Abstract
Vascular endothelial growth factor (VEGF) and stem cell factor (SCF) act as growth factors for the hemangioblast, an embryonic progenitor of the hematopoietic and endothelial lineages. Because thrombopoietin (TPO) and its receptor, c-Mpl, regulate primitive hematopoietic populations, including bone marrow hematopoietic stem cells, we investigated whether TPO acts on the hemangioblasts that derive from differentiation of embryonic stem cells in vitro. Reverse transcriptase polymerase chain reaction analysis detected expression of c-Mpl beginning on day 3 of embryoid body differentiation when the hemangioblast first arises. In assays of the hemangioblast colony-forming cell (BL-CFC), TPO alone supported BL-CFC formation and nearly doubled the number of BL-CFC when added together with VEGF and SCF. When replated under the appropriate conditions, TPO-stimulated BL-CFC gave rise to secondary hematopoietic colonies, as well as endothelial cells, confirming their nature as hemangioblasts. Addition of a neutralizing anti-VEGF antibody did not block TPO enhancement of BL-CFC formation, suggesting that TPO acts independently of VEGF. These results establish that Mpl signaling plays a role in the earliest stages of hematopoietic development and that TPO represents a third growth factor influencing hemangioblast formation.
Publication types
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Research Support, Non-U.S. Gov't
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Research Support, U.S. Gov't, Non-P.H.S.
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Research Support, U.S. Gov't, P.H.S.
MeSH terms
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Animals
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Antibodies / pharmacology
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Blood Cells / cytology
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Blood Cells / drug effects
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Blood Cells / metabolism
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Cardiovascular System / cytology
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Cardiovascular System / embryology*
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Cardiovascular System / metabolism
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Cell Differentiation / drug effects
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Cell Differentiation / physiology*
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Cells, Cultured
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Female
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Hematopoiesis / drug effects
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Hematopoiesis / physiology
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Hematopoietic Stem Cells / cytology
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Hematopoietic Stem Cells / drug effects
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Hematopoietic Stem Cells / metabolism*
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Male
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Mice
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Neoplasm Proteins / genetics*
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Proto-Oncogene Proteins / genetics*
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RNA, Messenger / drug effects
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RNA, Messenger / metabolism
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Receptors, Cytokine / genetics*
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Receptors, Thrombopoietin
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Signal Transduction / drug effects
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Signal Transduction / physiology
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Stem Cell Factor / metabolism
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Stem Cell Factor / pharmacology
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Thrombopoietin / metabolism*
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Thrombopoietin / pharmacology
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Vascular Endothelial Growth Factor A / antagonists & inhibitors
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Vascular Endothelial Growth Factor A / metabolism
Substances
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Antibodies
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Neoplasm Proteins
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Proto-Oncogene Proteins
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RNA, Messenger
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Receptors, Cytokine
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Receptors, Thrombopoietin
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Stem Cell Factor
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Vascular Endothelial Growth Factor A
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MPL protein, human
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Thrombopoietin