microRNA expressions in CD4+ and CD8+ T-cell subsets in autoimmune thyroid diseases

Graves' disease (GD) and Hashimoto's thyroiditis (HT) are the most common autoimmune thyroid diseases (AITD). MicroRNAs (miRNAs) critically control gene-expression and play an important role in regulating the immune response. The aim of this study was to prove significant variations of key immunoregulatory miRNAs in peripheral blood mononuclear cells (PBMCs) and in CD4+ and CD 8+ T-cells of AITD patients. Selected miRNAs were amplified by a semiquantitative SYBR Green PCR from PBMCs and purified CD4+ and CD 8+ T-cells of 59 patients with GD, HT, and healthy controls. Both GD and HT showed significantly decreased miRNA 200a_1 and miRNA 200a2* in CD4+-T-cells (mean relative expression 12,57 in HT vs. 19.40 in control group (CG), p=0.0002; 12,10 in GD vs. 19.40 in CG, p=0.0002) and in CD8+-T-cells (13.13 in HT vs. 18,12 in CG, p=0.02; 11.66 in GD vs. 18.12 in CG, p=0.0002). GD and HT showed significantly decreased miRNA 155_2 and miRNA 155*_1 in HT in CD8+-T-cells (10.69 in HT vs. 11.30 in CG, p=0.01; 10.40 in GD vs. 11.30 in CG, p=0.005). This study confirms significant variations of miRNA200a and miRNA155 in patients suffering from GD and HT in vivo in CD4+ T-cells and CD8+ T-cells. These data may help to better understand the gene regulations in the causative cells causing these autoimmune processes. They extend our very limited knowledge concerning miRNAs in thyroid diseases.