Marked differences in differentiation propensity among human embryonic stem cell lines

Specification of functional neurons and glia from human pluripotent stem cells

Human pluripotent stem cells (PSCs) such as embryonic stem cells (ESCs) and induced pluripotent stem cells (iPSCs) hold great promise in regenerative medicine as they are an important source of functional cells for potential cell replacement. These human PSCs, similar to their counterparts of mouse, have the full potential to give rise to any type of cells in the body. However, for the promise to be fulfilled, it is necessary to convert these PSCs into functional specialized cells. Using the developmental principles of neural lineage specification, human ESCs and iPSCs have been effectively differentiated to regional and functional specific neurons and glia, such as striatal gama-aminobutyric acid (GABA)-ergic neurons, spinal motor neurons and myelin sheath forming oligodendrocytes. The human PSCs, in general differentiate after the similar developmental program as that of the mouse: they use the same set of cell signaling to tune the cell fate and they share a conserved transcriptional program that directs the cell fate transition. However, the human PSCs, unlike their counterparts of mouse, tend to respond divergently to the same set of extracellular signals at certain stages of differentiation, which will be a critical consideration to translate the animal model based studies to clinical application.

Increased proteasome activity in human embryonic stem cells is regulated by PSMD11

Embryonic stem cells can replicate continuously in the absence of senescence and, therefore, are immortal in culture. Although genome stability is essential for the survival of stem cells, proteome stability may have an equally important role in stem-cell identity and function. Furthermore, with the asymmetric divisions invoked by stem cells, the passage of damaged proteins to daughter cells could potentially destroy the resulting lineage of cells. Therefore, a firm understanding of how stem cells maintain their proteome is of central importance. Here we show that human embryonic stem cells (hESCs) exhibit high proteasome activity that is correlated with increased levels of the 19S proteasome subunit PSMD11 (known as RPN-6 in Caenorhabditis elegans) and a corresponding increased assembly of the 26S/30S proteasome. Ectopic expression of PSMD11 is sufficient to increase proteasome assembly and activity. FOXO4, an insulin/insulin-like growth factor-I (IGF-I) responsive transcription factor associated with long lifespan in invertebrates, regulates proteasome activity by modulating the expression of PSMD11 in hESCs. Proteasome inhibition in hESCs affects the expression of pluripotency markers and the levels of specific markers of the distinct germ layers. Our results suggest a new regulation of proteostasis in hESCs that links longevity and stress resistance in invertebrates to hESC function and identity.

Perspectives on whole-organ assembly: moving toward transplantation on demand

There is an ever-growing demand for transplantable organs to replace acute and chronically damaged tissues. This demand cannot be met by the currently available donor organs. Efforts to provide an alternative source have led to the development of organ engineering, a discipline that combines cell biology, tissue engineering, and cell/organ transplantation. Over the last several years, engineered organs have been implanted into rodent recipients and have shown modest function. In this article, we summarize the most recent advances in this field and provide a perspective on the challenges of translating this promising new technology into a proven regenerative therapy.

A small molecule that promotes cardiac differentiation of human pluripotent stem cells under defined, cytokine- and xeno-free conditions

Human pluripotent stem cells (hPSCs), including embryonic stem cells and induced pluripotent stem cells, are potentially useful in regenerative therapies for heart disease. For medical applications, clinical-grade cardiac cells must be produced from hPSCs in a defined, cost-effective manner. Cell-based screening led to the discovery of KY02111, a small molecule that promotes differentiation of hPSCs to cardiomyocytes. Although the direct target of KY02111 remains unknown, results of the present study suggest that KY02111 promotes differentiation by inhibiting WNT signaling in hPSCs but in a manner that is distinct from that of previously studied WNT inhibitors. Combined use of KY02111 and WNT signaling modulators produced robust cardiac differentiation of hPSCs in a xeno-free, defined medium, devoid of serum and any kind of recombinant cytokines and hormones, such as BMP4, Activin A, or insulin. The methodology has potential as a means for the practical production of human cardiomyocytes for regeneration therapies.

Pivots of pluripotency: the roles of non-coding RNA in regulating embryonic and induced pluripotent stem cells

BACKGROUND

Induced pluripotent stem cells (iPSC) derived from reprogrammed patient somatic cells possess enormous therapeutic potential. However, unlocking the full capabilities of iPSC will require an improved understanding of the molecular mechanisms which govern the induction and maintenance of pluripotency, as well as directed differentiation to clinically relevant lineages. Induced pluripotency of a differentiated cell is mediated by sequential cascades of genetic and epigenetic reprogramming of somatic histone and DNA CpG methylation marks. These genome-wide changes are mediated by a coordinated activity of transcription factors and epigenetic modifying enzymes. Non-coding RNAs (ncRNAs), including microRNAs (miRNAs) and long non-coding RNAs (lncRNAs), are now recognized as an important third class of regulators of the pluripotent state.

SCOPE OF REVIEW

This review surveys the currently known roles and mechanisms of ncRNAs in regulating the embryonic and induced pluripotent states.

MAJOR CONCLUSIONS

Through a variety of mechanisms, ncRNAs regulate constellations of key pluripotency genes and epigenetic regulators, and thus critically determine induction and maintenance of the pluripotent state.

GENERAL SIGNIFICANCE

A further understanding of the roles of ncRNAs in regulating pluripotency may help assess the quality of human iPSC reprogramming. Additionally, ncRNA biology may help decipher potential transcriptional and epigenetic commonalities between the self renewal processes that govern both ESC and tumor initiating cancer stem cells (CSC). This article is part of a Special Issue entitled Biochemistry of Stem Cells.

iPS cell modeling of cardiometabolic diseases

Cardiometabolic diseases encompass simple monogenic enzyme deficiencies with well-established pathogenesis and clinical outcomes to complex polygenic diseases such as the cardiometabolic syndrome. The limited availability of relevant human cell types such as cardiomyocytes has hampered our ability to adequately model and study pathways or drugs relevant to these diseases in the heart. The recent discovery of induced pluripotent stem (iPS) cell technology now offers a powerful opportunity to establish translational platforms for cardiac disease modeling, drug discovery, and pre-clinical testing. In this article, we discuss the excitement and challenges of modeling cardiometabolic diseases using iPS cell and their potential to revolutionize translational research.

