- Email: [email protected]
2003 - ACUTE MYELOID LEUKEMIA CELLS SEIZE SEROTONIN SIGNALING IN OSTEOBLASTS TO ENGRAFT AND PROLIFERATE
Short Talk Presentations / Experimental Hematology 2019;76 (Suppl): S42−S50 the absence of Hsf1. At the molecular level, Hsf1 activation reduced the unfolded protein load and partially rebalanced protein homeostasis in HSCs. These findings indicate that maintaining protein homeostasis is a key factor in promoting ex vivo HSC self-renewal.
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2004 - NOVEL PRO-INFLAMMATORY AGM-ASSOCIATED MACROPHAGES ARE INVOLVED IN EMBRYONIC DEVELOPMENT OF HEMATOPOIETIC STEM CELLS Samanta Mariani1, Zhuan Li2, Siobhan Rice3, Stamatina Fragkogianni4, Carsten Krieg5, Chris Vink1, Jeffrey Pollard1, Elaine Dzierzak1 1 The University of Edinburgh, Edinburgh, United Kingdom; 2 Guangzhou University, Guangzhou, China (People’s Republic); 3 The Queen’s College, Oxford, Oxford, United Kingdom; 4 Memorial Sloan Kettering Cancer Center, New York, United States; 5Medical University of South Carolina, Charleston, United States Hematopoietic stem cells (HSCs) are responsible for the life-long maintenance and regeneration of the adult vertebrate blood system. The first HSCs are generated from specialized endothelial cells of the embryonic aorta. Inflammatory factors have been implicated in regulating HSC development, but it is unclear what cells in the mouse embryonic aorta-gonad-mesonephros (AGM) microenvironment produce these factors. In the adult, macrophages play both pro- and anti-inflammatory roles and they are involved in bone marrow hematopoiesis. We sought to examine whether macrophages or other hematopoietic cells found in the embryo prior to HSC generation are involved in the AGM HSC-generative microenvironment. Our mass cytometry (CyTOF) results indicate the absence of lymphoid cells and mature neutrophils in E10.5 mouse AGM, while two abundant myeloid cell types are present − mannose-receptor positive AGM-associated macrophages (AGM-aM) and mannose-receptor negative macrophages/progenitors. We show that the appearance of macrophages in the AGM is dependent on CX3CR1 and it occurs just before the time of HSC generation. Differently from mannose-receptor positive adult macrophages, AGM-aM express a pro-inflammatory signature. They localize to the embryonic aorta and dynamically interact with nascent and emerging intra-aortic hematopoietic cells (IAHC). Importantly, upon macrophage depletion, no adult-repopulating HSCs are detected, thus implicating unique pro-inflammatory AGM-associated macrophages in regulating the embryonic development of HSCs.
2003 - ACUTE MYELOID LEUKEMIA CELLS SEIZE SEROTONIN SIGNALING IN OSTEOBLASTS TO ENGRAFT AND PROLIFERATE Marta Galan-Diez1,2, Junfei Zhao3, Raul Rabadan3, Stavroula Kousteni4 1 Columbia University, Department of Physiology and Cellular Biophysics, New York, United States; 2 College of Physicians and Surgeons, New York, United States; 3Columbia University, New York, United States; 4Columbia University, New York, United States Patients with myelodysplasia or acute myeloid leukemia (AML) show decreased osteoblast numbers, and this is reproduced in mouse models of acute leukemia. Manipulating the osteoblast pool directly affects leukemia progression: osteoblast ablation increases leukemia burden, while maintenance of osteoblast numbers decreases it and prolongs survival. Here we show that the protective effect of osteoblasts against leukemia does not rely on a certain threshold of osteoblast numbers but rather requires a specific signaling pathway. Treatment of leukemic mice with parathyroid hormone, which increases osteoblast numbers, had no effect in leukemia progression. In contrast, maintaining the osteoblast pool in leukemic mice by decreasing the synthesis of gut-derived serotonin, reduced AML burden and prolonged survival. Using the human-AML MLL-AF9 model, we examined whether deletion of one of the main serotonin receptors expressed in osteoblasts affects leukemia progression. Global deletion of Htr1b in mice prevented leukemia. While removal of Htr1b in LepR+ positive mesenchymal stem cells had no effect in leukemia progression, its deletion in Col1a1-expressing osteoblast precursors significantly prevented lethality in the mutant mice. In order to dissect the crosstalk between leukemia-cells and osteoblasts, we co-cultured primary-human osteoblasts and AML cells. RNAseq analysis identified a signature of chemoattractants and pro-inflammatory cytokines secreted by osteoblasts upon exposure to AML cells, suggesting that the protective mechanism exerted by osteoblasts activates the anti-tumor immune response against leukemia. In summary, our data suggest that AML cells activate serotonin signaling in osteoblasts to promote their engraftment and expansion. Targeting this pathway may render the niche hostile to leukemia by enhancing the anti-tumor immune response elicited by osteoblasts.
