Blind Mice Regain Sight, May Help Cure Macular Degeneration

Scientists at the University of California-Berkley reported that a recent gene therapy application has cured mice of blindness caused by retinal degeneration. Although these are preliminary findings, researchers are already predicting a potential availability to the public within three years. This means that those suffering from age-related macular degeneration (AMD) just may have a chance at reversing potential blindness. It also means that those who have already succumbed to losing their sight could possibly have it restored.

According to the Berkeley News, 

“About 170 million people worldwide live with age-related macular degeneration, which strikes one in 10 people over the age of 55, while 1.7 million people worldwide have the most common form of inherited blindness, retinitis pigmentosa, which typically leaves people blind by the age of 40.” 

Gene therapy could begin to lower this number significantly possibly making macular degeneration and blindness, a thing of the past.

Gene Therapy vs Stem Cell Therapy

Gene therapy focuses on the negative outcome of pre-programmed cells and then cleverly “re-programs” them to a more beneficial result. Gene therapy has been advancing beyond the expectation of many researchers at such a rapid pace it is astounding. Stem cell therapy has been leading the way with many benefiting from regeneration and repair of damaged tissue when applied. However, when it comes to macular degeneration, it is gene therapy that may surpass stem cell therapy with the possibility of eliminating it altogether.

Gene therapy focuses on transplanting normal genes into cells that have missing or defective ones. In many cases, this transplantation, or gene therapy, has been able to correct genetic disorders. When genetic disorders are corrected, stem cells are no longer needed. 

Non-Virus Transport

Scientists were able to “piggy-back” a specific gene (called a medium wavelength cone opsin -MW-ospin rd1) inside an inactive virus for effective transport into the eyes of mice. This specific gene is for a green light receptor which is essential for optimal sight. 

Berkeley News reported on the progress of the blind mice after the injections, 

“…a month later, they were navigating around obstacles as easily as mice with no vision problems. They were able to see motion, brightness changes over a thousandfold range and fine detail on an iPad sufficient to distinguish letters.”

The non-virus transport is a highly effective way to immediately place the new genes and “start-up” retinal cells that have not already been damaged. However, there are over 250 varying genetic mutations that can attack the retina with upwards of ninety percent that slowly destroy the rods, sensitive to dim light, and the cones, for daylight color perception. 

Fortunately, and still unknown as to why, but researchers claim that other layers of retinal cells, particularly what are called the bipolar and the retinal ganglion cells are spared. These ganglion cells remain healthy but unable to detect light even when someone goes completely blind. It is almost as if it is a full battery pack just waiting to power up. This is where the current gene therapy has found a workaround. 

Waking Up Waiting Cells

It is almost as if macular degeneration has left a “back door” able to be opened for a cure. This is what the UC Berkeley team was able to accomplish, succeeding in tapping into the healthy ganglion cells making approximately ninety percent able to detect light. 

Berkeley News explained the process, 

“To reverse blindness in these mice, the researchers designed a virus targeted to retinal ganglion cells and loaded it with the gene for a light-sensitive receptor, the green (medium-wavelength) cone opsin. Normally, this opsin is expressed only by cone photoreceptor cells and makes them sensitive to green-yellow light. When injected into the eye, the virus carried the gene into ganglion cells, which normally are insensitive to light, and made them light-sensitive and able to send signals to the brain that were interpreted as sight.” 

Current options for patients with macular degeneration and other neurodegenerative diseases of the retina such as retinitis pigmentosa, include: 

• An electronic eye implant hooked to a video camera that sits on a pair of glasses
• Anti-VEGF injections (reduces new blood vessel growth and edema)
• Stem cell injections that are still in the testing phase
• Dietary and supplemental attempts at slowing macular degeneration or other disease progression   

Waking up waiting cells is a veritable breakthrough which scientists feel could be applied to other diseases that may have hidden back doors as well. For macular degeneration however, knowing where these cells are and how to restore them brings science that much closer to a workaround cure. 

In Three Years

Predictions of hope can often make people get ahead of themselves and then be extremely let down when something goes awry. However, this new gene therapy may be the real deal. It is understood that the eyes of mice are much different from humans, yet researchers at UC Berkeley seem to be unswayed by the potential leap to humans stating that,

“In mice, the researchers were able to deliver the opsins to most of the ganglion cells in the retina. To treat humans, they would need to inject many more virus particles because the human eye contains thousands of times more ganglion cells than the mouse eye. But the UC Berkeley team has developed the means to enhance viral delivery and hopes to insert the new light sensor into a similarly high percentage of ganglion cells, an amount equivalent to the very high pixel numbers in a camera.”

This crossover to human eyes is predicted to happen within three years time. According to Ehud Isacoff, a UC Berkeley professor of molecular and cell biology and one of the authors of the study, 

“We actually think that within three years this could be in humans,…The only thing that needs to be done in order to achieve that at this point is to work out the details of the delivery mechanism of the gene.”

Oddly enough, this procedure is considered so simple it is estimated that it could probably have been attempted twenty years ago. This may be because, like so many simple great ideas of the past, researchers were told such an attempt would be fruitless. John Flannery, a UC Berkeley professor of molecular and cell biology who is on the School of Optometry faculty commented,

“When everyone says it will never work and that you’re crazy, usually that means you are onto something,” 

Expect gene therapy, like this application for macular degeneration as well as many other health compromises, to head the charge in helping people regain their sight as well as their lives. It is yet another broad leap science is making.