title: Osteoclasts are essential for TNF-alpha-mediated joint destruction.
abstract: The detailed cellular and molecular mechanisms leading to joint destruction in rheumatoid arthritis, a disease driven by proinflammatory cytokines, are still unknown. To address the question of whether osteoclasts play a pivotal role in this process, transgenic mice that express human TNF (hTNFtg) and that develop a severe and destructive arthritis were crossed with osteopetrotic, c-fos-deficient mice (c-fos(-/-)) completely lacking osteoclasts. The resulting mutant mice (c-fos(-/-)hTNFtg) developed a TNF-dependent arthritis in the absence of osteoclasts. All clinical features of arthritis, such as paw swelling and reduction of grip strength, progressed equally in both groups. Histological evaluation of joint sections revealed no difference in the extent of synovial inflammation, its cellular composition (except for the lack of osteoclasts), and the expression of matrix metalloprotein-ase-3 (MMP-3) and MMP-13. In addition, cartilage damage, proteoglycan loss, and MMP-3, -9, and -13 expression in chondrocytes were similar in hTNFtg and c-fos(-/-)hTNFtg mice. However, despite the presence of severe inflammatory changes, c-fos(-/-)hTNFtg mice were fully protected against bone destruction. These data reveal that TNF-dependent bone erosion is mediated by osteoclasts and that the absence of osteoclasts alters TNF-mediated arthritis from a destructive to a nondestructive arthritis. Therefore, in addition to the use of anti-inflammatory therapies, osteoclast inhibition could be beneficial for the treatment of rheumatoid arthritis.
authors.affiliation: Department of Internal Medicine III, Division of Rheumatology, University of Vienna, Vienna, Austria.
authors.forename: Kurt
authors.initials: K
authors.lastname: Redlich
authors.forename: Silvia
authors.initials: S
authors.lastname: Hayer
authors.forename: Romeo
authors.initials: R
authors.lastname: Ricci
authors.forename: Jean-Pierre
authors.initials: JP
authors.lastname: David
authors.forename: Makiyeh
authors.initials: M
authors.lastname: Tohidast-Akrad
authors.forename: George
authors.initials: G
authors.lastname: Kollias
authors.forename: Günter
authors.initials: G
authors.lastname: Steiner
authors.forename: Josef S
authors.initials: JS
authors.lastname: Smolen
authors.forename: Erwin F
authors.initials: EF
authors.lastname: Wagner
authors.forename: Georg
authors.initials: G
authors.lastname: Schett
mesh_terms: D000818:Animals; D001172:Arthritis, Rheumatoid / Q000209:etiology* / Q000473:pathology / Q000503:physiopathology / Q000628:therapy; D002352:Carrier Proteins / Q000378:metabolism; D017364:Collagenases / Q000378:metabolism; D016762:Genes, fos; D006801:Humans; D053509:Matrix Metalloproteinase 13; D019278:Matrix Metalloproteinase 3 / Q000378:metabolism; D020780:Matrix Metalloproteinase 9 / Q000378:metabolism; D008562:Membrane Glycoproteins / Q000378:metabolism; D051379:Mice; D008810:Mice, Inbred C57BL; D018345:Mice, Knockout; D008822:Mice, Transgenic; D010010:Osteoclasts / Q000473:pathology / Q000502:physiology*; D010022:Osteopetrosis / Q000235:genetics / Q000473:pathology / Q000503:physiopathology; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D014409:Tumor Necrosis Factor-alpha / Q000172:deficiency / Q000235:genetics / Q000502:physiology*
chemical_list: D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; C505686:TNFRSF11A protein, human; C505688:TNFSF11 protein, human; C505687:Tnfrsf11a protein, mouse; C505689:Tnfsf11 protein, mouse; D014409:Tumor Necrosis Factor-alpha; D017364:Collagenases; C507079:MMP13 protein, human; D053509:Matrix Metalloproteinase 13; C507081:Mmp13 protein, mouse; D019278:Matrix Metalloproteinase 3; D020780:Matrix Metalloproteinase 9