Deciphering the Differential Impact of Thrombopoietin/MPL Signaling on Hematopoietic Stem Cell Function in Bone Marrow and Spleen
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ABSTRACT:
ORGANISM(S): Mus musculus
PROVIDER: GSE249912 | GEO | 2023/12/16
REPOSITORIES: GEO
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Project description:Adult hematopoietic stem cells (HSCs) reside primarily in bone marrow. However, hematopoietic stresses such as myelofibrosis, anemia, pregnancy, infection or myeloablation can mobilize HSCs to the spleen and induce extramedullary hematopoiesis (EMH). While the bone marrow HSC niche has been studied intensively, the EMH niche has received little attention. Here, we systematically assessed the physiological sources of the key niche factors, SCF and CXCL12, in the mouse spleen after EMH induction by cyclophosphamide plus granulocyte colony-stimulating factor, blood loss, or pregnancy. In each case, Scf was expressed by endothelial cells and Tcf21+ stromal cells, primarily around sinusoids in red pulp, while Cxcl12 was expressed by a subset of Tcf21+ stromal cells. EMH induction markedly expanded the Scf-expressing endothelial cells and stromal cells by inducing proliferation. Most splenic HSCs were adjacent to Tcf21+ stromal cells in red pulp. Conditional deletion of Scf from spleen endothelial cells or Scf or Cxcl12 from Tcf21+ stromal cells severely reduced spleen EMH and reduced blood cell counts without affecting bone marrow hematopoiesis. Endothelial cells and Tcf21+ stromal cells thus create the splenic EMH niche, which is necessary for the physiological response to diverse hematopoietic stresses. Unfractionated spleen cells (2 replicates) and FACS-sorted VE-cadherein negative Scf-GFP positive cells (3 replicates)
2015-08-01 | E-GEOD-71288 | biostudies-arrayexpress
Project description:Thrombopoietin (TPO), acting through its receptor Mpl, has two major physiological roles: ensuring production of sufficient platelets via stimulation of megakaryocyte production, and maintaining hematopoietic stem cell (HSC) quiescence. Mpl also controls circulating TPO concentration via receptor-mediated internalisation and degradation. We demonstrate that the megakaryocytosis and increased platelet mass in mice with mutations in the Myb or p300 genes causes reduced circulating TPO concentration and TPO starvation of the stem cell compartment, which is exacerbated because these cells additionally exhibit impaired responsiveness to TPO. Total RNA obtained from bone marrow Lineage- Sca-1+ c-Kit+ cells of mice that were mutant or knocked out for Myb, p300 or Mpl were compared to wild type samples. We have found that HSCs from MybPlt4/Plt4 and p300Plt6/Plt6 mice show altered expression of TPO-responsive genes, suggesting that TPO starvation is an important factor in the hematopoietic phenotypes observed in these mice .
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Project description:Adult hematopoietic stem cells (HSCs) reside primarily in bone marrow. However, hematopoietic stresses such as myelofibrosis, anemia, pregnancy, infection or myeloablation can mobilize HSCs to the spleen and induce extramedullary hematopoiesis (EMH). While the bone marrow HSC niche has been studied intensively, the EMH niche has received little attention. Here, we systematically assessed the physiological sources of the key niche factors, SCF and CXCL12, in the mouse spleen after EMH induction by cyclophosphamide plus granulocyte colony-stimulating factor, blood loss, or pregnancy. In each case, Scf was expressed by endothelial cells and Tcf21+ stromal cells, primarily around sinusoids in red pulp, while Cxcl12 was expressed by a subset of Tcf21+ stromal cells. EMH induction markedly expanded the Scf-expressing endothelial cells and stromal cells by inducing proliferation. Most splenic HSCs were adjacent to Tcf21+ stromal cells in red pulp. Conditional deletion of Scf from spleen endothelial cells or Scf or Cxcl12 from Tcf21+ stromal cells severely reduced spleen EMH and reduced blood cell counts without affecting bone marrow hematopoiesis. Endothelial cells and Tcf21+ stromal cells thus create the splenic EMH niche, which is necessary for the physiological response to diverse hematopoietic stresses.
