Mechanism Of Mesenchymal Stem Cell Derived From Wharton's Jelly To Inhibit Xenogeneic Graft-versus-host Disease

Objective:The study was aimed to investigate the immunomodulatory effects of mesenchymal stem cell(MSC) derived from Wharton's jelly.Methods:In this study,a method was developed to culture MSC derived from Wharton's jelly fragments.Cells were authenticated in common morphology,immune phenotype and capabilities of differentiation.Xenogeneic graft versus host disease (X-GVHD) model was established by intravenously infusing cord blood into NOD/SCID mice.MSC were intravenously co-infused into mice of X-GVHD model. Weight,blood cell count and pathologic changes were observed to assure the effect of MSC and further experiments were performed to investigate the mechanism through which MSC inhibit X-GVHD.Results:MSCs from Wharton's jelly were cultured and expanded.The cells population exhibited homogenous surface antigen profile,which are non-hematopoitic(CD45 and CD34),non-endothelial(CD31),only express some adhesive molecules(CD29,CD44,CD73,CD105).The cells expressed HLA-ABC and PD-L1, rather than CD80,CD86 or HLA-DR.The cells presented in vitro multipotential differentiation capacities along osteocyte and adipocyte lineages.Using a cord blood transfusion NOD/SCID model across the major histocompatibility barrier,we found that MSC alleviated X-GVHD symptom(weight loss,hacked and diarrhea) and ameliorated the pathologic damages(lung,liver,kidny and spleen) of the X-GVHD mice.Although MSC reduced the engraftment of human cells in the peripheral blood,spleen and bone marrow, it significantly reduced the engraftment and proliferation of human T cells in peripheral blood,spleen and bone marrow,and gave rise to the elevation of CD4~+ to CD8~+ ratio.Dentritic cells and T cells were the main effect cells during GVHD process. Monocytes induced dentritic cells cultured with MSC failed to show regular upregulation of maturation markers CD83,CD86 and HLA-DR,the cytokine IL-12p70 secretion and cytotoxic T cells activity(p＜0.05).In the mitogen-activated T cells system,less T-cells were in G2+S phase by MSC.MSC increased the activation of Th cells,decreased the activation of Tc cells,and upregulated Th to Tc ratio.MSC had the ability to inhibit mitogen-activated T cells and Th and Tc cells proliferation.MSC increased FoxP3 mRNA expression.The cytokines TGF-β1,IL-6 expressed by MSC were increased as compared with control,but IL-10 expression reduced in MSC(p＜0.05).Cell-to-cell contact showed merely influence on T cells by the effect of MSC.Conclusions:This work demonstrates that the immunosuppressive effect of MSC derived from Wharton's jelly:UCB-NOD/SCID mice treated with a single dose of MSC was a marked decrease X-GVHD symptom.Two factors played a role in the inhibition of X-GVHD by MSCs.MSCs reduced the upregulation of dentritic cells maturation markers CD83,CD86 and HLA-DR,the cytokine IL-12p70 secretion and cytotoxic T cells activity.MSC increased the activation of Th cells,decreased the activation of Tc cells,and upregulated Th to Tc ratio.MSCs had the ability to inhibit mitogen-activated T cells and Th and Tc cells proliferation,and increased inhibitory cytokines secretion.