Condrocyte Apoptosis in Rabbit TMJ following Anterior Disk Displacement

Objectives:Temporomandibular joint anterior disk displacement (ADD) was one kind of temporomandibular joint disorders (TMD). So far, there were arguments about whether temporomandibular joint disk displacement was pathologic. In this experiment, we studied articular histological changes, and chondrocytes apoptosis to investment the role of apoptosis in condyle adaptive remodeling. Materials and Methods:To study the signaling transfer pathway of chondrocytes apoptosis after ADD, we investigated the expression paterns of Fas,caspase-8 by western blotting. To study the adaptive changes in temporomandibular joint and the role of apoptosis in remodeling following anterior disk displacement, we invested histological changes in TMJ; furthermore, we studied In situ detection of apoptosis in TMJ by TUNEL. Results:In the experiment of Fas induced chondroocyte apoptosis following ADD, it was found that Fas,Caspase-8 expressed increasingly after ADD within 4 weeks. In the adaptive remodeling studying following anterior disk displacement, visual observation showed in the experimental rabbits, there were minor histological changes in one week after ADD, but after 2-4 weeks, the histological changes in TMJs were significant, including: cartilage became thinner with deranged chongdrocytes; disk collagen fibers arrayed disruptedly; synoviocytes on the surface layer exfoliated; chondrocyte-like cells were found in bilaminar zone (BZ), tipical cartilage could be found after 6 weeks on tne surface of or inside of the BZ; there was angiogenesis in BZ. There were few apoptotic cells in TMJ condyle and BZ of control and sham-operated rabbits. Focally arranged apoptotic cells appeared, especially in synovium after 1 week following ADD. Apoptotic cell increased largely in condyle and BZ after 2-4 weeks. Conclusions:The data suggest that chondrocyte apoptosis increased following ADD. Apoptosis might play an important role in condyle remodeling following ADD.