title: Tie2/angiopoietin-1 signaling regulates hematopoietic stem cell quiescence in the bone marrow niche.
abstract: The quiescent state is thought to be an indispensable property for the maintenance of hematopoietic stem cells (HSCs). Interaction of HSCs with their particular microenvironments, known as the stem cell niches, is critical for adult hematopoiesis in the bone marrow (BM). Here, we demonstrate that HSCs expressing the receptor tyrosine kinase Tie2 are quiescent and antiapoptotic, and comprise a side-population (SP) of HSCs, which adhere to osteoblasts (OBs) in the BM niche. The interaction of Tie2 with its ligand Angiopoietin-1 (Ang-1) induced cobblestone formation of HSCs in vitro and maintained in vivo long-term repopulating activity of HSCs. Furthermore, Ang-1 enhanced the ability of HSCs to become quiescent and induced adhesion to bone, resulting in protection of the HSC compartment from myelosuppressive stress. These data suggest that the Tie2/Ang-1 signaling pathway plays a critical role in the maintenance of HSCs in a quiescent state in the BM niche.
authors.affiliation: Department of Cell Differentiation, The Sakaguchi Laboratory of Developmental Biology, School of Medicine, Keio University, 35 Shinano-machi, Shinjuku-ku, Tokyo, 160-8582, Japan.
authors.forename: Fumio
authors.initials: F
authors.lastname: Arai
authors.forename: Atsushi
authors.initials: A
authors.lastname: Hirao
authors.forename: Masako
authors.initials: M
authors.lastname: Ohmura
authors.forename: Hidetaka
authors.initials: H
authors.lastname: Sato
authors.forename: Sahoko
authors.initials: S
authors.lastname: Matsuoka
authors.forename: Keiyo
authors.initials: K
authors.lastname: Takubo
authors.forename: Keisuke
authors.initials: K
authors.lastname: Ito
authors.forename: Gou Young
authors.initials: GY
authors.lastname: Koh
authors.forename: Toshio
authors.initials: T
authors.lastname: Suda
mesh_terms: D042683:Angiopoietin-1 / Q000378:metabolism*; D000818:Animals; D001854:Bone Marrow Cells / Q000378:metabolism; D002448:Cell Adhesion / Q000502:physiology; D002454:Cell Differentiation / Q000502:physiology*; D002455:Cell Division / Q000502:physiology; D002460:Cell Line; D006410:Hematopoiesis / Q000502:physiology*; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism*; D007108:Immune Tolerance / Q000502:physiology; D008024:Ligands; D051379:Mice; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000378:metabolism; D042787:Receptor, TIE-2 / Q000378:metabolism*; D015398:Signal Transduction / Q000502:physiology*; D013312:Stress, Physiological / Q000378:metabolism
chemical_list: D042683:Angiopoietin-1; D008024:Ligands; D042787:Receptor, TIE-2