Retinal stem cell research has yielded ‘spectacular progress,’ but challenges lie ahead

FORT LAUDERDALE, Fla. — The field of retinal stem cell research has seen great advances in the past decade, but work still lies ahead, according to researchers speaking here.

“There has been spectacular progress in this field, but there are still great challenges,” said Ruben R. Adler, MD, here at the Association for Research in Vision and Ophthalmology meeting

He discussed his current efforts in stem cell research, in which he seeks to replace degenerated photoreceptor cells with healthy cells.

“When photoreceptors die, they don’t come back,” Dr. Adler explained. “We are trying to replace these dead cells with healthy stem cells to prevent blindness.”

One problem with culturing stem cells, he said, is that, at present, there is “no magic bullet” to turn progenitor cells into mature synaptically connected photoreceptors.

“What we need is a growth factor that would speed up the transformation,” Dr. Adler noted.

In a separate presentation, Derek van der Kooy, MD, explained that stem cells used in retinal research are often taken from the ciliary marginal zone of the retina. He said the advantage of stem cells is their “multipotentiality” and “self-renewal,” which makes them ideal tools for ocular tissue regeneration.

“In culture, one human stem cell can proliferate to 10,000 stem cells in just a week,” he said. At the University of Toronto, Dr. van der Kooy has been cloning human retinal stem cells and studying their response to implantation in living animals.

“We are trying to put human receptor stem cells in mouse eyes to see if the cells integrate well,” he said.

Cell integration and biocompatibility is crucial to success whether dealing with stem cells or with implanted artificial tissue, said Raymond Lezzi, MD, during his presentation. Speaking about retinal prostheses, he said improving the “interface” of foreign material implanted in diseased or degenerative tissue may be achieved through therapeutic adjuncts.

“Drug delivery may be helpful in fighting off rejection of retinal prostheses and will improve the biocompatibility of the prosthesis,” Dr. Lezzi said.

Shigeru Kinoshita, MD, PhD, another presenter at the session, who has developed corneal epithelial stem cell sheets for use in patients with corneal degeneration, agreed that tissue integration is vital. He said the rejection rate declines significantly when patients implanted with his corneal graft material are managed with immunosuppressant therapy.