摘要:

AbstractIn cultures of normal mouse fetal liver cells, combination of stem cell factor (SCF) with erythropoietin enhanced erythroid colony formation and, in bone marrow cultures, combination of SCF with interleukin 6 (IL‐6) enhanced megakaryocyte colony formation. Combination in marrow cultures of SCF and granulocyte colony stimulating factor (G‐CSF) increased cell numbers more than tenfold in developing granulocytic and blast cell colonies. Combination with G‐CSF enhanced progenitor cell numbers fivefold in developing blast colonies, but a majority of these were committed macrophage progenitor cells not able to proliferate further with SCF plus G‐CSF. Similarly, many of the granulocyte progenitor cells could not proliferate further with this combination of stimuli. This process of amplified but abortive formation of progenitor cells was also noted with use of the combination of SCF plus IL‐6 but not with combination of SCF with granulocyte‐macrophage CSF (GM‐CSF) or Multi‐CSF (IL‐3). Analysis indicated that where colony size was amplified by combination of a factor with SCF, quantitatively the more important process was amplification of progenitor cell formation rather than amplification of the number of progeny formed by individual committed

ISSN:1066-5099    

DOI:10.1002/stem.5530110803

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractBinding of the Steel factor (SLF) to the product of thec‐kitproto‐oncogene stimulates the receptor's intrinsic tyrosine kinase that phosphorylates a set of cytoplasmic signaling molecules. Germ‐line mutations in the genes that encode the receptor or the ligand result in remarkably similar phenotypes that affect melanogenesis, erythropoiesis and gametogenesis in mice. We concentrated on the initial events of the signal transduction pathway that underlies these processes. The extracellular portion of Kit is comprised of five immunoglobulin‐(Ig)‐like domains. Ligand binding to this domain induces rapid and extensive dimerization of the receptor molecules in a mechanism that involves monovalent binding of the dimeric ligand, followed by an increase in receptors' affinity and gradual stabilization of the dimers. It thus appears that Kit has at least two functions: ligand binding and ligand‐induced receptor dimerization, in addition to the kinase activity. Both functions are independent of the transmembrane and cytoplasmic domains, as a recombinant soluble ectodomain retained high affinity to SLF and ligand‐dependent dimerization. In order to correlate these functions with specific structures, we employed ligand‐competitive monoclonal antibodies, soluble deletion mutants of the ectodomain and chimeric human‐mouse Kit proteins. These approaches indicated that the N‐terminal three Ig‐like domains constitute the binding site, whose core is the second domain. Further experiments suggested that a putative dimerization site is distinct from the binding cleft and may be located on the

ISSN:1066-5099    

DOI:10.1002/stem.5530110804

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractHepatocyte growth factor/scatter factor (HGF/SF) is secreted by cells of mesodermal origin and shows powerful mitogenic, motogenic and morphogenic activities on epithelial and endothelial cells. It is a heparin‐binding polypeptide with an α/β heterodimeric structure, showing structural homologies with enzymes of the blood clotting cascade. HGF binds with high affinity to the receptor encoded by theMETprotooncogene (p190MET). TheMETreceptor is a heterodimer of two disulfide‐linked subunits (α and β); the α subunit is extracellular, while the β is transmembrane and endowed with tyrosine kinase activity. The HGF‐triggered signaling is mediated by different cytoplasmic effectors, including phosphatidylinositol 3‐kinase, phospholipase C‐γ, and Src‐related tyrosine kinases. p190METis expressed in several normal epithelial tissues (e.g., liver, gastrointestinal tract, kidney) and is often overexpressed in neoplastic cells. p190METexpression has been reported also in central nervous system microglia, a monocyte‐derived cell population. We recently found that p190METis expressed in selected peripheral blood cell populations, such as macrophages. The amount of both mRNA and protein is barely detectable, while it is dramatically increased upon activation. These findings suggest that HGF may play a role in hemopoietic cell signaling, during activation and differentiation of

ISSN:1066-5099    

DOI:10.1002/stem.5530110805

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe past few years have seen considerable advances in the development of the methodologies for discovering novel genes critical to hematopoietic stem cell function and for analyzing their biological role in hematopoiesis. This review briefly discusses some common themes that are emerging from the molecular genetic approaches to hematopoietic stem cell function.

