title: GM-CSF cannot substitute for M-CSF in human osteoclastogenesis.
abstract: Osteopetrotic mice lacking functional M-CSF recover with ageing, suggesting alternate osteoclastogenesis pathways exist. One alternative is GM-CSF, treatment with which improves the osteopetrosis. Our objective was to determine whether GM-CSF could replace M-CSF in human osteoclastogenesis in vitro. Human CFU-GM precursors cultured with RANKL differentiate into osteoclasts without added M-CSF, indicating constitutive production of M-CSF. Addition of M-CSF antibody completely inhibited differentiation, demonstrating M-CSF-dependence in vitro. Co-treatment with low concentrations (0.01 ng/mL) of GM-CSF for 14 days or higher concentrations (10 ng/mL) for the first 1-2 days enhanced osteoclastogenesis but this effect was blocked with M-CSF antibody. Treatment with GM-CSF transiently increased M-CSF mRNA expression at 3 h but suppressed expression at 7-14 days. Neither FLT3-ligand nor VEGF supported osteoclastogenesis in the absence of M-CSF. Thus, in vitro human osteoclastogenesis is dependent on M-CSF and the stimulatory effects of GM-CSF are mediated by M-CSF. Rescue by GM-CSF in M-CSF-deficiency is unlikely to be directly mediated by FLT3-ligand or VEGF.
authors.affiliation: Department of Clinical and Biomedical Sciences, Barwon Health, University of Melbourne, Geelong, Victoria 3220, Australia. j.hodgel@pgrad.unimelb.edu.au
authors.forename: Jason M
authors.initials: JM
authors.lastname: Hodge
authors.forename: Mark A
authors.initials: MA
authors.lastname: Kirkland
authors.forename: Geoffrey C
authors.initials: GC
authors.lastname: Nicholson
mesh_terms: D000818:Animals; D001483:Base Sequence; D002352:Carrier Proteins; D003114:Colony-Forming Units Assay; D017931:DNA Primers; D005312:Fetal Blood / Q000166:cytology; D005786:Gene Expression Regulation / Q000187:drug effects; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000494:pharmacology*; D006801:Humans; D016173:Macrophage Colony-Stimulating Factor / Q000235:genetics / Q000494:pharmacology*; D008562:Membrane Glycoproteins; D051379:Mice; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects; D016133:Polymerase Chain Reaction / Q000379:methods; D053245:RANK Ligand; D012333:RNA, Messenger / Q000235:genetics; D053246:Receptor Activator of Nuclear Factor-kappa B; D011993:Recombinant Fusion Proteins / Q000494:pharmacology; D011994:Recombinant Proteins / Q000494:pharmacology; D014158:Transcription, Genetic; D042461:Vascular Endothelial Growth Factor A / Q000494:pharmacology
chemical_list: D002352:Carrier Proteins; D017931:DNA Primers; D008562:Membrane Glycoproteins; D053245:RANK Ligand; D012333:RNA, Messenger; D053246:Receptor Activator of Nuclear Factor-kappa B; D011993:Recombinant Fusion Proteins; D011994:Recombinant Proteins; C505686:TNFRSF11A protein, human; C505688:TNFSF11 protein, human; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; D042461:Vascular Endothelial Growth Factor A; D016173:Macrophage Colony-Stimulating Factor; D016178:Granulocyte-Macrophage Colony-Stimulating Factor