Human Amniotic Mesenchymal Stem Cells Inhibit aGVHD in Humanized NPG Mice by Regulating Balance of Treg Versus T Effector Cells

Background: Acute graft versus host disease(aGVHD) occurs when immunocompetent T cells in the donated tissue recognize the recipient as foreign after allo-HSCT, which can severely affect quality of life. Although previous studies indicated that MSC may be a salvage therapeutic agent for aGVHD, the mechanism is not yet fully clear. The aim of this study was to explore the therapeutic efficacy and underlying mechanisms of hAMSCs transplantation for humanized aGVHD mouse model.Methods: We established a novel xenogeneic (xeno)-aGVHD humanized mouse models by transplanting purified human T cells from peripheral blood into immunodeficient NOD-PrkdcscidIl2rγnull (NPG) mouse. In those mouse models, lymphocyte infiltration of target organs was detected by HE staining method and immunohistochemistry respectively. The biological characteristics of hAMSCs were investigated. hAMSCs labeled with GFP were administered to NPG mice to explore the homing ability of hAMSCs. Mice are divided into normal(control) group, aGVHD group and hAMSCs treatment group. After 3 days of injection of PBMC, hAMSCs and PBS were given into the different groups. T effector and Treg cells levels of each group in target organs were detected by flow cytometry and cytometric bead array (CBA).Results: We successfully established xenogeneic aGVHD “humanized model” by using NOD-PrkdcscidIl2rγnull (NPG) mice, which showed lymphocytes infiltration in the liver, spleen and lung. hAMSCs therapy improved systemic inflammation and inhibited aGVHD in humanized mouse through reduced villous blunting and lymphocyte infiltration into the lamina propria of the gut while reducing vascular endothelialitis and lymphocyte infiltration into the parenchyma of the liver and lung. In addition, hAMSCs suppresses xenogenesis CD3+/CD4+ and CD3+/CD8+ T cell concentration and increases the proportion of Treg cells. Our data also show that hAMSC can reduce the level of IL-17A, INF-γ, TNF and IL-2 that involved in the pathogenesis of aGVHD target organs.Conclusions: NPG murine environment is capable of activating human T cells to produce aGVHD pathology to mimic aGVHD in humans. hAMSCs controlled aGVHD by decreasing inflammatory cytokine secretion within target organs through modulating balance of Treg versus T effector cells in humanized mice.