202 DYSREGULATION OF GLUCOSE TRANSPORT AND GLUT-1 PROTEIN IN OSTEOARTHRITIC CHONDROCYTES IN RESPONSE TO HIGH EXTRACELLULAR GLUCOSE

Methods: Opticin was extracted from normal and OA human cartilage using guanidinium chloride (4M) extraction and examined by Western blotting. Human MMP 1, -2, -3, -7, -8, -9 and ADAMTS-4, -5 proteolytic activities on opticin were analyzed on normal and OA cartilage extracts incubated for 0−24 hours Results: One of the emerging observations was that all MMPs and ADAMTS tested, except MMP-9, cleaved opticin in both normal and OA specimens. Interestingly, MMP-7 and -8 were the most effective, and degradation occurred as early as 15 minutes of incubation. At which time, degradation was almost complete for MMP-7, suggesting that this molecule is a preferential substrate for this enzyme. In contrast, MMP-1 was the least effective and degradation was noted after an incubation of 16 hours. The others enzymes showed degradation starting at about 2 hours. The degradation pattern, except for MMP-7 in which degradation appeared independent of the specimen types, was different between normal and OA. In general, the degradation pattern was slower in normal than in OA specimens, reflecting an increased sensitivity of opticin to degradation when the cartilage was damaged. Fragments were also detected, but the number and size differed depending on the protease. This indicates different digestion sites among the proteases. Surprisingly, MMP-1 and -2 generated different opticin degradation fragments when normal were compared to OA specimens. The different opticin protease cleavage sites are currently under study. Conclusions: We showed, for the first time, the ability of different MMP and ADAMTS to degrade opticin. As opticin may contribute to the structural stability of cartilage matrix, its cleavage may predispose cartilage to degradation. In vivo identification of the cleavage products may assist in an early detection of OA cartilage matrix degeneration.