Sooraj Shah ’24
Leber congenital amaurosis (LCA) is a family of retinal disorders, which result in severe vision loss from birth. LCA is one of the most common causes of childhood blindness, affecting approximately 2-3 infants for every 100,000 births. Currently, no direct cure for LCA exists, but recent developments in gene replacement therapy have shown promise in partially restoring retinal light-sensing ability with variability in adolescents. However, it is still not clear if adult visual circuits can be restored. A study led by Dr. Sunil Gandhi, a professor of neurobiology and behavior at the University of California Irvine, focused on the use of chemical compounds called synthetic retinoids to restore visual dysfunction due to LCA in adults.
A major mechanism in LCA involves the visual cycle pathway formation of
11-cis-retinal chromophore, which is a pigment in rod cells within the retina that contibutes to vision. This chromophore was blocked within a mouse model to replicate the function of LCA. The effects of the usage of 9-cis-retinyl acetate (9-cis-R-Ac) as a substitute for 11-cis-retinal on the primary visual cortex (V1) was observed.
The study showed that administration of 9-cis-R-Ac resulted in an increase in the amplitude of responsive neurons within the V1, most significantly restoring ipsilateral function and therefore a balance of the eye-specific response. Ipsilateral restoration is defined as the eye being located on the same side of the body as another object, and it is the signals from the eye which lead to neuronal responses in the brain and then finally visual perception. This is crucial as Gandhi observed this same-side eye pathway exhibiting a five-fold response of activated neurons in the brain after the use of 9-cis-R-Ac.
The study showed the surprising impact of retinoid therapy in adult models, replicated within mouse models. While current therapies focus on the early intervention of LCA through gene replacement and pharmacological agents, the use of retinoids to restore the V1 may be a better avenue to treating LCA in fully developed adults. The focus of future research will include studying retinoid therapies in greater detail to find a more complete understanding of its restoration of V1 in LCA.
- C. Huh. et al. Retinoid therapy restores eye-specific cortical responses in adult mice with retinal degeneration. Current Biology 2022. DOI: 10.1016/j.cub.2022.09.005
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