Production of functional glucagon-secreting α-cells from human embryonic stem cells

New opportunities: harnessing induced pluripotency for discovery in diabetes and metabolism

The landmark discovery of induced pluripotent stem cells (iPSCs) by Shinya Yamanaka has transformed regenerative biology. Previously, insights into the pathogenesis of chronic human diseases have been hindered by the inaccessibility of patient samples. However, scientists are now able to convert patient fibroblasts into iPSCs and differentiate them into disease-relevant cell types. This ability opens new avenues for investigating disease pathogenesis and designing novel treatments. In this review, we highlight the uses of human iPSCs to uncover the underlying causes and pathological consequences of diabetes and metabolic syndromes, multifactorial diseases whose etiologies have been difficult to unravel using traditional methodologies.

Characterization of polyhormonal insulin-producing cells derived in vitro from human embryonic stem cells

Human embryonic stem cells (hESCs) were used as a model system of human pancreas development to study characteristics of the polyhormonal cells that arise during fetal pancreas development. HESCs were differentiated into fetal-like pancreatic cells in vitro using a 33-day, 7-stage protocol. Cultures were ~90-95% PDX1-positive by day (d) 11 and 70-75% NKX6.1-positive by d17. Polyhormonal cells were scattered at d17, but developed into islet-like clusters that expressed key transcription factors by d33. Human C-peptide and glucagon secretion were first detected at d17 and increased thereafter in parallel with INS and GCG transcript levels. HESC-derived cells were responsive to KCl and arginine, but not glucose in perifusion studies. Compared to adult human islets, hESC-derived cells expressed ~10-fold higher levels of glucose transporter 1 (GLUT1) mRNA, but similar levels of glucokinase (GCK). In situ hybridization confirmed the presence of GLUT1 transcript within endocrine cells. However, GLUT1 protein was excluded from this population and was instead observed predominantly in non-endocrine cells, whereas GCK was co-expressed in insulin-positive cells. In rubidium efflux assays, hESC-derived cells displayed mild potassium channel activity, but no responsiveness to glucose, metabolic inhibitors or glibenclamide. Western blotting experiments revealed that the higher molecular weight SUR1 band was absent in hESC-derived cells, suggesting a lack of functional KATP channels at the cell surface. In addition, KATP channel subunit transcript levels were not at a 1:1 ratio, as would be expected (SUR1 levels were ~5-fold lower than KIR6.2). Various ratios of SUR1:KIR6.2 plasmids were transfected into COSM6 cells and rubidium efflux was found to be particularly sensitive to a reduction in SUR1. These data suggest that an impaired ratio of SUR1:KIR6.2 may contribute to the observed KATP channel defects in hESC-derived islet endocrine cells, and along with lack of GLUT1, may explain the absence of glucose-stimulated insulin secretion.

Making β cells from adult cells within the pancreas

Cell therapy is currently considered as a potential therapeutic alternative to traditional treatments of diabetes. Islet and whole pancreas transplantations provided the proof-of-concept of glucose homeostasis restoration after replenishment of the deficiency of β cells responsible for the disease. Current limitations of these procedures have led to the search for strategies targeting replication of pre-existing β cells or transdifferentiation of progenitors and adult cells. These investigations revealed an unexpected plasticity towards β cells of adult cells residing in pancreatic epithelium (eg, acinar, duct, and α cells). Here we discuss recent developments in β-cell replication and β-cell transdifferentiation of adult epithelial pancreatic cells, with an emphasis on techniques with a potential for clinical translation.

Maturation and function of human embryonic stem cell-derived pancreatic progenitors in macroencapsulation devices following transplant into mice

AIMS/HYPOTHESIS

Islet transplantation is a promising cell therapy for patients with diabetes, but it is currently limited by the reliance upon cadaveric donor tissue. We previously demonstrated that human embryonic stem cell (hESC)-derived pancreatic progenitor cells matured under the kidney capsule in a mouse model of diabetes into glucose-responsive insulin-secreting cells capable of reversing diabetes. However, the formation of cells resembling bone and cartilage was a major limitation of that study. Therefore, we developed an improved differentiation protocol that aimed to prevent the formation of off-target mesoderm tissue following transplantation. We also examined how variation within the complex host environment influenced the development of pancreatic progenitors in vivo.

METHODS

The hESCs were differentiated for 14 days into pancreatic progenitor cells and transplanted either under the kidney capsule or within Theracyte (TheraCyte, Laguna Hills, CA, USA) devices into diabetic mice.

RESULTS

Our revised differentiation protocol successfully eliminated the formation of non-endodermal cell populations in 99% of transplanted mice and generated grafts containing >80% endocrine cells. Progenitor cells developed efficiently into pancreatic endocrine tissue within macroencapsulation devices, despite lacking direct contact with the host environment, and reversed diabetes within 3 months. The preparation of cell aggregates pre-transplant was critical for the formation of insulin-producing cells in vivo and endocrine cell development was accelerated within a diabetic host environment compared with healthy mice. Neither insulin nor exendin-4 therapy post-transplant affected the maturation of macroencapsulated cells.

CONCLUSIONS/INTERPRETATION

Efficient differentiation of hESC-derived pancreatic endocrine cells can occur in a macroencapsulation device, yielding glucose-responsive insulin-producing cells capable of reversing diabetes.

Phenotypic and functional characterization of glucagon-positive cells derived from spontaneous differentiation of D3-mouse embryonic stem cells

BACKGROUND

Glucagon expression is being considered as a definitive endoderm marker in protocols aiming to obtain insulin-secreting cells from embryonic stem cells. However, it should be considered that in vivo glucagon is expressed both in definitive endoderm- and neuroectoderm-derived cells. Therefore, the true nature and function of in vitro spontaneously differentiated glucagon-positive cells remains to be established.

METHODS

D3 and R1 mouse embryonic stem cells as well as α-TC1-9 cells were cultured and glucagon expression was determined by real-time PCR and immunocytochemistry. Functional analyses regarding intracellular calcium oscillations were performed to further characterize glucagon(+) cells.

RESULTS

Specifically, 5% of D3 and R1 cells expressed preproglucagon, with a small percentage of these (<1%) expressing glucagon-like peptide 1. The constitutive expression of protein convertase 5 supports the expression of both peptides. Glucagon(+) cells co-expressed neurofilament middle and some glucagon-like peptide-1(+) cells, glial fibrillary acidic protein, indicating a neuroectodermic origin. However, few glucagon-like peptide-1(+) cells did not show coexpression with glial fibrillary acidic protein, suggesting a non-neuroectodermic origin for these cells. Finally, glucagon(+) cells did not display Ca(2+) oscillations typical of pancreatic α-cells.

DISCUSSION

These results indicate the possible nondefinitive endodermal origin of glucagon-positive cells spontaneously differentiated from D3 and R1 cell lines, as well as the presence of cells expressing glucagon-like peptide-1 from two different origins.

