The
chemical, called AAQ (see below structure, acrylamide- azobenzene - quaternary ammonium), acts by taking the remaining, normally "blind" cells in
the retina sensitive to light, said lead researcher Richard Kramer, UC Berkeley
professor of molecular and cell biology. 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.
The
blind mice in the experiment had genetic mutations that made their rods and
cones die within months of birth and inactivated other photopigments in the eye. After injecting very small amounts
of AAQ into the eyes of the blind mice, Kramer and his colleagues confirmed that
they had restored light sensitivity because the mice's pupils contracted in
bright light, and the mice showed light avoidance, a typical rodent behavior
impossible without the animals being able to see some light. Kramer is hoping to
conduct more sophisticated vision tests in rodents injected with the next
generation of the compound.
Because
the chemical eventually wears off, it may offer a safer alternative to other
experimental approaches for restoring sight, such as gene or stem cell
therapies, which permanently change the retina. It is also less invasive than
implanting light-sensitive electronic chips in the eye.
"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. 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," Kramer said...........
