A preclinical study using
stem cells to produce progenitor photoreceptor cells—light-detecting cells
found in the eye—and then transplanting these into experimental models of
damaged retinas has resulted in significant vision recovery. This finding, by
scientists at Duke-NUS Medical School, the Singapore Eye Research Institute and
the Karolinska Institute in Sweden, marks a first step towards potentially
restoring vision in eye diseases characterised by photoreceptor loss.
“Our laboratory has developed a novel
method that enables the production of photoreceptor progenitor cells resembling
those in human embryos,” said Assistant Professor Tay Hwee Goon, first author of the study from Duke-NUS’ Centre for Vision Research. “Transplantation of these cells into experimental
models has yielded partial restoration of the retinal function.”
The degeneration of photoreceptors in
the eye is a significant cause of declining vision that can eventually lead to
blindness and for which there is currently no effective treatment.
Photoreceptor degeneration occurs in a variety of inherited retinal diseases,
such as retinitis pigmentosa—a rare eye disease that breaks down cells in the
retina over time and eventually causes vision loss—and age-related macular
degeneration, a leading cause of vision impairment worldwide1.
Regions
of photoreceptor regeneration in the retinas of preclinical models (inside
dashed boxes) highlighted by various molecular markers of photoreceptor
function (named at top right).
Asst Prof Tay and her team developed a
procedure to grow human embryonic stem cells in the presence of purified
laminin proteins that are involved in normal development of human retinas. In
the presence of the laminins, stem cells could be directed to differentiate
into photoreceptor progenitor cells responsible for converting light into
signals that are sent to the brain.
When these cells were transplanted into
damaged retinas, the preclinical models showed significant recovery of vision.
A diagnostic test called electroretinogram also identified significant recovery
in the retinas via electrical activity in the retina in response to a light
stimulus. The transplanted cells established connections with surrounding
retinal cells and nerves in the inner retina. They also survived and functioned
for many weeks after transplantation.
Moving forward, the team hopes to refine
their method to make it simpler and achieve more consistent results than
earlier attempts to explore stem cell therapy for photoreceptor cell
replacement.
“It is exciting to find these results,
which suggest a promising route towards using stem cells to treat those forms
of visual deterioration and blindness caused by the loss of photoreceptors,”
said Dr Helder Andre, Head of Molecular and Cellular Research from Karolinska
Institute’s Department of Clinical Neuroscience and a senior author of the
study.
Associate Professor Enrico Petretto, Director of the Centre for Computational Biology at Duke-NUS and the study’s bioinformatics
analysis lead, added: “Our method may also be useful for understanding the
molecular and cellular pathways that drive the progression of macular
degeneration, perhaps leading to the development of other therapeutic
approaches.”
The next challenge for the researchers
is to explore the efficacy of their method in models of photoreceptor
degeneration that more closely match the human condition.
“If we get promising results in our future studies, we hope to move to clinical trials in patients,” said Professor Karl Tryggvason, from Duke-NUS’ Cardiovascular and Metabolic Disorders Programme, and the corresponding author of the study. “That would be an important step towards for being able to reverse damage of the retina and restore vision.”
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