Identification of matrix metalloproteinases (MMPs) in synovial fluid from patients with temporomandibular disorder

Proteolytic enzymes with gelatinolytic activity in the synovial fluid (SF) of temporomandibular joint (TMJ) arthropathies were assayed by gelatin-impr egnated gel enzymography. SF samples were collected from 10 TMJs in patient s with closed lock (CL) condition and 5 TMJs from asymptomatic healthy volu nteers. Two proteinases with gelatinolytic activities at 92 kDa and 72 kDa were detected in both the normal and the diseased TMJs. Also detected were weak bands at molecular weights of 83 kDa and 66 kDa. All of these proteina se activities were inhibited by EDTA and tissue inhibitor of metalloprotein ases (TIMP), required Ca2+ for activation, and were detected with gelatin b ut not casein as substrate, suggesting that these enzymes were matrix metal loproteinases (MMPs). The 72 kDa and 66 kDa bands further reacted with anti -MMP-2 antibody by Western blot analysis, and the proteinases in the TMJ-SF could cleave type IV collagen in vitro without any activation. These four activities identified by enzymography were, therefore, identified as 92 kDa -gelatinase (proMMP-9), 83 kDa-gelatinase (active MMP-9), 72 kDa-gelatinase (proMMP-2) and 66 kDa-gelatinase (active MMP-2). Densitometric analyses of these bands revealed higher levels of the active form of MMP-9 in the CL p atients compared to controls. These findings suggest that MMP-2 and -9 coul d be dominant proteinases in the TMJ-SF and possibly reflect TMJ pathology.