Early Intervention of Subchondral Bone Resorption Mitigates Cartilage Degeneration in TMJOA

BACKGROUND: Excessive subchondral bone resorption is a typical manifestation in the early stage of osteoarthritis. This study is to verify whether and when intervening in subchondral bone could alleviate cartilage degeneration of temporomandibular joint osteoarthritis. METHODS: Disc displacement without reduction was used to induce temporomandibular joint osteoarthritis. Alendronate was administered subcutaneously twice a week at a dosage of 60 μg/kg body weight for 1 week by two intervention methods: early administration (1 day after disc displacement without reduction surgery) and late administration (2 weeks after disc displacement without reduction surgery). Micro-CT was used to assess subchondral bone mass and microstructure. Hematoxylin-eosin staining, toluidine blue staining, tartrate-resistant acid phosphatase staining, immunofluorescence staining, and Western blot were applied to evaluate histopathological changes of the condylar cartilage and subchondral bone. RESULTS: Early alendronate administration not only prevented subchondral bone resorption in early-stage temporomandibular joint osteoarthritis, but also suppressed chondrocyte apoptosis, cartilage extracellular matrix degeneration, as well as excessive subchondral bone formation of condyle in late-stage temporomandibular joint osteoarthritis. However, late alendronate administration had little effect on either subchondral bone or cartilage degenerative changes. CONCLUSIONS: Early inhibition of subchondral bone resorption could mitigate abnormal subchondral bone formation and condylar cartilage degeneration in late-stage temporomandibular joint osteoarthritis, which might be a promising strategy for temporomandibular joint osteoarthritis treatment.