Induced pluripotent stem cells: past, present, and future

The development of iPSCs reflected the merging of three major scientific streams and has in turn led to additional new branches of investigation. However, there is still debate about whether iPSCs are functionally equivalent to ESCs. This question should be answered only by science, not by politics or business.

Induced pluripotent stem cells: the new patient?

Worldwide increases in life expectancy have been paralleled by a greater prevalence of chronic and age-associated disorders, particularly of the cardiovascular, neural and metabolic systems. This has not been met by commensurate development of new drugs and therapies, which is in part owing to the difficulty in modelling human diseases in laboratory assays or experimental animals. Patient-specific induced pluripotent stem (iPS) cells are an emerging paradigm that may address this. Reprogrammed somatic cells from patients are already applied in disease modelling, drug testing and drug discovery, thus enabling researchers to undertake studies for treating diseases 'in a dish', which was previously inconceivable.

Therapeutic potential of human induced pluripotent stem cells in experimental stroke

Ischemic stroke mainly caused by middle cerebral artery occlusion (MCAo) is a major type of stroke, but there are currently very limited therapeutic options for its cure. Neural stem cells (NSCs) or neural precursor cells (NPCs) derived from various sources are known to survive and improve neurological functions when they are engrafted in animal models of stroke. Induced pluripotent stem cells (iPSCs) generated from somatic cells of patients are novel cells that promise the autologous cell therapy for stroke. In this study, we successfully differentiated iPSCs derived from human fibroblasts into NPCs and found their robust therapeutic potential in a rodent MCAo stroke model. We observed the significant graft-induced behavioral recovery, as well as extensive neural tissue formation. Animal MRI results indicated that the majority of contralaterally transplanted iPSC-derived NPCs migrated to the peri-infarct area, showing a pathotropism critical for tissue recovery. The transplanted animals exhibited the significant reduction of stroke-induced inflammatory response, gliosis and apoptosis, and the contribution to the endogenous neurogenesis. Our results demonstrate that iPSC-derived NPCs are effective cells for the treatment of stroke.

Differentiation of human embryonic stem cells and induced pluripotent stem cells to cardiomyocytes: a methods overview

Since human embryonic stem cells were first differentiated to beating cardiomyocytes a decade ago, interest in their potential applications has increased exponentially. This has been further enhanced over recent years by the discovery of methods to induce pluripotency in somatic cells, including those derived from patients with hereditary cardiac diseases. Human pluripotent stem cells have been among the most challenging cell types to grow stably in culture, but advances in reagent development now mean that most laboratories can expand both embryonic and induced pluripotent stem cells robustly using commercially available products. However, differentiation protocols have lagged behind and in many cases only produce the cell types required with low efficiency. Cardiomyocyte differentiation techniques were also initially inefficient and not readily transferable across cell lines, but there are now a number of more robust protocols available. Here, we review the basic biology underlying the differentiation of pluripotent cells to cardiac lineages and describe current state-of-the-art protocols, as well as ongoing refinements. This should provide a useful entry for laboratories new to this area to start their research. Ultimately, efficient and reliable differentiation methodologies are essential to generate desired cardiac lineages to realize the full promise of human pluripotent stem cells for biomedical research, drug development, and clinical applications.

Cardiomyocytes derived from human induced pluripotent stem cells as models for normal and diseased cardiac electrophysiology and contractility

Since the first description of human induced pluripotent stem cell-derived cardiomyocytes (hiPSC-CMs), these cells have garnered tremendous interest for their potential use in patient-specific analysis and therapy. Additionally, hiPSC-CMs can be derived from donor cells from patients with specific cardiac disorders, enabling in vitro human disease models for mechanistic study and therapeutic drug assessment. However, a full understanding of their electrophysiological and contractile function is necessary before this potential can be realized. Here, we review this emerging field from a functional perspective, with particular emphasis on beating rate, action potential, ionic currents, multicellular conduction, calcium handling and contraction. We further review extant hiPSC-CM disease models that recapitulate genetic myocardial disease.

Efficient neuronal differentiation and maturation of human pluripotent stem cells encapsulated in 3D microfibrous scaffolds

Developing an efficient culture system for controlled human pluripotent stem cell (hPSC) differentiation into selected lineages is a major challenge in realizing stem cell-based clinical applications. Here, we report the use of chitin-alginate 3D microfibrous scaffolds, previously developed for hPSC propagation, to support efficient neuronal differentiation and maturation under chemically defined culture conditions. When treated with neural induction medium containing Noggin/retinoic acid, the encapsulated cells expressed much higher levels of neural progenitor markers SOX1 and PAX6 than those in other treatment conditions. Immunocytochemisty analysis confirmed that the majority of the differentiated cells were nestin-positive cells. Subsequently transferring the scaffolds to neuronal differentiation medium efficiently directed these encapsulated neural progenitors into mature neurons, as detected by RT-PCR and positive immunostaining for neuron markers βIII tubulin and MAP2. Furthermore, flow cytometry confirmed that >90% βIII tubulin-positive neurons was achieved for three independent iPSC and hESC lines, a differentiation efficiency much higher than previously reported. Implantation of these terminally differentiated neurons into SCID mice yielded successful neural grafts comprising MAP2 positive neurons, without tumorigenesis, suggesting a potential safe cell source for regenerative medicine. These results bring us one step closer toward realizing large-scale production of stem cell derivatives for clinical and translational applications.

The generation of definitive neural stem cells from PiggyBac transposon-induced pluripotent stem cells can be enhanced by induction of the NOTCH signaling pathway

Cell-based therapies using neural stem cells (NSCs) have shown positive outcomes in various models of neurological injury and disease. Induced pluripotent stem cells (iPSCs) address many problems associated with NSCs from various sources, including the immune response and cell availability. However, due to inherent differences between embryonic stem cells (ESCs) and iPSCs, detailed characterization of the iPS-derived NSCs will be required before translational experiments can be performed. Murine piggyBac transposon iPSCs were clonally expanded in floating sphere colonies to generate primitive NSCs initially with serum-free media (SFM) containing the leukemia inhibitory factor and followed by SFM with the fibroblast growth factor-2 (FGF2) to form colonies of definitive NSCs (dNSCs). Primitive and definitive clonally derived neurospheres were successfully generated using the default conditions from iPSCs and ESCs. However, the iPSC-dNSCs expressed significantly higher levels of pluripotency and nonectoderm lineage genes compared to equivalent ESC-dNSCs. The addition of the bone morphogenetic proteins antagonist, Noggin, to the media significantly increased primary neurosphere generation from the iPSC lines, but did not affect the dNSC sphere colonies generated. The induction of the NOTCH pathway by the Delta-like ligand 4 (DLL4) improved the generation and quality of dNSCs, as demonstrated by a reduction in pluripotency and nonectodermal markers, while maintaining NSC-specific gene expression. The iPS-dNSCs (+DLL4) showed functional neural differentiation by immuncytochemical staining and electrophysiology. This study suggests the intrinsic differences between ESCs and iPSCs in their ability to acquire a dNSC fate that can be overcome by inducing the NOTCH pathway.

