BioEd Online

An injection of stem cells saved the sight of mice who would otherwise have gone blind, researchers reported this week. The study raises the prospect that some forms of human blindness might be treated with cells from a patient's own bone marrow.

The research team focused on a group of eye diseases called retinitis pigmentosa, in which cells in the retina break down over time, causing gradual loss of vision and sometimes blindness. There is currently no good treatment for the condition, which affects around one in 3,500 people.

Martin Friedlander at the Scripps Research Institute in La Jolla, California, and his team extracted a pool of stem cells from the bone marrow of adult mice and injected them into the eyes of newborn mice with a version of retinitis pigmentosa, before their retinas had begun to break down. The injections appeared to halt some of the eye's deterioration, the team found, particularly that of the cones, which are responsible for colour and fine vision.

The treated mice were also able to detect light shone into their eyes, whereas a group that did not receive treatment went completely blind. "It's amazing," says Friedlander, who reports the results in the Journal of Clinical Investigation¹.

Looking good

Stem cells are able to give rise to a variety of other cell types, but it is not yet known how they help the eye in this case. The team has shown previously that stem cells can help stop blood vessels in the retina breaking down, perhaps by integrating into them. But others may lodge in the eye and manufacture some type of molecule that helps both blood vessels and cones survive.

Friedlander hopes that the sight of human patients with retinitis pigmentosa could be sustained with injections of their own stem cells, harvested from their bone marrow. In humans, the deterioration of the eye doesn't tend to start until adolescence or later. "We're running to the clinic with this," he says. He hopes to start work on patients as early as a year from now, if he can accumulate enough evidence that the technique is safe.

The technique is one of the most promising treatments for blindness to be discovered in recent years, agrees Lois Smith, who studies eye disease at Harvard University in Massachusetts. Retinitis pigmentosa has many different underlying causes, so it is tough to find a drug that works for all cases.

Stem cells might also be adapted to treat other, more widespread forms of blindess, the researchers speculate. Blindness is most commonly caused by diabetic retinopathy and age-related macular degeneration. These are both conditions in which blood vessels in the eye grow abnormally. Stem cells might be engineered to crank out molecules that correct the vessels' growth, Smith says.