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  • 1
    Keywords: CELLS ; EXPRESSION ; BLOOD ; CELL ; Germany ; human ; PROTEIN ; PROTEINS ; DIFFERENTIATION ; CONTRAST ; BINDING ; fibroblasts ; culture ; VECTORS ; VECTOR ; NUMBER ; RATES ; COMPONENT ; MODULATION ; CANCER-CELLS ; LENGTH ; STEM-CELLS ; telomerase ; PROGENITOR CELLS ; HEMATOPOIETIC PROGENITOR CELLS ; RETROVIRAL VECTORS ; APLASTIC-ANEMIA ; BINDING PROTEIN ; cord blood ; HUMAN-LYMPHOCYTES ; CYTOKINE ; BINDING-PROTEIN ; fibroblast ; CAPACITY ; aging ; LINEAGE ; flow-FISH ; HUMAN BONE-MARROW ; REPLICATIVE LIFE-SPAN ; SERIAL TRANSPLANTATION ; stem cells ; telomere length
    Abstract: Loss of telomeric repeats has been causally linked to replicative senescence and aging in human cells. In contrast to normal somatic cells, which are telomerase-negative, hematopoietic stem cells have low levels of telomerase, which can be transiently upregulated upon cytokine stimulation. To examine whether ectopic expression of telomerase can overcome telomere erosion in hematopoietic progenitor cells, we overexpressed telomerase in CD34(+) and AC133(+) cord blood (CB) cells using retroviral vectors containing hTERT, the catalytic component of telomerase. Although the hTERT-transduced CB cells exhibited significantly elevated telomerase activity (approximately 10-fold), the mean telomere length was only increased up to 600 bp, which was in contrast to hTERT-transduced fibroblast cells gaining more than 2-kb telomeric repeats. Moreover, ectopic telomerase activity did not prevent overall telomere shortening, which was in the range of 1.3 kb in serum-free expansion culture. We also blocked endogenous telomerase activity by ectopic expression of dominant-negative hTERT. Whereas CB cells with absent telomerase activity showed reduced absolute numbers of colony-forming cells, we observed increased rates only for burst-forming units erythroid when the enzyme was overexpressed. These results suggest that telomere shortening in human hematopoietic progenitor cells cannot be compensated by increased levels of telomerase alone and is likely to be dependent on other factors, such as telomere binding proteins. Furthermore, telomerase function seems to be directly associated with the proliferative capacity of stem cells and may exert an additional role in lineage differentiation
    Type of Publication: Journal article published
    PubMed ID: 15342938
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  • 2
    Abstract: Mesenchymal stem cells (MSC) display unique suppressive properties on T-cell immunity, thus representing an attractive vehicle for the treatment of conditions associated with harmful T-cell responses such as organ-specific autoimmunity and graft-versus-host disease. Toll-like receptors (TLR) are primarily expressed on antigen-presenting cells and recognize conserved pathogen-derived components. Ligation of TLR activates multiple innate and adaptive immune response pathways to eliminate and protect against invading pathogens. In this work, we show that TLR expressed on human bone marrow-derived MSC enhanced the immunosuppressive phenotype of MSC. Immunosuppression mediated by TLR was dependent on the production of immunosuppressive kynurenines by the tryptophan-degrading enzyme indoleamine-2,3-dioxygenase-1 (IDO1). Induction of IDO1 by TLR involved an autocrine interferon (IFN)-beta signaling loop, which was dependent on protein kinase R (PKR), but independent of IFN-gamma. These data define a new role for TLR in MSC immunobiology, which is to augment the immunosuppressive properties of MSC in the absence of IFN-gamma rather than inducing proinflammatory immune response pathways. PKR and IFN-beta play a central, previously unidentified role in orchestrating the production of immunosuppressive kynurenines by MSC.
