Adult stem cells are found throughout the body -- in the brain, bones, muscle, skin and blood -- which help heal the body after injury. But now, researchers are using high concentrations of these cells to actually build new arteries in adult patients.
"What we do is actually take them out and find the right amount of cells and specifically put them into targeted areas," said Dr. Amit Patel, director of the Cardiac Stem Cell Therapies at The McGowan Institute for Regenerative Medicine, University of Pittsburgh Medical Center.
Results in more than 100 patients show that, within just three months after the stem cell injections, patients see a significant improvement in blood flow to the heart. The heart muscle itself actually doubles its ability to squeeze or contract.
Researchers say these adult stem cells might help tens of millions of heart patients each year.
"It could be patients who are receiving stents, who are recovering from coronary bypass surgery, patients with heart failure," said Patel. "All of these patients have the potential to benefit from this therapy."
Doctors at Chicago's Northwestern Memorial Hospital have started injecting adult stem cells into the leg to grow new arteries there. Jeremy Kotner, 27, had so little blood flow in his right leg he was at risk of having it amputated.
"You can see where the vessel is blocked," said Dr. Richard Burt while examining Kotner's X-ray. "You can see the blood flowing and then it just stops. Now, three months later after injection of stem cells in that area, you can see that there's a new vessel bringing the blood."
Burt, a specialist in autoimmune diseases, performed the world's first adult stem cell transplant at Northwestern.
"The pain is gone," said Kotner. "I can walk farther and because of that, I feel a lot better."
Many researchers emphasize that early success with these adult stem cells does not replace the need for greater research on embryonic stem cells, which appear more versatile and could potentially treat more diseases.
But when it comes to building blood vessels, using one's own cells could become a common treatment with just a couple of more years of testing.
ABC News' John McKenzie filed this report for "World News Tonight."