A tiny, tropical fish that can regenerate parts of its heart may help scientists find a way to help humans grow new cardiac cells to replace damaged ones.

The zebrafish, about the size of a small minnow, can regenerate cardiac muscle even when 20 per cent of its heart has been removed.

A team of scientists headed by Dr. Mark Keating of Harvard University found a gene in the zebrafish that appears to be the key to this healing process. Keating said the finding could lead to human cardiac regeneration.

In an article in the journal Science, Keating suggests "it is likely that there are corresponding genes in the human genome."

The black-and-white striped zebrafish is about 2.5 centimetres long. It can regrow fins and eye parts as well as heart cells.

The scientific experiment consisted of cutting into the fish's abdomen – the fish were anesthetized – then removing 20 per cent of the fish's two-chambered heart.

The fish was returned to the water and in 10 days recovered well enough to swim normally. Within two months the zebrafish had replaced the parts of its heart that had been removed, with little or no scarring.

Keating says a human can recover from a heart attack, but the human heart never regrows heart muscle. Instead, scar tissue replaces cells killed by the heart attack.

Scientists now will concentrate their research on the genes the zebrafish use to grow new heart muscle cells.