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Mending broken hearts - Stem cell could soon be used to repair the effects of heart attack.
11:18 02 April 2001
Two
teams 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.
Researchers
led by Piero Anversa of New York Medical College in Valhalla first
induced heart attacks in mice. A few hours later, they injected stem
cells - primitive cells that can give rise to many specialised types -
taken from mouse bone marrow directly into the heart wall.
After
nine days, the transplanted cells regenerated 68 per cent of the
damaged muscle and increased blood flow. The function of the heart
improved by 33 per cent.
"We saw that and we were screaming like kids," says Anversa.
Another
team led by Silviu Itescu at Columbia-Presbyterian Medical Center in
New York used stem cells to restore the heart''s blood supply and
prevent further damage after a heart
attack. "Even if you lose just a
bit of your heart in the initial attack, the damage extends and you end
up in heart failure again," says Itescu.
Other
researchers are cautious, however. "There have been 20 years of
disappointing experiments trying to replace cells in the heart," says
Mark Sussman, a cardiovascular molecular biologist at The Children''s
Hospital and Research Foundation in Cincinnati, Ohio.
"This new work looks very promising, but we need to understand why it is working and if we can get even better results."
The
havoc caused by a heart attack comes in two waves. Minutes after a
coronary artery is blocked, heart muscle cells begin to suffer from the
lack of oxygen. If doctors do not clear the blockage immediately, the
cells die and the heart is permanently damaged.
Days
or weeks later, the heart compensates by "remodelling", enlarging the
muscle cells so they can pump harder. But this valiant effort is often
futile. The ongoing death of blood vessels cuts off the blood supply
and causes more cells around the damaged area to die, thinning and
weakening the heart muscle.
Itescu''s
team purified human angioblasts - bone marrow stem cells that form
blood vessels during embryonic development. 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. As
Itescu can already isolate these cells from people, he says his team
may be able to start clinical trials within a year.
Anversa''s team will start experiments in monkeys within months. The technique may be tested on people in three years.
More at: Nature (vol 410, p 701), Nature Medicine (vol 7, p 433)