Production of functional classical brown adipocytes from human pluripotent stem cells using specific hemopoietin cocktail without gene transfer

Brown adipose tissue is attracting much attention due to its antiobestic effects; however, its development and involvement in metabolic improvement remain elusive. Here we established a method for a high-efficiency (>90%) differentiation of human pluripotent stem cells (hPSCs) into functional classical brown adipocytes (BAs) using specific hemopoietin cocktail (HC) without exogenous gene transfer. BAs were not generated without HC, and lack of a component of HC induced white adipocyte (WA) marker expressions. hPSC-derived BA (hPSCdBA) showed respiratory and thermogenic activation by β-adrenergic receptor (AdrRβ) stimuli and augmented lipid and glucose tolerance, whereas human multipotent stromal cell-derived WA (hMSCdWA) improved lipid but inhibited glucose metabolism. Cotransplantation of hPSCdBA normalized hMSCdWA-induced glucose intolerance. Surprisingly, hPSCdBAs expressed various hemopoietin genes, serving as stroma for myeloid progenitors. Moreover, AdrRβ stimuli enhanced recovery from chemotherapy-induced myelosuppression. Our study enhances our understanding of BA, identifying roles in metabolic and hemogenic regulation.

The B-MYB transcriptional network guides cell cycle progression and fate decisions to sustain self-renewal and the identity of pluripotent stem cells

Embryonic stem cells (ESCs) are pluripotent and have unlimited self-renewal capacity. Although pluripotency and differentiation have been examined extensively, the mechanisms responsible for self-renewal are poorly understood and are believed to involve an unusual cell cycle, epigenetic regulators and pluripotency-promoting transcription factors. Here we show that B-MYB, a cell cycle regulated phosphoprotein and transcription factor critical to the formation of inner cell mass, is central to the transcriptional and co-regulatory networks that sustain normal cell cycle progression and self-renewal properties of ESCs. Phenotypically, B-MYB is robustly expressed in ESCs and induced pluripotent stem cells (iPSCs), and it is present predominantly in a hypo-phosphorylated state. Knockdown of B-MYB results in functional cell cycle abnormalities that involve S, G2 and M phases, and reduced expression of critical cell cycle regulators like ccnb1 and plk1. By conducting gene expression profiling on control and B-MYB deficient cells, ChIP-chip experiments, and integrative computational analyses, we unraveled a highly complex B-MYB-mediated transcriptional network that guides ESC self-renewal. The network encompasses critical regulators of all cell cycle phases and epigenetic regulators, pluripotency transcription factors, and differentiation determinants. B-MYB along with E2F1 and c-MYC preferentially co-regulate cell cycle target genes. B-MYB also co-targets genes regulated by OCT4, SOX2 and NANOG that are significantly associated with stem cell differentiation, embryonic development, and epigenetic control. Moreover, loss of B-MYB leads to a breakdown of the transcriptional hierarchy present in ESCs. These results coupled with functional studies demonstrate that B-MYB not only controls and accelerates cell cycle progression in ESCs it contributes to fate decisions and maintenance of pluripotent stem cell identity.

Polyglutamine (polyQ) disorders: the chromatin connection

Polyglutamine (PolyQ)-related diseases are dominant late-onset genetic disorders that are manifested by progressive neurodegeneration, leading to behavioral and physical impairments. An increased body of evidence suggests that chromatin structure and epigenetic regulation are involved in disease pathology. PolyQ diseases often display an aberrant transcriptional regulation due to the disrupted function of histone-modifying complexes and altered interactions of the polyQ-extended proteins with chromatin-related factors. In this review we describe recent findings relating to the role of chromatin in polyQ diseases. We discuss the involvement of epigenetic-related factors and chromatin structure in genomic instability of CAG repeats; we describe changes in the expression and regulation of chromatin-related enzymes and in the levels and patterns of histone modifications in disease state; we illustrate the potential beneficial effects of different histone deacetylase (HDAC) inhibitors for the treatment of polyQ diseases, and we end by describing the potential use of human pluripotent stem cells and their differentiated derivatives for modeling polyQ diseases in vitro. Taken together, these accumulating studies strongly suggest that disrupted chromatin regulation may be directly involved with the pathophysiology of polyQ-related diseases.

Electrophysiological and contractile function of cardiomyocytes derived from human embryonic stem cells

Human embryonic stem cells have emerged as the prototypical source from which cardiomyocytes can be derived for use in drug discovery and cell therapy. However, such applications require that these cardiomyocytes (hESC-CMs) faithfully recapitulate the physiology of adult cells, especially in relation to their electrophysiological and contractile function. We review what is known about the electrophysiology of hESC-CMs in terms of beating rate, action potential characteristics, ionic currents, and cellular coupling as well as their contractility in terms of calcium cycling and contraction. We also discuss the heterogeneity in cellular phenotypes that arises from variability in cardiac differentiation, maturation, and culture conditions, and summarize present strategies that have been implemented to reduce this heterogeneity. Finally, we present original electrophysiological data from optical maps of hESC-CM clusters.

