Scientists find cells that mend broken heart

Self-repair of damaged heart is routine for zebrafish By Mary Jane Gore

Humans have very limited ability to regenerate heart muscle cells, which is a key reason why heart attacks that kill cells and scar heart tissue are so dangerous.

Fluorescent microscope image of a zebrafish heart 7 days after injury. | Kazu Kikuchi, Poss Lab
But damaged heart muscles in the amazing, highly regenerative zebrafish have given Duke University Medical Center scientists a few ideas that may lead to new directions in clinical research and better therapy after heart attacks.

''Our hearts don't seem so complex that they shouldn't have the capacity to regenerate,'' said Kenneth Poss, Ph.D., senior author of the study in Nature and professor of cell biology at Duke. The data in this study showed that the major contributors to the regeneration of surgically removed heart muscle came from a subpopulation of heart muscle cells (cardiomyocytes) near the area where the removal occurred.

The study appears in the March 25 issue of Nature.

The team labeled cells in the heart and found that cells that activated the gata4 gene upon injury ultimately contributed to regenerating the heart muscle.

The team first used a labeled ''fluorescent reporter'' fish that shows the presence of gata4, a gene required for heart formation in the developing embryo. They found that fluorescence was undetectable in uninjured zebrafish ventricles, but when they clipped a small section of the heart, a subpopulation of cardiac muscle cells along the outer wall of the ventricles began to fluoresce. Some of these cells near the removal site ultimately proliferate and integrate into the wound, replacing the injury clot.