Interleukin-1 reversibly inhibits the synthesis of biglycan and decorin in intact articular cartilage in culture.

OBJECTIVE To study the effect of interleukin-1 (IL-1) on the synthesis of proteoglycans biglycan (DSPG-I) and decorin (DSPG-II) in intact bovine articular cartilage. METHODS Cartilage bearing sesamoid bones from the metacarpophalangeal joint were cultured with 10 ng/ml IL-1 for 2 days and labelled with [35S] sulfate. One sesamoid bone from each animal had been labelled ex vivo. The remaining 2 were cultured with IL-1 and allowed to recover in control medium before labelling. Control cultures were maintained in medium without IL-1 and labelled concurrently with the experimental series. The dermatan sulfate proteoglycans were purified from 4 M guanidinium chloride extracts of the cartilage by gel filtration on Sepharose CL-2B and CL-4B, on which they appeared as a single peak. Biglycan and decorin were separated by sodium dodecyl sulfide polyacrylamide gel electrophoresis in high salt. Individual lanes from the gel were cut in slices, which were dissolved and counted for radioactivity. RESULTS Ex vivo, biglycan accounted for 4% and decorin for 2% of total incorporated sulfate. IL-1 reduced the synthesis of biglycan to 77% of the level of cultured controls and that of decorin to 73%. The synthesis of both proteoglycans returned to the control levels when the IL-1 was removed. IL-1 (10 ng/ml, 2 days) had no significant effect on total proteoglycan synthesis. CONCLUSION The inhibition of synthesis of biglycan and decorin by IL-1 might be important in the pathophysiology of cartilage destruction in rheumatic diseases.