Project description:Recent studies demonstrate that inflammatory signals regulate hematopoietic stem cells (HSCs). Granulocyte-colony stimulating factor (G-CSF) is often induced with infection and plays a key role in the stress granulopoiesis response. However, its effects on HSCs are less clear. Herein, we show that treatment with G-CSF induces expansion and increased quiescence of phenotypic HSCs, but causes a marked, cell-autonomous HSC repopulating defect associated with induction of toll-like receptor (TLR) expression and signaling. The G-CSF-mediated expansion of HSCs is reduced in mice lacking TLR2, TLR4 or the TLR signaling adaptor MyD88. Induction of HSC quiescence is abrogated in mice lacking MyD88 or in mice treated with antibiotics to suppress intestinal flora. Finally, loss of TLR4 or germ free conditions mitigates the G-CSF-mediated HSC repopulating defect. These data suggest that low level TLR agonist production by commensal flora contributes to the regulation of HSC function and that G-CSF negatively regulates HSCs, in part, by enhancing TLR signaling. RNA from KSL SLAM cells (Lineage- c-Kit+ Sca-1+ CD150+ CD48- CD41-) from bone marrow of 5-10 mice per group treated with G-CSF or saline alone was prepared using the RNA XS column kit (Machery-Nagel), amplified using the NuGen Ovation system (NuGen) and hybridized to the MoGene 1.0 ST array. This array includes 3 independent PBS control and 3 G-CSF treated groups.
Project description:Recent studies demonstrate that inflammatory signals regulate hematopoietic stem cells (HSCs). Granulocyte-colony stimulating factor (G-CSF) is often induced with infection and plays a key role in the stress granulopoiesis response. However, its effects on HSCs are less clear. Herein, we show that treatment with G-CSF induces expansion and increased quiescence of phenotypic HSCs, but causes a marked, cell-autonomous HSC repopulating defect associated with induction of toll-like receptor (TLR) expression and signaling. The G-CSF-mediated expansion of HSCs is reduced in mice lacking TLR2, TLR4 or the TLR signaling adaptor MyD88. Induction of HSC quiescence is abrogated in mice lacking MyD88 or in mice treated with antibiotics to suppress intestinal flora. Finally, loss of TLR4 or germ free conditions mitigates the G-CSF-mediated HSC repopulating defect. These data suggest that low level TLR agonist production by commensal flora contributes to the regulation of HSC function and that G-CSF negatively regulates HSCs, in part, by enhancing TLR signaling. RNA from KSL SLAM cells (Lineage- c-Kit+ Sca-1+ CD150+ CD48- CD41-) from bone marrow of 5-10 mice per group treated with G-CSF or saline alone was prepared using the RNA XS column kit (Machery-Nagel), amplified using the NuGen Ovation system (NuGen) and hybridized to the MoGene 1.0 ST array. This array includes 4 independent PBS control and 4 G-CSF treated groups.
