New research shows adult stem cells may aid in treating retinal degeneration

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.