BackgroundOur previous studies found that mesenchymal stem cells (MSCs) can ameliorate experimental autoimmune uveitis (EAU) and reduce tissue impairment.Its mechanism is still pending.

ObjectiveThis study was performed to investigate the effects of MSCs on T cell subsets and antigen presenting cells (APCs) in EAU rats.

MethodsMSCs were isolated from bone marrow of six male Wistar rats and cultured by plastic adherence method.Twelve female Lewis rats were assigned randomly into MSCs group and PBS group.EAU rat model was induced by immunization with 200 μl emulsion containing 30 μg interphotoreceptor retinoid-binding protein (IRBP) 1177-1191 polypeptide fragment R16 and complete Freund adjuvant (CFA). The eye manifestations of the rats were observed and scored under the slit lamp microscope after modeling.The R16-immunized rats were treated intravenously with 5×10 ⁶/ml MSCs for 3 consecutive days from day 9 to 11 after modeling in the MSCs group, and the equivalent volume of PBS was used with the same way in the PBS group.Fifteen days after modeling, the spleens and draining lymph nodes were collected to evaluate the proportion of interferon-γ (IFN-γ) positive CD4 ⁺ T cells, interleukin-17(IL-17)positive CD4 ⁺ T cells and forkhead helix transcription factor p3 (Foxp3) positive CD4 ⁺ T cells by flow cytometry.The T cells and APCs from the different groups were cocultured and divided into PBS cocultured group, MSCs cocultured group, PBS-MSCs cross-cultured group and MSCs-PBS cross-cultured group under the stimulation of R16 at the concentration of 0.3, 1.0 or 10.0 μg/ml, and the proliferation indexes of the T cells in different groups were assayed by 5-bromodeoxyuridine (BrdU) Elisa kit.The use of experimental animals complied with the regulations on the management of experimental animals promulgated by the national science and technology commission.

ResultsThe ocular surface inflammatory scores of 11, 12, 13 and 14 days after modeling in the MSCs group were significantly lower than that in the PBS group ( t=3.825, 5.100, 4.250, 3.400, all at P<0.05). Compared with the PBS group, the proportions of IFN-γ positive CD4 ⁺ T cells in spleen and draining lymph notes were considerably decreased in the MSCs group ( t=5.651, 4.376, both at P<0.05), so were the IL-17 ⁺ CD4 ⁺ T cells ( t=3.300, 4.925, both at P<0.05). However, the proportions of Foxp3 ⁺ CD4 ⁺ T cells in spleen and draining lymph notes were statistically raised in the MSCs group compared with the PBS group ( t=-5.172, -2.825, both at P<0.05). The proliferation index of T cells increased with the rise of R16 dose in the PBS cocultured group, and the proliferation indexes were all declined in the MSCs cocultured group compared with the PBS cocultured group under the stimulation of 0.3, 1.0 and 10.0 μg/ml of R16 ( P=0.027, 0.000, 0.000). In addition, significant reduces of proliferation indexes of T cells were seen in the PBS-MSCs cross-cultured group and MSCs-PBS cross-cultured group in comparison with the PBS cocultured group when stimulated by 1.0 μg/ml and 10.0 μg/ml R16 (1.0 μg/ml R16: P=0.001, 0.000; 10.0 μg/ml R16: P=0.000, 0.000).

ConclusionsMSCs can ameliorate EAU by inhibiting the functions of antigen-specific T cells and APCs and up-regulating T regulatory cells in EAU rats.