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PubMed1995

Myosin heavy chain expression in contracting myocytes isolated during embryonic stem cell cardiogenesis.

Mouse embryonic stem (ES) cells are totipotent cells derived from the inner cell mass of the preimplantation blastocyst and are capable of differentiating in vitro into cardiac myocytes. Attached cultures of differentiating ES cells were established to document the timing of contractile development by microscopic observation and to permit the microdissection of cardiac myocytes from culture. The onset of spontaneous contraction varied markedly in differentiation culture, with contraction being maintained on average for 9 days (range, 1 to 75 days). Indirect immunofluorescence in microscopy showed that myosin expression was localized to the contracting cardiac myocytes in culture. Myosin heavy chain (MHC) isoform expression in microdissected ES cell-derived cardiac myocytes was determined by means of sodium dodecyl sulfate-polyacryl-amide gel electrophoresis. The distribution of MHC isoform expression in isolated ES cell cardiac myocytes was as follows: 27% expressed the beta-MHC isoform, 33% expressed both the alpha- and beta-MHC isoforms, and 40% expressed the alpha-MHC isoform. MHC phenotype was correlated to the duration of continuous contractile activity of the myocytes. Myocytes that had just initiated spontaneous contractile activity predominantly expressed the beta-MHC (average days of contraction before isolation, 2.5 +/- 0.7). The alpha-MHC isoform was detected after mouse prolonged contractile activity in vitro (1 to 5 weeks). A strong correlation was obtained between MHC phenotype and days of contraction of the cardiac myocyte preparations isolated from ES cell cultures (r = .93). The apparent transition in MHC isoform expression during ES cell differentiation parallels the beta- to alpha-MHC isoform transition characteristic of murine cardiac development in vivo. These findings are evidence that ES cell cardiac myocyte differentiation follows the normal developmental program of murine cardiogenesis.

Animals↗

PubMed2004

Beta-catenin signaling is required for neural differentiation of embryonic stem cells.

Culture of embryonic stem (ES) cells at high density inhibits both beta-catenin signaling and neural differentiation. ES cell density does not influence beta-catenin expression, but a greater proportion of beta-catenin is targeted for degradation in high-density cultures. Moreover, in high-density cultures, beta-catenin is preferentially localized to the membrane further reducing beta-catenin signaling. Increasing beta-catenin signaling by treatment with Wnt3a-conditioned medium, by overexpression of beta-catenin, or by overexpression of a dominant-negative form of E-cadherin promotes neurogenesis. Furthermore, beta-catenin signaling is sufficient to induce neurogenesis in high-density cultures even in the absence of retinoic acid (RA), although RA potentiates the effects of beta-catenin. By contrast, RA does not induce neurogenesis in high-density cultures in the absence of beta-catenin signaling. Truncation of the armadillo domain of beta-catenin, but not the C terminus or the N terminus, eliminates its proneural effects. The proneural effects of beta-catenin reflect enhanced lineage commitment rather than proliferation of neural progenitor cells. Neurons induced by beta-catenin overexpression either alone or in association with RA express the caudal neuronal marker Hoxc4. However, RA treatment inhibits the beta-catenin-mediated generation of tyrosine hydroxylase-positive neurons, suggesting that not all of the effects of RA are dependent upon beta-catenin signaling. These observations suggest that beta-catenin signaling promotes neural lineage commitment by ES cells, and that beta-catenin signaling may be a necessary co-factor for RA-mediated neuronal differentiation. Further, enhancement of beta-catenin signaling with RA treatment significantly increases the numbers of neurons generated from ES cells, thus suggesting a method for obtaining large numbers of neural species for possible use in for ES cell transplantation.

Animals↗

PubMed2005

Hematopoietic and endothelial development of mouse embryonic stem cells in culture.

Embryonic stem (ES) cells differentiate efficiently in vitro and give rise to many different somatic cell types. Hematopoietic progenitors present within differentiated ES cells (embryoid bodies, EBs) can be identified by replating EB cells into semisolid media with hematopoietic growth factors. The developmental kinetics of various hematopoietic lineage precursors within EBs and molecular and cellular studies of these cells have suggested that the sequence of events leading to the onset of hematopoiesis within EBs is similar to that found within the mouse embryo. Thus, the in vitro differentiation model of ES cells provides a unique opportunity to study onset mechanisms involved in hematopoietic development.

