Production of beta-cells from human embryonic stem cells

Islets in the body are never flat: transitioning from two-dimensional (2D) monolayer culture to three-dimensional (3D) spheroid for better efficiency in the generation of functional hPSC-derived pancreatic β cells in vitro

Diabetes mellitus (DM), currently affecting more than 537 million people worldwide is a chronic disease characterized by impaired glucose metabolism resulting from a defect in insulin secretion, action, or both due to the loss or dysfunction of pancreatic β cells. Since cadaveric islet transplantation using Edmonton protocol has served as an effective intervention to restore normoglycaemia in T1D patients for months, stem cell-derived β cells have been explored for cell replacement therapy for diabetes. Thus, great effort has been concentrated by scientists on developing in vitro differentiation protocols to realize the therapeutic potential of hPSC-derived β cells. However, most of the 2D traditional monolayer culture could mainly generate insulin-producing β cells with immature phenotype. In the body, pancreatic islets are 3D cell arrangements with complex cell-cell and cell-ECM interactions. Therefore, it is important to consider the spatial organization of the cell in the culture environment. More recently, 3D cell culture platforms have emerged as powerful tools with huge translational potential, particularly for stem cell research. 3D protocols provide a better model to recapitulate not only the in vivo morphology, but also the cell connectivity, polarity, and gene expression mimicking more physiologically the in vivo cell niche. Therefore, the 3D culture constitutes a more relevant model that may help to fill the gap between in vitro and in vivo models. Interestingly, most of the 2D planar methodologies that successfully generated functional hPSC-derived β cells have switched to a 3D arrangement of cells from pancreatic progenitor stage either as suspension clusters or as aggregates, suggesting the effect of 3D on β cell functionality. In this review we highlight the role of dimensionality (2D vs 3D) on the differentiation efficiency for generation of hPSC-derived insulin-producing β cells in vitro. Consequently, how transitioning from 2D monolayer culture to 3D spheroid would provide a better model for an efficient generation of fully functional hPSC-derived β cells mimicking in vivo islet niche for diabetes therapy or drug screening. Video Abstract.

Comparative study of three types of mesenchymal stem cell to differentiate into pancreatic β-like cells in vitro

Type 1 diabetes (TID) is a chronic metabolic disease where the body produces insufficient or no insulin. Stem cells with multi-directional differentiation potential are transplanted and differentiate into β-like cells in vivo to replace pancreatic β cells, which has become a novel treatment strategy. The aim of the present study was to investigate the ability of three types of adult mesenchymal stem cell (MSC) to differentiate into pancreatic β-like cells in vitro in order to identify suitable sources for the treatment of diabetes. The three MSC types were menstrual blood-derived MSCs (MENSCs), umbilical cord-derived MSCs (UCMSCs) and dental pulp MSCs (DPSCs). The differentiation method used in the present study was divided into three steps and the MSCs were differentiated into pancreatic β-like cells in vitro. Among these MSCs, MENSCs had a greater ability to differentiate into islet β-like cells in vitro, while UCMSCs and DPSCs exhibited a similar differentiation potency, which was relatively lower compared with that of MENSCs. The present results indicated that MENSCs may be a suitable cell source for the curative treatment of TID.

Advances and complications of regenerative medicine in diabetes therapy

The rapid development of technologies in regenerative medicine indicates clearly that their common application is not a matter of if, but of when. However, the regeneration of beta-cells for diabetes patients remains a complex challenge due to the plurality of related problems. Indeed, the generation of beta-cells masses expressing marker genes is only a first step, with maintaining permanent insulin secretion, their protection from the immune system and avoiding pathological modifications in the genome being the necessary next developments. The prospects of regenerative medicine in diabetes therapy were promoted by the emergence of promising results with embryonic stem cells (ESCs). Their pluripotency and proliferation in an undifferentiated state during culture have ensured the success of ESCs in regenerative medicine. The discovery of induced pluripotent stem cells (iPSCs) derived from the patients’ own mesenchymal cells has provided further hope for diabetes treatment. Nonetheless, the use of stem cells has significant limitations related to the pluripotent stage, such as the risk of development of teratomas. Thus, the direct conversion of mature cells into beta-cells could address this issue. Recent studies have shown the possibility of such transdifferentiation and have set trends for regeneration medicine, directed at minimizing genome modifications and invasive procedures. In this review, we will discuss the published results of beta-cell regeneration and the advantages and disadvantages illustrated by these experiments.

Electrospun Nanofibers for Diabetes: Tissue Engineering and Cell-Based Therapies

Diabetes mellitus is an autoimmune disease which causes loss of insulin secretion producing hyperglycemia by promoting progressive destruction of pancreatic β cells. An ideal therapeutic approach to manage diabetes mellitus is pancreatic β cells replacement. The aim of this review article was to evaluate the role of nanofibrous scaffolds and stem cells in the treatment of diabetes mellitus. Various studies have pointed out that application of electrospun biomaterials has considerably attracted researchers in the field of tissue engineering. The principles of cell therapy for diabetes have been reviewed in the first part of this article, while the usability of tissue engineering as a new therapeutic approach is discussed in the second part.

