Why is a newborn mouse like a zebrafish? Because their hearts can heal – something impossible for adult mammals. The findings could lead to new treatments for heart disease in people.
Some fish and amphibians – zebrafish, for example – can regenerate heart tissue when it is damaged. They can do this throughout their life, whereas adult mammals can't: only mammalian embryos were known to have the ability. Intriguingly, before the heart of a developing mammalian embryo separates into four chambers, it looks similar to the two-chambered zebrafish heart.
To find out if mammals retain this heart-healing ability after birth, Enzo Porrello and colleagues at the University of Texas Southwestern Medical Center in Dallas turned to newborn mice.
They cut out a chunk of heart tissue – around 15 per cent of the left ventricle – from 1-day-old mice. When the group removed the whole organ 21 days later, they found that 99 per cent of the hearts had completely regenerated.
To find out whether regenerated hearts work properly, the team compared other heart-damaged newborn mice with mice that had been given a sham operation that did not touch the heart. Two months after the surgery, an echocardiogram showed that the regenerated hearts were functioning as well as the undamaged ones.
When the group repeated the surgery in 7-day-old mice, the hearts did not heal, suggesting that the regenerative ability was lost by this age.
**Published in "New Scientist"