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      Peripheral Blood Mononuclear Cells Acquire Myofibroblast Characteristics in Granulation Tissue

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          Abstract

          Background: Bone marrow-derived cell populations possess progenitor cell capacities. Emerging evidence also suggests significant plasticity of differentiated mononuclear cell lineages. We therefore assessed the distribution of transplanted peripheral blood mononuclear cells (PBMCs) in granulation tissue formation, and evaluated their possible transdifferentiation into myofibroblasts. Methods: Silastic tubes were inserted into the peritoneal cavity of rats, followed by injection of PKH26-labelled PBMCs isolated from donor animals. At 3, 14 and 21 days, the distribution of PKH26<sup>+</sup> cells as well as their colocalization with myofibroblast/smooth muscle cell [α-smooth muscle (α-SM) actin] or macrophage markers (ED1/ED2) were determined. Results: Round-shaped PKH26<sup>+</sup> cells accumulated around the implants at 3 days, while myofibroblasts were rare. Later, peritoneal granulation tissue constituted an inner, multilayered capsule primarily comprising α-SM actin<sup>+</sup> cells that was surrounded by more loosely organized inflammatory connective tissue. PKH26-labelled, spindle-shaped cells were abundantly found in tissue capsules. As a key finding, granulation tissue at 14 and 21 days contained cells with both PKH26 and α-SM actin labelling. Accordingly, a subpopulation of cells staining positive for macrophage markers showed a spindle-shaped morphology and α-SM actin expression. Conclusions: Transplanted PBMCs contribute to granulation tissue, and acquire myofibroblast characteristics during de novo tissue formation. Mononuclear cells may transdifferentiate into myofibroblast-like cells within an inflammatory environment.

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          Most cited references 13

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          Endothelial progenitor cells: characterization and role in vascular biology.

          Infusion of different hematopoietic stem cell populations and ex vivo expanded endothelial progenitor cells augments neovascularization of tissue after ischemia and contributes to reendothelialization after endothelial injury, thereby, providing a novel therapeutic option. However, controversy exists with respect to the identification and the origin of endothelial progenitor cells. Overall, there is consensus that endothelial progenitor cells can derive from the bone marrow and that CD133/VEGFR2 cells represent a population with endothelial progenitor capacity. However, increasing evidence suggests that there are additional bone marrow-derived cell populations (eg, myeloid cells, "side population" cells, and mesenchymal cells) and non-bone marrow-derived cells, which also can give rise to endothelial cells. The characterization of the different progenitor cell populations and their functional properties are discussed. Mobilization and endothelial progenitor cell-mediated neovascularization is critically regulated. Stimulatory (eg, statins and exercise) or inhibitory factors (risk factors for coronary artery disease) modulate progenitor cell levels and, thereby, affect the vascular repair capacity. Moreover, recruitment and incorporation of endothelial progenitor cells requires a coordinated sequence of multistep adhesive and signaling events including adhesion and migration (eg, by integrins), chemoattraction (eg, by SDF-1/CXCR4), and finally the differentiation to endothelial cells. This review summarizes the mechanisms regulating endothelial progenitor cell-mediated neovascularization and reendothelialization.
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            Endothelial progenitor cells: mobilization, differentiation, and homing.

            Postnatal bone marrow contains a subtype of progenitor cells that have the capacity to migrate to the peripheral circulation and to differentiate into mature endothelial cells. Therefore, these cells have been termed endothelial progenitor cells (EPCs). The isolation of EPCs by adherence culture or magnetic microbeads has been described. In general, EPCs are characterized by the expression of 3 markers, CD133, CD34, and the vascular endothelial growth factor receptor-2. During differentiation, EPCs obviously lose CD133 and start to express CD31, vascular endothelial cadherin, and von Willebrand factor. EPCs seem to participate in endothelial repair and neovascularization of ischemic organs. Clinical studies using EPCs for neovascularization have just been started; however, the mechanisms stimulating or inhibiting the differentiation of EPC in vivo and the signals causing their migration and homing to sites of injured endothelium or extravascular tissue are largely unknown at present. Thus, future studies will help to explore areas of potential basic research and clinical application of EPCs.
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              Intravenous transfusion of endothelial progenitor cells reduces neointima formation after vascular injury.

              Endothelial cell damage is one important pathophysiological step of atherosclerosis and restenosis after angioplasty. Accelerated reendothelialization impairs neointima formation. We evaluated the role of intravenously transfused endothelial progenitor cells (EPCs) on reendothelialization and neointima formation in a mouse model of arterial injury. Spleen-derived mouse mononuclear cells (MNCs) were cultured in endothelial basal medium. A total of 91.8+/-3.2% of adherent cells showed uptake of acetylated low-density lipoprotein (Dil-Ac-LDL) and lectin binding after 4 days. Immunostaining and long-term cultures confirmed the endothelial progenitor phenotype. To determine the effect of stem cell transfusion on reendothelialization, mice received either fluorescent-labeled spleen-derived MNCs or in vitro differentiated EPCs intravenously after endothelial injury of the carotid artery. Transfused cells were strictly restricted to the injury site, and lectin binding confirmed the endothelial phenotype. Homing of transfused cells to the site of injury was only detectable in splenectomized mice. Cell transfusion caused enhanced reendothelialization associated with a reduction of neointima formation. Systemically applied spleen-derived MNCs and EPCs home to the site of vascular injury, resulting in an enhanced reendothelialization associated with decreased neointima formation. These results allow novel insights in stem cell biology and provide additional information for the treatment of vascular dysfunction and prevention of restenosis after angioplasty. The full text of this article is available online at http://www.circresaha.org.
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                Author and article information

                Journal
                JVR
                J Vasc Res
                10.1159/issn.1018-1172
                Journal of Vascular Research
                S. Karger AG
                1018-1172
                1423-0135
                2005
                April 2005
                13 April 2005
                : 42
                : 2
                : 174-180
                Affiliations
                aDepartment of Hematology/Oncology, Winship Cancer Institute and bBone Marrow and Stem Cell Transplantation Center, Emory University School of Medicine, Atlanta, Ga., USA
                Article
                84406 J Vasc Res 2005;42:174–180
                10.1159/000084406
                15767764
                © 2005 S. Karger AG, Basel

                Copyright: All rights reserved. No part of this publication may be translated into other languages, reproduced or utilized in any form or by any means, electronic or mechanical, including photocopying, recording, microcopying, or by any information storage and retrieval system, without permission in writing from the publisher. Drug Dosage: The authors and the publisher have exerted every effort to ensure that drug selection and dosage set forth in this text are in accord with current recommendations and practice at the time of publication. However, in view of ongoing research, changes in government regulations, and the constant flow of information relating to drug therapy and drug reactions, the reader is urged to check the package insert for each drug for any changes in indications and dosage and for added warnings and precautions. This is particularly important when the recommended agent is a new and/or infrequently employed drug. Disclaimer: The statements, opinions and data contained in this publication are solely those of the individual authors and contributors and not of the publishers and the editor(s). The appearance of advertisements or/and product references in the publication is not a warranty, endorsement, or approval of the products or services advertised or of their effectiveness, quality or safety. The publisher and the editor(s) disclaim responsibility for any injury to persons or property resulting from any ideas, methods, instructions or products referred to in the content or advertisements.

                Page count
                Figures: 5, References: 25, Pages: 7
                Categories
                Research Paper

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