Expression, regulation and function of microRNAs in multiple sclerosis.

MicroRNAs (miRNAs) are single-stranded 19-25 nucleotide-long RNAs and have an important role in post-transcriptional gene silencing. It has been demonstrated that miRNAs are dysregulated in patients with multiple sclerosis (MS). For instance, miR-21, miR-142-3p, miR-146a, miR-146b, miR-155 and miR-326 were up-regulated in both peripheral blood mononuclear cells (PBMCs) and brain white matter lesions from MS patients and mouse model as well. These up-regulated miRNAs may be used as a signature for MS and play critical roles in MS pathogenesis. Moreover, miR-15a, miR-19a, miR-22, miR-210 and miR-223 were up-regulated in both regulatory T cells (Tregs) and other samples such as plasma, blood cells, PBMCs and brain white matter tissues from MS patients, suggesting that these up-regulated miRNAs and Tregs may also play a role in MS pathogenesis. Contrarily, other miRNAs such as miR-15a, miR-15b, miR-181c and miR-328 were down-regulated in MS. Drugs such as interferon-β and glatiramer acetate for MS treatment may regulate miRNA expression and thus have benefits for MS patients. The dysregulated miRNAs such as miR-155 and miR-326 may be used as diagnostic markers and therapeutic targets for MS.