ABSTRACT

Noncoding ARN, including miRNAs, constitutes an upper level of regulation in gene expression, increasing the complexity of cell function regulation. Besides epigenetic modification of DNA, miRNAs are key mediators of cell homeostasis and, therefore, deregulation of miRNAs is at the bases of pathology. In fact, underlying most of the severe diseases have been demonstrated alterations in miRNAs. Although miRNAs are generated in the nucleus and act in the cytoplasm, they can be secreted by the cells to the extracellular environment, constituting an important cell–cell method of communication. Being secreted, they can also be detected in body fluids. In contrast to longer RNAs, miRNAs are extremely stable and protected against RNAse activity. Taking into account all these features, miRNAs appear as suitable molecules to be identified as biomarkers of diseases. In fact, they can be easily detected by qRT-PCR in many types of samples—including tissue, cells, blood, urine and saliva—allowing the prognosis, diagnosis and monitoring of diseases using minimally invasive methods and, hence, are emerging as very useful tools in personalized medicine. All these aspects are discussed in this section.