AbstractIntroductionBone marrow mesenchymal stem cells (BMMSCs) are a heterogeneous population of postnatal precursor cells with the capacity of adhering to culture dishes generating colony-forming unit-fibroblasts (CFU-F). Here we identify a new subset of BMMSCs that fail to adhere to plastic culture dishes and remain in culture suspension (S-BMMSCs).MethodsTo catch S-BMMSCs, we used BMMSCs-produced extracellular cell matrix (ECM)-coated dishes. Isolated S-BMMSCs were analyzed byin vitrostem cell analysis approaches, including flow cytometry, inductive multiple differentiation, western blot andin vivoimplantation to assess the bone regeneration ability of S-BMMSCs. Furthermore, we performed systemic S-BMMSCs transplantation to treat systemic lupus erythematosus (SLE)-like MRL/lprmice.ResultsS-BMMSCs are capable of adhering to ECM-coated dishes and showing mesenchymal stem cell characteristics with distinction from hematopoietic cells as evidenced by co-expression of CD73 or Oct-4 with CD34, forming a single colony cluster on ECM, and failure to differentiate into hematopoietic cell lineage. Moreover, we found that culture-expanded S-BMMSCs exhibited significantly increased immunomodulatory capacitiesin vitroand an efficacious treatment for SLE-like MRL/lprmice by rebalancing regulatory T cells (Tregs) and T helper 17 cells (Th17) through high NO production.ConclusionsThese data suggest that it is feasible to improve immunotherapy by identifying a new subset BMMSCs.