The Effect of Low Intensity Pulsed Ultrasound on TMJ Arthritis in Juvenile Rats.

Juvenile idiopathic arthritis (JIA) is an inflammatory disease that can affect the temporomandibular joint (TMJ) and lower jaw growth. Better treatment options are needed, so this study investigated the effect of low intensity pulsed ultrasound (LIPUS) on TMJ arthritis. Seventy-two 3-week old male Wistar rats were in vivo micro-computed tomography (MicroCT) scanned and divided into 8 groups (n=9). These groups were Group 1 - TMJ arthritis and immediate LIPUS treatment (20 minutes/day, 4 weeks); Group 2 - immediate LIPUS treatment and no TMJ arthritis; Group 3 - TMJ arthritis and no LIPUS; Group 4 - no TMJ arthritis and no LIPUS; Group 5 - TMJ arthritis and LIPUS treatment with a delayed start by 4 weeks; Group 6 - delayed LIPUS and no TMJ arthritis; Group 7 - TMJ arthritis and no (delayed) LIPUS; and Group 8 - no TMJ arthritis and no (delayed) LIPUS. Ex-vivo MicroCT scanning was completed, and samples were prepared for tissue analysis. Synovitis was observed in the TMJ arthritis [collagen-induced arthritis (CIA)] groups, but the severity appeared greater in the groups without LIPUS treatment. Fibrocartilage and hypertrophic cell layer thicknesses in the CIA group without LIPUS treatment were significantly greater (p < 0.05). Proteoglycan staining appeared greater in the LIPUS groups. Immediate LIPUS treatment increased the expression of type II collagen, type X collagen, and TGF-β1 immunostaining, and CIA (no LIPUS) increased MMP-13, VEGF and IL-1β immunostaining. LIPUS treatment prevented growth disturbances observed in the CIA groups (no LIPUS) (p < 0.005). Our results have contributed to the understanding of the uses and limitations of the CIA juvenile rat model and have demonstrated the effects of LIPUS on the TMJ and mandibular growth. This information will help in designing future studies for investigating LIPUS and TMJ arthritis, leading to the development of new treatment options for children with juvenile arthritis in their TMJs.