The liver can regenerate itself after being damaged, but whether this ability will weaken with our age has been unknown for a long time A new study has found that age does not slow the ability of the liver to regenerate - whether it is 20 or 80, the average life span of liver cells is only three years
The liver undertakes the dangerous work of detoxifying the body. Due to frequent exposure to toxins, it faces more damage than most organs. In order to keep us healthy throughout our lives, the liver has developed an extraordinary ability to regenerate, which is unique among organs. But exactly how it accomplished this feat -- and whether it slowed down with age -- has been a mystery, and animal models have not been able to clarify it. So in this new study, researchers at the University of Dresden want to find out.
"Some studies have pointed out the possibility of long-lived hepatocytes, while others have shown the continuous replacement of hepatocytes," said Dr. Olaf Bergmann, the corresponding author of the study. "We know very well that if we want to know what happens in humans, we need to find a way to directly assess the age of human hepatocytes."
To find a solution, the research team turned to an unlikely source - the nuclear tests of the 1950s. When a nuclear bomb is detonated on the ground, a large amount of radioactive carbon is blasted into the atmosphere and then absorbed into their DNA by plants and animals. After the ground nuclear test was banned in 1963, the content of radioactive carbon in the atmosphere decreased year by year -- so did the content in biological cells.
Bergmann said: "although these are negligible and harmless quantities, we can detect and measure them in tissue samples. By comparing these values with the level of radioactive carbon in the atmosphere, we can trace the age of cells.".
To put this idea into practice, the team analyzed the radiocarbon levels in the livers of 33 dead people between the ages of 20 and 84. Sure enough, they found that no matter how old a person is, the age of the organ is roughly the same - on average, less than three years old. But not all liver cells are of the same age -- some have been found to regenerate every year or so, while others may persist for as long as a decade. Interestingly, cells that live longer are those that accumulate more sets of chromosomes.
Bergmann said, "most of our cells have two sets of chromosomes, but some cells accumulate more DNA with age. Finally, these cells can carry four, eight or more sets of chromosomes. Because It may be a protective mechanism to ensure that we do not accumulate harmful mutations. We need to find out whether there is a similar mechanism in chronic liver disease. In some cases, chronic liver disease may become cancer. "