The nuclear tests of the 1950s have spoken: our liver is not as old as one might think.
In the mammals that we are, the liver very briefly fulfills the role of a purifying plant. It is he who has the difficult task of purging our fluids of compounds that may pose a threat to the delicate balance of the body. By definition, it is on the front line and particularly exposed to these elements.
However, if you can read these lines, it is because your liver continues to function despite these blows. To achieve this, evolution has endowed our liver with a remarkable and still relatively little-known feature: it is the only internal organ capable of spontaneously regenerating from existing tissue.
This mechanism is essential for our survival. However, it is now well established that the ability of cells to regenerate decreases with age. Therefore, researchers have tried to determine to what extent aging decreases the regenerative capacity of the liver. Unfortunately, the first studies of this type did not return frankly conclusive results when they were carried out on animals.
A team of researchers from the University of Dresden in Germany decided to skip this step and go directly to studying the human liver in vivo. This multidisciplinary group made up of biologists, physicists, mathematicians, and clinicians launched a study on different patients aged 20 to 84 years.
A study carried out thanks to old nuclear tests
The team of Dr. Bergmann, the lead author of the study, specializes in radiocarbon or carbon 14 datings. It is a slightly radioactive variant of carbon that is found almost everywhere in very small amounts, even in living things. And like all radioactive elements, this one gradually decays at a very precise rate. Based on this decay, the researchers can calculate the age of the substrate where this carbon molecule is found using a simple mathematical formula, even from a ridiculously small sample.
Is a technique that works wonders among geologists, paleontologists, and archaeologists; Carbon 14 dating is now an essential dating tool that allows you to determine the age of a fossil or other artifact with sometimes dizzying precision. The problem is that this disintegration is excessively slow; therefore, it is not supposed to be suitable for this type of study on living things. Well, almost, because the researchers were able to rely on an unexpected resource: open-air nuclear tests conducted in the 1950s.
These tests introduced a massive amount of carbon-14 into the Earth’s atmosphere. It works the same as standard carbon in biological terms. Naturally, it finished its course in the carbon cycle and by extension in living beings. Even if they were insignificant amounts that were not dangerous in themselves, all the cells formed at this time, therefore, present an abnormally high level of carbon-14.
Liver cells are only three years old on average
In 1963, these tests were officially prohibited by the decree of the United Nations. Since that date, the atmospheric level of carbon-14 has gradually fallen; a trend that has also been verified in living beings. is, therefore, a correlation that researchers can use to determine the age of cells based on their carbon-14 level. All that remained was to apply this technique to the liver cells of their patients.
Verdict: “It doesn’t matter if you’re 20 or 84, your liver stays in an average of three years”, explains Dr. Bergmann. This result demonstrates 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.
This three-year figure is just an average. Previous studies have already noted that some liver cells can live longer. These precise cells have the peculiarity of accumulating more and more DNA over time; unlike a standard cell, they “may carry four or eight sets of chromosomes, or even moreBermann explains.
And his team made an interesting discovery about these DNA-rich cells; it turns out that they can live up to ten times longer than others. “Typical cells turn over about once a year but can reside in the liver for up to ten years. Bergmann explains.
A path of research for the fight against cancer… and eternal life?
Another interesting point: the researchers also determined that these DNA-rich cells become more and more numerous with age. For researchers, this suggests the existence of a link with a protective mechanism which would prevent cells from accumulating too many harmful mutations.
And since every time such a mechanism comes up, it’s hard not to immediately think of the cancer, this serious disease caused directly by these mutations. “We need to determine if there are similar mechanisms in chronic liver diseases that can develop into cancersBermann explains.
This work is particularly promising because its scope extends far beyond liver cancer. As soon as we became interested in cell regeneration, we opened a pandora’s box containing a lot of ethical and scientific questions about the limits of human life. Such work will necessarily benefit many projects that will undoubtedly improve the lives of our elders… and, in the long term, will probably serve as the basis for projects such as Jeff Bezos’s, which has simply set itself a scientific task. force the elite to wage a ruthless war against aging (see our article).