Articular cartilage of the temporomandibular joint: can it regenerate?

Clinical evidence and previous experimental animal work suggest that mandibular condylar cartilage shows the capacity for repair, after trauma or degeneration, that can reconstitute a functional articular surface; a facility not shared by other synovial joints. This study aims to test the regenerative capability of condylar cartilage in the repair of standardised full-thickness articular defects, and thereby to test the hypothesis that the healed wounds comprise tissues identical in form and composition to those of similar, but uninjured areas. Articular defects were produced at open arthrotomy of the temporomandibular joints in the young adult cotton eared marmoset. After healing periods of between 3 days and 1 year, repairing wounds were examined using histological, autoradiographic and immunocytochemical methods in an attempt to identify tissue architecture, cell proliferation and cartilage matrix components. The results showed reconstitution of all tissue elements of condylar cartilage within 6 months of injury. Glycosaminoglycans reformed at an early stage and appeared to be associated with type I collagen fibrillogenesis. Subsequently, type II collagen and aggregated proteoglycans accumulated from 8 weeks postoperatively, coinciding with organisation of the cell layers of condylar cartilage. The reformed tissue was maintained intact for the period studied (up to 1 year).