Transplanting photoreceptor cells into eyes restores sight in mice
8 May 2012
Scientists at University College Loondon Institute of
Ophthalmology have shown for the first time that transplanting
light-sensitive photoreceptors into the eyes of visually impaired mice
can restore their vision.
Loss of photoreceptors is the cause of blindness in many human eye
diseases including age-related macular degeneration, retinitis
pigmentosa and diabetes-related blindness.
The research, published in Nature, suggests that
transplanting photoreceptors — the 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.
Photoreceptor cells of the eye
Scientists injected cells from young healthy mice directly into
the retinas of adult mice that lacked functional rod-photoreceptors.
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
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.
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.
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.”
Dr Rachael Pearson from UCL Institute of Ophthalmology and
principal author, said: “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
Dr Rob Buckle, head of regenerative medicine at the MRC
said:“This is a landmark study that will inform future research
across a wide range of fields including vision research,
neuroscience and regenerative medicine. It provides clear evidence
of functional recovery in the damaged eye through cell
transplantation, providing great encouragement for the development
of stem cell therapies to address the many debilitating eye
conditions that affect millions worldwide.”
The researchers demonstrated previously (2010), 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 retina is almost, but not fully, formed. In this study they
optimised the rod transplantation procedure to increase the number
of cells integrated into the recipient mice and so were able to