Safety and efficacy of hematopoietic and mesanchymal stem cell therapy for treatment of T1DM: a systematic review and meta-analysis protocol

INTRODUCTION

Insulin standard treatment of T1DM cannot cure the patients as different chronic complications occurred subsequently. Investigations on a curative treatment in T1DM propose cell replacement or maintenance instead of exogenous insulin therapy, but different dimensions of this novel treatment are not clarified.

METHODS AND ANALYSIS

We will include all clinical trials which have evaluated the efficacy MSC or HSC transplantation in T1DM treatment; electronically search bibliographic databases, country registration data banks, and gray literatures; and hand-search two key journals, two experts' article, and references of the included articles with no language restriction. Primary outcome is the extent of reduction in insulin requirement and secondary outcomes are safety of MSC and HSC therapy, effect of this therapy on diabetic parameters, effect of the rout of transplantation and origin of the MSC or HSC on efficacy of treatment, studies heterogeneity and potential reasons of it. Heterogeneity and its severity will be calculated with Q Cochrane test, P value, and I2 index. STATA software version 12 will be used for meta-analysis. PROSPERO Registration number: CRD42016047176.

ETHICS AND DISSEMINATION

We will publish the systematic review in a peer review journal; as it presents an analysis of published literature, the study does not require ethical approval.

STRENGTHS AND LIMITATIONS OF THIS STUDY

This systematic review and meta-analysis will investigate the efficacy of MSC and HSC transplantation in T1DM treatment with no language restriction. Also we will evaluate gray literatures after hand searching. This protocol is prepared according to Preferred Reporting Items for Systematic Review and Meta-Analysis Protocols (PRISMA-P). Two reviewers will evaluate screened full texts, extract data, and asses risk of bias of eligible primary studies independently. As there is the possibility that we miss some unpublished primary studies due to negative results, we will use funnel plot to detect this and correct it with fill and trim method.

Distinct and Shared Determinants of Cardiomyocyte Contractility in Multi-Lineage Competent Ethnically Diverse Human iPSCs

The realization of personalized medicine through human induced pluripotent stem cell (iPSC) technology can be advanced by transcriptomics, epigenomics, and bioinformatics that inform on genetic pathways directing tissue development and function. When possible, population diversity should be included in new studies as resources become available. Previously we derived replicate iPSC lines of African American, Hispanic-Latino and Asian self-designated ethnically diverse (ED) origins with normal karyotype, verified teratoma formation, pluripotency biomarkers, and tri-lineage in vitro commitment. Here we perform bioinformatics of RNA-Seq and ChIP-seq pluripotency data sets for two replicate Asian and Hispanic-Latino ED-iPSC lines that reveal differences in generation of contractile cardiomyocytes but similar and robust differentiation to multiple neural, pancreatic, and smooth muscle cell types. We identify shared and distinct genes and contributing pathways in the replicate ED-iPSC lines to enhance our ability to understand how reprogramming to iPSC impacts genes and pathways contributing to cardiomyocyte contractility potential.

Progress and challenges in macroencapsulation approaches for type 1 diabetes (T1D) treatment: Cells, biomaterials, and devices

Macroencapsulation technology has been an attractive topic in the field of treatment for Type 1 diabetes due to mechanical stability, versatility, and retrievability of the macro-capsule design. Macro-capsules can be categorized into extravascular and intravascular devices, in which solute transport relies either on diffusion or convection, respectively. Failure of macroencapsulation strategies can be due to limited regenerative capacity of the encased insulin-producing cells, sub-optimal performance of encapsulation biomaterials, insufficient immunoisolation, excessive blood thrombosis for vascular perfusion devices, and inadequate modes of mass transfer to support cell viability and function. However, significant technical advancements have been achieved in macroencapsulation technology, namely reducing diffusion distance for oxygen and nutrients, using pro-angiogenic factors to increase vascularization for islet engraftment, and optimizing membrane permeability and selectivity to prevent immune attacks from host's body. This review presents an overview of existing macroencapsulation devices and discusses the advances based on tissue-engineering approaches that will stimulate future research and development of macroencapsulation technology. Biotechnol. Bioeng. 2016;113: 1381-1402. © 2015 Wiley Periodicals, Inc.

MAFA and T3 Drive Maturation of Both Fetal Human Islets and Insulin-Producing Cells Differentiated From hESC

CONTEXT

Human embryonic stem cells (hESCs) differentiated toward β-cells and fetal human pancreatic islet cells resemble each other transcriptionally and are characterized by immaturity with a lack of glucose responsiveness, low levels of insulin content, and impaired proinsulin-to-insulin processing. However, their response to stimuli that promote functionality have not been compared.

OBJECTIVE

The objective of the study was to evaluate the effects of our previous strategies for functional maturation developed in rodents in these two human models of β-cell immaturity and compare their responses. Design, Settings, Participants, and Interventions: In proof-of-principle experiments using either adenoviral-mediated overexpression of V-Maf avian musculoaponeurotic fibrosarcoma oncogene homolog A (MAFA) or the physiologically driven path via thyroid hormone (T3) and human fetal islet-like cluster (ICC) functional maturity was evaluated. Then the effects of T3 were evaluated upon the functional maturation of hESCs differentiated toward β-cells.

MAIN OUTCOME MEASURES

Functional maturation was evaluated by the following parameters: glucose responsiveness, insulin content, expression of the mature β-cell transcription factor MAFA, and proinsulin-to-insulin processing.