Functional neuronal cells generated by human parthenogenetic stem cells

Parent of origin imprints on the genome have been implicated in the regulation of neural cell type differentiation. The ability of human parthenogenetic (PG) embryonic stem cells (hpESCs) to undergo neural lineage and cell type-specific differentiation is undefined. We determined the potential of hpESCs to differentiate into various neural subtypes. Concurrently, we examined DNA methylation and expression status of imprinted genes. Under culture conditions promoting neural differentiation, hpESC-derived neural stem cells (hpNSCs) gave rise to glia and neuron-like cells that expressed subtype-specific markers and generated action potentials. Analysis of imprinting in hpESCs and in hpNSCs revealed that maternal-specific gene expression patterns and imprinting marks were generally maintained in PG cells upon differentiation. Our results demonstrate that despite the lack of a paternal genome, hpESCs generate proliferating NSCs that are capable of differentiation into physiologically functional neuron-like cells and maintain allele-specific expression of imprinted genes. Thus, hpESCs can serve as a model to study the role of maternal and paternal genomes in neural development and to better understand imprinting-associated brain diseases.

Derivation of vascular endothelial cells from human embryonic stem cells under GMP-compliant conditions: towards clinical studies in ischaemic disease

Revascularisation of ischaemic tissue remains an area of substantial unmet clinical need in cardiovascular disease. Strategies to induce therapeutic angiogenesis are therefore attractive. Our recent focus has been on human embryonic stem cell (hESC) strategies since hESC can be maintained in a pluripotent state or differentiated into any desired cell type, including endothelial cells (EC), under defined differentiation culture conditions. We recently published a protocol for non-good manufacturing practice (GMP) feeder- and serum-free hESC-EC-directed monolayer differentiation to vascular EC demonstrating the potential to generate hESC-derived EC in a GMP-compliant manner suitable for use in clinical trials. In this study we modified that laboratory protocol to GMP compliance. EC production was confirmed by flow cytometry, qRT-PCR and production of vascular structures in Matrigel®, yielding approximately 30 % mature VE-cadherin(+)/PECAM-1(+) cells using the GMP-compliant hESC line RC13. In conclusion, we have successfully demonstrated the production of vascular EC under GMP-compliant conditions suitable for clinical evaluation.

Comparison of cardiomyogenic potential among human ESC and iPSC lines

We recently reported that, following induction of clumps of pluripotent H1 human embryonic stem cells (hESCs) with activin-A and Bmp4 in defined medium for 5 days, widespread differentiation of rhythmically contracting cardiomyocytes occurs within 3-4 weeks. In this study, the same approach was used to assess whether human induced pluripotent stem cells (hiPSCs), which may theoretically provide an unlimited source of patient-matched cells for transplantation therapy, can similarly undergo cardiomyocyte differentiation. Differentiation of four pluripotent cell lines (H1 and H9 hESCs and C2a and C6a hiPSCs) was compared in parallel by monitoring rhythmic contraction, morphologic differentiation, and expression of cardiomyogenic genes. Based on expression of the cardiomyogenic lineage markers MESP1, ISL1, and NKX2-5, all four cell lines were induced into the cardiomyogenic lineage. However, in contrast to the widespread appearance of striations and rhythmic contractility seen in H9 and especially in H1 hESCs, both hiPSC lines exhibited poor terminal differentiation. These findings suggest that refined modes of generating hiPSCs, as well as of inducing cardiomyogenesis in them, may be required to fulfill their potential as agents of cardiac regeneration.

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.

Pluripotency in the embryo and in culture

Specific cells within the early mammalian embryo have the capacity to generate all somatic lineages plus the germline. This property of pluripotency is confined to the epiblast, a transient tissue that persists for only a few days. In vitro, however, pluripotency can be maintained indefinitely through derivation of stem cell lines. Pluripotent stem cells established from the newly formed epiblast are known as embryonic stem cells (ESCs), whereas those generated from later stages are called postimplantation epiblast stem cells (EpiSCs). These different classes of pluripotent stem cell have distinct culture requirements and gene expression programs, likely reflecting the dynamic development of the epiblast in the embryo. In this chapter we review current understanding of how the epiblast forms and relate this to the properties of derivative stem cells. We discuss whether ESCs and EpiSCs are true counterparts of different phases of epiblast development or are culture-generated phenomena. We also consider the proposition that early epiblast cells and ESCs may represent a naïve ground state without any prespecification of lineage choice, whereas later epiblasts and EpiSCs may be primed in favor of particular fates.

Highly pure and expandable PSA-NCAM-positive neural precursors from human ESC and iPSC-derived neural rosettes

Homogeneous culture of neural precursor cells (NPCs) derived from human pluripotent stem cells (hPSCs) would provide a powerful tool for biomedical applications. However, previous efforts to expand mechanically dissected neural rosettes for cultivation of NPCs remain concerns regarding non-neural cell contamination. In addition, several attempts to purify NPCs using cell surface markers have not demonstrated the expansion capability of the sorted cells. In the present study, we show that polysialic acid-neural cell adhesion molecule (PSA-NCAM) is detected in neural rosette cells derived from hPSCs, and employ PSA-NCAM as a marker for purifying expandable primitive NPCs from the neural rosettes. PSA-NCAM-positive NPCs (termed hNPC^PSA-NCAM+) were isolated from the heterogeneous cell population of mechanically harvested neural rosettes using magnetic-based cell sorting. The hNPC^PSA-NCAM+ extensively expressed neural markers such as Sox1, Sox2, Nestin, and Musashi-1 (80∼98% of the total cells) and were propagated for multiple passages while retaining their primitive characteristics in our culture condition. Interestingly, PSA-NCAM-negative cells largely exhibited characteristics of neural crest cells. The hNPC^PSA-NCAM+ showed multipotency and responsiveness to instructive cues towards region-specific neuronal subtypes in vitro. When transplanted into the rat striatum, hNPC^PSA-NCAM+ differentiated into neurons, astrocytes, and oligodendrocytes without particular signs of tumorigenesis. Furthermore, Ki67-positive proliferating cells and non-neural lineage cells were rarely detected in the grafts of hNPC^PSA-NCAM+ compared to those of neural rosette cells. Our results suggest that PSA-NCAM-mediated cell isolation provides a highly expandable population of pure primitive NPCs from hPSCs that will lend themselves as a promising strategy for drug screening and cell therapy for neurodegenerative disorders.

