title: RANKL upregulation associated with periodontitis and Porphyromonas gingivalis.
abstract: BACKGROUND
  Receptor activator of nuclear factor-kappa B (NF-kappaB) ligand (RANKL) and osteoprotegerin (OPG) are critical for homeostatic control of osteoclast activity, suggesting their vital roles in the progression of bone loss in periodontitis. In this study, the expression of RANKL and OPG mRNA and the relationship between these factors and periodontopathic bacteria in periodontal tissue were studied.
  
  
  METHODS
  Gingival tissue and subgingival plaque samples were collected from 15 patients with chronic periodontitis and 15 periodontally healthy subjects. RNA was extracted from the tissue and subjected to reverse transcription-polymerase chain reaction (RT-PCR) using primers specific for RANKL or OPG. Beta-actin was amplified as a control to ensure equal loading. The intensity of RT-PCR products was analyzed by a densitometer in proportion to the intensity of beta-actin. The numbers of Porphyromonas gingivalis and Actinobacillus actinomycetemcomitans were determined by quantitative real-time PCR.
  
  
  RESULTS
  Our results showed increased levels of RANKL mRNA in chronic periodontitis tissues. The RANKL/OPG expression ratio was significantly higher in the periodontitis group compared to the healthy control group (P = 0.001). Interestingly, the expression of RANKL (r = 0.64; P <0.001), but not OPG (r = -0.24; P = 0.20), was significantly correlated with increased numbers of P. gingivalis. A. actinomycetemcomitans was detected in only 6.7% of all sites.
  
  
  CONCLUSIONS
  Chronic periodontitis was associated with RANKL mRNA upregulation and increased RANKL/OPG mRNA expression ratio. In addition, our data showed for the first time to our knowledge an association between upregulated RANKL levels and the number of P. gingivalis in clinically obtained periodontal tissues.
authors.affiliation: Department of Periodontology, Faculty of Dentistry, Khon Kaen University, Khon Kaen, Thailand. nawarat@kku.ac.th
authors.forename: Nawarat
authors.initials: N
authors.lastname: Wara-aswapati
authors.forename: Rudee
authors.initials: R
authors.lastname: Surarit
authors.forename: Anek
authors.initials: A
authors.lastname: Chayasadom
authors.forename: Jason A
authors.initials: JA
authors.lastname: Boch
authors.forename: Waranuch
authors.initials: W
authors.lastname: Pitiphat
mesh_terms: D000199:Actins / Q000032:analysis; D000328:Adult; D000367:Age Factors; D016976:Aggregatibacter actinomycetemcomitans / Q000235:genetics / Q000302:isolation & purification; D002908:Chronic Disease; D003773:Dental Plaque / Q000382:microbiology; D004812:Epidemiologic Methods; D005260:Female; D005881:Gingiva / Q000378:metabolism; D006801:Humans; D008297:Male; D008875:Middle Aged; D053244:Osteoprotegerin / Q000032:analysis / Q000378:metabolism*; D010518:Periodontitis / Q000378:metabolism / Q000382:microbiology*; D016966:Porphyromonas gingivalis / Q000235:genetics / Q000302:isolation & purification*; D053245:RANK Ligand / Q000032:analysis / Q000378:metabolism*; D012313:RNA / Q000032:analysis; D012333:RNA, Messenger / Q000032:analysis / Q000378:metabolism*; D020133:Reverse Transcriptase Polymerase Chain Reaction; D012737:Sex Factors; D015854:Up-Regulation
chemical_list: D000199:Actins; D053244:Osteoprotegerin; D053245:RANK Ligand; D012333:RNA, Messenger; C505688:TNFSF11 protein, human; D012313:RNA