Extracellular mitochondria as promising diagnostic agents

Abstract

Nowadays, there is a new concept that says that mitochondria naturally circulate in the blood and this is characteristic of both human and animal bodies. It is believed that circulating mitochondria can easily pass through tissue barriers due to their small size (50–400 nm). The phenomenon of mitochondrial intercellular transfer, which is bidirectional, has been observed in vitro and in vivo, under both physiological and pathophysiological conditions, and among a variety of cells, including malignant tumor cells. Circulating cell-free intact mitochondria are thought to play an active biological and physiological role, as mitochondria are already known to be systemic mediators of intercellular communication, transmitting hereditary and non-hereditary biological components, including MtDN A. Mitochondrial components of cellular origin, including mitochondrial DNA, were detected in the extracellular space. There are about 50,000 times more copies of the mitochondrial genome than the nuclear genome in the blood plasma of healthy people. The researchers confirmed that mitochondrial cell-free DNA (McfDNA) is stable enough for detection and quantification, implying that there are stable structures protecting these DNA molecules. The circulating mitochondrial genome, which is released as a cell-free mitochondrial DNA, is recognized as a new biomarker of mitochondrial stress and signal transduction. McfDNA has become an attractive circulating biomarker because of its potential use in diagnostic programs for various diseases, e. g., diabetes, acute myocardial infarction, and cancer. There is no doubt that detection of circulating mitochondria and their DNA in body fluids opens up a new promising scientific direction in biology and medicine. The article analyzes modern scientific data devoted to proving the existence of extracellular mitochondria, their functions outside the cell and diagnostic value.