title: Lack of CD47 impairs bone cell differentiation and results in an osteopenic phenotype in vivo due to impaired signal regulatory protein α (SIRPα) signaling.
abstract: Here, we investigated whether the cell surface glycoprotein CD47 was required for normal formation of osteoblasts and osteoclasts and to maintain normal bone formation activity in vitro and in vivo. In parathyroid hormone or 1α,25(OH)2-vitamin D3 (D3)-stimulated bone marrow cultures (BMC) from CD47(-/-) mice, we found a strongly reduced formation of multinuclear tartrate-resistant acid phosphatase (TRAP)(+) osteoclasts, associated with reduced expression of osteoclastogenic genes (nfatc1, Oscar, Trap/Acp, ctr, catK, and dc-stamp). The production of M-CSF and RANKL (receptor activator of nuclear factor κβ ligand) was reduced in CD47(-/-) BMC, as compared with CD47(+/+) BMC. The stromal cell phenotype in CD47(-/-) BMC involved a blunted expression of the osteoblast-associated genes osterix, Alp/Akp1, and α-1-collagen, and reduced mineral deposition, as compared with that in CD47(+/+) BMC. CD47 is a ligand for SIRPα (signal regulatory protein α), which showed strongly reduced tyrosine phosphorylation in CD47(-/-) bone marrow stromal cells. In addition, stromal cells lacking the signaling SIRPα cytoplasmic domain also had a defect in osteogenic differentiation, and both CD47(-/-) and non-signaling SIRPα mutant stromal cells showed a markedly reduced ability to support osteoclastogenesis in wild-type bone marrow macrophages, demonstrating that CD47-induced SIRPα signaling is critical for stromal cell support of osteoclast formation. In vivo, femoral bones of 18- or 28-week-old CD47(-/-) mice showed significantly reduced osteoclast and osteoblast numbers and exhibited an osteopenic bone phenotype. In conclusion, lack of CD47 strongly impairs SIRPα-dependent osteoblast differentiation, deteriorate bone formation, and cause reduced formation of osteoclasts.
authors.affiliation: From the Departments of Odontology, Section for Molecular Periodontology, Umeå University, 901 87 Umea, Sweden.
authors.forename: Cecilia
authors.initials: C
authors.lastname: Koskinen
authors.forename: Emelie
authors.initials: E
authors.lastname: Persson
authors.forename: Paul
authors.initials: P
authors.lastname: Baldock
authors.forename: Åsa
authors.initials: Å
authors.lastname: Stenberg
authors.forename: Ingrid
authors.initials: I
authors.lastname: Boström
authors.forename: Takashi
authors.initials: T
authors.lastname: Matozaki
authors.forename: Per-Arne
authors.initials: PA
authors.lastname: Oldenborg
authors.forename: Pernilla
authors.initials: P
authors.lastname: Lundberg
mesh_terms: D000818:Animals; D015153:Blotting, Western; D001851:Bone Diseases, Metabolic / Q000235:genetics* / Q000378:metabolism; D001854:Bone Marrow Cells / Q000166:cytology / Q000378:metabolism; D001842:Bone and Bones / Q000166:cytology / Q000378:metabolism*; D051928:CD47 Antigen / Q000235:genetics* / Q000378:metabolism; D002454:Cell Differentiation / Q000235:genetics*; D002478:Cells, Cultured; D018920:Coculture Techniques; D051379:Mice; D008807:Mice, Inbred BALB C; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D009154:Mutation; D023461:Myeloid Progenitor Cells / Q000166:cytology / Q000378:metabolism; D010006:Osteoblasts / Q000166:cytology / Q000378:metabolism; D010010:Osteoclasts / Q000166:cytology / Q000378:metabolism; D010012:Osteogenesis / Q000235:genetics; D010641:Phenotype; D011971:Receptors, Immunologic / Q000235:genetics* / Q000378:metabolism; D020133:Reverse Transcriptase Polymerase Chain Reaction; D015398:Signal Transduction / Q000235:genetics; D017154:Stromal Cells / Q000166:cytology / Q000378:metabolism
chemical_list: D051928:CD47 Antigen; C497895:Cd47 protein, mouse; C501922:Sirpa protein, mouse; D011971:Receptors, Immunologic
keywords: Bone; CD47; Cell Differentiation; Osteoblasts; Osteoclast; SIRPalpha; Stromal Cell