About 22 years ago scientists conducting research on the aging of mice noticed that some of the animals unexpectedly experienced what looked like rapid aging. Their fur began disappearing; they could no longer move as easily as before; and their eyes filled with cataracts, among other aging-related maladies. The peculiar thing was these mice were only 3 months old – just 2 months past puberty and about 2 years before these changes would normally occur. These mice should have been in the prime of their life – getting ready for reproduction. Instead, they declined rapidly. Why?
It was discovered that these rapidly aged young mice accumulated what are known as “senescent cells” in their bodies – cells that were supposed to die, but didn’t. Think of senescent cells as the gunk that accumulates in the oil in the internal combustion engine in your car. Swap out the old oil for new and suddenly a car that is sluggish, now operates more efficiently. In humans and other living things, the body normally removes this gunk continuously through a process known as “apoptosis” – also called programmed cell death. Convincing cancer cells to experience apoptosis is a promising area of research.
The scientists that made this discovery wondered if removing these zombie cells could do more than just help living machines operate more efficiently – they thought it might be possible to actually reverse the signs and symptoms of aging. If possible, science might have discovered a way to help us become younger versions of ourselves. That is, to become “undead” in a way – see image below.
Is it really possible that aging is caused, in part, by the accumulation of zombie cells, and variation in the rate of aging and how long we live could be influenced by how efficient apoptosis operates in our bodies? Could risk factors such as smoking and obesity interfere with or hinder our body’s natural apoptotic mechanism for removing gunk? Maybe!
The term “reverse” is not a normal part of our vocabulary in aging science because it sounds dangerously close to claims often made by those advocating for the second oldest profession – an anti-aging industry selling every conceivable snake oil for the last three thousand years with promises of everlasting youth. I discussed this history in a book I published more than 20 years ago.
But guess what?
In the years since this discovery was made, dozens of experiments have now confirmed that these accumulating zombie cells are a major cause of aging, and eliminating them can prevent certain illnesses, restore physical fitness, improve the functioning of internal organs such as kidneys and the liver and external organs (e.g., the skin), improve lung disease, and even restore damaged cartilage – among other benefits. The holy grail of life extension was observed in normally aging mice that had their senescent cells removed.
A number of biotechnology companies have since been created based on this concept of removing zombie cells as a way to extend healthspan; reverse some of the signs of aging; and possibly even extend life. The compounds discovered that remove these senescent cells are known as “senolytics”.
There is no question that senolytics reverse aging in mice. The question now is whether they’ll work the same way in humans.
The important news for readers of this article is that the first clinical trials testing senolytic compounds in humans are now underway at the Mayo Clinic in Minnesota. The best non-technical articles published on this topic are located here and here.
While it’s premature for anyone to be using senolytic compounds already being sold on the Internet through the anti-aging industry, I’m optimistic enough to suggest that most of us alive today will eventually be using them to forestall the ravages of aging. We’ll be told by our physician that our prescription for a senolytic compound will treat a disease we already have or prevent one from emerging, but the reality is that aging itself will be modified and possibly reversed. I don’t expect a radical increase in lifespan as a result, but I do expect notable improvements in healthspan to occur (“more brain power; yes please”).