Therapeutic effect of low-intensity pulsed ultrasound on temporomandibular joint injury induced by chronic sleep deprivation in rats

Low-intensity pulsed ultrasound (LIPUS) treatment is an emerging physical therapy for treating bone, nerve, and muscle disorders. However, there have been no reports on the effectiveness of LIPUS for the treatment of temporomandibular joint injury, and the mechanisms of LIPUS remain unclear. The purpose of this study was to examine the therapeutic effects of LIPUS on temporomandibular joint injury in rats subjected to chronic sleep deprivation (CSD). In this study, after 2 weeks of chronic sleep deprivation in rats, the condylar cartilage exhibited rough surfaces, with a disorganized arrangement and partial sloughing of collagen fibers, decreased proliferation of chondrocytes, increased osteoclast activity in the calcified cartilage layer, and increased ratios of MMP-3/TIMP-1 and RANKL/OPG expression. After 4 weeks of LIPUS intervention in rats, the condylar cartilage displayed prominent reductions in these pathological changes, including noticeable repair of the injured cartilage structure, increased chondrocyte proliferation, a reduced number of osteoclasts, and marked reductions in the expression ratios of MMP-3/TIMP-1 and RANKL/OPG. These results demonstrated that LIPUS can effectively inhibit CSD-induced injury to condylar cartilage in rats. The therapeutic mechanism of LIPUS may involve promoting the repair function of chondrocytes and reducing the expression ratios of MMP-3/TIMP-1 and RANKL/OPG in condylar tissue, thus inhibiting the cleavage activity of MMP-3 on the condylar cartilage matrix and inhibiting osteoclast activation.