The prospect of reversing blindness has made a significant leap, according to scientists in the UK.
An
animal study in the journal Nature Biotechnology showed the part of the
eye which actually detects light can be repaired using stem cells.
The
team at Moorfields Eye Hospital and University College London say human
trials are now, for the first time, a realistic prospect.
Experts described it as a "significant breakthrough" and "huge leap" forward.
Photoreceptors
are the cells in the retina which react to light and convert it into an
electrical signal which can be sent to the brain.
However, these cells can die off in some causes of blindness such as Stargardt's disease and age-related macular degeneration.
There
are already trials in people to use stem cells to replace the "support"
cells in the eye which keep the photoreceptors alive.
Blind mice
Now
the London-based team have shown it is possible to replace the
light-sensing cells themselves, raising the prospect of reversing
blindness.
They have used a new technique for building retinas in
the laboratory. It was used to collect thousands of stem cells, which
were primed to transform into photoreceptors, and injected them into the
eyes of blind mice.
The study showed that these cells could hook up with the existing architecture of the eye and begin to function.
However,
the effectiveness is still low. Only about 1,000 cells out of a
transplant of 200,000 actually hooked up with the rest of the eye.
Lead
researcher Prof Robin Ali said: "This is a real proof of concept that
photoreceptors can be transplanted from an embryonic stem cells source
and it give us a route map to now do this in humans.
"That's why we're so excited, five years is a now a realistic aim for starting a clinical trial."
Rods and cones Rods, blue, and cones, blue-green, detect light and create electrical signals which are sent to the brain
The eye is one of the most advanced fields for stem cell research.
It
is relatively simple as the light sensing cells only have to pass their
electrical message on to one more cell in order to get their message to
the brain, unlike an attempt to reverse dementia which would require
cells to hook up with far more cells all across the brain.
The
immune system is also very weak in the eye so there is a low chance of
the transplant being rejected. A few cells can also make a big
difference in the eye.
Tens of thousands of stem cells in the eye
could improve vision, but that number of stem cells would not regenerate
a much larger organ such as a failing liver.
Prof Chris Mason,
from University College London, told the BBC: "I think they have made a
major step forward here, but the efficiency is still too low for
clinical uses.
"At the moment the numbers of tiny and it will take
quite a bit of work to get the numbers up and then the next question is
"Can you do it in man?"
"But I think it is a significant
breakthrough which may lead to cell therapies and will give a much
expanded knowledge on how to cure blindness."
Dr Marcelo Rivolta,
from the University of Sheffield, said the study was a "huge leap"
forward for treating blindness and could have implications across stem
cell research.
Source: BBC News
