Chondroprotective Effects Of Low-intensity Pulsed Ultrasound On Temporomandibular Joint Osteoarthritis In Vitro

Objective:The present study aimed to investigate the effect of LIPUS on the Wnt/β-catenin signaling pathway in IL-1β-stimulated chondrocytes from the temporomandibular joint(TMJ)of rat in vitro.Osteoarthritis(OA)is a highlyprevalent degenerative disease characterized by progressive joint destruction including articular cartilage degeneration and frequently affects the temporomandibular joint.Interleukin-lb(IL-1p)is an important cytokine that enhances inflammatory reactions in OA cartilage.Recently,low-intensity pulsed ultrasound(LIPUS)was shown to enhance the articular cartilage type II collagen in a rat O A model in vivo and confer protection to chondrocytes.Methods:Chondrocytes were isolated from the TMJ of 3--4-week-old Sprague-Dawley rats and stimulated by LIPUS in the presence and absence of IL-1β.The gene and protein expression of Wnt3a,β-catenin,dickkopfl(DKK1),glycogen synthase kinase-3β(GSK3P),phosphor-GSK3β(p-GSK3P),type Ⅱ collagen(COL2A1),and aggrecan(AGG)was studied by real-time quantitative polymerase chain reaction analysis and Western blot analysis.RNAi was used to inhibit production of DKK1.Results:We show that LIPUS stimulation suppressed activation of the Wnt/β-catenin signaling pathway and increased the expression of COL2A1,and AGG in IL-1β-induced chondrocytes.We further show that the stimulation inhibits the canonical Wnt signaling pathway through expression of the canonical Wnt inhibitor DKK1.Finally we show that promotion of COL2A1 and AGG expression through LIPUS stimulation is mediated by DKK1.Conclusion:LIPUS has potential therapeutic effects for preventing cartilage degradation and treating OA via a mechanical stimulation that inhibits the Wnt/β-catenin signaling pathway and stimulates the production of extracellular matrix.This study will contribute to the understanding of the potential therapeutic function of LIPUS for the treatment of OA of the temporomandibular joint.Future clinical studies should be undertaken to confirm the effects.