Suppression of epithelial-to-mesenchymal transitioning enhances ex vivo reprogramming of human exocrine pancreatic tissue toward functional insulin-producing β-like cells

Because of the lack of tissue available for islet transplantation, new sources of β-cells have been sought for the treatment of type 1 diabetes. The aim of this study was to determine whether the human exocrine-enriched fraction from the islet isolation procedure could be reprogrammed to provide additional islet tissue for transplantation. The exocrine-enriched cells rapidly dedifferentiated in culture and grew as a mesenchymal monolayer. Genetic lineage tracing confirmed that these mesenchymal cells arose, in part, through a process of epithelial-to-mesenchymal transitioning (EMT). A protocol was developed whereby transduction of these mesenchymal cells with adenoviruses containing Pdx1, Ngn3, MafA, and Pax4 generated a population of cells that were enriched in glucagon-secreting α-like cells. Transdifferentiation or reprogramming toward insulin-secreting β-cells was enhanced, however, when using unpassaged cells in combination with inhibition of EMT by inclusion of Rho-associated kinase (ROCK) and transforming growth factor-β1 inhibitors. Resultant cells were able to secrete insulin in response to glucose and on transplantation were able to normalize blood glucose levels in streptozotocin diabetic NOD/SCID mice. In conclusion, reprogramming of human exocrine-enriched tissue can be best achieved using fresh material under conditions whereby EMT is inhibited, rather than allowing the culture to expand as a mesenchymal monolayer.

Alternative functional in vitro models of human intestinal epithelia

Physiologically relevant sources of absorptive intestinal epithelial cells are crucial for human drug transport studies. Human adenocarcinoma-derived intestinal cell lines, such as Caco-2, offer conveniences of easy culture maintenance and scalability, but do not fully recapitulate in vivo intestinal phenotypes. Additional sources of renewable physiologically relevant human intestinal cells would provide a much needed tool for drug discovery and intestinal physiology. We compared two alternative sources of human intestinal cells, commercially available primary human intestinal epithelial cells (hInEpCs) and induced pluripotent stem cell (iPSC)-derived intestinal cells to Caco-2, for use in in vitro transwell monolayer intestinal transport assays. To achieve this for iPSC-derived cells, intestinal organogenesis was adapted to transwell differentiation. Intestinal cells were assessed by marker expression through immunocytochemical and mRNA expression analyses, monolayer integrity through Transepithelial Electrical Resistance (TEER) measurements and molecule permeability, and functionality by taking advantage the well-characterized intestinal transport mechanisms. In most cases, marker expression for primary hInEpCs and iPSC-derived cells appeared to be as good as or better than Caco-2. Furthermore, transwell monolayers exhibited high TEER with low permeability. Primary hInEpCs showed molecule efflux indicative of P-glycoprotein (Pgp) transport. Primary hInEpCs and iPSC-derived cells also showed neonatal Fc receptor-dependent binding of immunoglobulin G variants. Primary hInEpCs and iPSC-derived intestinal cells exhibit expected marker expression and demonstrate basic functional monolayer formation, similar to or better than Caco-2. These cells could offer an alternative source of human intestinal cells for understanding normal intestinal epithelial physiology and drug transport.

Penny wise and pound foolish: will shortsighted cost reduction measures compromise patient access to promising self-monitoring of blood glucose technology?

In this issue of Journal of Diabetes Science and Technology, Grady and coauthors enrolled 101 patients with type 1 and type 2 diabetes to evaluate new technology incorporated into the LifeScan VerioPro and VerioIQ blood glucose meters. The "pattern detection" software provides real-time, onscreen messages that alert users to patterns of high glucose (fasting and premeal) and low glucose as they are detected. The study showed that most participants possess a good understanding of the factors that can cause hyperglycemia; however, their understanding of the causes of hypoglycemia events was not as strong. Nevertheless, more than 70% of participants indicated they preferred to use a blood glucose meter that provides pattern detection capability. Although not designed to assess the impact of the pattern detection tool on clinical outcomes, the study highlights the value of continuous innovation in self-monitoring of blood glucose (SMBG) technology among manufacturers. Unfortunately, many patients may never have access to these systems due to reductions in Medicare reimbursement. Instead, they may be forced to use SMBG systems that are inaccurate and provide inadequate patient support. Stronger regulatory requirements are needed to ensure that all SMBG systems marketed to patients are accurate, reliable, and supported by adequate patient training, and current health care reimbursement policies should be restructured to encourage manufacturers to continue their efforts to develop innovative technology to further improve the utility and usability of their SMBG systems.

Reprogramming adult human dermal fibroblasts to islet-like cells by epigenetic modification coupled to transcription factor modulation

In this article, we describe novel conditions for culture, expansion, and transdifferentiation of primary human dermal fibroblasts (hDFs) to induce expression of transcription factors (TFs) and hormones characteristic of the islets of Langerhans. We show that histones associated with the insulin gene are hyperacetylated and that insulin gene DNA is less methylated in islet cells compared to cells that do not express insulin. Using two compounds that alter the epigenetic signature of cells, romidepsin (Romi), a histone deacetylase inhibitor, and 5-Azacytidine (5-AzC), a chemical analogue of cytidine that cannot be methylated, we show that hDFs exhibit a distinctive regulation of expression of TFs involved in islet development as well as of induction of glucagon and insulin. Overexpression of Pdx1, a TF important for islet differentiation, and silencing of musculoaponeurotic fibrosarcoma oncogene homolog B, a TF that is expressed in mature glucagon-producing cells, result in induction of insulin to a higher level compared to Romi and 5-AzC alone. The cells obtained from this protocol exhibit glucose-stimulated insulin secretion and lower blood glucose levels of diabetic mice. These data show that fully differentiated nonislet-derived cells could be made to transdifferentiate to islet-like cells and that combining epigenetic modulation with TF modulation leads to enhanced insulin expression.

Factors expressed by murine embryonic pancreatic mesenchyme enhance generation of insulin-producing cells from hESCs

Islet transplantation has proven to be a successful strategy to restore normoglycemia in patients with type 1 diabetes (T1D). However, the dearth of cadaveric islets available for transplantation hampers the widespread application of this treatment option. Although human embryonic stem cells and induced pluripotent stem cells are capable of generating insulin-producing cells in vitro when provided with the appropriate inductive cues, the insulin-expressing cells that develop behave more like immature β-cells with minimal sensitivity to glucose stimulation. Here, we identify a set of signaling factors expressed in mouse embryonic mesenchyme during the time when foregut and pancreatic progenitors are specified and test their activities during in vitro differentiation of human embryonic stem cells. Several of the identified factors work in concert to expand the pancreatic progenitor pool. Interestingly, transforming growth factor (TGF)-β ligands, most potent in inducing pancreatic progenitors, display strong inhibitory effects on subsequent endocrine cell differentiation. Treatment with TGF-β ligands, followed by the addition of a TGF-β receptor antagonist, dramatically increased the number of insulin-producing cells in vitro, demonstrating the need for dynamic temporal regulation of TGF-β signaling during in vitro differentiation. These studies illustrate the need to precisely mimic the in vivo conditions to fully recapitulate pancreatic lineage specification in vitro.

