LAUSR

The role of IL‐10‐producing regulatory B cells in inflammatory diseases has recently gained substantial attention. Here, we evaluated the function of mouse bone marrow mesenchymal stem cell‐derived exosomes (BMMSC‐Exos) and their effect on B‐cell differentiation. This study aimed to establish an association between BMMSC‐Exos and purified B cells and further explored the anti‐inflammatory effect of B10 cells. The expression of inflammatory factors, such as IL‐1β, TNF‐α, and bone metabolism‐related factors, including RANKL, OPG, and secreted IL‐10, was investigated by RT‐qPCR and ELISA. Populations of CD1dhighCD5+ B cells were analyzed by flow cytometry and immunofluorescence. Cell viability was assessed by CCK8 assay. The results showed that when B cells were separated from BMMSCs by Transwell, IL‐1β, TNF‐α, and RANKL were downregulated, whereas IL‐10, OPG/RANKL, and CD1dhighCD5+ Breg proportion were upregulated in the cocultured groups. Conversely, when B cells were cultured with BMMSC‐Exos, increasing concentrations of exosomes increased the proportion of CD1dhighCD5+ and IL‐10+CD45+ Bregs; however, the secretion of both pro‐inflammatory cytokines and IL‐10 were decreased. We found that BMMSC‐Exos induce the differentiation of B cells toward the CD1dhighCD5+ and IL‐10+CD45+ Breg phenotype but cannot increase the secretion of IL‐10 in vitro.