Diclofenac etalhyaluronate provides cartilage-protective effects in a mouse model of knee osteoarthritis.

BACKGROUND

To investigate the molecular basis of the chondroprotective effects of diclofenac etalhyaluronate (DFHA), which is an intra-articular diclofenac-hyaluronic acid conjugate that provides sustained anti-inflammatory and analgesic effects and has been reported to enhance high-molecular-weight hyaluronate production, in a mouse model of knee osteoarthritis (OA).

METHODS

Twelve-week-old male mice underwent surgery to cause destabilization of the medial meniscus (DMM) and induce OA of the knee. Mice were subsequently administered intra-articular injections of saline (placebo), hyaluronic acid (HA), or DFHA every four weeks. Behavioral changes were evaluated every two weeks using the open field test. Knee joints were harvested at 8 and 12 weeks after DMM surgery for histological analysis, and samples collected at 8 weeks were subjected to RNA-seq.

RESULTS

Open field testing demonstrated significantly reduced distance from the arena center point in the HA and DFHA groups compared with placebo group, suggesting altered exploratory behavior. At 8 weeks after DMM surgery, histological analysis showed significantly larger articular cartilage area only in the DFHA group, whereas OARSI scores did not significantly differ among groups. At 12 weeks after DMM surgery, the OARSI score was significantly lower in the DFHA group than in the HA group, although no significant difference was observed in articular cartilage area or osteophyte area. RNA-seq followed by gene ontology enrichment analysis indicated that genes upregulated in the DFHA group were enriched in biological processes related to cartilage development and tissue homeostasis. In joint capsule tissue, genes downregulated in the DFHA group were enriched for terms related to p53-mediated signaling and the electron transport chain.

CONCLUSIONS

DFHA showed cartilage-protective effects in a mouse DMM model of knee OA, accompanied by transcriptional changes in osteochondral tissue that may be related to cartilage maintenance. Further studies are needed to clarify the mechanisms underlying DFHA-associated chondroprotection and its tissue-specific effects.