To study the distribution and expression of type-1 plasminogen activator inhibitor (PAI-1) and type-2 plasminogen activator inhibitor (PAI-2) in synovial tissue from rheumatoid arthritis(RA) and measure the antigen levels and activity in synovial fluid and plasma of patients with RA.
Immunohistochemical analysis was used to detect PAI-1 and PAI-2 expression and distribution in synovial tissue from 24 RA patients, 18 osteoarthritis (OA) patients and 6 normal subjects. PAI-1 and PAI-2 antigen concentration and activity were determined with ELISA sandwich method.
In RA patients, positive staining of PAI-1 and PAI-2 was seen respectively in all the 24 cases and 8 of the 24 cases; positive expression was distributed mainly in the synovial lining area. In OA patients, positive staining of PAI-1 was detected in 8 cases and its positive distribution was similar to that in RA. No PAI-2 positive staining was seen in all the OA cases. In 6 normal subjects with normal synovial tissue, the staining was negative. The concentration and activity of PAI-1 in RA synovial fluid(SF) were significantly higher than those in the plasma(P < 0.001 and P < 0.05). The concentration and activity of PAI-1 in the plasma of RA were also much higher than those in the plasma of OA(P < 0.05 and P < 0.0001) and healthy subjects(P < 0.0001 and P < 0.001). The concentration and activity of PAI-1 in SF and plasma of RA correlated positively.
The up-regulated expression of PAI-1 and PAI-2 and the concentration and activity of PAI-1 in SF and plasma were significantly higher in RA than those in OA and healthy subjects, suggesting PAI especially PAI-1 may play an important role in the pathogenesis of RA.