The role of mandibular condylar cartilage in articular cartilage repair.

The articular hyaline cartilage of synovial joints has a very limited capacity for repair after injury. In contrast, the mandibular condylar cartilage of the temporomandibular joint possesses as intrinsic potential for regeneration. This study aimed to test the hypothesis that cultured allografts of mandibular condylar cartilage could be used to promote biological repair of injured orthotopic joint surfaces. Using a primate animal model, cultures of mandibular condylar cartilage cells were grafted into surgically created defects in a recipient hyaline cartilage joint surface. Articular wound healing was assessed macroscopically and histologically over a postoperative period of 52 weeks. Mandibular condylar cartilage cells scheduled for allogenous transplantation were initially characterised in vitro. Expansion of primary colonies in organ culture provided the allogenic cellular material for in vivo grafting. Grafting of osteochondral articular wounds with 5-week cultures of mandibular cartilage cells led to wound regeneration with complete reconstitution of articular surface continuity by 52 weeks. There was novel synthesis of cartilage collagens and sulphated glycosaminoglycans within the repair tissue and no evidence of immunological rejection. Healing of grafted defects was thought to occur by a combination of donor cell proliferation and ingress of host mesenchymal cells. In contrast, grafted control wounds underwent largely fibrous repair with incomplete articular regeneration. In conclusion, transplanted allografts of cultured mandibular condylar cartilage appeared to have the ability, in this primate model, to promote cartilaginous repair and regeneration of orthotopic articular wounds.