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Project description:Hematopoietic stem cells (HSCs) primarily reside in the bone marrow where signals generated by stromal cells regulate their self-renewal, proliferation, and trafficking. Endosteal osteoblasts and perivascular stromal cells including endothelial cells3, CXCL12-abundant reticular (CAR) cells, leptin-receptor positive stromal cells, and nestin-GFP positive mesenchymal progenitors have all been implicated in HSC maintenance. However, it is unclear if specific hematopoietic progenitor cell (HPC) subsets reside in distinct niches defined by the surrounding stromal cells and the regulatory molecules they produce. CXCL12 (stromal-derived factor-1, SDF-1) regulates both HSCs and lymphoid progenitors and is expressed by all of these stromal cell populations. Here, we selectively deleted Cxcl12 from candidate niche stromal cell populations and characterized the effect on HPCs. Deletion of Cxcl12 from mineralizing osteoblasts has no effect on HSCs or lymphoid progenitors. Deletion of Cxcl12 from osterix-expressing stromal cells, which includes CAR cells and osteoblasts, results in constitutive HPC mobilization and a loss of B lymphoid progenitors, but HSC function is normal. Cxcl12 deletion in endothelial cells results in a modest loss of long-term repopulating activity. Strikingly, deletion of Cxcl12 in nestin-negative mesenchymal progenitors using Prx1-Cre is associated with a marked loss of HSCs, long-term repopulating activity, HSC quiescence, and common lymphoid progenitors. These data suggest that osterix-expressing stromal cells comprise a distinct niche that supports B lymphoid progenitors and retains HPC in the bone marrow, while expression of CXCL12 from stromal cells in the perivascular region, including endothelial cells and mesenchymal progenitors, support HSCs. Total of three samples of two groups analyzed. Replica samples of CXCL12-abundant reticular (CAR) cells from two CXCL12-GFP knock-in mice and a combined sample of PDGFRa+ Sca+ CD45- lineage- cells from three Prx1-Cre Rosa26Ai9/+ Cxcl12gfp/+ mice were used and analyzed.
2013-01-31 | E-GEOD-43613 | biostudies-arrayexpress
Project description:Eltrombopag, a small molecule thrombopoietin receptor (TPO-R) agonist and potent intracellular iron chelator, has shown remarkable efficacy to stimulate sustained multilineage hematopoiesis in patients with bone marrow failure syndromes, suggesting an effect at the most immature hematopoietic stem and multipotent progenitor level. While the functional and molecular effects of Eltrombopag on megakaryopoiesis have been carefully studied in the recent past, insights into its mechanistic impact on the earliest stages of hematopoiesis have been limited. Additionally, previous studies also revealed molecular pathway of Eltrombopag apart from stimulation of TPO signaling, detail characterization remains to be addressed. In this study, we investigated the effects of Eltrombopag, in comparison with TPO, on highly-purified primary hematopoietic stem cells (HSCs) from healthy human donors. The binding of Eltrombopag to TPO-R is species-specific to human and primate cells. we also utilized HSCs isolated mouse as separation-of-function models to directly assess the molecular effect of Eltrombopag on HSCs independent of TPOR stimulation.
2018-09-17 | GSE107428 | GEO
Project description:Eltrombopag, a small molecule thrombopoietin receptor (TPO-R) agonist and potent intracellular iron chelator, has shown remarkable efficacy to stimulate sustained multilineage hematopoiesis in patients with bone marrow failure syndromes, suggesting an effect at the most immature hematopoietic stem and multipotent progenitor level. While the functional and molecular effects of Eltrombopag on megakaryopoiesis have been carefully studied in the recent past, insights into its mechanistic impact on the earliest stages of hematopoiesis have been limited. Additionally, previous studies also revealed molecular pathway of Eltrombopag apart from stimulation of TPO signaling, detail characterization remains to be addressed. In this study, we investigated the effects of Eltrombopag, in comparison with TPO, on highly-purified primary hematopoietic stem cells (HSCs) from healthy human donors. The binding of Eltrombopag to TPO-R is species-specific to human and primate cells. we also utilized HSCs isolated mouse as separation-of-function models to directly assess the molecular effect of Eltrombopag on HSCs independent of TPOR stimulation.
