Stem cell research: Retinal cells could be first to clinic

Retinal stem cells could well be the first neural stem cells used in patients, University of Toronto researcher Derek van der Kooy predicted recently at the National Stem Cell Centre conference in Melbourne.

"They are easy to get to and easy to grow," the scientist told a workshop on the use of stem cells for the treatment of neural disorders.

According to van der Kooy, one retinal stem cell can easily be expanded to 15,000 cells in a week, and there are 10,000 stem cells in a single human eye. The cells differentiate into the different types of retinal cells, including photoreceptors, and experiments in mice suggest that the differentiated cells integrate into the eye.

He believes the approach could be used in degenerative diseases such as retinitis pigmentosa, where the photoreceptors are destroyed. The cells are easily obtained up to 24 hours post mortem, or a patient's own cells could potentially be used.

But before the cells can be turned into a therapy it has to be shown that the stem cell-derived cells not only integrate into the retina, but form the right connections with the nerves of the optical system, van der Kooy said.

Ultimately, he would like to determine a combination of growth factors that activate retinal stem cells to repair the damaged areas of the retina. But this is likely to be difficult, particularly as mammalian retinal stem cells are under extremely tight control.

"There appears to be an inhibitory factor of some kind that stops proliferation, even when there is injury," van der Kooy says. "Mammals don't make new photoreceptors."