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Results for “Embryonic stem cells”

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PubMed1998

p53-independent DNA repair and cell cycle arrest in embryonic stem cells.

The role of p53 in DNA repair and cell cycle checkpoint after ultraviolet irradiation was investigated in an embryonic stem cell line homozygous for a targeted deletion of p53. Results indicate that loss of p53 does not alter the capacity of ES cells to respond to DNA damage. Wild-type and p53-deficient cells showed similar cessation of DNA synthesis after UV damage and similar ultimate capacity to repair a transiently transfected reporter plasmid. Interestingly, in the absence of DNA damaging treatment, the transit of p53-deficient cells through S phase was slower than wild-type cells. We suggest that this may result from the absence of a p53-dependent response to endogenous DNA damage: without p53 sensing endogenous damage leading to immediate repair, such damage may persist and thus delay DNA synthesis.

Animals↗

PubMed1996

Blood island formation in attached cultures of murine embryonic stem cells.

Differentiation of murine embryonic stem cells in suspension culture results in the formation of cystic embryoid bodies that develop blood islands. In this study pre-cystic embryoid bodies were attached to a substratum, and the program of differentiation was monitored. The attached ES cell cultures formed blood islands on a cell layer that migrated out from the center of attachment and beneath a mesothelial-like cell layer. Morphological and in situ marker analysis showed benzidine-positive hematopoietic cells surrounded by vascular endothelial cells that expressed PECAM and took up DiI-Ac-LDL. Waves of morphological differentiation were evident, suggesting a graded response to differentiation signals. Electron microscopy of the blood islands showed that they were similar to blood islands of cystic embryoid bodies and mouse yolk sacs, and cell-cell junctions were evident among the blood island cells. RNA expression analysis was consistent with the presence of hematopoietic precursor cells of several lineages and a primitive vascular endothelium in the cultures. Thus a program of vascular and hematopoietic development can be elaborated in attached ES cell cultures, and these blood islands are accessible to experimental manipulation.

Animals↗

PubMed2002

Embryonic stem cells.

The capacity of embryonic stem cells for virtually unlimited self-renewal and differentiation capacity has opened up the prospect of widespread applications in biomedical research and regenerative medicine. For the latter, the cells provide hope that it will be possible to overcome the problems of donor tissue shortage and also, by making the cells immunocompatible with the recipient, implant rejection. Four years after the first derivation of human pluripotent cell lines from pre-implantation embryos, a great deal has been learnt about their biology and how differentiation can be encouraged towards particular cell lineages. However, considerable research is needed, not least into means to enrich and purify derivative cell lineages, before clinical trials can be considered.

Cell Differentiation↗

PubMed2004

Human blastocysts for the development of embryonic stem cells.

Establishment of human embryonic stem cells (hES) from surplus human IVF embryos has been successful when both fresh and frozen-thawed cleavage stage embryos have been cultured to the blastocyst stage. This study reports the characteristics of the starting material, the blastocysts, for hES cell lines that were first derived at the University of Gothenburg, Sahlgrenska University Hospital in 1999. Twenty-two hES cell lines were derived by Cellartis AB from 114 blastocysts, giving an overall success rate of 19.3%. The blastocysts from which the hES cell lines were established were of varying morphological quality, both fresh and frozen-thawed. Two techniques of hES establishment were applied, i.e. direct application of the blastocysts on feeder cells or the standard immunosurgery method. It was further found that the efficiency by which frozen-thawed embryos gave rise to new hES cell lines was 3.7 times better than with fresh surplus embryos. These findings suggest that frozen-thawed embryos are superior to fresh surplus human embryos in hES cell establishment, which also avoids specific ethical problems associated with embryo donation in a fresh IVF cycle.

Blastocyst↗

PubMed2002

[Ethical aspects of embryonic stem cell research].

Research using embryonic stem cells raises a variety of ethical questions, which will be explored in this article. At the core of the ethical controversy is the question of the status of the embryo and its availability for research. A range of countries have approved the use of "supernumerous" embryos from in-vitro fertilization. But ethical problems also arise in reproduction medicine, the informed consent of affected couples, and the targeted production of embryos and egg cell donation for research. The author discuss some of these neglected issues and develops suggestions for comprehensive ethical reflection.

Adult↗

PubMed2006

Derivation of distal airway epithelium from human embryonic stem cells.