    Type of Publication: Journal article published
    PubMed ID: 19353519
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  • 3
    Keywords: proliferation ; ACTIVATION ; SUPPRESSION ; TRANSGENE EXPRESSION ; RNA INTERFERENCE ; LENTIVIRAL VECTOR ; BONE ; SELF-RENEWAL ; MICRORNA ; tetracycline
    Abstract: Hematopoietic stem cells (HSC) are probably the best understood somatic stem cells and often serve as a paradigm for other stem cells. Nevertheless, most current techniques to genetically manipulate them in vivo are either constitutive and/or induced in settings of hematopoietic stress such as after irradiation. Here, we present a conditional expression system that allows for externally controllable transgenesis and knockdown in resident HSCs, based on a lentiviral vector containing a tet-O sequence and a transgenic mouse line expressing a doxycyclin-regulated tTR-KRAB repressor protein. HSCs harvested from tTR-KRAB mice are transduced with the lentiviral vector containing a cDNA (i.e., Green Fluorescent Protein (GFP)) and/or shRNA (i.e., p53) of interest and then transplanted into lethally irradiated recipients. While the vector is effectively repressed by tTR-KRAB during homing and engraftment, robust GFP/shp53 expression is induced on doxycyclin treatment in HSCs and their progeny. Doxycylin-controllable transcription is maintained on serial transplantation, indicating that repopulating HSCs are stably modified by this approach. In summary, this easy to implement conditional system provides inducible and reversible overexpression or knock down of genes in resident HSCs in vivo using a drug devoid of toxic or activating effects.
    Type of Publication: Journal article published
    PubMed ID: 20641037
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  • 4
    Keywords: IN-VIVO ; DIFFERENTIATION ; MICE ; SELECTION ; INTEGRATION SITES ; PERIPHERAL-BLOOD ; VECTOR INTEGRATION ; ENGRAFTMENT ; IPS CELLS ; SCID-X1 GENE-THERAPY
    Abstract: A patient with beta(E) /beta(0) -thalassemia major was converted to transfusion-independence 4.5 years ago by lentiviral gene transfer in hematopoietic stem cells while showing a myeloid-biased cell clone. Induced pluripotent stem cells (iPSCs) are a potential alternative source of hematopoietic stem cells. If fetal to adult globin class, switching does not occur in vivo in iPSC-derived erythroid cells, beta-globin gene transfer would be unnecessary. To investigate both vector integration skewing and the potential use of iPSCs for the treatment of thalassemia, we derived iPSCs from the thalassemia gene therapy patient and compared iPSC-derived hematopoietic cells to their natural isogenic somatic counterparts. In NSG immunodeficient mice, embryonic to fetal and a partial fetal to adult globin class switching were observed, indicating that the gene transfer is likely necessary for iPSC-based therapy of the beta-hemoglobinopathies. Lentivector integration occurred in regions of low and high genotoxicity. Surprisingly, common integration sites (CIS) were identified across those iPSCs and cells retrieved from isogenic and nonisogenic gene therapy patients with beta-thalassemia and adrenoleukodystrophy, respectively. This suggests that CIS observed in the absence of overt tumorigenesis result from nonrandom lentiviral integration rather than oncogenic in vivo selection. These findings bring the use of iPSCs closer to practicality and further clarify our interpretation of genome-wide lentivector integration. Stem Cells 2013;31:1785-1794.
    Type of Publication: Journal article published
    PubMed ID: 23712774
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  • 5
    Abstract: Hematopoietic stem cells (HSCs) maintain blood cell production life-long by their unique abilities of self-renewal and differentiation into all blood cell lineages. Growth arrest and DNA-damage-inducible 45 alpha (GADD45A) is induced by genotoxic stress in HSCs. GADD45A has been implicated in cell cycle control, cell death and senescence, as well as in DNA-damage repair. In general, GADD45A provides cellular stability by either arresting the cell cycle progression until DNA damage is repaired or, in cases of fatal damage, by inducing apoptosis. However, the function of GADD45A in hematopoiesis remains controversial. We revealed the changes in murine HSC fate control orchestrated by the expression of GADD45A at single cell resolution. In contrast to other cellular systems, GADD45A expression did not cause a cell cycle arrest or an alteration in the decision between cell survival and apoptosis in HSCs. Strikingly, GADD45A strongly induced and accelerated the differentiation program in HSCs. Continuous tracking of individual HSCs and their progeny via time-lapse microscopy elucidated that once GADD45A was expressed, HSCs differentiate into committed progenitors within 29 hours. GADD45A-expressing HSCs failed to long-term reconstitute the blood of recipients by inducing multilineage differentiation in vivo. Importantly, gamma-irradiation of HSCs induced their differentiation by upregulating endogenous GADD45A. The differentiation induction by GADD45A was transmitted by activating p38 Mitogen-activated protein kinase (MAPK) signaling and allowed the generation of megakaryocytic-erythroid, myeloid, and lymphoid lineages. These data indicate that genotoxic stress-induced GADD45A expression in HSCs prevents their fatal transformation by directing them into differentiation and thereby clearing them from the system. Stem Cells 2016;34:699-710.
