**3. Recent Progress of miRNAs in Hypertension**

miRNAs (18–24 bp) are master gene regulators controlling the expressions of specific genes by their binding to the 3 untranslated region (UTR) of a messenger RNA (mRNA), which triggers either repression or degradation of the translation mechanism, and thus gene expression. A single miRNA regulates one to several hundred genes, and a single gene could be regulated by more than one miRNA. miRNAs can be sourced from tissues, urine, serum, plasma and blood cells (which include peripheral blood mononuclear and vascular endothelial cells). The accessibility of miRNA from serum, plasma or urine stems from studies that validated the presence of circulating miRNAs packaged in exosomes, microvesicles or apoptotic bodies [34–37]. The functions of the circulating miRNAs are mainly to communicate to neighboring or remote target cells and to provide gene expression regulation. An example for this is the communication between endothelial cells and the VSMCs, via the circulating miRNAs in these mentioned extracellular vesicles [34]. The various miRNAs that will be described are also listed in Table 1.
