Somatomedin activity in synovial fluid from patients with joint diseases

The somatomedin activity in synovial fluids from 50 patients with a variety of joint diseases has been studied and compared with the activity in each of the patient's own serum and a standard reference serum (SRS). The porcine costal cartilage bioassay of Van den Brande and Du Caju (1974a) has been used with the isotopes 3H-thymidine and 35S-sulphate. Synovial fluids from most patients with post-traumatic and post-operative effusions, osteoarthritis and arthritis associated with psoriasis, Reiter's disease, and ankylosing spondylitis stimulated the synthesis of DNA and proteoglycans in cartilage. Synovial fluids from patients with rheumatoid arthritis either had impaired capacity to stimulate DNA synthesis, or they inhibited it; a similar, but less evident pattern was observed for proteoglycan synthesis. Some synovial fluids from patients with miscellaneous synovitides stimulated, while others inhibited cartilage metabolism. It is concluded that the synovial fluid from patients with rheumatoid arthritis and from some patients with miscellaneous synovitides contained an inhibitor(s) to DNA and possibly proteoglycan synthesis. The sera from nearly all the patients stimulated both DNA and proteoglycan synthesis, but the somatomedin potency ratios for serum in terms of SRS were generally less than 1.0. There was a significant inverse correlation between the serum somatomedin potency ratio and the age of the patient.