title: Tumor necrosis factor alpha and RANKL blockade cannot halt bony spur formation in experimental inflammatory arthritis.
abstract: OBJECTIVE
  To investigate the kinetics of bony spur formation and the relationship of bony spur formation to synovial inflammation and bone erosion in 2 rat arthritis models, and to address whether bony spur formation depends on the expression of tumor necrosis factor alpha (TNFalpha) or RANKL.
  
  
  METHODS
  Analysis of the kinetics of synovial inflammation, bone erosion, osteoclast formation, and growth of bony spurs was performed in rat collagen-induced arthritis (CIA) and adjuvant-induced arthritis (AIA). In addition, inhibition experiments were performed to assess whether inhibition of TNFalpha and RANKL by pegylated soluble TNF receptor type I (pegTNFRI) and osteoprotegerin (OPG), respectively, affected bony spur formation.
  
  
  RESULTS
  Bony spurs emerged from the periosteal surface close to joints, and initial proliferation of mesenchymal cells was noted as early as 3 days and 5 days after onset of CIA and AIA, respectively. Initiation of bony spur formation occurred shortly after the onset of inflammation and bone erosion. Neither pegTNFRI nor OPG could significantly halt the osteophytic responses in CIA and AIA.
  
  
  CONCLUSIONS
  These results suggest that bony spur formation is triggered by inflammation and initial structural damage in these rat models of inflammatory arthritis. Moreover, emergence of bony spurs depends on periosteal proliferation and is not affected by inhibition of either TNFalpha or RANKL. Bony spur formation can thus be considered a process that occurs independent of TNFalpha and RANKL and is triggered by destructive arthritis.
authors.affiliation: Department of Internal Medicine III and Institute for Clinical Immunology, University of Erlangen-Nuremberg, Krankenhausstrasse 12, Erlangen, Germany. georg.schett@uk-erlangen.de
authors.forename: Georg
authors.initials: G
authors.lastname: Schett
authors.forename: Marina
authors.initials: M
authors.lastname: Stolina
authors.forename: Denise
authors.initials: D
authors.lastname: Dwyer
authors.forename: Debra
authors.initials: D
authors.lastname: Zack
authors.forename: Stefan
authors.initials: S
authors.lastname: Uderhardt
authors.forename: Gerhard
authors.initials: G
authors.lastname: Krönke
authors.forename: Paul
authors.initials: P
authors.lastname: Kostenuik
authors.forename: Ulrich
authors.initials: U
authors.lastname: Feige
mesh_terms: D000818:Animals; D001169:Arthritis, Experimental / Q000378:metabolism* / Q000473:pathology; D049109:Cell Proliferation; D003094:Collagen / Q000009:adverse effects; D004195:Disease Models, Animal; D005260:Female; D008297:Male; D010010:Osteoclasts / Q000187:drug effects / Q000473:pathology; D010012:Osteogenesis / Q000187:drug effects; D054850:Osteophyte / Q000209:etiology / Q000378:metabolism* / Q000473:pathology; D053244:Osteoprotegerin / Q000494:pharmacology; D011092:Polyethylene Glycols / Q000494:pharmacology; D053245:RANK Ligand / Q000037:antagonists & inhibitors* / Q000378:metabolism; D051381:Rats; D011917:Rats, Inbred Lew; D047888:Receptors, Tumor Necrosis Factor, Type I / Q000494:pharmacology; D013583:Synovial Membrane / Q000187:drug effects / Q000473:pathology; D014409:Tumor Necrosis Factor-alpha / Q000037:antagonists & inhibitors* / Q000378:metabolism
chemical_list: D053244:Osteoprotegerin; C496217:PEGylated tumor necrosis factor alpha receptor 1; D053245:RANK Ligand; D047888:Receptors, Tumor Necrosis Factor, Type I; D014409:Tumor Necrosis Factor-alpha; D011092:Polyethylene Glycols; D003094:Collagen