Type II collagen and aggrecan mRNA expression by in situ hybridization in rabbit temporomandibular joint posterior attachment following disc displacement

Pathological changes and mRNA expression were studied in the posterior attachment of 40 adult Japanese white rabbits. The right temporomandibular joints of 28 rabbits were subjected to surgical disc displacement. Joints were studied by histochemistry and in situ hybridization. The collagen in the posterior attachment became dense, especially near the posterior band of the disc. Chondrocytes were found not only in the disc but also in the posterior attachment. Sometimes cartilage formation was seen. Type II collagen mRNA expression was first detected in the posterior attachment 4 days postoperatively and became progressively stronger with time. Aggrecan expression in the posterior attachment decreased at first, then increased gradually. It was concluded that, in the temporomandibular joint, chondrocytes appear in the posterior attachment as a result of biomechanical stimuli and the attachment becomes fibrocartilaginous following disc displacement.