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Stem cell treatment for devastating eye disease moves closer to clinical trials

Stephen H. Tsang, M.D., Ph.D., associate professor of pathology and cell biology and of ophthalmology at Columbia University Medical Center and an ophthalmologist at New York-Presbyterian Hospital/CUMC, led the study. “We’ve never seen this type of improvement in retinal function in mouse models of RP. We hope we may finally have something to offer patients with this form of vision loss,” he said.

RP encompasses a group of inherited eye diseases that cause progressive loss of photoreceptor cells, specialized neurons found in the retina. The first symptoms typically appear in early adulthood, beginning with night blindness. In later stages, RP destroys photoreceptors in the macula, which is responsible for fine central vision. Mutations in at least 50 genes have been found to cause the disease, which affects about 1.5 million people worldwide.

In their study, published in the current issue of Molecular Medicine, the CUMC researchers tested the long-term safety and efficacy of using iPS cell grafts, taken from human skin cells, to restore visual function in a mouse model of RP. The cells were administered via injection directly underneath the retina when the mice were five days old.

The iPS cells assimilated into the host retina without disruption, and none of the mice receiving transplants developed tumors over their lifetimes, the researchers reported. The iPS cells were found to express markers specific to retinal pigmented epithelium (the cell layer adjacent to the photoreceptor layer), showing that they had the potential to develop into functional retinal cells. Using electroretinography, a standard method for measuring retinal function, the researchers found that the visual function of the mice improved after treatment and the effect was long lasting.

“This is the first evidence of lifelong neuronal recovery in an animal model using stem cell transplants, with vision improvement persisting throughout the lifespan,” said Dr. Tsang.

In 2011, the FDA approved clinical trials of embryonic stem cell transplants for the treatment of macular degenerations, but such therapy requires immunosuppression.

“Our study focused on patient-specific iPS cells, which offer a compelling alternative,” said Dr. Tsang. “The iPS cells can provide a potentially unlimited supply of cells for functional rescue and optimization. Also, since they would come from the patient’s own body, immunosuppression would not be necessary to prevent rejection after transplantation.”

In theory, iPS cell transplants could also be used to treat age-related macular degeneration, the leading cause of vision loss among older adults, Dr. Tsang added. His team also conducted an RP study using gene therapy that also appeared to show promise. Those results are published in Human Molecular Genetics.

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