Therapeutic effects of Tetramethylpyrazine on Cartilage in Rat Model of Post-traumatic Osteoarthritis

Post-traumatic Osteoarthritis (PTOA) is a common secondary joint disease characterized by cartilage degradation, subchondral bone remodeling, and synovial inflammation following joint trauma. Current therapeutic options are limited in reversing pathological progression. Tetramethylpyrazine (TMP), an active alkaloid extracted from traditional Chinese medicine Ligusticum chuanxiong, exhibits anti-inflammatory, antioxidant, and cartilage protective properties. This study aimed to investigate the therapeutic effects of TMP in a rat model of PTOA. Sixty-three male Sprague–Dawley rats were randomly divided into sham and model groups. PTOA was induced using a modified Hulth method (anterior cruciate ligament and medial collateral ligament transection plus medial meniscectomy). Four weeks post-surgery, rats were intra-articularly administered TMP (2, 4, or 8 mg/kg) or hyaluronic acid sodium (HA, positive control) for 5 weeks. Functional recovery was assessed using grip strength and gait analysis. Cartilage and subchondral bone changes were evaluated by Micro-CT and histopathological staining (HE and safranin O-fast green). Immunohistochemistry was used to detect cartilage matrix components (COL II, MMP13 and ADAMTS5) at the protein level, while qRT-PCR was performed to validate the gene level of Col2a1 , Mmp13 and Adamts5 . ELISA was used to determine inflammatory cytokines (IL-1β, IL-18) in synovial fluid and serum. TMP significantly improved grip strength and normalized gait parameters in PTOA model rats. Micro-CT revealed that TMP attenuated subchondral bone loss and improved trabecular microarchitecture. Histological analysis showed that TMP restored cartilage surface integrity, increased chondrocyte density, and enhanced matrix staining. TMP significantly downregulated MMP13 and ADAMTS5 protein expression while upregulating COL II protein. Similarly, TMP restored Col2a1 mRNA expression and reduced Mmp13 and Adamts5 mRNA level in cartilage. TMP also decreased IL-1β and IL-18 levels in both serum and synovial fluid. Intra-articular administration of TMP effectively restored joint function and ameliorated PTOA progression in model rats by promoting cartilage matrix repair, inhibiting inflammatory responses, and improving subchondral bone microstructure. These findings suggest TMP as a potential therapeutic agent for PTOA treatment.