ES-62 suppression of arthritis reflects epigenetic rewiring of synovial fibroblasts to a joint-protective phenotype

The parasitic worm product, ES-62 protects against collagen-induced arthritis, a mouse model of rheumatoid arthritis (RA) by suppressing the synovial fibroblast (SF) responses perpetuating inflammation and driving joint destruction. Such SF responses are shaped during disease progression by the inflammatory microenvironment of the joint that promotes remodelling of their epigenetic landscape, inducing an “aggressive” pathogenic SF phenotype. Critically, exposure to ES-62 in vivo induces a stably imprinted “safe” phenotype that exhibits responses more typical of healthy SFs. Surprisingly however, DNA methylome analysis reveals that rather than simply preventing the pathogenic rewiring of SFs, ES-62 induces further epigenetic remodelling, including targeting genes associated with ciliogenesis and differentiation, to program a distinct “protective” phenotype. Such unique behaviour signposts potential DNA methylation signatures predictive of pathogenesis and its resolution and hence, candidate mechanisms by which novel therapeutic interventions could prevent SFs from perpetuating joint inflammation and destruction in RA. ### Competing Interest Statement The authors have declared no competing interest.