Akt2 inhibition alleviates temporomandibular joint osteoarthritis by preventing subchondral bone loss

Abstract

This study aimed to investigate the role and mechanism of the Akt2 pathway in different stages of anterior disc displacement (ADD)-induced temporomandibular joint osteoarthritis (TMJOA). A rat model for TMJOA that simulates anterior disc displacement was established. For inhibit Akt2 expression in subchondral bone, rats were intravenously injected with adeno-associated virus carrying Akt2 shRNA at a titer of 1 × 1012 transducing units/mL 10 days before the ADD or sham operations. The rats were euthanized and evaluated 1 or 8 weeks after surgery, as these time points represented the early or advanced stage of ADD. Immunostaining was performed to examine the expression and location of phosphorylated Akt2 in different stages of ADD. Microcomputed tomography, hematoxylin and eosin staining, toluidine blue staining, Western blotting, immunohistochemical and immunofluorescence staining were used to elucidate the pathological changes and potential mechanisms underlying ADD-induced TMJOA. In the rat model of ADD-induced TMJOA, rapid condylar bone loss occurred with increased phosphorylation of Akt2 in subchondral bone macrophages within 1 week post-surgery. At 8 weeks after surgery, abnormal remodeling of subchondral bone and degenerative changes in cartilage were observed. Inhibiting Akt2 reduced condylar bone resorption following ADD surgery while improving condylar bone morphology at 8 weeks post-surgery. Additionally, inhibition of Akt2 alleviated cartilage degeneration characterized by a decreased number of apoptotic chondrocytes, reduced expression of matrix metalloproteinases, and increased collagen type II expression in cartilage tissue. The Akt2 pathway is activated mainly in subchondral bone macrophages during the early stage of ADD and plays an important role in regulating subchondral bone remodeling. Inhibition of Akt2 could serve as a prophylactic treatment to slow the progression of ADD-induced TMJOA.