title: Cell type and distribution in the porcine temporomandibular joint disc.
abstract: OBJECTIVE
  Surprisingly little is known about the cellular composition of the temporomandibular joint (TMJ) disc, which is a crucial piece of the puzzle in tissue engineering efforts. Toward this end, cell types were identified and quantified regionally in the TMJ disc.
  
  
  METHODS
  Porcine TMJ discs were examined by histology, electron microscopy, and immunohistochemistry. Histology consisted of hematoxylin and eosin staining to identify regional variation of cell type and cell numbers. Transmission electron microscopy was used to elucidate differences in organelle content and pericellular matrix between TMJ disc cells and chondrocytes from hyaline cartilage. Immunohistochemistry was used to assess the presence of smooth and skeletal muscle character in the TMJ disc.
  
  
  RESULTS
  The overall ratio of fibroblasts to chondrocyte-like cells in the TMJ disc was approximately 2.35 to 1, with the highest relative number of chondrocyte-like cells in the intermediate zone. Electron microscopy revealed distinct differences between TMJ disc chondrocyte-like cells and chondrocytes from hyaline cartilage with respect to organelles and the pericellular region. Immunostaining identified smooth muscle in the form of vessels, which were most prominent in the anterior band. Skeletal muscle was not observed.
  
  
  CONCLUSIONS
  The cells of the TMJ disc are distinctly different from cells of hyaline cartilage, and consequently should not be referred to as chondrocytes. TMJ disc cells are comprised of heterogeneously distributed subpopulations, with fibroblasts predominating over fibrochondrocytes.
authors.affiliation: Department of Chemical and Petroleum Engineering, University of Kansas, Lawrence, KS 66045-7609, USA.
authors.forename: Michael S
authors.initials: MS
authors.lastname: Detamore
authors.forename: Jay N
authors.initials: JN
authors.lastname: Hegde
authors.forename: Rohan R
authors.initials: RR
authors.lastname: Wagle
authors.forename: Alejandro J
authors.initials: AJ
authors.lastname: Almarza
authors.forename: Dina
authors.initials: D
authors.lastname: Montufar-Solis
authors.forename: P Jackie
authors.initials: PJ
authors.lastname: Duke
authors.forename: Kyriacos A
authors.initials: KA
authors.lastname: Athanasiou
mesh_terms: D000818:Animals; D002452:Cell Count; D019902:Chondrocytes / Q000648:ultrastructure; D005260:Female; D005347:Fibroblasts / Q000648:ultrastructure; D051457:Hyaline Cartilage / Q000166:cytology; D017348:Microscopy, Electron, Scanning Transmission; D013552:Swine; D019224:Temporomandibular Joint Disc / Q000166:cytology* / Q000648:ultrastructure