See... blind mice
13 November 2006
Scientists have made a breakthrough that could cure common types of blindness. They've restored sight to blind mice by replacing damaged eye cells with healthy ones - and they hope the same trick could treat blind patients.
Antenna takes a closer look...
This story was published in Nature on 9 November 2006.
Image: Stock.XCHNG/Eirin Henriksen
Every year, thousands of people in the UK go blind because the special light-sensitive cells that line the back of their eyes - photoreceptor cells - get damaged. Now new research suggests that transplanting healthy eye cells to replace damaged ones could help to restore vision.
This patient's light-sensitive photoreceptor cells are damaged - they're the darker areas near the middle of the eye.
Image: Robert MacLaren
What did the scientists do?
The scientists, led by a team from University College London, transplanted developing photoreceptor cells from newly born mice into mice whose photoreceptor cells had been destroyed by a genetic disease. The transplanted cells grew and attached to nerve endings at the back of the eye to form new working photoreceptor cells.
This is what a single transplanted photoreceptor cell looks like under a microscope.
Image: Robert MacLaren
To check the transplant was working, the researchers tested whether the mice could see. Mouse vision can't be measured with an eye chart, so the scientists looked at how the mice responded to light instead. The results showed that the mice's sight was restored to around 25% of normal.
These two pictures show the response of the mice's pupils to dark (a0) and light (a1) after the transplant. Before the transplant these two responses would have looked the same.
Image: Nature Publishing Group
'We believe this is the first time this has ever been done. When I saw the cells I nearly fell off my chair, I was so excited by the results!' says eye surgeon Robert MacLaren, who helped carry out the research.
'The key was using developing cells that were already committed to becoming photoreceptors,' he explains.
Robert MacLaren, Consultant Surgeon, Moorfields Eye Hospital, London
Image: Robert MacLaren
'Before now we had tried using stem cells, which are dividing cells that haven't yet become specialised. But with 220 different cell types in the body, how is a stem cell going to know whether to become a photoreceptor or a skin cell?'
There's also a hitch with the type of cells used in the latest transplant. They can't be used in people because they would have to be taken from developing human embryos - and this isn't legal at the moment. But Robert MacLaren thinks that recent research could provide a way round this.
'Cells that have stem-cell-like properties have now been found in the human eye. If we could take these cells from a patient and work out how to make them become developing photoreceptor cells we could then reimplant them into the patient's own eye.'
This picture is a slice through the human eye and shows the tightly packed photoreceptor cells.
Image: Peter Munro, UCL
'Using the patient's own cells might avoid the problem of rejection, because the cells would be genetically identical to the patient's own.'
Robert MacLaren
Robert MacLaren
Getting this research to work in humans is still some way off though. But the results so far are encouraging.
'We're definitely excited by these findings, as there are so many people out there who have untreatable eye diseases who could potentially benefit,' says Barbara McLaughlan from the Royal National Institute for the Blind.
Image: RNIB
'But this work is still in the very early stages. Several more years of research and trials are needed before we will know if this technique could be used as a treatment for common eye diseases.'