title: [Cylic stretching force-induced late apoptosis in human periodontal ligament cells].
abstract: OBJECTIVE
  To investigate the effect of stretching force on late apoptosis of human periodontal ligament cells.
  
  
  METHODS
  HPDLCs were cultured in vitro, and cells were stretched by dynamic mechanical strain 1%, 10% and 20% for 6, 12, 24 and 48 h. Then late apoptosis were detected through TUNEL method binding by flow cytometry and confocal laser scanning microscopy. The data was analyzed with SPSS 11.0 software package.
  
  
  RESULTS
  HPDCLs inclined parallel to each other and aligned their long axis perpendicular to the stretching force vector. The number of apoptotic cells increased significantly in a time-and force-dependent manner in response to stretching strain within 24 h.
  
  
  CONCLUSIONS
  It is found that stretching force can induce apoptosis in HPDLC and show time- and stress-dependent manner with a tendency of increase in 24 h.
authors.affiliation: Department of Prosthodontics, Shanghai Ninth People's Hospital, College of Stomatology, Shanghai Jiao Tong University School of Medicine; Shanghai Key Laboratory of Stomatology. Shanghai 200011, China.E-mail:haoyi5315@163.com.
authors.forename: Yi
authors.initials: Y
authors.lastname: Hao
authors.forename: Jing
authors.initials: J
authors.lastname: Li
authors.forename: Jia-yin
authors.initials: JY
authors.lastname: Ma
authors.forename: Jun
authors.initials: J
authors.lastname: Li
authors.forename: Chun
authors.initials: C
authors.lastname: Xu
mesh_terms: D017209:Apoptosis; D002478:Cells, Cultured; D005434:Flow Cytometry; D006801:Humans; D055595:Mechanical Phenomena; D010513:Periodontal Ligament / Q000502:physiology*