Animals↗

PubMed2006

Internal standards in differentiating embryonic stem cells in vitro.

Embryonic stem (ES) cell lines are important for use in developmental biology studies, and because these cells are totipotent, they may provide a much-needed source of differentiated cells for certain therapeutic applications. The phenotype of the ES cell in culture is often assessed by (semi)quantitative RNA analyses. In such cases, it is critical to use appropriate internal standards to correct for experimentally induced sources of error. This is particularly true for ES cell differentiation because it is heterogeneous in nature. We describe protocols for determining the suitability of housekeeping genes to act as internal controls in differentiating ES cell cultures. Such assessment is needed for every experimental condition under investigation. The protocol focuses on polymerase chain reaction; however, the principle and experimental design are applicable to any (semi)quantitative RNA assay.

Animals↗

PubMed2006

DNA damage response and mutagenesis in mouse embryonic stem cells.

Mutation in embryonic stem (ES) cells can potentially compromise multiple cell lineages and affect the well-being of subsequent generations. Thus, ES cells require sensitive mechanisms to maintain genomic integrity. One mechanism involves suppression of mutation. A complementary mechanism is to regulate the cell cycle checkpoint and facilitate cell death. Here, we describe the detailed protocols we have used to investigate DNA damage response and mutagenesis in mouse ES cells.

Adenine Phosphoribosyltransferase↗

PubMed2006

Generation and characterization of monkey embryonic stem cells.

Nonhuman primate embryonic stem (ES) cells are very important for preclinical research of the medical application of human ES cells. Because primate ES cells show significant differences from mouse ES cells, we have been optimizing protocols for the establishment and maintenance of monkey ES cells. The latest methods for derivation and culture of cynomolgus monkey ES cells are described in detail.

Animals↗

PubMed2002

Analysis of different promoter systems for efficient transgene expression in mouse embryonic stem cell lines.

Mouse embryonic stem (ES) cells are derived from the inner cell mass of the preimplantation embryo and have the developmental capacity to generate all cell types of the body. Combined with efficient genetic manipulation and in vitro differentiation procedures, ES cells are a useful system for the molecular analysis of developmental pathways. We analyzed and compared the transcriptional activities of a cellular polypeptide chain elongation factor 1 alpha (EF), a cellular-virus hybrid (cytomegalo-virus [CMV] immediate early enhancer fused to chicken beta-actin [CBA]), and a viral CMV promoter system in two ES cell lines. When transiently transfected, the EF and CBA promoters robustly drove reporter gene expression, while the CMV promoter was inactive. We also demonstrated that the EF and CBA promoters effectively drove gene expression in different stages of cell development: naïve ES cells, embryoid bodies (EBs), and neuronal precursor cells. In contrast, the CMV promoter did not have transcriptional activity in either ES cells or EB but had significant activity once ES cells differentiated into neuronal precursors. Our data show that individual promoters have different abilities to express reporter gene expression in the ES and other cell types tested.

Actins↗

PubMed2004

Controlled, scalable embryonic stem cell differentiation culture.

Embryonic stem (ES) cells are of significant interest as a renewable source of therapeutically useful cells. ES cell aggregation is important for both human and mouse embryoid body (EB) formation and the subsequent generation of ES cell derivatives. Aggregation between EBs (agglomeration), however, inhibits cell growth and differentiation in stirred or high-cell-density static cultures. We demonstrate that the agglomeration of two EBs is initiated by E-cadherin-mediated cell attachment and followed by active cell migration. We report the development of a technology capable of controlling cell-cell interactions in scalable culture by the mass encapsulation of ES cells in size-specified agarose capsules. When placed in stirred-suspension bioreactors, encapsulated ES cells can be used to produce scalable quantities of hematopoietic progenitor cells in a controlled environment.

Animals↗

PubMed2002

In vivo differentiation of mouse embryonic stem cells into hepatocytes.

