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Photoreceptor transplant restores vision in mice
22 May 2012
In an important study, the Gene and Cell Therapy Group have showed for the first time that transplanting light-sensitive photoreceptors into the eyes of visually impaired mice can restore their vision.
The results, published in Nature, suggest that transplanting photoreceptors – light-sensitive nerve cells that line the back of the eye – could form the basis of a new treatment to restore sight in people with degenerative eye diseases.
Dr. Rachael Pearson injected cells from young healthy mice directly into the retinas of adult mice that lacked functional rod photoreceptor cells - rod cells are vital for seeing in the dark as they are extremely sensitive to even low levels of light. Loss of photoreceptors is the cause of blindness in many human eye diseases including age-related macular degeneration, retinitis pigmentosa and diabetes-related blindness.
After four to six weeks, the transplanted cells appeared to be functioning almost as well as normal rod photoreceptor cells and had formed the connections needed to transmit visual information to the brain.
We also tested the vision of the treated mice in a dimly lit maze. Those mice with newly transplanted rod cells were able to use a visual cue to quickly find a hidden platform in the maze whereas untreated mice were able to find the hidden platform only by chance after extensive exploration of the maze.
“We’ve shown for the first time that transplanted photoreceptor cells can integrate successfully with the existing retinal circuitry and truly improve vision. We’re hopeful that we will soon be able to replicate this success with photoreceptors derived from embryonic stem cells and eventually to develop human trials. “Although there are many more steps before this approach will be available to patients, it could lead to treatments for thousands of people who have lost their sight through degenerative eye disorders. The findings also pave the way for techniques to repair the central nervous system as they demonstrate the brain’s amazing ability to connect with newly transplanted neurons.”
The cells transplanted were immature (or progenitor) rod photoreceptor cells, that are used for peripheral vision and night-vision.
We are now finding ways to improve the efficiency of cone photoreceptor transplantation and to increase the effectiveness of transplantation in very degenerate retina. We will probably need to do both in order to develop effective treatments for patients.
We have demonstrated previously, in another study published in Nature, that it is possible to transplant photoreceptor cells into an adult mouse retina, provided the cells from the donor mouse are at a specific stage of development - when the rod photoreceptors are almost, but not fully, formed. In this study we improved the procedure to increase the number of rod cells integrated into the recipient mice and so were able to restore vision.
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