Age-related macular degeneration is the leading cause of vision loss in seniors, and existing treatments are few.
But now, experiments in pigs and rats suggest that stem cell therapy might help curb at least one form of the disease. The results could soon lead to the first human trials of this therapy for macular degeneration, according to researchers from the U.S. National Eye Institute (NEI).
The rats and pigs in this study had geographic atrophy, the advanced "dry" form of the illness. One eye specialist was cautiously optimistic about the new report.
"This could lead to improved visual function for people with age-related macular degeneration of the dry form, for which there is currently no cure," said Dr. Mark Fromer, an ophthalmologist at Lenox Hill Hospital in New York City.
However, despite the early promise from these animal studies, "human clinical trials are necessary to develop these new groundbreaking techniques," Fromer said.
The new research was led by Kapil Bharti, who directs the NEI's Unit on Ocular and Stem Cell Translational Research. His team used human blood cells and, in the lab, converted them into what are known as induced pluripotent stem cells (iPS cells). These are cells that can develop into any type of cell in the body.
In this case, iPS cells, or iPSC, were programmed to become retinal pigment epithelial (RPE) cells — the cell type that dies off in the early stage of AMD. RPE cells are essential to vision because they nurture photoreceptors, the light-sensing cells in the eye's retina.
According to the NEI researchers, just 10 weeks after special "patches" of human iPSC-derived RPE cells were implanted in the retinas of pigs and rats, they had integrated within the retina and were functioning properly.
One major concern with any type of stem cell therapy is the risk of cells multiplying uncontrollably and forming tumors. But a genetic analysis of the iPSC-derived RPE cells used in this study revealed no such gene mutations, Bharti's team said.
And because the patient's own cells are used as the source of the transplanted cells, this "minimizes the chance of [transplant] rejection," Bharti explained in an NEI news release.
Based on these promising results, planning for an early stage trial in humans to test the safety of the stem cell therapy is already underway. The trial would begin after approval from the U.S. Food and Drug Administration, the researchers said.
Dr. Matthew Gorski is an ophthalmologist at Northwell Health in Great Neck, N.Y. He agreed that "the successful results of this study are important steps towards finding a treatment for certain types of macular degeneration."
Still, experiments performed on animals don't always pan out in humans, so "many more years of experiments will need to be completed before we can know if this technology can successfully be used to treat macular degeneration," Gorski said.
The study was published Jan. 16 in the journal Science Translational Medicine.