Editor's note: "Life's Work" features innovators and pioneers who are making a difference in the world of medicine.
(CNN) -- Dr. Roberto Bolli's face lights up when he talks about his true love: the human heart.
"The heart is really a miraculous organ. It beats 72 times a minute throughout our life, which means billions of times in our lifetime. And it never gets tired," Bolli says.
"It knows exactly how much blood to pump; it can increase its output by fivefold if we need more oxygen -- for example, if we're running or doing strenuous activity. You have 5 billion cells called myocites, all beating in synchrony, in a perfectly coordinated manner, to maximize the heart's pumping ability. It is an engineering feat that never ceases to amaze me."
Bolli was born in Perugia, Italy, the son of a general practitioner. He came to the United States after finishing medical school in Italy, starting at Baylor College of Medicine in Houston. Since 1994, he's been the chief of cardiology at the University of Louisville, where he also directs the Institute of Molecular Cardiology.
Like most physicians, Bolli was taught that heart cells don't regenerate, and that any cells which die from loss of oxygen during a heart attack are lost forever. But the lesson never quite sunk in.
"That theory always struck me as odd," Bolli says now. "Why would nature demand so much of a single cell, when that same cell must beat 70 times a minute throughout your life? That seems like an unreasonable demand."
Was it possible that new heart cells are constantly born? And could the process be helped along to assist sick patients?
For about a decade, scientists have experimented with the use of stem cells to try and repair the heart, mostly in animals and mostly using stem cells derived from bone marrow. In 2009, Bolli was ready to launch the SCIPIO trial (Cardiac Stem Cells in Patients with Cardiomyopathy).
Stem cells were taken from patients with severe heart failure and multiplied in a laboratory run by Dr. Piero Anversa at Brigham & Women's Hospital in Boston. A few months later, each patient was re-infused with a million of his or her own stem cells.
The results were dramatic. Patients saw scar tissue replaced by working heart muscle and a significant improvement in their hearts' ability to pump blood.
While the numbers are small, other studies have found similarly encouraging results. Bolli has refined his procedure to make it less invasive -- stem cells can now be taken through a catheter -- and none of the patients in cardiac stem cell trials have suffered serious adverse effects. Bolli is hoping to start a larger trial by the fall of 2013.