title: Co-regulation of LPS and tensile strain downregulating osteogenicity via c-fos expression.
abstract: OBJECTIVE
  Orthodontic forces are known to aggravate inflammation-induced destruction of the periodontium, but the underlying mechanism has not been elucidated. The present study investigates how inflammation and forces co-regulate periodontium damage.
  
  
  METHODS
  Cultures of MC3T3-E1 osteoblasts were pre-treated with conditioned medium from RAW264.7 macrophages exposed to 100ng/ml Porphyromonas gingivalis (Pg)-LPS. Conditioned medium was analyzed by ELISA for interleukin-1 beta (IL-1β), interleukin-6 (IL-6), and tumor necrosis factor-alpha (TNF-α). Osteoblasts were then subjected to tensile strain (0.5Hz; 1000μ or 3000μ) for 0min, 5min, 15min, 30min, 1h, 3h, and 6h. The cultures were analyzed for mRNA and protein levels of c-fos. Cells were also analyzed for alkaline phosphatase (ALP) activity.
  
  
  RESULTS
  (Pg)-LPS stimulated the secretion of all three cytokines from RAW264.7 cells in a dose- and time-dependent manner. Medium from (Pg)-LPS stimulated cells induced a 10-fold increase in c-fos expression, which decreased to a 4-fold plateau after 3h. In contrast, ALP activity of control osteoblasts decreased during the first 60min, then recovered over the next 4h. Pretreatment with conditioned medium generated the same initial decrease during tensile strain but prevented the recovery.
  
  
  CONCLUSIONS
  Our study showed, for the first time, that the inhibitory effect of inflammation and tensile strain on osteogenicity is associated with the upregulation in c-fos expression. In addition, inflammation may reduce the ability of osteoblasts to restore their osteogenic capacity during sustained tensile stress and contribute to periodontium damage.
authors.affiliation: Orthodontic Department, School of Stomatology, Wenzhou Medical College, China.
authors.forename: Yi
authors.initials: Y
authors.lastname: Wang
authors.affiliation: Orthodontic Department, School of Stomatology, Wenzhou Medical College, China.
authors.forename: Haiyan
authors.initials: H
authors.lastname: Wang
authors.affiliation: Department of Orthodontics, James Cook University, Australia.
authors.forename: Qingsong
authors.initials: Q
authors.lastname: Ye
authors.affiliation: Orthodontic Department, School of Stomatology, Wenzhou Medical College, China.
authors.forename: Jie
authors.initials: J
authors.lastname: Ye
authors.affiliation: Orthodontic Department, Yiwu Central Hospital, China.
authors.forename: Chunyan
authors.initials: C
authors.lastname: Xu
authors.affiliation: Orthodontic Department, School of Stomatology, Wenzhou Medical College, China.
authors.forename: Leilei
authors.initials: L
authors.lastname: Lin
authors.affiliation: Periodontal Department, School of Stomatology, Wenzhou Medical College, China. Electronic address: dh0726@gmail.com.
authors.forename: Hui
authors.initials: H
authors.lastname: Deng
authors.affiliation: Orthodontic Department, School of Stomatology, Wenzhou Medical College, China. Electronic address: hurongdang@hotmail.com.
authors.forename: Rongdang
authors.initials: R
authors.lastname: Hu
mesh_terms: D000469:Alkaline Phosphatase / Q000378:metabolism; D000704:Analysis of Variance; D000818:Animals; D001696:Biomechanical Phenomena; D015153:Blotting, Western; D002460:Cell Line; D017077:Culture Media, Conditioned / Q000737:chemistry / Q000494:pharmacology; D017931:DNA Primers / Q000235:genetics; D004797:Enzyme-Linked Immunosorbent Assay; D053583:Interleukin-1beta / Q000378:metabolism; D015850:Interleukin-6 / Q000378:metabolism; D008070:Lipopolysaccharides / Q000378:metabolism*; D051379:Mice; D010006:Osteoblasts / Q000187:drug effects; D010012:Osteogenesis / Q000502:physiology*; D010518:Periodontitis / Q000503:physiopathology*; D016966:Porphyromonas gingivalis / Q000737:chemistry; D016760:Proto-Oncogene Proteins c-fos / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D020133:Reverse Transcriptase Polymerase Chain Reaction; D013314:Stress, Mechanical; D013997:Time Factors; D014409:Tumor Necrosis Factor-alpha / Q000378:metabolism
chemical_list: D017077:Culture Media, Conditioned; D017931:DNA Primers; D053583:Interleukin-1beta; D015850:Interleukin-6; D008070:Lipopolysaccharides; D016760:Proto-Oncogene Proteins c-fos; D014409:Tumor Necrosis Factor-alpha; D000469:Alkaline Phosphatase