Cartilage and bone biological markers in the synovial fluid of osteoarthritic patients after hyaluronan injections in the knee.

OBJECTIVE: To evaluate synovial fluid levels of cartilage and bone biological markers after repetitive intra-articular injections of sodium hyaluronate (HA) in knee osteoarthritis (OA) patients.

METHODS: Twenty patients with knee OA were evaluated before and after 5 weekly injections of HA. To study cartilage and bone biological markers, synovial fluid and urine samples were collected simultaneously with the first (FI=week 0) and before the last injection (LI=week 4) of HA. Not commercially available markers (cartilage oligomeric matrix protein (COMP), proteoglycan monomers and cyanogen bromide peptide 11 of the type II collagen chains (alpha (II) CA11B)) were determined by an indirect inhibition ELISA developed and standardized in our laboratory.

RESULTS: We found a significant reduction in levels of proteoglycan monomers (30+/-16 vs. 22+/-10 microg/ml, p<0.05), an increase in COMP concentration (2.9+/-0.9 vs. 3.6+/-0.9 microg/ml, p<0.05) and osteocalcin (BGP) levels (8.7+/-8 vs. 11.9+/-9 ng/ml, p<0.05). No significant changes were observed in the levels of alpha (II)CB11B), metalloproteinase-1 (MMP-1) or pyridinium cross-link/creatinine (Pyr/Cr).

CONCLUSIONS: HA could elicit an indirect response on the cartilage and bone metabolism due to the increased overuse of the joint caused by the analgesic effect of HA. However, a direct HA action on the metabolism of chondrocytes must not be ruled out.