NLRP3 and rheumatoid arthritis: Altogether, our results suggest that hUCB-MSCs can effectively regulate circulating macrophages in RA patients through the preferential induction toward M2 phenotype, as well as the inhibition of NLRP3 inflammasome-mediated IL-1β secretion, implying that these immune-balancing effects enable hUCB-MSCs to be a promising therapeutic option for RA treatment.