It's not often researchers dare use the "cure"
word, especially when referring to a major cause of death
like heart attack. But that word is indeed being bandied
about by Johns Hopkins researchers following the remarkable
results of a trial reported in the Proceedings of the
National Academy of Sciences, in which myocardial
tissue was regenerated in pigs using stem cells harvested
from bone marrow.
"There is reason for optimism
about these findings, possibly leading to a first-ever
cure for heart attack in humans," said Dr Joshua
Hare, a cardiologist and professor of medicine at the
Heart Institute of the Johns Hopkins University School
of Medicine. "If a treatment can be found for the
damage done by a heart attack to heart muscle, then
there is the potential to forestall the serious complications
that traditionally result from a heart attack."
WHERE
THERE'S A WILL
This isn't the first time that stem cells have been
injected into infarcted animal hearts, but the study
employed novel techniques that appear to have made all
the difference. First, the type of stem cells used was
peculiarly well-suited to cardiac repair. Also, the
cells were taken from different pigs ? a huge advantage
in practice as it means that these cells need not come
from the heart attack victim himself. A novel delivery
method also came in handy. Previous research used intracoronary
injections but the large size of these bone marrow cells
makes it difficult for them to penetrate the infracted
tissue and may even cause microvascular obstruction.
In the latest study, the researchers injected stem cells
directly into damaged tissue, resulting in more tissue
regeneration and an actual reduction in risk of sudden
death.
The results were dramatic. Eight
weeks after MI, six pigs treated with MSCs averaged
less than a quarter of the scar tissue of six treated
with placebo. They also showed vast improvement in heart
function. While the ejection fraction of placebo-treated
pigs dipped then stabilized following MI, in the MSC-treated
pigs it climbed and was still rising fast at the eight-week
cutoff. "Ultimately, the goal is to develop a widely
applicable treatment to repair and reverse the damage
done to heart muscle," said Dr Hare. To that end,
48 MI patients are now being enrolled in a Phase I clinical
trial, which will report its findings in mid-2006.
Proc Natl Acad Sci Epub
ahead of print Aug 1, 2005
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