Heart valves grown from womb fluid cells
By LINDSEY TANNER, AP Medical Writer
Wed Nov 15, 6:07 PM ET
CHICAGO - Scientists for the first time have grown human heart valves
using stem cells from the fluid that cushions babies in the womb —
offering a revolutionary approach that may be used to repair defective
hearts in the future.
The idea is to create these new valves in the lab while the pregnancy
progresses and have them ready to implant in a baby with heart defects
after it is born.
The Swiss experiment follows recent successes at growing bladders and
blood vessels and suggests that people may one day be able to grow
their own replacement heart parts — in some cases, even before they're
even born.
It's one of several sci-fi tissue engineering advances that could lead
to homegrown heart valves for infants and adults that are more durable
and effective than artificial or cadaver valves.
"This may open a whole new therapy concept to the treatment of
congenital heart defects," said Dr. Simon Hoerstrup, a University of
Zurich scientist who led the work, which was presented Wednesday at an
American Heart Association conference.
Also at the meeting, Japanese researchers said they had grown new
heart valves in rabbits using cells from the animals' own tissue. It's
the first time replacement heart valves have been created in this
manner, said lead author Dr. Kyoko Hayashida.
"It's very promising," University of Chicago cardiologist Dr. Ziyad
Hijazi said of the two studies. "I don't doubt" that it will be
applied one day in humans, he said.
One percent of all newborns, or more than 1 million babies born
worldwide each year, have heart problems. These kill more babies in
the United States in the first year of life than any other birth
defects, according to the National Institutes of Health.
Heart valve defects can be detected during pregnancy with ultrasound
tests at about 20 weeks of pregnancy. At least one-third of afflicted
infants have problems that could be treated with replacement valves,
Hoerstrup said.
"It could be quite important if it turns out to work," said Dr. Robert
Bonow, a Northwestern University heart valve specialist.
Conventional procedures to fix faulty heart valves all have drawbacks.
Artificial valves are prone to blood clots and patients must take
anti-clotting drugs for life. Valves from human cadavers or animals
can deteriorate, requiring repeated open-heart surgeries to replace
them, Hijazi said. That's especially true in children, because these
valves don't grow along with the body.
Valves made from the patient's own cells are living tissue and might
be able to grow with the patient, said Hayashida, a scientist at the
National Cardiovascular Center Research Institute in Osaka.
The Swiss procedure has another advantage: using cells the fetus sheds
in amniotic fluid avoids controversy because it doesn't involve
destroying embryos to get stem cells.
"This is an ethical advantage," Hoerstrup said at the meeting.
Here's how the experiment worked:
Amniotic fluid was obtained through a needle inserted into the womb
during amniocentesis, a prenatal test for birth defects that is often
offered to pregnant women aged 35 and older.
Fetal stem cells were isolated from the fluid, cultured in a lab dish,
then placed on a mold shaped like a small ink pen and made of
biodegradable plastic. It took only four to six weeks to grow each of
the 12 valves created in the experiment.
The researchers said lab tests showed they appeared to function
normally.
The next step is to see if they work in sheep, a two-year experiment
that Hoerstrup said is under way.
He and co-researcher Dorthe Schmidt called their method "a promising,
low-risk approach enabling the prenatal fabrication of heart valves
ready to use at birth."
Hoerstrup said amniotic stem cells also can be frozen for years and
could potentially be used to create replacement parts for aging or
diseased valves in adults, too.
The research is preliminary and experts say implanting
tissue-engineered human valves in human hearts is likely years away.
But it's not as far-fetched as it sounds.
Earlier this year, U.S. scientists reported re-engineering seven
diseased bladders with tissue grown from the patients' own cells.
And last year, researchers reported that two kidney dialysis patients
from Argentina had received the world's first tissue-engineered blood
vessels, fashioned from their own skin and vein tissue.
Dr. John E. Mayer Jr., a Children's Hospital Boston heart surgeon and
tissue engineering pioneer, said scientists are optimistic that this
area of research will revolutionize how people with valve disease will
be cared for in the future.
About 250,000 patients worldwide have surgery to replace heart parts
each year, according to Mayer.
In one of Mayer's experiments, heart valves fashioned from stem cells
harvested from sheep bone marrow appeared to function normally when
implanted in sheep. A similar experiment used cells harvested from
sheep arteries.
Hoerstrup said amniotic fluid is potentially a richer source of stem
cells than other sources.
Mayer said the big question is whether stem cells from amniotic fluid
can create valves superior to those made from other cell types.
"I'm pretty sure the ball will continue to be advanced down the
field," Mayer said. "We'll get there one way or the other."
--
Wherever I go it will be well with me, for it was well with me here, not
on account of the place, but of my judgments which I shall carry away
with me, for no one can deprive me of these; on the contrary, they alone
are my property, and cannot be taken away, and to possess them suffices
me wherever I am or whatever I do. -- EPICTETUS
"There are no absolute certainties in this universe. A man must try to
whip order into a yelping pack of probabilities, and uniform success is
impossible." -- Jack Vance
"Civilization is the interval between Ice Ages." -- Will Durant.
"Progress is the increasing control of the environment by life.
--Will Durant
Joseph R. Darancette
daranc@NOSPAMverizon.net
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