CD146+ umbilical cord mesenchymal stem cells exhibit higher immunomodulatory activity and therapeutic efficacy in septic mice

Abstract: Background Several animal studies have shown that MSCs can significantly improve the survival of sepsis. CD146 + MSCs, a subpopulation of mesenchymal stem cell (MSCs), correlate with high therapeutic and secretory potency. However, their therapeutic effect on sepsis and detail mechanisms about regulation of macrophage have not been explored. Methods The effect of CD146+/-MSCs on differentiation of Treg,Th1,Th17 subsets was evaluated by flow cytometry. The paracrine effects of CD146+/-MSCs on RAW264.7 phagocytosis and LPS-stimulated polarization were studied using a co-culture protocol. In addition, we employed Luminex bead array and RNA sequencing analysis to determine the mechanisms of MSCs on LPS-stimulated RAW264.7. The Arg1 protein was detected by Western blot. CD146+/-MSCs were injected into LPS-induced sepsis mice by tail vein. The treatment effect was assessed by organ HE staining, T-cell subsets, cytokine in plasma, peritoneal macrophages, infiltrating monocytes subpopulations. Results In vitro, CD146 + MSCs could significantly increase the Treg cells proportion in PBMCs stimulated by PHA. Both CD146+/-MSCs can reduce the proportion of Th1 and Th17 subsets. CD146 + MSCs can increase the phagocytic rate of raw264.7. The RNA sequencing data indicated that UC-MSCs therapy improved LPS-induced raw264.7 through PPAR and cytokine receptor pathways. The differences between the CD146 + and CD146- groups were clustered in arginine metabolism. CD146 + MSCs decreased NO production and increased agr1 expression. CD146 + MSCs secreted higher IL15,IFNγ, VEGF and lower IL1β, IL8 under LPS. In vivo, CD146+/-MSCs treatment can improve the pathological damage of organs caused by LPS. CD146+/-MSCs therapy significantly decreased CD4 expression, increased CD8 expression, and decreased CD4/CD8 ratios, which was similar to that in the normal group. CD146+/-MSCs can reduce IL1β,IL6 content in plasma. The level of IL10 at 24h and CXCL1 at 12h in CD146 + MSCs group was the highest. The phagocytic capacity of peritoneal macrophages in CD146 + MSCs group was better than that in CD146- group and LPS group at 12h. The CD146+/-MSCs had significantly reduced numbers of monocytes in the peritoneal cavity. CD146 + MSCs enhanced the ratios of CD11b + Ly6C^lo reparative monocytes and CD11b + Ly6C^hi inflammatory monocytes until 24h. Conclusions Compared with CD146-MSCs, CD146 + MSCs can accelerates the end of the inflammatory response and have robust anti-inflammatory effects, by increasing the Treg cells, promoting macrophage phagocytosis, enhancing the reparative macrophage, secreting more VEGF, etc.