DURHAM, N.C. -- Cells taken from a woman's placenta are helping people walk without pain. It sounds strange, but the experimental therapy may be a solution for the eight million Americans suffering from peripheral artery disease.

Ronald Davis can move again after seven long years.

"Pain 24 hours a day, seven days a week," Davis said.

Plaque clogged the artery carrying blood to his leg, which cut off oxygen flow. It's called peripheral artery disease. Left alone, it can cause ulcers, gangrene and even lead to amputation.

"There, at some point, it felt like the muscles were ripping out. It's just so painful," Davis said.

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.

"There really isn't an adequate therapy," Christopher Kontos, M.D., cardiologist at Duke University explained.

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.

"We are looking for something else to do to prevent an amputation or help healing," Manesh Patel, M.D., cardiologist at Duke University added.

Three days after injections, Davis was walking, and doctors say the oxygen level in his leg tissue jumped from 43 percent to 67 percent.

"I have these feelings in it now, feels like it's healing," Davis said.

For Davis and his wife, feeling is believing.

"This has given me more light at the end of the tunnel, like I'm through the tunnel now," Davis concluded.

This specific type of stem-cell therapy is currently involved in a phase-one clinical trial. PAD affects up to 20 percent of people over the age of 65.

Placentas Help People Walk? -- Research Summary

BACKGROUND: Peripheral artery disease (PAD) is a common circulatory problem in which narrowed arteries reduce blood flow to the limbs. When a person develops PAD, his extremities -- usually the legs -- don't receive enough blood flow to keep up with demand. This causes symptoms, most notably leg pain when walking.

SYMPTOMS: According to the Mayo Foundation for Medical Education and Research, the following symptoms are signs of PAD: • Painful cramping in the hip, thigh or calf muscles after activity such as walking or climbing stairs (intermittent claudication). • Leg numbness or weakness. • Coldness in the lower leg or foot, especially when compared to the other leg. • Sores on the toes, feet or legs that won't heal. • A change in the color of legs. • Hair loss or slower hair growth on the feet and legs. • Slower growth of toenails. • Shiny skin on the legs. • No pulse or a weak pulse in the legs or feet. • Erectile dysfunction in men.

STEM CELLS: According to the article, The Potential of Stem Cells: An Inventory, stem cells are found in all multicellular organisms. They are characterized by the ability to renew themselves through mitotic cell division and differentiate into a diverse range of specialized cell types.

BREAKTHROUGH: A recent research study determined the safety and possible effectiveness of various doses of stem cells. Investigators tested to see if the injection of stem cells would help in creating new collaterals and provide the vital conduit for blood flow to the parts of the leg below the block in patients with PAD. The cells, which were taken from pregnant women's placentas, were delivered with a needle into regions of the leg with claudication. The study, known as Autologous CD34+ Stem Cell Injection for Severe Intermittent Claudication, showed 39 out of 44 patients (approximately 89 percent) with severe PAD who were treated with stem cells had their legs saved from amputation.