Scientists have come closer to discovering a chemical which reinstates light sensitivity for the blind, the University of California, Berkeley has revealed.
In a post on its news center, the educational institution has said that a team of scientists consisting of researchers from the organization as well as from the University of Munich and University of Washington, in Seattle has discovered a certain chemical which briefly restores light sensitivity in blind mice.
According to UC Berkeley Professor Richard Kramer, the new chemical is called AAQ (acrylamide-azobenzene-quaternary ammonium). This chemical makes normally light-insensitive cells in the retina become light-sensitive.
In the experiment, blind mice were injected with very small amounts of AAQ which restored light sensitivity in these blind mice. The team knows this as the pupils of the mice’s eyes reacted by contracting in bright light.
Furthermore, the mice – after being injected with AAQ – exhibited the typical mice behavior of avoiding light which would have been impossible if the mice’s eyes were still insensitive to light.
These mice “had genetic mutations that made their rods and cones die within months of birth and inactivated other photopigments in the eye,” UC Berkeley said.
Quoting the release, UC Berkeley says that: “AAQ is a photoswitch that binds to protein ion channels on the surface of retinal cells. When switched on by light, AAQ alters the flow of ions through the channels and activates these neurons much the way rods and cones are activated by light.”
“This is similar to the way local anesthetics work: they embed themselves in ion channels and stick around for a long time, so that you stay numb for a long time,” Professor Kramer explained.
“Our molecule is different in that it’s light sensitive, so you can turn it on and off and turn on or off neural activity,” he added.
Furthermore, the release mentions that the same team is now working on improving this chemical and hopes to find a compound that “may someday allow people with degenerative blindness to see again.”
The team envisions that the compound will be the answer to the genetic disease retinitis pigmentosa and the age-related macular degeneration. As it stands, retinitis pigmentosa is the most common form of blindness passed on genetically. Macular degeneration, on the other hand, is the world’s leading cause of acquired blindness.
For both ailments, light-sensitive cells in the retina die causing the eye to have no functioning cells that detect light.
“This is a major advance in the field of vision restoration,” said Dr. Russel Van Gelder who is chair of the Department of Ophthalmology at the University of Washington, Seattle.
Van Gelder is a co-author of the paper which will detail the results of the group’s study in the July 26 edition of the journal Neuron.
Kramer is joined by chemist Dirk Trauner and UC Berkeley current or former post-docs or graduate students Aleksandra Polosukhina, Jeffrey Litt, Ivan Tochitsky, Ivan De Kouchkovsky, Tracy Huang and Katharine Borges; and post-doctoral fellow Joseph Nemargut and ophthalmology resident Yivgeny Sychev at the University of Washington
“The photoswitch approach offers real hope to patients with retinal degeneration,” Van Gelder said.
“We still need to show that these compounds are safe and will work in people the way they work in mice, but these results demonstrate that this class of compound restores light sensitivity to retinas blind from genetic disease,” he explained further.
According to UC Berkeley, this photoswitch approach is a safer alternative to current alternative experimental treatments for curing blindness. Other approaches currently being developed involves gene or stem cell therapies which result in the permanent alteration of the retina.
Other experimental treatments include chip implants in the eye which is more invasive than this new approach.
“The advantage of this approach is that it is a simple chemical, which means that you can change the dosage, you can use it in combination with other therapies, or you can discontinue the therapy if you don’t like the results,” Professor Kramer said.
“As improved chemicals become available, you could offer them to patients. You can’t do that when you surgically implant a chip or after you genetically modify somebody,” he explained.
The professor says that the team is “really excited about” new versions of AAQ qhich are currently being tested. These newer versions of AAQ activate neurons for days compared to hours for the earlier versions. Furthermore, the newer versions of AAQ self-deactivate in darkness which means the blind will not have to have certain lights to deactivate the chemical if they so deemed.