MADISON - 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 today (March 28) in the journal Public Library of Science (PLoS)
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
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."
Lund has experimented with other cell types as therapies for preserving
vision. The neural progenitor cells, a cell model developed by Wisconsin stem
cell researcher Clive Svendsen, have been used experimentally to deliver the
same growth factor in models of Parkinson's disease and Lou Gehrig's disease.
Svendsen is also an author of the new PloS One report.
"It seems that the cells in and of themselves are quite neuroprotective,"
says Gamm. "They don't become retinal cells. They maintain their own identity,
but they migrate within the outer and inner retina" where they seem to confer
some protection to the light-sensing cells that typically die in the course of
degenerative eye disease.
For researchers, the work is intriguing because the progenitor cells come
from the brain itself, and not from the part of the nervous system devoted to
"This cell type isn't derived from the retina. It is derived from the brain,"
says Gamm. "But we're not asking it to become a retina. They survive in the
environment of the eye and don't disrupt the local architecture. They seem to
live in a symbiotic relation ship" with retinal cells.
Gamm and Lund emphasize that the new work is preliminary, and that much
remains to be done before the cells can be tested in humans: "The first thing is
to show that something works, which we have done," says Lund. "Now we need to
find out why, but this is a good jumping off point. "