Our blood consists of red and white blood cells and platelets bathed in a liquid known as plasma. But the blood is also composed of complete and functional mitochondria researchers at the Inserm of the University of Montpellier and the Montpellier Cancer Institute revealed in a study published on January 19 in The Faseb Journal. These organelles play a key role in maintaining the lipid content and good ion concentrations necessary for physiological communication, in supplying the energy needed for blood circulation, in supporting the transport of glucose and insulin and in eliminating potential health risks.
They also have the peculiarity of having their own genome. The genome is transmitted exclusively by the mother and differs from the DNA in the nucleus. Until now, mitochondria have only been found outside cells in special cases, released by platelets into the extracellular space. In the long term, these results, unprecedented in physiology, pave the way for new therapeutic paths.
In the past, research has shown that a healthy person’s blood plasma contains up to 50,000 times more mitochondrial DNA than nuclear DNA. To try to detect and quantify it in the blood, the researchers here had the idea of protecting it in a stable structure. Then they analyzed about 100 blood plasma samples.
A messenger for the entire organism
Using a highly sensitive detection method called genetic amplification, which allows for direct measurement of minimal amounts of DNA, they discovered the presence of structures in the bloodstream that contain the intact, functional mitochondrial genomes. “If you look at the high number of extracellular mitochondria we find in the blood, we wonder why this was not discovered earlier,” says Professor Alain R. Thierry, who led the research.
In the blood, these mitochondria could be involved in physiological and/or pathological processes that require communication between cells, such as inflammatory mechanisms, the researchers argue. In particular, recent studies have shown that certain cells can exchange mitochondria, such as stem cells with damaged cells. “The extracellular mitochondria could perform various tasks as messengers for the whole body,” explains Alain R. Thierry.
Ultimately, this discovery could lead to better diagnosis, monitoring or treatment of certain diseases.
Changing the mitochondrial DNA increases the risk of cancer.
The research team is now investigating the extracellular mitochondria as biomarkers in non-invasive prenatal diagnosis and cancer. “Further research is needed to assess the impact and potential implications of this discovery in terms of cellular communication, inflammation and clinical applications”, the researchers conclude.
Since mitochondria play a key role in regulating the body’s major metabolic pathways, their destruction or weakening can lead to serious complications such as multiple sclerosis, autism, bipolar disorder, chronic fatigue syndrome, type 2 diabetes, heart disease, and cancer.
When the mitochondrial DNA is altered, the risk of cancer increases. When too many free radicals are produced, mitochondria create oxidative stress that prevents antioxidants from defending the body against cancer. In the past, researchers have found that it is mainly lung, breast and kidney cell carcinomas that have increased as a result of these mutations.