The influence of intra-articular hyaluronic acid on PGE2 and cAMP of synovial fluid

Prostaglandin (PG)E2, cyclic adenosine monophosphate (cAMP), white blood cells (WBC), total protein (TP), total complement activity (CH50) and beta-2-microglobulin (beta-2-m) were measured at baseline and after eight days in the synovial fluid (SF) of 16 patients affected with knee-joint effusion due to various arthropathies. The volume of SF was also calculated. Eight patients--4 with rheumatoid arthritis (RA), 2 with recurrent monoarthritis (RM) and 2 with osteoarthritis (OA) were randomly allocated to the treatment with intra-articular injection of Hyalgan (HA, Na-hyaluronate, 20 mg/2 ml), while eight patients having similar arthropathies--4 RA, 2 RM and 2 OA--were not treated (control group). In the patients treated with HA a significant reduction of SF volume (from 28.5 +/- 5.1 ml to 20.5 +/- 4.0 ml; p less than 0.02) and PGE2 (from 96.1 +/- 22.7 pg/ml to 66.2 +/- 14.5 pg/ml; p less than 0.05) was found, whereas cAMP concentration was significantly increased (from 4.5 +/- 0.7 pmol/ml to 7.2 +/- 1.2 pmol/ml; p less than 0.05). No significant variations were observed in the control group. Moreover, no differences in WBC count, TP and beta-2-m and CH50 were found in either group. These data could suggest an anti-inflammatory effect of HA that appears to be mediated by PG-inhibition as well as cAMP stimulation.