The first
patient-derived stem cell model to research eye conditions related to
oculocutaneous albinism (OCA) has been created.
Researchers at the US
National Eye Institute (NEI) have developed the first patient-derived stem cell
model for studying eye conditions related to oculocutaneous albinism
(OCA).
According to the researchers, OCA is a set of
genetic conditions that affects pigmentation in the eye, skin and hair due to
mutation in the genes crucial to melanin pigment production. In the eye,
pigment is present in the retinal pigment epithelium (RPE) and aids vision by
preventing the scattering of light. The RPE is located right next to the eye’s
light-sensing photoreceptors and provides them nourishment and support. People
with OCA lack pigmented RPE and have an underdeveloped fovea, an area within
the retina that is crucial for central vision.
People with OCA have misrouted optic nerve fibres,
which carry visual signals to the brain. Scientists think that RPE plays a role
in forming these structures and want to understand how lack of pigment affects
their development.
Animals used to study albinism are less than ideal
because they lack foveae,” said Dr Brian Brooks, one of the authors of the paper
published in Stem Cell Reports. “A human stem cell model that mimics the
disease is an important step forward in understanding albinism and testing
potential therapies to treat it.”
To make the model, the researchers reprogrammed
skin cells from individuals without OCA and people with the two most common
types of OCA (OCA1A and OCA2) into induced pluripotent stem cells (iPSCs). The
iPSCs were then differentiated to RPE cells. The RPE cells from OCA patients
were identical to RPE cells from unaffected individuals but displayed
significantly reduced pigmentation.
The researchers say they will use the model to
study how lack of pigmentation affects RPE physiology and function. In theory,
if fovea development is dependent on RPE pigmentation and pigmentation can be
somehow improved, vision defects associated with abnormal fovea development
could be at least partially resolved.
“Treating albinism at a very young age, perhaps
even prenatally, when the eye’s structures are forming, would have the greatest
chance of rescuing vision,” said Brooks. “In adults, benefits might be limited
to improvements in photosensitivity, for example, but children may see more
dramatic effects.”
The team say they are now exploring how to use
their model for high-throughput screening of potential OCA therapies.
“This ‘disease-in-a-dish’ system will help us
understand how the absence of pigment in albinism leads to abnormal development
of the retina, optic nerve fibres and other eye structures crucial for central
vision,” said Dr Aman George, the lead author of the paper.
European Journal of Case Reports and Clinical Images is an international open-access journal publi
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