91av

REPAIRING a damaged heart suddenly seems possible. Two teams of scientists
report that stem cells can fix some of the damage caused by heart attacks. The
techniques could be tested in people as early as next year.

The havoc caused by a heart attack comes in two stages. Minutes after a
coronary artery is blocked, heart muscle cells begin to suffer from the lack of
oxygen and nutrients. If doctors don鈥檛 clear the blockage immediately, the cells
die and the heart is permanently damaged.

Days or weeks later, the heart compensates by 鈥渞emodelling鈥�, enlarging the
muscle cells so they can pump harder. But this valiant effort is often futile.
The lowered blood supply can鈥檛 support the increased effort of the cells and
causes more of them to die, thinning and weakening the heart muscle.

Now a team led by Piero Anversa of New York Medical College in Valhalla has
shown that stem cells鈥攗ndifferentiated cells that can give rise to many
specialised types鈥攃an repair some of the immediate damage that is caused
by heart attacks.

The researchers first induced heart attacks in mice. A few hours later, they
injected stem cells taken from mouse bone marrow directly into the heart
wall.

After nine days, the transplanted cells had regenerated 68 per cent of the
damaged muscle and increased blood flow. The function of the heart improved by
33 per cent. 鈥淲e saw that and we were screaming like kids,鈥� says Anversa. In a
few months, his team will start experiments in monkeys, he says. The technique
may be tested on people within three years.

Another team led by Silviu Itescu at Columbia-Presbyterian Medical Center in
New York has used stem cells to restore the heart鈥檚 blood supply and prevent
further damage after a heart attack. 鈥淓ven if you lose just a bit of your heart
in the initial attack, the damage extends and you end up in heart failure
again,鈥� says Itescu.

He and his colleagues purified human angioblasts鈥攂one marrow stem cells
that form blood vessels during the development of the embryo. These cells were
injected into rats two days after heart attacks had been induced.

The cells created new blood vessels in the damaged area and caused nearby
blood vessels to branch, improving heart function by 26 per cent. Because Itescu
can already isolate these cells from people, he says his team may be able to
start clinical trials within a year.

Other researchers are cautiously optimistic. 鈥淭here have been 20 years of
disappointing experiments trying to replace cells in the heart,鈥� says Mark
Sussman, a cardiovascular molecular biologist at The Children鈥檚 Hospital and
Research Foundation in Cincinnati, Ohio. 鈥淭his new work looks very promising,
but we need to understand why it is working and if we can get even better
谤别蝉耻濒迟蝉.鈥