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Rachel Michelle Stupay, Astra Dinculescu, Seok-Hong Min, Sanford L. Boye, Vince Chiodo Chiodo, William W Hauswirth; Long-term preservation of retinal function in the rd6 mouse model of retinitis pigmentosa following AAV-mediated gene therapy. Invest. Ophthalmol. Vis. Sci. 2016;57(12):1167.
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© ARVO (1962-2015); The Authors (2016-present)
Mutations in the MFRP (membrane-type frizzled-related protein) gene can lead to recessive retinitis pigmentosa (RP). Previously, we showed that gene therapy in the rd6 mouse, a model for MFRP-RP, prevented retinal degeneration and rescued the photoreceptor function for at least 2 months when treatment was initiated early (P14). Our goal was to test the long-term effects of gene therapy on the retinal structure and function in adult rd6 mice following subretinal vector treatment.
One microliter (109 total vector genomes) of an AAV8 (double Y−F+T−V) capsid mutated vector containing the small chicken β-actin (smCBA) promoter driving the wild-type mouse Mfrp cDNA was delivered subretinally to one eye of adult 2 month-old rd6 mice, while contralateral eyes remained un-injected. Retinal function in treated rd6 mice was evaluated by full-field electroretinography (ERG) up to 15 months post-injection, under scotopic or photopic conditions. Treated eyes were also examined by digital fundus imaging and spectral-domain optical coherence tomography. MFRP transgene expression was evaluated by immunohistochemistry and Western blot analysis. For morphological analysis, treated rd6 and control retinal sections were stained with hematoxylin and eosin.
Subretinal AAV8 (double Y−F+T−V) vector treatment led to preservation of photoreceptors and retinal function as determined by morphological and ERG analysis, for at least 15 months following vector delivery. Treatment rescued both rod and cone photoreceptor function. This AAV-mediated gene delivery resulted in MFRP expression at its normal location within the retinal pigment epithelium apical membrane and its microvilli, as determined by immunostaining. AAV-treated rd6 retinas had a greater number of rows of photoreceptor nuclei (6-8) and long, well-organized outer segments, in contrast to untreated retinas, in which the outer segments were dramatically shortened or completely missing, and contained only 1-3 rows of nuclei in the ONL.
Subretinal delivery of Mfrp cDNA in adult mice can preserve retinal function in the rd6 mouse even after the photoreceptor degeneration starts. The beneficial effects can last for more than 1 year after treatment. This result has important therapeutic implications for human patients with MFRP-RP at different stages of disease progression.
This is an abstract that was submitted for the 2016 ARVO Annual Meeting, held in Seattle, Wash., May 1-5, 2016.
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