Circulating microRNAs in Disease Diagnostics and their Potential Biological Relevance

Gazouli, Maria, Maria Gazouli

Inflammatory bowel diseases (IBD) are chronic, idiopathic, polygenic diseases with significant genetic heterogeneity. The two major types of IBD are Crohn's disease (CD) and ulcerative colitis (UlC). It is well known that chronic intestinal inflammation results from the interplay of genetic, immunologic, and environmental factors, so the failure to properly downregulate nonspecific inflammation started by an environmental trigger may lead to the development of IBD. Recent studies indicate several microRNAs (miRNAs) as regulators of important pathways of the immune response and immune cell development, which are crucial to the pathogenesis of a variety of inflammatory diseases, including IBD. Additionally, miRNAs are shown to be crucial regulators of intestinal epithelial barrier function, colonic epithelial cell-derived chemokine expression, and autophagy mechanisms. About 100 miRNAs have been indicated to exhibit altered expression in tissues and blood for UlC and CD, when compared to healthy normal controls. Taking into consideration that to date the diagnosis and follow-up of IBD are performed by invasive colonoscopy, it is well suggested that circulating microRNAs might be promising noninvasive biomarkers for IBD. Therefore, recent studies have focused on comparing miRNAs expression profile in tissue to miRNAs profile in blood, in order to introduce the analysis of circulating microRNAs in the future clinical practice. In this chapter, the role of microRNAs in IBD and the most promising circulating microRNAs will be discussed that could be used as noninvasive biomarkers for IBD diagnosis.