To study the expression of urokinase-type plasminogen activator (uPA) and its receptor (uPAR) in the synovial tissures, and the significance of uPA and uPAR in degradation of extracellular matrices in osteoarthritis (OA), then analyse the possible relationship between uPA and uPAR.
Immunohistochemical analysis technique was used to detect uPA and uPAR protein expression and distribution in synovial tissues in 26 OA patients and 10 mormal individuals.
Positive staining of uPA and uPAR protein were detected in 19 cases in the 26 OA samples (73%), while only 2 positive cases were seen in the 10 mormal tissues (20%). The expression rate of uPA protein was markedly higher in OA than in the normal (P < 0.01). The expression of uPAR was seen in 14 cases in all 26 OA samples (54.6%), while there was only one case in 10 normal samples (10%), the positive rate was significantly higher in OA than in normal samples (P < 0.05). Positive expression of uPA and uPAR proteins were found in synovial lining cells, mononuclear cells, macrophage-like cells and endothelial cells. Using the correction analysis, we found a positive correlation between uPA and uPAR reactivity in the synovial tissues in OA (r = 0.920, P < 0.01).
The high expression of uPA and uPAR protein in OA synovial tissues indicate that the uPA system may play an important role in the process of synovitis and degradation of OA cartilage extracellular matrices. In the pathologic process of OA, uPA and uPAR coordinate each other, lead to the genesis and development of OA cartilage degradation.