Cell transplants 'restore sight'
Cell transplants have successfully restored vision to
mice which had lost their sight, leading to hopes
people could benefit in the same way.
UK scientists treated animals which had eye damage
similar to that seen in many human eye diseases.
They were able to help them see again by transplanting
immature retinal stem cells into their eyes.
UK experts welcomed the study, published in the
magazine Nature, saying it was "stunning" research.
This is a stunning piece of research that may in the
distant future may lead to transplants in humans to
relieve blindness
Professor Andrew Dick
University of Bristol
If the results can be translated into a treatment for
human eye disease, it could help the millions of
people with conditions ranging from age-related
macular
degeneration to diabetes.
Once the cone and rod photoreceptors in a retina are
lost, they cannot be replaced.
While treatments are being developed which might
prevent or delay the loss of these cells, scientists
are also seeking to help those already affected.
It is thought the retina is one of the best places to
try out cell transplant therapy because photoreceptor
loss initially leaves the rest of the wiring
to the brain intact.
But previous attempts to transplant stem cells, which
can turn into any kind of cell in the body, in the
hope that they will become photoreceptors have
failed because the cells were not developed enough.
Harvest
In this study, funded by the Medical Research Council,
scientists from the University College London
Institutes of Ophthalmology and Child Health and
Moorfields
Eye Hospital transplanted cells which were more
advanced, and already programmed to develop into
photoreceptors.
1 - Early stage retinal cells are taken from a newborn
mouse
2 - They are transplanted into the retina of a mouse
which has lost its sight
3 - The cells implant and connect with existing cells
in the eye, restoring some sight to the mouse.
The team took cells from three to five-day-old mice, a
stage when the retina is about to be formed.
The cells were then transplanted into animals which
had been genetically designed to have conditions which
meant they would gradually lose their sight -
either mimicking the human disease retinitis
pigmentosa or age-related macular degeneration.
The transplants were successful; the photoreceptors
implanted and made electrical connections to the
animals' existing retinal nerve cells - key to
allowing
them to see again.
Tests showed that the mice's pupils responded to light
and that there was activity in the optical nerve,
showing signals were being sent to the brain.
Dr Jane Sowden, one of the study's leaders, said:
"Remarkably, we found that the mature retina,
previously believed to have no capacity for repair, is
in
fact able to support the development of new functional
photoreceptors."
'Not false hope'
To get human retinal cells at the same stage of
development, however, would involve taking stem cells
from a foetus during the second trimester of
pregnancy.
But Dr Robert MacLaren, a specialist at Moorfields Eye
Hospital who worked on the research, said they did not
want to go down that route.
He said the aim now would be to look at adult stem
cells to see if they could be genetically altered to
behave like the mouse retinal cells.
There are some cells on the margin of adult retinas
that have been identified as having stem cell-like
properties, which the team says could be suitable.
Dr MacLaren stressed it would be some time before
patients could benefit from such a treatment, but he
said that at least it was now a possibility.
"Everyday, I sit in my clinic and have to tell
patients that there's nothing I can do.
"I don't want to give patients false hope. But at
least now, if I see a young patient, I can say that
there might be something within your lifetime."
Dr Stephen Minger, a stem cell expert at King's
College London, said: "I think this is important,
superb research - it clearly shows that the host
environment
is important in directing the integration of
transplanted cells."
But Andrew Dick, professor of ophthalmology at the
University of Bristol, added: "As with any basic
research we have to be careful not to overhype.
However,
this is a stunning piece of research that may in the
distant future lead to transplants in humans to
relieve blindness."
Story from BBC NEWS:
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