ISSN:1066-5099    

DOI:10.1002/stem.5530110806

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractGranulocyte colony stimulating factor (G‐CSF) has been shown to increase peripheral blood progenitor cells (PBPC) which have an enhanced engraftment potential in autologous transplantation compared with bone marrow cells. The data presented in this study demonstrate the ability of low doses of stem cell factor (SCF) to synergize with G‐CSF to enhance the mobilization of PBPC, compared with G‐CSF alone, in both mouse and primate models. In the mouse model the combination of SCF plus G‐CSF stimulated an absolute increase in cells with in vivo repopulating potential. These studies suggest a possible role for SCF plus G‐CSF in the clinical setting for increased mobilization of PBPC, giving rise to increased phoresis yields and enhanced engraftment for support of high‐dose c

ISSN:1066-5099    

DOI:10.1002/stem.5530110807

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractIn both murine and human systems the c‐kitligand, also known as mast cell growth factor (MGF), acts synergistically with several colony stimulating factors, including the granulocyte‐macrophage colony stimulating factor (GM‐CSF) and interleukin 3 (IL‐3), in stimulating the proliferation and differentiation of different types of hematopoietic progenitors. In addition, MGF is also known to enhance the effects of GM‐CSF and IL‐3 on the in vitro proliferative activity of myeloid leukemic cells. MGF synergizes with a number of other cytokines such as GM‐CSF, IL‐3, IL‐2, IL‐4, IL‐6 and IL‐9 in sustaining the proliferation of growth factor dependent M‐07e cells. In order to explore the molecular basis of this synergistic activity and to elucidate the regulatory mechanisms of c‐kitexpression, we investigated the effects of GM‐CSF, IL‐3 and MGF on c‐kitmRNA and protein levels in M‐07e cells. GM‐CSF, unlike MGF and IL‐3, induced a transient but significant increase of c‐kitmRNA levels. Moreover, following MGF and GM‐CSF treatment, c‐kitprotein expression in M‐07e cells decreased, whereas all the other cytokines tested are unable to modulate c‐kitprotein. These data together with the results of protein turnover analysis suggest that MGF and GM‐CSF regulate c‐kitexpression at the post‐transcriptional level. In addition, the finding that IL‐3 has no detectable effect on c‐kitexpression raises the possibility that GM‐CSF‐induced c‐kitregulation is not mediated by the common signal transduc

ISSN:1066-5099    

DOI:10.1002/stem.5530110808

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractSorted fractions from mouse bone marrow containing highly purified hemopoietic stem and progenitor cells were studied for the expression of growth factor receptors. With the use of rhodamine 123 WGA+, 15–1.1−, low density cells were separated into quiescent pluripotent stem cells and committed progenitor cells. RNA was extracted and cDNA was prepared by reverse transcription. Using primers specific for growth factor receptors, the cDNA of each sorted fraction was amplified by polymerase chain reaction (PCR).The quiescent rhodamine 123 dull stem cell fraction was found to express the interleukin 3 (IL‐3) receptor β unit and c‐kit, but not the granulocyte‐macrophage colony stimulating factor (GM‐CSF) receptor β unit norflk‐2. The rhodamine 123 bright fraction with activated stem cells and mostly committed progenitor cells similarly expressed the IL‐3‐Rβ, and c‐kit.However, this fraction also expressedflk‐2 and GM‐CSF‐Rβ.Since the expression of c‐kitin the stem cell fraction does not correspond with the poor response to the kit‐ligand stem cell factor (SCF) by these cells, we further analyzed the fractions with respect to their binding of biotinylated SCF. The SCF‐binding cells were found to be all rhodamine 123 bright This indicates that the expression of c‐kitis not sufficient to yield a functional receptor for SCF; c‐kitprobably needs a partner molecule to form a functional high‐affinity binding site for SCF. Similar to the β unit of the GM‐CSF receptor10, this partner is then not expressed in the stem cell fraction. Its expression would be upregulated upon differentiation and commitment. It may be speculated that this partner molecule of c‐kitisflk‐2. Alternatively, it may be speculated that the stem cells contain an isoform splice product of ki

