AsianScientist (Jan. 14, 2013) – Blind mice can see again, after researchers transplanted developing cells into their eyes and found they could reform the entire light-sensitive layer of the retina.

Videos show the nocturnal mice, which once didn’t notice the difference between light and dark at all, now run from the light and prefer to be in the dark – just like mice with normal vision.

The researchers say the approach has relevance for treating patients with retinitis pigmentosa, a condition in which the light-sensing cells in the retina gradually die leading to progressive blindness.

Published in the journal PNAS, the study was led by Dr. Mandeep Singh, an eye surgeon from the National University Hospital of Singapore and a clinician-scientist with the Singapore Eye Research Institute (SERI), while he was a Ph.D. student with Professor Robert MacLaren at the University of Oxford, U.K.

The researchers worked with mice that were blind due to complete loss of the light-sensing photoreceptor cells in their retinas. This is the most relevant mouse model for treating patients who are blind from retinitis pigmentosa.

In the study, immature cells transplanted into the eye re-formed a full light-detecting layer on the retina which restored near-normal vision to the mice. The cells used were mouse ‘precursor’ cells that were on an initial path towards developing into retinal cells.
A pupil constriction test showed that, of the 12 mice that received the cell transplant, 10 showed improved pupil constriction in response to light. This was evidence that the retinas of the mice were sensing the light once more, and the signal was being transmitted down the optic nerve to the brain.

Explaining the significance of the work, Dr. Singh said,
“The immature donor cells not only survived in blind mice recipients but also matured in that environment to become functioning retinal cells. By providing new replacement cells, we found that the retina could be reconstructed.”

“We found that if enough cells are transplanted together, they not only become light sensing but they also regenerate the connections required for meaningful vision.”
Prof. MacLaren believes that new treatments for blind patients will someday be derived from induced pluripotent stem cells (iPS cells). iPS cells are stem cells that have been generated from the patient’s own cells, such as skin or blood cells, which can then be directed to form precursors of the retina cells. 


“All the steps are there for doing this in patients in the future. Our study shows what we could achieve with a cell-based approach,” said MacLaren.


Source: Oxford University; Photo: Richard Winchell/Flickr/CC.

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