Role of microRNAs 99b, 181a, and 181b in the differentiation of human embryonic stem cells to vascular endothelial cells

MicroRNAs (miRNAs) are short noncoding RNAs, which post-transcriptionally regulate gene expression. miRNAs are transcribed as precursors and matured to active forms by a series of enzymes, including Dicer. miRNAs are important in governing cell differentiation, development, and disease. We have recently developed a feeder- and serum-free protocol for direct derivation of endothelial cells (ECs) from human embryonic stem cells (hESCs) and provided evidence of increases in angiogenesis-associated miRNAs (miR-126 and -210) during the process. However, the functional role of miRNAs in hESC differentiation to vascular EC remains to be fully interrogated. Here, we show that the reduction of miRNA maturation induced by Dicer knockdown suppressed hES-EC differentiation. A miRNA microarray was performed to quantify hES-EC miRNA profiles during defined stages of endothelial differentiation. miR-99b, -181a, and -181b were identified as increasing in a time- and differentiation-dependent manner to peak in mature hESC-ECs and adult ECs. Augmentation of miR-99b, -181a, and -181b levels by lentiviral-mediated transfer potentiated the mRNA and protein expression of EC-specific markers, Pecam1 and VE Cadherin, increased nitric oxide production, and improved hES-EC-induced therapeutic neovascularization in vivo. Conversely, knockdown did not impact endothelial differentiation. Our results suggest that miR-99b, -181a, and -181b comprise a component of an endothelial-miRNA signature and are capable of potentiating EC differentiation from pluripotent hESCs

Donor-dependent variations in hepatic differentiation from human-induced pluripotent stem cells

Hepatocytes generated from human induced pluripotent stem cells (hiPSCs) are unprecedented resources for pharmaceuticals and cell therapy. However, the in vitro directed differentiation of human pluripotent stem cells into mature hepatocytes remains challenging. Little attention has so far been paid to variations among hiPSC lines in terms of their hepatic differentiation. In the current study, we developed an improved hepatic differentiation protocol and compared 28 hiPSC lines originated from various somatic cells and derived using retroviruses, Sendai viruses, or episomal plasmids. This comparison indicated that the origins, but not the derivation methods, may be a major determinant of variation in hepatic differentiation. The hiPSC clones derived from peripheral blood cells consistently showed good differentiation efficiency, whereas many hiPSC clones from adult dermal fibroblasts showed poor differentiation. However, when we compared hiPSCs from peripheral blood and dermal fibroblasts from the same individuals, we found that variations in hepatic differentiation were largely attributable to donor differences, rather than to the types of the original cells. These data underscore the importance of donor differences when comparing the differentiation propensities of hiPSC clones.

Chondrogenic differentiation in vitro of murine two-factor induced pluripotent stem cells is comparable to murine embryonic stem cells

Differentiation of embryonic stem (ES) cells via embryoid bodies has been established as an appropriate model to study the development of various cell types in vitro. Here, we show that murine induced pluripotent stem (iPS) cells, reprogrammed by exogenous expression of the two transcription factors Oct4 and Klf4 (2F OK iPS), differentiate into chondrocytes in vitro characterized by the appearance of Alcian blue-stained nodules and the expression of cartilage-associated genes and proteins. Quantitatively, the chondrogenic differentiation potential of 2F OK iPS and ES cells was found to be similar. Further, we demonstrate the induction of chondrogenic iPS cell differentiation by certain members of the transforming growth factor-β family (BMP-2, TGF-β(1)). The number of Alcian blue-positive nodules and the expression of the cartilage marker molecule collagen type II increased after application of BMP-2, whereas simultaneous treatment with both BMP-2 and TGF-β(1) showed no significant effect on gene expression.

Human induced pluripotent stem cells and neurodegenerative disease: prospects for novel therapies

PURPOSE OF REVIEW

The lack of effective treatments for various neurodegenerative disorders has placed huge burdens on society. We review the current status in applying induced pluripotent stem cell (iPSC) technology for the cellular therapy, drug screening, and in-vitro modeling of neurodegenerative diseases.

RECENT FINDINGS

iPSCs are generated from somatic cells by overexpressing four reprogramming factors (Oct4, Sox2, Klf4, and Myc). Like human embryonic stem cells, iPSCs have features of self-renewal and pluripotency, and allow in-vitro disease modeling, drug screening, and cell replacement therapy. Disease-specific iPSCs were derived from patients of several neurodegenerative diseases, including Parkinson's disease, Alzheimer's disease, amyotrophic lateral sclerosis, and spinal muscular atrophy. Neurons differentiated from these iPSCs recapitulated the in-vivo phenotypes, providing platforms for drug screening. In the case of Parkinson's disease, iPSC-derived dopaminergic neurons gave positive therapeutic effect on a rodent Parkinson's disease model as a proof of principle in using iPSCs as sources of cell replacement therapy. Beyond iPSC technology, much effort is being made to generate neurons directly from dermal fibroblasts with neuron-specific transcription factors, which does not require making iPSCs as an intermediate cell type.

SUMMARY

We summarize recent progress in using iPSCs for modeling the progress and treatment of neurodegenerative diseases and provide evidence for future perspectives in this field.

Improved cell survival and paracrine capacity of human embryonic stem cell-derived mesenchymal stem cells promote therapeutic potential for pulmonary arterial hypertension

Although transplantation of adult bone marrow mesenchymal stem cells (BM-MSCs) holds promise in the treatment for pulmonary arterial hypertension (PAH), the poor survival and differentiation potential of adult BM-MSCs have limited their therapeutic efficiency. Here, we compared the therapeutic efficacy of human embryonic stem cell-derived MSCs (hESC-MSCs) with adult BM-MSCs for the treatment of PAH in an animal model. One week following monocrotaline (MCT)-induced PAH, mice were randomly assigned to receive phosphate-buffered saline (MCT group); 3.0×10(6) human BM-derived MSCs (BM-MSCs group) or 3.0×10(6) hESC-derived MSCs (hESC-MSCs group) via tail vein injection. At 3 weeks post-transplantation, the right ventricular systolic pressure (RVSP), degree of RV hypertrophy, and medial wall thickening of pulmonary arteries were lower=, and pulmonary capillary density was higher in the hESC-MSC group as compared with BM-MSC and MCT groups (all p < 0.05). At 1 week post-transplantation, the number of engrafted MSCs in the lungs was found significantly higher in the hESC-MSC group than in the BM-MSC group (all p < 0.01). At 3 weeks post-transplantation, implanted BM-MSCs were undetectable whereas hESC-MSCs were not only engrafted in injured pulmonary arteries but had also undergone endothelial differentiation. In addition, protein profiling of hESC-MSC- and BM-MSC-conditioned medium revealed a differential paracrine capacity. Classification of these factors into bioprocesses revealed that secreted factors from hESC-MSCs were preferentially involved in early embryonic development and tissue differentiation, especially blood vessel morphogenesis. We concluded that improved cell survival and paracrine capacity of hESC-MSCs provide better therapeutic efficacy than BM-MSCs in the treatment for PAH.

