Validation of a chemical osteoarthritis model in rabbit temporomandibular joint: a compliment to biomechanical models

To explore degenerative mechanisms occurring in the temporomandibular joint (TMJ), a chemical model of knee joint osteoarthritis using sodium mono-iodoacetate injection was transposed to the TMJ. Twelve New Zealand rabbits were used to document the effect of this drug on the TMJ. Eight rabbits underwent bilateral iodoacetate injection in the disco-condylar compartment while 4 served as controls. Rabbits were sacrificed at 10, 20, 30 and 40 days and joints studied by histology. Severity of the damage was time dependent and the use of iodoacetate allowed the observation, within a few weeks, of every osteoarthritic stage usually described in the literature. This study showed that the TMJ has a specific response to the degenerative process. This response was characterized by (i) thickening and fibrillation of the cartilage at the periphery of the lesion, tending to reduce mechanical stress in the lesional area and (ii) chondrocyte migration under areas where subchondral bone surface was locally destroyed. The extracellular matrix containing chondrocyte clusters and prechondrocytes dived around the bony defect and proceeded below the necrotic bone to promote the eviction of bony fragments into the joint cavity, pushing them up while the thickness of chondrocyte rows increased below. This could be interpreted as a repairing attempt due to the specific potential of fibrocartilage proliferative cells.