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Endothelin-1 mediated regulation of extracellular matrix collagens in cells of human lamina cribrosa. Exp Eye Res 2008; 86:886-94. [PMID: 18420197 DOI: 10.1016/j.exer.2008.03.003] [Citation(s) in RCA: 27] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2007] [Revised: 01/11/2008] [Accepted: 03/05/2008] [Indexed: 11/21/2022]
Abstract
Endothelin-1 (ET-1), a potent vaso-active peptide, mediates extracellular matrix regulation resulting in an increase in collagen deposition in various cell types and tissues and has been proposed to play a key role in glaucoma pathology. The role of ET-1 in the regulation of extracellular matrix collagens at the level of optic nerve head is not known. In this study we have examined the role of ET-1 in extracellular matrix collagen regulation in primary cultures of human lamina cribrosa cells. Our hypothesis is that ET-1 increases remodeling of the ECM of cells of the lamina cribrosa. Such actions could contribute to the development of optic neuropathy. QPCR analysis revealed that ET-1 mediated an increase in mRNA levels of collagen type I alpha1 and collagen type VI alpha1 chains at all doses of ET-1 with a significant increase at 1nM and 10nM concentration in LC cells. A dose-dependent increase in collagen type I and type VI protein deposition and secretion was also observed by Western blot in response to ET-1 and was significant at 10nM and 100nM concentrations of ET-1. ET-1 increased the [3H] proline uptake in LC cells suggesting that ET-1 contributed to an increase in total collagen synthesis in LC cells. ET-1-mediated increase in collagen type I, type VI and total collagen synthesis was significantly blocked by the ET(A) receptor antagonist, BQ610, as well as with the ET(B) receptor antagonist, BQ788, suggesting the involvement of both receptor subtypes in ET-1 mediated collagen synthesis in LC cells. These results suggest that ET-1 regulates extracellular matrix collagen synthesis in LC cells and may contribute to ECM remodeling at the level of LC of POAG subjects who have elevated plasma and aqueous humor levels of endothelin-1.
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202
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Iwabe S, Moreno-Mendoza NA, Trigo-Tavera F, Crowder C, García-Sánchez GA. Retrograde axonal transport obstruction of brain-derived neurotrophic factor (BDNF) and its TrkB receptor in the retina and optic nerve of American Cocker Spaniel dogs with spontaneous glaucoma. Vet Ophthalmol 2008; 10 Suppl 1:12-9. [PMID: 17973830 DOI: 10.1111/j.1463-5224.2007.00504.x] [Citation(s) in RCA: 50] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
OBJECTIVE To determine the degree of retrograde optic nerve axonal transport obstruction at the scleral lamina cribosa level by examining levels of brain-derived neurotrophic factor (BDNF) and its tyrosine kinase receptor type B (TrkB) in dogs presenting with high intraocular pressure. ANIMALS STUDIED A total of 10 eyes, four normal and six glaucomatous eyes, from normal and affected American Cocker Spaniels with primary glaucoma were studied. All eyes were assessed by neuro-ophthalmic examination, tonometry, gonioscopy, slit-lamp biomicroscopy, and indirect ophthalmoscopy prior to enucleation. METHODS Immunocytochemistry analysis was performed to evaluate BDNF and TrkB receptor expression in retina and optic nerve in normal and glaucomatous dogs. RESULTS In all normal eyes BDNF immunostaining was detected in the cytoplasm of retinal ganglion cells (RGC), inner plexiform layer (IPL), inner nuclear layer (INL), nerve fiber layer (NFL), optic nerve head cells, and lamina cribosa cells. In all glaucomatous eyes BDNF was more evident in RGC, NFL and lamina cribosa cells. TrkB receptor was detected in the cytoplasm of RGC, NFL and ONH bundles in all normal eyes, and in a more intense pattern in all glaucomatous eyes. CONCLUSIONS BDNF retrograde axonal transport is substantially inhibited by intraocular pressure elevation. TrkB accumulation at the ONH in glaucoma suggests a role for neurotrophin deprivation in the pathogenesis of RGC death in canine glaucoma, as well as a possible paracrine and/or autocrine signaling within the lamina cribosa. Neurotrophin signaling may regulate more than neuronal development, survival and differentiation. BDNF neurotrophin and its TrkB receptor expression by lamina cribosa cells and ONH astrocytes in glaucomatous eyes may help to determine the role of these cells as a paracrine source in terms of retinal ganglion cell survival, during episodes of elevated intraocular pressure.
