Fig. 5.

iOPN promoted STAT1-mediated immunosuppression in MSCs. a–d Vector-MSCs and iOPN-MSCs or WT-MSCs and OPN^−/−-MSCs were treated with or without TNF-α plus IFN-γ (10 ng/mL) for the indicated times. Cells were harvested, and OPN, NF-κB p65, STAT1, IKBα, phosphorylation of NF-κB p65, phosphorylation of STAT1 at Tyr701 and phosphorylation of IKBα were analyzed by immunoblotting analysis. Full-length blots are presented in Additional file 1: Fig. 5a-d. e–g Vector-MSCs and iOPN-MSCs were stimulated with TNF-α plus IFN-γ (10 ng/mL) for 12 h. The STAT1 inhibitor fludarabine (Flu, 2 μM) was then added to the culture medium of Vector-MSCs and iOPN-MSCs. The expression of iNOS was determined by quantitative real-time PCR (e), immunoblotting analysis (f) and flow cytometry (g). Full-length blots are presented in Additional file 1: Fig. 5f. h Vector-MSCs and iOPN-MSCs were pretreated with DMSO or fludarabine (Flu, 2 μM) for 6 h and then irradiated and cocultured with CFSE-labeled splenocytes activated by anti-CD3/CD28 antibodies for 3 days at a ratio of 1:20. CD4⁺ T cells and CD8⁺ T cells were stained for proliferation analysis by flow cytometry at the end of coculture, and the percentages of proliferating T cells are shown. The results are representative of three to six independent experiments. Values are shown as the mean ± SEM and statistical significance is indicated as *P < 0.05, **P < 0.01 and ***P < 0.001