RESULTS

ICCs responded positively to MAFA overexpression and T3 treatment as assessed by two different maturation parameters: increased insulin secretion at 16.8 mM glucose and increased proinsulin-to-insulin processing. In hESCs differentiated toward β-cells, T3 enhanced MAFA expression, increased insulin content (probably mediated by the increased MAFA), and increased insulin secretion at 16.8 mM glucose.

CONCLUSION

T3 is a useful in vitro stimulus to promote human β-cell maturation as shown in both human fetal ICCs and differentiated hESCs. The degree of maturation induced varied in the two models, possibly due to the different developmental status at the beginning of the study.

In Vitro Differentiation of Human Umbilical Cord Blood CD133(+)Cells into Insulin Producing Cells in Co-Culture with Rat Pancreatic Mesenchymal Stem Cells

Objective

Pancreatic stroma plays an important role in the induction of pancreatic cells by the use of close range signaling. In this respect, we presume that pancreatic mesenchymal cells (PMCs) as a fundamental factor of the stromal niche may have an effective role in differentiation of umbilical cord blood cluster of differentiation 133⁺ (UCB-CD133⁺) cells into newly-formed β-cells in vitro.

Materials and Methods

This study is an experimental research. The UCB-CD133⁺cells were purified by magnetic activated cell sorting (MACS) and differentiated into insulin producing cells (IPCs) in co-culture, both directly and indirectly with rat PMCs. Immunocytochemistry and enzyme linked immune sorbent assay (ELISA) were used to determine expression and production of insulin and C-peptide at the protein level.

Results

Our results demonstrated that UCB-CD133⁺differentiated into IPCs. Cells in islet-like clusters with (out) co-cultured with rat pancreatic stromal cells produced insulin and C-peptide and released them into the culture medium at the end of the induction protocol. However they did not respond well to glucose challenges.

Conclusion

Rat PMCs possibly affect differentiation of UCB-CD133⁺cells into IPCs by increasing the number of immature β-cells.

Using stem cells to produce insulin

INTRODUCTION

Tremendous progress has been made in generating insulin-producing cells from pluripotent stem cells. The best outcome of the refined protocols became apparent in the first clinical trial announced by ViaCyte, based on the implantation of pancreatic progenitors that would further mature into functional insulin-producing cells inside the patient's body.

AREAS COVERED

Several groups, including ours, have contributed to improve strategies to generate insulin-producing cells. Of note, the latest results have gained a substantial amount of interest as a method to create a potentially functional and limitless supply of β-cell to revert diabetes mellitus. This review analyzes the accomplishments that have taken place over the last few decades, summarizes the state-of-art methods for β-cell replacement therapies based on the differentiation of embryonic stem cells into glucose-responsive and insulin-producing cells in a dish and discusses alternative approaches to obtain new sources of insulin-producing cells.

EXPERT OPINION

Undoubtedly, recent events preface the beginning of a new era in diabetes therapy. However, in our opinion, a number of significant hurdles still stand in the way of clinical application. We believe that the combination of the private and public sectors will accelerate the process of obtaining the desired safe and functional β-cell surrogates.

Resveratrol ameliorates the maturation process of β-cell-like cells obtained from an optimized differentiation protocol of human embryonic stem cells

Human embryonic stem cells (hESCs) retain the extraordinary capacity to differentiate into different cell types of an adult organism, including pancreatic β-cells. For this particular lineage, although a lot of effort has been made in the last ten years to achieve an efficient and reproducible differentiation protocol, it was not until recently that this aim was roughly accomplished. Besides, several studies evidenced the impact of resveratrol (RSV) on insulin secretion, even though the mechanism by which this polyphenol potentiates glucose-stimulated insulin secretion (GSIS) is still not clear. The aim of this study was to optimize an efficient differentiation protocol that mimics in vivo pancreatic organogenesis and to investigate whether RSV may improve the final maturation step to obtain functional insulin-secreting cells. Our results indicate that treatment of hESCs (HS-181) with activin-A induced definitive endoderm differentiation as detected by the expression of SOX17 and FOXA2. Addition of retinoic acid (RA), Noggin and Cyclopamine promoted pancreatic differentiation as indicated by the expression of the early pancreatic progenitor markers ISL1, NGN3 and PDX1. Moreover, during maturation in suspension culture, differentiating cells assembled in islet-like clusters, which expressed specific endocrine markers such as PDX1, SST, GCG and INS. Similar results were confirmed with the human induced Pluripotent Stem Cell (hiPSC) line MSUH-001. Finally, differentiation protocols incorporating RSV treatment yielded numerous insulin-positive cells, induced significantly higher PDX1 expression and were able to transiently normalize glycaemia when transplanted in streptozotocin (STZ) induced diabetic mice thus promoting its survival. In conclusion, our strategy allows the efficient differentiation of hESCs into pancreatic endoderm capable of generating β-cell-like cells and demonstrates that RSV improves the maturation process.

