METTL3-mediated m6A modification of ATG7 regulates autophagy-GATA4 axis to promote cellular senescence and osteoarthritis progression

Ann Rheum Dis. 2022 Jan;81(1):87-99. doi: 10.1136/annrheumdis-2021-221091. Epub 2021 Oct 27.

Abstract

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.

Keywords: biological therapy; fibroblasts; inflammation; knee; osteoarthritis.

Publication types

  • Research Support, Non-U.S. Gov't

MeSH terms

  • Adenosine / analogs & derivatives*
  • Adenosine / metabolism
  • Animals
  • Autophagy / genetics*
  • Autophagy-Related Protein 7 / genetics
  • Autophagy-Related Protein 7 / metabolism
  • Cartilage, Articular / pathology
  • Cell Line
  • Cellular Senescence / genetics*
  • Chondrocytes / metabolism
  • Coculture Techniques
  • Disease Models, Animal
  • Disease Progression
  • Female
  • GATA4 Transcription Factor / genetics
  • GATA4 Transcription Factor / metabolism
  • Gene Expression
  • Humans
  • Immunoprecipitation
  • Male
  • Methylation
  • Methyltransferases / genetics*
  • Mice
  • Middle Aged
  • Osteoarthritis / genetics*
  • Osteoarthritis / metabolism
  • RNA Processing, Post-Transcriptional
  • RNA, Messenger / metabolism
  • RNA, Small Interfering / genetics
  • RNA-Binding Proteins / genetics
  • Synoviocytes / physiology*
  • Up-Regulation

Substances

  • Atg7 protein, mouse
  • GATA4 Transcription Factor
  • GATA4 protein, human
  • RNA, Messenger
  • RNA, Small Interfering
  • RNA-Binding Proteins
  • YTHDF2 protein, human
  • N-methyladenosine
  • Methyltransferases
  • Mettl3 protein, mouse
  • METTL3 protein, human
  • ATG7 protein, human
  • Autophagy-Related Protein 7
  • Adenosine