Embryonic stem (ES) cells have been regarded as a powerful resource for cell replacement therapy. In recent reports mouse ES cells have been successfully applied in the treatment of spinal cord injury, hereditary myelin disorder of the central nervous system, and diabetes mellitus. Another type of disease that could benefit from the availability of stem cell therapy is liver disease. However, for this potential to be realized, it is necessary to demonstrate the differentiation of ES cells into hepatocytes. To demonstrate the in vivo differentiation potential of mouse ES cells, we injected ES cells into the spleen of immunosuppressed nude mice. Histological analysis of teratomas derived from injected ES cells revealed that some areas contained typical hepatocytes arranged in a sinusoidal structure. The hepatic nature of these cells was further confirmed by showing that transcripts of liver-specific genes were present in the differentiated teratoma using reverse transcriptase-polymerase chain reaction and immunohistochemistry using several liver-specific antibodies including HEP-PAR, phenylalanine hydroxylase, and mouse N-system aminotransferase to identify the respective proteins in the differentiated hepatocytes. This is the first demonstration that mouse ES cells can differentiate in vivo into a mixed population of hepatocytes of varying maturity. This finding extends the potential use of ES cells in the cell replacement therapy by including its possible application for treating liver diseases.

Animals↗

PubMed2005

Efficient derivation of new human embryonic stem cell lines.

Human embryonic stem (hES) cells, unlike most cells derived from adult or fetal human tissues, represent a potentially unlimited source of various cell types for basic clinical research. To meet the increased demand for characterized hES cell lines, we established and characterized nine new lines obtained from frozen-thawed pronucleus-stage embryos. In addition, we improved the derivation efficiency from inner cell masses (to 47.4%) and optimized culture conditions for undifferentiated hES cells. After these cell lines had been maintained for over a year in vitro, they were characterized comprehensively for expression of markers of undifferentiated hES cells, karyotype, and in vitro/in vivo differentiation capacity. All of the cell lines were pluripotent, and one cell line was trisomic for chromosome 3. Improved culture techniques for hES cells should make them a good source for diverse applications in regenerative medicine, but further investigation is needed of their basic biology.

Animals↗

PubMed2003

Staurosporine is a potent activator of neuronal, glial, and "CNS stem cell-like" neurosphere differentiation in murine embryonic stem cells.

Staurosporine (STS), a broad spectrum protein kinase inhibitor, was previously shown to induce neurite outgrowth in several neuroblastoma cell lines. However, data on the neurotrophic potential of this alkaloid in embryonic stem cell systems were not available. Therefore, three mouse ES cell lines, IB10, RW4, and Bruce 4, were induced to enter neurogenesis in culture at low concentrations of STS. These cells differentiated into epidermal growth factor-responsive neural precursor cells, formed neurospheres, and further developed to neurons and astrocytes. The clonally derived neurospheres consisted of multipotent cells which exhibited some of the classical characteristics of early CNS stem cells and could be propagated in vitro. STS was antagonistic in several ways to retinoic acid (RA), a vitamin A metabolite, which promotes neuritogenesis. Results from RT-PCR experiments and inhibition studies with RA provided evidence that staurosporine exerted its neurotrophic effects through the induction of very late levels of the nerve growth factor and protein kinase C neurogenesis pathways.

Animals↗

PubMed2006

Induction dopamine releasing cells from mouse embryonic stem cells and their long-term culture.

Cell transplantation therapy using dopaminergic neurons derived from embryonic stem (ES) cells for the treatment of Parkinson's disease has been proposed as one of the major applications for stem cell-based therapy. However, the low collection efficiency of neurons from a culture dish and the rejection of cells after transplantation are expected to limit their future clinical applications. To overcome these problems, we examined the induction of neurogenesis of ES cells under free-floating conditions and microencapsulation of the obtained cell aggregates into an agarose hydrogel. Cell aggregates from ES cells were cultured in various media under the free-floating condition. Immunohistochemical staining for tyrosine hydroxylase (TH) and RT-PCR analyses for TH and Nurr1 showed that dopaminergic neurons were induced in ES cell aggregates cultured in a 1:2 mixture of conditioned medium of PA6 stromal cells and Glasgow minimum essential medium (GMEM) after 16 days in culture. The cell aggregates could be collected and were encased within agarose microcapsules without loss of dopaminergic neurons. The cell aggregates with/without microencapsulation were maintained in CM/GMEM for an additional period. KCl stimulation assays were done at day 23, 30, 37, 44, 51, and 58 to examine dopamine release. Dopamine release abilities were well maintained during 58 days of observation. Amounts of dopamine release from encapsulated cell aggregates were slightly higher than those of unencapsulated cell aggregates from day 16 to 58. Although efficacy for immunoisolation of the agarose microcapsules still remains for future in vivo studies, microencapsulation did not adversely affect viability and functions of the dopamine releasing ES cell progeny.