The pluripotency of embryonic stem cells (ESC) is offering new opportunities in tissue engineering and cell therapy. We have shown previously that alveolar epithelial cells, specifically type II pneumocytes, can be derived from murine ESC and hypothesized that a similar protocol could be used successfully on human ESC. Undifferentiated human ESC were induced to form embryoid bodies that were transferred into adherent culture conditions and grown in a medium designed for the maintenance of mature small airway epithelium. On inverted microscopy, the generated cells showed the cobblestone-like morphology of epithelium. The presence of surfactant protein C, a specific marker of type II pneumocytes, and its corresponding RNA were demonstrated by immunostaining and reverse transcription polymerase chain reaction, respectively. Electron microscopy revealed frequent cells with the typical ultrastructure of type II pneumocytes. This study provides evidence for in vitro induction of the differentiation from human ESC of alveolar type II cells, which have the potential for therapeutic use or construction of an in vitro model of human lung.

Animals↗

PubMed2004

VIP and PACAP induce selective neuronal differentiation of mouse embryonic stem cells.

The capacity of embryonic stem cells (ES cells) to differentiate into neuronal cells represents a potential source for neuronal replacement and a model for studying factors controlling early stages of neuronal differentiation. Various molecules have been used to induce such differentiation but so far neuropeptides acting via functional G-protein-coupled receptors (GPCRs) have not been investigated. Vasoactive intestinal polypeptide (VIP) and pituitary adenylate cyclase-activating polypeptide (PACAP) are neuropeptides expressed in early development which affect neuronal precursor proliferation and neuronal differentiation. VIP and PACAP share two common receptors (VPAC1 and VPAC2 receptors) while only PACAP binds with high affinity to PAC1 receptors. The aim of the study was to determine whether VIP and PACAP could produce functional neuronal differentiation of ES cells. Mouse ES cells were allowed to aggregate in embryoid bodies (EBs) in the presence or not of VIP and PACAP for 1 week. VIP and PACAP potently increased the proportion of EB-derived cells expressing specifically a neuronal phenotype shown by immunocytochemistry and neurite outgrowth without altering glial cell number. Binding and RT-PCR analyses demonstrated the presence of VPAC2 and PAC1 receptors on ES cells. Accordingly, both peptides increased cyclic AMP and intracellular calcium. In contrast, EB-derived cells only expressed a functional PAC1 receptor, suggesting a switch in GPCR phenotype during ES cell differentiation. These original data demonstrate that functional GPCRs for VIP and PACAP are present on ES cells and that these neuropeptides may induce their differentiation into a neuronal phenotype. It opens an exciting new field for neuropeptide regulation of tissue ontogenesis.

Animals↗

PubMed1988

Vasculogenesis and angiogenesis in embryonic-stem-cell-derived embryoid bodies.

Embryonic stem cells (ESC) have been established previously from the inner cell mass cells of mouse blastocysts. In suspension culture, they spontaneously differentiate to blood-island-containing cystic embryoid bodies (CEB). The development of blood vessels from in situ differentiating endothelial cells of blood islands, a process which we call vasculogenesis, was induced by injecting ESC into the peritoneal cavity of syngeneic mice. In the peritoneum, fusion of blood islands and formation of an in vivo-like primary capillary plexus occurred. Transplantation of ESC and ESC-derived complex and cystic embryoid bodies (ESC-CEB) onto the quail chorioallantoic membrane (CAM) induced an angiogenic response, which was directed by nonyolk sac endoderm structures. Neither yolk sac endoderm from ESC-CEB nor normal mouse yolk sac tissue induced angiogenesis on the quail CAM. Extracts from ESC-CEB stimulated the proliferation of capillary endothelial cells in vitro. Mitogenic activity increase during in vitro culture and differentiation of ESC. Almost all growth factor activity was associated with the cells. The ESC-CEB derived endothelial cell growth factor bound to heparin-sepharose. The identification of acidic fibroblast growth factor (FGF)in heparin-sepharose-purified material was accomplished by immunoblot experiments involving antibodies against acidic and basic FGF. We conclude that vasculogenesis, the development of blood vessels from in situ differentiating endothelial cells, and angiogenesis, the sprouting of capillaries from preexisting vessels are very early events during embryogenesis which can be studied using ESC differentiating in vitro. Our results suggest that vasculogenesis and angiogenesis are differently regulated.

