When it comes to stem cells, it appears the eyes have it. Researchers at the University of Toronto and the Hospital for Sick Children (HSC) have identified retinal stem cells in the adult mammalian eye, opening the door for retinal regeneration as a possible cure for damaged or diseased eyes.

"Before our study, it wasn't known whether retinal regeneration was possible in adult mammals, especially humans," says Vincent Tropepe, a PhD student in U of T's developmental biology program and lead author of the study that appears in the March 17 edition of the journal Science. "We've shown that by removing these cells from the eye, we can encourage the production of new neurons even after the retinas have fully matured and cell division has stopped."

Stem cells give rise to a lineage of other cells by simultaneously dividing and self-renewing, beginning in the embryo and continuing throughout post-natal life and into adulthood. When this cell division occurs, one of the two new cells is identical to the original while the other is slightly different. These new cells continue to divide and can become specialized and replace others that die or are lost.

In their study, researchers discovered retinal stem cells in the tissue of adult mice, cows and humans. Previously, only amphibians and fish were thought to have retinal stem cells capable of regenerating and making new neurons. "The stem cells we discovered appear to be under inhibitory control while still in the eye, but proliferate once they are removed," says Roderick McInnes, holder of the Anne and Max Tannenbaum Chair in Molecular Medicine at HSC and U of T.

The research team now hopes to be able to stimulate the stem cells in their natural region inside the eye in order to generate new neurons to help return the eyes to their proper function. "Our next goal is to find those factors that inhibit them from proliferating in their natural region inside the eye and release that inhibition so as to give
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Contact: Steven de Sousa
steven.desousa@utoronto.ca
416-978-5949
University of Toronto
15-Mar-2000