Urokinase Plasminogen Activator System Expression in chondrocytes after anterior disc displacement

Objectives: To investigate the roles of fibrinolytic enzymes (uPA/PAI-1) in the remodelling in condylar cartilage after disc displacement. Methods: The animal model of anterior disc displacement was established in 24 rabbits. In situ hybridization technique was used to analyzed the mRNA expression of uPA and PAI-1 in condyle chondrocytes. Results: uPA and PAI-1 were coexpressed weakly in chondrocytes from transition zone to hypertrophic zone and mineralized zone, while no hybridizing signals were showed in proliferative zone and fibrial zone. After disc displacement, uPA and PAI-1 mRNA expression increased in 4 days post-operation, especially in the hypertrophic zone and mineralized zone. There were hybridizing signals in proliferative zone in 4 weeks post-operation. After 4 weeks, the expression began to recover and reached near normal level in 12 weeks. Conclusions: There finding suggest that uPA system is concerned with the remodelling in condylar cartilage after disc displacement.