Cell replacement may cure blindness

Scientists claim they have moved a step closer to finding a cure for blindness after successfully replacing lost light-sensitive cells in back of the eye of mice that helped them see again.

A team at the University College London took healthy rods — tiny structures in the back of the eye essential for seeing in dim light — from young mice and injected them into the eyes of adult mice whose rods didn’t work. After four to six weeks, the new rods appeared to be working almost normally and had formed the connections needed to transmit information to the brain. When the treated mice were put in a dimly-lit pool, they headed straight for the exit, the Daily Mail reported.

The work is at an early stage but if successful, it will benefit millions of people who suffer from age-related macular degeneration, one of the most common forms of blindness, the researchers said.

Prof Robin Ali, who led the research, said: “We’ve shown for the first time that transplanted photoreceptor cells can integrate successfully with the existing retinal circuitry and truly improve vision.”

“We’re hopeful that we will soon be able to replicate this success with photoreceptors derived from embryonic stem cells and eventually to develop human trials.”

However, the scientists who detailed their work in the journal Nature, said much work is needed before the technique can be attempted on human patients. The first clinical trials might be five or 10 years away.

In the study, the undeveloped precursor cells were taken from week-old mice. Up to 32,000 of the cells were integrated into the retinas of recipient animals. Tests showed that visual responses in the brains of the mice were enhanced after the procedure.
To see how the transplants affected behaviour, mice were placed in a dimly lit Y-shaped water maze in which one of two routes led to escape. This required swimming towards a visual cue, a grating pattern.

After treatment, four of nine night-blind mice completed the task in 70 per cent of trials. Untreated mice and those given “sham” treatments, performed no better than by chance.
Cell integration in animals that performed best tended to be clustered rather than spread widely across the retina. This suggested that besides the number of cells, the closeness of the cells to one another might be important, the researchers said.

Professor Phil Luthert, director of the UCL Institute of Ophthalmology, said: “The techniques used in the study are part of a pretty big push in regenerative medicine.