For the millions of Americans whose vision is slowly ebbing due to degenerative diseases of the eye, the lowly neural progenitor cell may be riding to the rescue.
In a study in rats, neural progenitor cells derived from human fetal stem cells have been shown to protect the vision of animals with degenerative eye disease similar to the kinds of diseases that afflict humans. The new study appears in the journal Public Library of Science (PLoS) One.
The lead author of the study, University of Wisconsin-Madison researcher David Gamm, says the cells - formative brain cells that arise in early development - show "some of the best rescue, functionally and anatomically" of any such work to date. In animals whose vision would typically be lost to degenerative retinal disease, the cells were shown to protect vision and the cells in the eye that underpin sight.
The new findings are important because they suggest there may be novel ways to preserve vision in the context of degenerative diseases for which there are now no effective treatments. Macular degeneration, an age-related affliction that gradually destroys central vision, is a scourge of old age, robbing people of the ability to read, recognize faces and live independently.
The finding that the brain cells protected the cells in the eye was a surprise, according to Raymond D. Lund, an author of the new study and an eye disease expert at the University of Utah and the Oregon Health and Sciences University. The neural progenitor cells, which arise from stem cells and further differentiate into different types of cells found in the central nervous system, were being tested for their ability to deliver another agent, a growth factor that has been shown to be effective in treating some types of degenerative disease.
What was surprising, say Gamm and Lund, was that the cells alone demonstrated a remarkable ability to rescue vision.
"On their own, they were able to support retinal cells and keep them alive," says Lund, who has conducted pioneering studies of cell therapy for eye disease. "We didn't expect that at all. We've used a number of different cell types from different sources and these have given us the best results we've ever got."
How the cells act to preserve the deteriorating eye cells remains unknown, says Gamm. Like all cells, neural progenitor cells do many things and secrete many different types of chemicals that may influence the cells around them.
"The idea was to test the cells as a continuous delivery system" to shuttle an agent known as glial cell line-derived neurotrophic factor or GDNF, Lund explains. "It's not a sensible thing to inject the eyes many times over years. The idea was to use the cells as a continuous delivery system, but we found they work quite well on their own."