Scientists may one day slow down aging with a simple injection of youthful stem cells. They’ve just proven it can be done in mice.  The mice all had progeria, the Benjamin Button disease – the one that makes people age incredibly fast.

And the mice would normally have grown old when they were quite young. But that changed when researchers injected stem cells from healthy young mice into the quickly aging mice. Within days, the doddering and frail mice began to act like they were a youthful Brad Pitt in the movie - they started looking and acting younger.

Johnny Huard is a professor of orthopedic surgery at the University of Pittsburgh School of Medicine. He says when he saw the mice he thought he’d made a mistake, and put the normal mice in the wrong cage.

And the stem-cell injected mice survived about three times as long as would have without the treatment. And Huard thinks if he’d injected the mice again, they’d live even longer.

So why do the stem cells work? Scientists have discovered that we grow frail when our stem cells age and lose the ability to self-repair.

But with an injection of young stem cells, older ones are renewed.  So one day it might be standard for people to stash away their own stem cells when they’re young, so they can use them when they start aging.