Animals↗

PubMed2001

The preliminary experimental study of induced differentiation of embryonic stem cells into corneal epithelial cells.

PURPOSE: To study preliminarily induced differentiation of embryonic stem cells into corneal epithelial cells in vitro. METHODS: Murine embryonic stem cells were co-cultured with Rabbit limbal corneal epithelial cells in Transwell system to induce differentiation. Mophological and immunohistochemical examination were implemented. RESULTS: The induced cells from embryonic stem cells have an epithelial appearance. The cells formed a network and were confluent into film gradually after being co-cultured with rabbit limbal corneal epithelial cells for 24-96 hours. The cells ranged mosaic structure and localized together with clear rim. Most of the cells showed polygonal appearance. Transmission electron microscope showed lots of microvilli on the surface of induced cells and tight junctions between them. These epithelial-like cells expressed the corneal epithelial cell specific marker cytokeratin3/cytokeratin12. CONCLUSION: The potential mechanism of the differentiation of murine embryonic stem cells into corneal epithelial cells induced by limbal corneal epithelial cell-derived inducing activity is to be further verified.

Animals↗

PubMedDate not supplied

[The interaction of homotypic and heterotypic embryonic stem cells with developing embryos].

It has been demonstrated that embryonic stem cells form adhesive contacts with external blastomeres of mouse morula, while there is no such contact with blastocysts. The development of morula in the blastocysts is delayed inside a dense layer of such cells; however, in some cases, external blastomeres of the morula begin to differentiate into trophoblastic cells. The introduction of an excessive number of embryonic stem cells (15-20) into a 4-8-cell embryo results in abnormal development. When heterotypic embryonic mink stem cells are co-cultivated, they show only very weak adhesion with mouse blastomeres and are displaced as a result of compactization. When blastocysts are formed after the injection of heterotypic embryonic stem cells, such cells remain in the perivitelline space. In some cases, heterotypic embryonic stem cells continue to be determined in the trophoblastic direction and produce trophoblastic vesicles autonomously. The role of cell interaction in the determination of cells during early mammalian development is discussed.

Animals↗

PubMed2000

Directed differentiation of dendritic cells from mouse embryonic stem cells.

Dendritic cells (DCs) are uniquely capable of presenting antigen to naive T cells, either eliciting immunity [1] or ensuring self-tolerance [2]. This property identifies DCs as potential candidates for enhancing responses to foreign [3] and tumour antigens [4], and as targets for immune intervention in the treatment of autoimmunity and allograft rejection [1]. Realisation of their therapeutic potential would be greatly facilitated by a fuller understanding of the function of DC-specific genes, a goal that has frequently proven elusive because of the paucity of stable lines of DCs that retain their unique properties, and the inherent resistance of primary DCs to genetic modification. Protocols for the genetic manipulation of embryonic stem (ES) cells are, by contrast, well established [5], as is their capacity to differentiate into a wide variety of cell types in vitro, including many of hematopoietic origin [6]. Here, we report the establishment, from mouse ES cells, of long-term cultures of immature DCs that share many characteristics with macrophages, but acquire, upon maturation, the allostimulatory capacity and surface phenotype of classical DCs, including expression of CD11c, major histocompatibility complex (MHC) class II and co-stimulatory molecules. This novel source should prove valuable for the generation of primary, untransformed DCs in which candidate genes have been overexpressed or functionally ablated, while providing insights into the earliest stages of DC ontogeny.

Animals↗

PubMed2006

Radiation-induced response of micro RNA expression in murine embryonic stem cells.

Despite the importance of embryonic stem cells in embryology and regenerative medicine, their response to DNA damage is not fully understood. Here we studied the expression profiles of small RNAs approximately 22 nucleotides long called micro RNAs, which play an important role in developmental regulation in plants and animals. We identified a group of micro RNAs with increased expression after exposure to radiation (compared with murine fibroblasts) and characterized putative target genes. These micro RNA sequences are conserved in mice, chickens and humans with similar genomic organizations, suggesting that a common regulatory network is involved in stem cell regulation in response to DNA damage. Micro RNAs might be useful as therapeutic tools to control DNA damage response in pluripotent stem cells.

Animals↗

PubMed2002

Flk1+ cells derived from mouse embryonic stem cells reconstitute hematopoiesis in vivo in SCID mice.

