title: Differential gene expression of periodontal ligament cells after loading of static compressive force.
abstract: BACKGROUND
  Compressive force is an important mechanical stimulus on the periodontal ligament (PDL) and is closely related to therapeutic tooth movement. In this study, early or late response genes related to the compressive stress in PDL cells were evaluated. Particularly, the expression of interleukin (IL)-6, IL-8, and alkaline phosphatase (ALP) was studied.
  
  
  METHODS
  The primary cultured cells from PDL were grown in a three-dimensional collagen gel, and received a continuous static compressive force (1.76 g/cm(2)). The expressed genes were screened by cDNA microarray assays for 2 or 12 hours after the initiation of the mechanical force application. The genes of interest that showed significant changes in expression in the cDNA microarray assay were analyzed further by quantitative reverse transcriptase polymerase chain reaction (RT-PCR), enzyme-linked immunoabsorbent assays (ELISA), and ALP assays.
  
  
  RESULTS
  ALP, IL-6, and IL-8 were selected among the genes that significantly changed expression (/M/ >0.7) and subsequently were confirmed by quantitative RT-PCR. The secreted protein concentrations for IL-6, IL-8, and ALP activity were measured at 72 hours after application of continuous static compressive force. The protein level of IL-6 was significantly increased at 72 hours (P <0.001), but there was no significant change in IL-8 (P >0.05). ALP activity was decreased approximately 41.5% compared to the control (P = 0.015).
  
  
  CONCLUSIONS
  Considering that IL-6 is a potent osteoclast activator and the compressive side of PDL during orthodontic tooth movement shows the resorption of calcified tissue, the changed expression of IL-6 and ALP in response to the static compressive force in PDL cells may contribute to the orthodontic tooth movement or alveolar bone remodeling.
authors.affiliation: Department of Orthodontics, College of Dentistry, Seoul National University, Seoul, Korea.
authors.forename: Yeon-Hee
authors.initials: YH
authors.lastname: Lee
authors.forename: Dong-Seok
authors.initials: DS
authors.lastname: Nahm
authors.forename: Youn-Kwan
authors.initials: YK
authors.lastname: Jung
authors.forename: Je-Yong
authors.initials: JY
authors.lastname: Choi
authors.forename: Sahng Gyoon
authors.initials: SG
authors.lastname: Kim
authors.forename: Michael
authors.initials: M
authors.lastname: Cho
authors.forename: Myung-Hee
authors.initials: MH
authors.lastname: Kim
authors.forename: Chang-Hoon
authors.initials: CH
authors.lastname: Chae
authors.forename: Seong-Gon
authors.initials: SG
authors.lastname: Kim
mesh_terms: D000469:Alkaline Phosphatase / Q000096:biosynthesis / Q000235:genetics; D016723:Bone Remodeling / Q000235:genetics; D018929:Cell Culture Techniques; D002478:Cells, Cultured; D019245:Compressive Strength; D003799:Dental Stress Analysis; D004797:Enzyme-Linked Immunosorbent Assay; D015870:Gene Expression; D020869:Gene Expression Profiling; D006801:Humans; D015850:Interleukin-6 / Q000096:biosynthesis* / Q000235:genetics; D016209:Interleukin-8 / Q000096:biosynthesis / Q000235:genetics; D020411:Oligonucleotide Array Sequence Analysis; D010513:Periodontal Ligament / Q000166:cytology / Q000378:metabolism / Q000502:physiology*; D020133:Reverse Transcriptase Polymerase Chain Reaction
chemical_list: D015850:Interleukin-6; D016209:Interleukin-8; D000469:Alkaline Phosphatase