Acid hydrolase activity following allografting

The synovium of dogs receiving an osteochondral allograft of the distal femur has similar characteristics to a rheumatoid synovium. Since it is generally believed that the cartilage destruction in rheumatoid arthritis is related to the release of hydrolases from lysosomes, the following study was performed to determine whether a similar phenomenon is responsible for the destruction of transplanted articular cartilage. Host synovium revealed an almost threefold increase in acid phosphatase activity at 26 and 52 weeks after transplantation when compared to controls. Electron microscopy studies showed a marked increase in the number of lysosomes seen in the type A synovial cells at 26 weeks, degradation of the cartilage matrix, and the presence of enzyme reaction product when treated for cytochemical demonstration of acid phosphatase activity. It is concluded that the host synovium destroys the allograft by the release of lysosomal enzymes.