Stem Cell Therapy May Treat World's Leading Cause of Blindness

Author:  Hoi See Tsao

Institution:  Wellesley College
Date:  June 2007

A team of scientists from the UK recently used stem cell therapy to treat the world's leading cause of blindness, age-related macular degeneration. According to a BBC news report, the stem cell therapy has already been successful in "a handful of patients" using the patients' own eye cells.

Age-related macular degeneration is caused by the failure of a layer of cells under the retina-called retinal pigment epithelial cells-to process light. In turn, this leads to the degeneration of the central area of the retina, or the macula, and the decline of central vision, which is responsible for the ability to see fine details, to read, and to recognize faces.

Macular degeneration can take two distinct forms. The dry form involves atrophy of the retinal pigment epithelial layer. The resulting loss of function of the rod and cone photoreceptors in the central part of the eye eventually leads to blindness. The wet form of the condition involves the abnormal growth of blood vessels, resulting in the leakage of blood and protein below the macula layer, which causes irreversible photoreceptor damage. Ninety percent of age-related macular degeneration cases are the dry condition and 10% of cases are the wet condition.

Consultant ophthalmic surgeon at Moorfields Eye Hospital in London Lyndon Da Cruz performed the stem cell therapy on a few patients. The operation involved transplanting normal cells from the edges of the eye of patients with wet age-related macular degeneration onto the affected area of the eye. While the operations have been successful, there have been complications. The procedure also takes more than two hours and requires two operations.

To make the procedure quicker, easier and more accessible to patients, the researchers have grown retinal pigment epithelial cells from embryonic cells. The team hopes that the retinal pigment epithelial cells can then be processed into a layer and injected into the patient's eye, reducing operation time to 45 minutes. The researchers expect to be able to treat patients using this new method within five years. So far, tests on rats with age-related macular degeneration using the laboratory-grown retina pigment epithelial cells have been successful in restoring vision.

An anonymous £4m donation has helped the scientists to set up the London Project to Cure Age-Related Macular Degeneration with the University College London Institute of Ophthalmology.

Professor Pete Coffey, director of the project, explained to BBC News that although his team was able to successfully grow retinal pigment epithelial cells in the laboratory, they needed to ensure that the cells were safe in humans and this process required time.

"Using stem cells - which are far more adaptable - can only improve success of what has already been achieved and in addition establish this as a global therapy," Coffey said. "The goal is within five years to have a cohort of patients to put the cells into."

Cruz felt that if in the next decade, the 4 by 6 mm retinal pigment epithelial cells transplant was not popular and used globally, there must have been a major failure in the research. "We have the RPE [retinal pigment epithelial cells], we have the evidence that doing this type of thing can restore vision. It's practicality issues rather than a big unknown," he said.

Currently, operations using the patients' own cells are planned for patients with dry age-related macular degeneration to test the effectiveness of the procedure.

Written by Hoi See Tsao