Stemistry: the control of stem cells in situ using chemistry

A new paradigm for drug research has emerged, namely the deliberate search for molecules able to selectively affect the proliferation, differentiation, and migration of adult stem cells within the tissues in which they exist. Recently, there has been significant interest in medicinal chemistry toward the discovery and design of low molecular weight molecules that affect stem cells and thus have novel therapeutic activity. We believe that a successful agent from such a discover program would have profound effects on the treatment of many long-term degenerative disorders. Among these conditions are examples such as cardiovascular decay, neurological disorders including Alzheimer's disease, and macular degeneration, all of which have significant unmet medical needs. This perspective will review evidence from the literature that indicates that discovery of such agents is achievable and represents a worthwhile pursuit for the skills of the medicinal chemist.

Insulin-producing intestinal K cells protect nonobese diabetic mice from autoimmune diabetes

BACKGROUND & AIMS

Type 1 diabetes is caused by an aberrant response against pancreatic β cells. Intestinal K cells are glucose-responsive endocrine cells that might be engineered to secrete insulin. We generated diabetes-prone non-obese diabetic (NOD) mice that express insulin, via a transgene, in K cells. We assessed the effects on immunogenicity and diabetes development.

METHODS

Diabetes incidence and glucose homeostasis were assessed in NOD mice that expressed mouse preproinsulin II from a transgene in K cells and nontransgenic NOD mice (controls); pancreas and duodenum tissues were collected and analyzed by histology. We evaluated T cell responses to insulin, levels of circulating autoantibodies against insulin, and the percentage of circulating antigen-specific T cells. Inflammation of mesenteric and pancreatic lymph node cells was also evaluated.

RESULTS

The transgenic mice tended to have lower blood levels of glucose than control mice, associated with increased plasma levels of immunoreactive insulin and proinsulin. Fewer transgenic mice developed diabetes than controls. In analyses of pancreas and intestine tissues from the transgenic mice, insulin-producing K cells were not affected by the immune response and the mice had reduced destruction of endogenous β cells. Fewer transgenic mice were positive for insulin autoantibodies compared with controls. Cells isolated from mesenteric lymph nodes of the transgenic mice had significantly lower rates of proliferation and T cells from transgenic mice tended to secrete lower levels of inflammatory cytokines than from controls. At 15 weeks, transgenic mice had fewer peripheral CD8(+) T cells specific for NRP-V7 than control mice.

CONCLUSIONS

NOD mice with intestinal K cells engineered to express insulin have reduced blood levels of glucose, are less likely to develop diabetes, and have reduced immunity against pancreatic β cells compared with control NOD mice. This approach might be developed to treat patients with type 1 diabetes.

High oxygen condition facilitates the differentiation of mouse and human pluripotent stem cells into pancreatic progenitors and insulin-producing cells

Pluripotent stem cells have potential applications in regenerative medicine for diabetes. Differentiation of stem cells into insulin-producing cells has been achieved using various protocols. However, both the efficiency of the method and potency of differentiated cells are insufficient. Oxygen tension, the partial pressure of oxygen, has been shown to regulate the embryonic development of several organs, including pancreatic β-cells. In this study, we tried to establish an effective method for the differentiation of induced pluripotent stem cells (iPSCs) into insulin-producing cells by culturing under high oxygen (O2) conditions. Treatment with a high O2 condition in the early stage of differentiation increased insulin-positive cells at the terminus of differentiation. We found that a high O2 condition repressed Notch-dependent gene Hes1 expression and increased Ngn3 expression at the stage of pancreatic progenitors. This effect was caused by inhibition of hypoxia-inducible factor-1α protein level. Moreover, a high O2 condition activated Wnt signaling. Optimal stage-specific treatment with a high O2 condition resulted in a significant increase in insulin production in both mouse embryonic stem cells and human iPSCs and yielded populations containing up to 10% C-peptide-positive cells in human iPSCs. These results suggest that culturing in a high O2 condition at a specific stage is useful for the efficient generation of insulin-producing cells.

Functions and roles of proteins: diabetes as a paradigm

Molecular and cellular biology has moved towards complete and accurate knowledge of how molecules behave in space and time. Protein is considered as the primary group of molecules responsible for mediating most physiological processes. Changes in the levels of proteins may lead to the altered function and are responsible for many diseases. This review provides a partial molecular explanation of biological force-ratio generation that may act to split protein into branches, and shows molecular functional divergence. Developing a non-reductionist theory of the cellular function in medicine is clearly not sufficient. Finding effective parameters of the models by characterizing molecular interactions becomes necessary. Protein interactivity and stability provides a basis for an integrated understanding of pathologies such diabetes. One example of how a mechanistic analysis of such physiological processes can be of value is the time-delay between mRNA and translation that can act as a fork allowing a slowdown in gene expression.

Membranes to achieve immunoprotection of transplanted islets

Transplantation of islet or beta cells is seen as the cure for type 1 diabetes since it allows physiological regulation of blood glucose levels without requiring any compliance from the patients. In order to circumvent the use of immunosuppressive drugs (and their side effects), semipermeable membranes have been developed to encapsulate and immunoprotect transplanted cells. This review presents the historical developments of immunoisolation and provides an update on the current research in this field. A particular emphasis is laid on the fabrication, characterization and performance of membranes developed for immunoisolation applications.