Distinct lineage specification roles for NANOG, OCT4, and SOX2 in human embryonic stem cells

Nanog, Oct4, and Sox2 are the core regulators of mouse (m)ESC pluripotency. Although their basic importance in human (h)ESCs has been demonstrated, the mechanistic functions are not well defined. Here, we identify general and cell-line-specific requirements for NANOG, OCT4, and SOX2 in hESCs. We show that OCT4 regulates, and interacts with, the BMP4 pathway to specify four developmental fates. High levels of OCT4 enable self-renewal in the absence of BMP4 but specify mesendoderm in the presence of BMP4. Low levels of OCT4 induce embryonic ectoderm differentiation in the absence of BMP4 but specify extraembryonic lineages in the presence of BMP4. NANOG represses embryonic ectoderm differentiation but has little effect on other lineages, whereas SOX2 and SOX3 are redundant and repress mesendoderm differentiation. Thus, instead of being panrepressors of differentiation, each factor controls specific cell fates. Our study revises the view of how self-renewal is orchestrated in hESCs.

Laser-Based Propagation of Human iPS and ES Cells Generates Reproducible Cultures with Enhanced Differentiation Potential

Proper maintenance of stem cells is essential for successful utilization of ESCs/iPSCs as tools in developmental and drug discovery studies and in regenerative medicine. Standardization is critical for all future applications of stem cells and necessary to fully understand their potential. This study reports a novel approach for the efficient, consistent expansion of human ESCs and iPSCs using laser sectioning, instead of mechanical devices or enzymes, to divide cultures into defined size clumps for propagation. Laser-mediated propagation maintained the pluripotency, quality, and genetic stability of ESCs/iPSCs and led to enhanced differentiation potential. This approach removes the variability associated with ESC/iPSC propagation, significantly reduces the expertise, labor, and time associated with manual passaging techniques and provides the basis for scalable delivery of standardized ESC/iPSC lines. Adoption of standardized protocols would allow researchers to understand the role of genetics, environment, and/or procedural effects on stem cells and would ensure reproducible production of stem cell cultures for use in clinical/therapeutic applications.

State of the art in stem cell research: human embryonic stem cells, induced pluripotent stem cells, and transdifferentiation

Stem cells divide by asymmetric division and display different degrees of potency, or ability to differentiate into various specialized cell types. Owing to their unique regenerative capacity, stem cells have generated great enthusiasm worldwide and represent an invaluable tool with unprecedented potential for biomedical research and therapeutic applications. Stem cells play a central role in the understanding of molecular mechanisms regulating tissue development and regeneration in normal and pathological conditions and open large possibilities for the discovery of innovative pharmaceuticals to treat the most devastating diseases of our time. Not least, their intrinsic characteristics allow the engineering of functional tissues for replacement therapies that promise to revolutionize the medical practice in the near future. In this paper, the authors present the characteristics of pluripotent stem cells and new developments of transdifferentiation technologies and explore some of the biomedical applications that this emerging technology is expected to empower.

Generation of Mouse STO Feeder Cell Lines That Confer Resistance to Several Types of Selective Drugs

Feeder cells are generally required for establishment and maintenance of embryonic stem (ES)/induced pluripotent stem (iPS) cells. Increased demands for generation of those cells carrying various types of vectors (i.e., KO vectors and transgenes) also require feeder cells that confer resistance to any types of preexisting selective drugs. Unfortunately, the use of the feeders that are resistant to various drugs appears to be limited to a few laboratories. Here we generated a set of gene-engineered STO feeder cells that confer resistance to several commercially available drugs. The STO cells, which have long been used as a feeder for mouse ES and embryonal carcinoma (EC) cells, were transfected with pcBIH [carrying bleomycin resistance gene (ble) and hygromycin B phosphotransferase gene (Hyg)], pcBIP [carrying ble and puromycin resistance gene (puro)], or pcBSN [carrying ble and neomycin resistance gene (neo)]. The resulting stably transfectants (termed SHB for pcBIH, SPB for pcBIP, and SNB for pcBSN) exhibited bleomycin/hygromycin, bleomycin/puromycin, or bleomycin/neomycin, as expected. The morphology of these cells passaged over 18 generations was indistinguishable from that of parental STO cells. Of isolated clones, the SHB3, SPB3, and SNB2 clones successfully supported the growth of mouse ES cells in an undifferentiated state, when coculture was performed. PCR analysis revealed the presence of the selective markers in these clones, as expected. These SHB3, SPB3, and SNB2 cells will thus be useful for the acquisition and maintenance of genetically manipulated ES/iPS cells.

Human pre-implantation embryo development

Understanding human pre-implantation development has important implications for assisted reproductive technology (ART) and for human embryonic stem cell (hESC)-based therapies. Owing to limited resources, the cellular and molecular mechanisms governing this early stage of human development are poorly understood. Nonetheless, recent advances in non-invasive imaging techniques and molecular and genomic technologies have helped to increase our understanding of this fascinating stage of human development. Here, we summarize what is currently known about human pre-implantation embryo development and highlight how further studies of human pre-implantation embryos can be used to improve ART and to fully harness the potential of hESCs for therapeutic goals.

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.

Procedures for derivation and characterisation of human embryonic stem cells from Odense, Denmark

In 1998, a development occurred in stem cell biology with the first report of the derivation of a human embryonic stem cell (hESC) line. Since then a number of techniques have been used to derive and characterise hESCs. Here, we describe the derivation methods used by our laboratory for isolation of the ICM by immunosurgery and outgrowth of the whole blastocyst. We have added protocols for routine culture, passaging and cryopreservation of our hESC lines as well as the methods we have used for characterisation (flow cytometry, karyotyping, immunocytochemistry, in vitro and in vivo differentiation). Additionally, we have included gene sequences for PCR and an antibody list for immunocytochemistry.

