Chemical enables vision in blind mice

A team of researchers at university of California, Berkeley have collaborated with scientists at university of Washington, Seattle and university of Munich to discover a chemical that is capable of temporarily restoring the vision in blind mice. The team is working on developing an improved version of the chemical that may enable people suffering from degenerative blindness to see once again. This approach could be especially beneficial to those having retinitis pigmentosa. This is a genetic disease characterized by inheritance of blindness. It is also the cause of macular degeneration which is a common cause of blindness. In both the cases the retina’s light sensitive cells i.e., the rods and cones die depriving the eyes of functional photoreceptors.

The chemical is called AAQ and works increasing the sensitivity of the leftover blind cells to the light as told by Richard Kramer, lead researcher and UC Berkeley professor (molecular and cell biology). AAQ stands for acrylamide-azobenzene-quaternary ammonium and is a photoswitch that reacts to the potassium channels. The chemical binds with the protein ion channels present on the retinal cells’ surface. When light falls on it, it gets switched on and changes the flow of ions in the channels. As a result the neurons get activated in a way similar to the rods and cones. Kramer said that the way AAQ works is similar to the effect of local anesthetics which also bind with the ion channels and keep us numb for a long time. But AAQ is different because of its light sensitive nature that allows it to be turned on or off. Since the effect of the chemical is temporary, it actually is a potential safe alternative to other approaches such as stem cell or gene therapies which require permanently changing the retina. It is also safer when compared to the light – sensitive electronic chips that have to be implanted in the eye. The advantage here is that because it’s a simple chemical which means that the dosage can be varied or combined with other treatments or stopped.  These advantages aren’t available in surgical methods. Dr. Russell Van Gelder, co –author and ophthalmologist said “This is a major advance in the field of vision restoration,” The findings of Kramer, Van Gelder and their colleagues will be published in Journal Neuron on July 26. The blind mice used had some genetic mutations that cause the death of their rods and cones soon after their birth. The evidence of the success of AAQ came from the observation that pupils of mice’s eyes contracted when exposed to light after being injected by AAQ. The mice showed typical rodent behavior i.e., avoiding light. Researchers hope to conduct some advance tests using improved version of the chemical.

Current methodologies for restoring vision include rods and cones regeneration through injection of stem cells, gene therapies or optogenetics involving insertion of a photoreceptor gene in the blind cells and using electronic prosthetic devices for stimulating blind neurons.