Your Liver Is Only About Three Years Old, Scientists Say

According to recent study, the human liver remains youthful even as the rest of our bodies age, and the organ is on average less than three years old, regardless of the age of the person to whom it is linked.

Scientists discovered that liver rejuvenation is essentially unaffected as humans age, using mathematical modeling and a technique called retrospective radiocarbon birth dating, which ages human cells based on quantities of a carbon isotope that skyrocketed in the atmosphere during mid-20th century nuclear testing.

The liver's fundamental function, which is to remove poisonous compounds from the body, depends on this rejuvenation. The organ suffers as a result of this waste disposal, yet it has the unusual capacity to regenerate after being harmed.

"No matter if you are 20 or 84, your liver stays on average just under three years old," explains molecular scientist Olaf Bergmann of Dresden University of Technology in Germany.

The researchers looked at post-mortem and biopsy tissue samples from more than 50 people ranging in age from 20 to 84. They discovered that human biology maintains tight control over the bulk of the liver throughout our lifetimes by replacing liver cells on a regular basis.

Our bodies become less capable of renewing cells and carrying out repairs as we age. The latest study demonstrates that this does not apply to hepatocytes, or liver cells. Earlier animal experiments had shown mixed findings, but this time there is a lot more certainty.

However, when it comes to how rapidly liver cells regenerate, not all are created equal: The researchers discovered that a tiny percentage of people can live to reach ten years old. This appears to be connected to the number of chromosomal sets they have.

Aside from our sex cells, most cells in our body have two copies of our whole genome. Liver cells are an outlier, with a subset of cells producing even more copies of our whole DNA library on top of that.

"When we compared typical liver cells with the cells richer in DNA, we found fundamental differences in their renewal," Bergmann explains. "Typical cells renew approximately once a year, while the cells richer in DNA can reside in the liver for up to a decade." 

"As this fraction gradually increases with age, this could be a protective mechanism that safeguards us from accumulating harmful mutations. We need to find out if there are similar mechanisms in chronic liver disease, which in some cases can turn into cancer."

This is a significant new insight into the basic mechanics underlying how the liver functions – and, of course, the more we learn about the organs in the body, the better we can figure out how to keep them healthy and cure sickness.

Other organs, such as the heart, are also being studied to discover how quickly cells are replenished throughout the body. Cells may be correctly dated and renewal rates calculated using the same retrospective radiocarbon birth dating approach.

It's one of the most effective ways for determining the age of human tissue now available, as it uses the decay rates of radiocarbon in the atmosphere to match to traces in the body. It turns out that your organs aren't as ancient as you think.

"Our research shows that studying cell renewal directly in humans is technically very challenging but it can provide unparalleled insights into the underlying cellular and molecular mechanisms of human organ regeneration," Bergmann adds.