ANTI-INFLAMMATORY AND STRUCTURE PROTECTIVE EFFECTS OF HYALURONANS: ARE THESE EFFECTS MOLECULAR WEIGHT DEPENDENT?

Although hyaluronans (HA) has been proved to be effective in the treatment of patients with osteoarthritis and rheumatoid arthritis, the correlations between these effects and the molecular weight (MW) of HA have not been systematically followed. Many different HA preparations are now applied worldwide in clinical usage. Their MWs are very wide ranged (500-6,000 kDa). No systematic review especially addresses the role of HA's MW in the effects of anti-inflammation and structure protection. This study evaluates the literature of the basic and clinical studies on biological, pathological, and clinical effects of different MW HA. Databases were searched through PubMed (period 1978-2009), using the terms hyaluronan, hyaluronic acid, arthritis, and MW. Reference lists of relevant articles were controlled for additional references. We define the "high" MW (HMW) as MW greater than 2,000 kDa and define the "low" MW (LMW) as MW less than 2,000 kDa in the current study. Most data that support the structure protective effect of HA are from the studies with LMW HA. On the other hand, the majority of data that recommend the anti-inflammatory effect of HA are from the reports of HMW HA. In conclusion, we suggest that the effects of LMW HA were more structure protective and those of HMW HA were more anti-inflammatory.