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Jasmina Cehajic Kapetanovic, Annette E Allen, Katherine E Davis, Cyril Giles Eleftheriou, Nina Milosavljevic, Franck P Martial, Paul N Bishop, Robert J Lucas; Restoring vision with ectopic expression of human rod opsin. Invest. Ophthalmol. Vis. Sci. 2015;56(7 ):4832.
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© ARVO (1962-2015); The Authors (2016-present)
Many retinal dystrophies result in photoreceptor loss, but the inner retinal neurons can survive and these are potentially amenable to emerging optogenetic therapies. Here we investigated the effect of ectopic expression of human rod opsin (hRho) on visual function in a mouse model (rd1) of advanced retinal degeneration. We used both an untargetted approach and targetted delivery of hRho to ON-bipolar cells.
Viral gene delivery systems (AAV2-CAG-hRho and AAV2-grm6-hRho) were injected intravitreally into rd1 mice with extracellular matrix degrading glycosidic enzymes. Rod opsin expression was investigated using immunohistochemistry. Retinal function was assessed with pupillometry at 6 weeks post treatment and then ganglion cell activity using a multi-electrode array (MEA). Responses in the brain were examined using in-vivo electrophysiology recordings from the lateral geniculate nucleus (LGN) and locomotory behaviour was assessed in response to various light conditions using a modified open field box.
We found rod opsin expression with both untargetted (CAG) and targetted (Grm6) delivery systems in treated retinas. Untargetted expression restored the pupillary light reflex (PLR), whereas under targeted expression the PLR remained impaired. Both CAG- and grm6-hRho expression restored light responses at the ganglion cell and the LGN levels. Restored in-vivo responses were diverse (ON and OFF), responded under a range of physiological light intensities, in light adapted conditions and to naturalistic movie scenes. Behaviourally, treated mice showed a restoration of light-induced locomotor activity. In addition Rd1-hRho-grm6 mice responded to contrast in light adapted conditions, were able to resolve flicker at up to 10Hz and naturalistic movie scenes.<br />
Ectopic expression of rod opsin restores responses to a wide range of artificial and natural visual stimuli in blind mice at the retinal, brain and behavioural levels under illuminance typical of natural indoor environments. Our approach employs intravitreal injection that is already a routine clinical practice and introduces a native human protein into the retina, minimising the challenges of progression to clinical trials.
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