In the current study, the scientists looked at these photoreceptors' development -- from the embryonic stages to those in the newborn. They found that the cells that worked best came from animals between the first and fifth days of life. "Photoreceptors are just being born and starting to make connections," said Pearson, one of the co-authors of the study, published this week in Nature.
The retinal cells were transplanted in normal adult mice and others with two different types of vision problems that cause blindness. In earlier studies, researchers found that the cells looked like photoreceptors and seemed to act like them. But the real test was laid out in this current study.
Ten mice who received the retinal transplants were studied to see whether there were functional changes. When a light was shone in the retina, electrical signals came out of the cells, suggesting that the animals were responding to a light that under normal situations they would not have seen. Scientists also observed the pupils constricting in the mice, another sign they were registering the light in their eyes and the message was traveling to the brain.
"We restored some aspects of visual function," Pearson said. "But we have no idea yet what the animals can or can't see. It's still a long way off from a human treatment."
So, photoreception was restored, but vision probably was not. I am wondering if a cell transplant of retinal ganglion cells mat restore circadian photoreception - a serious problem in some blind people who "freerun" instead of being synchronized to the day-night cycle.
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