RSPO2 and rheumatoid arthritis: Interestingly, downregulated LGR5 and β-catenin were observed in synovium and cartilage of Rspo2-NAb-treated RA mice, while obviously reduced β-catenin-positive cells, not LGR5-, was observed in synovium and cartilage in rmDKK1-treated RA mice (Fig. 2C).