HYALURONIC-ACID SUPPRESSES FIBRONECTIN FRAGMENT MEDIATED CARTILAGE CHONDROLYSIS .1. IN-VITRO

A commercial preparation of 800-kDa hyaluronic acid (HA), (ARTZ from S eikagaku, Inc.), has been used as a therapeutic intervention in the tr eatment of osteoarthritis (OA). We tested the effect of this HA form, HA/800, in an in vitro cartilage chondrolytic system in which a specif ic amino-terminal 29-kDa fragment of fibronectin (Fn-f) penetrates car tilage tissue to activate chondrocytes to amplify two major chondrolyt ic activities: suppression of proteoglycan (PG) synthesis and inductio n of matrix metalloproteinases. We report that HA/800 did not block da mage by Fn-f in serum free cartilage cultures. However, HA/800 was eff ective in blocking the ability of 100 nm Fn-f to cause the degradation and release of half of the total cartilage PG from cartilage in 10% s erum/DMEM cultures. While the Fn-f caused a half-time for PG release o f 3 days, continuous exposure to 0.1 or 1 mg/ml HA/800 slowed the half -time to 12 days. Further, a single 1 day pre-incubation with 0.1 or 1 mg/ml HA/800 was sufficient to decrease the half-time of 100 nm Fn-f mediated PG; depletion to 7 and 12 days, respectively. HA/800 complete ly blocked the effect of 10 nm Fn-f. Blocking of Fn-f-mediated cartila ge PG; depletion was associated with a decreased concentration of Fn-f on the superficial cartilage surface and decreased penetration into t he cultured cartilage tissue. Further, the two major chondrolytic acti vities of the Fn-f, suppression of synthesis of PG and enhanced releas e of stromelysin-1, were suppressed by HA/800. HA/800 also partially r estored PG in cartilage first damaged with the Fn-f. We conclude that HA/800 slows Fn-f-mediated cartilage chondrolysis in vitro and has som e reparative potential. The damage blocking activity appears to be ass ociated with the ability of HA/800 to block penetration of the Fn-f, r ather than with direct effects on cartilage tissue.