Cell secretions spread throughout the body, accelerating aging after two weeks of experiments on young mice.
The starting point of this study is whether the known "rejuvenation effect of young blood" is not actually due to young blood, but to the fact that extra young blood dilutes the aging function of old blood.
Since the 2010s, one of the main focuses of scientists studying aging has been the regenerative effects of young blood. At the time, a number of studies were published, confirming this through animal experiments.
For example, researchers at the University of Pittsburgh in the United States and the University of Valencia in Spain published experimental results last year and this year, respectively, confirming the rejuvenating effects of extracellular vesicles (EVs) in the blood of young mice. Some studies look for causes in plasma and stem cells in young blood; One study found that a Dutch woman who died in 2005 at the age of 115 had only two stem cells left in her blood. This has led to a series of follow-up studies to determine which components in young blood produce this effect. However, young blood therapy is also the subject of debate about whether blood transfusion rejuvenation is morally correct, along with side effects such as immune responses.
So, conversely, what happens if aging blood is injected?
On July 29, a joint research team from korea University School of Medicine and the University of California, UC Berkeley conducted an experiment to transfuse young mice with blood from older mice, and found that young mice aged faster, and the study was published online in the international journal Natural Metabolism. This effect is the opposite of when young blood is injected. This suggests that cellular aging is not just a wear and tear phenomenon caused by long-term use.
In previous transfusion experiments between young mice and old mice, it has been confirmed that the health of young mice with aged blood transfusions deteriorates. However, the study focused primarily on rejuvenation in older mice, while no detailed analysis of the effects that occurred in younger mice was conducted.
The researchers focused on this part of the experiment. According to the paper's lead author, Professor Chung Ok-hee (Medical and Life Sciences) of Korea University School of Medicine, the starting point of the study is that "the problem that has long been called the rejuvenation effect of young blood is actually not due to young blood, but to the addition of young blood, diluting the aging function of old blood." That's the problem.
Just as cancer metastasizes in the blood, aging also metastasizes
The researchers transfused blood from three-month-old mice with older mice about two years old.
After two weeks, the number of aging cells in young mice increased significantly. Cells of various organs, including the liver and kidneys, are damaged and stop dividing. That doesn't mean they die, but they become a kind of zombie cell. This is a phenomenon that occurs at the beginning of aging. This phenomenon is particularly pronounced in the liver and brain.
After the blood of the aging mice was transfused, the muscle strength of the young mice also weakened. Even if they don't age, cell aging is progressing. The researchers found that "overall, the degree of negative effect of transfusion of old blood is equal to or greater than the positive effect of transfusion of young blood."
Why? The researchers analyzed that factors secreted by aging cells in the blood may lead to "aging transitions", that is, factors circulating in the blood that cause cells and tissues in young mice to age. This is the same principle as carcinogens that spread throughout the body in the bloodstream, causing cancer to metastasize.
Aging cells secrete inflammatory substances, proteolytic enzymes, and other substances instead of stopping their proliferation. This is known as a secretory trait associated with cellular senescence (SASP). However, in this study, it was not possible to determine which substances secreted by senescent cells specifically caused the metastasis of aging.
A new paradigm in aging treatment research
Professor Zheng said: "This study is not only the passage of time in biology, but also significantly proposes a new paradigm accelerated by the transfer of aging." So far, aging treatment research has focused on dealing with the aging "cell" itself, but this study is a new concept study on the use of the "transfer" mechanism of aging.
Co-researcher Professor Kang Boi told the scientific journal New Scientist that "cell aging is only part of the aging process" and that "this study opens up new horizons for research by explaining why drugs (senescent agents) that eliminated aging cells in previous clinical trials were not as successful as expected." He commented.
Professor Chung said that "anti-aging drugs that have been developed to target aging cells have failed in many clinical trials" and that "the focus of anti-aging drug development needs to change, as this study reveals that the process of aging transition is mediated by cell-derived substances rather than cells in various tissues".
This raises a new goal of developing drugs that can remove the factors that induce aging from the bloodstream in the treatment of aging diseases. Professor Chung Ok-hee added: "The next research task is to determine exactly what substance is causing the shift in ageing.
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