title: Resting T cells negatively regulate osteoclast generation from peripheral blood monocytes.
abstract: There is accumulating evidence that T cells may be involved in osteoclastogenesis in a variety of murine systems. However, the precise role of human T cells in the regulation of osteoclast generation is still unclear. To address this issue, we investigated the effect of resting peripheral T cells on receptor activator of NF-kappaB ligand (RANKL)-induced osteoclast generation from human peripheral monocytes. Although osteoclasts were not generated in the culture of human peripheral blood mononuclear cells (PBMC) in the presence of RANKL and macrophage colony-stimulating factor (M-CSF), the addition of cyclosporine A (CsA), a potent inhibitor of T-cell function, resulted in the formation of an increasing number of lacunae resorption on dentine, suggesting T cells may inhibit osteoclast formation. In a coculture of T cells and monocytes, which were isolated from PBMC, T cells inhibited the osteoclast generation from monocytes, as determined by tartrate-resistant acid phosphatase (TRAP) staining and a pit assay using dentine. This inhibition of osteoclast generation by T cells was also observed in a culture of the parathyroid hormone-stimulated SaOS4/3 osteoblast cell line and monocytes. The culture in Transwell plates revealed that the cell-to-cell interaction was not required for the inhibition, suggesting that T-cell cytokines may be responsible for the inhibition. Among inhibitory T-cell cytokines on osteoclastogenesis, granulocyte-macrophage colony-stimulating factor (GM-CSF) and interferon-gamma (IFN-gamma) were actively produced by CD4 T cells but not CD8 T cells in the coculture of T cells with monocytes, and the neutralizing antibodies to these cytokines partially rescued the T-cell-induced inhibition of osteoclast formation. Although CsA did not affect RANKL-induced osteoclast generation in the culture of monocytes alone, it completely rescued the T-cell-induced inhibition of osteoclast formation and strongly inhibited the production of GM-CSF and IFN-gamma. Thus, we demonstrate that resting T cells negatively regulate the osteoclast generation via production of GM-CSF and IFN-gamma by CD4 T cells and that CsA stimulates the osteoclast generation through the inhibition of the production of these cytokines. These findings provide new insight into therapeutic strategies for immunosuppression-induced bone loss in transplant and other diseases.
authors.affiliation: First Department of Internal Medicine, Toyama Medical and Pharmaceutical University, Toyama 930-0194, Japan.
authors.forename: K
authors.initials: K
authors.lastname: Shinoda
authors.forename: E
authors.initials: E
authors.lastname: Sugiyama
authors.forename: H
authors.initials: H
authors.lastname: Taki
authors.forename: S
authors.initials: S
authors.lastname: Harada
authors.forename: T
authors.initials: T
authors.lastname: Mino
authors.forename: M
authors.initials: M
authors.lastname: Maruyama
authors.forename: M
authors.initials: M
authors.lastname: Kobayashi
mesh_terms: D016723:Bone Remodeling / Q000187:drug effects / Q000276:immunology*; D001862:Bone Resorption / Q000276:immunology / Q000473:pathology; D015496:CD4-Positive T-Lymphocytes / Q000276:immunology; D018414:CD8-Positive T-Lymphocytes / Q000276:immunology; D002352:Carrier Proteins / Q000494:pharmacology; D002450:Cell Communication / Q000276:immunology; D002454:Cell Differentiation / Q000187:drug effects / Q000276:immunology; D002460:Cell Line; D018920:Coculture Techniques; D016572:Cyclosporine / Q000494:pharmacology; D016178:Granulocyte-Macrophage Colony-Stimulating Factor / Q000096:biosynthesis; D006801:Humans; D007166:Immunosuppressive Agents / Q000494:pharmacology; D007371:Interferon-gamma / Q000096:biosynthesis; D016173:Macrophage Colony-Stimulating Factor / Q000494:pharmacology; D008562:Membrane Glycoproteins / Q000494:pharmacology; D009000:Monocytes / Q000166:cytology* / Q000187:drug effects / Q000276:immunology*; D010010:Osteoclasts / Q000166:cytology* / Q000187:drug effects / Q000276:immunology*; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D013601:T-Lymphocytes / Q000276:immunology*
chemical_list: D002352:Carrier Proteins; D007166:Immunosuppressive Agents; D008562:Membrane Glycoproteins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; C505686:TNFRSF11A protein, human; C505688:TNFSF11 protein, human; D016173:Macrophage Colony-Stimulating Factor; D007371:Interferon-gamma; D016178:Granulocyte-Macrophage Colony-Stimulating Factor; D016572:Cyclosporine