Quantitative measurement of serum hyaluronic acid molecular weight in rheumatoid arthritis patients and the role of hyaluronidase

Aim:  Hyaluronic acid (HA) is a glycosaminoglycan and is essential for protecting the cartilage surface by its physical property. It is known that serum HA concentration in rheumatoid arthritis (RA) patients is higher than in healthy volunteer. However, molecular weight (MW) of serum HA in RA patients is not clear, since it needs a large sample volume to assay serum HA MW. The aim of this study is to establish the method for measuring serum HA MW in small sample sizes and to assess the association between serum HA MW and hyaluronidase (HAase) activity. Methods:  MW of serum HA in RA patients was measured using high-performance liquid chromatography and HA-binding protein. Additionally, the correlation between serum HA and HAase activity was examined using zymographic measurements. Results:  Serum HA MW peaked at 1–2 × 105 Da in all cases. However, in certain cases two peaks were observed, one each at low (1–2 × 105 Da) and high (8–14 × 105 Da) MW. HAase activity was lower in cases exhibiting this two-peaked serum HA MW pattern than in those cases with only a single peak. Conclusion:  The novel method developed for this study permits accurate measurement of serum HA MW. The correlation observed between serum HA MW and HAase activity suggests that serum HA MW may reflect the condition of subjects’ joints.