Introduction: Patients with rheumatoid arthritis (RA) have increased aortic stiffness, which can be improved with anti-inflammatory therapies. However, how inflammation leads to aortic stiffening remains unclear. One potential mechanism is by overproduction of hyaluronan (HA) in the extracellular matrix, which results in stiffening of the arterial wall by thinning of elastic lamellae in animal models. However, the effect in man is unknown. The aim was to evaluate 1) whether serum HA concentration is a valid surrogate of aortic tissue level and 2) to compare serum HA in patients with RA and control subjects and to relate this to aortic pulse wave velocity (aPWV).

Methods: 18 aortic tissue samples were homogenised and HA concentration in the homogenate and corresponding serum sample was assessed using commercially available ELISA kit (DY3614, R&D Systems, U.K). Also, aPWV using SphygmoCor system, and Serum HA was assessed in 40 patients with RA and in 40 matched control subjects.

Results: There was a correlation between tissue and serum HA (R=0.68; P=0.01). Patients with RA had higher serum HA compared to controls (66.6±65.2 v. 11.0±7.9 ng/ml; P<0.0001). In patients with RA, the serum HA levels correlated with aPWV (R=0.3; P=0.01).

Conclusion: This study demonstrates that serum HA is increased in patients with RA in comparison to control subjects, and this correlates with aortic stiffening. The data suggests that increased HA synthesis may be the mechanism behind inflammation-induced aortic stiffness in patients with RA. However, further experiments are needed to study causality between tissue HA concentration and aortic stiffness.