title: The Effect of Altered Loading on Mandibular Condylar Cartilage.
abstract: OBJECTIVE
  The purpose of this study was to delineate the cellular, mechanical and morphometric effects of altered loading on the mandibular condylar cartilage (MCC) and subchondral bone. We hypothesized that altered loading will induce differentiation of cells by accelerating the lineage progression of the MCC.
  
  
  METHODS
  Four-week-old male Dkk3 XCol2A1XCol10A1 mice were randomly divided into two groups: (1) Loaded-Altered loading of MCC was induced by forced mouth opening using a custom-made spring; (2) Control-served as an unloaded group. Mice were euthanized and flow cytometery based cell analysis, micro-CT, gene expression analysis, histology and morphometric measurements were done to assess the response.
  
  
  RESULTS
  Our flow cytometery data showed that altered loading resulted in a significant increase in a number of Col2a1-positive (blue) and Col10a1-positive (red) expressing cells. The gene expression analysis showed significant increase in expression of BMP2, Col10a1 and Sox 9 in the altered loading group. There was a significant increase in the bone volume fraction and trabecular thickness, but a decrease in the trabecular spacing of the subchondral bone with the altered loading. Morphometric measurements revealed increased mandibular length, increased condylar length and increased cartilage width with altered loading. Our histology showed increased mineralization/calcification of the MCC with 5 days of loading. An unexpected observation was an increase in expression of tartrate resistant acid phosphatase activity in the fibrocartilaginous region with loading.
  
  
  CONCLUSIONS
  Altered loading leads to mineralization of fibrocartilage and drives the lineage towards differentiation/maturation.
authors.affiliation: Division of Orthodontics, University of Connecticut Health Center, Farmington, United States of America.
authors.forename: Raman
authors.initials: R
authors.lastname: Kaul
authors.affiliation: Division of Orthodontics, University of Connecticut Health Center, Farmington, United States of America.
authors.forename: Mara H
authors.initials: MH
authors.lastname: O'Brien
authors.affiliation: Division of Orthodontics, University of Connecticut Health Center, Farmington, United States of America.
authors.forename: Eliane
authors.initials: E
authors.lastname: Dutra
authors.affiliation: Division of Orthodontics, University of Connecticut Health Center, Farmington, United States of America.
authors.forename: Alexandro
authors.initials: A
authors.lastname: Lima
authors.affiliation: Division of Orthodontics, Indiana University Purdue University Indianapolis, Indianapolis, United States of America.
authors.forename: Achint
authors.initials: A
authors.lastname: Utreja
authors.affiliation: Division of Orthodontics, University of Connecticut Health Center, Farmington, United States of America.
authors.forename: Sumit
authors.initials: S
authors.lastname: Yadav
mesh_terms: D000818:Animals; D002356:Cartilage / Q000473:pathology*; D002454:Cell Differentiation; D049109:Cell Proliferation; D002469:Cell Separation; D019902:Chondrocytes / Q000473:pathology; D049452:Green Fluorescent Proteins / Q000235:genetics; D008297:Male; D008335:Mandibular Condyle / Q000473:pathology*; D051379:Mice; D008822:Mice, Transgenic; D013312:Stress, Physiological; D055114:X-Ray Microtomography
chemical_list: D049452:Green Fluorescent Proteins