AAV Mediated GDNF Secretion From Retinal Glia Slows Down Retinal Degeneration in a Rat Model of Retinitis Pigmentosa

Department of Molecular and Cell Biology and the Helen Wills Neuroscience Institute, University of California, Berkeley, California 94720-3190, USA.
Molecular Therapy (Impact Factor: 6.43). 04/2011; 19(9):1602-8. DOI: 10.1038/mt.2011.62
Source: PubMed

ABSTRACT Mutations in over 80 identified genes can induce apoptosis in photoreceptors, resulting in blindness with a prevalence of 1 in 3,000 individuals. This broad genetic heterogeneity of disease impacting a wide range of photoreceptor functions renders the design of gene-specific therapies for photoreceptor degeneration impractical and necessitates the development of mutation-independent treatments to slow photoreceptor cell death. One promising strategy for photoreceptor neuroprotection is neurotrophin secretion from Müller cells, the primary retinal glia. Müller glia are excellent targets for secreting neurotrophins as they span the entire tissue, ensheath all neuronal populations, are numerous, and persist through retinal degeneration. We previously engineered an adeno-associated virus (AAV) variant (ShH10) capable of efficient and selective glial cell transduction through intravitreal injection. ShH10-mediated glial-derived neurotrophic factor (GDNF) secretion from glia, generates high GDNF levels in treated retinas, leading to sustained functional rescue for over 5 months. This GDNF secretion from glia following intravitreal vector administration is a safe and effective means to slow the progression of retinal degeneration in a rat model of retinitis pigmentosa (RP) and shows significant promise as a gene therapy to treat human retinal degenerations. These findings also demonstrate for the first time that glia-mediated secretion of neurotrophins is a promising treatment that may be applicable to other neurodegenerative conditions.

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    • "(2012) 122, 1047–1053. Increased expression of glial cell line-derived neurotrophic factor (GDNF) in the retina slows the death of rod photoreceptors in models of retinal degeneration and reduces retinal degeneration from severe oxidative stress (McGee et al. 2001; Dong et al. 2007; Dalkara et al. 2011; Del Rio et al. 2011). In addition, high levels of GDNF reduced levels of reactive oxygen species in the retina after intraocular injection of paraquat (Dong et al. 2007). "
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    ABSTRACT: Retinitis pigmentosa is a group of diseases in which one of hundreds of mutations causes death of rod photoreceptor cells and then cones gradually die from oxidative damage. As different mutations cause rod cell death by different mechanisms, mutation-specific treatments are needed. Another approach is to use a neurotrophic factor to promote photoreceptor survival regardless of the mechanism of cell death, and previous studies have demonstrated encouraging short-term results with gene transfer of glial cell line-derived neurotrophic factor (GDNF). We generated rd10 mice with doxycycline-inducible expression of GDNF in photoreceptors (Tet/IRBP/GDNF-rd10 mice) or retinal pigmented epithelial cells (Tet/VMD2/GDNF-rd10 mice). In doxycycline-treated Tet/IRBP/GDNF-rd10 mice, there was a 9.3 × 10(4) -fold increase in Gdnf mRNA at P35 and although it decreased over time, it was still increased by 9.4 × 10(3) -fold at P70. Gdnf mRNA was increased 4.5 × 10(2) -fold in doxycycline-treated Tet/VMD2/GDMF-rd10 mice at P35 and was not significantly decreased at P70. GDNF protein levels were increased about 2.3-fold at P35 and 30% at P70 in Tet/IRBP/GDNF-rd10 mice, and in Tet/VMD2/GDNF-rd10 mice they were increased 30% at P35 and not significantly increased at P70. Despite the difference in expression, Tet/IRBP/GDNF-rd10 and Tet/VMD2/GDNF-rd10 mice had comparable significant increases in outer nuclear layer thickness and mean photopic and scotopic ERG b-wave amplitudes compared with rd10 mice at P35 which decreased, but was still significant at P70. Compared with rd10 mice, Tet/IRBP/GDNF-rd10 and Tet/VMD2/GDNF-rd10 mice had comparable significant improvements in cone density at P50 that decreased, but were still significant at P70. These data indicate that despite a large difference in expression of GDNF, Tet/IRBP/GDNF-rd10 and Tet/VMD2/GDNF-rd10 provide comparable slowing of photoreceptor degeneration, but cannot stop the degeneration.
    Journal of Neurochemistry 06/2012; 122(5):1047-53. DOI:10.1111/j.1471-4159.2012.07842.x · 4.24 Impact Factor
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    • "The most effective carriers currently existing are engineered from naturally occurring infectious viral particles. Non-pathogenic adenoassociated viruses have shown remarkable results in the treatment of muscle [1] and eye [2] diseases. Non-viral alternatives exist, involving either cationic lipids [3] [4] or cationic polymers. "
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    Acta biomaterialia 01/2012; 9(2). DOI:10.1016/j.actbio.2012.09.015 · 5.68 Impact Factor
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    ABSTRACT: In normal mice, the lentiviral vector (LV) is very efficient to target the RPE cells, but transduces retinal neurons well only during development. In the present study, the tropism of LV has been investigated in the degenerating retina of mice, knowing that the retina structure changes during degeneration. We postulated that the viral transduction would be increased by the alteration of the outer limiting membrane (OLM). Two different LV pseudotypes were tested using the VSVG and the Mokola envelopes, as well as two animal models of retinal degeneration: light-damaged Balb-C and Rhodopsin knockout (Rho-/-) mice. After light damage, the OLM is altered and no significant increase of the number of transduced photoreceptors can be obtained with a LV-VSVG-Rhop-GFP vector. In the Rho-/- mice, an alteration of the OLM was also observed, but the possibility of transducing photoreceptors was decreased, probably by ongoing gliosis. The use of a ubiquitous promoter allows better photoreceptor transduction, suggesting that photoreceptor-specific promoter activity changes during late stages of photoreceptor degeneration. However, the number of targeted photoreceptors remains low. In contrast, LV pseudotyped with the Mokola envelope allows a wide dispersion of the vector into the retina (corresponding to the injection bleb) with preferential targeting of Müller cells, a situation which does not occur in the wild-type retina. Mokola-pseudotyped lentiviral vectors may serve to engineer these glial cells to deliver secreted therapeutic factors to a diseased area of the retina.
    PLoS ONE 08/2011; 6(8):e23782. DOI:10.1371/journal.pone.0023782 · 3.53 Impact Factor
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