Researchers at the Mayo Clinic have just completed a fascinating study on what makes the human body age. They experimented on mice, and now the process must be adapted to humans, but it may be the Fountain of Youth we're all searching for.
A new, remarkable study of mice in the U.S. shows that cells that die as a person gets older, and they can be flushed out. New, younger, healthier living creatures are the result. Researchers at the Mayo Clinic say the onset of wrinkles, the wasting of the body's muscles or the development of cataracts can be delayed and even eliminated in the studies they did on mice. The BBC reports that these so-called "retired cells" accumulate naturally as the human body ages.
The researchers, who published their findings in the medical periodical Nature, refer to these retired cells as "senescent cells" and say they are the ones that stop dividing into new cells as we age. In young people, they are constantly dividing and then are cleared out of the body by the immune system, which is why the young stay young for a period of time. But as human age, the senescent cells stop dividing and therefore are unable to prevent tumors, for instance from progressing. The researchers believe that only around 10% of cells in very old people continue to be senescent.
In the work done by scientists at the Mayo Clinic, they came up with a way to kill all the senescent cells in genetically engineered mice. The animals were programmed to age far more quickly than normal, and when they were given a drug, the senescent cells would die.
USA Today reports that the researchers looked at three symptoms of old age: the formation of cataracts in the eye; the wasting away of muscle tissue; and the loss of fat deposits under the skin, which keep it smooth.
Researchers say the onset of these symptoms was "dramatically delayed" when the animals were treated with the drug. And when it was given after the mice had aged substantially, there was an improvement in muscle function.
Researcher Dr James Kirkland, said:
"I've never seen anything quite like it."
A colleague Dr Jan van Deursen told the BBC:
"We were very surprised by the very profound effect. I really think this is very significant."
To eliminate the senescent cells in the in the mice, the researchers focused a tracer on a protein called p16, which the stops cells from dividing. The scientists used the p16 to activate a type of "suicide gene" within the senescent cells of the mice. The protein made by this gene kills the senescent cells (without damaging other normal cells) after a drug specifically designed to activate it is administered.
The doctors say they used two sets of prematurely aged mice in the study. In one set, the researchers cleared senescent cells for the entire 15 months of the mice's typical lifespan. In another set of mice, they waited until age-related problems had begun and then cleared the senescent cells away for a few months.
The results were that in the first set of mice, lifelong destruction of the senescent cells prevented all age-related problems. In the second set, removing senescent cells later in life slowed down any age-related health problems.
Dr. Kirkland, the study leader, says what they noticed in both groups of mice was that their activity level was higher in both instances.
The study raises the tantalizing prospect of slowing the process of aging in humans. But a thorny problem will be just how to flush the senescent cells out of human beings.