July 22, 2013
Using Stem Cells To Treat Blindness
Brett Smith for redOrbit.com - Your Universe Online
A new study published in the journal Nature Biotechnology represents a major step forward in curing certain types of blindness.
While previous efforts have successfully focused on keeping the photoreceptors' support cells alive, the new treatment aims to replace the retina's key cells directly. These cells sense light and are connected to other cells that relay the visual information to the brain.
The new technique expands on work done by Japanese researchers who used mice stem cells to fashion new retinas. The London team created photoreceptor cells and placed them in the eyes of blind mice.
After being injected, the new cells were able to connect with the mice's existing framework - albeit at a relatively low level of effectiveness. Approximately 1,000 of the 200,000 transplanted cells were able to connect with the rest of the eye.
"This is a real proof of concept that photoreceptors can be transplanted from an embryonic stem cells source and it give us a route map to now do this in humans," said lead researcher Robin Ali, a professor of Human Molecular Genetics at the University College of London. "That's why we're so excited, five years is now a realistic aim for starting a clinical trial."
The eye is one of the most promising candidates for stem cell therapy because there is only one type of intermediary cell between photoreceptors and the brain, unlike other organs which require far more connections between newly generated cells. A relatively small number - tens of thousands - of stem cells could improve vision, a number that would not make much of a difference in the liver or brain.
The eye's relatively weak local immune system also makes it an ideal candidate for stem cell therapy. A weak immune system means a lower chance of transplanted cells being rejected.
While experts described the study as a "huge leap" forward, some expressed concerns about the stem cells' relatively low connection rate.
"I think they have made a major step forward here, but the efficiency is still too low for clinical uses," Chris Mason, from University College London, told the BBC. "At the moment the numbers are tiny and it will take quite a bit of work to get the numbers up and then the next question is - can you do it in man?"
"But I think it is a significant breakthrough which may lead to cell therapies and will give a much expanded knowledge on how to cure blindness," Mason added.
The new technique could eventually bring relief to those suffering from macular degeneration, a disease marked by the destruction of the macula, the part of the eye necessary for clear vision. The condition is the leading cause of vision loss in adults over 50 years of age and is most likely to affect those who smoke or have a family history of the disease.