Stargardt Disease at Center of Embryonic Stem Cell Trial
Great excitement surrounds the announcement that human embryonic stem cells will be used in a trial to treat patients with Stargardt macular dystrophy. If successful, the new trial, in which experts will use retinal pigment epithelium cells derived from the human embryonic stem cells, could lead to an effective treatment for Stargardt disease as well as other degenerative eye diseases such as dry age-related macular degeneration, a condition that typically affects people age 65 and older.
What is Stargardt disease?
Stargardt macular dystrophy (Stargardt disease) is—for now—an incurable inherited eye condition that is a form of macular degeneration and a leading cause of blindness among young people. The disease occurs in about one in 10,000 children.
Like age-related macular degeneration, Stargardt disease is characterized by progressive loss of central vision. In Stargardt disease, however, the damage begins in both eyes usually between the ages of 6 and 20. Early signs of Stargardt include difficulty reading, black or hazy spots in the center of vision, and taking a longer time to adjust between light and dark environments.
Young people usually experience a slow loss of central vision until they reach the 20/40 level, and then vision loss progresses rapidly to the legally blind level (20/200). Some people experience a more rapid decline to 10/200 in just a few months. Most people retain peripheral and night vision, but lose color vision in later stages of the disease.
Scientists uncovered a genetic component of Stargardt disease in 1997 and named the ABCA4 gene as the probable culprit. When there is a defect in the ABCA4 gene, it produces a malfunctioning protein, which in turn inhibits energy flow to and from the photoreceptor cells in the retina.
The lack of energy causes the photoreceptor cells to degenerate, and waste materials build up in the retinal pigment epithelium. This accumulation causes damage to the rods and cones in the eye, ultimately resulting in loss of central vision.
So far, one young female in the United States who had already been blinded by Stargardt disease has been treated using retinal pigment epithelium cells derived from stem cells. That trial began in mid-July 2011. The new trial, to be conducted at Moorfields Eye Hospital in London, will be the first one outside the United States and will include more patients.
Professor Peng Khaw, director of the biomedical research center at Moorfields, explained that “we are delighted to be the site for these very exciting new clinical trials in stem cell therapy, which have the potential to give hope and make such a difference to the lives of people with currently untreatable blinding retinal conditions.”