PubMed Health⌕ Search

SEARCH · PubMed Health

Results for “Embryonic stem cells”

Explore indexed PubMed citations for clinical trials, systematic reviews and public health research. Read source abstracts and follow each citation to its original PubMed record.

Quote a phrase for an exact phrase match. Source license links do not imply unrestricted reuse.

At least 379 records · Page 21Linked to original sources
PubMed2005

Issues in human embryonic stem cell biology.

Human embryonic stem cells (hESCs) derived from frozen unused blastocytes from in vitro fertilization clinics exhibit unlimited proliferative capacity, and are pluripotent. The ability to maintain hESCs cultures in an undifferentiated state in vitro and differentiate them along a given lineage in a controlled manner make these cells potentially invaluable in regenerative medicine. Recent developments in the generation of patient-specific hESCs as well as animal product-free culture systems are some of the latest developments in the field; however great challenges lie ahead before the therapeutic application of hESCs becomes a reality. This article addresses some of the successes and roadblocks concerning the hESCs field; including various political, ethical and scientific obstacles.

Biology↗
PubMed2002

Signalling, cell cycle and pluripotency in embryonic stem cells.

Pluripotent mouse embryonic stem (ES) cells can be expanded in large numbers in vitro owing to a process of symmetrical self-renewal. Self-renewal entails proliferation with a concomitant suppression of differentiation. Here we describe how the cytokine leukaemia inhibitory factor (LIF) sustains self-renewal through activation of the transcription factor STAT3, and how two other signals - extracellular-signal-related kinase (ERK) and phosphatidylinositol-3-OH kinase (PI3K) - can influence differentiation and propagation, respectively. We relate these observations to the unusual cell-cycle properties of ES cells and speculate on the role of the cell cycle in maintaining pluripotency.

Animals↗
PubMed1996

Comparison of aggregation and injection techniques in producing chimeras with embryonic stem cells in mice.

We analyzed embryonic stem cell lines for their capacity to produce aggregation chimeras with diploid or developmentally compromised tetraploid embryos. Descendants of embryonic stem cells which contributed to midgestation fetuses at high levels were capable of supporting fetal development also with tetraploid partners. Different numbers of embryonic stem cells were introduced into diploid and tetraploid morulae as well as into blastocysts by microinjection. There were no differences in the frequency of embryonic stem cell-containing fetuses when comparing aggregation or injection into morulae versus blastocysts. However, the distribution pattern of embryonic stem cell derivatives in chimeric fetuses suggested that pre-compaction embryos are more suitable for generating fetuses with high embryonic stem cell contribution. Injection of embryonic stem cells into tetraploid embryos showed that completely embryonic stem cell-derived fetuses can also be produced by this technique. Totally embryonic stem cell derived fetuses were observed in each group, when embryonic stem cells were injected into diploid embryos. However, the rate of chimeras and chimerism was lower when 1 or 3 embryonic stem cells were used versus 8 or 15 cells. This suggests that the number of embryonic stem cells introduced might play a role in the colonization ability.

Journal Article↗
PubMed1987

Buffalo rat liver cells produce a diffusible activity which inhibits the differentiation of murine embryonal carcinoma and embryonic stem cells.

Many pluripotent embryonal carcinoma (EC) cell lines and all embryonic stem (ES) cell lines have hitherto been maintained in the undifferentiated state only by culture on feeder layers of mitomycin C-treated embryonic fibroblasts. We now demonstrate that medium conditioned by incubation with Buffalo rat liver (BRL) cells prevents the spontaneous differentiation of such cells which occurs when they are plated in the absence of feeders. This effect is not mediated via cell selection but represents a fully reversible inhibitory action ascribed to a differentiation-inhibiting activity (DIA). BRL-conditioned medium can therefore replace feeders in the propagation of homogeneous stem cell populations. Such medium also restricts differentiation in embryoid bodies formed via aggregation of EC cells and partially inhibits retinoic acid-induced differentiation. The PSA4 EC line gives rise only to extraembryonic endoderm-like cells when aggregated or exposed to retinoic acid in BRL-conditioned medium. This suggests that DIA may be lineage-specific. DIA is a dialysable, acid-stable entity of apparent molecular weight 20,000-35,000. Its actions are reproduced neither by insulin-like growth factor-II nor by transforming growth factor-beta. DIA thus appears to be a novel factor exerting a negative control over embryonic stem cell differentiation.

Animals↗
PubMed2002

Hematopoietic progenitor cells derived from embryonic stem cells: analysis of gene expression.

Rhesus monkey embryonic stem (ES) cells undergo differentiation in vitro to generate hematopoietic progenitor cells. Our previous studies demonstrated a high degree of similarity in the expression of genes associated with hematopoietic differentiation, homing, and engraftment in CD34(+) and CD34(+)CD38(-) cells from rhesus monkey ES cells and from fresh or cultured bone marrow (BM). In the present study, we compared the expression patterns of cyclins, cyclin-dependent kinases (CDKs) and CDK inhibitors (CDIs) in these cells. The expression of genes for cyclins, CDKs, and CDIs was similar among the hematopoietic progenitor cells of different origins, with only minor differences. Differentially expressed genes were also analyzed in CD34(+) lineage-negative cells derived from mouse ES cells and from BM. No difference or totally divergent results were obtained with the latter system, suggesting that this variation may be species specific. We observed, however, that CD34(+) and CD34(+)CD38(-) cells derived from ES cells expressed embryonic epsilon and zeta as well as alpha, beta, and gamma globin genes, whereas no expression of embryonic globins could be detected in the cell preparations from BM. Moreover, erythroblast-enriched CD34(-) cells derived from 4- or 5-week ES cell differentiation cultures also expressed embryonic, fetal, and adult globin genes, with greater beta gene expression, but otherwise were identical to those of the more primitive CD34(+) cells derived from 2-week ES cultures. These latter observations may reflect the presence of heterogeneous cell populations within the cell fractions that were compared, or they may represent variability among ES-cell-derived hematopoietic stem cells.

ATP Binding Cassette Transporter, Subfamily G, Mem↗
PubMed1992

Targeted disruption of the tissue inhibitor of metalloproteinases gene increases the invasive behavior of primitive mesenchymal cells derived from embryonic stem cells in vitro.

The metalloproteinase family of proteolytic enzymes can degrade extracellular matrix and facilitate invasive migration. This class of enzymes is specifically inhibited by the tissue inhibitor of metalloproteinases (TIMP-1). Using homologous recombination, we have disrupted the gene encoding TIMP-1 in pluripotent embryonic stem cells. Because the TIMP-1 gene is X linked and is hemizygous in embryonic stem cells, we have been able to study the effect of this mutation in culture. Using a basement membrane invasion assay, we found that the mutant cells, differentiated in low concentrations of serum with retinoic acid, were more invasive than their normal cell counterparts, and that this was specifically reversed by adding exogenous TIMP-1 protein. The invasive cell population had characteristics of an early population of primitive mesenchymal cells, including expression of vimentin and a transient period of invasiveness from 4-8 d after initiation of differentiation. Therefore, metalloproteinase activity can be rate limiting for cell invasion.

Base Sequence↗
PubMedDate not supplied

Hematopoietic differentiation of rhesus monkey embryonic stem cells.

Several lines of embryonic stem cells (ESC) have been established from rhesus monkey blastocysts. We have examined two of these cell lines for their potential for generating hematopoietic progenitors in cell culture, and we identified culture conditions, including supplementation with bone morphogenetic proteins (BMP), that result in hematopoietic differentiation of rhesus ESC with high efficiency. We have also characterized the resulting hematopoietic progenitor cells for their patterns of gene expression, as compared to those of hematopoietic progenitor cells harvested from rhesus monkey bone marrow. Of more than 60 genes examined in this manner, CD34+/CD38- cells derived from embryonic stem cells and those obtained from bone marrow demonstrated very similar patterns of gene expression. However, with integrin alphaL, IL-6 receptor, and flt-3 gene expression was greatly diminished or absent in CD34+/CD38- cells derived from the ESC, whereas the bone marrow-derived progenitors showed substantial expression of all of these genes. When the same type of comparison was done with mouse (D3 and CCE) as well as human (H1) embryonic stem cells, in each case comparing ESC-derived hematopoietic progenitors with those harvested from bone marrow, the only consistent deficiency of gene expression was that of flt-3. In hematopoietic precursors derived from mouse ESC, globin-gene expression has previously been shown to be a useful index of the embryological maturity of the cells, and we also examined globin-gene expression in rhesus monkey ESC-derived hematopoietic precursor cells, using a semiquantitative technique. CD34+/CD38- cells demonstrated expression of the epsilon- and gamma-globin genes, but negligible levels of beta globin, suggesting that these cells were at the developmental stage in which the yolk sac and fetal liver are the primary sites of hematopoiesis.

Animals↗
PubMed1998

Enrichment of blood from embryonic stem cells in vitro.