Thyroid hormone promotes postnatal rat pancreatic β-cell development and glucose-responsive insulin secretion through MAFA

Neonatal β cells do not secrete glucose-responsive insulin and are considered immature. We previously showed the transcription factor MAFA is key for the functional maturation of β cells, but the physiological regulators of this process are unknown. Here we show that postnatal rat β cells express thyroid hormone (TH) receptor isoforms and deiodinases in an age-dependent pattern as glucose responsiveness develops. In vivo neonatal triiodothyronine supplementation and TH inhibition, respectively, accelerated and delayed metabolic development. In vitro exposure of immature islets to triiodothyronine enhanced the expression of Mafa, the secretion of glucose-responsive insulin, and the proportion of responsive cells, all of which are effects that were abolished in the presence of dominant-negative Mafa. Using chromatin immunoprecipitation and electrophoretic mobility shift assay, we show that TH has a direct receptor-ligand interaction with the Mafa promoter and, using a luciferase reporter, that this interaction was functional. Thus, TH can be considered a physiological regulator of functional maturation of β cells via its induction of Mafa.

Adult pancreas side population cells expand after β cell injury and are a source of insulin-secreting cells

Pancreas stem cells are a potential source of insulin-producing β cells for the therapy of diabetes. In adult tissues the ‘side population’ (SP) of cells that effluxes the DNA binding dye Hoechst 33342 through ATP-binding cassette transporters has stem cell properties. We hypothesised therefore that the SP would expand in response to β cell injury and give rise to functional β cells. SP cells were flow sorted from dissociated pancreas cells of adult mice, analysed for phenotype and cultured with growth promoting and differentiation factors before analysis for hormone expression and glucose-stimulated insulin secretion. SP cell number and colony forming potential (CFP) increased significantly in models of type diabetes, and after partial pancreatectomy, in the absence of hyperglycaemia. SP cells, ∼1% of total pancreas cells at 1 week of age, were enriched >10-fold for CFP compared to non-SP cells. Freshly isolated SP cells contained no insulin protein or RNA but expressed the homeobox transcription factor Pdx1 required for pancreas development and β cell function. Pdx1, along with surface expression of CD326 (Ep-Cam), was a marker of the colony forming and proliferation potential of SP cells. In serum-free medium with defined factors, SP cells proliferated and differentiated into islet hormone-expressing cells that secreted insulin in response to glucose. Insulin expression was maintained when tissue was transplanted within vascularised chambers into diabetic mice. SP cells in the adult pancreas expand in response to β cell injury and are a source of β cell progenitors with potential for the treatment of diabetes.

Pancreatic transcription factors containing protein transduction domains drive mouse embryonic stem cells towards endocrine pancreas

Protein transduction domains (PTDs), such as the HIV1-TAT peptide, have been previously used to promote the uptake of proteins into a range of cell types, including stem cells. Here we generated pancreatic transcription factors containing PTD sequences and administered these to endoderm enriched mouse embryonic stem (ES) cells under conditions that were designed to mimic the pattern of expression of these factors in the developing pancreas. The ES cells were first cultured as embryoid bodies and treated with Activin A and Bone morphogenetic protein 4 (BMP4) to promote formation of definitive endoderm. Cells were subsequently plated as a monolayer and treated with different combinations of the modified recombinant transcription factors Pdx1 and MafA. The results demonstrate that each transcription factor was efficiently taken up by the cells, where they were localized in the nuclei. RT-qPCR was used to measure the expression levels of pancreatic markers. After the addition of Pdx1 alone for a period of five days, followed by the combination of Pdx1 and TAT-MafA in a second phase, up-regulation of insulin 1, insulin 2, Pdx1, Glut2, Pax4 and Nkx6.1 was observed. As assessed by immunocytochemistry, double positive insulin and Pdx1 cells were detected in the differentiated cultures. Although the pattern of pancreatic markers expression in these cultures was comparable to that of a mouse transformed β-cell line (MIN-6) and human islets, the expression levels of insulin observed in the differentiated ES cell cultures were several orders of magnitude lower. This suggests that, although PTD-TFs may prove useful in studying the role of exogenous TFs in the differentiation of ES cells towards islets and other pancreatic lineages, the amount of insulin generated is well below that required for therapeutically useful cells.

Human liver cells expressing albumin and mesenchymal characteristics give rise to insulin-producing cells

Activation of the pancreatic lineage in the liver has been suggested as a potential autologous cell replacement therapy for diabetic patients. Transcription factors-induced liver-to-pancreas reprogramming has been demonstrated in numerous species both in vivo and in vitro. However, human-derived liver cells capable of acquiring the alternate pancreatic repertoire have never been characterized. It is yet unknown whether hepatic-like stem cells or rather adult liver cells give rise to insulin-producing cells. Using an in vitro experimental system, we demonstrate that proliferating adherent human liver cells acquire mesenchymal-like characteristics and a considerable level of cellular plasticity. However, using a lineage-tracing approach, we demonstrate that insulin-producing cells are primarily generated in cells enriched for adult hepatic markers that coexpress both albumin and mesenchymal markers. Taken together, our data suggest that adult human hepatic tissue retains a substantial level of developmental plasticity, which could be exploited in regenerative medicine approaches.