A simple tool to improve pluripotent stem cell differentiation

We develop a method to overcome previously documented restrictions on the differentiation propensities of pluripotent stem cells. Culturing pluripotent stem cells in dimethylsulfoxide (DMSO) activates the retinoblastoma protein, increases the proportion of cells in the early G1 phase of the cell cycle, and subsequently improves their competency for directed differentiation into multiple lineages in more than 25 stem cell lines. DMSO treatment also promotes terminal differentiation into functional derivatives.

Generating β-cells in vitro: progress towards a Holy Grail

PURPOSE OF REVIEW

Diabetes is a debilitating disease characterized by a chronic inability to normalize blood glucose levels. Transplanting cadaveric pancreata or isolated pancreatic islets can restore glucose homeostasis, but organ demand outstrips supply. Consequently, there is significant interest in alternative tissue sources. This review summarizes state-of-the-art efforts to generate scalable, functional β-cells to treat diabetes.

RECENT FINDINGS

Applying knowledge gleaned from developmental biology, human pluripotent stem cells can be treated stepwise with combinations of small molecules, developmentally relevant growth factors, and morphogens to generate pancreatic progenitor cells (PPCs) in vitro. Transplanted PPCs can then further mature in vivo into functional islet-like tissues containing all of the endocrine hormone cells present in adult islets and can reverse hyperglycemia in a diabetic animal model. Recent publications demonstrate that skin, liver, and other cell lineages may also be reprogrammed to functional β-like cells.

SUMMARY

Although generation of fully functional β-cells in vitro has not yet been achieved, possible intermediate approaches to treat diabetes include using PPCs or reprogramming adult cells to β-like cells. A cell therapy with either approach will require isolation from the host immune response. Ongoing efforts are addressing this need through the use of immune-isolation devices to avoid immunosuppressive drugs.

Human pluripotent stem cells: an emerging model in developmental biology

Developmental biology has long benefited from studies of classic model organisms. Recently, human pluripotent stem cells (hPSCs), including human embryonic stem cells and human induced pluripotent stem cells, have emerged as a new model system that offers unique advantages for developmental studies. Here, we discuss how studies of hPSCs can complement classic approaches using model organisms, and how hPSCs can be used to recapitulate aspects of human embryonic development 'in a dish'. We also summarize some of the recently developed genetic tools that greatly facilitate the interrogation of gene function during hPSC differentiation. With the development of high-throughput screening technologies, hPSCs have the potential to revolutionize gene discovery in mammalian development.

Functional evaluation of ES cell-derived endodermal populations reveals differences between Nodal and Activin A-guided differentiation

Embryonic stem (ES) cells hold great promise with respect to their potential to be differentiated into desired cell types. Of interest are organs derived from the definitive endoderm, such as the pancreas and liver, and animal studies have revealed an essential role for Nodal in development of the definitive endoderm. Activin A is a related TGFβ member that acts through many of the same downstream signaling effectors as Nodal and is thought to mimic Nodal activity. Detailed characterization of ES cell-derived endodermal cell types by gene expression analysis in vitro and functional analysis in vivo reveal that, despite their similarity in gene expression, Nodal and Activin-derived endodermal cells exhibit a distinct difference in functional competence following transplantation into the developing mouse embryo. Pdx1-expressing cells arising from the respective endoderm populations exhibit extended differences in their competence to mature into insulin/c-peptide-expressing cells in vivo. Our findings underscore the importance of functional cell-type evaluation during stepwise differentiation of stem cells.

Alpha cells come of age

The alpha cells that coinhabit the islets with the insulin-producing beta cells have recently captured the attention of diabetes researchers because of new breakthrough findings highlighting the importance of these cells in the maintenance of beta cell health and functions. In normal physiological conditions alpha cells produce glucagon but in conditions of beta cell injury they also produce glucagon-like peptide-1 (GLP-1), a growth and survival factor for beta cells. In this review we consider these new findings on the functions of alpha cells. Alpha cells remain somewhat enigmatic inasmuch as they now appear to be important in the maintenance of the health of beta cells, but their production of glucagon promotes diabetes. This circumstance prompts an examination of approaches to coax alpha cells to produce GLP-1 instead of glucagon.

Endodermal stem cell populations derived from pluripotent stem cells

The generation of functional endodermal lineages, such as hepatocytes and pancreatic endocrine cells, from pluripotent stem cells (PSCs) remains a challenge. One strategy to enhance the purity, yield and maturity of endodermal derivatives is to expand endoderm committed stem or progenitor cell populations derived from PSCs before final differentiation. Recent studies have shown that this is in fact a viable option both for expanding pure populations of endodermal cells as well as for generating more mature derivative tissues, as highlighted in the case of pancreatic beta cells.

Small-molecule inhibitors of the cystic fibrosis transmembrane conductance regulator increase pancreatic endocrine cell development in rat and mouse

AIMS/HYPOTHESIS

The main objective of this work was to discover new drugs that can activate the differentiation of multipotent pancreatic progenitors into endocrine cells.

METHODS

In vitro experiments were performed using fetal pancreatic explants from rats and mice. In this assay, we examined the actions on pancreatic cell development of glibenclamide, a sulfonylurea derivative, and glycine hydrazide (GlyH-101), a small-molecule inhibitor of cystic fibrosis transmembrane conductance regulator (CFTR). We next tested the actions of GlyH-101 on in vivo pancreatic cell development.

RESULTS

Glibenclamide (10 nmol/l-100 μmol/l) did not alter the morphology or growth of the developing pancreas and exerted no deleterious effects on exocrine cell development in the pancreas. Unexpectedly, glibenclamide at its highest concentration promoted endocrine differentiation. This glibenclamide-induced promotion of the endocrine pathway could not be reproduced when other sulfonylureas were used, suggesting that glibenclamide had an off-target action. This high concentration of glibenclamide had previously been reported to inhibit CFTR. We found that the effects of glibenclamide on the developing pancreas could be mimicked both in vitro and in vivo by GlyH-101.

CONCLUSIONS/INTERPRETATION

Collectively, we demonstrate that two small-molecule inhibitors of the CFTR, glibenclamide and GlyH-101, increase the number of pancreatic endocrine cells by increasing the size of the pool of neurogenin 3-positive endocrine progenitors in the developing pancreas.

