Zebrafish Heart Regeneration | HHMI BioInteractive video

The zebrafish heart is similar to the human heart in many respects. But unlike the human heart, the fish heart closes wounds rapidly and then regenerates to nearly full function.

When the zebrafish heart is damaged, the wound site is rapidly sealed with a fibrin clot that stems bleeding within seconds. Following clot formation, the tissue that surrounds the heart muscle—the epicardium—gradually covers the fibrin clot via migration and cell division. Over the next few months, new cardiac muscle is produced and replaces the clot. Growth factors, like FGF1, produced by the new heart tissue, signals the cells of the epicardial layer to migrate into the heart and form new blood vessels, to provide essential blood flow to the regenerating tissue. Over time, the wounded zebrafish heart returns to nearly its original shape, size, and pumping ability.

Although the human heart is virtually unable to regenerate new muscle when severely damaged, our vertebrate cousin the zebrafish can regenerate cardiac muscle to replace a massive section of damaged heart. Scientists want to understand why fish and humans should have such differing regenerative abilities, and especially hope that understanding how the fish heart regenerates will yield clues for improving therapy after human heart attacks. The zebrafish heart does have some structural differences with the human heart, having only two chambers instead of four, and having a more “spongy” composition that may facilitate clotting. If the role of important molecules like FGF1 can be determined in the zebrafish, the same molecules can then be studied in humans, and even explored as therapeutic agents.