Hyaluronan molecular weight and polydispersity in some commercial intra-articular injectable preparations and in synovial fluid

Objective and Design: Hyaluronan is the major non-proteinaceous component of joint synovial fluid and is responsible for the unique rheological and biological properties of this medium. In joint arthropathies the molecular weight and concentration of hyaluronan may change, thereby influencing joint physiology and function. Intra-articular administrated hyaluronan derived from a number of sources, has been used for the treatment of osteoarthritis, however, there is limited information on the molecular weight and polydispersity of these various commercial preparations. The objective of this study was to develop an accurate, convenient method by which the molecular weight and polydispersity of hyaluronan may be determined and then applied to characterise the hyaluronan in synovial fluid.¶Materials and Methods: Characterisation of the molecular parameters of hyaluronan of different origins and in ovine synovial fluid was accomplished using a multi-angle laser-light scattering (MALLS) detector coupled to a gel permeation chromatography (GPC) system, fitted with an automatic sample injector.¶Conclusion: Seven commercially available hyaluronan preparations of reported molecular weight were analysed. The weight average molecular weight (Mw) and number average molecular weight (Mn) values obtained for 6 of the 7 preparations using the MALLS-GPC system were in good agreement with the reported values. The abnormally low values for the exception suggested that degradation of hyaluronan had occurred. The MALLS-GPC technique was then used to determine the molecular characteristics of the endogenous hyaluronan in normal ovine synovial fluids. While the Mws ranged from less than 1 × 106 Da to 7 × 106 Da the majority were between 1-3 × 106 Da. [mean Mw = 2.42 × 106, mean Mn = 2.21 × 106 Da]. The effects of freezing and thawing synovial fluid upon molecular weight of hyaluronan were also investigated and were found to diminish both Mz and Mw values.