2018-09-17 | GSE107429 | GEO
Project description:Thrombopoietin (TPO) acting via its receptor Mpl is the major cytokine regulator of platelet number. To precisely define the role of specific hematopoietic cells in TPO dependent hematopoiesis, we generated mice that express the Mpl receptor normally on stem/progenitor cells but lack expression on megakaryocytes and platelets (MplPF4cre/PF4cre). MplPF4cre/PF4cre mice displayed profound megakaryocytosis and thrombocytosis with a remarkable expansion of megakaryocyte-committed and multipotential progenitor cells, the latter displaying biological responses and a gene expression signature indicative of chronic TPO over-stimulation as the underlying causative mechanism, despite a normal circulating TPO level. Thus, TPO signaling in megakaryocytes is dispensable for platelet production; its key role in control of platelet number is via generation and stimulation of the bipotential megakaryocyte precursors. Nevertheless, Mpl expression on megakaryocytes and platelets is essential to prevent megakaryocytosis and myeloproliferation by restricting the amount of TPO available to stimulate the production of megakaryocytes from the progenitor cell pool.
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Project description:Dnm2fl/fl Pf4-Cre (Dnm2Plt-/-) mice lacking the endocytic GTPase dynamin 2 (DNM2) in platelets and megakaryocytes (MKs) develop hallmarks of myelofibrosis. At the cellular level, the tyrosine kinase JAK2 is constitutively active but decreased in expression in Dnm2Plt-/- platelets. Additionally, Dnm2Plt-/- platelets cannot endocytose the thrombopoietin (TPO) receptor Mpl, leading to elevated circulating TPO levels. Here, we assessed whether the hyperproliferative phenotype of Dnm2Plt-/- mice was due to JAK2 constitutive activation or elevated circulating TPO levels. In unstimulated Dnm2Plt-/- platelets, STAT3 and to a lower extent STAT5 were phosphorylated, but their phosphorylation was slowed and diminished upon TPO stimulation. We further crossed Dnm2Plt-/- mice in the Mpl-/- background to generate Mpl-/- Dnm2Plt-/- mice lacking Mpl ubiquitously and DNM2 in platelets and MKs. Mpl-/- Dnm2Plt-/- platelets had severely reduced JAK2 and STAT3 but normal STAT5 expression. Mpl-/- Dnm2Plt-/- mice had severely reduced bone marrow MK and hematopoietic stem and progenitor cell numbers. Additionally, Mpl-/- Dnm2Plt-/- mice had severe erythroblast maturation defects, decreased expression of hemoglobin and heme homeostasis genes, increased expression of ribosome biogenesis and protein translation genes, and developed anemia with grossly elevated plasma erythropoietin levels, leading to early fatality by postnatal day 25. Mpl-/- Dnm2Plt+/+ mice had impaired EB development at three weeks of age, which normalized with adulthood. Together, the data shows that DNM2-dependent Mpl-mediated endocytosis in platelets and MKs is required for steady-state hematopoiesis and provides novel insights into a developmentally controlled role for Mpl in normal erythropoiesis, regulating hemoglobin and heme production.
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Project description:Hematopoietic stem cell transplantation (HSCT) is successfully applied since the late 1950s, however, its efficacy still needs to be improved. A promising strategy is to transplant high numbers of pluripotent hematopoietic stem cells (HSCs). Therefore, an advanced ex vivo culture system is needed that supports the proliferation and maintains the pluripotency of HSC to override possible limitations in cell numbers gained from donors. To model the natural HSC niche in vitro and thus, to amplify high numbers of undifferentiated HSCs, we used an optimized HSC cell culture medium in combination with artificial 3D bone marrow-like scaffolds made of polydimethylsiloxane (PDMS). After 14 days in vitro (DIV) cell culture, we performed transcriptome and proteome analysis of the whole cell populations. Ingenuity pathway analysis (IPA) indicated that our 3D PDMS cell culture scaffolds activated interleukin, SREBP, mTOR and FOXO signaling pathways as well as the HSC metabolism, which we confirmed by ELISA, Western blot and metabolic flux analysis. These molecular signaling pathways and HSC metabolism are well known to promote the expansion HSCs and are involved in their pluripotency maintenance. After selection and enrichment of immature CD34-positive/CD38-negative HSCs using FACS sorting, we could confirm our findings by another proteome analysis followed by IPA. Thus, we could show that our 3D bone marrow-like PDMS scaffolds activate key molecular signaling pathways to amplify the numbers of undifferentiated HSC efficiently ex vivo.
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