[Tougu Xiaotong Capsule alleviates cartilage degeneration in mice with knee osteoarthritis by modulating Nav1.7].

Objective: To investigate the mechanism by which Tougu Xiaotong Capsule (TGXTC) alleviates chondrocyte degeneration in knee osteoarthritis (KOA).

Methods: Thirty 2-month-old C57BL/6 mouse models of KOA established using the Hulth method were randomized into model group, TGXTC group, and diclofenac sodium group and received treatment with saline, TGXTC (368 mg/kg), and diclofenac sodium (10 mg/kg) by gavage, respectively, with another 10 untreated mice as the blank control group. All interventions were administered 6 times a week for 4 weeks. After the treatments, structural changes in the cartilage tissue were observed with morphological staining, and Nav1.7 mRNA expression and the protein expression levels of Nav1.7, MMP-3, ADAMTS-5, and COX-2 were detected using RT-qPCR and Western blotting. Fluorescence in situ hybridization (FISH) was used to detect Nav1.7 expression in the chondrocytes. In cultured KOA chondrocytes, the effect of TGXTC and lentivirus-mediated Nav1.7 knockdown on MMP-3, MMP-13, ADAMTS-4, ADAMTS-5, and COX-2 protein expressions were assessed with Western blotting.

Results: In KOA mice treatments with TGXTC and diclofenac sodium both significantly alleviated structural damage of the cartilage layer, reduced Nav1.7 protein and mRNA expressions and lowered the expressions of MMP-3, ADAMTS-5, and COX-2 proteins in the cartilage tissues. FISH results indicated that TGXTC treatment significantly reduced IL-1β -induced Nav1.7 expression in the chondrocytes. In Nav1.7 knockdown experiment, Nav1.7 levels were significantly lower in IL-1β+sh-Nav1.7 group than in IL-1β group, and also lower in IL-1β+TGXTC group than in IL-1β+sh-Nav1.7+TGXTC group. TGXTC treatment significantly inhibited IL-1β-induced elevation of MMP-3, MMP-13, ADAMTS-4, ADAMTS-5 and COX-2 protein expressions in the chondrocytes, but its effects were strongly weakened by Nav1.7 knockdown.

Conclusion: TGXTC alleviates extracellular matrix metabolic disorder in KOA chondrocytes by regulating Nav1.7, thereby mitigating chondrocyte degeneration in KOA mice.