title: Contribution of alpha6 integrins to hematopoietic stem and progenitor cell homing to bone marrow and collaboration with alpha4 integrins.
abstract: The laminin receptor integrin alpha6 chain is ubiquitously expressed in human and mouse hematopoietic stem and progenitor cells. We have studied its role for homing of stem and progenitor cells to mouse hematopoietic tissues in vivo. A function-blocking anti-integrin alpha6 antibody significantly reduced progenitor cell homing to bone marrow (BM) of lethally irradiated mice, with a corresponding retention of progenitors in blood. Remarkably, the anti-integrin alpha6 antibody profoundly inhibited BM homing of long-term multilineage engrafting stem cells, studied by competitive repopulation assay and analysis of donor-derived lymphocytes and myeloid cells in blood 16 weeks after transplantation. A similar profound inhibition of long-term stem cell homing was obtained by using a function-blocking antibody against alpha4 integrin, studied in parallel. Furthermore, the anti-integrin alpha6 and alpha4 antibodies synergistically inhibited homing of short-term repopulating stem cells. Intravenous injection of anti-integrin alpha6 antibodies, in contrast to antibodies against alpha4 integrin, did not mobilize progenitors or enhance cytokine-induced mobilization by G-CSF. Our results provide the first evidence for a distinct functional role of integrin alpha6 receptor during hematopoietic stem and progenitor cell homing and collaboration of alpha6 integrin with alpha4 integrin receptors during homing of short-term stem cells.
authors.affiliation: Hematopoietic Stem Cell Laboratory, BMC B12, Lund University, 221 84 Lund, Sweden.
authors.forename: Hong
authors.initials: H
authors.lastname: Qian
authors.forename: Karl
authors.initials: K
authors.lastname: Tryggvason
authors.forename: Sten Eirik
authors.initials: SE
authors.lastname: Jacobsen
authors.forename: Marja
authors.initials: M
authors.lastname: Ekblom
mesh_terms: D000818:Animals; D001854:Bone Marrow Cells / Q000502:physiology; D002465:Cell Movement; D003114:Colony-Forming Units Assay; D005260:Female; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000502:physiology*; D006801:Humans; D066298:In Vitro Techniques; D039441:Integrin alpha4 / Q000502:physiology*; D039503:Integrin alpha6 / Q000502:physiology*; D007797:Laminin / Q000378:metabolism; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D013154:Spleen / Q000166:cytology
chemical_list: D039503:Integrin alpha6; D007797:Laminin; D039441:Integrin alpha4