Pyridoxal 5' phosphate protects islets against streptozotocin-induced beta-cell dysfunction--in vitro and in vivo

Administration of pyridoxal 5' phosphate (PLP) has demonstrated beneficial effects in the management of diabetes, albeit the mechanism(s) are not clearly understood. The present study addressed the islet-cell function(s) in streptozotocin (STZ)-induced diabetic mice both in vitro and in vivo. Primary islet cells primed with or without PLP (5 mmol/L) were treated with STZ (2 mmol/L) and were measured for cell viability, insulin secretion, free radicals and mRNA of Insulin and Pdx1. The specificity of PLP's response on insulin secretion was assessed with amino oxy acetic acid (AOAA)-PLP inhibitor. In vivo, the STZ (200 mg/kg b.w)-treated diabetic mice received 10 mmol/L PLP intraperitoneally a day before (PLP + STZ) or after (STZ + PLP) with three more doses once every 48 h. On 7, 14 and 21 d of STZ treatment, physiological parameters, islet morphology, insulin:glucagon, insulin:HSP104, and mRNA of Insulin, Glut2, Pdx1 and Reg1 were determined. In vitro, PLP protected islets against STZ-induced changes in viability, insulin secretion, prevented increase in free radical levels and normalized mRNA of Insulin and Pdx1. Further, AOAA inhibited PLP-induced insulin secretion in islets. In vivo, PLP treatment normalized STZ-induced changes in physiological parameters, circulating levels of PLP and insulin. Also, islet morphology, insulin:glucagon, insulin:HSP104 and mRNA levels of Insulin, Pdx1 and Glut2 were restored by 21 d. Although PLP treatment (pre- and post-STZ) prevented development of frank diabetes, STZ + PLP mice showed transient hyperglycemia, and increased mRNA for Reg1. The data suggest the cytoprotective vis-à-vis insulinotrophic effects of PLP against STZ-induced beta-cell dysfunction and underline its prophylactic use in the management of diabetes.

Reversible immortalization of rat pancreatic β cells with a novel immortalizing and tamoxifen-mediated self-recombination tricistronic vector

Although the strategy of "Cre/LoxP-based reversible immortalization" holds great promise to overcome the cellular senescence of primary cell cultures for their further use, a secondary gene transfer for Cre expression is usually utilized to trigger the excision of the immortalizing genes in a large number of cells, thus presenting a formidable hurdle for large-scale application. We modified the strategy by utilizing a tricistronic retroviral vector pLCRSTP, in which Cre-ER, simian virus 40 large T antigen (SV40LTAg) oncogene, and a reporter gene were flanked by the same pair of LoxA sites. Five immortalized rat pancreatic β cell clones transduced with pLCRSTP, and six immortalized rat pancreatic β cell clones co-transduced with pLCRSTP and another vector encoding the human telomerase reverse transcriptase (hTERT) gene, were obtained, respectively. The Cre-ER protein could be induced to translocate from the cytoplasm to the nucleus by 4-hydroxytamoxifen to make SV40LTAg, hTERT and the Cre-ER gene itself excise without a secondary gene transfer. Our studies suggest that this system is useful to expand rat β cells and may allow for large-scale production due to its simpler manipulation.

Indolactam V/GLP-1-mediated differentiation of human iPS cells into glucose-responsive insulin-secreting progeny

Nuclear reprogramming of somatic tissue enables derivation of induced pluripotent stem (iPS) cells from an autologous, non-embryonic origin. The purpose of the current study was to establish efficient protocols for lineage-specification of human iPS cells into functional glucose-responsive, insulin-producing progeny. We generated human iPS cells, which were then guided with recombinant growth factors that mimic the essential signaling for pancreatic development. Reprogrammed with four stemness factors, human fibroblasts were here converted into authentic iPS cells. Under feeder-free conditions, fate-specification was initiated with activin A and Wnt3a that triggered engagement into definitive endoderm, followed by priming with FGF10 and KAAD-cyclopamine. Addition of retinoic acid, boosted by the pancreatic endoderm inducer indolactam V (ILV), yielded pancreatic progenitors expressing PDX1, NGN3 and NEUROD1 markers. Further guidance, under IGF-1, HGF and DAPT, was enhanced by glucagon like peptide-1 (GLP-1) to generate islet-like cells that expressed pancreas-specific markers including insulin and glucagon. Derived progeny demonstrated sustained expression of PDX1, and functional responsiveness to glucose challenge secreting up to 230 pM of C-peptide. A pancreatogenic cocktail enriched with ILV/GLP-1 offers a proficient means to specify human iPS cells into glucose-responsive hormone-producing progeny, refining the development of a personalized platform for islet-like cell generation.

Inconsistent formation and nonfunction of insulin-positive cells from pancreatic endoderm derived from human embryonic stem cells in athymic nude rats