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Affiliation(s)
- Simone Iwabe
- Facultad de Medicina Veterinaria y Zootecnia, Universidad Nacional Autónoma de México, DF, México
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203
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Cooper NGF, Laabich A, Fan W, Wang X. The relationship between neurotrophic factors and CaMKII in the death and survival of retinal ganglion cells. PROGRESS IN BRAIN RESEARCH 2008; 173:521-40. [PMID: 18929132 DOI: 10.1016/s0079-6123(08)01136-9] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/04/2022]
Abstract
The scientific discourse relating to the causes and treatments for glaucoma are becoming reflective of the need to protect and preserve retinal neurons from degenerative changes, which result from the injurious environment associated with this disease. Knowledge, in particular, of the signal transduction pathways which affect death and survival of the retinal ganglion cells is critical to this discourse and to the development of a suitable neurotherapeutic strategy for this disease. The goal of this chapter is to review what is known of the chief suspects involved in initiating the cell death/survival pathways in these cells, and what still remains to be uncovered. The least controversial aspect of the subject relates to the potential role of neurotrophic factors in the protection of the retinal ganglion cells. On the other hand, the postulated triggers for signaling cell death in glaucoma remain controversial. Certainly, the restricted flow of neurotrophic factors has been cited as one possible trigger. However, the connections between glaucoma and other factors present in the retina, such as glutamate, long held to be a prospective culprit in retinal ganglion cell death are still being questioned. Whatever the outcome of this particular debate, it is clear that the downstream intersections between the cell death and survival pathways should provide important foci for future studies whose goal is to protect retinal neurons, situated as they are, in the stressful environment of a cell destroying disease. The evidence for CaMKII being one of these intersecting points is discussed.
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Affiliation(s)
- N G F Cooper
- Department of Anatomical Sciences and Neurobiology, University of Louisville School of Medicine, Louisville, KY 40292, USA.
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204
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Glaucoma of the brain: a disease model for the study of transsynaptic neural degeneration. PROGRESS IN BRAIN RESEARCH 2008; 173:465-78. [PMID: 18929128 DOI: 10.1016/s0079-6123(08)01132-1] [Citation(s) in RCA: 87] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/03/2022]
Abstract
The identification of mechanisms precipitating neuronal death and injury is an intense area of investigation requiring reliable models to assess the effects of neuroprotective agents. Most are suboptimal since the effects of initial damage are diffuse and may not be reproducible or easily quantifiable. The ideal laboratory model should have the ability to (a) clearly detect evidence of neuronal injury and recovery, (b) accurately measure morphologically the extent of these changes, and (c) provide functional evidence for damage and recovery. Glaucoma is a disease of visual neurons in the eye and brain. In the visual system, neuroanatomical pathways and retinotopic organization are exquisitely defined, functional modalities are highly characterized and can be dissected physiologically, visual input parameters can be modified, visual functional output can be readily tested and measured, changes in the eye and the visual brain can be directly visualized and imaged, and pathological and compensatory changes in brain centers of vision can be examined and measured specifically. For these reasons, the glaucoma disease model is ideal for the study of response and recovery to injury in the central nervous system due to anterograde and retrograde degeneration from the eye to the brain and the brain to the eye, respectively. The study of this glaucoma model of transsynaptic brain injury may be relevant to understanding more complex pathways and point to new strategies to prevent disease progression in other neurodegenerative diseases.
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205
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The expression of heat shock protein 27 in retinal ganglion and glial cells in a rat glaucoma model. Neuroscience 2007; 150:692-704. [DOI: 10.1016/j.neuroscience.2007.09.078] [Citation(s) in RCA: 26] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2007] [Revised: 09/13/2007] [Accepted: 09/28/2007] [Indexed: 11/21/2022]
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206
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Abstract
Animal models are useful to elucidate the etiology and pathology of glaucoma and to develop novel and more effective therapies for the disease. Because of the substantial similarities between the rodent and primate eyes, and the advances of relevant study techniques, rat and mouse models of glaucoma have recently become popular as research tools. This review surveys research techniques used in the measurement of rodent intraocular pressure, and also the evaluation of pertinent morphologic, biochemical, and functional changes in the retina, optic nerve head, and optic nerve. This review further describes in detail the individual rodent models, some of which serve as surrogate models and do not entail ocular hypertension, whereas others involve transient or chronic increases of intraocular pressure. The technical considerations and theoretical concerns of these models, their advantages, and limitations, are also discussed.
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Affiliation(s)
- Iok-Hou Pang
- Glaucoma Research, Alcon Research, Ltd, Fort Worth, TX, USA.
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207
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Hong S, Lee JE, Kim CY, Seong GJ. Agmatine protects retinal ganglion cells from hypoxia-induced apoptosis in transformed rat retinal ganglion cell line. BMC Neurosci 2007; 8:81. [PMID: 17908330 PMCID: PMC2089075 DOI: 10.1186/1471-2202-8-81] [Citation(s) in RCA: 52] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/03/2007] [Accepted: 10/02/2007] [Indexed: 11/17/2022] Open
Abstract
BACKGROUND Agmatine is an endogenous polyamine formed by the decarboxylation of L-arginine. We investigated the protective effects of agmatine against hypoxia-induced apoptosis of immortalized rat retinal ganglion cells (RGC-5). RGC-5 cells were cultured in a closed hypoxic chamber (5% O2) with or without agmatine. Cell viability was determined by lactate dehydrogenase (LDH) assay and apoptosis was examined by annexin V and caspase-3 assays. Expression and phosphorylation of mitogen-activated protein kinases (MAPKs; JNK, ERK p44/42, and p38) and nuclear factor-kappa B (NF-kappaB) were investigated by Western immunoblot analysis. The effects of agmatine were compared to those of brain-derived neurotrophic factor (BDNF), a well-known protective neurotrophin for retinal ganglion cells. RESULTS After 48 hours of hypoxic culture, the LDH assay showed 52.3% cell loss, which was reduced to 25.6% and 30.1% when agmatine and BDNF were administered, respectively. This observed cell loss was due to apoptotic cell death, as established by annexin V and caspase-3 assays. Although total expression of MAPKs and NF-kappaB was not influenced by hypoxic injury, phosphorylation of these two proteins was increased. Agmatine reduced phosphorylation of JNK and NF-kappaB, while BDNF suppressed phosphorylation of ERK and p38. CONCLUSION Our results show that agmatine has neuroprotective effects against hypoxia-induced retinal ganglion cell damage in RGC-5 cells and that its effects may act through the JNK and NF-kappaB signaling pathways. Our data suggest that agmatine may lead to a novel therapeutic strategy to reduce retinal ganglion cell injury related to hypoxia.
