One-month-old male mice were divided into two groups. In group 1, condylar cartilage was partially removed in the right joint using a small scissors to induce ankylosis. In group 2, condylar cartilage was completely removed in the same right joint using a small scissors to induce ankylosis. The phenotypes were observed using gross observation, micro-computed tomography scans and histological examination.
The results revealed a great deal of ectopic cartilage and bone formation in the right periarticular region in all mice in group 1, whereas there was only a small amount of ectopic cartilage present in 26.7% of the mice in group 2. Additionally, there was stronger expression of FGF9 and weaker expression of OPN in the right temporomandibular joint region in group 2 at 7 days after surgery.
These results suggest that the injured cartilage, not the injured bone, plays a crucial role in the development of TTMJA. In addition, it offers a useful TTMJA animal model to study the molecular mechanisms of TTMJA based on the gene manipulation technology, such as gene knock-out and knock-in as well as transgenic or gene mutation.