January 24, 2012
Promising Results In First-ever Trial Of Stem Cell Therapy For The Blind
Scientists have improved the eyesight of two people who were nearly blind by injecting their eyes with stem cells from human embryos.
One patient, a 51-year-old graphic artist, had suffered from Stargardt's disease, the most common form of macular degeneration in young patients, since she was a teenager. Her condition had progressively worsened to the point she was unable to read a single letter on a standard eye chart and was legally blind.
A second patient, aged 78, suffered from dry macular degeneration, the leading cause of blindness in the elderly, and was also legally blind.
The two volunteers showed no signs of adverse effects from the therapy, the scientists said.
The results of the initial tests, which were aimed at evaluating whether the treatment is safe, were reported Monday in The Lancet, and are the first published results of human embryonic stem cell therapy used to improve eyesight.
Embryonic stem cells are highly versatile cells found in early-stage embryos that can differentiate into any tissue of the body.
Scientists have long hoped to harness these cells to form replacements for tissue lost through disease or accidents.
But the mission to use embryonic stem cells has been challenging.
One problem is biological, in that donated stem cells provoke an immune response by the body that cause the cells to be rejected or cause cancer. The other issue is ethical, with critics of the treatment saying the embryos are human life.
In the current study, the stem cells were used at a so-called "immunoprivileged" site -- the eye -- where there is not a strong immune response because of the blood-ocular barrier.
Roughly 50,000 embryonic stem cells that had diversified into replacement cells for the pigmented layer of the retina were transplanted into the two volunteers.
For the following six weeks, the patients received treatment -- which was scaled back over time -- to prevent their immune systems from attacking the newly-implanted cells.
In the first four months after treatment, the scientists found no signs of cancer, rejection or any other problems, and both patients recovered a small amount of vision.
Prior to treatment, the 78-year-old patient was able to read 21 letters on a standard chart of visual acuity. After two weeks of treatment, this rose to 33 letters before settling at a stable ability to read 28 letters, the scientists reported.
The woman with Stargardt's disease went from seeing only hand movements to being able to see single fingers and reading five letters of the alphabet.
"However, that doesn't really capture the difference it has made in their life," said chief scientific officer Bob Lanza in an interview with the AFP news agency.
"The Stargardt's patient reports that she can see more color and has better contract and dark adaptation out of the operated eye. In fact, she started using her computer and could even read her watch... (and) says she can even thread a needle now."
Lanza said that since these improvements occurred in patients who were at a highly advanced stage of the disease, the trials also show promise for patients at an earlier stage of degeneration.
Clinical trials of new drugs or treatments typically undergo a three-phase process, enrolling a progressively larger number of patients to ensure the treatments are first and foremost safe, and, secondly, effective.
The scientists noted that while surgeries sometimes produce false "placebo" benefits for patients, the current treatments showed new retinal cells growing in patches ravaged by blindness in the patient's eyes.
"Ten years ago we told these patients they were going to go blind. These results show a lot of promise to change the landscape," said retinal surgeon Rama Jager of University Retina, who was not involved in the study.
Growth of these new cells is "really spectacular," Jager told USAToday.
"You just don't see that in these patients."
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