Expression of matrix metalloproteinase-2 in osteoarthritic fibrocartilage from human mandibular condyle.

Matrix metalloproteinase (MMP)-2 is expressed in osteoarthritic cartilage and synovial fluid and is thought to be involved in the degradation of cartilage extracellular matrix. However, MMP-2 expression and osteoarthritic changes in internal derangement of the temporomandibular joint are unknown. In the present study, we have examined the histological relationship between osteoarthritic changes on articular cartilage with or without articular disc perforation, and MMP-2 expression, in 85 mandibular condyles from cadavers. The expression and tissue immunolocalization of MMP-2 in fibrocartilages from these condyles was examined histochemically. The Mankin grade of histological criteria for specimens with disc perforation was significantly higher than that of specimens without perforation. MMP-2 immunostaining was positive in the cytoplasm of chondrocytes and in their surrounding matrix. There was a linear correlation between MMP-2-positive cell rates and Mankin grade. Our data suggest that MMP-2 plays an important role in fibrocartilage degradation in internal derangement of the temporomandibular joint.

Histological changes in the rabbit condyle following posterolateral disk perforation.

PURPOSE: To examine changes in condylar cartilage following perforation in the posterolateral region of the articular disk of the craniomandibular joint of a rabbit. MATERIAL AND METHODS: The circular perforation in the left joint of 25 female Japanese white rabbits measured precisely one-sixteenth of a disk. Histological examination, including the immunohistochemical proliferating cell nuclear antigen (PCNA) procedure, was performed on separate sets of five rabbits each 2, 4, 8, 12, and 24 weeks postoperatively. RESULTS: Microscopic examination revealed hypertrophy of the condylar cartilage with osteophyte formation up to 8 weeks after perforation. Proliferative activity then decreased near the condylar surface as the perforation flattened. Twenty-four weeks postoperatively, the condylar surface was found to be fibrous and flattened. Positive PCNA results in cartilage cells indicated proliferation following disk perforation which peaked in the 4th week and then decreased. CONCLUSION: Disk perforation was followed initially by hypertrophy of condylar cartilage, and later by degeneration of the condylar surface. Although osteoarthritic cartilage was found 24 weeks after perforation, degeneration decreased over time. This suggests that remodelling took place after the perforation.

Histologic evaluation of auricular cartilage grafts after discectomy in the rabbit craniomandibular joint.

PURPOSE: The clinical use of auricular cartilage grafting after discectomy has been reported as a treatment in the terminal stage of internal derangement of the temporomandibular joint (TMJ). Although the occurrence of fibrous adhesions has been observed in such grafted joints, the exact tissue reaction to the graft is still not understood. The purpose of this study was to evaluate the histologic changes after discectomy and auricular cartilage grafting in the rabbit craniomandibular joint (CMJ). MATERIALS AND METHODS: Unilateral discectomy of the left CMJ was performed in 28 Japanese white rabbits. Auricular cartilage harvested from the ipsilateral ear was grafted as a disc replacement in 14 animals (Group C), and the other 14 underwent wound closure immediately after discectomy (Group B). Two other rabbits (Group A) served as nonsurgically treated controls. Two rabbits from each experimental group were killed at 2, 4, 6, 8, 10, 12, and 24 weeks postoperatively. Microscopic observation of the specimens was performed in the parasaggital plane. RESULTS: Complete resorption of the cartilage layer on the articular surface was observed within 4 weeks postoperatively in group B. Regeneration of a fibrous cartilage layer was observed in this group after 6 weeks, but the postoperative degenerative changes were so severe that the surface of the condyle and eminence was flattened. In contrast, the degenerative changes were milder in group C, although the grafted cartilage showed perforation and fragmentation from the sixth postoperative week onward. The condylar shape and cartilage layer were well preserved at all times. CONCLUSIONS: These results suggest that the structure and function of the condyle may be preserved by auricular cartilage grafting after discectomy. However, the problems of adhesion and fragmentation need to be addressed.