Methylome characterization of CD4+ T cells in multiple sclerosis — Establishing a role for miR-21 in autoimmune disease

expression of Ly6C and Ly6G, very important in infectious, autoimmune and tumor models. The present work will further characterize the potential role of miR-223 in the EAE model and MS. First we found an upregulation of miR-233 in the Peripheral Blood Mononuclear Cell (PBMC) of 20 MS samples vs. 20 controls (fold change over controls 1.64 ± 1.25 vs. 1.20 ± 0.95, P = 0.018). This result was confirmed in a different cohort of subjects, including 15 untreated MS subjects (population from Italy: 11 RRMS, 4 PPMS) and 12 healthy controls. In this cohort, miR-233 was upregulated in MS vs. control subjects (fold change over controls 0.81 ± 0.65 vs. 0.40 ± 0.26, P = 0.010). We also performed several active EAE experiments in miR-223 knockout (miR-223 KO) mice and littermate control mice. MiR-223 KO mice developed a significantly less severe disease (P b 0.0001 by two-way ANOVA) with a significantly higher percentage of PMN-MDSC (CD11b/Ly6G positive cells) and MO-MDSC (CD11b/Ly6C positive cells) in the spleens and spinal cords compared to control mice. We found also that MO-MDSC from miR-223 KO mice had greater immune-suppressive effects on CD4 T cell proliferation than controls in antigen T cell stimulatory conditions. It is established that MO-MDSCs inhibit CD4 and CD8 T cell proliferation mostly via ARG1 action. ARG1 was promptly upregulated in MO-MDSC from miR-223 KO cells corresponding to their high immunosuppressive function. These results demonstrate altered levels of miR 223 in the PBMC of MS patients and suggest that miR-223 plays a role in EAE. This may lead to the identification of new disease biomarkers of therapeutic targets.