Biomedical subjects

Edward W Scott

Publications and source records attributed to Edward W Scott.

25 records · Page 2Linked to original sources

PubMed2003

Mouse A6-positive hepatic oval cells also express several hematopoietic stem cell markers.

Hepatic oval cells (HOC) are thought to be a type of facultative stem cell that arises as a result of certain forms of hepatic injury. A new and more efficient model has been established to activate the oval cell compartment in mice by incorporating 3,5-diethoxycarbonyl-1,4-dihydro-collidine (DDC) in a standard chow at a concentration of 0.1%. At the present time, very few markers exist for the mouse oval cells. One accepted marker is A6, an uncharacterized epitope recognized by mouse hepatic oval cells and it is accepted to be an oval cell marker. Sca-1 is a cell surface marker used to identify hematopoietic stem cells in conjunction with Thy-1+, CD34+, and lineage-specific markers. Both the CD34 and Sca-1 antigens are not normally expressed in adult liver, but are expressed in fetal liver, presumably on the hematopoietic cells. We report herein that mouse oval cells express high levels of Sca-1 and CD34, as well as CD45 surface proteins. Immunohistochemistry revealed that the cells expressing Sca-1/CD34/CD45 were indeed oval cells because they co-expressed the oval cell-specific marker A6 (94.57% +/- 0.033%), as well as alpha-fetoprotein (AFP) (75.92% +/- 0.071%). By using Sca-1 antibody in conjunction with magnetic activated cell sorting (MACS), followed with a flow cytometric cell sorting (FACS) method for CD34 and CD45, we have developed a rapid oval cell isolation protocol with high yields of greater than 90%. In conclusion, we have an efficient murine model for the production and isolation of large numbers of highly purified oval cells. Our system works with most strains of mouse, which will facilitate both in vivo and in vitro studies of mouse hepatic oval cells.

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PubMed2003

The role of adult bone marrow-derived stem cells in choroidal neovascularization.

PURPOSE: Age-related macular degeneration (ARMD) is the primary cause of blindness in people aged of 50 years or more. The wet form leads to severe loss of central vision. Recent evidence supports that adult hematopoietic stem cells (HSCs) contribute to preretinal neovascularization. In the current study, it was determined whether HSCs, by producing both blood and blood vessels, provide functional hemangioblast activity during choroidal neovascularization (CNV) in mice. METHODS: Gfp chimeric mice were developed by bone marrow ablation of C57BL/6J mice and reconstitution with donor tissue from gfp(+/+) transgenic mice. Gfp chimeric mice underwent laser rupture of Bruch's membrane and were killed and eyes enucleated at 1, 2, 3, and 4 weeks after laser injury. CNV was examined by confocal microscopy of retinal flatmounts. Because endothelial progenitor cells (EPCs) derive from HSCs, immunocytochemistry was used to quantify relative the EPC contribution to CNV. RESULTS: Laser injury alone was sufficient to induce stem cell recruitment and subsequent CNV. Gfp+ cells formed part of the functional vasculature in the choroid as early as 1 week after injury and were present for the duration of the study. The relative EPC contribution to CNV remained fairly constant throughout the study and constituted almost 50% of the total vasculature. CONCLUSIONS: Adult stem cells are recruited to the choroid in a model of CNV, where they contribute to forming aberrant new vessels. This observation suggests that targeting stem cell recruitment to the eye may offer a novel therapeutic strategy for ARMD.

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PubMed2003

An overview of stem cell research and regulatory issues.

