RSPO2 and rheumatoid arthritis: Compared to controls, an obvious increase of synovitis scores with marked synovial hyperplasia and inflammatory cell infiltration was found in the synovium of RA mice treated with rmRspo2, at both 4 weeks and 8 weeks after AIA, while treatment with Rspo2-NAb or rmDKK1 obviously attenuated synovitis score in RA mice at both 4 weeks and 8 weeks after AIA (Fig. 3A, C).