Objective: To evaluate the occurrence of gelatinase-B (matrix metalloproteinase 9, MMP-9) in synovial fluids (SF) of patients with arthritis to investigate the possible role of this neutral MMP in joint destruction.
Methods: In paired (series I) and unpaired SF (series II) we examined the occurrence of gelatinase-B, prostromelysin-1, and urokinase-type plasminogen activator (u-PA).
Results: In the paired SF a parallelism between the presence of activated gelatinase-B and the local arthritis activity scores of the knees was observed. Activated gelatinase-B correlated well with the presence of stromelysin-1 and u-PA, 2 enzymes probably involved in the activation process of gelatinase-B. In the 2nd series, activated gelatinase-B was found in 56 SF samples, whereas 82 samples did not exhibit activated gelatinase-B. The SF samples with the activated form of gelatinase-B showed a significantly higher ability to induce permeability changes in cultured monolayers of human endothelial cells, had more myeloperoxidase activity--secreted by infiltrated leukocytes--and had higher u-PA antigen concentrations, compared to SF samples without the activated form of gelatinase-B.
Conclusion: Our data suggest that the presence of gelatinase-B is a reflection of the inflammatory condition of the joints of patients with arthritis, and that the activation of gelatinase-B in the joints, which may occur in a u-PA/plasmin dependent and/or a stromelysin dependent way, contributes to the progression of arthritis.