Stem cells are noted for their ability to self-renew and differentiate into a variety of cell types. Some stem cells, described as totipotent cells, have tremendous capacity to self-renew and differentiate. Embryonic stem cells have pluripotent capacity, able to form tissues of all 3 germ layers but unable to form an entire live being. Research with embryonic stem cells has enabled investigators to make substantial gains in developmental biology, therapeutic tissue engineering, and reproductive cloning. However, with these remarkable opportunities many ethical challenges arise, which are largely based on concerns for safety, efficacy, resource allocation, and methods of harvesting stem cells. Discussing the moral and legal status of the human embryo is critical to the debate on stem cell ethics. Religious perspectives and political events leading to regulation of stem cell research are presented and discussed, with special attention directed toward the use of embryonic stem cells for therapeutic and reproductive cloning. Adult stem cells were previously thought to have a restricted capacity to differentiate; however, several reports have described their plasticity potential. Furthermore, there have been close ties between the behavior of stem cells and cancer cells. True eradication of cancer will require a deeper understanding of stem cell biology. This article was written to inform medical scientists and practicing clinicians across the spectrum of medical education about the research and regulatory issues affecting the future of stem cell therapy.

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PubMed2002

Distinct functions for signal transducer and activator of transcription 1 and PU.1 in transcriptional activation of Fc gamma receptor I promoter.

The myeloid cell-specific expression and interferon-gamma (IFN-gamma) induction of Fc gamma receptor I (FcgammaRI) requires cooperation between PU.1 and signal transducer and activator of transcription 1 (Stat1) by means of mechanisms that are unknown. We found that PU.1 and Stat1 mediated distinct functions in the activation of FcgammaRI promoter. The basal activity of the natural FcgammaRI promoter was strictly dependent on PU.1, and IFN-gamma induction required both PU.1 and Stat1. Recruitment of TATA-binding protein (TBP) to the FcgammaRI promoter did not replace PU.1 in promoter activation, suggesting that TBP is not sufficient for FcgammaRI activation and that PU.1 mediates additional contacts with basal transcription machinery. In contrast, Stat1 did not interact with basal transcription machinery, but the Stat1-mediated activation of FcgammaRI promoter critically required CREB-binding protein (CBP)/p300. These results define functional cooperativity between PU.1 and Stat1 in FcgammaRI promoter activation, in which PU.1 appears to serve as a bridging factor with the basal transcription machinery and IFN-gamma-mediated induction of transcription occurs through recruitment of CBP/p300 by Stat1.

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PubMed2002

Bone marrow cells adopt the phenotype of other cells by spontaneous cell fusion.

Recent studies have demonstrated that transplanted bone marrow cells can turn into unexpected lineages including myocytes, hepatocytes, neurons and many others. A potential problem, however, is that reports discussing such 'transdifferentiation' in vivo tend to conclude donor origin of transdifferentiated cells on the basis of the existence of donor-specific genes such as Y-chromosome markers. Here we demonstrate that mouse bone marrow cells can fuse spontaneously with embryonic stem cells in culture in vitro that contains interleukin-3. Moreover, spontaneously fused bone marrow cells can subsequently adopt the phenotype of the recipient cells, which, without detailed genetic analysis, might be interpreted as 'dedifferentiation' or transdifferentiation.

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PubMed2002

Adult hematopoietic stem cells provide functional hemangioblast activity during retinal neovascularization.

Adults maintain a reservoir of hematopoietic stem cells that can enter the circulation to reach organs in need of regeneration. We developed a novel model of retinal neovascularization in adult mice to examine the role of hematopoietic stem cells in revascularizing ischemic retinas. Adult mice were durably engrafted with hematopoietic stem cells isolated from transgenic mice expressing green fluorescent protein. We performed serial long-term transplants, to ensure activity arose from self-renewing stem cells, and single hematopoietic stem-cell transplants to show clonality. After durable hematopoietic engraftment was established, retinal ischemia was induced to promote neovascularization. Our results indicate that self-renewing adult hematopoietic stem cells have functional hemangioblast activity, that is, they can clonally differentiate into all hematopoietic cell lineages as well as endothelial cells that revascularize adult retina. We also show that recruitment of endothelial precursors to sites of ischemic injury has a significant role in neovascularization.

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PubMedDate not supplied

Stem cell plasticity or fusion: two approaches to targeted cell therapy.

The possibility the adult stem cells may be able to differentiate along atypical developmental pathways has garnered widespread attention. Recent papers have demonstrated that some "plasticity" arises as a result of cellular fusion events. This review attempts to highlight and reconcile the current data on both sides of the plasticity debate.

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