Murine embryonic stem (ES) cells are pluripotent. When injected into blastocysts they can give rise to every cell type of a derived chimeric mouse including germ cells. Embryonic stem cells also possess remarkable in vitro differentiation potential. When removed from stromal support and leukaemia inhibitory factor (LIF), ES cells differentiate into structures known as embryoid bodies (EBs), in which all three germ layers develop and interact. As ES cells from humans become available there is increasing interest in the potential for EBs to provide an unlimited supply of stem cells for somatic transplantation therapies. Realisation of this potential will require greater understanding of the molecular determinants of cell fate within EBs. Also, culture techniques for selective expansion of cell lineages of interest will reduce the risks associated with transplantation of EB-derived cells. In this paper the kinetics of expression of mRNA and protein for early mesoderm markers within EBs is reported. In addition, a three-step culture system incorporating co-cultivation on the bone marrow derived stromal cell line, MC3T3-G2/PA6 (PA6), is explored as a way to select for haematopoietic progenitor cells (HPCs) and against undifferentiated ES cells. A system like this could enhance purification of haematopoietic stem cells (HSCs) from ES cells for bone marrow transplantation.

Animals↗
PubMed2006

Nuclear reprogramming of somatic nucleus hybridized with embryonic stem cells by electrofusion.

Cell fusion is a powerful tool for understanding the molecular mechanisms of epigenetic reprogramming. In hybrid cells of somatic cells and pluripotential stem cells, including embryonic stem (ES) and embryonic germ cells, somatic nuclei acquire pluripotential competence. ES and embryonic germ cells retain intrinsic trans activity to induce epigenetic reprogramming. For generating hybrid cells, we have used the technique of electrofusion. Electrofusion is a highly effective, reproducible, and biomedically safe in vitro system. For successful cell fusion, two sequential steps of electric pulse stimulation are required for the alignment (pearl chain formation) of two different types of cells between electrodes in response to alternating current stimulation and for the fusion of cytoplasmic membranes by direct current stimulation. Optimal conditions for electrofusion with a pulse generator are introduced for ES and somatic cell fusion. Topics in the field of stem cell research include the successful production of cloned animals via the epigenetic reprogramming of somatic cells and contribution of spontaneous cell fusion to generating intrinsic plasticity of tissue stem cells. Cell fusion technology may make important contributions to the fields of epigenetic reprogramming and regenerative medicine.

Animals↗
PubMed2000

Apoptosis of mouse embryonic stem cells induced by single cell suspension.

Embryonic stem cells (ES cells) are pluripotential, and are therefore used to construct gene knock-out mice. We found that the apoptosis of mouse ES cells was induced when the cells were dispersed as single cells, whereas this process was suppressed when they proliferated in aggregates. The apoptosis of ES cells was repressed when the cells were cultured on feeders prepared from STO cells, a cell line established from embryonic fibroblasts. Culture supernatants from STO cells did not block the apoptosis of ES cells, which suggests that a direct interaction between ES cells and STO cells is required for the suppression of apoptosis. The viability of ES cells examined by the trypan blue exclusion test or by the MTT ((3-4,5-dimethyithiazol-2-yl)-2,5-diphenyltetrazolium bromide) reduction assay decreased dramatically when the cells were dispersed in phosphate-buffered saline PBS. Cellular activity was restored by the addition of culture medium for ES cells. Glucose in the medium was found to be a major factor responsible for the restoration. Amino acids also restored the decrease in reduction of MTT. Suspension of the ES cells in PBS(-) caused leakage of the nucleosome into cytoplasm. Results indicate that the single cell suspension of ES cells leads to leakage of substrates for oxidative phosphorylation from the mitochondria, and that these cells finally become committed to apoptosis.

Amino Acids↗
PubMed2004

Establishment and in vitro differentiation of a new embryonic stem cell line from human blastocyst.

Embryonic stem cells have the ability to remain undifferentiated and proliferate indefinitely in vitro while maintaining the potential to differentiate into derivatives of all three embryonic germ layers. These cells have, therefore, potential for in vitro differentiation studies, gene function, and so on. The aim of this study was to produce a human embryonic stem cell line. An inner cell mass of a human blastocyst was separated and cultured on mouse embryonic fibroblasts in embryonic stem cell medium with related additives. The established line was evaluated by morphology; passaging; freezing and thawing; alkaline phosphatase; Oct-4 expression; anti-surface markers including Tra-1-60 and Tra-1-81; and karyotype and spontaneous differentiation. Differentiated cardiomyocytes and neurons were evaluated by transmission electron microscopy and immunocytochemistry. Here, we report the derivation of a new embryonic stem cell line (Royan H1) from a human blastocyst that remains undifferentiated in morphology during continuous passaging for more than 30 passages, maintains a normal XX karyotype, is viable after freezing and thawing, and expresses alkaline phosphatase, Oct-4, Tra-1-60, and Tra-1-81. These cells remain undifferentiated when grown on mouse embryonic fibroblast feeder layers in the presence or absence of recombinant human leukemia inhibitory factor. Royan H1 cells can differentiate in vitro in the absence of feeder cells and can produce embryoid bodies that can further differentiate into beating cardiomyocytes as well as neurons. These results define Royan H1 cells as a new human embryonic stem cell line.

