MicroRNAs (miRNAs) are endogenous, noncoding, single-stranded RNAs of 19–24 nucleotides in length. They regulate gene expression by messenger RNA degradation and disruption of translation and are important in a wide range of physiological and pathological processes. They have been described as master regulators of gene expression, and are instrumental in regulating immune system development, normal immune function and autoimmunity. The two main characteristics of connective tissue diseases (CTD) is an imbalance between pro- and anti inflammatory processes leading to a prolonged inflammatory response and end organ damage. microRNAs play a fundamental role in both of these. Specific microRNA patterns are associated with various pro- or anti-inflammatory effects and abnormalities in some of these microRNAs have been described in CTDs. MicroRNAs have also been implicated in fibrosis and non-immune mediated mechanisms contributing to end organ damage.
MicroRNAs are attractive as biomarker candidates since they can be detected in a variety of biologic sources and there are various methods to reliably assess their expressions. Importantly, they are reasonably stable and appear to be resistant to differences in sample handling. Some microRNAs have already been validated as diagnostic or prognostic biomarkers in various malignant diseases, demonstrating their clinical utility. Preliminary studies in CTDs (lupus, Sjogren’s syndrome) have shown some encouraging results. Selected microRNAs correlated with disease activity in lupus and salivary gland inflammation in Sjogren’s syndrome. In a pilot study global microRNA profiling reliably distinguished minor salivary glands obtained from SS patients with low or high focus scores from each other as well as from control biopsies. Interestingly, inflammation and decreased salivary gland function were associated with different sets of miRNAs which targeted distinct pathologic pathways. Further studies designed to evaluate microRNAs as biomarkers of specific applications (diagnosis, prognosis, and disease activity) are needed to establish their true potential as biomarkers in CTDs.
Disclosure of Interest None Declared
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