Embryonic stem cell therapy has been proposed as a therapeutic strategy to restore β-cell mass and function in T1DM. Recently, a group from Novocell (now ViaCyte) reported successful development of glucose-responsive islet-like structures after implantation of pancreatic endoderm (PE) derived from human embryonic stem cells (hESC) into immune-deficient mice. Our objective was to determine whether implantation of hESC-derived pancreatic endoderm from Novocell into athymic nude rats results in development of viable glucose-responsive pancreatic endocrine tissue. Athymic nude rats were implanted with PE derived from hESC either via implantation into the epididymal fat pads or by subcutaneous implantation into TheraCyte encapsulation devices for 20 wk. Blood glucose, weight, and human insulin/C-peptide secretion were monitored by weekly blood draws. Graft β-cell function was assessed by a glucose tolerance test, and graft morphology was assessed by immunohistochemistry and immunofluorescence. At 20 wk postimplantation, epididymal fat-implanted PE progressed to develop islet-like structures in 50% of implants, with a mean β-cell fractional area of 0.8 ± 0.3%. Human C-peptide and insulin were detectable, but at very low levels (C-peptide = 50 ± 26 pmol/l and insulin = 15 ± 7 pmol/l); however, there was no increase in human C-peptide/insulin levels after glucose challenge. There was no development of viable pancreatic tissue or meaningful secretory function when human PE was implanted in the TheraCyte encapsulation devices. These data confirm that islet-like structures develop from hESC differentiated to PE by the protocol developed by NovoCell. However, the extent of endocrine cell formation and secretory function is not yet sufficient to be clinically relevant.

A factor(s) secreted from MIN-6 beta-cells stimulates differentiation of definitive endoderm enriched embryonic stem cells towards a pancreatic lineage

In the mouse the developing pancreas is controlled by contact with, and signalling molecules secreted from, surrounding cells. These factors are best studied using explant cultures of embryonic tissue. The present study was undertaken to determine whether embryonic stem (ES) cells could be used as an alternative model in vitro system to investigate the role of cell-cell interactions in the developing pancreas. Transwell culture experiments showed that MIN-6 beta-cells secreted a factor or factors that promoted differentiation of ES cell derived definitive endoderm enriched cells towards a pancreatic fate. Further studies using MIN-6 condition medium showed that the factor(s) involved was restricted to MIN-6 cells, could be concentrated with ammonium sulphate, and was sensitive to heat treatment, suggesting that it was a protein or peptide. Further analyses showed that insulin or proinsulin failed to mimic the effects of the conditioned media. Collectively, these results suggest that beta-cells secrete a factor(s) capable of controlling their own differentiation and maturation. The culture system described here presents unique advantages in the identification and characterisation of these factors.

Noggin, retinoids, and fibroblast growth factor regulate hepatic or pancreatic fate of human embryonic stem cells

BACKGROUND & AIMS

New sources of beta cells are needed to develop cell therapies for patients with diabetes. An in vitro, sequential method has been developed to derive pancreatic progenitors, but this technique has not been used for other cell lines. We investigated whether definitive endoderm derived from human embryonic stem (hES) cells might be used to create beta cells.

METHODS

Five hES cell lines were induced to form pancreatic progenitors and analyzed for pancreas markers. Cells were incubated with a bone morphogenetic protein (BMP) antagonist, retinoids, a Hedgehog antagonist, or fibroblast growth factor (FGF) and phenotypes were analyzed.

RESULTS

Four hES cell lines sequentially generated definitive endoderm, primitive gut, and posterior foregut equivalents, as described previously. However, functional hepatocytes, rather than pancreas progenitors, developed. Consistent with liver development, FGF and BMP signaling pathways were involved in this process; their inhibition disrupted hepatocyte differentiation. During early stages of development, exposure of cells to noggin and retinoid acid, followed by FGF10, generated pancreatic cells (PDX1+; 50%-80%) that coexpressed FOXA2, HNF6, and SOX9.

CONCLUSIONS

These findings demonstrate the combined functions of endogenous BMP and supplemented FGF in inducing differentiation of hepatocytes from hES cells and the ability to shift developmental pathways from hepatic to pancreatic cell differentiation. Although additional signals appear to be required for full specification of PDX1(+) early pancreatic progenitors (via PTF1a and NKX6.1 coexpression), these findings indicate the signaling pathways required for differentiation of bipotential progenitors.

Emerging use of stem cells in regenerative medicine

Stem cells represent a unique opportunity for regenerative medicine to cure a broad number of diseases for which current treatment only alleviates symptoms or retards further disease progression. However, the number of stem cells available has speedily increased these past 10 years and their diversity presents new challenges to clinicians and basic scientists who intend to use them in clinics or to study their unique properties. In addition, the recent possibility to derive pluripotent stem cells from somatic cells using epigenetic reprogramming has further increased the clinical interest of stem cells since induced pluripotent stem cells could render personalized cell-based therapy possible. The present review will attempt to summarize the advantages and challenges of each type of stem cell for current and future clinical applications using specific examples.

Converting human pluripotent stem cells into beta-cells: recent advances and future challenges

PURPOSE OF REVIEW

The transplantation of insulin-producing beta-cells derived from human embryonic stem cells and induced pluripotent stem cells (collectively termed pluripotent stem cells or PSCs) holds great promise for therapy of diabetes mellitus. The purpose of this review is to summarize recent advances in this area, emphasizing the importance of studies of endocrine pancreas development in efforts to direct PSC differentiation into endocrine cells, as well as to outline the major challenges remaining before transplantation of PSC-derived beta-cells can become a reality.

RECENT FINDINGS

Although several protocols to generate glucose-responsive pancreatic beta-cells in vitro have been described, the most successful approaches are those that most closely mimic embryonic development of the endocrine pancreas. Until recently, cells generated by these methods have exhibited immature pancreatic endocrine phenotypes. However, protocols that generate more functional beta-like cells have now been described. In addition, small molecules are being used to improve protocols to direct differentiation of PSCs into endoderm and pancreatic lineages.

