February 23, 2007

Lecture gets to the heart of cardiac regeneration

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Antonis Hatzopoulos, Ph.D., discussed the regenerative ability of stem cells at last week’s Discovery Lecture. (photo by Mary Donaldson)

Lecture gets to the heart of cardiac regeneration

Punished by Zeus for stealing fire from the gods, Prometheus was sentenced to have part of his liver (or heart, according to some sources) pecked out each night by a golden eagle.

This myth reflects the ancient recognition that some organs have the ability to regenerate — a capacity that modern medicine is trying to harness to treat a range of ailments.

At the Feb. 15 Discovery Lecture, Antonis Hatzopoulos, Ph.D., associate professor of Medicine and Cell and Developmental Biology, detailed recent efforts to better understand and exploit the regenerative ability of stem cells repairing heart damage.

“As time goes by, we start losing cells,” Hatzopoulos said. “In regenerative medicine, we try to restore some of this lost tissue in order to save lives as well as improve the quality of life.”

The body's tissues have a wide range of regenerative capacity, he noted — from skin and blood cells that regenerate easily to the brain, pancreas and heart, where regeneration is probably very limited or nonexistent.

The ability to regenerate is conferred by either resident populations of stem cells that can give rise to new tissue cells when needed (e.g., in skin and blood), adult cells that retain the ability to divide and grow (as in the liver), or a combination of the two.

“When it comes to cardiac regeneration, it looks like the heart has none of these mechanisms,” said Hatzopoulos.

Recently, some studies have indicated that the heart may have a very small reserve of stem cells, Hatzopoulos noted.

But until those cells can be identified and isolated, he said, “scientists have turned to other sources of stem cells to see if they would be able to repair damaged heart tissue.”

Several recent clinical trials examining the ability of bone marrow-derived stem cells in repairing damaged heart tissue after heart attack have shown that such therapies are safe and may offer a “moderate” improvement in heart function.

But optimizing the stem cell approach also will require a deeper knowledge of the factors that induce stem cells to produce new heart cells.

Hatzopoulos described some of his basic research aimed at understanding how stem cells work — how they find their way to damaged tissue and what cellular factors help instruct stem cells to differentiate into heart cells.

Hatzopoulos and colleagues have identified numerous proteins that may have “cardiogenic” properties, which they are now testing in animal models to determine their effects on heart development and regeneration.

“What we are trying to do is find factors that will push these cells towards the cardiac lineage in a more effective way,” said Hatzopoulos.

“The practical application …would be that if we put these factors together with stem cells and transplant them in the heart, that they will increase the yield of stem cells that become heart cells.”

For a complete schedule of the Discovery Lecture Series and archived video of previous lectures, go to www.mc.vanderbilt.edu/discoveryseries.