(Reuters) -
Before treatment, the 51-year-old graphic artist was legally blind, unable to
read a single letter on a standard eye chart. She has suffered from Stargardt's
disease, the most common form of macular degeneration in young patients, since
she was a teenager, and it was getting progressively worse.
A second
patient, aged 78, suffered from dry macular degeneration - the leading cause of
blindness in the elderly -and could not even see well enough to go shopping.
But after
being treated with stem cells from a donated human embryo, both women have
improved dramatically, researchers said on Monday. Stem cells are master cells
that can differentiate into any of the 200 kinds of cells in the human body.
Their
results are the first-ever report of the medical use of stem cells taken from
human embryos, making them crucial barometers of whether the controversial
technique will ever find widespread therapeutic uses.
In a paper
published online in The Lancet on Monday, physicians at the University of California,
Los Angeles, and scientists at biotechnology company Advanced Cell Technology
report that the first two patients in the clinical trial suffered no adverse
health effects from the treatment and seem to have benefited from it.
A week
after having cells derived from a days-old embryo injected into her eye, the
graphic artist could count fingers, and after one month she could read the top
five letters on the eye chart. She can see more color and contrast, has started
using her computer, and for the first time in years can read her watch and
thread a needle. The macular degeneration patient recently went to the mall for
the first time in years.
The safety
findings, not any vision improvement, is what people should focus on, said
Dusko Ilic, senior lecturer in stem cell science at Kings College London, who
was not involved in the work.
"If
everyone expects that the blind patients will see after being treated ... it
will end up as disaster," he said.
Nevertheless,
advocates for the blind are already hailing the results. "At last we are
seeing fruits of human embryonic stem cell research entering clinical
trials," said Peter Coffey, Director of the London Project to Cure
Blindness.
OBJECTIONS
AND RISKS
Using human
embryonic stem cells for research or treatment has incited controversy for
ethical and medical reasons. Some opponents argue that because removing stem
cells from days-old human embryos almost always destroys the embryo, the
technique amounts to murder.
ACT is the
only company currently testing human embryonic stem cells in study patients.
Last November, stem-cell pioneer Geron announced that it was halting what had
been the first-ever clinical trial of the cells-testing them in patients with spinal
cord injuries-and leaving the field.
When Robert
Lanza, chief scientific officer of ACT, approached ophthalmic surgeon Steven
Schwartz of UCLA about leading the clinical trial, Schwartz asked for ethical
advice from two of his patients: elderly nuns. They gave him the go-ahead, he
said last year.
Even
scientists who support stem cell research argue that they could be dangerous to
use therapeutically. The very property that makes them so valuable in research
- stem cells can morph into any of the kinds of cells in the human body - also
makes them risky.
They can
form teratomas, a type of tumor that arises when stem cells differentiate into
a profusion of cell types.
Another
concern is that transplanting cells derived from human embryos could be rejected
by the patient's immune system. The ACT team got around that by targeting the
eye, which is an "immunoprivileged" site that does not produce a
strong immune response to foreign tissue.
In the
study, physicians led by Schwartz injected what are called retinal epithelial
cells into one eye of each patient. RPE cells lie at the back of the eye and
bathe the retina's rods and cones in substances called growth factors. When RPE
cells die, as they do in macular degeneration, so do the photoreceptors, eventually
causing blindness.
Transplanting
RPE cells grown from stem cells, Lanza reasoned when he began this research
almost a decade ago, might rejuvenate the eye's rods and cones, restoring lost
vision.
To produce
RPE cells, Lanza and his colleagues arranged to obtain days-old embryos created
by in vitro fertilization. The parents, who no longer wanted the embryos,
donated them for research. The scientists then removed a single stem cell from
one embryo, grew it in the lab to obtain millions of cells, and differentiated
them into RPE cells.
The primary
purpose of the clinical trial was to determine whether the implanted cells
caused any harm. So far, neither patient has experienced inflammation, an
indication that their immune system is not attacking the foreign cells.
And there
is no evidence that a teratoma formed in either patient. Researchers also found
that the RPE cells still survive after being implanted four months ago.
NOT A CURE
FOR THE BLIND
The goal of
the study was to determine safety and, at most, see whether the therapy can
slow down or arrest vision loss, not restore it. "The fact that we're
seeing measurable improvements in their vision, persisting for more than four
months, is a bonus," Lanza said in an interview.
Although
rods and cones cannot be brought back from the dead, he explains, "until
you lose them completely you can rescue them." He believes that the
transplanted RPE cells both bathed the deteriorating rods and cones in
nourishing growth factors and gobbled up fragments of dead rods and cones,
keeping the retinal environment healthier for the survivors.
The UCLA
physicians plan to enroll a total of 12 Stargardt's patients and 12 macular
degeneration patients in the ongoing clinical trial, with groups of three
patients each receiving a different number of retinal epithelial cells.
The two
patients being reported on Monday each received the smallest dose, 50,000
cells. Other patients will receive at least twice that many. The trial is also
expanding across the Atlantic: the first patient was treated at Moorfields Eye
Hospital in London last Friday. In a later trial, they hope to treat patients
with earlier-stage disease, before so much of their vision has been lost.
David
Prentice of the Family Research Council, a pro-life group that has opposed the
use of human embryos for research, says the results will require more scrutiny.
"You
have to follow the patients longer to know if it's safe," he told Reuters.
"People will also want to know if there are other routes to the same
end," using sources of stem cells other than human embryos.
Lanza is
planning just that. He believes that skin cells "re-programmed" to
revert to embryonic status might prove just as good a source or RPE and other
specialized cells as human embryonic stem cells. Called IPS (for "induced
pluripotent stem") cells, they can be derived from a patient's own skin
cells and pose no risk of immune rejection.
"I
think we can be up and running in the clinic with IPS cells in one or two
years," Lanza says.
(Additional
reporting by Kate Kelland in London; Editing by Michele Gershberg and Cynthia Osterman)
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| (Photo: Urban don) |
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