    Type of Publication: Journal article published
    PubMed ID: 26731607
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  • 6
    Abstract: Skeletal metastasis of breast cancer is associated with a poor prognosis and significant morbidity. Investigations in other solid tumors have revealed an impairment in hematopoietic function upon bone marrow invasion. However, the interaction between disseminated breast cancer cells and the bone marrow microenvironment which harbors them has not been addressed comprehensively. Employing advanced co-culture assays, proteomic studies, organotypic models as well as in vivo xenotransplant models, we define the consequences of this interaction on the stromal compartment of bone marrow, affected molecular pathways and subsequent effects on the hematopoietic stem and progenitor cells (HSPCs). The results showed a basic fibroblast growth factor (bFGF)-mediated, synergistic increase in proliferation of breast cancer cells and mesenchymal stromal cells (MSCs) in co-culture. The stromal induction was associated with elevated phosphoinositide-3 kinase (PI3K) signaling in the stroma, which coupled with elevated bFGF levels resulted in increased migration of breast cancer cells towards the MSCs. The perturbed cytokine profile in the stroma led to reduction in the osteogenic differentiation of MSCs via downregulation of platelet-derived growth factor-BB (PDGF-BB). Long term co-cultures of breast cancer cells, HSPCs, MSCs and in vivo studies in NOD.Cg-Prkdc(scid) Il2rg(tm1Wjl) /SzJ (NSG) mice showed a reduced support for HSPCs in the altered niche. The resultant non- conducive phenotype of the niche for HSPC support emphasizes the importance of the affected molecular pathways in the stroma as clinical targets. These findings can be a platform for further development of therapeutic strategies aiming at the blockade of bone marrow support to disseminated breast cancer cells. Stem Cells 2016;34:2224-2235.
    Type of Publication: Journal article published
    PubMed ID: 27090603
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  • 7
  • 8
    Keywords: CELLS ; EXPRESSION ; Germany ; POPULATION ; SITE ; SITES ; CDNA ; GENE ; GENE-EXPRESSION ; GENES ; microarray ; transcription ; ASSOCIATION ; BONE-MARROW ; gene expression ; IMMUNODEFICIENT MICE ; HUMAN GENOME ; STEM-CELLS ; PROGENITOR CELLS ; CD34(+) CELLS ; HEMATOPOIETIC-CELLS ; INTEGRATION SITE ; INTEGRATION ; molecular ; SUBSET ; FRACTION ; targeted ; ARRAY ; gene targeting ; intensity ; RESISTANCE 1 GENE ; EXPRESSED GENES ; CD34(+) ; hematopoietic stem cell ; MOBILIZED PERIPHERAL-BLOOD ; REPOPULATING CELLS ; retroviral vector integration ; START REGIONS ; TRANSCRIPT PROFILING ANALYSIS
    Abstract: In this study, we analyzed whether retroviral integration sites in repopulating hematopoietic cells correlate with genes expressed in fractions enriched in hematopoietic stem cells (HSCs). We have previously described microarray studies of two populations enriched in HSCs: CD34(+)/CD38(-) and the slow dividing fraction of CD34(+)/CD38(-) cells (SDF). Furthermore, we demonstrated that oncoretroviral integrations in severe combined immunodeficient repopulating cells are preferentially located near the transcription start. Here, we have identified 117 corresponding cDNA clones on our microarray representing genes with retroviral integration sites. These genes revealed a higher mean signal intensity in comparison with either all genes on the array or a subset of control genes with retroviral integrations in HeLa cells. Furthermore, these genes demonstrated a higher expression in CD34(+)/CD38(-) cells and SDF. The association of gene expression and retrovirally targeted genes observed here will help to elucidate the molecular characteristics of primitive repopulating hematopoietic cells
    Type of Publication: Journal article published
    PubMed ID: 16140869
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  • 9
