Seeing is definitely believing when it comes to stem cell therapy. A blind man has recovered enough sight to ride his horse. A woman who could see no letters at all on a standard eye test chart can now read the letters on the top four lines. Others have recovered the ability to see colour. All have had injections of specialised retinal cells in their eyes to replace ones lost through age or disease.

A trial in 18 people with degenerative eye conditions is being hailed as the most promising yet for a treatment based on human embryonic stem cells.

"We've been hearing about their potential for more than a decade, but the results have always been in mice and rats, and no one has shown they're safe or effective in humans long term," says Robert Lanza of Advanced Cell Technology in Marlborough, Massachusetts, the company that carried out the stem cell intervention. "Now, we've shown both that they're safe and that there's a real chance these cells can help people."

Ten years ago, the team at Advanced Cell Technology announced that it had successfully converted human embryonic stem cells into retinal pigment epithelial cells. These cells help keep the eyes' light-detecting rods and cones healthy. But when retinal pigment epithelial cells deteriorate, blindness can occur. This happens in age-related macular degeneration and Stargardt's macular dystrophy.

In a bid to reverse this, Lanza's team injected retinal cells into one of each of the 18participants' eyes, half of whom had age-related macular degeneration and half had Stargardt's. A year later, 10people's eyes had improved, and the eyes of the others had stabilised. Untreated eyes had continued to deteriorate.

"On average, we're seeing three lines [on an eye test chart] of visual improvement in our patients," says Lanza.

There were no serious side effects and no sign of tumours, which can be a potential risk in stem cell therapies.

Lanza says the aim of the study was to halt further deterioration, so the improvements in sight were an unexpected bonus. He speculates that the improvements might be the result of rods and cones that had become dormant when the native retinal pigment epithelial cells died, resuming their function when the fresh cells were added.

"The results are highly encouraging," says Pete Coffey of University College London, who heads a project to treat people with age-related macular degeneration using tiny patches of retinal pigment epithelial cells made from human embryonic stem cells.

Advanced Cell Technology is now planning a larger trial, first in 100 people with Stargardt's, then in people with macular degeneration.

Originally posted here:

Stem cells improve vision enough for horse riding