An approach to therapy for degenerative blindness that involves reprogramming existing cells rather than introducing new ones:
Doctors may one day treat some forms of blindness by altering the genetic program of the light-sensing cells of the eye. [Working] in mice with retinitis pigmentosa, a disease that causes gradual blindness, the researchers reprogrammed the cells in the eye that enable night vision. The change made the cells more similar to other cells that provide sight during daylight hours and prevented degeneration of the retina, the light-sensing structure in the back of the eye.
"We think it may be significantly easier to preserve vision by modifying existing cells in the eye than it would be to introduce new stem cells. A diseased retina is not a hospitable environment for transplanting stem cells. [The] question was, when retinitis pigmentosa is caused by a mutation in a protein only active in rods, can we reduce or stop vision loss by making the cells less rod-like?"
The new study focuses on a protein known as Nrl, which influences development of photoreceptors. Cells that make Nrl become rods, while cells that lack the protein become cones. Turning off the Nrl gene in developing mice leads to a retina packed with cone cells. To see if this rod-to-cone change was possible in adult mice, [researchers] created a mouse model of retinitis pigmentosa with an Nrl gene that could be switched on and off by scientists. [In] adult mice, switching off Nrl partially converts the rod cells into cone cells.