OBJECTIVETo investigate the effect of anterior disc displacement on the expression of urokinase plasminogen activator and its inhibitor-1 (uPA/PAI-1) in synovial tissues.

METHODSForty Japanese white rabbits were used in this study. The animals were killed at 4 days, 1, 2, 4, 8 and 12 weeks postoperatively, respectively. In situ hybridization technology was applied to detect the expression of uPA/PAI-1 mRNA in synovial membrane.

RESULTSIn normal synovial tissues, synovial lining cells and a few fibrosblasts with mild positive staining were occasionally seen. More synovial lining cells and fibrosblasts with moderate postive signals were found 1 week after operation. Since then, the degree of staining for uPA/PAI-1 increased gradually. By the end of 12 weeks postoperatively, strong signals of uPA/PAI-1 mRNA were detected.

CONCLUSIONThere is a harmonized uPA/PAI-1 system existing in synovial tissues. The high expression of uPA and PAI-1 mRNA in synovial tissues indicates that the uPA/PAI-1 system may play an important role in the process of synovitis resulted from anterior disc displacement.