Long-lived stem cells heal heart attacks

HELEN PEARSON

Heart failure affects 23 million people worldwide. © Getty Images

Injections of hardy stem cells have helped rats to recover from a heart attack. But researchers are still arguing about the value of such cells for human patients.

Hopes for the stem-cell treatment were raised in 2001 when two reports revealed that mouse bone-marrow stem cells, which normally make blood, had patched up damaged heart tissue. But in many ensuing studies, more than 90% of cells pumped into the heart died within 2 days.

In the latest advance, Victor Dzau and his colleagues at the Brigham and Women's Hospital in Boston inserted a cell-survival gene called Akt1 into a type of bone-marrow stem cell1. They injected the cells into rats whose hearts had been starved of oxygen as happens when blocked arteries cause a heart attack.

More than 60% of the modified cells survived for 48 hours. What's more, they halted the heart's subsequent decline towards failure. "It's pretty amazing," says Stanton Gerson, who studies blood stem cells at Case Western Reserve University in Cleveland, Ohio.

The result bolsters the idea that stem cells could mend human hearts after an attack. Proponents also point to positive results from first-stage clinical trials in which heart-attack patients are injected with their own blood cells. "The controversy is over," states heart researcher Piero Anversa of New York Medical College in Valhalla.

Others question whether stem cells will be safe or effective in people. Some human studies, for example, have lacked appropriate control groups, argues Charles Murry, who studies heart failure at the University of Washington in Seattle. "One needs to be enthusiastic but sceptical," he says.

Heart of the matter

Some of the dispute arises because different research groups tend to use different techniques, making their results incomparable. Dzau works with mesenchymal stem cells, which normally produce muscle and bone; other studies have used slightly different types of stem cells.

It is not clear how stem cells heal the heart. They may spawn new muscle cells, fuse with existing cells or simply prompt the cells to repair and grow themselves. "It's an intellectual question that will take years to sort out," says Gerson.

Nonetheless, advocates argue that preliminary human trials on the safety of stem-cell therapy should continue because the need is so great. An estimated 23 million people worldwide are affected by heart failure.

Wary researchers warn that a single incident in which, say, stem cells trigger a heart tumour, could condemn the field. "I think we need to be really careful," says Murry.

1. Mangi, A.A. et al. Mesenchymal stem cells modified with Akt prevent remodeling and restore performance of infracted hearts. Nature Medicine, AOP doi: 10.1038/nm912, (2003). |Article|

© Nature News Service / Macmillan Magazines Ltd 2003