Inhibition of Toll-Like Receptor 3 Relieves Osteoarthritis by Suppression of Cartilage Degradation, Nuclear Factor Kappa B-Mediated Inflammation, and Activation of Autophagy.

Objective: To investigate the regulatory role of Toll-like receptor 3 (TLR3) in osteoarthritis (OA) progression, particularly its impacts on cartilage degradation, NF-κB-mediated inflammation, and autophagy activation.

Method: 1. Model Constuction: OA mouse model generated via anterior cruciate ligament transection (ACLT); LPS-induced inflammatory injury in murine ATDC5 chondrocytes; Histomorphological analysis of cartilage tissue using H&E and Safranine O staining. 2. Molecular Detection: TLR3 expression assessed by Western blot; Cartilage degradation markers (MMP-13, ADAMTS) and NF-κB pathway proteins analyzed via Western blot; Pro-inflammatory cytokine levels (IL-1β, TNF-α) quantified via RT-qPCR and Western blot. 3. Functional Assays: Cell viability examined via CCK-8 assay.

Results: 1. TLR3 Upregulation: TLR3 was highly expressed in OA cartilage and LPS-treated chondrocytes. 2. Cartilage Protection: TLR3 inhibition reduced cartilage erosion and proteoglycan loss in ACLT mice (confirmed by H&E and Safranine O staining); Downregulation of cartilage degradation markers (MMP-13, ADAMTS-5) observed in TLR3-knockdown models. 3. Anti-inflammatory Effects: TLR3 knockdown suppressed NF-κB activation, reducing IL-1β and TNF-α levels. 4. Autophagy Activation: Enhanced LC3-II/LC3-I ratio and Beclin-1 expression indicated TLR3 inhibition promotes autophagy.

Conclusion: TLR3 drives OA progression through dual mechanisms: 1. Pro-inflammatory Pathway: Activates NF-κB signaling to amplify cytokine release and cartilage matrix breakdown. 2. Autophagy Suppression: Inhibits autophagy-related proteins, impairing cellular homeostasis. Targeting TLR3 may represent a therapeutic strategy to balance inflammation and autophagy, potentially slowing OA progression in multi-joint involvement cases.