Targeting the SNORD3-EZH2-ESM1 signaling axis in fibroblast-like synoviocytes ameliorates rheumatoid arthritis

Rheumatoid arthritis (RA) is a prevalent chronic autoimmune disorder characterized by synovial inflammation and bone destruction. Despite the availability of various diseasemodifying antirheumatic drugs (DMARDs), 40%-60% of patients exhibit poor response to current therapies, emphasizing the urgent need for new therapeutic targets and strategies.
Recently, we have collected synovial specimens from RA and osteoarthritis (OA) patients. Unlike RA, OA is primarily driven by mechanical wear and tear rather than autoimmune mechanisms. Comparing these specimens allows us to elucidate RA-specific pathological processes. Through RNA sequencing, we identify a significantly elevated small nucleolar RNA (snoRNA), SNORD3, in synovial tissues of RA patients. Further analysis reveals abnormally high expression levels of SNORD3 in RA fibroblast-like synoviocytes (RA-FLSs) and collagen-induced arthritis (CIA) mice. Our functional assays demonstrate that SNORD3 is responsive to inflammation and exacerbates the aggressive nature of RA-FLSs. In vivo, we observe a remarkable reduction in arthritic symptoms in mice by silencing SNORD3 using an aptamer-functionalized siRNA delivery system designed for FLSs.
Mechanistically, we find that SNORD3 induces the upregulation of ESM1. Specifically, SNORD3 interacts with EZH2, a subunit of the polycomb repressive complex 2 (PRC2), and disrupts its association with RBBP4. This reduces the H3K27me3 mark on the ESM1 promoter, relieving its transcriptional repression and promoting the aggressive transformation of RA-FLSs. Based on these findings, we speculate that targeting the SNORD3-EZH2-ESM1 signaling axis could treat RA. Aptamers, RNA or ssDNA, can be used as therapeutic agents for disease treatment. We screened the aptamer ESMA04, which could neutralize ESM1 and block the aggressive phenotype of ESM1-mediated RA-FLSs in vitro, meaning that it could act as a therapeutic aptamer for ESM1 for the treatment of RA.

In this study, we propose:
(1) To reveal the downstream signaling pathway mediated by the SNORD3-EZH2- ESM1 axis;
(2) To examine whether FLSs-specific knockout of SNORD3 or ESM1 in mouse models can alleviate arthritis;
(3) To explore the therapeutic effect of aptamer ESMA04 alone or in combination with TNF monoclonal antibody in arthritis mice;
(4) To detect the toxicity of aptamer ESMA04 alone or in combination with a TNF monoclonal antibody in arthritic mice