Peripheral artery disease is one of a number of conditions shown to benefit from even early, crude efforts at stem cell transplantation: "Peripheral artery disease (PAD) affects 8 million Americans. It's when arteries in the legs narrow. The most common symptoms of PAD are cramping, pain or tiredness when walking. It can so bad that some can't walk at all. Now an experimental stem-cell therapy may offer hope to people with severe pad. Ronald Davis can move again after seven long years. 'Pain 24 hours a day, seven days a week,' said Davis. Plaque clogged the artery carrying blood to his leg, which cut off oxygen flow. ... Left alone, it can cause ulcers, gangrene and even lead to amputation. ... Davis began a last-ditch stem-cell therapy at Duke University. His leg was marked for 30 injections, totaling millions of stem cells. For him, there was no other choice. ... Cells are taken from the placentas of Israeli women who've given birth. Once injected, they secrete proteins, which boost additional cell growth. Then, it's believed those cells may contribute to the growth of additional vessels around the plaque, circumventing the blockage. ... Three days after injections, Davis was walking, and doctors say the oxygen level in his leg tissue jumped from 43 percent to 67 percent. ... This specific type of stem-cell therapy is currently involved in a Phase 1 clinical trial."