The nuclear tests of the 1950s spoke: Our liver is not as old as one might think.
In the mammals that we are, the liver very briefly plays the role of a sewage treatment plant. It has the difficult task of ridding our fluids of compounds that could pose a threat to the body’s delicate balance. By definition, therefore, it is on the front line and particularly exposed to these elements.
However, if you are able to read these lines, it is because your liver continues to function despite these beatings. To achieve this, evolution has endowed our liver with a remarkable and still relatively poorly understood property: it is the only internal organ capable of spontaneous regeneration from existing tissue.
This mechanism is essential for our survival. However, it is already well known that the ability of cells to regenerate decreases with age. Researchers have therefore tried to find out to what extent aging reduces the liver’s ability to regenerate. Unfortunately, the first studies of this type, when conducted on animals, did not produce conclusive results.
A team of researchers from the University of Dresden in Germany therefore decided to skip this step and proceed directly to studying the human liver in vivo. This multidisciplinary group of biologists, physicists, mathematicians and clinicians started a study on different patients aged 20 to 84 years.
A study carried out thanks to old nuclear tests
The team of dr. Bergmann, first author of the study, specializes in Radiocarbon dating or carbon 14. It is a slightly radioactive variant of carbon that is found in very small amounts almost everywhere, including in living things. And like all radioactive elements, this one gradually decays at a very precise rate. From this decay, even from a ridiculously small sample, researchers can use a simple mathematical formula to calculate the age of the substrate on which that carbon molecule resides.
It is a Technology that works wonders for geologists, paleontologists and archaeologists; Carbon 14 Dating is now an absolutely essential dating tool that allows you to do this determine the age of a fossil or other artifact with sometimes dizzying accuracy. The problem is that this decay is overly slow; it should therefore not be suitable for this type of study of living beings. Almost, because the researchers were able to fall back on an unexpected resource: the open-air nuclear tests conducted in the 1950s.
These tests introduced a huge amount of carbon-14 into the earth’s atmosphere. It works biologically like standard charcoal. It ended up naturally in the carbon cycle and thus in living things. Even if the amounts involved were negligible and were not in themselves dangerous, all cells formed at this point show a unusually high carbon-14 content.
On average, liver cells are only three years old
In 1963, these tests were officially banned by United Nations decree. Since that date, atmospheric carbon-14 levels have increased gradually fallen off; a tendency that has also been demonstrated in living beings. So it is one Correlation that researchers can use to determine the age of cells based on their carbon 14 content. All that remained was to apply this technique to their patients’ liver cells.
Verdict: “whether you are 20 or 84, Your liver will live an average of three years“, explains Dr. miner. This result shows how precisely the cells of this vital organ are regulated by the body and that this mechanism is maintained as the patient ages. And to understand this mechanism, we need to take a closer look at the age differences between these cells.
In fact, this three-year figure is just an average. Previous studies have already found that some liver cells can live longer. These precise cells have the particularity of accumulating more and more DNA over time; as opposed to a standard cell,”they can carry four or eight sets of chromosomes or even more‘ explains Berman.
And his team made an interesting discovery about these DNA-rich cells; They can live up to ten times longer than the others. “Typical cells are renewed about once a year, but these can remain in the liver for ten years‘ explains Bergman.
A path of research for the fight against cancer … and eternal life?
Another interesting point: the researchers also found that these DNA-rich cells become more numerous with age. For researchers, this indicates a connection with a protective mechanism which would prevent cells from accumulating too many harmful mutations.
And since every time such a mechanism appears, it is difficult not to immediately think of it Cancer, this serious disease directly caused by these mutations. “We need to determine if there are similar mechanisms in chronic liver disease that can lead to cancer‘ explains Berman.
This work is particularly promising as its scope extends well beyond liver cancer. As soon as we are interested in cell regeneration, we open a Pandora’s box containing a whole heap of ethical and scientific questions about the limits of human life. Works of this nature are bound to benefit many projects that will surely improve the lives of our elders… and, in the long term, will likely serve as the basis for projects like that of Jeff Bezos, who simply set a scientific task to force the elite to wage a merciless war against the aging (see our article).
The text of the study can be found here.