MATRIX LOSS AND SYNTHESIS FOLLOWING A SINGLE IMPACT LOAD ON ARTICULAR-CARTILAGE IN-VITRO

Articular cartilage biopsies were subjected to a single impact load an d the metabolic response of the chondrocytes investigated using radiol abelled precursors for protein ([H-3]leucine) and glycosaminoglycan ([ S-35]sulfate). The severity of the impact was controlled by using diff erent masses and drop heights in a purpose built drop tower. Loss of m atrix components was studied by prelabelling prior to loading, the pos sible repair response by pulse labelling at defined intervals after lo ading. There was an increase in the loss of both labels from the tissu e with increasing severity of impact though the patterns of loss were different. Only 25%-40% of the sulfate was lost over a two week period and the loss increased with the severity of impact. This contrasted w ith 60% of the leucine being lost over the same period independently o f loading. In addition to the loss of synthetic activity caused by cel l death, there was a suppression of incorporation immediately followin g loading. This eventually recovered and increased above control value s but the recovery time appeared to depend on the severity of the impa ct. These results provide preliminary evidence for a repair response.