title: Mastication markedly affects mandibular condylar cartilage growth, gene expression, and morphology.
abstract: BACKGROUND
  Mandibular growth is believed to be strongly related to mastication. Furthermore, mandibular condylar cartilage is known to be derived from neural crest cells. We examined whether the degree of chewing affects condylar cartilage growth of the mandible.
  
  
  METHODS
  Mice were fed diets with varying hardness. Genes specific to neural crest-derived cells were measured by real-time polymerase chain reaction to compare the expression changes between the mandibular and tibia cartilages. The mandibular condylar cartilage was then evaluated histologically, and proliferation was evaluated using proliferating cell nuclear antigen. Immunostaining was conducted for osteopontin, type X collagen, and Musashi1, and real-time polymerase chain reaction was used to assess the expression levels of osteopontin and type X collagen.
  
  
  RESULTS
  Markers including P75, Wnt-1, Musashi1, and Nestin were upregulated in the mandibular condylar cartilage as compared with the tibial cartilage. Histologic assessment of the mandibular cartilage showed that the hypertrophic chondrocyte zone was statistically significantly thicker in mice fed a hard diet. Chondrocyte proliferation and Musashi1 expression were lower in mice fed a hard diet. After 4 weeks, numerous osteopontin and type X collagen-positive cells were observed in mice fed a mixed diet.
  
  
  CONCLUSIONS
  Mastication affects the balance between differentiation and proliferation in the mandibular condylar cartilage. This phenomenon might be attributed to the presence of neural crest-derived cells.
authors.affiliation: Postgraduate researcher, Department of Orthodontics, School of Dentistry, Showa University, Tokyo, Japan.
authors.forename: Akiko
authors.initials: A
authors.lastname: Enomoto
authors.affiliation: Lecturer, Department of Orthodontics, School of Dentistry, Showa University, Tokyo, Japan. Electronic address: junwata2000@ybb.ne.jp.
authors.forename: Junichi
authors.initials: J
authors.lastname: Watahiki
authors.affiliation: Postgraduate researcher, Department of Orthodontics, School of Dentistry, Showa University, Tokyo, Japan.
authors.forename: Tomoki
authors.initials: T
authors.lastname: Nampo
authors.affiliation: Lecturer, Dapartment of Oral Pathology, School of Dentistry, Showa University, Tokyo, Japan.
authors.forename: Tarou
authors.initials: T
authors.lastname: Irie
authors.affiliation: Assistant lecturer, Department of Orthodontics, School of Dentistry, Showa University, Tokyo, Japan.
authors.forename: Yuuta
authors.initials: Y
authors.lastname: Ichikawa
authors.affiliation: Professor, Department of Oral Pathology, School of Dentistry, Showa University, Tokyo, Japan.
authors.forename: Tetsuhiko
authors.initials: T
authors.lastname: Tachikawa
authors.affiliation: Professor, Department of Orthodontics, School of Dentistry, Showa University, Tokyo, Japan.
authors.forename: Koutaro
authors.initials: K
authors.lastname: Maki
mesh_terms: D000821:Animal Feed / Q000145:classification; D000818:Animals; D002358:Cartilage, Articular / Q000033:anatomy & histology / Q000254:growth & development*; D002454:Cell Differentiation / Q000235:genetics; D049109:Cell Proliferation; D019902:Chondrocytes / Q000166:cytology; D024121:Collagen Type X / Q000032:analysis; D015870:Gene Expression / Q000235:genetics; D006244:Hardness; D008297:Male; D008335:Mandibular Condyle / Q000033:anatomy & histology / Q000254:growth & development*; D008409:Mastication / Q000235:genetics*; D008592:Menisci, Tibial / Q000033:anatomy & histology / Q000254:growth & development; D051379:Mice; D009419:Nerve Tissue Proteins / Q000032:analysis; D064231:Nestin / Q000032:analysis; D009432:Neural Crest / Q000166:cytology / Q000378:metabolism; D053495:Osteopontin / Q000032:analysis; D018809:Proliferating Cell Nuclear Antigen / Q000032:analysis; D016601:RNA-Binding Proteins / Q000032:analysis; D011897:Random Allocation; D060888:Real-Time Polymerase Chain Reaction; D017475:Receptors, Nerve Growth Factor / Q000032:analysis; D013997:Time Factors; D015854:Up-Regulation; D051155:Wnt1 Protein / Q000032:analysis
chemical_list: D024121:Collagen Type X; C104786:Msi1h protein, mouse; D009419:Nerve Tissue Proteins; C577485:Nes protein, mouse; D064231:Nestin; D018809:Proliferating Cell Nuclear Antigen; D016601:RNA-Binding Proteins; D017475:Receptors, Nerve Growth Factor; C506897:Spp1 protein, rat; C517634:Ngfr protein, mouse; D051155:Wnt1 Protein; C495246:Wnt1 protein, mouse; D053495:Osteopontin