A recent study published last week indicates that the human liver remains youthful even as we age. Using a technique to determine age through radiocarbon dating, researchers estimate that the average age of human liver cells is around 3 years old. However, some cells appear to live longer than others, and this discovery may help scientists better understand why, as well as the conditions that lead to many diseases such as liver cancer.
The aforementioned study was conducted by a team of scientists from the Dresden University of Technology in Germany. They sought to estimate the lifespan of liver cells collected from over 30 individuals who had passed away from various diseases, aged between 20 and 84. To do this, they relied on a technique known as “radiocarbon birth dating“, which was developed in the early 2000s.
The levels of radiocarbon in the environment have fluctuated over the past few decades due to the onset and cessation of atmospheric nuclear weapon testing. Because traces of radiocarbon can be found in the DNA of plants and animal cells, scientists can use radiocarbon as a “measure” to determine the age of a cell. The older the cell, the more radiocarbon is likely to be present in its DNA.
The average age of human liver cells is around 3 years old.
When the research team traced the birth dates of liver cells from their sample group, they discovered a common characteristic regardless of the age of the individuals from whom the livers were taken: most liver cells are young and nearly the same age. They then estimated that most liver cells replace themselves approximately once a year, and on average, our livers are less than 3 years old!
The liver is known for its resilience and rapid recovery rate—an essential trait for an organ that must continuously filter out toxins from our bodies. However, researchers state that they still do not know much about how the liver renews itself and whether this regenerative ability diminishes over time. The study suggests that the liver can remain youthful even while existing in an aging body.
On the other hand, as we age, it seems that the liver also undergoes corresponding changes. Some cells in the liver may carry more than two sets of chromosomes and still function normally, unlike most other cells in the body. The research team found that these DNA-containing cells can live much longer than other liver cells—up to a decade—and the human liver appears to accumulate more and more such cells. Therefore, researchers believe that this change is what helps our livers remain healthy for a long time. If this is accurate, then the risk of humans facing liver-related health issues may also increase when this process does not proceed as expected.
“As the number of such cells increases with age, it could be a protective mechanism against the accumulation of harmful mutations,” said study author Olaf Bergmann, a long-time researcher at the Dresden Center for Regenerative Therapy. “We need to investigate whether similar mechanisms exist in chronic liver disease, which in some cases can progress to cancer.“
The findings of the research team will be evaluated by other research groups before being published in academic medical literature. However, a similar study they conducted earlier this year provided evidence that certain brain cells can renew themselves even as we age—quite coincidentally aligning with this current research. The team’s next plan is to explore whether heart cells in individuals with chronic heart disease still retain their regenerative capabilities!
