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Gene Therapy May Not Only Restore Vision, But Strengthen Visual Pathways in Brain

Created July 23, 2015 by in Retina Stories
lca

 

The use of gene therapy in restoring vision has been an active subject in clinical trials since 2007 and has yielded miraculous results for children and adults who were previously thought to endure blindness for the rest of their lives.

The focal point of these studies has been Leber’s congenital amaurosis, a rare hereditary disease that has been the leading cause of blindness in infants. LCA causes a slow degeneration of the retina, ultimately leading to complete blindness in untreated individuals as young as forty. With gene therapy, many have seen dramatic improvements in their vision and their quality of life, progressing from complete blindness to being able to see normally.

One of the less understood elements of this research has been its effect on the brain. When it comes to visual processing, the eye is but one piece of the puzzle; in order for vision to be processed successfully, certain pathways to the brain must be functional as well. After years of blindness or near blindness, how well can these pathways regenerate, particularly in adults? The author of the most recent study, Manzar Ashtari of University of Pennsylvania’s Perelman School of Medicine, sought to investigate the effects of the therapy on neuroplasticity and these visual pathways.

“The patients had received the gene therapy in just one eye, their worse seeing eye, and though we imaged their brains only about two years later, on average, we saw big differences between the side of the brain connected to the treated region of the injected eye and the side connected to the untreated eye,” Ashtari states in his report.

Senior author Jean Bennett adds, “It’s an elegant demonstration that these visual processing pathways can be restored even long after the period when it was thought there would be a loss of plasticity.”

Using advanced MRI techniques to examine the connection pathways of the brain, Ashtari compared the visual pathways of recipients of the gene therapy to a control group of normal-sighted individuals. The trial yielded two important discoveries:

1) There was a rapid regrowth in these previously untapped brain connections in adult individuals aged 20-45, an age group thought to suffer from a significant loss in neuroplasticity, and
2) The more time that had passed since the treatment, the more these neuropathways had improved, whereas the untreated eye saw a progressive decline in the efficacy of its visual pathways.

“Brain plasticity is not just for kids – it is for all ages,” Ashtari stated.

The FDA is expected to review the conclusions of this trial within the next year, and their findings could lead to the approval of the first gene therapy drug in the United States.

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