Cadherin expression. These DE-cells could be further differentiated into posterior foregut and pancreatic phenotypes using a culture protocol initially developed for human embryonic stem cell (hESC) differentiation. In addition, this mESC-derived DE gave rise to hepatocyte-like cells after exposure to BMP and FGF ligands. Our data therefore indicate a substantial improvement of monolayer DE induction from mESCs and support the concept that differentiation conditions for mESC-derived DE are similar to those for hESCs. As mESCs are easier to maintain and manipulate in culture compared to hESCs, and considering the shorter duration of embryonic development in the mouse, this method of efficient DE induction on monolayer will promote the development of new differentiation protocols to obtain DE-derivatives, like pancreatic beta-cells, for future use in cell replacement therapies.

The use of stem cells for pancreatic regeneration in diabetes mellitus

The endocrine pancreas represents an interesting arena for regenerative medicine and cell therapeutics. One of the major pancreatic diseases, diabetes mellitus is a metabolic disorder caused by having an insufficient number of insulin-producing β cells. Replenishment of β cells by cell transplantation can restore normal metabolic control. The shortage in donor pancreata has meant that the demand for transplantable β cells has outstripped the supply, which could be met by using alternative sources of stem cells. This situation has opened up new areas of research, such as cellular reprogramming and in vivo β-cell regeneration. Pluripotent stem cells seem to be the best option for clinical applications of β-cell regeneration in the near future, as these cells have been demonstrated to represent an unlimited source of functional β cells. Although compelling evidence shows that the adult pancreas retains regenerative capacity, it remains unclear whether this organ contains stem cells. Alternatively, specialized cell types within or outside the pancreas retain plasticity in proliferation and differentiation. Cellular reprogramming or transdifferentiation of exocrine cells or other types of endocrine cells in the pancreas could provide a long-term solution.

[Differentiation of pluripotent stem cells into pancreatic lineages]

Diabetes mellitus is the leading metabolic disease and represents a major public health concern worldwide. Whereas the transplantation of pancreas donor-derived islets significantly improves the quality of life of diabetic patients who become insulin independent for few years, it can unfortunately be provided only to few patients in an advanced stage of the disease. This situation is related to the severe shortage in pancreas donors and has prompted the hunt for alternative sources of islet cells. Beside many other strategies aiming at producing new beta cells in vitro or in vivo, a particular focus has been on the plupiropent stem cells because of their abundant availability and their extreme plasticity. Progress in understanding small vertebrates embryonic development has tremendously contributed to the design of differentiation strategies applied to pluripotent stem cells. Nowadays, definitive endoderm and pancreatic progenitors can be efficiently induced from human embryonic stem cells and from human induced pluripotent stem cells. Although we are still lacking the knowledge required for deriving functional beta cells in vitro, transplantation experiments have demonstrated that stem cell-derived pancreas progenitors further generate this phenotype in vivo. All these findings gathered during the last decade witness the closer clinical application of pluripotent stem cell progenies in diabetes cell therapy.

Stem cells as a tool to improve outcomes of islet transplantation

The publication of the promising results of the Edmonton protocol in 2000 generated optimism for islet transplantation as a potential cure for Type 1 Diabetes Mellitus. Unfortunately, follow-up data revealed that less than 10% of patients achieved long-term insulin independence. More recent data from other large trials like the Collaborative Islet Transplant Registry show incremental improvement with 44% of islet transplant recipients maintaining insulin independence at three years of follow-up. Multiple underlying issues have been identified that contribute to islet graft failure, and newer research has attempted to address these problems. Stem cells have been utilized not only as a functional replacement for β cells, but also as companion or supportive cells to address a variety of different obstacles that prevent ideal graft viability and function. In this paper, we outline the manners in which stem cells have been applied to address barriers to the achievement of long-term insulin independence following islet transplantation.