title: Osteoimmunological mechanisms involved in orthodontically and bacterially induced periodontal stress.
abstract: OBJECTIVE
  Orthodontic tooth movement is known to cause sterile inflammation of the periodontal ligament (PDL). It may also be accompanied by pathological effects of external apical root resorption, with interindividual differences in the incidence and extent of resorption. An involvement of autoimmunological mechanisms is currently under discussion. This study aimed to improve our understanding of similarities between the inflammatory mechanisms underlying the pathophysiology of periodontitis and root resorption.
  
  
  METHODS
  Human PDL cells were stimulated with interleukin (IL)-1β/IL-17A/IFN-γ, or left non-stimulated. Their potential for phagocytosis was then evaluated by incubation with dextran or E. coli or S. aureus particles, followed by flow cytometric and immunohistochemical analysis. Real-time polymerase chain reaction (PCR) was used to analyze receptor activator of NF-κB ligand (RANKL) and osteoprotegerin (OPG) expression in PDL cells. Verification was obtained in vivo by studying IL-17A, RANKL, and OPG expression in biopsies of inflamed periodontal tissues and in biopsies of rat maxillae with mechanically induced root resorption. Statistical analysis included Wilcoxon's rank sum test to analyze gene expression data and one-way ANOVA in conjunction with Tukey's post hoc test to analyze flow cytometric data.
  
  
  RESULTS
  PDL cells phagocytosed foreign particles under both inflammatory and non-inflammatory conditions. Furthermore, IL-17A significantly downregulated RANKL expression while significantly upregulating OPG expression in PDL cells. These immunomodulatory cytokines were also demonstrable in both inflammatorily altered periodontal tissues and root resorption lacunae, while the incidence of IL-7A was strikingly variable in resorption areas.
  
  
  CONCLUSIONS
  PDL cells were demonstrated to effect phagocytosis and to express immunomodulatory molecules, which proves their capability of participating in periodontal osteoimmunological processes. The development of root resorption and periodontitis appears to be governed by similar pathophysiological mechanisms.
authors.affiliation: Department of Orthodontics, University of Bonn, Germany. konermann@uni-bonn.de
authors.forename: A
authors.initials: A
authors.lastname: Konermann
authors.forename: W
authors.initials: W
authors.lastname: Götz
authors.forename: D
authors.initials: D
authors.lastname: Wohlleber
authors.forename: P
authors.initials: P
authors.lastname: Knolle
authors.forename: J
authors.initials: J
authors.lastname: Deschner
authors.forename: A
authors.initials: A
authors.lastname: Jäger
mesh_terms: D000293:Adolescent; D001424:Bacterial Infections / Q000276:immunology*; D002478:Cells, Cultured; D016207:Cytokines / Q000276:immunology*; D005260:Female; D006801:Humans; D008297:Male; D010513:Periodontal Ligament / Q000276:immunology* / Q000473:pathology; D010518:Periodontitis / Q000276:immunology*; D010587:Phagocytosis / Q000276:immunology*; D012391:Root Resorption / Q000276:immunology* / Q000473:pathology; D013312:Stress, Physiological / Q000276:immunology; D014087:Tooth Movement Techniques / Q000009:adverse effects*
chemical_list: D016207:Cytokines