A team of researchers has highlighted the presence in the bloodstream of organelles responsible for the respiration of cells, which until now have been found outside of these cells only in very specific cases. These results provide unprecedented knowledge in physiology and open the way to new therapeutic avenues, according to an article from Wrapva.
What is our blood made of, which oxygenates, nourishes, cleanses and defends all the tissues and organs of the body? It is a living tissue made up of red blood cells, white blood cells and platelets, bathed in a liquid called plasma. However, the blood, which the researchers thought they knew so well, would in fact contain elements hitherto undetectable. This is shown by the work of researchers from Inserm, the University of Montpellier and the Montpellier Cancer Institute at the Montpellier Cancer Research Institute. Their study has for the first time highlighted the presence in the bloodstream of complete and functional mitochondria.
Places of cellular respiration, the mitochondria are the “batteries” of cells and play a major role in energy metabolism and intercellular communication. They have the distinction of having their own genome, transmitted only by the mother, and distinct from the DNA contained in the nucleus. Mitochondria can sometimes be seen outside of cells as “encapsulated” fragments in microvesicles. Under certain very specific conditions , platelets, these tiny cells that stop bleeding , prevent or stop bleeding, are also able to release mitochondria in the extracellular space.
“One may wonder why this has not been discovered before”
The work of this research team, published in The FASEB Journal , disrupts knowledge of this organelle, revealing that extracellular mitochondria, complete and functional, are circulating in the blood . The researchers built on previous results showing that the blood plasma of a healthy individual contains up to 50,000 times more mitochondrial DNA than nuclear DNA (DNA located in the nucleus of cells in the form of chromosomes). They hypothesized that, for it to be so detectable and quantifiable in the blood, mitochondrial DNA had to be protected by a sufficiently stable structure.
In order to identify the latter, a hundred samples of blood plasma (the liquid part of the blood which allows red blood cells and platelets to circulate) were analyzed. These analyzes revealed the presence in the bloodstream of structures containing whole mitochondrial genomes. After examining their size and density, these structures observed by electron microscopy have been shown to be intact and functional mitochondria . “When we consider the high number of extracellular mitochondria that we have found in the blood, we may wonder why this has not been discovered before”, explains Professor Alain R. Thierry.
A role linked to the body’s inflammation and immunity
But what role do these extracellular mitochondria play? Researchers hypothesize an ability to induce immune and inflammatory responses. These could be involved in many physiological and / or pathological processes requiring communication between cells, such as the mechanisms of inflammation. Indeed, recent studies have demonstrated the ability of certain cells to exchange mitochondria with one another, such as stem cells with damaged cells. “The extracellular mitochondria could perform several tasks as a messenger for the whole organism”, specifies Alain R. Thierry.
This discovery is important because in addition to its interest in knowledge of the physiology of the human body , it could lead to an improvement in the diagnosis, monitoring or treatment of certain diseases. The research team is now focusing on the evaluation of extracellular mitochondria as biomarkers in non-invasive prenatal diagnosis and cancer. Note that blood plays a central role in the defense of the body against pathogens (bacteria, viruses, etc.). And in case of injury, he ensures the repair of his vessels himself. It carries the hormones essential for the regulation and proper functioning of the body.
News source Wrapva