The human eye is an incredibly complex organ, and researchers continue to actively investigate how the eye functions and, in some cases, why it does not. An estimated 36 million people worldwide are blind, and an additional 217 million people have moderate to severe impairment of their vision. How many of these cases are avoidable? How can science help us reverse visual impairment and even blindness?
Reversing Blindness with Gene Editing
The most common genetic condition affecting vision is known as retinitis pigmentosa. Globally, around 1.5 million children are born with retinitis pigmentosa, a condition which causes the cells on the retina to deteriorate over time. This usually starts with a loss of night vision, followed by tunnel vision, and eventually can end in blindness.
Since retinitis pigmentosa is a genetic condition, it is caused by a genetic mutation. If cells from a healthy retina can be inserted into the eye, they could dominate over the cells with the mutation to either slow or stop the retinal degeneration. However, using cells from someone else’s healthy retina runs the risk of the foreign cells not being accepted by the new host body. Fortunately, new approaches to gene editing like the CRISPR/Cas9 enzyme mean that we can snip out unwanted sections of our own genes.
In a recent study published in the journal Nature, researchers took skin cells from patients with retinitis pigmentosa and used a known technique for turning them into multipurpose cells (called pluripotent stem cells). They then removed the mutation through CRISPR gene editing. When they tested the cells 10 days later, the mutation was still gone. The next steps will be to test whether the cells can be put back into the afflicted retina with positive results.
Researchers are also looking at reprogramming the eye’s own cells to address congenital issues like retinitis pigmentosa and other degenerative diseases like age-related macular degeneration. For example, scientists from the National Eye Institute (part of the National Institutes of Health in the U.S.) recently found that Muller glia, cells that act as connective support between neurons in the eye—or, in other words, retinal glue—could be reprogrammed to function as photoreceptors in the eyes of mice that were born blind, specifically the rods that allow us to see in low light.