Photoreceptor Transplant Restores Vision In Mice
18 April 2012
In a landmark project, scientists funded by the Medical Research Council (MRC) and RP Fighting Blindness have shown for the first time that transplanting light-sensitive photoreceptors into the eyes of visually impaired mice can restore their vision.
The research, published in Nature, suggests 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 retinitis pigmentosa (RP).
Scientists from UCL Institute of Ophthalmology injected cells from young healthy mice directly into the retinas of adult mice that lacked functional rod-photoreceptors. Loss of photoreceptors is the cause of blindness in many human eye diseases including RP.
There are two types of photoreceptor in the eye – rods and cones. The cells transplanted were immature (or progenitor) rod-photoreceptor cells. Rod cells are especially important for seeing in the dark as they are extremely sensitive to even low levels of light.
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.
The researchers 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.
Professor Robin Ali at UCL Institute of Ophthalmology, who led the research, said “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.”
Dr Rachael Pearson from UCL Institute of Ophthalmology added "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.”
The researchers had demonstrated previously 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 retina is almost, but not fully, formed. In this latest study they optimised the rod transplantation procedure to increase the number of cells integrated into the recipient mice and so were able to restore vision.
David Head, Chief Executive at RP Fighting Blindness, which contributed to the work and represents many RP patients, said “This is fantastic progress and exciting for patients faced with sight loss as a result of RP. To read that 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 is truly amazing.
“Once again RP Fighting Blindness is proud to be associated with Professor Ali and Dr Pearson’s work, such cutting edge research is offering hope for the 25,000 people across the UK affected by RP. Preserving and restoring sight are our ultimate aims and this is a great step forward.”
Video footage of Professor Ali describing and demonstrating the mouse maze is available at this Youtube link and the full paper as published in nature is at the link at the foot of this page.
Questions and Answers
How is RP Fighting Blindness involved?
The charity has supported Professor Ali's work for many years and continues to do so, through a number of research grants. Included is a grant of £190,000 to support this particular project, delivered by Professor Ali and Dr Pearson.
What happens next?
It is too early to say at present. Ultimately the objective is to secure the approval and funding for human clinical trials of similar treatments but the time frames for this are uncertain. In the meantime optimising the procedure, extending it to cone cells, and determining where transplanted cells should be sourced are all priorities.
How long before a cure might come from this work?
Again, it is far too early to say. Though the work is very exciting, even getting to the stage of securing approval for human clinical trials is a long one and then a series of trials may take several years. It would be unfair on RP patients to speculate on this.
Where Can I Learn more?
RP Fighting Blindness keeps members up to date with research news and organises information events for its members, you can join the charity using the link at the top of this page.
Professor Ali is speaking at our conference on June 23rd 2012, more details of this event and how to book are available linked from our home page.
This article is based on a press release from UCL and more information is available from Clare Ryan, Media relations Manager, on 0203 108 3846 or clare.ryan@ucl.ac.uk |
