MicroRNAs in Sjögren's syndrome as a prototypic autoimmune disease.

MicroRNAs are endogenous non-coding RNAs, approximately 22 nucleotides in length. They regulate gene expression and are important in a wide range of physiological and pathological processes. MicroRNA expression is tightly regulated during hematopoiesis and lymphoid cell differentiation and disruption of the entire microRNA network or selected microRNAs may lead to dysregulated immune responses. Abnormalities in microRNA expression related to inflammatory cytokines, Th-17 and regulatory T cells as well as B cells have been described in several autoimmune diseases. Sjogren's syndrome is characterized by features of systemic autoimmunity and chronic inflammation and dysfunction in exocrine organs. Its clinical characteristics along with the relatively easy access to the target tissue and its product makes Sjögren's syndrome appealing to study many aspects of microRNAs in a systemic autoimmune disease, such as their potential as diagnostic or prognostic biomarkers and their role in pathogenesis of autoimmunity, inflammation or organ dysfunction. Encouraging preliminary data from pilot studies in Sjogren's syndrome demonstrate the potential of microRNAs as putative diagnostic and prognostic biomarker candidates which should be tested in larger more definite studies. Combining the comparison of microRNA expression profiles between various clinical subsets of Sjögren's syndrome with bioinformatic modeling tools may predict formerly unsuspected pathways which may contribute to the disease process and lead to the generation of testable novel hypothesis of pathogenesis.