Could getting rid of old cells turn back the clock on aging?

James began his career as a geriatrician. He wasn't happy with what he could give them.

"I got tired of writing prescriptions for wheelchairs, walkers and incontinence devices." He knew that aging was the biggest risk factor for chronic illness, but he wasn't able to do anything about it. To learn the skills he would need to tackle aging head-on, Kirkland went back to school and earned a PhD in biochemistry. He and Tchkonia are leaders in a movement to stop chronic disease by protecting brains and bodies from the effects of aging.

The number of Americans over the age of 65 is expected to double in the next 25 years. The time that a person lives free of disease is called the health span.

Aging cells are one of their targets. Damage, stress or just time can causeescent cells to stop dividing, but they don't die. One study found that senescent cells accounted for up to 36 percent of cells in some organs in old mice. They aren't just sitting there quietly. A toxic environment can be created whenescent cells release a bunch of compounds. Diabetes, stroke, osteoporosis, and several other conditions have been linked toescent cells.

The noxious cells and the idea that they could be mitigated by getting rid of them are getting a lot of attention. The National Institutes of Health is investing $125 million in a new research effort that aims to identify senescent cells in the human body as well as in mice over the natural lifespan. The National Institute on Aging has given more than $3 million to the Translational Geroscience Network multicenter team that is running preliminary clinical trials of potential antiaging treatments. There are drugs that kill senescent cells. There are small-scale trials of these in people with conditions like Alzheimer's.

John Varga is the chief of rheumatology at the University of Michigan Medical School and isn't a member of the TGN.

Some scientists think the field has been overblown because he and others sound a note of caution. Varga said there was a lot of hype. I think I have a very healthy skepticism. He warns his patients of the dangers of senolytic supplements alone.

Even in embryology, where the aging out of certain cells is crucial for proper development, researchers still don't know the biology of senescent cells. Laboratory mice show that destroying senescent cells improves health span. Only a few preliminary human trials have been completed with hints of promise.

Even so, Tchkonia and Kirkland think that senolytics could eventually help younger people with conditions such as cancer and injury, even if it is only for a short period of time. There could be applications all over the place.