Role of bone marrow mesenchymal stem cells in different concentrations on regulatory T cell/T-helper cell 17 balance in rats

Abstract

To explore the effects of bone marrow mesenchymal stem cells (BMSCs) in different concentrations on the balance of regulatory T cell/T-helper cell 17 (Treg/Th17). BMSCs were isolated from SPF grade male Wistar rats with age of 3 weeks old and weight of 50 g. BMSCs were cultured and identified when they were expanded to the 4th generation. CD4+ T lymphocytes were isolated from SPF grade male Wistar rat with age of 6 weeks old and weight of 200 g and assayed for cell purity by flow cytometry. BMSCs were divided into 0.5-fold concentration group, basal concentration group, 2-fold concentration group and 4-fold concentration group by their concentrations of 1×105/well, 2×105/well, 4×105/well and 8×105/well, which were cultured with CD4+ T lymphocytes for 72 hours, respectively. Then the proportion of Treg cells and Th17 cells in each group was detected by flow cytometry, and cytokines were detected by cytometric bead array. The purities of BMSCs and CD4+ T lymphocytes were both higher than 95%. In the co-culture of BMSCs and CD4+ T lymphocytes, the proportions of Treg cells were statistically different among different concentration groups of BMSCs (F = 10.071, P = 0.001), in which BMSCs in 2-fold concentration group had the strongest ability to promote the Treg cells proliferation. The proportion of Treg cells in 2-fold concentration group was significantly higher than that in 0.5-fold concentration group, basal concentration group and 4-fold concentration group [(9.24±2.68)% vs. (3.87±0.38)%, (5.16±1.69)%, (3.86±0.36)%, all P < 0.01]. The level of interleukin-10 (IL-10) was lowest in 0.5-fold concentration group, and it was significantly lower than that in basal concentration group, 2-fold concentration group and 4-fold concentration group (ng/L: 39.80±14.48 vs. 148.43±64.49, 156.40±59.27, 126.92±42.95, all P < 0.05). Transforming growth factor-β (TGF-β) was the highest in basal concentration group, and it was significantly higher than that in 0.5-fold concentration group, 2-fold concentration group and 4-fold concentration group [ng/L: 3.17 (1.88, 5.74) vs. 0.71 (0.32, 1.38), 1.22 (0.47, 2.97), 0.52 (0.37, 1.23), all P < 0.05]. The proportions of Th17 cells were statistically different among the different concentration groups (F = 21.069, P = 0.000), with the highest proportion in basal concentration group which was significantly higher than that in 0.5-fold concentration group or 4-fold concentration group [(0.89±0.08)% vs. (0.64±0.15)%, (0.37±0.10)%, both P < 0.01], but no significant difference was found as compared with 2-fold concentration group [(0.83±0.06)%, P > 0.05]. However, the expressions of IL-17 and IL-6 were not different among the different concentration groups respectively (IL-17: χ2 = 0.550, P = 0.760; IL-6: χ2 = 0.010, P = 0.995). BMSCs in moderate concentrations [(2-4)×105/well] could promote proliferation both in Treg cells and Th17 cells, but no change could be found in higher concentrations of BMSCs (8×105/well). However, the changes in related cytokines were not synchronized with Treg/Th17 cells.