A cell surfaceome map for immunophenotyping and sorting pluripotent stem cells

Induction of a pluripotent state in somatic cells through nuclear reprogramming has ushered in a new era of regenerative medicine. Heterogeneity and varied differentiation potentials among induced pluripotent stem cell (iPSC) lines are, however, complicating factors that limit their usefulness for disease modeling, drug discovery, and patient therapies. Thus, there is an urgent need to develop nonmutagenic rapid throughput methods capable of distinguishing among putative iPSC lines of variable quality. To address this issue, we have applied a highly specific chemoproteomic targeting strategy for de novo discovery of cell surface N-glycoproteins to increase the knowledge-base of surface exposed proteins and accessible epitopes of pluripotent stem cells. We report the identification of 500 cell surface proteins on four embryonic stem cell and iPSCs lines and demonstrate the biological significance of this resource on mouse fibroblasts containing an oct4-GFP expression cassette that is active in reprogrammed cells. These results together with immunophenotyping, cell sorting, and functional analyses demonstrate that these newly identified surface marker panels are useful for isolating iPSCs from heterogeneous reprogrammed cultures and for isolating functionally distinct stem cell subpopulations.

Stemness characteristics and osteogenic potential of sheep amniotic epithelial cells

We set out to characterize stemness properties and osteogenic potential of sheep AEC (amniotic epithelial cells). AEC were isolated from 3-month-old fetuses and expanded in vitro for 12 passages. The morphology, surface markers, stemness markers and osteogenic differentiation were inspected after 1, 6 and 12 passages of expansion, with an average doubling time of 24 h. AEC clearly expressed the stemness markers Oct-3/4 (octamer-binding protein-3/4), Nanog, Sox2 and TERT (telomerase reverse transcriptase) and displayed low levels of global DNA methylation. Culture had moderate effects on cell conditions; some adhesion molecules progressively disappeared from the cell surface, and the expression of Sox2 and TERT was slightly reduced while Nanog increased. No changes occurred in the levels of DNA methylation. Cells organized in 3D spheroids were used for IVD (in vitro differentiation). Within these structures the cells developed a complex intercellular organization that involved extensive intercellular coupling despite continuous cell migration. Marked deposition of calcein in the ECM (extracellular matrix), increased ALP (alkaline phosphatase) activity, expression of bone-related genes (osteocalcin) and the matrix mineralization shown by Alizarin Red staining demonstrate that AEC can undergo rapid and extensive osteogenic differentiation. AEC introduced in experimental bone lesions survived in the site of implantation for 45 days and supported consistent bone neoformation, thus showing promising potential applications in osteogenic regenerative medicine.

Differentiation and enrichment of cardiomyocytes from human pluripotent stem cells

Human cardiomyocytes derived from pluripotent stem cells hold great promise for cardiac cell therapy, disease modeling, drug discovery, and the study of developmental biology. Reaching these potentials fully requires the development of methods that enable efficient and robust generation of cardiomyocytes with expected characteristics. This review summarizes and discusses up-to-date methods that have been used to derive and enrich human cardiomyocytes from pluripotent stem cells, provides a brief overview of in vitro and in vivo characterization of these cardiomyocytes, and considers future advancement needed to further harness the power of these cells.

Endothelial cell co-culture mediates maturation of human embryonic stem cell to pancreatic insulin producing cells in a directed differentiation approach

Embryonic stem cells (ESC) have two main characteristics: they can be indefinitely propagated in vitro in an undifferentiated state and they are pluripotent, thus having the potential to differentiate into multiple lineages. Such properties make ESCs extremely attractive for cell based therapy and regenerative treatment applications. However for its full potential to be realized the cells have to be differentiated into mature and functional phenotypes, which is a daunting task. A promising approach in inducing cellular differentiation is to closely mimic the path of organogenesis in the in vitro setting. Pancreatic development is known to occur in specific stages, starting with endoderm, which can develop into several organs, including liver and pancreas. Endoderm induction can be achieved by modulation of the nodal pathway through addition of Activin A in combination with several growth factors. Definitive endoderm cells then undergo pancreatic commitment by inhibition of sonic hedgehog inhibition, which can be achieved in vitro by addition of cyclopamine. Pancreatic maturation is mediated by several parallel events including inhibition of notch signaling; aggregation of pancreatic progenitors into 3-dimentional clusters; induction of vascularization; to name a few. By far the most successful in vitro maturation of ESC derived pancreatic progenitor cells have been achieved through inhibition of notch signaling by DAPT supplementation. Although successful, this results in low yield of the mature phenotype with reduced functionality. A less studied area is the effect of endothelial cell signaling in pancreatic maturation, which is increasingly being appreciated as an important contributing factor in in-vivo pancreatic islet maturation. The current study explores such effect of endothelial cell signaling in maturation of human ESC derived pancreatic progenitor cells into insulin producing islet-like cells. We report a multi-stage directed differentiation protocol where the human ESCs are first induced towards endoderm by Activin A along with inhibition of PI3K pathway. Pancreatic specification of endoderm cells is achieved by inhibition of sonic hedgehog signaling by Cyclopamine along with retinoid induction by addition of Retinoic Acid. The final stage of maturation is induced by endothelial cell signaling achieved by a co-culture configuration. While several endothelial cells have been tested in the co-culture, herein we present our data with rat heart microvascular endothelial Cells (RHMVEC), primarily for the ease of analysis.

Teratoma formation of human embryonic stem cells in three-dimensional perfusion culture bioreactors

Teratoma formation in mice is today the most stringent test for pluripotency that is available for human pluripotent cells, as chimera formation and tetraploid complementation cannot be performed with human cells. The teratoma assay could also be applied for assessing the safety of human pluripotent cell-derived cell populations intended for therapeutic applications. In our study we examined the spontaneous differentiation behaviour of human embryonic stem cells (hESCs) in a perfused 3D multi-compartment bioreactor system and compared it with differentiation of hESCs and human induced pluripotent cells (hiPSCs) cultured in vitro as embryoid bodies and in vivo in an experimental mouse model of teratoma formation. Results from biochemical, histological/immunohistological and ultrastuctural analyses revealed that hESCs cultured in bioreactors formed tissue-like structures containing derivatives of all three germ layers. Comparison with embryoid bodies and the teratomas revealed a high degree of similarity of the tissues formed in the bioreactor to these in the teratomas at the histological as well as transcriptional level, as detected by comparative whole-genome RNA expression profiling. The 3D culture system represents a novel in vitro model that permits stable long-term cultivation, spontaneous multi-lineage differentiation and tissue formation of pluripotent cells that is comparable to in vivo differentiation. Such a model is of interest, e.g. for the development of novel cell differentiation strategies. In addition, the 3D in vitro model could be used for teratoma studies and pluripotency assays in a fully defined, controlled environment, alternatively to in vivo mouse models.

