DNA hypermethylation of SFRP2 influences the pathology of rheumatoid arthritis through the canonical Wnt signaling in model rats

Abstract

In this work, the expression of secreted frizzled related protein 2 (SFRP2) in rheumatoid arthritis (RA) model rats and the mechanisms of SFRP2 on the RA pathogenesis were investigated. Data suggested that SFRP2 was significantly down-regulated in RA model rats compared with normal control, and overexpression of SFRP2 suppressed the RA pathogenesis and the canonical Wnt signaling in fibroblast-like synovial cells (FLS) from RA model rats, whereas knockdown of SFRP2 got an opposite observation. Interestingly, 5-azadC treatment up-regulated the SFRP2 expression, inhibited the FLS proliferation, suppressed the expression of IL-6 and IL-8 and the fibronectin production, suggesting that the decreased SFRP2 in RA model rats was due to the DNA methylation. Furthermore, DNMT1 knockdown up-regulated the SFRP2 expression, DNMT1 overexpression inhibited the SFRP2, and the quantitative methylation-specific PCR (qMSP) confirmed that the DNMT1 has direct methylation roles for the SFRP2 promoter, leading to a regulation of FLS proliferation and fibronectin expression in RA model rats. In addition, up-regulated MeCP2 was involved in the SFRP2 regulation and the pathogenesis of RA model rats, and MeCP2 and DNMT1 have synergistic inhibition roles in the SFRP2 expression. Combination of DNMT1 and DNA methylation may be a promising treatment strategy for individuals with RA in which SFRP2 is down-regulated.