A healthy human cell can divide itself to replace cells that have been destroyed or damaged by normal wear and tear. But nature has built-in a mechanism that prevents old or damaged cells from dividing infinitely. When that doesn’t work, the result is a cancer tumor, which just keeps growing without limit. The name of the safeguard against uncontrolled cell multiplication is cellular senescence, and as we age, old, senescent cells keep accumulating.
It’s been theorized that cells that have reached a biological dead-end are bad for us. When we're young and healthy, our immune systems clear them out, but as we age, this cellular "garbage disposal" process loses some of its effectiveness, and more senescent cells accumulate in various tissues and organs.
To see what would happen if we gave nature a hand taking out the trash, a group of researchers at the Mayo Clinic devised a way to remove senescent cells from mice. Treatment for the animals began when they reached middle age — which for a mouse is about 1 year old — and the results were impressive. The study was published in the journal Nature.
The test mice had a median lifespan that was longer by about 17 to 35 percent! Several organs were found to function better when the senescent cells were removed, and the mice not only lived longer, but they also had a healthier appearance, were more active in their cages, had better heart function, and less inflammation.
What’s great about this news isn't just a longer lifespan; it's the extension of the healthy years, not an extension of time spent battling an illness.
The study also provides some evidence that senescent cells promote the growth of tumors, since the mice treated had slower-growing tumors (they still had some, but they grew more slowly and were only fatal after a longer period of time).
This experiment seems to confirm that senescent cells — which are found all over the body and inside all organs, in increasing numbers as we age — have a negative net impact on health and longevity. And since removing these cells did not cause negative side effects (as far as we can tell), it raises new possibilities about developing drugs or therapies to extend the healthy years.
Here is doctor Jan van Deursen, the chair of biochemistry and molecular biology at Mayo Clinic, and the senior author of the paper, discussing his research: