Effects of hyaluronic acid on cartilage degradation.

Based on the published literature available so far, it appears that naturally derived hyaluronic acid (HA) and newer formulations available on the market belong to the pharmacologic class of slow-acting drugs for the treatment of osteoarthritis. These compounds seem to have the potential to modulate the painful symptoms of osteoarthritis as well as to improve the function of the osteoarthritis joint. Positive clinical consequences are based on direct and indirect effects of viscosupplementation associated with a normalization of the rheologic properties of the osteoarthritic synovial fluid, decreased inflammation, and end-coating of the pain receptors in the osteoarthritis joint. Few in vivo data exist in humans to support the concept that HA formulations could have a structure-modifying effect on human osteoarthritis cartilage. Animal-based studies have demonstrated positive effects of exogenous HA on pain in the joint, heat shock proteins, and in models of osteoarthritis. Although many promising effects of exogenous HA have been reported, there remains uncertainty as to the effectiveness of reversing cartilage injury and other manifestations of joint diseases with exogenous HA because of difficulties in interpreting and unifying results of these studies. This is due largely to differences of cartilage source in models of joint/cartilage injury, multiple end points, the controls employed, analytical techniques, and the molecular weight of exogenous HA used. There exists a need for uniform agreement as to the choice of injury model, time points of the study, evaluation tools, and source and molecular weight of the HA used if we are to determine whether exogenous application of HA has a truly beneficial role in the reversal of cartilage injury.