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Samantha R De Silva, Alun R Barnard, Mandeep S Singh, Michelle McClements, Matthew During, Mark Hankins, Robert E MacLaren; Subretinal delivery of human melanopsin using capsid mutant AAV 2/8 Y733F results in sustained expression at one year with restoration of pupil responses in the rd1 mouse. Invest. Ophthalmol. Vis. Sci. 2014;55(13):3297.
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A strategy for restoring visual function to the degenerate retina is to express a photopigment in residual retinal cells and make them light sensitive in the absence of functional rods and cones. We aimed to assess whether long term expression of the photopigment melanopsin could be achieved following subretinal injection of capsid mutant AAV in the rd1 mouse model of retinal degeneration. To assess whether this could restore visual function, we examined if the pupil light response in the rd1 mouse could be improved by treatment with human melanopsin.
Capsid mutant AAV (rAAV2/8.Y733F) expressing human melanopsin was delivered via subretinal injection to the left eye of 15 Pde6brd1/rd1 mice. 9 mice were injected with phosphate-buffered saline (sham group) and 13 untreated mice were also included. 12 months after treatment, pupil responses were recorded from the right eye following stimulation of the left eye with a 2 second white light stimulus of varying intensity.
12 months after subretinal injection, a large area of retina in each treated eye expressed human melanopsin, as confirmed by immunohistochemistry. At a light intensity of 2 x 1015 photons/cm2/s, which was in the mid-range of the light intensities tested, there was significantly more pupil constriction in the treated group (mean constriction 36.0%+/-7.06) versus the sham treated group (3.1%+/-1.45) and the untreated group (15.6%+/-6.61); treated versus sham p=0.0026, treated versus untreated p=0.038 2 way ANOVA, Tukey’s post hoc test.
Human melanopsin can be successfully delivered via subretinal injection to the mouse degenerate retina using capsid mutant AAV, with a sustained high level of gene expression seen after 12 months. The pupil light response in treated animals was significantly improved compared to sham-injected and untreated mice, providing evidence that human melanopsin mediated photosensitivity can restore visual function in the degenerate retina.
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