Authors:
Jason M. Butler, Daniel J. Nolan, Eva L. Vertes, Barbara Varnum-Finney, Hideki Kobayashi, Andrea T. Hooper, Marco Seandel, Koji Shido, Ian A. White, Mariko Kobayashi, Larry Witte, Chad May, Carrie Shawber, Yuki Kimura, Jan Kitajewski, Zev Rosenwaks, & Irwin D. Bernstein, Shahin Rafii
Summary:
Bone marrow endothelial cells (ECs) are essential for reconstitution of hematopoiesis, but their role in self-renewal of long-term hematopoietic stem cells (LT-HSCs) is unknown. We have developed angiogenic models to demonstrate that EC-derived angiocrine growth factors support in vitro self-renewal and in vivo repopulation of authentic LT-HSCs. In serum/cytokine-free cocultures, ECs, through direct cellular contact, stimulated incremental expansion of repopulating CD34-Flt3-cKit+Lineage-Sca1+ LT-HSCs, which retained their self-renewal ability, as determined by single-cell and serial transplantation assays. Angiocrine expression of Notch ligands by ECs promoted proliferation and prevented exhaustion of LT-HSCs derived from wild-type, but not Notch1/Notch2-deficient, mice. In transgenic notch-reporter (TNR.Gfp) mice, regenerating TNR.Gfp+ LT-HSCs were detected in cellular contact with sinusoidal ECs. Interference with angiocrine, but not perfusion, function of SECs impaired repopulation of TNR.Gfp+ LT-HSCs. ECs establish an instructive vascular niche for clinical-scale expansion of LT-HSCs and a cellular platform to identify stem cell-active trophogens.
Source:
Cell Stem Cell; Vol. 6, Issue 3, 251-264 (03/05/10)