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 release from equine articular cartilage explant cultures.

DESIGN

Equine articular cartilage explants were maintained in vitro for 7 days in the presence of 0 (control), 1, 10, or 100 ng of rhBMP-2/ml. Synthesis and release of GAG were assessed as measures of production and degradation of the extracellular matrix, respectively.

ANIMALS

6 horses (age range, 2 to 25 years old) without clinically detectable musculoskeletal abnormalities.

PROCEDURE

Rate of synthesis of GAG was assessed by incorporation of [36S]sulfate during the final 24 hours of the 7-day incubation 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 incubation with 100 ng of rhBMP-2/ml. There was a significant (P = 0.05) decrease in GAG synthesis in explants from only 2 of the 6 horses at the same concentration of rhBMP-2. There was no significant age correlation between responsive and nonresponsive horses.

CONCLUSIONS

A concentration of 100 ng of rhBMP-2/ml stimulates GAG release from explant cultures of equine articular cartilage. The data suggest that bone morphogenetic proteins may be potential regulators of equine cartilage degradation and repair.

CLINICAL RELEVANCE

Surgical procedures that damage subchondral bone may stimulate generation of improved cartilage-like tissue. It is, therefore, crucial to understand how bone-derived factors may influence cartilage metabolism in horses.