Stem cells have been used in
the treatment of multiple sclerosis, leukemia, lupus,
thrombocytopenia and the list goes on. Add this to the
equally long list of their potential uses in curing diseases
like Alzheimer's, diabetes and Parkinson's, and it's not
difficult to see why stem cells have won the hearts of
many with their chameleon-like ability to morph into just
about any cell in the body.
Speaking of hearts, you can now
chalk up yet another potential use for these incredible
cells. Researchers headed by Dr Ronald Li of Johns Hopkins
University have shown that human cardiomyocytes derived
from genetically engineered human embryonic stem cells
can kick-start malfunctioning ventricular cardiomyocytes
and act as a pacemaker in rats and guinea pigs.
MOVE
TO THEIR OWN BEAT
The research published in the December 20 online edition
of Circulation documents how Dr Li and his colleagues
engineered the stem cell-derived cardiomyocytes and
were successful in getting the cells to beat on their
own. The cells were then added to a cell layer of non-beating
ventricular myocytes obtained from neonatal rats. After
only a few days, the newcomer cells induced "rhythmic
electrical and contractile activities," reported the
researchers.
Up to this point, the research
was exciting but not novel. In 2003, researchers at
the University of Wisconsin had also succeeded in getting
isolated cardiomyocytes to move to the beat in cell
culture. But in this latest research Dr Li and colleagues
moved the bar up, by demonstrating that the cadence
of the beating cells was responsive to drugs used clinically
to ratchet the heart rate up or down.
Then came the kicker. The researchers
took the engineered cardiomyocytes in vivo, implanting
them into the left ventricle of guinea pigs whose heart
rate had been experimentally suppressed. Lo and behold,
the implanted cells triggered regular contractions of
the heart. These findings pave the way for a future
in which folks with malfunctioning tickers can receive
pacemakers comprised of living cells, as opposed to
the mechanical devices that are today's life-saving
staple.
BATTERIES
run out
"While electronic pacemakers are effective, they are
associated with significant expenses and various complications
such as bleeding and infection, and the batteries need
to be replaced," Dr Li commented in an interview with
Reuters Health. Further, a living pacemaker could potentially
adjust its beat to the changing chemistry of the body,
much as the heart does naturally. "Unlike a [human embryonic
stem cell]-derived biopacemaker, electronic devices
also do not respond to endogenous neurohormonal controls,"
said Dr Li in the same interview.
Dr Li foresees a day when different
heart types will be engineered for transplantation,
eliminating the need for donors. "Our results lay the
ground work for creating a self-renewable library of
genetically-engineered specialized human cells with
customized phenotypic properties ... for achieving different
therapeutic goals," he notes on his website.
There are some 100,000 Canadians
who have pacemakers implanted in their chests, according
to the Heart and Stroke Foundation of Canada. Each year
their numbers swell by about 10,000.
December 20 online edition of Circulation
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