Juvenile porcine temporomandibular joint: Three different cartilaginous structures?
OBJECTIVE
The temporomandibular joint (TMJ) consists of three cartilaginous structures: the fossa, disc, and condyle. In juvenile idiopathic arthritis (JIA), inflammation of the TMJ leads to destruction of the condyle, but not of the fossa or the disc. Such a different effect of inflammation might be related to differences in matrix composition of the cartilaginous structures.


METHODS
The matrix composition of the three TMJ structures was analyzed in juvenile porcine samples and in an in vitro system of cells isolated from each anatomical structure embedded in 3% agarose gels.


RESULTS
The matrix of all three anatomical structures of the TMJ contained collagen type I and its gene expression was maintained after isolation. The condyle and the fossa stained positive for collagen type II and proteoglycans, but the condyle contained considerably more collagen type II and proteoglycans than the fossa. The disc contained neither collagen type II protein nor expression of its gene, and the disc did not stain positive for proteoglycans. Aggrecan gene expression was lower in the disc compared to condyle and fossa cell-isolates. In general, the cell-isolates in vitro closely mimicked the characteristic features found in the tissue.


CONCLUSIONS
The collagen type II content of the condyle clearly distinguished this cartilaginous structure from the disc and fossa. Since autoimmunity against collagen type II is associated with JIA, the relatively abundant presence of this type of collagen in the condyle might provide an explanation why primarily this cartilaginous structure of the TMJ is affected in JIA patients.
Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands.
Hessam
H
Tabeian
Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands.
Astrid D
AD
Bakker
Department of Periodontology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands. Electronic address: teun.devries@acta.nl.
Teun J
TJ
de Vries
Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands.
Behrouz
B
Zandieh-Doulabi
Department of Oral Kinesiology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands.
Frank
F
Lobbezoo
Department of Oral Cell Biology, Academic Centre for Dentistry Amsterdam (ACTA), University of Amsterdam and VU University Amsterdam, MOVE Research Institute Amsterdam, Amsterdam, The Netherlands.
Vincent
V
Everts
D000818:Animals; D002478:Cells, Cultured; D024042:Collagen Type I / Q000378:metabolism*; D024043:Collagen Type II / Q000378:metabolism*; D007150:Immunohistochemistry; D008335:Mandibular Condyle / Q000378:metabolism; D010641:Phenotype; D011509:Proteoglycans / Q000378:metabolism*; D060888:Real-Time Polymerase Chain Reaction; D013552:Swine; D013704:Temporomandibular Joint / Q000378:metabolism*; D019224:Temporomandibular Joint Disc / Q000378:metabolism
D024042:Collagen Type I; D024043:Collagen Type II; D011509:Proteoglycans
Articular disc; In vitro; Juvenile idiopathic arthritis; Mandibular condyle; Mandibular fossa