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: 6.23). 04/2011; 19(9):1602-8. DOI: 10.1038/mt.2011.62
Source: PubMed


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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Available from: David Vernon Schaffer, Jul 27, 2015
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    • "Although more than 160 IPD-associated genes have been identified in humans, with many of these mutations modeled in mouse, relatively few studies have examined the biochemical mechanisms that promote or resist death in the mutant PR [1], [2]. Factors shown to promote the survival of mutant or injured PRs include IL-6 cytokines [3], [4], [5], [6], [7], STAT3 [8], and neurotrophic factors including FGF2 [9], [10], [11], [12], [13]. In contrast, other molecules including GFAP and vimentin [14], [15], complement factor D [16], TNFα [17] and poly-ADP-ribose polymerase-1 [18] have been shown to contribute to the death of mutant or injured PRs. "
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    ABSTRACT: Expression of the mRNA is greatly increased in the photoreceptors (PRs) of mouse models of inherited PR degeneration (IPD). To examine the role of in mutant PR survival, we generated mice carrying homozygous alleles or the transgene. In the background, PR survival increased 110% in mice at post-natal (PN) day 15, and 60% in mice at PN40. In contrast, PR survival was not increased in retinal explants of ; mice. This finding, together with systemic abnormalities in mice, suggested that the increased survival of mutant PRs in the background resulted at least partly from the systemic EDN2 loss of function. To examine directly the role of EDN2 in mutant PRs, we used a scAAV5- cDNA vector to restore expression in ; PRs and observed an 18% increase in PR survival at PN14. Importantly, PR survival was also increased after injection of scAAV5- into retinas, by 31% at PN15. Together, these findings suggest that increased expression is protective to mutant PRs. To begin to elucidate -mediated mechanisms that contribute to PR survival, we used microarray analysis and identified a cohort of 20 genes with >4-fold increased expression in retinas, including . Notably, increased expression of the FGF2 protein in PRs was ablated in ; retinas. Our findings indicate that the increased expression of PR increases PR survival, and suggest that the -dependent increase in PR expression of FGF2 may contribute to the augmented survival.
    PLoS ONE 02/2013; 8(2):e58023. DOI:10.1371/journal.pone.0058023 · 3.23 Impact Factor
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    • "These results indicate that gene therapy may be a useful technique in the treatment of other neurological disorders as it allows for the localised, targeted, stable and efficient introduction of a gene or genes. Neuroprotective and regenerative therapies using trophic factors, such as NTs, have garnered much attention of late, particularly in the areas of Parkinson’s disease, retinitis pigmentosa and spinal cord injury, just to name a few [48], [49], [50]. Initial clinical studies involving Parkinson’s disease patients, for example, used a mechanical pump to infuse glial cell-derived neurotrophic factor (GNDF) into the lateral ventricles. "
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    ABSTRACT: The cochlear implant provides auditory cues to profoundly deaf patients by electrically stimulating the residual spiral ganglion neurons. These neurons, however, undergo progressive degeneration after hearing loss, marked initially by peripheral fibre retraction and ultimately culminating in cell death. This research aims to use gene therapy techniques to both hold and reverse this degeneration by providing a sustained and localised source of neurotrophins to the deafened cochlea. Adenoviral vectors containing green fluorescent protein, with or without neurotrophin-3 and brain derived neurotrophic factor, were injected into the lower basal turn of scala media of guinea pigs ototoxically deafened one week prior to intervention. This single injection resulted in localised and sustained gene expression, principally in the supporting cells within the organ of Corti. Guinea pigs treated with adenoviral neurotrophin-gene therapy had greater neuronal survival compared to contralateral non-treated cochleae when examined at 7 and 11 weeks post injection. Moreover; there was evidence of directed peripheral fibre regrowth towards cells expressing neurotrophin genes after both treatment periods. These data suggest that neurotrophin-gene therapy can provide sustained protection of spiral ganglion neurons and peripheral fibres after hearing loss.
    PLoS ONE 12/2012; 7(12):e52338. DOI:10.1371/journal.pone.0052338 · 3.23 Impact Factor
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    • "The expression of IL6, an interleukin found to prevent photoreceptors from degeneration after retinal detachment [39] as well as retinal ganglion cell apoptosis in the setting of increased intraocular pressure [34], was strongly increased (9, 24, and 18-fold at 8, 24, and 48 hours, respectively) post-ESMV treatment. Glial- derived neurotrophic factor (GDNF), a growth factor shown to exert long-term neuroprotection when secreted from Müller cells in a rat model of retinitis pigmentosa [68] and increase long-term ganglion cell survival in glaucoma [69] was also strongly up-regulated at all times post-ESMV administration. The expression of neuregulins 1 and 2, known to promote survival and neurite extension from retinal neurons during retinal development [35], and FGF2, a growth factor demonstrated to slow down photoreceptor degeneration in retinitis pigmentosa [70] and promote retinal regeneration from progenitor cells in Xenopus [71] were also increased significantly at all times post-ESMV exposure. "
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    ABSTRACT: Cell-derived microvesicles (MVs), recognized as important components of cell-cell communication, contain mRNAs, miRNAs, proteins and lipids and transfer their bioactive contents from parent cells to cells of other origins. We have studied the effect that MVs released from embryonic stem cells (ESMVs) have on retinal progenitor Müller cells. Cultured human Müller cells were exposed to mouse ESMVs every 48 hours for a total of 9 treatments. Morphological changes were observed by light microscopy in the treated cells, which grew as individual heterogeneous cells, compared to the uniform, spindle-like adherent cellular sheets of untreated cells. ESMVs transferred to Müller cells embryonic stem cell (ESC) mRNAs involved in the maintenance of pluripotency, including Oct4 and Sox2, and the miRNAs of the 290 cluster, important regulators of the ESC-specific cell cycle. Moreover, ESMV exposure induced up-regulation of the basal levels of endogenous human Oct4 mRNA in Müller cells. mRNA and miRNA microarrays of ESMV-treated vs. untreated Müller cells revealed the up-regulation of genes and miRNAs involved in the induction of pluripotency, cellular proliferation, early ocular genes and genes important for retinal protection and remodeling, as well as the down-regulation of inhibitory and scar-related genes and miRNAs involved in differentiation and cell cycle arrest. To further characterize the heterogeneous cell population of ESMV-treated Müller cells, their expression of retinal cell markers was compared to that in untreated control cells by immunocytochemistry. Markers for amacrine, ganglion and rod photoreceptors were present in treated but not in control Müller cells. Together, our findings indicate that ESMs induce de-differentiation and pluripotency in their target Müller cells, which may turn on an early retinogenic program of differentiation.
    PLoS ONE 11/2012; 7(11):e50417. DOI:10.1371/journal.pone.0050417 · 3.23 Impact Factor
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