Comparison of effects of intra-articular diclofenac etalhyaluronate and hyaluronic acid in a monoiodoacetate rat osteoarthritis model

Diclofenac etalhyaluronate (DF-HA) sustained diclofenac release with the effects of hyaluronic acid (HA), offering long-term analgesia in osteoarthritis. In this study, the effects of DF-HA on pain improvement and osteoarthritis were evaluated in a rat knee monoiodoacetate-induced osteoarthritis model compared to HA. Eight rats per group had been injected with monoiodoacetate (2.0 mg) or saline in the right knee for 4 weeks and were injected with either DF-HA (1.25 mg/kg; 0.5 mg), HA (0.5 mg), vehicle which was a substrate without DF-HA (50 μL), or saline and followed for 4 weeks. Mechanical plantar skin sensitivity was assessed weekly using the von Frey assay. Osteoarthritis changes were monitored with Larsen scores via CT imaging at every 2 weeks. The articular cartilage was analyzed using OARSI scores through H&E, Safranin-O staining at 8 weeks. The percentage of Iba-1 positive microglia in the spinal dorsal horn and of FG + CGRP-labeled cells among FG-positive cells in the dorsal root ganglion were evaluated by immunohistochemical staining. TNF-α and IL-6 mRNA expression levels in the knee synovium were evaluated by PCR. The DF-HA showed significantly improved pain hypersensitivity compared with the HA at 6–8 weeks. The percentage of Iba-1-positive microglia was significantly lower than that in the vehicle and the percentage of FG + CGRP/FG was significantly lower than that in the HA. OARSI scores did not differ among treatment groups, Larsen scores indicated lower in the DF-HA than in the vehicle. DF-HA was as effective as HA in joint protection and significantly improved inflammatory pain compared to HA.