RSPO2 and rheumatoid arthritis: Additionally, rmRspo2 administration caused significantly elevated expression of MMP3 in RA synovium, along with increased colocalization of Vimentin (an FLS marker) compared to controls, which suggested that Rspo2 could significantly facilitate FLS proliferation and invasion, while the administration of Rspo2-NAb or rmDKK1 caused obviously decreased expression of MMP3 in synovium, as well reduced colocalization of Vimentin compared to controls (Fig. 4B, C), indicating that Rspo2 promoted FLS proliferation and invasion in the progression of RA via activating the β-catenin signaling pathway.