Cell transplantation therapy for diabetes mellitus: endocrine pancreas and adipocyte

Experimental transplantation of endocrine tissues has led to significant advances in our understanding of endocrinology and metabolism. Endocrine cell transplantation therapy is expected to be applied to the treatment of metabolic endocriopathies. Restoration of functional pancreatic beta-cell mass or of functional adipose mass are reasonable treatment approaches for patients with diabetes or lipodystrophy, respectively. Human induced pluripotent stem (iPS) cell research is having a great impact on life sciences. Doctors Takahashi and Yamanaka discovered that the forced expression of a set of genes can convert mouse and human somatic cells into a pluripotent state [1, 2]. These iPS cells can differentiate into a variety of cell types. Therefore, iPS cells from patients may be a potential cell source for autologous cell replacement therapy. This review briefly summarizes the current knowledge about transplantation therapy for diabetes mellitus, the development of the endocrine pancreas and adipocytes, and endocrine-metabolic disease-specific iPS cells.

Urocortin 3 marks mature human primary and embryonic stem cell-derived pancreatic alpha and beta cells

The peptide hormone Urocortin 3 (Ucn 3) is abundantly and exclusively expressed in mouse pancreatic beta cells where it regulates insulin secretion. Here we demonstrate that Ucn 3 first appears at embryonic day (E) 17.5 and, from approximately postnatal day (p) 7 and onwards throughout adult life, becomes a unifying and exclusive feature of mouse beta cells. These observations identify Ucn 3 as a potential beta cell maturation marker. To determine whether Ucn 3 is similarly restricted to beta cells in humans, we conducted comprehensive immunohistochemistry and gene expression experiments on macaque and human pancreas and sorted primary human islet cells. This revealed that Ucn 3 is not restricted to the beta cell lineage in primates, but is also expressed in alpha cells. To substantiate these findings, we analyzed human embryonic stem cell (hESC)-derived pancreatic endoderm that differentiates into mature endocrine cells upon engraftment in mice. Ucn 3 expression in hESC-derived grafts increased robustly upon differentiation into mature endocrine cells and localized to both alpha and beta cells. Collectively, these observations confirm that Ucn 3 is expressed in adult beta cells in both mouse and human and appears late in beta cell differentiation. Expression of Pdx1, Nkx6.1 and PC1/3 in hESC-derived Ucn 3⁺ beta cells supports this. However, the expression of Ucn 3 in primary and hESC-derived alpha cells demonstrates that human Ucn 3 is not exclusive to the beta cell lineage but is a general marker for both the alpha and beta cell lineages. Ucn 3⁺ hESC-derived alpha cells do not express Nkx6.1, Pdx1 or PC1/3 in agreement with the presence of a separate population of Ucn 3⁺ alpha cells. Our study highlights important species differences in Ucn 3 expression, which have implications for its utility as a marker to identify mature beta cells in (re)programming strategies.

Restoring insulin production for type 1 diabetes

Current therapies for the treatment of type 1 diabetes include daily administration of exogenous insulin and, less frequently, whole-pancreas or islet transplantation. Insulin injections often result in inaccurate insulin doses, exposing the patient to hypo- and/or hyperglycemic episodes that lead to long-term complications. Islet transplantation is also limited by lack of high-quality islet donors, early graft failure, and chronic post-transplant immunosuppressive treatment. These barriers could be circumvented by designing a safe and efficient strategy to restore insulin production within the patient's body. Porcine islets have been considered as a possible alternative source of transplantable insulin-producing cells to replace human cadaveric islets. More recently, embryonic or induced pluripotent stem cells have also been examined for their ability to differentiate in vitro into pancreatic endocrine cells. Alternatively, it may be feasible to generate new β-cells by ectopic expression of key transcription factors in endogenous non-β-cells. Finally, engineering surrogate β-cells by in vivo delivery of the insulin gene to specific tissues is also being studied as a possible therapy for type 1 diabetes. In the present review, we discuss these different approaches to restore insulin production.

Self-renewal of embryonic-stem-cell-derived progenitors by organ-matched mesenchyme

One goal of regenerative medicine, to use stem cells to replace cells lost by injury or disease, depends on producing an excess of the relevant cell for study or transplantation. To this end, the stepwise differentiation of stem cells into specialized derivatives has been successful for some cell types, but a major problem remains the inefficient conversion of cells from one stage of differentiation to the next. If specialized cells are to be produced in large numbers it will be necessary to expand progenitor cells, without differentiation, at some steps of the process. Using the pancreatic lineage as a model for embryonic-stem-cell differentiation, we demonstrate that this is a solvable problem. Co-culture with organ-matched mesenchyme permits proliferation and self-renewal of progenitors, without differentiation, and enables an expansion of more than a million-fold for human endodermal cells with full retention of their developmental potential. This effect is specific both to the mesenchymal cell and to the progenitor being amplified. Progenitors that have been serially expanded on mesenchyme give rise to glucose-sensing, insulin-secreting cells when transplanted in vivo. Theoretically, the identification of stage-specific renewal signals can be incorporated into any scheme for the efficient production of large numbers of differentiated cells from stem cells and may therefore have wide application in regenerative biology.

Characterization of myelomonocytoid progenitor cells with mesenchymal differentiation potential obtained by outgrowth from pancreas explants

Progenitor cells can be obtained by outgrowth from tissue explants during primary ex vivo tissue culture. We have isolated and characterized cells outgrown from neonatal mouse pancreatic explants. A relatively uniform population of cells showing a distinctive morphology emerged over time in culture. This population expressed monocyte/macrophage and hematopoietic markers (CD11b(+) and CD45(+)), and some stromal-related markers (CD44(+) and CD29(+)), but not mesenchymal stem cell (MSC)-defining markers (CD90(-) and CD105(-)) nor endothelial (CD31(-)) or stem cell-associated markers (CD133(-) and stem cell antigen-1; Sca-1(-)). Cells could be maintained in culture as a plastic-adherent monolayer in culture medium (MesenCult MSC) for more than 1 year. Cells spontaneously formed sphere clusters "pancreatospheres" which, however, were nonclonal. When cultured in appropriate media, cells differentiated into multiple mesenchymal lineages (fat, cartilage, and bone). Positive dithizone staining suggested that a subset of cells differentiated into insulin-producing cells. However, further studies are needed to characterize the endocrine potential of these cells. These findings indicate that a myelomonocytoid population from pancreatic explant outgrowths has mesenchymal differentiation potential. These results are in line with recent data onmonocyte-derivedmesenchymal progenitors (MOMPs).

