The article describes the main methods of assessment of physiological significance of coronary artery stenoses, their use in clinical practice and future perspectives. New diagnostic methods that are currently under research are discussed.

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.

Cardiovascular diseases are the main cause of death and disability in economically developed countries in the world. In response to the impact of various factors, the structure and function of several types of cells changes, contributing to the occurrence and progression of cardiovascular diseases. Search for sensitive and specific biomarkers is one of the most important problems in the field of diagnosis of cardiovascular diseases. In the last decade, microRNAs have more often been considered as potential biomarkers of a wide range of cardiovascular diseases, such as myocardial infarction, ischemic heart disease, heart failure, hypertension, diabetes mellitus and obstructive sleep apnoea. Early diagnosis of these diseases is essential to initiate immediate treatment, which can lead to improved outcomes. MicroRNAs are endogenous small (21-23 nucleotides) ribonucleotides involved in the regulation of protein synthesis from amino acids based on matrix RNA. MicroRNAs are involved in the regulation of expression of the majority (>60%) of genes encoding proteins, mainly due to its suppression, modulate numerous signaling pathways and cellular processes and participate in intercellular communication. There are different advantages of these biomarkers: low invasiveness during research, stability, resistance to destructive factors, for example, freeze-thaw cycles, enzymes in the blood. Some microRNAs are expressed everywhere, while others are specific to certain tissues and/or stages of development of the organism. At the same time, microRNAs were detected in various biological fluids: blood plasma, urine, seminal fluid, saliva, breast milk. Changes in both the amount and functional activity of microRNAs can lead to the development of various diseases. In the cardiovascular system, microRNAs control the functions of various cells, such as cardiomyocytes, endothelial cells, smooth muscle cells and fibroblasts. Thus, due to the stability of microRNAs, the tissue­specific nature of expression and secretion into specific fluids, it becomes possible to consider them as an attractive diagnostic. It is also particularly important that the expression levels of certain microRNAs reflect not only the presence of diseases in the early stages, but also the dynamic development of diseases in the later stages. This review presents the features of various microRNAs as biomarkers and their influence on some molecular pathways underlying cardiovascular diseases and describes the significant potential of supplementing traditionally used markers in clinical practice with microRNA biomarkers. Prospects for the development and limitations of the use of microRNAs as potential biomarkers are also described.

The article discusses the stages of formation and development of ultrasound diagnostics, including those with contrast enhancement. The main types of contrast agents and their mechanism of action are presented. Examples of the use of contrast-enhanced ultrasound in various fields of medicine are given. The prospects of the method and its place in clinical practice are discussed.