Blind mice can see again, thanks to a recently discovered chemical that can reactivate light-sensing cells in their eyes. The find could lead to compounds that would help restore vision to people with common acquired forms of blindness like age-related macular degeneration.
Researchers from the University of Munich, the University of Washington and the University of California, Berkeley described in the journal Neuron on Wednesday how their chemical, known as AAQ, makes normally defective retina cells sensitive to light.
The chemical works by binding to cell structures called protein ion channels, which are like pores in a cell membrane that are involved in the flow of electrochemical signals. AAQ binds to ion channels in retina cells and alters the flow of ions in response to light, mimicking how normal rods and cone cells react to light and activate neurons.
"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," Berkeley researcher and senior author Richard H. Kramer said. "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."
The mice in the study had genetic defects that killed off their rod and cone cells shortly after birth. When the researchers injected a bit of AAQ into their eyes, the mice's pupils would contract in response to a bright light, and they also began avoiding light the way that normal rodents typically do.
AAQ's effect is temporary, but this may actually be an advantage, the authors say. Unlike gene or stem cell therapies that cause lasting changes in the retina, AAQ could be a more flexible experimental approach for patients.
"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," Kramer says.