title: Tumor necrosis factor-α antagonist infliximab inhibits osteoclast formation of peripheral blood mononuclear cells but does not affect periodontal ligament fibroblast-mediated osteoclast formation.
abstract: OBJECTIVE
  The inflammatory cytokine tumor necrosis factor-alpha (TNF-α) is elevated in inflamed periodontal tissues and may contribute to periodontitis progression. TNF-α stimulates formation and activity of osteoclasts, the cells that are recruited in periodontitis, that cause alveolar bone degradation and subsequent tooth loss. We previously showed that TNF-α is elevated in co-cultures of periodontal ligament fibroblast (PDLF) and peripheral blood mononuclear cells (PBMC). Hence, TNF-α could be a determining factor in osteoclast formation in these cultures, as osteoclasts are formed despite the fact that prototypical osteoclast differentiation factor receptor activator of nuclear factor kappa-B ligand is outnumbered at least 100-fold by its inhibitor osteoprotegerin in these cultures.
  
  
  METHODS
  To assess the role of TNF-α in periodontitis-associated osteoclast formation in vitro, osteoclast formation was analyzed in the presence of the anti-TNF-α therapeutic agent infliximab in two culture systems: (i) PBMC in co-culture with PDLFs from controls and patients with periodontitis, or (ii) with PBMC only. PDLFs from control and patients with periodontitis were exposed to infliximab, PBMCs were added and the formation of osteoclast-like cells was assessed.
  
  
  RESULTS
  TNF-α was highest levels in supernatants at 7 d in co-cultures and declined at 14 and 21 d. TNF-α was undetectable in cultures that received infliximab. The formation and activity of osteoclasts in co-cultures was not affected by infliximab. In contrast, infliximab in cultures of only PBMC significantly reduced the formation of osteoclasts. This reduction was accompanied by a decreased number and size of cell clusters, a step that precedes the formation of osteoclasts. TNF-α was again undetectable in the supernatant of infliximab-treated cultures, but was detectable at similar levels in cell lysates of control and infliximab-treated PBMC cultures.
  
  
  CONCLUSIONS
  Our study shows that the contribution of TNF-α to osteoclast formation is cell system dependent. It contributes to PBMC-induced osteoclast formation, possibly by establishing stronger cell-cell interactions that precede osteoclast formation.
authors.affiliation: Department of Periodontology, Academic Centre for Dentistry Amsterdam (ACTA), Research Institute MOVE, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: T J
authors.initials: TJ
authors.lastname: de Vries
authors.affiliation: Department of Periodontology, Academic Centre for Dentistry Amsterdam (ACTA), Research Institute MOVE, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: J
authors.initials: J
authors.lastname: Yousovich
authors.affiliation: Department of Periodontology, Academic Centre for Dentistry Amsterdam (ACTA), Research Institute MOVE, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: T
authors.initials: T
authors.lastname: Schoenmaker
authors.affiliation: Department of Preventive Dentistry, Academic Centre for Dentistry Amsterdam (ACTA), Research Institute MOVE, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: N
authors.initials: N
authors.lastname: Scheres
authors.affiliation: Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), Research Institute MOVE, University of Amsterdam and VU University Amsterdam, Amsterdam, The Netherlands.
authors.forename: V
authors.initials: V
authors.lastname: Everts
mesh_terms: D002352:Carrier Proteins; D002454:Cell Differentiation; D005347:Fibroblasts; D006801:Humans; D000069285:Infliximab; D007963:Leukocytes, Mononuclear; D008562:Membrane Glycoproteins; D010010:Osteoclasts; D010513:Periodontal Ligament; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D014409:Tumor Necrosis Factor-alpha
chemical_list: D002352:Carrier Proteins; D008562:Membrane Glycoproteins; D053245:RANK Ligand; D053246:Receptor Activator of Nuclear Factor-kappa B; D014409:Tumor Necrosis Factor-alpha; D000069285:Infliximab
keywords: TNF-α; cell differentiation; osteoclast formation; periodontal ligament; peripheral blood