MicroRNAs in autoimmune thyroid diseases and their role as biomarkers

MicroRNAs (miRNAs) are small non-coding RNAs that regulate gene expression at the posttranscriptional level. They are emerging as potential biomarkers and as therapeutic targets for several diseases including autoimmune thyroid diseases (AITD). They control a wide range of biological phenomena, including immune activation, apoptosis, differentiation and development, proliferation and metabolism. This function makes miRNAs attractive as disease biomarker candidates or even as therapeutic agents. Because of their stability and reproducibility circulating miRNAs have been an interesting area of research in many diseases, and studies describing their role in the immune response and in autoimmune diseases have progressively developed. The mechanisms underlying AITD remain elusive. AITD pathogenesis is characterized by a multifactorial interplay based on the synergy between susceptibility genes and environmental stimulation, together with epigenetic modulation. Understanding the regulatory role of miRNAs could lead to identify potential susceptibility pathways, diagnostic biomarkers and therapeutic targets for this disease. Herein we update our present knowledge on the role of microRNAs in AITD and discuss on their importance as possible diagnostic and prognostic biomarkers in the most prevalent AITDs: Hashimoto's thyroiditis (HT), Graves' disease (GD) and Graves' Ophthalmopathy (GO). This review provides an overview of the state of the art in the pathological roles of microRNAs as well as in possible novel miRNA-based therapeutic approaches in AITD.