SUMMARY

Advances over the last decade suggest that generating functional beta-cells from human PSCs is achievable. However, there are aspects of beta-cell development that are not well understood and are hampering generation of PSC-derived beta-cells. In particular, the signaling pathways that instruct endocrine progenitor cells to differentiate into mature and functional beta-cells are poorly understood. Other significant obstacles remain, including the need for safe and cost-effective differentiation methods for large-scale generation of transplantation quality beta-cells, methods to prevent immune rejection of grafted tissues, and amelioration of the risks of tumorigenesis.

Successes and disappointments with clinical islet transplantation

Transplantation of pancreatic islets is considered a therapeutic option for patients with type 1 diabetes mellitus who have life-threatening hypoglycaemic episodes. After the procedure, a decrease in the frequency and severity of hypoglycaemic episodes and sustained graft function as indicated by detectable levels of C-peptide can be seen in the majority of patients. However, true insulin independence, if achieved, usually lasts for at most a few years. Apart from the low insulin independence rates, reasons for concern regarding this procedure are the side effects of the immunosuppressive therapy, allo-immunization, and the high costs. Moreover, whether islet transplantation prevents the progression of diabetic micro- and macrovascular complications is largely unknown. Areas of current research include the development of less toxic immunosuppressive regimens, the control of the inflammatory reaction immediately after transplantation, the identification of the optimal anatomical site for islet infusion, and the possibility to encapsulate transplanted islets to protect them from the allo-immune response. At present, pancreatic islet transplantation is still an experimental procedure, which is only indicated for a highly selected group of type 1 diabetic patients with life-threatening hypoglycaemic episodes.

Human embryonic stem-cell derivatives for full reconstruction of the pluristratified epidermis: a preclinical study

BACKGROUND

Cell therapy for large burns is dependent upon autologous epidermis reconstructed in vitro. However, the effectiveness of current procedures is limited by the delay needed to culture the patient's own keratinocytes. To assess whether the keratinocyte progeny of human embryonic stem cells (hESCs) could be used to form a temporary skin substitute for use in patients awaiting autologous grafts, we investigated the cells' capability of constructing a pluristratified epidermis.

METHODS

hESCs from lines H9 and SA01 were seeded at least in triplicate on fibroblast feeder cells for 40 days in a medium supplemented with bone morphogenetic protein 4 and ascorbic acid. Molecular characterisation of cell differentiation was done throughout the process by quantitative PCR, fluorescence-activated cell sorting, and immunocytochemical techniques. Keratinocyte molecular differentiation and functional capacity to construct a human epidermis were assessed in vitro and in vivo.

FINDINGS

From hESCs, we generated a homogeneous population of cells that showed phenotypic characteristics of basal keratinocytes. Expression levels of genes encoding keratin 14, keratin 5, integrin alpha6, integrin beta4, collagen VII, and laminin 5 in these cells were similar to those in basal keratinocytes. After seeding on an artificial matrix, keratinocytes derived from hESCs (K-hESCs) formed a pluristratified epidermis. Keratin-14 immunostaining was seen in the basal compartment, with keratin 10 present in layers overlying the basal layer. Involucrin and filaggrin, late markers of epidermal differentiation, were detected in the uppermost layers only. 12 weeks after grafting onto five immunodeficient mice, epidermis derived from K-hESCs had a structure consistent with that of mature human skin. Human involucrin was appropriately located in spinous and granular layers and few Ki67-positive cells were detected in the basal layer.

INTERPRETATION

hESCs can be differentiated into basal keratinocytes that are fully functional--ie, able to construct a pluristratified epidermis. This resource could be developed to provide temporary skin substitutes for patients awaiting autologous grafts.

FUNDING

Institut National de la Santé et de la Recherche Médicale, University Evry Val d'Essonne, Association Française contre les Myopathies, Fondation René Touraine, and Genopole.

Pancreatic stellate cells can form new beta-like cells

Regenerative medicine, including cell-replacement strategies, may have an important role in the treatment of Type 1 and Type 2 diabetes, both of which are associated with decreased islet cell mass. To date, significant progress has been made in deriving insulin-secreting beta-like cells from human ES (embryonic stem) cells. However, the cells are not fully differentiated, and there is a long way to go before they could be used as a replenishable supply of insulin-secreting beta-cells for transplantation. For this reason, adult pancreatic stem cells are seen as an alternative source that could be expanded and differentiated ex vivo, or induced to form new islets in situ. In this issue of the Biochemical Journal, Mato et al. used drug selection to purify a population of stellate cells from explant cultures of pancreas from lactating rats. The selected cells express some stem-cell markers and can be grown for over 2 years as a fibroblast-like monolayer. When plated on extracellular matrix, along with a cocktail of growth factors that included insulin, transferrin, selenium and the GLP-1 (glucagon-like peptide-1) analogue exendin-4, the cells differentiated into cells that expressed many of the phenotypic markers characteristic of a beta-cell, and exhibited an insulin-secretory response, albeit weak, to glucose. The ability to purify this cell population opens up the possibility of unravelling the mechanisms that control self-renewal and differentiation of pancreatic cells that share some of the properties of stem cells.