Injectable hyaluronic acid-tyramine hydrogels for the treatment of rheumatoid arthritis.

Rheumatoid arthritis (RA) is a chronic inflammatory disease caused by inflammation of the synovial membrane, leading in turn to articular cartilage destruction. In this work, injectable tyramine modified hyaluronic acid (HA-Tyr) hydrogels were developed for the treatment of RA. HA-Tyr conjugate was synthesized by amide bond formation between carboxyl groups of HA and amine groups of tyramine. Then, HA-Tyr hydrogels were prepared by radical crosslinking reaction using H(2)O(2) and horse-radish peroxidase. Intra-articular injection of HA-Tyr hydrogels encapsulating dexamethasone (DMT) as a model drug resulted in successful treatment of RA with reduced interlukine-6, prostaglandin E2 and four types of cytokine levels in collagen-induced arthritis animal models. Histological analysis with hematoxylin and eosin (H&E) staining also confirmed the therapeutic effect of injectable HA-Tyr hydrogels with DMT. Taken together, the injectable HA-Tyr hydrogels were thought suitable to be developed as a therapeutically effective drug carrier for the treatment of RA.