Generation of beta cells from human pluripotent stem cells: Potential for regenerative medicine

The loss of beta cells in Type I diabetes ultimately leads to insulin dependence and major complications that are difficult to manage by insulin injections. Given the complications associated with long-term administration of insulin, cell-replacement therapy is now under consideration as an alternative treatment that may someday provide a cure for this disease. Over the past 10 years, islet transplantation trials have demonstrated that it is possible to replenish beta cell function in Type I diabetes patients and, at least temporarily, eliminate their dependency on insulin. While not yet optimal, the success of these trials has provided proof-of-principle that cell replacement therapy is a viable option for treating diabetes. Limited access to donor islets has launched a search for alternative source of beta cells for cell therapy purposes and focused the efforts of many investigators on the challenge of deriving such cells from human embryonic (hESCs) and induced pluripotent stem cells (hiPSCs). Over the past five years, significant advances have been made in understanding the signaling pathways that control lineage development from human pluripotent stem cells (hPSCs) and as a consequence, it is now possible to routinely generate insulin producing cells from both hESCs and hiPSCs. While these achievements are impressive, significant challenges do still exist, as the majority of insulin producing cells generated under these conditions are polyhormonal and non functional, likely reflecting the emergence of the polyhormonal population that is known to arise in the early embryo during the phase of pancreatic development known as the 'first transition'. Functional beta cells, which arise during the second phase or transition of pancreatic development have been generated from hESCs, however they are detected only following transplantation of progenitor stage cells into immunocompromised mice. With this success, our challenge now is to define the pathways that control the development and maturation of this second transition population from hPSCs, and establish conditions for the generation of functional beta cells in vitro.

Maturation of human embryonic stem cell-derived pancreatic progenitors into functional islets capable of treating pre-existing diabetes in mice

Diabetes is a chronic debilitating disease that results from insufficient production of insulin from pancreatic β-cells. Islet cell replacement can effectively treat diabetes but is currently severely limited by the reliance upon cadaveric donor tissue. We have developed a protocol to efficiently differentiate commercially available human embryonic stem cells (hESCs) in vitro into a highly enriched PDX1+ pancreatic progenitor cell population that further develops in vivo to mature pancreatic endocrine cells. Immature pancreatic precursor cells were transplanted into immunodeficient mice with streptozotocin-induced diabetes, and glycemia was initially controlled with exogenous insulin. As graft-derived insulin levels increased over time, diabetic mice were weaned from exogenous insulin and human C-peptide secretion was eventually regulated by meal and glucose challenges. Similar differentiation of pancreatic precursor cells was observed after transplant in immunodeficient rats. Throughout the in vivo maturation period hESC-derived endocrine cells exhibited gene and protein expression profiles that were remarkably similar to the developing human fetal pancreas. Our findings support the feasibility of using differentiated hESCs as an alternative to cadaveric islets for treating patients with diabetes.

Self-renewing endodermal progenitor lines generated from human pluripotent stem cells

The use of human pluripotent stem cells for laboratory studies and cell-based therapies is hampered by their tumor-forming potential and limited ability to generate pure populations of differentiated cell types in vitro. To address these issues, we established endodermal progenitor (EP) cell lines from human embryonic and induced pluripotent stem cells. Optimized growth conditions were established that allow near unlimited (>10(16)) EP cell self-renewal in which they display a morphology and gene expression pattern characteristic of definitive endoderm. Upon manipulation of their culture conditions in vitro or transplantation into mice, clonally derived EP cells differentiate into numerous endodermal lineages, including monohormonal glucose-responsive pancreatic β-cells, hepatocytes, and intestinal epithelia. Importantly, EP cells are nontumorigenic in vivo. Thus, EP cells represent a powerful tool to study endoderm specification and offer a potentially safe source of endodermal-derived tissues for transplantation therapies.

Making β cells from adult tissues

β-Cell replacement represents an attractive prospect for diabetes therapy. Although much hope has been placed on derivation of insulin-producing cells from human pluripotent stem cells, this approach continues to face considerable challenges. Cells from adult human tissues, with both stem/progenitor and mature phenotypes, offer a possible alternative. This review summarizes recent progress in two major strategies based on this cell source, ex vivo expansion of human islet β cells and conversion of non-β cells into insulin-producing cells by nuclear reprogramming, and examines the obstacles that remain to be overcome for bringing these strategies closer to clinical application in diabetes therapy.

A scalable system for production of functional pancreatic progenitors from human embryonic stem cells

Development of a human embryonic stem cell (hESC)-based therapy for type 1 diabetes will require the translation of proof-of-principle concepts into a scalable, controlled, and regulated cell manufacturing process. We have previously demonstrated that hESC can be directed to differentiate into pancreatic progenitors that mature into functional glucose-responsive, insulin-secreting cells in vivo. In this study we describe hESC expansion and banking methods and a suspension-based differentiation system, which together underpin an integrated scalable manufacturing process for producing pancreatic progenitors. This system has been optimized for the CyT49 cell line. Accordingly, qualified large-scale single-cell master and working cGMP cell banks of CyT49 have been generated to provide a virtually unlimited starting resource for manufacturing. Upon thaw from these banks, we expanded CyT49 for two weeks in an adherent culture format that achieves 50–100 fold expansion per week. Undifferentiated CyT49 were then aggregated into clusters in dynamic rotational suspension culture, followed by differentiation en masse for two weeks with a four-stage protocol. Numerous scaled differentiation runs generated reproducible and defined population compositions highly enriched for pancreatic cell lineages, as shown by examining mRNA expression at each stage of differentiation and flow cytometry of the final population. Islet-like tissue containing glucose-responsive, insulin-secreting cells was generated upon implantation into mice. By four- to five-months post-engraftment, mature neo-pancreatic tissue was sufficient to protect against streptozotocin (STZ)-induced hyperglycemia. In summary, we have developed a tractable manufacturing process for the generation of functional pancreatic progenitors from hESC on a scale amenable to clinical entry.

Preparation of pancreatic β-cells from human iPS cells with small molecules

Human induced pluripotent stem (iPS) cells obtained from patients are expected to be a useful source for cell transplantation therapy, because many patients (including those with type 1 diabetes and severe type 2 diabetes) are on waiting lists for transplantation for a long time due to the shortage of donors. At present, many concerns related to clinical application of human iPS cells have been raised, but rapid development of methods for the establishment, culture, and standardization of iPS cells will lead autologous cell therapy to be realistic sooner or later. However, establishment of a method for preparing some of desired cell types is still challenging. Regarding pancreatic β-cells, there have been many reports about differentiation of these cells from human embryonic stem (ES)/iPS cells, but a protocol for clinical application has still not been established. Since there is clear proof that cell transplantation therapy is effective for diabetes based on the results of clinical islet transplantation, pancreatic β-cells prepared from human iPS cells are considered likely to be effective for reducing the burden on patients. In this article, the current status of procedures for preparing pancreatic β-cells from human ES/iPS cells, including effective use of small molecules, is summarized, and some of the problems that still need to be overcome are discussed.

