The liver is responsible for clearing the toxins in the body and because of that, it is constantly bombarded by toxic substances that could injure it. To overcome this, the liver has a unique capability of regenerating itself after damage. But like many organs in the body, scientists expect its ability to regenerate to decline as the person grows old.
Previous research shows contradictory answers, with some claiming liver cells are long-lived while others showed it is constantly regenerating.
According to Medical Xpress, scientists from Technische Universität Dresden decided to find a way to directly assess the age of human liver cells to know how it regenerates.
Human Liver Remains Under Three Years Old Regardless of A Person's Age, Study Reveals
The Young Human Liver
Dr. Olaf Bergmann, the lead author of the research, led a team of scientists composed of biologists, physicists, and mathematicians to analyze the livers of individuals who died between the age of 20 and 84. They found that regardless of the person's age, the liver remains more or less the same age.
He explains that, on average, liver cells remain under 3 years old. The result shows that the adjustment of liver mass to the needs of the body is regulated through the constant replacement of liver cells that is still present even in old age. The ongoing liver cell replacement plays a key role in liver regeneration and cancer formation.
However, not all liver cells are that young since a small fraction of cells regenerate themselves after 10 years. A similar report from Science Daily said that analysis showed that these cells carry more DNA than the typical liver cell.
According to Dr. Bergmann, unlike typical cells with two sets of chromosomes, these special cells accumulate more DNA as they age and carry four, eight, or even more sets of chromosomes.
In comparison, typical cells tend to renew once a year, while the cells with more DNA can reside for up to a decade. Dr. Bergmann pointed out that the process could be a protective mechanism that safeguards the liver from harmful mutations. The team also wants to know if there are similar mechanisms involved in chronic liver disease that can turn into cancer.
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Determining the Age of Liver Cells
Since methods in determining the biological age used in animal models cannot be used in human cells, Dr. Bergmann's group used retrospective radiocarbon birth dating, which assesses the biological age of human tissues.
Archaeologists have been using the said method for many years to analyze the age of ancient specimens. Dr. Bergmann added that the radioactive decay of radiocarbon is so slow and provides enough resolution for them.
In the study titled "Diploid Hepatocytes Drive Physiological Liver Renewal in Adult Humans," published in Cell Systems, researchers analyzed the radioactive decay of radiocarbon. They noted that they were able to establish the age of cells by comparing the values of cellular radiocarbon to the levels of atmospheric radiocarbon.
They also explored the mechanism behind the static regeneration of the brain and heart. The researchers found that the formation of new brain and heart cells is not limited to prenatal time and continues until old age.
The research shows that studying cell renewal directly in humans can be challenging but can provide unparalleled insights into the underlying cellular and molecular regeneration mechanisms in human organs.
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