2005 - GATA3 PROMOTES THE ENDOTHELIAL-TO-HEMATOPOIETIC TRANSITION VIA REGULATION OF THE CELL CYCLE Katrin Ottersbach1, Nada Zaidan2 , Evangelia Diamanti3, Emma Shaw1, Nicola Wilson3, Berthold Gottgens3 1 University of Edinburgh, Edinburgh, United Kingdom; 2King Abdullah International Medical Research Centre, Riyadh, Saudi Arabia; 3University of Cambridge, Cambridge, United Kingdom Hematopoietic stem cells (HSCs) are known to emerge in the dorsal aorta at E10.5 of mouse embryo development. They derive from hemogenic endothelial cells via a process known as endothelial-to-hematopoietic transition (EHT), which comprises a number of intermediate steps and the molecular details of which have not been fully characterized. Our lab has previously demonstrated that embryos deficient for the transcription factor Gata3 have a defect in HSC generation in the dorsal aorta. This was linked to a lack of catecholamine synthesis in these embryos, which demonstrated that neurotransmitters released from the co-developing sympathetic nervous system promote embryonic HSC production. We now have evidence that Gata3 plays an additional role in EHT. Gata3 expression was found to enrich for hemogenic endothelial cell activity, and an endothelial-specific knockout of Gata3 severely impairs HSC generation in the dorsal aorta. Furthermore, with the use of co-aggregation assays developed in the Medvinsky lab, we were able to determine that Gata3 is expressed in the pro-HSC and pre-HSC type I stage, but is downregulated thereafter. RNA-Seq analysis of Gata3-positive and negative cell populations highlighted a cell cycle signature, with cell cycle inhibitors, such as p57Kip2, specifically enriched in Gata3-expressing cells. This suggests that a cell cycle arrest may be required for endothelial cells to complete the transition to a hematopoietic fate, which is supported by our preliminary results with embryos deficient for p57Kip2. Our results thus provide further insights into the molecular mechanisms of HSC generation from endothelial cells.
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2004 - NOVEL PRO-INFLAMMATORY AGM-ASSOCIATED MACROPHAGES ARE INVOLVED IN EMBRYONIC DEVELOPMENT OF HEMATOPOIETIC STEM CELLS Samanta Mariani1, Zhuan Li2, Siobhan Rice3, Stamatina Fragkogianni4, Carsten Krieg5, Chris Vink1, Jeffrey Pollard1, Elaine Dzierzak1 1 The University of Edinburgh, Edinburgh, United Kingdom; 2 Guangzhou University, Guangzhou, China (People’s Republic); 3 The Queen’s College, Oxford, Oxford, United Kingdom; 4 Memorial Sloan Kettering Cancer Center, New York, United States; 5Medical University of South Carolina, Charleston, United States Hematopoietic stem cells (HSCs) are responsible for the life-long maintenance and regeneration of the adult vertebrate blood system. The first HSCs are generated from specialized endothelial cells of the embryonic aorta. Inflammatory factors have been implicated in regulating HSC development, but it is unclear what cells in the mouse embryonic aorta-gonad-mesonephros (AGM) microenvironment produce these factors. In the adult, macrophages play both pro- and anti-inflammatory roles and they are involved in bone marrow hematopoiesis. We sought to examine whether macrophages or other hematopoietic cells found in the embryo prior to HSC generation are involved in the AGM HSC-generative microenvironment. Our mass cytometry (CyTOF) results indicate the absence of lymphoid cells and mature neutrophils in E10.5 mouse AGM, while two abundant myeloid cell types are present − mannose-receptor positive AGM-associated macrophages (AGM-aM) and mannose-receptor negative macrophages/progenitors. We show that the appearance of macrophages in the AGM is dependent on CX3CR1 and it occurs just before the time of HSC generation. Differently from mannose-receptor positive adult macrophages, AGM-aM express a pro-inflammatory signature. They localize to the embryonic aorta and dynamically interact with nascent and emerging intra-aortic hematopoietic cells (IAHC). Importantly, upon macrophage depletion, no adult-repopulating HSCs are detected, thus implicating unique pro-inflammatory AGM-associated macrophages in regulating the embryonic development of HSCs.
