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From Ophthalmology Times - February 15, 2001 Issue
Transplanted Stem Cells May Aid AMD Patients
by Laura Newman
Reviewed by Michael J. Young, PhD
(Figure courtesy of Michael J. Young, PhD)
Investigators hope that animal research - such
as with these adult rat hippocampal progenitor
cells - will pave the way to using adult stem cell
transplants to treat retinal degeneration
in humans.
New York - Recent animal research
demonstrating that stem cells could be isolated from the hippocampus has pushed
research on retinal degeneration into a new direction. Now for the first
time, bench researchers have successfully transplanted stem cells from the
hippocampus into the eyes of mature rats with retinal degeneration, where they
have migrated to the retina.
Although researchers have not yet demonstrated that the
transplanted hippocampal cells can develop into functional photoreceptors that
improve eyesight, investigators hope that further research will pave the way to
using stem cell transplants to treat retinal degeneration in humans, said
Michael J. Young, PhD.
"When I first discussed the possibility of putting
hippocampal cells into eyes [to regenerate the retina] at the Association for
Research in Vision and Ophthalmology last year, people came up to me and were
skeptical, saying it sounded almost like a silly thing to do," said Dr.
Young, assistant scientist at the Schepens Eye Institute at Harvard University
in Boston.
But research is proceeding. In the September issue of
Molecular and Cellular Neuroscience, Dr. Young and colleagues Henry J. Klassen,
MD, PhD, of Children's Hospital of Orange County, Orange, CA and Fred H. Gage,
PhD of the Salk Institute, LaJolla, CA reported that they have been able to
"inject hippocampal cells into the eyes of rats with retinal degeneration,
where they take up residence, migrate to the retina and have begun to take on
the characteristics of retinal cells."
In the study, researchers inject adult rat hippocampal
progenitor cells (AHPC) into the eyes of rats with diseased retinas. The
cells survived up to 16 weeks, showing broad incorporation of green fluorescent
protein-expressing (GFP+) donor cells for 10 weeks, though only limited
incorporation into rats as old as 19 weeks. Stem cells in the ganglion
cell layer also extended neurites into the optic nerve. When grafted to 36
week old rats, however, the progenitor did not survive. Dr. Young was
careful to stress that this research is very early, pointing out that much more
research has to be done with animals to prove that the stem cell transplants can
improve vision.
"We still must demonstrate that these progenitor cells
differentiate into functional photoreceptors, even though morphologically they
can look like these key cells," Dr. Young said. "A lot more
needs to be done. We need to prove that they are safe."
In culture, Dr. Gage's laboratory has shown that the cells can
be induced to proliferate. Also, when transplanted, they can migrate over
large distances. "We need to understand the factors that
control these behaviors," he said.
In the eye, potential applications that may develop include
novel treatments for age-related macular degeneration and retinitis pigmentosa,
according to Dr. Young. Even further down the road this approach could
prove a new way to treat retinal detachments and diabetic retinopathy, he said.
The stem cell transplantation technique is also under active
study for Parkinson's Disease, Huntington's Disease and spinal cord injury.
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