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

Abstract Background: Acute graft versus host disease (aGVHD) remains a leading cause of transplant-related mortality following allogeneic haematopoietic cell transplantation(allo-HCT). Although previous studies indicated that mesenchymal stem cells (MSCs) may be a salvage therapeutic agent for aGVHD, the mechanism is not yet fully clear. Human amniotic mesenchymal stem cells (hAMSCs) is a novel MSCs, compared with bone marrow mesenchymal stem cells, it has the advantage of being non-invasive, and also has stronger proliferation ability than that of BM-MSCs and equivalent immune regulation ability as BM-MSCs. The aim of this study was to explore the therapeutic efficacy and underlying mechanisms of human amniotic mesenchymal stem cells transplantation for the humanized aGVHD mouse model.Methods: We established a humanized aGVHD mouse model by transplanting human peripheral blood mononuclear cells (PBMCs) into NOD-PrkdcscidIL2rγnull (NPG) mice, hAMSCs collected from discarded placenta of healthy pregnant women after delivery. Mice were divided into control group (untreated), aGVHD group, and hAMSCs treatment group, the hAMSCs labeled with GFP were administered to aGVHD mice to explore the homing ability of hAMSCs. T effector and Treg cell levels and cytokines of each group in target organs were detected by flow cytometry and cytometric bead array (CBA) respectively.Results: We successfully established a humanized aGVHD mouse model using NPG mice. The hAMSCs have the ability to inhibit aGVHD in this mouse model 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. hAMSCs suppressed xenogenesis CD3+CD4+ T and CD3+CD8+ T cell expression and increased the proportion of Treg cells, and besides, hAMSCs can reduce the levels of IL-17A, INF-γ, TNF, and IL-2 in aGVHD target organs.Conclusions: The NPG murine environment was capable of activating human T cells to produce aGVHD pathology to mimic aGVHD as in humans. The hAMSCs controlled aGVHD by decreasing inflammatory cytokine secretion within target organs by modulating the balance of Treg and T effector cells in humanized mice.