Endothelium and NOTCH specify and amplify aorta-gonad-mesonephros-derived hematopoietic stem cells

J Clin Invest. 2015 May;125(5):2032-45. doi: 10.1172/JCI80137. Epub 2015 Apr 13.


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.

Publication types

  • Research Support, N.I.H., Extramural
  • Research Support, Non-U.S. Gov't

MeSH terms

  • Animals
  • Antigens, CD / analysis
  • Aorta / embryology*
  • Cadherins / analysis
  • Cells, Cultured
  • Colony-Forming Units Assay
  • Endothelial Cells / physiology*
  • Endothelium, Vascular / cytology
  • Endothelium, Vascular / embryology*
  • Female
  • Gonads / embryology*
  • Graft Survival
  • Hematopoietic Stem Cell Transplantation
  • Hematopoietic System / embryology*
  • Intracellular Signaling Peptides and Proteins / physiology
  • Leukocyte Common Antigens / analysis
  • Male
  • Membrane Proteins / physiology
  • Mesonephros / embryology*
  • Mice, Congenic
  • Mice, Inbred C57BL
  • Radiation Chimera
  • Receptor, Notch1 / physiology*
  • Receptor, Notch2 / physiology*
  • Signal Transduction
  • Stem Cell Niche / physiology*
  • Stromal Cells / physiology


  • Antigens, CD
  • Cadherins
  • Intracellular Signaling Peptides and Proteins
  • Membrane Proteins
  • Notch1 protein, mouse
  • Notch2 protein, mouse
  • Receptor, Notch1
  • Receptor, Notch2
  • cadherin 5
  • delta protein
  • Leukocyte Common Antigens
  • Ptprc protein, mouse