(ORDO NEWS) — The study confirmed that aging does not affect liver regeneration: this organ is an excellent replacement for its cells in both young and old people.
A team of biologists, physicists, mathematicians and clinicians, led by the Center for Regenerative Therapy at Dresden University of Technology (Germany), used retrospective radiocarbon dating to determine the age of the human liver, because this organ has the ability to regenerate due to renewed hepatocytes – parenchyma cells.
As shown by a study, the results of which are presented in the journal Cell Systems , age does not affect the process of liver renewal: cells are equally well replaced in both young and old.
Although it is known that hepatocytes can be renewed in adulthood, until now there was no clear picture of their behavior: scientists did not know whether hepatocytes are exchanged throughout life or are physiologically long-lived cells, like cardiomyocytes and neurons.
The authors of the new work examined the liver of 33 people who died between the ages of 20 and 84: genomic DNA was extracted from the cell nuclei to obtain a comprehensive model for the renewal of hepatocytes and their age distribution.
As a result, using retrospective radiocarbon dating and computer modeling, it was possible to find out that liver cells in all people are almost the same age – a little younger than three years. According to the researchers, their discovery indicates for the first time that this organ remains young to the end.
“Because the liver is composed of different types of cells, we further separated nuclei from hepatocytes and non-hepatocytes.
Genomic concentrations of carbon-14 (14C) suggest that hepatocytes are renewed throughout life at the level of 19% per year and have an age of 2.7 years for young people. In mature and older age, they are updated by 17% per year, the average age of hepatocytes is 2.9 years.
Non-hepatocytes make up only a small fraction of liver cells, but they are a very diverse group with different functions.
There is no real characterization of their unique renewal dynamics. We got only a general idea: they are updated at the level of 16% per year for a 25-year-old person and 13% per year for a 75-year-old, ”says the work.
However, it turned out that not all liver cells are so young: the researchers found a lower renewal rate in polyploid cells, whose average age was estimated at ten years, and their number increased in the process of human aging.
Unlike diploid cells, which have two sets of chromosomes, these cells accumulate more DNA, can carry four, eight or more sets of chromosomes, are gigantic in size, and are often found in tumor tissues or exposed to penetrating radiation.
“Whether long-lived polyploid liver cells make the liver more susceptible to age-related diseases, or whether they act as a resistance factor to cope with cellular stress, thereby preventing loss of organ function and the development of cancer, remains an important issue that needs to be addressed,” the scientists concluded.
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