FIGURE 10.

Schematic diagram of the proposed development process of THO-TMJ. Trauma in the TMJ region stimulates residual and injured chondrocytes to release IGF1/TGFβ2 when there is no articular disc (and under pressure). IGF1/TGFβ2 may induce blood endothelial cells and muscle-derived cells to differentiate into chondrocytes, followed by heterotopic ossification through an endochondral ossification process. Finally, heterotopic ossification may lead to TMJ ankylosis in the clinic. “?” indicates that precursor cells may also directly differentiate into osteoblasts, but this needs to be further investigated.