Transplanted retinal cells let blind mice see again

A team of British scientists using cellular implants has restored sight in adult mice -- possibly paving the way for similar techniques in the treatment of some forms of human blindness.

Robert MacLaren, Rachael Pearson and their colleagues from the Institute of Ophthalmology, University College London, plucked retinal cells from newborn mice and transplanted them into adult mice with impaired vision. With the new retinal cells, the animals were able to see lights.

Other researchers have tried to transplant stem cells, but the new connections were not sufficient to restore vision.

The study focused on photoreceptors, the light-sensitive cells in the retina. They are the only cells damaged in age-related macular degeneration and retinitis pigmentosa -- two conditions that can cause blindness.

One in 10 people older than 65 is at risk for age-related macular degeneration, and 1 in 3,000 has retinitis pigmentosa. In these conditions, these cells are lost, but all other neuronal connections to the brain are intact.

In the current study, the scientists looked at these photoreceptors’ development from embryo to newborn. They found that the cells that worked best came from animals between the first and fifth days of life.

“Photoreceptors are just being born and starting to make connections,” said Pearson, one of the coauthors of the study published Thursday in the journal Nature.

The retinal cells were transplanted in normal adult mice and others with two types of problems that cause blindness.

Ten mice that received the transplants were studied. When a light was shone in the retina, electrical signals came out of the cells, suggesting that the animals were responding to light that they otherwise would not have seen. Scientists also observed the pupils constricting, another sign that the mice were registering the light in their eyes and the message was traveling to the brain.

“We restored some aspects of visual function,” Pearson said. “But we have no idea yet what the animals can or can’t see. It’s still a long way off from a human treatment.”