title: Lack of evidence that hematopoietic stem cells depend on N-cadherin-mediated adhesion to osteoblasts for their maintenance.
abstract: Recent studies have proposed that bone marrow hematopoietic stem cells (HSCs) are maintained via N-cadherin-mediated homophilic adhesion with osteoblasts. However, there is not yet any evidence that N-cadherin-expressing cells have HSC activity or that osteoblasts are required for HSC maintenance. We were unable to detect N-cadherin expression in highly purified HSCs by polymerase chain reaction, by using commercial anti-N-cadherin antibodies, or by beta-galactosidase staining of N-cadherin gene trap mice. Only N-cadherin-negative bone marrow cells exhibited HSC activity in irradiated mice. Finally, biglycan-deficient mice had significant reductions in trabecular bone and osteoblasts but showed no defects in hematopoiesis, HSC frequency, or function. Thus, reductions in osteoblasts do not necessarily lead to reductions in HSCs. Most bone marrow HSCs in wild-type and biglycan-deficient mice localized to sinusoids, and few localized within five cell diameters of the endosteum. These results question whether significant numbers of HSCs depend on N-cadherin-mediated adhesion to osteoblasts.
authors: Howard Hughes Medical Institute, University of Michigan, Ann Arbor, MI 48109-2216, USA.
authors: Mark J
authors: MJ
authors: Kiel
authors: Glenn L
authors: GL
authors: Radice
authors: Sean J
authors: SJ
authors: Morrison
mesh_terms: D000818:Animals; D058578:Biglycan; D001854:Bone Marrow Cells / Q000502:physiology; D015820:Cadherins / Q000096:biosynthesis / Q000235:genetics / Q000502:physiology*; D002448:Cell Adhesion / Q000502:physiology; D002450:Cell Communication / Q000502:physiology; D016326:Extracellular Matrix Proteins / Q000502:physiology; D006412:Hematopoietic Stem Cells / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D051379:Mice; D008810:Mice, Inbred C57BL; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D011509:Proteoglycans / Q000502:physiology
chemical_list: C546885:Bgn protein, mouse; D058578:Biglycan; D015820:Cadherins; C489083:Cdh2 protein, mouse; D016326:Extracellular Matrix Proteins; D011509:Proteoglycans