Importance of synovitis in osteoarthritis: Evidence for the use of glycosaminoglycans against synovial inflammation

Objectives: After detailing the different aspects of synovial inflammation (i.e., cellular, biochemical, and vascular) and based on the current knowledge, the aim of this review was to collect the available in vitro and in vivo data regarding the potency of some glycosaminoglycan (GAG) compounds to target synovial inflammation, an important aspect of osteoarthritis. Methods: The first part of the review corresponds to a qualitative review of the inflammatory status of OA synovial membrane. The second part corresponds to a systematic review of the literature regarding the potential effects of some GAGs on the previously described phenomenon. Results: The synovial aspect of the inflammatory status of OA has been detailed. Chondroitin sulfate has demonstrated to control the three aspects of synovial membrane inflammation: cell infiltration and activity, biochemical mediators release, and angiogenesis. Glucosamine is also active on both cellular and molecular aspects of the inflammatory reaction. Hyaluronic acid seems to be anti-inflammatory in its native form, while products of degradation are reported to be pro-angiogenic. Conclusion: Much evidence suggests that some of the studied GAG compounds could target different aspects of synovitis. Some of them could be considered in combination therapy since they exhibit complementary properties. Most of the studies have concentrated on articular cartilage and chondrocytes. In order to achieve a structure modification, one may now consider all joint tissues and investigate the drug potency on all of them. Potent treatment should trigger the most important features of OA: cartilage degradation, subchondral bone sclerosis, and all aspects of synovial inflammation. (C) 2014 Elsevier Inc. All rights reserved.