Animals↗

PubMed2003

Cardiomyocytes derived from embryonic stem cells resemble cardiomyocytes of the embryonic heart tube.

OBJECTIVE: After formation of the linear heart tube a chamber-specific program of gene expression becomes active that underlies the formation of the chamber myocardium. To assess whether this program is recapitulated in in vitro differentiated embryonic stem cells, we performed qualitative and quantitative analyses of cardiogenesis in vivo and in vitro. METHODS: Gene expression profiles were made by in situ hybridisation and real-time PCR and electrophysiological profiles by patch clamp analyses of cardiomyocytes derived from time series of differentiating HM1 mouse embryonic stem cells and from embryonic and adult mouse hearts. RESULTS: In embryoid bodies the in situ patterns of expression of alpha-myosin heavy chain, myosin light chain 2a and sarcoendoplasmic reticulum calcium ATPase 2a were similar to that of the heart muscle-specific marker gene cardiac troponin I. Myosin light chain 2v was expressed in part of the cardiac troponin I-expressing area, indicating heterogeneity within the cardiac cell population. Atrial natriuretic factor expression, indicative of the chamber-type program, could only very occasionally be detected by in situ hybridisation. Quantitative reverse transcriptase PCR showed that all cardiac genes, most notably atrial natriuretic factor, were expressed at relatively low levels, similar to those in embryonic hearts at embryonic day 8.75-9. Analysis of the electrophysiological characteristics of embryonic stem cell-derived cardiomyocytes showed an increase of the upstroke velocity and a shorter duration of the action potential during prolonged differentiation in vitro. When embryonic mouse heart compartments of embryonic day 12.5 were used as a reference, the electrophysiological characteristics of a substantial part of the embryonic stem cell-derived cardiomyocytes were most reminiscent to those observed in the embryonic outflow tract. CONCLUSION: Together, these data suggest that most cardiomyocytes acquired by differentiation of embryonic stem cells maintain a phenotype reminiscent of that of the cardiomyocytes of the primary heart tube, and hardly any myocytes develop a chamber myocardial phenotype.

Action Potentials↗

PubMed2006

Gene trapping in embryonic stem cells.

Gene trapping in embryonic stem cells (ESCs) generates random, sequence-tagged insertional mutations, which can often report the gene expression pattern of the mutated gene. This mutagenesis strategy has often been coupled to expression or function-based assays in gene discovery screens. The availability of the mouse genome sequence has shifted gene trapping from a gene discovery platform to a high-throughput mutagenesis platform. At present, a concerted worldwide effort is underway to develop a library of loss-of-function mutations in all mouse genes. The International Gene Trap Consortium (IGTC) is leading the way by making a first pass of the genome by random mutagenesis before a high-throughput gene targeting program takes over. In this chapter, we provide a methods guidebook to exploring and using the IGTC resource, explain the different kinds of vectors and insertions that reside in the different libraries, and provide advice and methods for investigators to design novel expression-based "cottage industry" screens.

Animals↗

PubMed1995

The development of haematopoietic cells is biased in embryonic stem cell chimaeras.

The haematopoietic development of embryonic stem (ES) cell injection chimaeras was analysed using beta-galactosidase expression from an X-linked transgene as a marker to distinguish the ES-derived cell population from the host cells. The number of cells in the different haematopoietic cell subpopulations was determined by flow cytometry. When the proportions of ES-derived cells in the antigen-positive lineages were compared to the ES cell contribution to all cells in teh organs, we found an unexpected bias in the haematopoietic differentiation of ES-derived cells. ES descendants were overrepresented in the bone marrow B lymphoid cell population and the splenic myeloid cells but were underrepresented in the CD4-positive T lymphoid cells in the spleen. These results were obtained by comparison with control female animals that were X chromosome mosaic for beta-galactosidase expression. These findings of uneven contribution to haematopoietic development by ES cells indicate that the commitment of ES cell descendants may be different from that of the host cells.

