MSC-secreted TGF-β regulates lipopolysaccharide-stimulated macrophage M2-like polarization via the Akt/FoxO1 pathway

Abstract

BackgroundAn uncontrolled inflammatory response is a critical pathophysiological feature of sepsis. Mesenchymal stem cells (MSCs) induce macrophage phenotype polarization and reduce inflammation in sepsis. MSC-secreted transforming growth factor beta (TGF-β) participated in the immune modulatory function of MSCs. However, the underlying mechanism of MSC-secreted TGF-β was not fully elucidated in regulation macrophage M2-like polarization.MethodsThe paracrine effects of MSCs on macrophage polarization were studied using a co-culture protocol with LPS-stimulated RAW264.7 cells/mouse peritoneal macrophages and MSCs. The effect of TGF-β in the co-culture system was blocked by the TGF-β receptor inhibitor. To determine the role of MSC-secreted TGF-β, we used recombinant TGF-β to culture with LPS-stimulated RAW264.7 cells. In addition, we employed antibody microarray analysis to determine the mechanisms of MSC secreted TGF-β on LPS-stimulated RAW264.7 cell/mouse peritoneal macrophage M2-like polarization. Furthermore, we used an Akt inhibitor and a FoxO1 inhibitor to inhibit the Akt/FoxO1 pathway. The nuclear translocation of FoxO1 was detected by Western blot.ResultsMSCs induced LPS-stimulated RAW264.7 cell/mouse peritoneal macrophage polarization towards the M2-like phenotype and significantly reduced pro-inflammatory cytokine levels via paracrine, which was inhibited by TGF-β receptor inhibitor. Furthermore, we found that MSC-secreted TGF-β enhanced the macrophage phagocytic ability. The antibody microarray analysis and Western blot verified that TGF-β treatment activated the Akt/FoxO1 pathway in LPS-stimulated macrophages, TGF-β-induced FoxO1 nuclear translocation and obviously expressed in the cytoplasm, the effects of TGF-β regulatory effects on LPS-stimulated macrophage were inhibited by pre-treatment with Akt inhibitor and FoxO1 inhibitor.ConclusionsTGF-β secreted by MSCs could skew LPS-stimulated macrophage polarization towards the M2-like phenotype, reduce inflammatory reactions, and improve the phagocytic ability via the Akt/FoxO1 pathway, providing potential therapeutic strategies for sepsis.

Are Liver Pericytes Just Precursors of Myofibroblasts in Hepatic Diseases? Insights from the Crosstalk between Perivascular and Inflammatory Cells in Liver Injury and Repair

“…These myofibroblast-like cells produce the active form of TGF-β, which, together with neutrophil-derived ROS [106], contributes to macrophage polarization toward a TGF-β-producing, pro-regenerative phenotype (Figure 2). The main putative pathway involved with an M2-like polarization is Akt [102], including Akt/SNAIL [103] and Akt/FoxO1 [107]. Myofibroblasts expressing high levels of p75NTR undergo apoptosis triggered by NGF, which is produced by cleavage of parenchymal cell-derived pro-NGF operated by macrophage-derived MMP7.…”

MSC-derived miR-181b Overexpressing Exosomes Enhanced Osteointegration by Enhancing M2 Polarization of Macrophages via Targeting the PRKCD/AKT Pathway

“…Since the inhibition of Akt abrogates the upregulation of M2 related genes, the activation of Akt is essential for M2 polarization [38]. Feng Liu et, al reported that TGF-β secreted from MSC promoted RAW264.7 to M2 phenotype [39]. Guohua Wang et, al found that increased expression of glycogen synthase kinase 3 beta (GSK3β) inhibited the activation of phosphatase and tensin homologue (PTEN), thus enhancing PI3K/Akt pathway, further enhancing microglia to M2 polarization [40].…”

<p>Growth Factor Gene-Modified Mesenchymal Stem Cells in Tissue Regeneration</p>

“…These secreted compounds can inhibit a range of processes such as apoptotic cell death and fibrosis, 11 in addition to being able to drive angiogenesis, 12,13 and to regulate the immune response. 14,15 Without any exogenous manipulation, MSCs achieve limited therapeutic efficacy due to their poor survival and limited GF secretion upon transplantation. The therapeutic efficacy of MSCs ultimately depend upon the number of cells implanted, the function of these cells, when they are administered, and what condition they are being used to treat.…”