PMC:17820 / 6301-9577 JSONTXT

{"project":"2_test","denotations":[{"id":"11056678-1870029-4384037","span":{"begin":468,"end":469},"obj":"1870029"},{"id":"11056678-9027588-4384038","span":{"begin":883,"end":884},"obj":"9027588"},{"id":"11056678-1870029-4384039","span":{"begin":1156,"end":1157},"obj":"1870029"},{"id":"11056678-9027588-4384040","span":{"begin":1158,"end":1159},"obj":"9027588"},{"id":"11056678-10548503-4384041","span":{"begin":1370,"end":1371},"obj":"10548503"},{"id":"11056678-2070060-4384042","span":{"begin":1768,"end":1769},"obj":"2070060"},{"id":"11056678-8790603-4384043","span":{"begin":2611,"end":2612},"obj":"8790603"}],"text":"Introduction\nBone marrow is a complex tissue containing hematopoietic cell progenitors and their progeny and a connective-tissue network of mesenchymally derived cells known as stroma. Marrow stroma includes a subpopulation of undifferentiated cells that are capable of becoming one of a number of phenotypes, including chondrocytes, osteoblasts, adipocytes, fibroblasts, possibly muscle cells, and the reticular cells that support hematopoietic cell differentiation [1,2]. Extensive experimentation has defined conditions for the isolation, propagation, and differentiation in vitro and in vivo of the stromal cells referred to as MSCs. They are a population of firmly adherent cells with a high proliferative capacity and potential for self-renewal. Their developmental potential is retained even after repeated subcultivation in vitro, supporting their designation as stem cells [3].\nIdentification of MSCs in situ has been difficult, partly because they have few unique products or molecular markers. A series of monoclonal antibodies (SH antibodies) purportedly specific reagents have been used to isolate MSCs from a population of bone-marrow cells [1,3]. The one used most often (SH-2) was recently shown to react with endoglin (CD105), a member of the transforming growth factor (TGF)-β receptor family usually found on the endothelium of postcapillary venules [4]. Two other reagents may be more specific. One consists of a group of antibodies to BMP receptors (BMPRs) present on embryonic mesenchyme and postnatally on osteoblasts and chondrocytes [5]. Another antibody, Stro-1 made against marrow fibroblastic cells, blocks hematopoiesis in vitro by interfering with the interaction of reconstituted human hematopoietic stem cells (HSCs) and stromal cells [6].\nAttempts to demonstrate MSCs in peripheral blood have been unrewarding, except for a report by Fernandez et al [7], who identified cells with the features of MSCs in growth-factor-mobilized peripheral-blood cells from breast-cancer patients. Low-density mononuclear cells grown for 1 week in tissue culture with fetal calf serum (FCS) become adherent fibroblast-like cells and a few were large, flat, round cells. Immunohistology and flow cytometric analysis in a fluorescence-activated cell sorter (FACS) revealed fibronectin and three types of collagen (I, III, and VI) in the cytoplasm of the cultured cells. They expressed adhesion ligands and antigens recognized by SH-2 and SH-3 monoclonal antibodies. No stromal cells were demonstrated in normal peripheral-blood cells not mobilized by granulocyte-macrophage CSF [7]. Bucala et al [8] separated human blood cells by density centrifugation, cultured them on a fibronectin matrix, and identified a population of circulating cells that had fibroblast properties and a distinctive phenotype (collagen+/vimentin+/ CD34+). This novel circulating cell, termed a fibrocyte, has both mesenchymal and hematopoietic features.\nNow we report for the first time that cells with the morphology and phenotype of mesenchymal precursors are normally present in the circulation. Hereafter these are referred to as `blood-derived mesenchymal precursor cells' (BMPCs). The observations that support these conclusions and the significance of the findings are discussed."}

{"project":"Colil","denotations":[{"id":"T5","span":{"begin":883,"end":884},"obj":"9027588"},{"id":"T1","span":{"begin":468,"end":469},"obj":"1870029"},{"id":"T2","span":{"begin":1156,"end":1157},"obj":"1870029"},{"id":"T3","span":{"begin":1158,"end":1159},"obj":"9027588"},{"id":"T4","span":{"begin":1768,"end":1769},"obj":"2070060"},{"id":"T6","span":{"begin":2611,"end":2612},"obj":"8790603"},{"id":"T7","span":{"begin":1370,"end":1371},"obj":"10548503"}],"namespaces":[{"prefix":"_base","uri":"http://pubannotation.org/docs/sourcedb/PubMed/sourceid/"}],"text":"Introduction\nBone marrow is a complex tissue containing hematopoietic cell progenitors and their progeny and a connective-tissue network of mesenchymally derived cells known as stroma. Marrow stroma includes a subpopulation of undifferentiated cells that are capable of becoming one of a number of phenotypes, including chondrocytes, osteoblasts, adipocytes, fibroblasts, possibly muscle cells, and the reticular cells that support hematopoietic cell differentiation [1,2]. Extensive experimentation has defined conditions for the isolation, propagation, and differentiation in vitro and in vivo of the stromal cells referred to as MSCs. They are a population of firmly adherent cells with a high proliferative capacity and potential for self-renewal. Their developmental potential is retained even after repeated subcultivation in vitro, supporting their designation as stem cells [3].\nIdentification of MSCs in situ has been difficult, partly because they have few unique products or molecular markers. A series of monoclonal antibodies (SH antibodies) purportedly specific reagents have been used to isolate MSCs from a population of bone-marrow cells [1,3]. The one used most often (SH-2) was recently shown to react with endoglin (CD105), a member of the transforming growth factor (TGF)-β receptor family usually found on the endothelium of postcapillary venules [4]. Two other reagents may be more specific. One consists of a group of antibodies to BMP receptors (BMPRs) present on embryonic mesenchyme and postnatally on osteoblasts and chondrocytes [5]. Another antibody, Stro-1 made against marrow fibroblastic cells, blocks hematopoiesis in vitro by interfering with the interaction of reconstituted human hematopoietic stem cells (HSCs) and stromal cells [6].\nAttempts to demonstrate MSCs in peripheral blood have been unrewarding, except for a report by Fernandez et al [7], who identified cells with the features of MSCs in growth-factor-mobilized peripheral-blood cells from breast-cancer patients. Low-density mononuclear cells grown for 1 week in tissue culture with fetal calf serum (FCS) become adherent fibroblast-like cells and a few were large, flat, round cells. Immunohistology and flow cytometric analysis in a fluorescence-activated cell sorter (FACS) revealed fibronectin and three types of collagen (I, III, and VI) in the cytoplasm of the cultured cells. They expressed adhesion ligands and antigens recognized by SH-2 and SH-3 monoclonal antibodies. No stromal cells were demonstrated in normal peripheral-blood cells not mobilized by granulocyte-macrophage CSF [7]. Bucala et al [8] separated human blood cells by density centrifugation, cultured them on a fibronectin matrix, and identified a population of circulating cells that had fibroblast properties and a distinctive phenotype (collagen+/vimentin+/ CD34+). This novel circulating cell, termed a fibrocyte, has both mesenchymal and hematopoietic features.\nNow we report for the first time that cells with the morphology and phenotype of mesenchymal precursors are normally present in the circulation. Hereafter these are referred to as `blood-derived mesenchymal precursor cells' (BMPCs). The observations that support these conclusions and the significance of the findings are discussed."}