title: Endotoxins potentiate COX-2 and RANKL expression in compressed PDL cells.
abstract: OBJECTIVE
  This study aims to demonstrate in vitro the synergistic effect of orthodontic forces and periodontal pathogens on cyclooxygenase-2 regulation and the subsequent receptor activator of nuclear factor kappa-B ligand (RANKL) production from periodontal ligament (PDL) cells.
  
  
  METHODS
  In comparison to a control group, three experimental groups were formed from human primary PDL cells stressed with compressive forces, bacterial endotoxins, or a combination of both. Gene expression of cyclooxygenase-2 and RANKL was analysed with RT real-time PCR. The prostaglandin E2 production was determined with ELISA. A co-culture of PDL cells and an osteoclast-progenitor cell line was used in order to demonstrate the osteoclast formation effect caused by the simultaneous combined stress.
  
  
  RESULTS
  The simultaneous combined stress resulted in a 56-fold up-regulation of cyclooxygenase-2 gene expression with a subsequent noticeable rise in the prostaglandin E2 in the culture medium. The RANKL/osteoprotegerin gene expression ratio was 50-fold up-regulated and the osteoclast formation assay revealed 153.5 ± 15.7 tartrate-resistant acid phosphatase (TRAP)-positive cells per well compared with 42.3 ± 3.8 TRAP-positive cells per well of the control group.
  
  
  CONCLUSIONS
  The synergistic action of periodontal pathogens and orthodontic forces leads to an increased expression of cyclooxygenase-2 from PDL cells that intensify the RANKL production which in turn induces osteoclast differentiation and subsequent osteoclastogenesis.
  
  
  CONCLUSIONS
  The present study puts an emphasis on the detrimental effect of orthodontic forces on patients with an active periodontal disease by underlining the significance of cyclooxygenase-2 activity and RANKL binding on the osteoclastogenesis process.
authors: Department of Orthodontics, University Medical Centre Regensburg, Franz-Josef-Strauss-Allee 11, 93053, Regensburg, Germany, piero.roemer@gmx.de.
authors: Piero
authors: P
authors: Römer
authors: Josef
authors: J
authors: Köstler
authors: Vasiliki
authors: V
authors: Koretsi
authors: Peter
authors: P
authors: Proff
mesh_terms: D000293:Adolescent; D000328:Adult; D001483:Base Sequence; D002478:Cells, Cultured; D051546:Cyclooxygenase 2 / Q000235:genetics / Q000378:metabolism*; D017931:DNA Primers; D015232:Dinoprostone / Q000378:metabolism; D004731:Endotoxins / Q000494:pharmacology*; D004797:Enzyme-Linked Immunosorbent Assay; D006801:Humans; D008297:Male; D010513:Periodontal Ligament / Q000166:cytology / Q000187:drug effects* / Q000378:metabolism; D053245:RANK Ligand / Q000235:genetics / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D055815:Young Adult
chemical_list: D017931:DNA Primers; D004731:Endotoxins; D053245:RANK Ligand; C505688:TNFSF11 protein, human; D051546:Cyclooxygenase 2; D015232:Dinoprostone
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