Alkaline Phosphatase↗
PubMed2002

Mast cells derived from embryonic stem cells: a model system for studying the effects of genetic manipulations on mast cell development, phenotype, and function in vitro and in vivo.

Large quantities of highly enriched populations of mast cells can be generated from mouse embryonic stem (ES) cells using an in vitro differentiation system. These embryonic stem cell-derived mast cells (ESMCs) exhibit many similarities to mouse bone marrow-derived cultured mast cells (BMCMCs), including the abilities to survive and to orchestrate immunologically specific immunoglobulin E (IgE)-dependent reactions in vivo after transplantation into genetically mast cell-deficient KitW/KitW-v mice. Coupled with the current spectrum of techniques for genetically manipulating ES cells, ESMCs represent a unique model system to analyze the effects of specific alterations in gene structure, expression, or function, including embryonic lethal mutations, on mast cell development, phenotype, and function in vitro and in vivo.

Animals↗
PubMed2003

Stable lines of genetically modified dendritic cells from mouse embryonic stem cells.

BACKGROUND: The capacity to activate naïve T cells sets dendritic cells (DCs) apart from other antigen-presenting cells, making them attractive targets for immune intervention during deleterious immune responses. The inherent resistance of terminally differentiated DCs to conventional strategies for genetic modification has, however, greatly limited our understanding of the molecular mechanisms underlying their function. METHODS AND RESULTS: We report the derivation of long-term cultures of untransformed DCs, uniformly expressing a defined mutant phenotype by the directed differentiation of cloned embryonic stem cells, stably transfected with a reporter gene. Introduction of the gene encoding enhanced green fluorescent protein into pluripotent stem cells demonstrated no observable impact on the phenotype, immunogenicity, or capacity for maturation of DCs differentiated from them. CONCLUSIONS: The production of unlimited numbers of mutant DCs from genetically modified embryonic stem cells paves the way for the systematic elucidation of gene function in this cell type and the rational design of DCs for use in immunotherapy.

Animals↗
PubMed2006

Generation of insulin-secreting cells from human embryonic stem cells.

A growth factor-mediated selection method was used to obtained insulin-secreting cells from human embryonic stem cells (hESC; Royan H1). Our resultant cells were positive for dithizone, a zinc-chelating agent known to selectively stain pancreatic beta cells and immunoreactive for antibodies against insulin, glucagon, and C-peptide. Semi-quantitative reverse transcription-polymerase chain reaction detected expression of proinsulin, insulin and other pancreatic beta-cell-related genes, such as Nkx6.1, Is11, Glut2, Pax4, and prohormone convertase2 (PC2). Moreover, glucagon, somatostatin, K(ATP)-channel genes KIR6.2 and SUR1, islet amyloid polypeptide (IAPP), PC1/3, and glucokinase (GCK) were expressed in the differentiating hESC in a developmental stage-dependent manner. Also, the addition of glucose to the culture medium triggered insulin release from differentiated cells, but transmission electron microscopy of the differentiated cells did not show typical beta-cell granules, even though secretary granules were detected. The results showed that hESC have the ability to transcribe and process insulin, but further improvements of the current method are required to generate a sufficient source of true beta cells for the treatment of diabetes mellitus.

Cell Culture Techniques↗
PubMed2004

Temporal expression changes during differentiation of neural stem cells derived from mouse embryonic stem cell.

Temporal analysis in gene expression during differentiation of neural stem cells (NSCs) was performed by using in-house microarrays composed of 10,368 genes. The changes in mRNA level were measured during differentiation day 1, 2, 3, 6, 12, and 15. Out of 10,368 genes analyzed, 259 genes were up-regulated or down-regulated by 2-fold or more at least at one time-point during differentiation, and were classified into six clusters based on their expression patterns by K-means clustering. Clusters characterized by gradual increase have large numbers of genes involved in transport and cell adhesion; those which showed gradual decrease have much of genes in nucleic acid metabolism, cell cycle, transcription factor, and RNA processing. In situ hybridization (ISH) validated microarray data and it also showed that Fox M1, cyclin D2, and CDK4 were highly expressed in CNS germinal zones and ectonucleotide pyrophosphatase/phosphodiesterase 2 (Enpp2) was highly expressed in choroid plexus where stem/progenitor cells are possibly located. Together, this clustering analysis of expression patterns of functionally classified genes may give insight into understanding of CNS development and mechanisms of NSCs proliferation and differentiation.

Animals↗