After damage, the liver can regenerate. It was not known if this ability decreases as we age. The age of the human liver was determined using a technique known as retrospective radiocarbon birth dating. The average age of the liver is less than three years. The results show that aging doesn't have an effect on the renewal of the liver.
Our bodies need the help of the liver to clear toxins. It is likely to be injured frequently because it deals with toxic substances. The liver has a unique ability to repair itself after being damaged. The ability of the body to heal itself and regenerate decreases as we age, and scientists wondered if the capacity to renew also decreases with age.
The nature of regeneration in humans remained a mystery. Some studies pointed to the possibility of long-lived cells while others showed a constant turnover. It was clear to us that if we want to know what happens in humans, we need to find a way to assess the age of human cells.
The human is a young organ.
The team of biologists, physicists, mathematicians, and clinicians were led by Dr. Bergmann. The team found that the cells of all subjects were the same age.
Even if you are 20 or 84, your liver stays on average just under three years old. The results show that the process of adjusting the mass of the body is maintained even in older people. This ongoing cell replacement is important for the regeneration and formation of cancer.
The cells with more DNA Renew Less.
Not all of the cells in our body are young. Some cells can live up to 10 years. Most of our cells have two sets of chromosomes, but some cells accumulate more DNA as they age. In the end, such cells can carry four, eight, or even more sets of chromosomes.
When we looked at the cells with the richer DNA, we found differences in their renewal. The cells richer in DNA can reside in the liver for up to a decade, and this could be a protective mechanism. We need to find out if there are similar mechanisms in chronic liver disease, which can lead to cancer.
Lessons from the nuclear disaster.
Determining the biological age of human cells is a huge technical challenge as methods used in animal models cannot be applied to humans.
Dr. Bergmann's group specializes in retrospective birth dating and uses the technique to assess the biological age of human tissues. Life on Earth is dependent on carbon, a chemical element that is ubiquitous. Radiocarbon is a type of carbon. It can be seen in the atmosphere. Plants pass it on to animals and humans in the same way carbon is. Radiocarbon is unstable and weakly radioactive. Archeology uses these characteristics to determine the age of ancient samples.
Archeologists have used the decay of radiocarbon successfully for many years to assess the age of specimen, one example being dating of the shroud of Turin, says Dr. Bergmann. It is not useful for determining the age of human cells. We can still use the radiocarbon in our research.
Massive amounts of radiocarbon were introduced into the atmosphere, plants, and animals by the aboveground nuclear tests carried out in the 1950s. Cells formed in this period have higher amounts of radiocarbon in their genes.
The amount of atmospheric radiocarbon dropped after the official ban of aboveground nuclear testing in 1963. The values of atmospheric and cellular radiocarbon are 888-609- 888-609- 888-609- 888-609-
Even though they are not harmful, we can detect and measure them in tissue samples. By comparing the values to the levels of atmospheric radiocarbon, we can retroactively establish the age of the cells.
Insights directly from the source.
The mechanisms that drive the regeneration of other tissues are explored by the Bergmann group. The team used their expertise in retrospective birth dating to show that the formation of new brain and heart cells is not limited to the beginning of a child's life. New human heart muscle cells can still be created in people with chronic heart disease.
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.
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