title: Generation of human osteoclasts in stromal cell-free and stromal cell-rich cultures: differences in osteoclast CD11c/CD18 integrin expression.
abstract: Osteoclasts form in the presence of macrophage colony-stimulating factor (M-CSF) and receptor activator of Nfkappab ligand (RANKL), a membrane-bound differentiation factor that is now available as a soluble recombinant molecule. Acquisition of the osteoclast phenotype [the alphavbeta3 subunit of the vitronectin receptor (VNR)-, calcitonin receptor (CTR)- and F-actin ring-positive cells] is associated with loss of monocyte/macrophage-associated integrins, specifically CD11b, CD11c and CD18. We hypothesized that differences in the osteoclast integrin adhesion molecule profile may exist in osteoclasts generated in stromal cell-rich and in stromal-free conditions. Unlike osteoclasts generated in vivo, F-actin ring-positive (resorbing) osteoclasts formed in soluble RANKL in vitro, in the absence of stromal cells, and co-expressed CD11c and CD18. However, when osteoclasts were generated from peripheral blood mononuclear cells (PBMNCs) in co-cultures with the murine bone marrow stromal cell line 218 (which does not produce membrane-bound RANKL) in the presence of soluble RANKL, CD11c and CD18 were not expressed by osteoclasts. These findings indicate that the persistent expression of CD11c and CD18 is not accounted for by RANKL being presented in a soluble form and that membrane-bound RANKL is not required for the normal integrin expression in resorbing osteoclasts. This study demonstrates that potentially misleading information may arise by using data obtained from osteoclasts generated in the absence of stromal cells as they do not completely reflect the situation in vivo.
authors.affiliation: The Department of Histopathology, Imperial College School of Medicine (St Mary's Campus), Norfolk Place, London, UK.
authors.forename: C S
authors.initials: CS
authors.lastname: Lader
authors.forename: J
authors.initials: J
authors.lastname: Scopes
authors.forename: M A
authors.initials: MA
authors.lastname: Horton
authors.forename: A M
authors.initials: AM
authors.lastname: Flanagan
mesh_terms: D000199:Actins / Q000378:metabolism; D000328:Adult; D000704:Analysis of Variance; D001854:Bone Marrow Cells; D001862:Bone Resorption; D018821:CD18 Antigens / Q000032:analysis; D002352:Carrier Proteins / Q000494:pharmacology*; D002454:Cell Differentiation; D002478:Cells, Cultured; D018920:Coculture Techniques; D003470:Culture Media; D006801:Humans; D007150:Immunohistochemistry; D016167:Integrin alphaXbeta2 / Q000032:analysis; D016023:Integrins / Q000032:analysis*; D008562:Membrane Glycoproteins / Q000494:pharmacology*; D018613:Microscopy, Confocal; D010010:Osteoclasts / Q000276:immunology*; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018124:Receptors, Tumor Necrosis Factor / Q000378:metabolism; D011994:Recombinant Proteins / Q000494:pharmacology
chemical_list: D000199:Actins; D018821:CD18 Antigens; D002352:Carrier Proteins; D003470:Culture Media; D016167:Integrin alphaXbeta2; D016023:Integrins; D008562:Membrane Glycoproteins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D018124:Receptors, Tumor Necrosis Factor; D011994:Recombinant Proteins; C505686:TNFRSF11A protein, human; C505688:TNFSF11 protein, human