OXYGEN SCAVENGERS IN SIMPLE BONE-CYSTS

Simple bone cyst is a fluid-filled, cystic lesion that occurs in the m etaphysis of the long bones of children and adolescents. The chemical characteristics of the cyst fluid of the simple bone cyst are similar to those of serum, The existence of the cyst fluid itself may be an ob stacle to cyst healing, and, in part, this may be because the cyst flu id contains bone destructive factors. Oxygen-free radicals, which are cytotoxic and cause connective tissue damage, are known to be generate d under ischemic conditions. Blockage to the drainage of interstitial fluid within the metaphysis has been suggested as the possible primary cause of simple bone cyst, thus causing an ischemic state in which fr ee radicals are generated. The precise measurement of free radical lev els is difficult to obtain because of their extremely short half-lives . High levels of oxygen-free radicals induce high levels of oxygen sca vengers Locally to protect cells from the harmful effects of the free radicals. Therefore, the activity of the oxygen scavengers, superoxide dismutase and catalase, was measured in the cyst fluid of 9 cases of simple bone cyst as an indicator of high oxygen-free radical content i n the cyst. Serum from the patients with simple bone cyst and joint fl uid from patients with osteoarthritis were used for comparison with th e intracystic levels of oxygen scavengers. Superoxide dismutase activi ty was directly measured at room temperature using an electron spin re sonance spin-trapping technique with 5,5'-dimethyl-1-pyrroline-N-oxide as a trapping agent. Catalase was measured with a spectrophotometer. Superoxide dismutase activity in cyst fluid was 15-fold greater than i n the patients' serum, and catalase activity was 5.5-fold higher. Thes e values were also significantly higher than those in joint fluid from osteoarthritis patients. These results suggest that high activity of oxygen radicals may exist in cyst fluid of simple bone cyst and may co ntribute to bone destruction.