Objective The aim of the study was to investigate the role and regulatory mechanisms of fibroblast-like synoviocytes (FLSs) and their senescence in the progression of osteoarthritis (OA).
Methods Synovial tissues from normal patients and patients with OA were collected. Synovium FLS senescence was analysed by immunofluorescence and western blotting. The role of methyltransferase-like 3 (METTL3) in autophagy regulation was explored using N6-methyladenosine (m6A)-methylated RNA and RNA immunoprecipitation assays. Mice subjected to destabilisation of the medial meniscus (DMM) surgery were intra-articularly injected with or without pAAV9 loaded with small interfering RNA (siRNA) targeting METTL3. Histological analysis was performed to determine cartilage damage.
Results Senescent FLSs were markedly increased with the progression of OA in patients and mouse models. We determined that impaired autophagy occurred in OA-FLS, resulting in the upregulation of senescence-associated secretory phenotype (SASP). Re-establishment of autophagy reversed the senescent phenotype by suppressing GATA4. Further, we observed for the first time that excessive m6A modification negatively regulated autophagy in OA-FLS. Mechanistically, METTL3-mediated m6A modification decreased the expression of autophagy-related 7, an E-1 enzyme crucial for the formation of autophagosomes, by attenuating its RNA stability. Silencing METTL3 enhanced autophagic flux and inhibited SASP expression in OA-FLS. Intra-articular injection of synovium-targeted METTL3 siRNA suppressed cellular senescence propagation in joints and ameliorated DMM-induced cartilage destruction.
Conclusions Our study revealed the important role of FLS senescence in OA progression. Targeted METTL3 inhibition could alleviate the senescence of FLS and limit OA development in experimental animal models, providing a potential strategy for OA therapy.
- biological therapy
Data availability statement
Data are available upon reasonable request. Not applicable.
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Handling editor Josef S Smolen
Contributors XC conducted the most assays and acquired and analysed the data. WG, XS and TS helped with animal housing and genotype identification. LZ, JD and YS participated in some experiments and collected human samples. QJ and BS conceived the project, designed the study, arranged the results and revised the manuscript. All authors approved the final version of the manuscript. BS accepted full responsibility for the finished work, had access to the data and controlled the decision to publish.
Funding This work was supported by research grants from the National Key Research and Development Program of China (number 2020YFC2004900); National Natural Science Foundation of China (numbers 82000069, 81991514, 81730067, 82002370 and 81972124); Natural Science Foundation of Jiangsu Province of China (BK20200314 and BK20200117); Youth Thousand Talents Program of China (number 13004001); The Research Team Start-up Funds of Nanjing University (number 14912203); Program of Innovation and Entrepreneurship of Jiangsu Province; China Postdoctoral Science Foundation (number 2019M661806).
Competing interests None declared.
Provenance and peer review Not commissioned; externally peer reviewed.
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