Stem Cells and Macular Degeneration
Stem cells and Macular Degeneration have been in the news quite a bit lately. Most recently, a reported human stem cell clinical trial may lead to a new treatment for non-neovascular age-related macular degeneration (NNAMD). According to the National Eye Institute, age-related macular degeneration is a common eye condition in people over 50. The condition causes progressive damage to the macula, a structure near the center of the retina. This damage causes a progressive loss of focus and vision. To measure the damage, physicians ask patients to identify letters and numbers.
While the condition typically does not cause total blindness, it does cause a loss of central vision. People who suffer severe retinal damage may not be able to see faces, read or write, or perform detail-oriented tasks. Currently, there is no cure for the condition.
Age, smoking, race, family history, high blood pressure and genetics are all significant contributing factors to the disease. The use of high-dose vitamin combinations can slow the progression of intermediate and late-stage disease in one eye. No effective early treatments exist, and current treatments do not restore lost vision.
Stem cells show promise for treating dry macular degeneration
A group of researchers at the University of Southern California has developed a retinal implant made from a single layer of human stem cells to replace lost retinal pigment epithelium cells. They tested the implant in four of five patients with advanced age-related macular degeneration. The experimental implant proved both safe and well-tolerated by the test subjects, and none of the test subjects experienced progressive vision loss. Furthermore, initial results also showed some improvement in visual acuity. Following implantation, one eye was able to discern 17 more letters than before implantation. Two subjects reported improved central focusing ability. This leads researchers to believe that the technique could delay the progression of the disease. It also shows the potential to restore lost vision.1
The experimental implant is designed to mimic Bruch’s membrane, a specialized base layer of the choroid. The choroid is a vascular layer of tissue that provides oxygen and nutrients to the retina. Bruch’s membrane naturally varies in thickness but thickens naturally as a consequence of aging. This thickening slows down the delivery of nutrients to the retina. It also allows the formation of phospholipid deposits that characterize the disease. Damage to Bruch’s membrane can also cause neo-vascular (wet) macular degeneration, a condition that features rapid vision loss. The current clinical trial examines the impact of stem cell implantation only on age-related (dry) macular degeneration.
Stem cell treatments may treat wet macular degeneration
A separate research team at the University of California Santa Barbara (UCSB) has already explored the use of human stem cells to treat neo-vascular (“wet”) macular degeneration. This condition produces retinal damage from leaking fluid and blood in and around the macula. Wet macular degeneration almost always results from “dry” macular degeneration. However, not everyone who experiences dry macular degeneration progresses to the wet form of the condition.
The UCSB team, in partnership with Moorfields Eye Hospital NHS Foundation Trust, the University College London Institute of Ophthalmology and the National Institute for Health Research, developed a stem cell retinal patch. They implanted the test patch into two patients at a London hospital. The patients reported significant improvements in their vision. Both test subjects regained the ability to read with ordinary reading glasses– an ability they’d completely lost prior to treatment. NHS researchers hope that the research trial may lead to an “off-the-shelf” treatment for macular degeneration within five years.
The use of human stem cells to treat vision loss has shown promising results in small clinical trials. Before such treatments can become widely available, researchers must also conduct larger-scale trials on a more diverse study population. Macular degeneration causes about half of all visual impairments today, and promising treatments that can stop or reverse the progression of the disease can have a major impact on healthcare worldwide.
- A bioengineered retinal pigment epithelial monolayer for advanced, dry age-related macular degeneration: BY