Synthesis of type II collagen is decreased in cartilage cultured with interleukin 1 while the rate of intracellular degradation remains unchanged.

The effect of interleukin 1 (IL1) on the synthesis and degradation of collagen was examined in explants of cultured cartilage. IL1 induced a reversible, dose-dependent (10-100 pM) inhibition of type II collagen synthesis. The proportion of collagen produced decreased selectively from 7% to 1.2% of total protein after 72 h exposure to IL1 (100pM). There was no change in the rate of degradation of newly synthesized collagen. Analysis of newly synthesized material showed that the type II collagen synthesized in the presence of IL1 had the same characteristics as that extracted from unstimulated cartilage. The relative amounts of type II procollagen mRNA were estimated by Northern blot hybridization. The levels were decreased in cartilage cultured with IL1 to a similar extent as that seen for the type II collagen protein. Exposure to IL1 (10-350pM) for 3 days did not induce increased resorption of extracellular collagen in the cultured explants. These data demonstrate that decreased collagen production in cartilage exposed to IL1 is due primarily to decreased amounts of type II procollagen mRNA.