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.
鈥淲e鈥檝e 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鈥檙e safe or effective in humans long term,鈥� says Robert Lanza of in Marlborough, Massachusetts, the company that carried out the stem cell intervention. 鈥淣ow, we鈥檝e shown both that they鈥檙e safe and that there鈥檚 a real chance these cells can help people.鈥�
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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鈥� 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鈥檚 macular dystrophy.
Decline halted
In a bid to reverse this, Lanza鈥檚 team injected retinal cells into one of each of the 18聽participants鈥� eyes, half of whom had age-related macular degeneration and half had Stargardt鈥檚. A year later, 10聽people鈥檚 eyes had improved, and the eyes of the others had stabilised. Untreated eyes had continued to deteriorate.
鈥淥n average, we鈥檙e seeing three lines [on an eye test chart] of visual improvement in our patients,鈥� says Lanza.
There were no serious side effects 鈥� 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.
鈥淭he results are highly encouraging,鈥� 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鈥檚, then in people with macular degeneration.
Trials of cells made from human embryonic stem cells are also poised to begin in people with type 1 diabetes and heart failure, the first time embryonic stem cells have been used in the treatment of major lethal diseases. They have also been injected into the spines of four people with paralysis, although that trial is now on hold because the company running it, Geron, went bust.
Journal reference: The Lancet, DOI:
