LOADING-INDUCED CHANGES IN SYNOVIAL-FLUID AFFECT CARTILAGE METABOLISM

The purpose of this study was to determine whether changes in the syno vial fluid (SF) induced by in vivo loading can induce an alteration in the metabolic activity of chondrocytes in vitro. Therefore, SF was co llected from ponies after a period of box rest and after they had exer cise for a week. Normal, unloaded articular cartilage explants were cu ltured in 20% solutions of these SFs for 4 days and chondrocyte activi ty was determined by glycosaminoglycan (GAG) turnover. In explants cul tured in post-exercise SF, GAG synthesis was enhanced and GAG release was diminished when compared to cultures in pre-exercise SF. SF analys is showed that levels of insulin-like growth factors (IGF-I and IGF-II ) tended to be higher in post-exercise SF, while no differences were f ound in metalloproteinase activity, hyaluronic acid and protein concen trations. This study showed that anabolic effects of joint loading on cartilage are, at least partially, mediated by alterations in the SF.