α-cell role in β-cell generation and regeneration

This review considers the role of α-cells in β-cell generation and regeneration. We present recent evidence obtained from lineage-tracing studies showing that α-cells can serve as progenitors of β-cells and present a hypothetical model how injured β-cells might activate α-cells in adult islets to promote β-cell regeneration. β-cells appear to arise by way of their trans-differentiation from undifferentiated α progenitor cells, pro-α-cells, both during embryonic development of the islets and in the adult pancreas in response to β-cell injuries. Plasticity of α-cells is endowed by the expression of the gene encoding proglucagon, a prohormone that can give rise to glucagon and glucagon-like peptides (GLPs). The production of glucagon from proglucagon is characteristic of fully-differentiated α-cells whereas GLP-1 is a product of undifferentiated α-cells. GLP-1, a cell growth and survival factor, is proposed to promote the expansion of neurogenin3-expressing, undifferentiated pro-α-cells during development. β-cells arise from pro-α-cells by a change in the relative amounts of the transcription factors Arx and Pax4, master regulators of the α- and β-cell lineages, respectively. A paracrine/autocrine model is proposed whereby injuries of β-cells in adult islets induce the production and release of factors, such as stromal cell-derived factor-1, that cause the de-differentiation of adjacent α-cells into pro-α-cells. Pro-α-cells produce GLP-1 and its receptor that renders them competent to trans-differentiate into β-cells. The trans-differentiation of pro-α-cells into β-cells provides a potentially exploitable mechanism for the regeneration of β-cells in individuals with type 1 diabetes.

β-cell preservation and regeneration for diabetes treatment: where are we now?

Over the last decade, our knowledge of β-cell biology has expanded with the use of new scientific techniques and strategies. Growth factors, hormones and small molecules have been shown to enhance β-cell proliferation and function. Stem cell technology and research into the developmental biology of the pancreas have yielded new methods for in vivo and in vitro regeneration of β cells from stem cells and endogenous progenitors as well as transdifferentiation of non-β cells. Novel pharmacological approaches have been developed to preserve and enhance β-cell function. Strategies to increase expression of insulin gene transcription factors in dysfunctional and immature β cells have ameliorated these impairments. Hence, we suggest that strategies to minimize β-cell loss and to increase their function and regeneration will ultimately lead to therapy for both Type 1 and 2 diabetes.

Functional beta-cell maturation is marked by an increased glucose threshold and by expression of urocortin 3

Insulin-expressing cells that have been differentiated from human pluripotent stem cells in vitro lack the glucose responsiveness characteristic of mature beta cells. Beta-cell maturation in mice was studied to find genetic markers that enable screens for factors that induce bona fide beta cells in vitro. We find that functional beta-cell maturation is marked by an increase in the glucose threshold for insulin secretion and by expression of the gene urocortin 3.

Immunohistochemical characterisation of cells co-producing insulin and glucagon in the developing human pancreas

AIMS/HYPOTHESIS

In adult human islets, insulin and glucagon production is largely restricted to individual cell populations. The production of these hormones is less segregated during development and during the differentiation of human pluripotent stem cells towards pancreatic lineages. We therefore sought to characterise the transcription factor profile of these cells that co-produce insulin and glucagon in the developing human pancreas, and thus to gain insight into their potential fate during normal pancreas development.

METHODS

An immunohistochemical analysis was performed on human pancreas sections from fetal donors aged 9 to 21 weeks and from adult donors between the ages of 17 and 55 years.

RESULTS

Endocrine cells were observed within the pancreas at all ages examined, with cells co-producing insulin and glucagon observed as early as 9 weeks of fetal age. The population of cells that co-produce insulin and glucagon generally decreased in prevalence with age, with negligible numbers in adult pancreas. From 9 to 16 weeks, the population of glucagon-only cells increased, while the insulin-only cells decreased in abundance. Cells that co-produced insulin and glucagon also produced the alpha cell transcription factor, aristaless related homeobox (ARX), and lacked the beta cell transcription factors pancreatic and duodenal homeobox 1 (PDX1), NK6 homeobox 1 (NKX6.1) and v-maf musculoaponeurotic fibrosarcoma oncogene homologue A (MAFA).

CONCLUSIONS/INTERPRETATION

Our results indicate that cells co-producing insulin and glucagon in the developing human pancreas share a transcription factor profile that is similar to that of mature alpha cells and suggest that some maturing alpha cells briefly exhibit ectopic insulin expression. Thus cells that co-produce insulin and glucagon may represent a transient cell population, which gives rise to mature alpha cells.

The functional and molecular characterisation of human embryonic stem cell-derived insulin-positive cells compared with adult pancreatic beta cells

AIMS/HYPOTHESIS

Using a novel directed differentiation protocol, we recently generated up to 25% insulin-producing cells from human embryonic stem cells (hESCs) (insulin(+) cells). At this juncture, it was important to functionally and molecularly characterise these hESC-derived insulin(+) cells and identify key differences and similarities between them and primary beta cells.

METHODS

We used a new reporter hESC line with green fluorescent protein (GFP) cDNA targeted to the INS locus by homologous recombination (INS (GFP/w)) and an untargeted hESC line (HES2). INS (GFP/w) allowed efficient identification and purification of GFP-producing (INS:GFP(+)) cells. Insulin(+) cells were examined for key features of adult beta cells using microarray, quantitative PCR, secretion assays, imaging and electrophysiology.

RESULTS

Immunofluorescent staining showed complete co-localisation of insulin with GFP; however, cells were often multihormonal, many with granules containing insulin and glucagon. Electrophysiological recordings revealed variable K(ATP) and voltage-gated Ca(2+) channel activity, and reduced glucose-induced cytosolic Ca(2+) uptake. This translated into defective glucose-stimulated insulin secretion but, intriguingly, appropriate glucagon responses. Gene profiling revealed differences in global gene expression between INS:GFP(+) cells and adult human islets; however, INS:GFP(+) cells had remarkably similar expression of endocrine-lineage transcription factors and genes involved in glucose sensing and exocytosis.

CONCLUSIONS/INTERPRETATION

INS:GFP(+) cells can be purified from differentiated hESCs, providing a superior source of insulin-producing cells. Genomic analyses revealed that INS:GFP(+) cells collectively resemble immature endocrine cells. However, insulin(+) cells were heterogeneous, a fact that translated into important functional differences within this population. The information gained from this study may now be used to generate new iterations of functioning beta cells that can be purified for transplant.

