MicroRNA: a clinician's view of the state of the problem. Part 1. History of the issue

A large amount of genetic information is localized in microRNAs which are a class of non-coding RNAs formed from longer RNA precursors, usually having a length of 19-24 nucleotides and a specific hairpin structure. Although microRNA studies have been started relatively recently, there is no doubt that they play an important role in regulating gene expression at the post-transcriptional level in embryonic development, and are also involved in maintaining the normal functions of adult cells. For the first time, microRNA was discovered in the study of free-living nematodes Caenorhabditis elegans and then a new mechanism for suppressing expression using antisense RNA was discovered. MicroRNA may be part of protein-coding transcripts or may be located in the intergenic genome regions. Changes in the functional activity and number of microRNAs can lead to diseases such as oncological, cardiovascular, gynecological, and neurological. MicroRNA is also involved in the process of neurodegeneration and the development of mental diseases. Since part of the microRNA is specific to certain tissues and/or stages of development of the organism, microRNA molecules can be considered as a promising diagnostic tool. Among the advantages of these biomarkers are the possibility of detecting pathology in the latent stage, the low invasiveness of studies and resistance to destructive factors. At the same time, microRNAs can be detected in various biological fluids: blood serum, urine, seminal fluid, saliva, breast milk. Currently, the possibilities of using microRNAs in targeted therapy are widely discussed in connection with the possibility of regulating the expression of genes with undesirable properties or overexpression of microRNA inhibitors to prevent the negative effects of microRNAs that cause the development of the disease. The first part of the review discusses the historical aspect of the study of microRNAs, their mechanism of formation, the features of circulating microRNAs and the possible therapeutic effect of exogenous microRNAs coming from food on the human body.