17β-estradiol promotes the progression of temporomandibular joint osteoarthritis by regulating the FTO/IGF2BP1/m6A-NLRC5 axis.

Background: Temporomandibular joint osteoarthritis (TMJOA) is a degenerative cartilage disease. 17β-estradiol (E2) aggravates the pathological process of TMJOA; however, the mechanisms of its action have not been elucidated. Thus, we investigate the influence of E2 on the cellular biological behaviors of synoviocytes and the molecular mechanisms.

Methods: Primary fibroblast-like synoviocytes (FLSs) isolated from rats were treated with TNF-α to establish cell model, and phenotypes were evaluated using cell counting kit-8, EdU, Tanswell, enzyme-linked immunosorbent assay, and quantitative real-time PCR (qPCR). The underlying mechanism of E2, FTO-mediated NLRC5 m6A methylation, was assessed using microarray, methylated RNA immunoprecipitation, qPCR, and western blot. Moreover, TMJOA-like rat model was established by intra-articular injection of monosodium iodoacetate (MIA), and bone morphology and pathology were assessed using micro-CT and H&E staining.

Results: The results illustrated that E2 facilitated the proliferation, migration, invasion, and inflammation of TNF-α-treated FLSs. FTO expression was downregulated in TMJOA and was reduced by E2 in FLSs. Knockdown of FTO promoted m6A methylation of NLRC5 and enhanced NLRC5 stability by IGF2BP1 recognition. Moreover, E2 promoted TMJ pathology and condyle remodeling, and increased bone mineral density and trabecular bone volume fraction, which was rescued by NLRC5 knockdown.

Conclusion: E2 promoted the progression of TMJOA.