Researchers discover a new blood component

We are very well aware that blood is made of components like red cells, plasma, platelets various factors with defined functions. Researchers seemed to have found out a new blood component in addition to the ones already known.

A team of researchers led by Inserm researcher Alain R. Thierry at the Montpellier Cancer Research Institute (Inserm/Université de Montpellier/Montpellier Cancer Institute has revealed the presence of whole functional mitochondria in the blood circulation. The research has revolutionized knowledge of this organelle by revealing that whole functioning extracellular mitochondria are in fact found in the bloodstream. This discovery may deepen knowledge of physiology and open up new avenues for treatment.

The researchers used previous findings which showed that the plasma of a healthy individual contains up to 50,000 times more mitochondrial DNA than nuclear DNA. They hypothesized that for it to be detectable and quantifiable in the blood in this manner, the mitochondrial DNA had to be protected by a structure of sufficient stability. In order to identify such a structure, plasma samples from around 100 individuals were analyzed. This analysis revealed the presence in the blood circulation of highly stable structures containing whole mitochondrial genomes. Following examination of their size and density, as well as the integrity of their mitochondrial DNA, these structures observed using electron microscopy (up to 3.7 million per ml of plasma) were revealed to be intact and functional mitochondria. Throughout the seven-year research period, the scientists used as many technical and methodological approaches as possible to validate this presence of circulating extracellular mitochondria in the blood."When we consider the sheer number of extracellular mitochondria found in the blood, we have to ask why such a discovery had not been made before, Thierry says. Our team has built up expertise in the specific and sensitive detection of DNA in the blood, by working on the fragmentation of extracellular DNA derived from the mitochondria in particular," he adds. But what is the role of these extracellular mitochondria? The answer to that could be linked to the structure of the mitochondrial DNA, similar to that of bacterial DNA, which gives it the ability to induce immune and inflammatory responses. Based on this observation, the researchers hypothesize that these circulating mitochondria could be implicated in many physiological and/or pathological processes requiring communication between the cells (such as the mechanisms of inflammation). Indeed, recent studies have demonstrated the ability of certain cells to transfer mitochondria between themselves, such as the stem cells with damaged cells. "The extracellular mitochondria could perform various tasks as a messenger for the entire body," Thierry explains.In addition to its importance to our knowledge of physiology, this discovery could lead to improvements in the diagnosis, monitoring and treatment of certain diseases. In fact, the research team is now devoting its attention to evaluating the extracellular mitochondria as biomarkers in non-invasive prenatal diagnosis and cancer

Journal Reference:Zahra Al Amir Dache, Amaëlle Otandault, Rita Tanos, Brice Pastor, Romain Meddeb, Cynthia Sanchez, Giuseppe Arena, Laurence Lasorsa, Andrew Bennett, Thierry Grange, Safia El Messaoudi, Thibault Mazard, Corinne Prevostel, Alain R. Thierry. Blood contains circulating cell‐free respiratory competent mitochondria. The FASEB Journal, 2020; DOI: 10.1096/fj.201901917RR