title: Osteoclast differentiation during experimental tooth movement by a short-term force application: an immunohistochemical study in rats.
abstract: OBJECTIVE
  The origin of osteoclasts responsible for bone resorption during orthodontic tooth movement is not yet clear. Their precursors may reside within the periodontal ligament (PDL) or could be recruited from the circulation or the bone marrow. The aim of this study was to investigate the spatial and sequential distribution of osteoclast precursors during experimental tooth movement by using three differentiation markers: receptor for macrophage colony stimulating factor (c-Fms), receptor activator of nuclear factor-kappaB (RANK), and calcitonin receptor (CTR).
  
  
  METHODS
  Six-week-old Wistar rats were used. Elastic bands were inserted between the upper 1st and 2nd molars for 1, 2, 3, and 6 days. Immunohistochemical staining for c-Fms, RANK, or CTR was performed on parasagittal sections and positive cells were counted.
  
  
  RESULTS
  Before force application, many c-Fms+ and a few RANK+ precursors were present in the bone marrow. No c-Fms+ osteoclast precursors were observed in the PDL. After force application, the number of RANK+ but not c-Fms+ precursors increased rapidly in the PDL. In bone marrow, the number of c-Fms+ and RANK+ precursors also increased rapidly, as did multinuclear c-Fms+, RANK+, and CTR+ cells. Subsequently, the number of c-Fms+, RANK+, and CTR+ multinuclear cells in the PDL increased. After 6 days, the expression profiles tended to return to baseline levels.
  
  
  CONCLUSIONS
  Osteoclast precursors differentiate within the bone marrow and then migrate into the PDL during early tooth movement.
authors: Department of Orthodontics and Oral Biology, Radboud University Nijmegen Medical Centre, Nijmegen, The Netherlands.
authors: Rui
authors: R
authors: Xie
authors: Anne Marie
authors: AM
authors: Kuijpers-Jagtman
authors: Jaap C
authors: JC
authors: Maltha
mesh_terms: D000818:Animals; D015415:Biomarkers / Q000032:analysis; D001854:Bone Marrow Cells / Q000378:metabolism; D002454:Cell Differentiation; D002465:Cell Movement; D003799:Dental Stress Analysis; D007150:Immunohistochemistry; D008297:Male; D010010:Osteoclasts / Q000166:cytology*; D010513:Periodontal Ligament / Q000166:cytology*; D051381:Rats; D017208:Rats, Wistar; D053246:Receptor Activator of Nuclear Factor-kappa B / Q000032:analysis / Q000096:biosynthesis; D016186:Receptor, Macrophage Colony-Stimulating Factor / Q000032:analysis / Q000096:biosynthesis; D018003:Receptors, Calcitonin / Q000032:analysis / Q000096:biosynthesis; D014087:Tooth Movement Techniques
chemical_list: D015415:Biomarkers; D053246:Receptor Activator of Nuclear Factor-kappa B; D018003:Receptors, Calcitonin; D016186:Receptor, Macrophage Colony-Stimulating Factor