title: The effect of centrifugal force on the mRNA and protein levels of ATF4 in cultured human periodontal ligament fibroblasts.
abstract: OBJECTIVE
  The aim of this study was to examine the changes of ATF4 expression in cultured human periodontal ligament fibroblasts (hPDLF) after mechanical stimuli, and to investigate whether ATF4 is essential for the mechanical stress-induced hPDLF differentiation.
  
  
  METHODS
  Reverse transcriptase polymerase chain reaction (RT-PCR) and western blotting were used to examine mRNA and protein levels of ATF4 expression in hPDLFs after application of centrifugal force. pMyc-ATF4 transfected cells were subjected to centrifugal force for 30min, and the changes of alkaline phosphatase (ALP) activity and osteocalcin (OCN), osteopontin (OPN), collagen I (COLI), bone sialoprotein (BSP) genes were measured to assess the differentiation of hPDLFs.
  
  
  RESULTS
  The mRNA and protein levels of ATF4 increased shortly and then decreased rapidly towards its pre-pressure levels. Overexpression of pMyc-ATF4 exhibited a greater increase in ALP activity and all four osteogenic genes compared to the untransfected cells in response to the centrifugal force.
  
  
  CONCLUSIONS
  Our results indicate that ATF4 is essential in response of hPDLFs to mechanical stress, resulting in increased differentiation of hPDLFs to osteoblast-like cells.
authors.affiliation: Department of Orthodontics, Shandong University, Shandong Province, Jinan 250012, People's Republic of China.
authors.forename: Fulan
authors.initials: F
authors.lastname: Wei
authors.forename: Chunling
authors.initials: C
authors.lastname: Wang
authors.forename: Gengyin
authors.initials: G
authors.lastname: Zhou
authors.forename: Dongxu
authors.initials: D
authors.lastname: Liu
authors.forename: Xiaofang
authors.initials: X
authors.lastname: Zhang
authors.forename: Yanhong
authors.initials: Y
authors.lastname: Zhao
authors.forename: Yuhua
authors.initials: Y
authors.lastname: Zhang
authors.forename: Qifeng
authors.initials: Q
authors.lastname: Yang
mesh_terms: D051701:Activating Transcription Factor 4 / Q000032:analysis / Q000235:genetics*; D000293:Adolescent; D015153:Blotting, Western / Q000379:methods; D002478:Cells, Cultured; D002498:Centrifugation; D002648:Child; D005347:Fibroblasts / Q000187:drug effects / Q000378:metabolism; D015870:Gene Expression / Q000187:drug effects; D006801:Humans; D010513:Periodontal Ligament / Q000187:drug effects / Q000378:metabolism*; D012333:RNA, Messenger / Q000032:analysis*; D011993:Recombinant Fusion Proteins / Q000235:genetics; D020133:Reverse Transcriptase Polymerase Chain Reaction / Q000379:methods; D014162:Transfection / Q000379:methods