Project description:CD34+ hematopoietic stem/progenitor cells were isolated from human cord blood and amplified in vitro for 10-14 days in serum-free medium with specific cytokines (Ju et al., Eur. J. Cell Biol. 82, 75-86, 2003; Hacker et al., Nat. Immunol. 4, 380-386, 2003). Cultured progenitor cells were induced to differentiate into DC in RPMI medium supplemented with 10% fetal calf serum, 2 mM L-glutamine, 0.1 microM Beta-mercaptoethanol, 100 U/ml penicillin and streptomycin (GIBCO-BRL) and 500 U/ml GM-CSF, 500 U/ml IL-4 for 6 days with or without 10 ng/ml TGF-beta1 as indicated (0.5x10E6 cells/ml). Every 2 days growth factors were added and cells were maintained at 0.5x10E6 cells/ml cell density. RNA was prepared and subjected to microarray analysis. Experiment Overall Design: Dendritic cells (DC) were treated for various periods of time (4, 16 and 36 hours) with TGF-beta1 (10 ng/ml) or left untreated. Experiment Overall Design: DC untreated Experiment Overall Design: DC + TGF-beta1 for 4 hours Experiment Overall Design: DC + TGF-beta1 for 16 hours Experiment Overall Design: DC + TGF-beta1 for 36 hours
Project description:Although hematopoietic stem and progenitor cells (HSPCs) become activated in the cell-cycle status after chemotherapy to supply hematopoietic loss, the detailed mechanisms of activation remain unknown. Here we show that Sca1+ macrophages play a key role for bone marrow (BM) recovery through granulocyte-macrophage colony-stimulating factor (GM-CSF) secretion. By analyzing gene expression profiles of HSPCs lodged in 5-fluolouracil (5-FU)-treated mice, we found GM-CSF as a key proliferative signal. Sca1+ macrophages in BM after 5-FU treatment expressed high levels of GM-CSF. GM-CSF-knockout mice treated with 5-FU were lethal because of severe BM suppression. Up-regulation of Csf2 in Sca1+ macrophages by 5-FU was suppressed in MyD88-knockout mice, suggesting that TLR signaling via damage-associated molecular patterns caused by cell death is critical for up-regulation of Csf2. In 5-FU treated BM, majority of Sca1+ macrophages and transplanted HSPCs locate perivascular areas. These findings together indicate that Sca1+ macrophages induce HSPCs to proliferate through GM-CSF signaling in the stressed BM environments.
Project description:Although hematopoietic stem and progenitor cells (HSPCs) become activated in the cell-cycle status after chemotherapy to supply hematopoietic loss, the detailed mechanisms of activation remain unknown. Here we show that Sca1+ macrophages play a key role for bone marrow (BM) recovery through granulocyte-macrophage colony-stimulating factor (GM-CSF) secretion. By analyzing gene expression profiles of HSPCs lodged in 5-fluolouracil (5-FU)-treated mice, we found GM-CSF as a key proliferative signal. Sca1+ macrophages in BM after 5-FU treatment expressed high levels of GM-CSF. GM-CSF-knockout mice treated with 5-FU were lethal because of severe BM suppression. Up-regulation of Csf2 in Sca1+ macrophages by 5-FU was suppressed in MyD88-knockout mice, suggesting that TLR signaling via damage-associated molecular patterns caused by cell death is critical for up-regulation of Csf2. In 5-FU treated BM, majority of Sca1+ macrophages and transplanted HSPCs locate perivascular areas. These findings together indicate that Sca1+ macrophages induce HSPCs to proliferate through GM-CSF signaling in the stressed BM environments.
Project description:Granulocyte colony-stimulating factor (G-CSF) has been utilized to treat neutropenia in various clinical settings. Although clearly beneficial, there are concerns that use of G-CSF in certain conditions increases the risk of myelodysplastic syndrome (MDS) and/or acute myeloid leukemia (AML). The most striking example is in severe congenital neutropenia (SCN). SCN patients develop MDS/AML at a high rate that is directly correlated to the cumulative lifetime dosage of G-CSF. MDS and AML that arise in these settings are commonly associated with chromosomal deletions. We demonstrate that chronic G-CSF treatment in mice results in expansion of the hematopoietic stem cell population. Furthermore, primitive hematopoietic progenitors from G-CSF–treated mice show evidence of DNA damage as demonstrated by an increase in double strand breaks and recurrent chromosomal deletions. Concurrent treatment with genistein, a natural soy isoflavone, limits DNA damage in this population. The protective effect of genistein appears to be related to its preferential inhibition of G-CSF–induced proliferation of hematopoietic stem cells. Importantly, genistein does not impair G-CSF–induced proliferation of committed hematopoietic progenitors, nor diminish neutrophil production. The protective effect of genistein was accomplished with plasma levels that are easily attainable through dietary supplementation. aCGH was performed using NimbleGen