The Effect Of Bone Marrow Mesenchymal Stem Cells On T Lymphocytes And Dendritic Cell And Its Application In Islets Transplantation

Objective:a).to clarify the immunoregulatory mechanism of bone marrow mesenchymal stem cells(BMSCs) by studying the effect of BMSCs on cytokine secretion,cell cycle,and proliferation of different allogeneic T lymphocyte subsets and the effect on the differentiation, function,and maturation of dendritic cells,b).to observe the ability of BMSCs inhibiting allo-reaction and prolong the survival of allo-islets by combining BMSCs with islets transplantation.Methods:The BMSCs from Balb/C mice were isolated,purified and identified.T lymphocytes were enriched with C57BL/6 mouse spleens using immunomagnetic beads.BMSCs were co-cultured with T lymphocytes or bone marrow cells(BMCs) from C57BL/6 mice at different mixing ratio in vitro.The proliferation of T lymphocytes was measured using MTT.The secretion of IL-4,IFN-γand cell cycle were detected by a flow cytometry(FCM).The phenotype and the endocytosis capacity of dendritic cells were also detected by a flow cytometry. Meanwhile,the IL-12 level in culture supernatant was measured by ELISA.Islets from Balb/c mice were isolated,purified and identified.Then they were transplanted with or without BMSCs into C57BL/6 mice with type 1 diabetes induced by streptozotocin(STZ).The blood glucose level was measured at different time points.The effect of BMSCs on T lymphocytes in vivo was studied by FCM analysis.Results:The proliferation of T lymphocyte induced by alloantigen was clearly inhibited by BMSCs.Further more,BMSCs reduced the secretion of IFN- within subsets CD4⁺,CD8⁺ T lymphocytes,but have no effect on IL-4 level.This phenomenon was also clearly observed for CD4⁺CD45RB^High,CD4⁺CD45RB^Low and CD8⁺CD45RB^High,CD8⁺CD45RB^Low subsets,the amount of reduction was different for different subsets.When the ratio of BMSCs verse BMC reached 1:10,the expression of CD11c,CD14,CD83,CD86,I-Ab were clearly reduced.For dendritic cells,Endocytosis of Dextran and secretion of IL-12 were also decreased.Despite the function of T lymphocytes was suppressed,BMSCs didn't prolong the survival of islets and induce immunotolerance. Conclusion:BMSCs suppress immunoreaction by inhibiting proliferation and reducing cytokine secretion for different subsets of T lymphocytes.In vitro,BMSCs inhibit allo-BMCs- derived dendritic cells differentiation,maturation and function.Despite the function of T lymphocytes were suppressed in vivo,BMSC could not induce immunotolerance and prolong the survival of transplanted islets.