Cell transplants help restore sight in blind mice
8th November
Scientists have overcome a major hurdle in central nervous system repair to restore vision in blind mice. The team’s work, funded by the Medical Research Council, could have a significant impact on stem cell therapy, particularly for patients with untreatable eye diseases. Their work is published tomorrow, November 9th, in Nature.
The mice had a form of eye damage known as photoreceptor loss which occurs in many human eye diseases, from age-related macular degeneration to diabetes. It currently causes irreversible blindness.
It is thought the retina is one of the best places to try out stem cell therapy because photoreceptor loss initially leaves the rest of the wiring to the brain intact. The scientists thought that transplanted photoreceptors would need only make one short connection to restore sight.
However until now, attempts to do this have failed. Previously, brain and retina derived stem cells, which have the ability to become a number of different neural cells, have shown little evidence of integrating into their new environment and becoming new photoreceptors following transplantation.
But the team of scientists from UCL Institute of Ophthalmology and UCL Institute of Child Health and Dr Robert MacLaren, a clinician scientist and eye surgeon from Moorfields Eye Hospital, revisited the idea that the transplanted cells should be undifferentiated stem cells at the earliest developmental stages. The group, led by Professor Robin Ali and Dr Jane Sowden, decided to transplant cells at a later developmental stage which would have to develop into retinal cells and become photoreceptors.
“We worked on the theory that cells at a later stage of development might have a higher probability of success upon transplantation. And we show here that cells taken from the peak rod genesis stage of development, when the retina is about to be formed, can be successfully transplanted and integrate into the adult or degenerating retina,” said Professor Ali.
The scientists were successful in restoring some vision to blind mice by transplanting into their retinas cells committed to becoming photoreceptors.
“Remarkably we found that the mature retina, previously believed to have no capacity for repair is in fact able to support the development of new functional photoreceptors,” said Dr Sowden.
In order to achieve equivalent results in humans, there is a possibility of using embryonic stem cells, but it is thought this might not be necessary.
Professor Ali said: “Recent research has shown that a population of cells can be found on the margin of the adult retina which have stem cell-like properties, in other words they are capable of self-renewal. These could be harvested through minor surgery and grown in the lab to become photoreceptor precursors before being re-implanted on the retina.”
“This research is the first to show that photoreceptor transplantation is feasible. We are now confident that this is the avenue to pursue to uncover ways of restoring vision to thousands who have lost their sight. We will be pursuing the idea of using the stem cell-like retinal cells particularly as these could be harvested from the affected patient, thus avoiding rejection,” said Dr Robert MacLaren.
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