title: Endothelium and NOTCH specify and amplify aorta-gonad-mesonephros-derived hematopoietic stem cells.
abstract: Hematopoietic stem cells (HSCs) first emerge during embryonic development within vessels such as the dorsal aorta of the aorta-gonad-mesonephros (AGM) region, suggesting that signals from the vascular microenvironment are critical for HSC development. Here, we demonstrated that AGM-derived endothelial cells (ECs) engineered to constitutively express AKT (AGM AKT-ECs) can provide an in vitro niche that recapitulates embryonic HSC specification and amplification. Specifically, nonengrafting embryonic precursors, including the VE-cadherin-expressing population that lacks hematopoietic surface markers, cocultured with AGM AKT-ECs specified into long-term, adult-engrafting HSCs, establishing that a vascular niche is sufficient to induce the endothelial-to-HSC transition in vitro. Subsequent to hematopoietic induction, coculture with AGM AKT-ECs also substantially increased the numbers of HSCs derived from VE-cadherin⁺CD45⁺ AGM hematopoietic cells, consistent with a role in supporting further HSC maturation and self-renewal. We also identified conditions that included NOTCH activation with an immobilized NOTCH ligand that were sufficient to amplify AGM-derived HSCs following their specification in the absence of AGM AKT-ECs. Together, these studies begin to define the critical niche components and resident signals required for HSC induction and self-renewal ex vivo, and thus provide insight for development of defined in vitro systems targeted toward HSC generation for therapeutic applications.
authors: Brandon K
authors: BK
authors: Hadland
authors: Barbara
authors: B
authors: Varnum-Finney
authors: Michael G
authors: MG
authors: Poulos
authors: Randall T
authors: RT
authors: Moon
authors: Jason M
authors: JM
authors: Butler
authors: Shahin
authors: S
authors: Rafii
authors: Irwin D
authors: ID
authors: Bernstein
mesh_terms: D000818:Animals; D015703:Antigens, CD / Q000032:analysis; D001011:Aorta / Q000196:embryology*; D015820:Cadherins / Q000032:analysis; D002478:Cells, Cultured; D003114:Colony-Forming Units Assay; D042783:Endothelial Cells / Q000502:physiology*; D004730:Endothelium, Vascular / Q000166:cytology / Q000196:embryology*; D005260:Female; D006066:Gonads / Q000196:embryology*; D006085:Graft Survival; D018380:Hematopoietic Stem Cell Transplantation; D006413:Hematopoietic System / Q000196:embryology*; D047908:Intracellular Signaling Peptides and Proteins / Q000502:physiology; D017493:Leukocyte Common Antigens / Q000032:analysis; D008297:Male; D008565:Membrane Proteins / Q000502:physiology; D008650:Mesonephros / Q000196:embryology*; D020297:Mice, Congenic; D008810:Mice, Inbred C57BL; D011828:Radiation Chimera; D051881:Receptor, Notch1 / Q000502:physiology*; D051883:Receptor, Notch2 / Q000502:physiology*; D015398:Signal Transduction; D055153:Stem Cell Niche / Q000502:physiology*; D017154:Stromal Cells / Q000502:physiology; D000099152:Cadherin 5
chemical_list: D015703:Antigens, CD; D015820:Cadherins; D047908:Intracellular Signaling Peptides and Proteins; D017493:Leukocyte Common Antigens; D008565:Membrane Proteins; D051881:Receptor, Notch1; D051883:Receptor, Notch2; D000099152:Cadherin 5; C497762:Notch1 protein, mouse; C497765:Notch2 protein, mouse; C064045:delta protein; C516770:Ptprc protein, mouse