Researchers at Mount Sinai have successfully restored vision in mice through activating retinal stem cells, something that has never been done before. Their study, published in the August 15 online issue of Nature, could transform treatment for patients with retinal degenerative diseases, which currently have no cure.
"This study opens a new pathway for potentially treating blinding diseases by manipulating our own regenerative capability to self-repair," explained lead investigator Bo Chen, PhD, Associate Professor of Ophthalmology and Director of the Ocular Stem Cell Program at the Icahn School of Medicine at Mount Sinai. "This is the first step to finding promising cures for patients that involve self-repair as opposed to medicine or invasive procedures."
In zebrafish, Müller glial cells (MGs) are a source of retinal stem cells that can replenish damaged retinal neurons and restore vision. In mammals, MGs do not have regenerative capability after photoreceptors are lost, and therefore retina damage cannot fix itself. As a result, in patients with diseases like macular degeneration or retinitis pigmentosa that kill retinal cells, the disease progression is often irreversible. Researchers hypothesized if they could somehow reactivate MGs and bring back vision.
A team of scientists did a two-step gene transfer to reprogram MGs into blind mice. First, they activated dormant stem cells to become active stem cells. The second step involved another gene transfer to help stem cells develop into rod photoreceptor cells. The rod photoreceptor cells are the most abundant cell type in the retina, and the first step to sensing light in the retina. They then transmit to other cells in the retina, which send signals to the brain allowing for actual sight.
After this two-step reprogramming, investigators found that new rod photoreceptors were generated and integrated into the existing retinal structure, instead of floating around and being ineffective. They saw no difference between these new cells and real rod photoreceptor cells. These cells sensed light, which then triggered information to be sent to the visual cortex (brain) and restored function of the visual pathway. Between four and six weeks after the reprogramming, the blind mice were able to sense light and regained their vision.
While vision was restored to some degree, researchers could not measure the degree of improvement, and must do further testing to find this out.
"This could lead to extraordinary opportunities in the future where we can potentially use the same strategy to reactivate these stem cells in the diseased human eye," said Dr. Chen. "If this works, this could transform the way we treat patients with retinal disease and possibly learn how to cure other types of eye disease like glaucoma."
The National Eye Institute (NEI), which is part of the National Institutes of Health, supported this study.
About the Mount Sinai Health System
The Mount Sinai Health System is New York City's largest integrated delivery system encompassing seven hospital campuses, a leading medical school, and a vast network of ambulatory practices throughout the greater New York region. Mount Sinai's vision is to produce the safest care, the highest quality, the highest satisfaction, the best access and the best value of any health system in the nation. The System includes approximately 7,100 primary and specialty care physicians; 10 joint-venture ambulatory surgery centers; more than 140 ambulatory practices throughout the five boroughs of New York City, Westchester, Long Island, and Florida; and 31 affiliated community health centers. The Icahn School of Medicine is one of three medical schools that have earned distinction by multiple indicators: ranked in the top 20 by U.S. News & World Report's "Best Medical Schools", aligned with a U.S. News & World Report's "Honor Roll" Hospital, No. 13 in the nation for National Institutes of Health funding, and among the top 10 most innovative research institutions as ranked by the journal Nature in its Nature Innovation Index. This reflects a special level of excellence in education, clinical practice, and research. The Mount Sinai Hospital is ranked No. 18 on U.S. News & World Report's "Honor Roll" of top U.S. hospitals; it is one of the nation's top 20 hospitals in Cardiology/Heart Surgery, Diabetes/Endocrinology, Gastroenterology/GI Surgery, Geriatrics, Nephrology, and Neurology/Neurosurgery, and in the top 50 in four other specialties in the 2017-2018 "Best Hospitals" issue. Mount Sinai's Kravis Children's Hospital also is ranked in six out of ten pediatric specialties by U.S. News & World Report. The New York Eye and Ear Infirmary of Mount Sinai is ranked 12th nationally for Ophthalmology and 50th for Ear, Nose, and Throat, while Mount Sinai Beth Israel, Mount Sinai St. Luke's and Mount Sinai West are ranked regionally. For more information, visit http://www.mountsinai.org/, or find Mount Sinai on Facebook, Twitter and YouTube.