ISSN:1066-5099    

DOI:10.1002/stem.5530110809

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractWe have studied the frequency of colony forming cells (CFC) in fetal and neonatal blood in comparison with adult blood and marrow. Fetal/neonatal blood contains at least as many CFC as adult marrow and higher numbers of the more primitive CFC—those CFC giving rise to colonies composed of erythroid and myeloid cells. CD34+cord blood cells (selected either by sorting, panning or affinity chromatography) proliferate in culture over time and generate more CFC (from pre‐CFC) and differentiated cells in response to Steel factor plus different hematopoietic growth factors. Steel factor is unable to stimulate cell growth by itself under serum‐deprived conditions and requires the synergistic action of erythropoietin (Epo), granulocyte colony stimulating factor (G‐CSF) or interleukin 3 (IL‐3). In the presence of Epo or G‐CSF, CFC and differentiated cells are generated for 15 days and are mainly erythroid or granulocytic, respectively. In contrast, Steel factor plus IL‐3 generates multilineage CFC and differentiated cells for more than one month. When the conditions for these long‐term suspension cultures were optimized (37°C, regular refeeding with fresh growth factors and media without changing the flask), CFC and differentiated cells were generated for more than two months. At this time, CFC were no longer detectable and all cells had a mast cell phenotype. These cells have been maintained and propagated for more than eight months in the presence of IL‐3 and Steel factor and may represent a useful tool to study human mast cell differentiation. Finally, the addition of oligonucleotides antisense to c‐kit, the receptor for Steel factor, selectively suppresses the generation of erythroid cells, indicating that Steel factor/c‐kitinteraction plays a major role in the process o

ISSN:1066-5099    

DOI:10.1002/stem.5530110810

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractThe use of cytokines to improve peripheral blood stem cell enhancement and recruitment has recently received close attention. Three main cytokines have been, or are still being, investigated in this way in human clinical trials so far: recombinant human granulocyte‐macrophage colony stimulating factor (rhGM‐CSF), granulocyte CSF (rhG‐CSF) and interleukin 3 (IL‐3). While cytokines used alone appear undoubtedly capable of a marked peripheral blood stem cell (PBSC) enhancement, their combination with a chemotherapy priming often increases this phenomenon. This is particularly evident with rhIL‐3, which is an earlier acting cytokine than rhGM‐CSF and rhG‐CSF. rhIL‐3 priming alone leads to only a minor elevation of circulating progenitor cells, while its combination with chemotherapy and/or a late acting cytokine may allow enhancement and recruitment of large amounts of PBSC.The effect of cytokines on PBSC enhancement may also be at least partially thwarted by various factors. Additionally, their adequate dosage often remains uncertain. So it is presently too early to determine what is actually the most appropriate cytokine or cytokine combination to improve PBSC enhancement Also the risk of stimulation of tumor clonogenic cells in some malignant diseases remains, and the experimenters should be as cautious as possible to not jeopardize the p

ISSN:1066-5099    

DOI:10.1002/stem.5530110811

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY

摘要:

AbstractClinical investigators have found that the hematopoietic system irreversibly damaged by cancer therapy with myeloablative high doses of chemoradiotherapy can be reconstituted by transplantation of autologous hematopoietic progenitors retrieved from peripheral blood. In comparison with patients transplanted with bone marrow, those who receive peripheral blood progenitors undergo shorter periods of neutropenia and thrombocytopenia, require less platelet and erythrocyte transfusions and, most importantly, experience overall reduced treatment‐related morbidity. In this article, we speculate that an explanation for this clinical achievement may be that committed hematopoietic progenitors as well as ancestral uncommitted pluripotent stem cells are retrieved from circulation and transplanted after myeloablative cancer therapy. As indicated by studies in rodents, transplantation of hematopoietic progenitors is followed by two phases of engraftment associated with progenitors at different stages of maturation. An initial phase corresponding to early hematopoietic recovery is produced by committed progenitors, and a second sustained engraftment phase is produced by the pluripotent stem cell. Should this multiphase engraftment model be true of humans also, the exceptionally prompt and sustained blood cell count recovery achieved by transplanting blood progenitor cells may reflect transplantation of heterogeneous progenitors such as committed progenitors and pluripotent stem cells producing an early engraftment phase and then sustained hematopoiesis, respectivel

ISSN:1066-5099    

DOI:10.1002/stem.5530110812

出版商:John Wiley&Sons, Ltd.    

年代:1993

数据来源: WILEY