Concise review: pancreas regeneration: recent advances and perspectives

The replacement of functional pancreatic β-cells is seen as an attractive potential therapy for diabetes, because diabetes results from an inadequate β-cell mass. Inducing replication of the remaining β-cells and new islet formation from progenitors within the pancreas (neogenesis) are the most direct ways to increase the β-cell mass. Stimulation of both replication and neogenesis have been reported in rodents, but their clinical significance must still be shown. Because human islet transplantation is limited by the scarcity of donors and graft failure within a few years, efforts have recently concentrated on the use of stem cells to replace the deficient β-cells. Currently, embryonic stem cells and induced pluripotent stem cells achieve high levels of β-cell differentiation, but their clinical use is still hampered by ethical issues and/or the risk of developing tumors after transplantation. Pancreatic epithelial cells (duct, acinar, or α-cells) represent an appealing alternative to stem cells because they demonstrate β-cell differentiation capacities. Yet translation of such capacity to human cells after significant in vitro expansion has yet to be achieved. Besides providing new β-cells, cell therapy also has to address the question on how to protect the transplanted cells from destruction by the immune system via either allo- or autoimmunity. Encouraging developments have been made in encapsulation and immunomodulation techniques, but many challenges still remain. Herein, we discuss recent advances in the search for β-cell replacement therapies, current strategies for circumventing the immune system, and mandatory steps for new techniques to be translated from bench to clinics.

Musashi expression in β-cells coordinates insulin expression, apoptosis and proliferation in response to endoplasmic reticulum stress in diabetes

Diabetes is associated with the death and dysfunction of insulin-producing pancreatic β-cells. In other systems, Musashi genes regulate cell fate via Notch signaling, which we recently showed regulates β-cell survival. Here we show for the first time that human and mouse adult islet cells express mRNA and protein of both Musashi isoforms, as well Numb/Notch/Hes/neurogenin-3 pathway components. Musashi expression was observed in insulin/glucagon double-positive cells during human fetal development and increased during directed differentiation of human embryonic stem cells (hESCs) to the pancreatic lineage. De-differentiation of β-cells with activin A increased Msi1 expression. Endoplasmic reticulum (ER) stress increased Msi2 and Hes1, while it decreased Ins1 and Ins2 expression, revealing a molecular link between ER stress and β-cell dedifferentiation in type 2 diabetes. These effects were independent of changes in Numb protein levels and Notch activation. Overexpression of MSI1 was sufficient to increase Hes1, stimulate proliferation, inhibit apoptosis and reduce insulin expression, whereas Msi1 knockdown had the converse effects on proliferation and insulin expression. Overexpression of MSI2 resulted in a decrease in MSI1 expression. Taken together, these results demonstrate overlapping, but distinct roles for Musashi-1 and Musashi-2 in the control of insulin expression and β-cell proliferation. Our data also suggest that Musashi is a novel link between ER stress and the compensatory β-cell proliferation and the loss of β-cell gene expression seen in specific phases of the progression to type 2 diabetes.

Small molecules induce efficient differentiation into insulin-producing cells from human induced pluripotent stem cells

Human induced pluripotent stem (hiPS) cells have potential uses for drug discovery and cell therapy, including generation of pancreatic β-cells for diabetes research and treatment. In this study, we developed a simple protocol for generating insulin-producing cells from hiPS cells. Treatment with activin A and a GSK3β inhibitor enhanced efficient endodermal differentiation, and then combined treatment with retinoic acid, a bone morphogenic protein inhibitor, and a transforming growth factor-β (TGF-β) inhibitor induced efficient differentiation of pancreatic progenitor cells from definitive endoderm. Expression of the pancreatic progenitor markers PDX1 and NGN3 was significantly increased at this step and most cells were positive for anti-PDX1 antibody. Moreover, several compounds, including forskolin, dexamethasone, and a TGF-β inhibitor, were found to induce the differentiation of insulin-producing cells from pancreatic progenitor cells. By combined treatment with these compounds, more than 10% of the cells became insulin positive. The differentiated cells secreted human c-peptide in response to various insulin secretagogues. In addition, all five hiPS cell lines that we examined showed efficient differentiation into insulin-producing cells with this protocol.

Potential pathways to restore β-cell mass: pluripotent stem cells, reprogramming, and endogenous regeneration

Currently available β-cell replacement therapies for patients with diabetes, including islet and pancreas transplantation, are largely successful in restoring normal glucose metabolism, but the scarcity of organ donors restricts their more widespread use. To solve this supply problem, several different strategies for achieving β-cell mass restoration are being pursued. These include the generation of β cells from stem cells and their subsequent transplantation, or regeneration-type approaches, such as stimulating endogenous regenerative mechanisms or inducing reprogramming of non-β cells into β cells. Because these strategies would ultimately generate allogeneic or syngeneic β cells in humans, the control of alloimmunity and/or autoimmunity in addition to replacing lost β cells will be of utmost importance. We briefly review the recent literature on these three promising strategies toward β-cell replacement or restoration and point out the major issues impacting their translation to treating human diabetes.

Generation of pancreatic insulin-producing cells from rhesus monkey induced pluripotent stem cells

AIMS/HYPOTHESIS

The generation of induced pluripotent stem cells (iPSCs) provides a promising possibility for type 1 diabetes therapy. However, the generation of insulin-producing cells from iPSCs and evaluation of their efficacy and safety should be achieved in large animals before clinically applying iPSC-derived cells in humans. Here we try to generate insulin-producing cells from rhesus monkey (RM) iPSCs.

METHODS

Based on the knowledge of embryonic pancreatic development, we developed a four-stage protocol to generate insulin-producing cells from RM iPSCs. We established a quantitative method using flow cytometry to analyse the differentiation efficiency. In addition, to evaluate the differentiation competence and function of RM iPSC-derived cells, transplantation of stage 3 and 4 cells into immunodeficient mice was performed.

RESULTS

RM iPSCs were sequentially induced to definitive endoderm (DE), pancreatic progenitors (PP), endocrine precursors (EP) and insulin-producing cells. PDX1(+) PP cells were obtained efficiently from RM iPSCs (over 85% efficiency). The TGF-β inhibitor SB431542 promoted the generation of NGN3(+) EP cells, which can generate insulin-producing cells in vivo upon transplantation. Finally, after this four-stage differentiation in vitro, insulin-producing cells that could secrete insulin in response to glucose stimulation were obtained. When transplanted into mouse models for diabetes, these insulin-producing cells could decrease blood glucose levels in approximately 50% of the mice.

CONCLUSIONS/INTERPRETATION

We demonstrate for the first time that RM iPSCs can be differentiated into functional insulin-producing cells, which will provide the basis for investigating the efficacy and safety of autologous iPSC-derived insulin-producing cells in a rhesus monkey model for type 1 diabetes therapy.