    Keywords: CELLS ; tumor ; BLOOD ; CELL ; Germany ; human ; IN-VIVO ; MODEL ; THERAPY ; FOLLOW-UP ; QUANTIFICATION ; LONG-TERM ; GENE ; gene therapy ; TIME ; TRANSDUCTION ; gene transfer ; GENE-TRANSFER ; TRANSPLANTATION ; BIOLOGY ; BREAST-CANCER ; NO ; resistance ; VECTOR ; IMMUNODEFICIENT MICE ; STEM-CELLS ; PROGENITOR CELLS ; POLYMERASE-CHAIN-REACTION ; CHAIN-REACTION ; HEMATOPOIETIC-CELLS ; PERIPHERAL-BLOOD ; MULTIDRUG-RESISTANCE ; RESISTANCE MDR-1 GENE ; retroviral vector ; insertional mutagenesis ; LACKING ; multidrug resistance ; CHAIN ; ONCOLOGY ; THERAPIES ; polymerase chain reaction ; P-GLYCOPROTEIN ; BONE-MARROW-CELLS ; stem cells ; LEVEL ; USA ; progenitor cell ; microbiology ; STEM ; PROGENITOR-CELL ; rhesus macaque ; biotechnology ; CD34+ ; DOMINANCE ; long-term follow-up ; multidrug resistance 1
    Abstract: Previous murine studies have suggested that retroviral multidrug resistance 1 ( MDR1) gene transfer may be associated with a myeloproliferative disorder. Analyses at a clonal level and prolonged long-term follow-up in a model with more direct relevance to human biology were lacking. In this study, we analyzed the contribution of individual CD34selected peripheral blood progenitor cells to long-term rhesus macaque hematopoiesis after transduction with a retroviral vector either expressing the multidrug resistance 1 gene ( HaMDR1 vector) or expressing the neomycin resistance ( NeoR) gene ( G1Na vector). We found a total of 122 contributing clones from 8 weeks up to 4 years after transplantation. One hundred two clones contained the G1Na vector, whereas only 20 clones contained the HaMDR1 vector. Here, we show for the first time realtime polymerase chain reaction based quantification of individual transduced cell clones constituting 0.0008% +/- 0.0003% to 0.0041% +/- 0.00032% of primate peripheral blood cells. No clonal dominance was observed
    Type of Publication: Journal article published
    PubMed ID: 17615269
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  • 10
    Keywords: CELLS ; EXPRESSION ; GROWTH ; IN-VITRO ; CELL ; Germany ; human ; IN-VIVO ; VITRO ; POPULATION ; GENE-EXPRESSION ; PROTEIN ; TISSUE ; MICE ; primary ; TISSUES ; BIOLOGY ; ASSAY ; NUMBER ; leukemia ; STEM-CELLS ; PROGENITOR CELLS ; CD34(+) CELLS ; molecular ; ONCOLOGY ; RE ; INCREASE ; ACUTE MYELOID-LEUKEMIA ; TRANSPORTER ; BONE-MARROW-CELLS ; HEMATOPOIESIS ; stem cells ; USA ; REPOPULATING CELLS ; microbiology ; STEM ; biotechnology ; ABCG2 ; FORCED EXPRESSION ; human progenitor cells ; POPULATION STEM-CELLS ; SIDE-POPULATION ; SP PHENOTYPE
    Abstract: The ATP-binding cassette transporter, ABCG2, is a molecular determinant of the side population phenotype, which is enriched for stem and progenitor cells in various nonhematopoietic and hematopoietic tissues. ABCG2 is highly expressed in hematopoietic progenitors and silenced in differentiated hematopoietic cells, suggesting a role of ABCG2 in early hematopoiesis. To test whether ABCG2 is involved in human hematopoietic development, we retrovirally transduced umbilical cord blood-derived early hematopoietic cells and analyzed hematopoiesis in vitro and in vivo. ABCG2 increased the number of clonogenic progenitors in vitro, including the most primitive colony-forming unit-granulocyte, erythroid, macrophage, megakaryocyte, by twofold (n = 14; p 〈 .0005). Furthermore, ABCG2 induced a threefold increase in the replating capacity of primary colonies (n = 9; p 〈 .01). In addition, ABCG2 impaired the development of CD19(+) lymphoid cells in vitro. In transplanted NOD/SCID mice, the ATP-binding cassette transporter decreased the number of human B-lymphoid cells, resulting in an inversion of the lymphoid/myeloid ratio. ABCG2 enhanced the proportion of CD34(+) progenitor cells in vivo (n = 4; p 〈 .05) and enhanced the most primitive human progenitor pool, as determined by limiting dilution competitive repopulating unit assay (p 〈 .034). Our data characterize ABCG2 as a regulatory protein of early human hematopoietic development
    Type of Publication: Journal article published
    PubMed ID: 18055445
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