(ORDO NEWS) — The human liver stays young even as the rest of our body ages, according to new research, and is less than three years old on average, regardless of a person’s age.
Using mathematical modeling and retrospective radiocarbon dating of birth, which dates human cells based on the level of carbon isotope that grew in the atmosphere after nuclear tests in the mid-20th century, the scientists found that little to no liver renewal occurs as we age.
This renewal is the key to the main function of the liver – cleansing the body of toxic substances. Removal of toxic substances from the body requires considerable effort from the body, but it has a unique ability to self-repair after damage.
“Whether you’re 20 or 84 years old, your liver lives on average just under three years,” says molecular biologist Olaf Bergmann of the Dresden University of Technology in Germany.
The team of researchers analyzed post-mortem and biopsy tissue samples from more than 50 people aged 20 to 84. They found that our biology maintains tight control over liver mass throughout life through constant replacement of liver cells.
As we age, our body becomes less capable of cell renewal and repair. A new study shows that this is not the case for hepatocytes – liver cells. Whereas earlier animal studies have yielded conflicting results, there is much more clarity here.
However, not all liver cells are the same in terms of how quickly they renew themselves: a small proportion can live up to 10 years, the researchers found. This appears to be related to how many sets of chromosomes they carry.
Most cells in our body, with the exception of germ cells, carry two copies of the entire genome. Liver cells are a strange exception: some cells generate even more copies of our entire DNA library.
“When we compared typical liver cells with cells richer in DNA, we found fundamental differences in their renewal,” says Bergmann. “Typical cells are renewed about once a year, while cells richer in DNA can stay in the liver for up to ten years.”
“Because this proportion gradually increases with age, this may be a protective mechanism that prevents us from accumulating deleterious mutations. We need to find out if there are similar mechanisms in chronic liver disease, which in some cases can develop into cancer.”
This is an important new insight into the biological mechanisms that underlie the functioning of the liver – and of course, the more we know about the organs of the body, the better we can understand how to keep them healthy and how to treat them from disease.
Researchers are also looking at other organs, including the heart, to understand how quickly cells are renewing throughout the body. The same method of retrospective radiocarbon dating of birth can be used to accurately date cells and determine the rate of renewal.
It is one of the best methods to date for determining the age of human tissue, using the decay rate of radiocarbon in the atmosphere according to traces in the body. As it turns out, your organs may not be as old as you think.
“Our study shows that studying cellular renewal directly in humans is technically very difficult, but it can provide unprecedented insight into the underlying cellular and molecular mechanisms of human organ regeneration,” says Bergmann.
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