title: Uncertainty in the niches that maintain haematopoietic stem cells.
abstract: Haematopoietic stem cell (HSC) niches are specialized microenvironments that contain stem cells and regulate their maintenance. Cells at the interface of bone and the bone marrow (the endosteum) contribute to the creation of HSC niches. It remains uncertain whether this interface itself is a niche, or whether endosteal cells secrete factors that diffuse to nearby niches. Vascular and/or perivascular cells may also create niches as many HSCs are observed around sinusoidal blood vessels, and perivascular cells secrete factors that regulate HSC maintenance. Do endosteal and perivascular cells create distinct niches, or do they contribute to a common niche? We discuss a range of niche models consistent with recent evidence.
authors.affiliation: Howard Hughes Medical Institute, Life Sciences Institute, Department of Internal Medicine, and Center for Stem Cell Biology, University of Michigan, Ann Arbor, Michigan, 48109-2216, USA.
authors.forename: Mark J
authors.initials: MJ
authors.lastname: Kiel
authors.forename: Sean J
authors.initials: SJ
authors.lastname: Morrison
mesh_terms: D000818:Animals; D001808:Blood Vessels / Q000166:cytology; D001853:Bone Marrow / Q000033:anatomy & histology; D001854:Bone Marrow Cells / Q000166:cytology*; D001842:Bone and Bones / Q000166:cytology; D002454:Cell Differentiation / Q000502:physiology; D006410:Hematopoiesis; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D006801:Humans; D010006:Osteoblasts / Q000166:cytology; D010010:Osteoclasts / Q000166:cytology; D013154:Spleen / Q000166:cytology