Inhibitors of Src and focal adhesion kinase promote endocrine specification: impact on the derivation of β-cells from human pluripotent stem cells

Stepwise approaches for the derivation of β-cells from human embryonic stem cells have been described. However, low levels of endocrine specification limit the final yield of insulin-producing β-cells. In this study, we show that the pyrrolo-pyrimidine Src family kinase (SFK) inhibitor PP2 effectively promotes the endocrine specification of human embryonic stem cell derivatives based on its capacity to induce the expression of proendocrine transcription factors (NGN3, NEUROD1, NKX2.2, and PAX4) and to significantly increase the final yield of insulin-positive cells. We further demonstrate that PP2 inhibits the activation of focal adhesion kinase (FAK), and selective inhibition of this kinase is also sufficient to induce early endocrine commitment based on increased expression of NGN3, NEUROD1, and NKX2.2. Additional studies using dominant negative constructs and isolated human fetal pancreata suggest that c-Src is at least partially responsible for inhibiting early endocrine specification. Mechanistically, we propose that inhibition of SFK/FAK signaling can promote endocrine specification by limiting activation of the TGFβR/Smad2/3 pathway. Moreover, we show that inhibition of SFK/FAK signaling suppresses cell growth, increases the expression of the β-cell-associated cyclin-dependent kinase inhibitor p57kip2, and simultaneously suppresses the expression of Id1 and Id2. This study has important implications for the derivation of β-cells for the cell-based therapy of diabetes and sheds new light on the signaling events that regulate early endocrine specification.

Activin, BMP and FGF pathways cooperate to promote endoderm and pancreatic lineage cell differentiation from human embryonic stem cells

The study of how human embryonic stem cells (hESCs) differentiate into insulin-producing beta cells has twofold significance: first, it provides an in vitro model system for the study of human pancreatic development, and second, it serves as a platform for the ultimate production of beta cells for transplantation into patients with diabetes. The delineation of growth factor interactions regulating pancreas specification from hESCs in vitro is critical to achieving these goals. In this study, we describe the roles of growth factors bFGF, BMP4 and Activin A in early hESC fate determination. The entire differentiation process is carried out in serum-free chemically-defined media (CDM) and results in reliable and robust induction of pancreatic endoderm cells, marked by PDX1, and cell clusters co-expressing markers characteristic of beta cells, including PDX1 and insulin/C-peptide. Varying the combinations of growth factors, we found that treatment of hESCs with bFGF, Activin A and BMP4 (FAB) together for 3-4days resulted in strong induction of primitive-streak and definitive endoderm-associated genes, including MIXL1, GSC, SOX17 and FOXA2. Early proliferative foregut endoderm and pancreatic lineage cells marked by PDX1, FOXA2 and SOX9 expression are specified in EBs made from FAB-treated hESCs, but not from Activin A alone treated cells. Our results suggest that important tissue interactions occur in EB-based suspension culture that contribute to the complete induction of definitive endoderm and pancreas progenitors. Further differentiation occurs after EBs are embedded in Matrigel and cultured in serum-free media containing insulin, transferrin, selenium, FGF7, nicotinamide, islet neogenesis associated peptide (INGAP) and exendin-4, a long acting GLP-1 agonist. 21-28days after embedding, PDX1 gene expression levels are comparable to those of human islets used for transplantation, and many PDX1(+) clusters are formed. Almost all cells in PDX1(+) clusters co-express FOXA2, HNF1ß, HNF6 and SOX9 proteins, and many cells also express CPA1, NKX6.1 and PTF1a. If cells are then switched to medium containing B27 and nicotinamide for 7-14days, then the number of insulin(+) cells increases markedly. Our study identifies a new chemically defined culture protocol for inducing endoderm- and pancreas-committed cells from hESCs and reveals an interplay between FGF, Activin A and BMP signaling in early hESC fate determination.

Cell-surface markers for the isolation of pancreatic cell types derived from human embryonic stem cells

Using a flow cytometry-based screen of commercial antibodies, we have identified cell-surface markers for the separation of pancreatic cell types derived from human embryonic stem (hES) cells. We show enrichment of pancreatic endoderm cells using CD142 and of endocrine cells using CD200 and CD318. After transplantation into mice, enriched pancreatic endoderm cells give rise to all the pancreatic lineages, including functional insulin-producing cells, demonstrating that they are pancreatic progenitors. In contrast, implanted, enriched polyhormonal endocrine cells principally give rise to glucagon cells. These antibodies will aid investigations that use pancreatic cells generated from pluripotent stem cells to study diabetes and pancreas biology.

Stem cell-based approaches for the treatment of diabetes

The incidence of diabetes and the associated debilitating complications are increasing at an alarming rate worldwide. Current therapies for type 1 diabetes focus primarily on administration of exogenous insulin to help restore glucose homeostasis. However, such treatment rarely prevents the long-term complications of this serious metabolic disorder, including neuropathy, nephropathy, retinopathy, and cardiovascular disease. Whole pancreas or islet transplantations have enjoyed limited success in some individuals, but these approaches are hampered by the shortage of suitable donors and the burden of lifelong immunosuppression. Here, we review current approaches to differentiate nonislet cell types towards an islet-cell phenotype which may be used for larger-scale cell replacement strategies. In particular, the differentiation protocols used to direct embryonic stem cells, progenitor cells of both endocrine and nonendocrine origin, and induced pluripotent stem cells towards an islet-cell phenotype are discussed.

Stage-specific signaling through TGFβ family members and WNT regulates patterning and pancreatic specification of human pluripotent stem cells

The generation of insulin-producing β-cells from human pluripotent stem cells is dependent on efficient endoderm induction and appropriate patterning and specification of this germ layer to a pancreatic fate. In this study, we elucidated the temporal requirements for TGFβ family members and canonical WNT signaling at these developmental stages and show that the duration of nodal/activin A signaling plays a pivotal role in establishing an appropriate definitive endoderm population for specification to the pancreatic lineage. WNT signaling was found to induce a posterior endoderm fate and at optimal concentrations enhanced the development of pancreatic lineage cells. Inhibition of the BMP signaling pathway at specific stages was essential for the generation of insulin-expressing cells and the extent of BMP inhibition required varied widely among the cell lines tested. Optimal stage-specific manipulation of these pathways resulted in a striking 250-fold increase in the levels of insulin expression and yielded populations containing up to 25% C-peptide+ cells.

Stage-specific signaling through TGFβ family members and WNT regulates patterning and pancreatic specification of human pluripotent stem cells

The generation of insulin-producing β-cells from human pluripotent stem cells is dependent on efficient endoderm induction and appropriate patterning and specification of this germ layer to a pancreatic fate. In this study, we elucidated the temporal requirements for TGFβ family members and canonical WNT signaling at these developmental stages and show that the duration of nodal/activin A signaling plays a pivotal role in establishing an appropriate definitive endoderm population for specification to the pancreatic lineage. WNT signaling was found to induce a posterior endoderm fate and at optimal concentrations enhanced the development of pancreatic lineage cells. Inhibition of the BMP signaling pathway at specific stages was essential for the generation of insulin-expressing cells and the extent of BMP inhibition required varied widely among the cell lines tested. Optimal stage-specific manipulation of these pathways resulted in a striking 250-fold increase in the levels of insulin expression and yielded populations containing up to 25% C-peptide+ cells.