Dr. Jean Bennett, a gene therapist
at the University of Pennsylvania, and her colleagues, began treating people
who are blind with injections of a harmless virus that inserts good copies of
genes that are defective in the patient. The genes were inserted into the cells
of the retina. The retina is a light sensitive tissue at the back of the inner
eyeball. Its job is to receive light and convert that light into neural signals
to which the brain uses for visual recognition.
In 2007, researchers began conducting
gene therapy clinical trials on ten patients with Leber’s congenital amaurosis
Type 2. Leber’s congenital amaurosis Type 2 causes a degeneration of retinas
thus limiting vision at birth and progressive blindness by mid life. The ten
patients, ages ranging from 20-45, underwent gene therapy only in one of their
eyes, the one which had the worst vision. After gene therapy for two or three
years, researchers used an MRI to scan deep into the patients’ brains. The MRI
showed the visual pathways in each patient was nearly as strong and healthy as
a normal persons vision at that age. The MRI scan also showed the untreated
eyes had much weaker visual pathways. This observation suggested that regaining
sight also helped to rebuild the visual pathways in the brain. This revision is
called brain plasticity.
The data collected from this study
hinted that the patients’ visual pathways were in better condition after more
and more time had elapsed since undergoing gene therapy. Because the pathways
improve as more signals get sent through, Bennett and her colleagues are
working on larger phase trials to determine whether their gene therapy can be
used more widely as treatment.
This article and the research
behind it were truly remarkable. The patients undergoing gene therapy are in
their 20’s, and one patient was 45. This age range demonstrated visual pathways
and brain plasticity could be improved at any age, not just young children. I
found this article to be extremely uplifting and encouraging in the field of
gene therapy. The ability to use gene therapy in repairing a person’s sight that
had been nearly blind is just so moving.
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