Researchers have found that gene therapy not only reverses blindness in those who have Leber's congenital amaurosis Type 2 (LCA2) but can also restore visual pathways in the brain even after years of low activity.
In a study published in the journal Science Translational Medicine, researchers from the University of Pennsylvania's Perelman School of Medicine and The Children's Hospital of Philadelphia detailed the use of gene therapy on LCA2 patients and how the use of the treatment not only led to sight restoration but the reactivation as well of brain connections related to sight.
There were 10 patients part of the study and each one were administered gene therapy on their worse-seeing eye. The subjects' brain images were taken around two years later and the researchers found that brain pathways related to the patients' treated eyes and those associated with untreated eyes were vastly different.
"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," said Jean Bennett, M.D., Ph.D., and senior author for the study.
LCA2 is a rare disease affecting people who have inherited bad copies of the LCA2 gene from both their parents. The condition limits visual functions at birth before leading to slow retinal degeneration that worsens to progressive loss of vision. By the time a patient is in mid-life, they would have completely lost their sight.
But with gene therapy, it was common for LCA2 patients to go from being almost blind or already blind to being able to partially see and eventually being able to navigate almost normally.
Several experiments were then conducted to see how well visual processing connections in the brain recover once sight is restored. Deep brain connections were revealed with an advanced MRI method, showing that connections were strong in those related to a patient's treated eye. In fact, they were comparable to connections observed in the control group, implying that the brain pathways had rebuilt themselves following sight restoration, even at an age when the nervous system's ability to rewire itself has been significantly reduced.
Further tests confirmed that as the treated eye is used, the stronger the associated brain connection becomes.
The patients part of the study have since received gene therapy in their then-untreated eye.
Hui Zhang, Chris Baker, Philip Cook, Albert Maguire, Laura Cyckowski, James Gee, Kenneth Shindler, Arastoo Vossough, Kathleen Marshall and Puya Aravand also contributed to the study.
Photo: Ahmed Sinan | Flickr