Immunosuppressive effects and mechanism of rat bone marrow mesenchymal stem cells on allogeneic T lymphocytes
Objective To observe the role of nitric oxide(NO) in the immune regulatory effect of bone marrow mesenchymal stem cells(MSCs). Methods Bone marrow MSCs were isolated from Lewis rats by adherence screening. Concanavalin A (ConA) was adopted as the stimulator and T-lymphocyte isolated from peripheral blood of SD rats as the reactive cells. The changes of the ability of T-lymphocyte proliferation, when co-cultured with MSCs, were measured by CCK-8 assay. The inducible nitric oxide synthase (iNOS) mRNA and protein expression on MSCs and were detected by RT-PCR, Western blot. The contents of nitrites and the levels of Th1 type cytokine IFN-γand Th2 type cytokine IL-4 were measured by Griess test and ELISA respectively, in the co-cultured supernatant. Results T-lymphocyte proliferation was inhibited by co-cultured MSCs, which was concentration-dependent. In this study, the inhibition was most obviously group[ (79.03 ± 1.70)% ] (P ＞ 0.05 ). The I NOS mRNA expression, protein and nitrite levels were signifigroups, the proliferation rate of T-lymphocyte recovered. The content of IFN-γwas increased with the ratio decline of MSCs in the experimental group and IL-4 in each group has no significant difference( P ＞ 0.05 ).Conclusion MSCs inhibited T-lymphocyte proliferation by influencing Th1/Th2 balance, and the secretion of soluble factor NO, which secreted by MSCs, may plays an important role in the immune regulation. 
 
Key words: 
Mesenchymal stem cells;  Nitric oxide;  Th1/Th2;  Immune regulation