title: Diverse effects of Porphyromonas gingivalis on human osteoclast formation.
abstract: Porphyromonas gingivalis is associated with periodontitis, a chronic inflammatory disease of the tooth-supporting tissues. A major clinical symptom is alveolar bone loss due to excessive resorption by osteoclasts. P. gingivalis may influence osteoclast formation in diverse ways; by interacting directly with osteoclast precursors that likely originate from peripheral blood, or indirectly by activating gingival fibroblasts, cells that can support osteoclast formation. In the present study we investigated these possibilities. Conditioned medium from viable or dead P. gingivalis, or from gingival fibroblasts challenged with viable or dead P. gingivalis were added to human mononuclear osteoclast precursors. After 21 days of culture the number of multinucleated (≥3 nuclei) tartrate resistant acid phosphatase (TRACP)-positive cells was determined as a measure for osteoclast formation. Conditioned medium from viable P. gingivalis, and from fibroblasts with viable P. gingivalis stimulated osteoclast formation (1.6-fold increase p < 0.05). Conditioned medium from dead bacteria had no effect on osteoclast formation, whereas conditioned medium from fibroblasts with dead bacteria stimulated formation (1.4-fold increase, p < 0.05). Inhibition of P. gingivalis LPS activity by Polymyxin B reduced the stimulatory effect of conditioned medium. Interestingly, when RANKL and M-CSF were added to cultures, conditioned media inhibited osteoclast formation (0.6-0.7-fold decrease, p < 0.05). Our results indicate that P. gingivalis influences osteoclast formation in vitro in different ways. Directly, by bacterial factors, likely LPS, or indirectly, by cytokines produced by gingival fibroblasts in response to P. gingivalis. Depending on the presence of RANKL and M-CSF, the effect of P. gingivalis is either stimulatory or inhibitory.
authors.affiliation: Department of Oral Microbiology, Academic Centre for Dentistry Amsterdam, University of Amsterdam and VU University Amsterdam, The Netherlands.
authors.forename: Nina
authors.initials: N
authors.lastname: Scheres
authors.forename: Teun J
authors.initials: TJ
authors.lastname: de Vries
authors.forename: Jorg
authors.initials: J
authors.lastname: Brunner
authors.forename: Wim
authors.initials: W
authors.lastname: Crielaard
authors.forename: Marja L
authors.initials: ML
authors.lastname: Laine
authors.forename: Vincent
authors.initials: V
authors.lastname: Everts
mesh_terms: D000293:Adolescent; D000328:Adult; D002454:Cell Differentiation; D002478:Cells, Cultured; D017077:Culture Media, Conditioned; D016207:Cytokines / Q000276:immunology / Q000378:metabolism; D005260:Female; D005347:Fibroblasts / Q000382:microbiology / Q000502:physiology; D006801:Humans; D008070:Lipopolysaccharides / Q000276:immunology / Q000378:metabolism; D016173:Macrophage Colony-Stimulating Factor / Q000378:metabolism; D008297:Male; D010010:Osteoclasts / Q000382:microbiology* / Q000502:physiology*; D016966:Porphyromonas gingivalis / Q000472:pathogenicity*; D053245:RANK Ligand / Q000378:metabolism; D013234:Stem Cells / Q000382:microbiology / Q000502:physiology; D055815:Young Adult
chemical_list: D017077:Culture Media, Conditioned; D016207:Cytokines; D008070:Lipopolysaccharides; D053245:RANK Ligand; C505688:TNFSF11 protein, human; D016173:Macrophage Colony-Stimulating Factor