The Heart of Tissue Engineering
by David Pescovitz
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version
Multimedia
Movie:
When the injectable hydrogel reaches a temperature above
34 degrees Celsius, it undergoes a phase transformation
and stiffens. (Quicktime movie)
Movie courtesy Kevin Healy
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How do you mend
a broken heart? That's the question being answered, literally, by
Berkeley materials scientists.
Kevin E. Healy, a professor with joint appointments in Berkeley's
departments of Materials Science and Engineering (MSE) and Bioengineering
(BioE), and MSE graduate student Timothy V. Kirk are developing
an injectable gel rife with living cells and bioactive molecules
that could rebuild portions of a heart damaged by disease.
According to the American Heart Association, one in three deaths
in the western world is caused by heart disease. With only 20,000
transplant hearts available each year, there simply aren't enough
spare hearts to go around.
"Organs like the liver and bone are able to regenerate when they're
damaged," Healy says. "Cardiac cells don't proliferate or grow.
You have to go to a renewal source to repopulate a damaged area."
Mouse
heart injected with hydrogel specially-prepared to fluoresce
red. Scale bar indicates 10 microns. Click for larger
image.
Courtesy
Kevin Healy
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Kirk and Healy's renewal source are adult stem cells, undifferentiated
cells that have the capability to develop into specialized cells.
In studies on mice, Healy and Kirk harvested stem cells from the
animal's bone marrow and isolated the sub-population they believed
had the propensity to specialize into cardiac cells.
Professor
Kevin Healy in his O'Brien Hall laboratory with a syringe
of hydrogel.
Peg
Skorpinski photo
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Traditionally,
bioengineers have used stem cells to grow tissue on hard scaffolds,
physical guides for cell growth. The tissue is then surgically implanted
into the body. But Healy and former graduate student Ranee A. Stile
invented a novel hydrogel, a polymer-based matrix containing growth
factors, peptide sequences, and other biomaterials that help direct
the cells' growth into new heart tissue and blood vessels. The polymer
can be injected into the heart with a syringe or catheter.
"When the hydrogel
is room temperature, it's flexible and you can inject it into the
damaged area," Healy explains. "But when it hits body temperature,
it stiffens and enables the cells to grow."
MSE
graduate student Timothy V. Kirk.
Angela
Privin photo
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So far, the researchers,
with collaborators at Children's Hospital Oakland Research Institute,
have injected their hydrogel, without stem cells, into a beating
mouse heart and observed how it spreads through the organ before
hardening. And most recently, Kirk and Healy cultured bone marrow
cells in the hydrogel ex vivo and observed huge expansion of the
bone marrow.
"Independent of the cardiac applications, this may turn out to be
a useful approach to expand numbers of stem cells," Healy says.
The next step is to study any genetic changes the cells undergo
during expansion and then inject the stem cell-seeded hydrogel into
a mouse heart in the hopes of regenerating damaged heart tissue.
If their experimental success continues, Healy and Kirk believe
that the technology could be tested on humans within seven years.
"I'd like to take a research project all the way from basic science
to use by clinicians," Kirk says. "This research has the promise
and the potential to benefit a great number of people."
Kevin E. Healy's Home Page
Biomaterials at UC Berkeley
"Making the Human Body More Hospitable"
Lab Notes is published online by the Public Affairs Office of the UC Berkeley College of Engineering. The Lab Notes mission is to illuminate groundbreaking
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Updated 11/26/02.
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