2003 - ACUTE MYELOID LEUKEMIA CELLS SEIZE SEROTONIN SIGNALING IN OSTEOBLASTS TO ENGRAFT AND PROLIFERATE Marta Galan-Diez1,2, Junfei Zhao3, Raul Rabadan3, Stavroula Kousteni4 1 Columbia University, Department of Physiology and Cellular Biophysics, New York, United States; 2 College of Physicians and Surgeons, New York, United States; 3Columbia University, New York, United States; 4Columbia University, New York, United States Patients with myelodysplasia or acute myeloid leukemia (AML) show decreased osteoblast numbers, and this is reproduced in mouse models of acute leukemia. Manipulating the osteoblast pool directly affects leukemia progression: osteoblast ablation increases leukemia burden, while maintenance of osteoblast numbers decreases it and prolongs survival. Here we show that the protective effect of osteoblasts against leukemia does not rely on a certain threshold of osteoblast numbers but rather requires a specific signaling pathway. Treatment of leukemic mice with parathyroid hormone, which increases osteoblast numbers, had no effect in leukemia progression. In contrast, maintaining the osteoblast pool in leukemic mice by decreasing the synthesis of gut-derived serotonin, reduced AML burden and prolonged survival. Using the human-AML MLL-AF9 model, we examined whether deletion of one of the main serotonin receptors expressed in osteoblasts affects leukemia progression. Global deletion of Htr1b in mice prevented leukemia. While removal of Htr1b in LepR+ positive mesenchymal stem cells had no effect in leukemia progression, its deletion in Col1a1-expressing osteoblast precursors significantly prevented lethality in the mutant mice. In order to dissect the crosstalk between leukemia-cells and osteoblasts, we co-cultured primary-human osteoblasts and AML cells. RNAseq analysis identified a signature of chemoattractants and pro-inflammatory cytokines secreted by osteoblasts upon exposure to AML cells, suggesting that the protective mechanism exerted by osteoblasts activates the anti-tumor immune response against leukemia. In summary, our data suggest that AML cells activate serotonin signaling in osteoblasts to promote their engraftment and expansion. Targeting this pathway may render the niche hostile to leukemia by enhancing the anti-tumor immune response elicited by osteoblasts.
2005 - GATA3 PROMOTES THE ENDOTHELIAL-TO-HEMATOPOIETIC TRANSITION VIA REGULATION OF THE CELL CYCLE Katrin Ottersbach1, Nada Zaidan2 , Evangelia Diamanti3, Emma Shaw1, Nicola Wilson3, Berthold Gottgens3 1 University of Edinburgh, Edinburgh, United Kingdom; 2King Abdullah International Medical Research Centre, Riyadh, Saudi Arabia; 3University of Cambridge, Cambridge, United Kingdom Hematopoietic stem cells (HSCs) are known to emerge in the dorsal aorta at E10.5 of mouse embryo development. They derive from hemogenic endothelial cells via a process known as endothelial-to-hematopoietic transition (EHT), which comprises a number of intermediate steps and the molecular details of which have not been fully characterized. Our lab has previously demonstrated that embryos deficient for the transcription factor Gata3 have a defect in HSC generation in the dorsal aorta. This was linked to a lack of catecholamine synthesis in these embryos, which demonstrated that neurotransmitters released from the co-developing sympathetic nervous system promote embryonic HSC production. We now have evidence that Gata3 plays an additional role in EHT. Gata3 expression was found to enrich for hemogenic endothelial cell activity, and an endothelial-specific knockout of Gata3 severely impairs HSC generation in the dorsal aorta. Furthermore, with the use of co-aggregation assays developed in the Medvinsky lab, we were able to determine that Gata3 is expressed in the pro-HSC and pre-HSC type I stage, but is downregulated thereafter. RNA-Seq analysis of Gata3-positive and negative cell populations highlighted a cell cycle signature, with cell cycle inhibitors, such as p57Kip2, specifically enriched in Gata3-expressing cells. This suggests that a cell cycle arrest may be required for endothelial cells to complete the transition to a hematopoietic fate, which is supported by our preliminary results with embryos deficient for p57Kip2. Our results thus provide further insights into the molecular mechanisms of HSC generation from endothelial cells.