Analytical aspects of microRNA in diagnostics: a review

MicroRNAs (miRNA) are short (∼22 nucleotides) non-coding RNA molecules that regulate gene expression at the post-transcriptional level. Their expression is specific to cells and tissues and is temporally regulated. miRNAs are known to be involved in developmental and physiological processes, and their dysregulation leads to development of diseases. Since their profiles reflect pathological processes, miRNAs have recently been proposed as being useful in diagnostics as biomarkers of the onset, prognosis and risk of diseases, as well as in the classification of different types of cancer. The establishment of miRNA profiles that are representative of diseases and the detection of different types and levels of miRNA in samples are therefore critical milestones in diagnostics. miRNAs can be detected in blood and body fluids as well as in tissues, thus making non-invasive collection of samples possible. For a method to be useful in diagnostics, it should be simple, inexpensive and highly sensitive. Here, we will review current methods of detecting miRNAs and indicate the advantages and disadvantages of each techniques. We will then summarize some of the clinical evidence for the potential application of miRNAs as biomarkers in diagnostics. We conclude providing some general perspectives on the use of miRNAs in clinical situations, including therapeutic applications.