A survey of parameters involved in the establishment of new lines of human embryonic stem cells

Since the derivation of the first human embryonic stem cell (hESC) lines by Thomson and coworkers in 1998, more than 1,200 different hESC lines have been established worldwide. Nevertheless, there is still a recognized interest in the establishment of new lines of hESC, particularly from HLA types and ethnic groups currently underrepresented among the available lines. The methodology of hESC derivation has evolved significantly since 1998, when human LIF (hLIF) was used for maintenance of pluripotency. However, there are a number of different strategies for the several steps involved in establishing a new line of hESC. Here we make a survey of the most relevant parameters used between 1998 and 2010 for the derivation of the 375 hESC lines deposited in two international stem cell registries, and able to form teratomas in immunocompromised mice. Although we identify some trends in the methodology for establishing hESC lines, our data reveal a much greater heterogeneity of strategies than what is used for derivation of murine ESC lines, indicating that optimum conditions have not been consolidated yet, and thus, hESC establishment is still an evolving field of research.

Chemical strategies for stem cell biology and regenerative medicine

Stem cell technology holds great promises for the cures of devastating diseases, injuries, aging, and even cancers as it is applied in regenerative medicine. Recent breakthroughs in the development of induced pluripotent stem cell techniques and efficient differentiation strategies have generated tremendous enthusiasm and efforts to explore the therapeutic potential of stem cells. Small molecules, which target specific signaling pathways and/or proteins, have been demonstrated to be particularly valuable for manipulating cell fate, state, and function. Such small molecules not only are useful in generating desired cell types in vitro for various applications but also could be further developed as conventional therapeutics to stimulate patients' endogenous cells to repair and regenerate in vivo. Here, we focus on recent progress in the use of small molecules in stem cell biology and regenerative medicine.

Investigating cellular identity and manipulating cell fate using induced pluripotent stem cells

Induced pluripotent stem (iPS) cells, obtained from reprogramming somatic cells by ectopic expression of a defined set of transcription factors or chemicals, are expected to be used as differentiated cells for drug screening or evaluations of drug toxicity and cell replacement therapies. As pluripotent stem cells, iPS cells are similar to embryonic stem (ES) cells in morphology and marker expression. Several types of iPS cells have been generated using combinations of reprogramming molecules and/or small chemical compounds from different types of tissues. A comprehensive approach, such as global gene or microRNA expression analysis and whole genomic DNA methylation profiling, has demonstrated that iPS cells are similar to their embryonic counterparts. Considering the substantial variation among iPS cell lines reported to date, the safety and therapeutic implications of these differences should be thoroughly evaluated before they are used in cell therapies. Here, we review recent research defining the concept of standardization for iPS cells, their ability to differentiate and the identity of the differentiated cells.

miR-371-3 expression predicts neural differentiation propensity in human pluripotent stem cells

The use of pluripotent stem cells in regenerative medicine and disease modeling is complicated by the variation in differentiation properties between lines. In this study, we characterized 13 human embryonic stem cell (hESC) and 26 human induced pluripotent stem cell (hiPSC) lines to identify markers that predict neural differentiation behavior. At a general level, markers previously known to distinguish mouse ESCs from epiblast stem cells (EPI-SCs) correlated with neural differentiation behavior. More specifically, quantitative analysis of miR-371-3 expression prospectively identified hESC and hiPSC lines with differential neurogenic differentiation propensity and in vivo dopamine neuron engraftment potential. Transient KLF4 transduction increased miR-371-3 expression and altered neurogenic behavior and pluripotency marker expression. Conversely, suppression of miR-371-3 expression in KLF4-transduced cells rescued neural differentiation propensity. miR-371-3 expression level therefore appears to have both a predictive and a functional role in determining human pluripotent stem cell neurogenic differentiation behavior.

Derivation of novel genetically diverse human embryonic stem cell lines

Human embryonic stem cells (hESCs) have the potential to revolutionize many biomedical fields ranging from basic research to disease modeling, regenerative medicine, drug discovery, and toxicity testing. A multitude of hESC lines have been derived worldwide since the first 5 lines by Thomson et al. 13 years ago, but many of these are poorly characterized, unavailable, or do not represent desired traits, thus making them unsuitable for application purposes. In order to provide the scientific community with better options, we have derived 12 new hESC lines at New York University from discarded genetically normal and abnormal embryos using the latest techniques. We examined the genetic status of the NYUES lines in detail as well as their molecular and cellular features and DNA fingerprinting profile. Furthermore, we differentiated our hESCs into the tissues most affected by a specific condition or into clinically desired cell types. To our knowledge, a number of characteristics of our hESCs have not been previously reported, for example, mutation for alpha thalassemia X-linked mental retardation syndrome, linkage to conditions with a genetic component such as asthma or poor sperm morphology, and novel combinations of ethnic backgrounds. Importantly, all of our undifferentiated euploid female lines tested to date did not show X chromosome inactivation, believed to result in superior potency. We continue to derive new hESC lines and add them to the NIH registry and other registries. This should facilitate the use of our hESCs and lead to advancements for patient-benefitting applications.

The promise of induced pluripotent stem cells in research and therapy

The field of stem-cell biology has been catapulted forward by the startling development of reprogramming technology. The ability to restore pluripotency to somatic cells through the ectopic co-expression of reprogramming factors has created powerful new opportunities for modelling human diseases and offers hope for personalized regenerative cell therapies. While the field is racing ahead, some researchers are pausing to evaluate whether induced pluripotent stem cells are indeed the true equivalents of embryonic stem cells and whether subtle differences between these types of cell might affect their research applications and therapeutic potential.