RSPO2 and rheumatoid arthritis: Secondly, although no significant difference in the number of LGR5-positive cells was detected in synovium and articular cartilage between rmDKK1-treated RA mice and their control, elevated protein and mRNA expression of LGR5 in rmRspo2-treated FLS and primary chondrocytes were significantly reduced by Rspo2-NAb or recombinant DKK1.