Animals↗

PubMed2002

Comparative gene expression in hematopoietic progenitor cells derived from embryonic stem cells.

OBJECTIVE: The aim of this study was to characterize at the molecular level the hematopoietic progenitor cells derived from rhesus monkey embryonic stem (ES) cell differentiation. MATERIALS AND METHODS: We purified CD34(+) and CD34(+)CD38(-) cells from rhesus monkey ES cell cultures and examined the expression of a variety of genes associated with hematopoietic development, by semiquantitative polymerase chain reaction analysis. For comparison, we examined cell preparations from fresh or cultured rhesus monkey bone marrow (BM) and from mouse ES cells and BM. RESULTS: We observed a high degree of similarity in the expression patterns of these genes, with only a few exceptions. Most notably, the message of the flt3 gene was undetectable in rhesus monkey ES cell-derived CD34(+) and CD34(+)CD38(-) cells, whereas substantial flt3 expression was observed in the corresponding cells from fresh BM and in CD34(+) cells from cultured BM. The integrin alphaL and interleukin-6 (IL-6) receptor genes also were expressed in CD34(+)CD38(-) cells from BM, but there was little or no expression of these genes in CD34(+)CD38(-) cells derived from ES cells. Parallel analyses, using CD34(+)Lin(-) cells derived from murine ES cell cultures, showed no apparent expression of flt3, integrin alphaL, or IL-6 receptor, whereas corresponding cell preparations isolated from mouse BM expressed high levels of all of these genes. CONCLUSIONS: ES cell-derived hematopoietic progenitors, both from the rhesus monkey and from the mouse, exhibited the same alterations in gene expression compared with BM-derived cells from these animals. These observations could reflect the presence of different subpopulations in the cell fractions that were compared, or they may represent altered biologic properties of ES cell-derived hematopoietic stem cells.

ADP-ribosyl Cyclase↗

PubMed1989

Expression of multiple heparin-binding growth factor species by murine embryonal carcinoma and embryonic stem cells.

Culture medium conditioned by P19 embryonal carcinoma (EC) cells contains potent mitogenic activity which is markedly potentiated when the medium is conditioned in the presence of heparin. Fractionation of P19 medium conditioned in the presence of heparin reveals the existence of two biochemically distinct growth factor species both of which exhibit high affinity for immobilised heparin and significant activity as amphibian mesoderm-inducing agents. One of the species is recovered as a single polypeptide of apparent Mr = 15,000. This molecule is immunologically related to the protein product of the human K-FGF proto-oncogene. Transcripts derived from the murine K-FGF gene are also expressed by both differentiated and undifferentiated EC cells and embryonic stem cells. The second heparin-binding growth factor is recovered as a complex of four polypeptides, the largest of which has an apparent Mr = 17,000. This agent is immunologically and biochemically distinct from both acidic and basic fibroblast growth factor as well as K-FGF, and represents the predominant mitogenic activity in EC-cell-conditioned medium.

Animals↗

PubMed2004

Osteogenic Cells Derived From Embryonic Stem Cells Produced Bone Nodules in Three-Dimensional Scaffolds.

An approach for 3D bone tissue generation from embryonic stem (ES) cells was investigated. The ES cells were induced to differentiate into osteogenic precursors, capable of proliferating and subsequently differentiating into bone-forming cells. The differentiated cells and the seeded scaffolds were characterized using von Kossa and Alizarin Red staining, electron microscopy, and RT-PCR analysis. The results demonstrated that ES-derived bone-forming cells attached to and colonized the biocompatible and biodegradable scaffolds. Furthermore, these cells produced bone nodules when grown for 3-4 weeks in mineralization medium containing ascorbic acid and beta-glycerophosphate both in tissue culture plates and in scaffolds. The differentiated cells also expressed osteospecific markers when grown both in the culture plates and in 3D scaffolds. Osteogenic cells expressed alkaline phosphatase, osteocalcin, and osteopontin, but not an ES cell-specific marker, oct-4. These findings suggest that ES cell can be used for in vitro tissue engineering and cultivation of graftable skeletal structures.

Journal Article↗