Cyclic compression loaded on cartilage explants enhances the production of reactive oxygen species

Objective. Although mechanical forces are an essential factor in the regulation of cartilage metabolism, the precise mechanisms involved have not yet been determined. We previously demonstrated that mechanical forces on chondrocytes inhibited proteoglycan (PG) synthesis. We also demonstrated the induction of reactive oxygen species (ROS) is loaded on the chondrocytes. Our purpose was to determine the ROS induction with mechanical compression and its involvement in PG synthesis of cartilage slices. Methods. Bovine articular cartilage slices were subjected to cyclic compression loading. Synthesis of PG and ROS was measured using Na 2 [ 35 S]-SO 4 and a chemiluminescent probe, respectively. The induction of nitrotyrosine was determined using immunohistochemistry. Results. The synthesis of PG was significantly inhibited with 2.0 MPa of compression stress; 1 h of compression was sufficient to inhibit PG synthesis. The ROS inhibitor ebselen reversed the compression-inhibited synthesis of PG. Compression on the cartilage induced synthesis of ROS and the expression of nitrotyrosine. Conclusion. Mechanical compression at 2.0 MPa inhibited PG synthesis by cartilage explants. ROS were involved in this action.