REGULATION OF GLYCOSAMINOGLYCAN METABOLISM BY BONE MORPHOGENETIC PROTEIN-2 IN EQUINE CARTILAGE EXPLANT CULTURES

Objective-To investigate whether recombinant human bone morphogenetic protein-2 (rhBMP-2) regulates glycosaminoglycan (GAG) synthesis and re lease from equine articular cartilage explant cultures. Design-Equine articular cartilage explants were maintained in vitro for 7 days in th e presence of 0 (control), 1, 10, or 100 ng of rhBMP-2/ml. Synthesis a nd release of GAG were assessed as measures of production and degradat ion of the extracellular matrix, respectively. Animals-6 horses (age r ange, 2 to 25 years old) without clinically detectable musculoskeletal abnormalities. Procedure-Rate of synthesis of GAG was assessed by inc orporation of [S-35]sulfate during the final 24 hours of the 7-day inc ubation period. Release of GAG was assessed on days 3, 6, and 7, using 1,9-dimethylmethylene blue. Results-Explants from all 6 horses had a significant (P = 0.05) increase in release of GAG in response to incub ation with 100 ng of rhBMP-2/ml. There was a significant (P = 0.05) de crease in GAG synthesis in explants from only 2 of the 6 horses at the same concentration of rhBMP-2. There was no significant age correlati on between responsive and nonresponsive horses. Conclusions-A concentr ation of 100 ng of rhBMP-2/ml stimulates GAG release from explant cult ures of equine articular cartilage. The data suggest that bone morphog enetic proteins may be potential regulators of equine cartilage degrad ation and repair. Clinical Relevance-Surgical procedures that damage s ubchondral bone may stimulate generation of improved cartilage-like ti ssue. It is, therefore, crucial to understand how bone-derived factors may influence cartilage metabolism in horses.