OBJECTIVE: Embryonic stem (ES) cells are pluripotent and can differentiate into any cell type, including the hematopoietic lineage. We examined whether hematopoietic progenitor cells derived from ES cells reconstitute hematopoiesis in irradiated SCID mice. MATERIALS AND METHODS: ES cells (E14.1, H2K(b)) were cultured for 4 days in semisolid medium containing methylcellulose. Irradiated SCID mice were used as recipients of hematopoietic progenitor cells. Cell surface antigen expression was analyzed by flow cytometry. The spleens of the recipient mice were studied by hematoxylin and eosin staining and immunohistochemical staining. RESULTS: After cell culture of ES cells in methylcellulose for 4 days, the cells expressing Flk1 (VEGF receptor 2), a tentative marker of hemangioblasts, were increased, whereas cells expressing CD31 (PECAM-1) and E-cadherin (nonmesodermal adhesion molecule) were dramatically reduced. Flk1+ cells expressed c-kit predominantly. Circulating leukocytes and thrombocytes were increased in irradiated SCID (H2K(d)) mice transplanted with ES cell-derived Flk1+ cells compared with vehicle-injected control mice. H2K(b+) and VE-cadherin(+) vascular endothelial cells were prominent in spleens of the recipient mice. Flow cytometric analysis demonstrated that H2K(b+) cells were increased in the bone marrow of recipient mice. In addition, Flk1+ cells accompanying enhanced c-kit expression preferentially repopulated in the bone marrow, and leukopoiesis and thrombopoiesis of the recipient mice were evident. CONCLUSION: The Flk1+ hematopoietic cells derived from ES cells reconstitute hematopoiesis in vivo and may become an alternative donor source for bone marrow transplantation.

Animals↗

PubMed2006

Potentiality of embryonic stem cells: an ethical problem even with alternative stem cell sources.

The recent discussions about alternative sources of human embryonic stem cells (White Paper of the US President's Council on Bioethics, 2005), while stirring new interest in the developmental potential of the various abnormal embryos or constructs proposed as such sources, also raise questions about the potential of the derived embryonic stem cells. The data on the developmental potential of embryonic stem cells that seem relevant for ethical considerations and aspects of patentability are discussed. Particular attention is paid to the meaning of "totipotency, omnipotency and pluripotency" as illustrated by a comparison of the developmental potential of three-dimensional clusters of blastomeres (morula), embryonic stem cells, somatic or (adult) stem cells or other somatic (non-stem) cells. This paper focuses on embryoid bodies and on direct cloning by tetraploid complementation. Usage and patenting of these cells cannot be considered to be ethically sound as long as totipotency and tetraploid complementability of embryonic stem cells are not excluded for the specific cell line in question. Testing this poses an ethical problem in itself and needs to be discussed in the future.

Adult↗

PubMed2005

Identification of candidate regulators of embryonic stem cell differentiation by comparative phosphoprotein affinity profiling.

Embryonic stem cells are a unique cell population capable both of self-renewal and of differentiation into all tissues in the adult organism. Despite the central importance of these cells, little information is available regarding the intracellular signaling pathways that govern self-renewal or early steps in the differentiation program. Embryonic stem cell growth and differentiation correlates with kinase activities, but with the exception of the JAK/STAT3 pathway, the relevant substrates are unknown. To identify candidate phosphoproteins with potential relevance to embryonic stem cell differentiation, a systems biology approach was used. Proteins were purified using phosphoprotein affinity columns, then separated by two-dimensional gel electrophoresis, and detected by silver stain before being identified by tandem mass spectrometry. By comparing preparations from undifferentiated and differentiating mouse embryonic stem cells, a set of proteins was identified that exhibited altered post-translational modifications that correlated with differentiation state. Evidence for altered post-translational modification included altered gel mobility, altered recovery after affinity purification, and direct mass spectra evidence. Affymetrix microarray analysis indicated that gene expression levels of these same proteins had minimal variability over the same differentiation period. Bioinformatic annotations indicated that this set of proteins is enriched with chromatin remodeling, catabolic, and chaperone functions. This set of candidate phosphoprotein regulators of stem cell differentiation includes products of genes previously noted to be enriched in embryonic stem cells at the mRNA expression level as well as proteins not associated previously with stem cell differentiation status.

Animals↗

PubMed2004

In vivo fate-tracing studies using the Scl stem cell enhancer: embryonic hematopoietic stem cells significantly contribute to adult hematopoiesis.

Evidence for the lineage relationship between embryonic and adult hematopoietic stem cells (HSCs) in the mouse is primarily indirect. In order to study this relationship in a direct manner, we expressed the tamoxifen-inducible Cre-ER(T) recombinase under the control of the stem cell leukemia (Scl) stem-cell enhancer in transgenic mice (HSC-SCL-Cre-ER(T)). To determine functionality, HSC-SCL-Cre-ER(T) transgenics were bred with Cre reporter mice. Flow cytometric and transplantation studies revealed tamoxifen-dependent recombination occurring in more than 90% of adult long-term HSCs, whereas the targeted proportion within mature progenitor populations was significantly lower. Moreover, the transgene was able to irreversibly tag embryonic HSCs on days 10 and 11 of gestation. These cells contributed to bone marrow hematopoiesis 5 months later. In order to investigate whether the de novo HSC generation is completed during embryogenesis, HSC-SCL-Cre-ER(T)-marked fetal liver cells were transplanted into adult recipients. Strikingly, the proportion of marked cells within the transplanted and the in vivo-remaining HSC compartment was not different, implying that no further HSC generation occurred during late fetal and neonatal stages of development. These data demonstrate for the first time the direct lineage relationship between midgestation embryonic and adult HSCs in the mouse. Additionally, the HSC-SCL-Cre-ER(T) mice will provide a valuable tool to achieve temporally controlled genetic manipulation of HSCs.

Age Factors↗

PubMed2005

Human embryonic stem cells: possibilities for human cell transplantation.

Human embryonic stem (ES) cells serve as a potentially unlimited renewable source for cell transplantation targeted to treat several diseases. One advantage of embryonic stem (ES) cells over other stem cells under research is their apparently indefinite self-renewal capacity if cultured appropriately, and their ready differentiation into various cell phenotypes of all three germ layers. To date, a number of studies have reported the derivation of specific functional derivatives from human ES cells in vitro. While there have been clinical trials of human embryonal carcinoma (EC) cell-derived neurons in humans there has been no attempt as yet using human ES cell derivatives. However, the latter have been transplanted into recipient animals. In some cases ES-derived cells were shown to undergo further maturation, displayed integration with host tissue and even ameliorated the disease condition in the animal model. Recently, it has been reported that human ES cells can be genetically manipulated. Such procedures could be used to direct differentiation to a specific cell type or to reduce graft rejections by the modification of immune responses. This review highlights some of the recent advances in the field and the challenges that lie ahead before clinical trials using ES-derived cells can be contemplated.

Cell Culture Techniques↗

PubMed2003

Potential use of embryonic stem cells for the treatment of mouse parkinsonian models: improved behavior by transplantation of in vitro differentiated dopaminergic neurons from embryonic stem cells.

BACKGROUND: and Aims. The purpose of the present study was to examine the efficacy of transplantation of mouse embryonic-stem-(ES)-cell-derived tyrosine hydroxylase-positive (TH(+)) cells into Parkinsonian mice using behavioral tests and immunohistochemical evaluation. METHODS: Undifferentiated ES cells carrying the enhanced green fluorescent protein (EGFP) gene were differentiated into a cell population containing TH(+) neurons using a five-step in vitro differentiation method. These ES-cell-derived cells were used as allografts in Parkinsonian mice, made by administering injections of 6-hydroxydopamine (6-OHDA). Fifteen hemiparkinsonian mice were divided into three groups. Four weeks after 6-OHDA injection, mice in groups 1, 2, and 3 received phosphate-buffered saline, 1 x 10(4) graft cells, and 1 x 10(5) graft cells, respectively, into their dopamine-denervated striata. RESULTS: Improved rotational behavior was observed in the graft-transplanted groups (groups 2 and 3) 2 weeks after transplantation. Mice in group 2 displayed a continuous maintenance of reduced rotational behavior, while those in group 3 showed ipsilateral rotation toward the lesioned side at 4, 6, and 8 weeks after transplantation. Tumor formation was observed in one mouse in group 3. TH(+) cells were found at the grafted sites 8 weeks after transplantation in mice in groups 2 and 3, some of which were immunopositive to GFP, demonstrating the presence of dopaminergic neurons derived from the ES cells. CONCLUSION: Transplantation of in vitro differentiated ES cells changed rotational behavior in Parkinsonian mice. Our results suggest the potential availability of ES cells for Parkinson's disease.

Animals↗