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Affiliation(s)
- Samin Hong
- Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea
| | - Jong Eun Lee
- Department of Anatomy, Yonsei University College of Medicine, Seoul, Korea
| | - Chan Yun Kim
- Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea
| | - Gong Je Seong
- Institute of Vision Research, Department of Ophthalmology, Yonsei University College of Medicine, Seoul, Korea
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208
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Hu Y, Arulpragasam A, Plant GW, Hendriks WTJ, Cui Q, Harvey AR. The importance of transgene and cell type on the regeneration of adult retinal ganglion cell axons within reconstituted bridging grafts. Exp Neurol 2007; 207:314-28. [PMID: 17689533 DOI: 10.1016/j.expneurol.2007.07.001] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/27/2007] [Revised: 06/27/2007] [Accepted: 07/02/2007] [Indexed: 12/22/2022]
Abstract
When grafted onto the cut optic nerve, chimeric peripheral nerve (PN) sheaths reconstituted with adult Schwann cells (SCs) support the regeneration of adult rat retinal ganglion cell (RGC) axons. Regrowth can be further enhanced by using PN containing SCs transduced ex vivo with lentiviral (LV) vectors encoding a secretable form of ciliary neurotrophic factor (CNTF). To determine whether other neurotrophic factors or different cell types also enhance RGC regrowth in this bridging model, we tested the effectiveness of (1) adult SCs transduced with brain-derived neurotrophic factor (BDNF) or glial cell line-derived neurotrophic factor (GDNF), and (2) fibroblasts (FBs) genetically modified to express CNTF. SCs transduced with LV-BDNF and LV-GDNF secreted measurable and bioactive amounts of each of these proteins, but reconstituted grafts containing LV-BDNF or LV-GDNF transduced SCs did not enhance RGC survival or axonal regrowth. LV-BDNF modified grafts did, however, contain many pan-neurofilament immunolabeled axons, many of which were also immunoreactive for calcitonin gene-related peptide (CGRP) and were presumably of peripheral sensory origin. Nor-adrenergic and cholinergic axons were also seen in these grafts. There were far fewer axons in LV-GDNF engineered grafts. Reconstituted PN sheaths containing FBs that had been modified to express CNTF did not promote RGC viability or regeneration, and PN reconstituted with a mixed population of SCs and CNTF expressing FBs were less effective than SCs alone. These data show that both the type of neurotrophic factor and the cell types that express these factors are crucial elements when designing bridging substrates to promote long-distance regeneration in the injured CNS.
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Affiliation(s)
- Ying Hu
- School of Anatomy and Human Biology, The University of Western Australia, Crawley, WA 6009, Australia
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209
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Pietropaolo S, Paterna JC, Büeler H, Feldon J, Yee BK. Bidirectional changes in water-maze learning following recombinant adenovirus-associated viral vector (rAAV)-mediated brain-derived neurotrophic factor expression in the rat hippocampus. Behav Pharmacol 2007; 18:533-47. [PMID: 17762522 DOI: 10.1097/fbp.0b013e3282da0bf6] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/31/2022]
Abstract
Alterations in hippocampal brain-derived neurotrophic factor (BDNF) expression have been implicated in the pathogenesis of emotional and cognitive dysfunction. Here, we induced BDNF overexpression in the rat hippocampus using recombinant adenovirus-associated viral (rAAV) vectors, and studied its long-term (2 months postinduction) effects on anxiety-related behaviour, exploration in the open field, and spatial learning in the water maze. Although the treatment successfully led to substantial elevation of hippocampal BDNF levels, its effect on spatial learning was bidirectional: a subset of rAAV-induced BDNF-overexpressing rats performed well above control level, whereas the rest were clearly impaired. This behavioural distinction corresponded to two markedly different levels of BDNF overexpression. The increase in dorsal hippocampal BDNF content achieved in the 'water-maze-impaired' subgroup was twice that attained in the 'water-maze-improved' rats. Although neither subgroup of rAAV-induced BDNF-overexpressing rats differed from controls in the open field, the 'water-maze-impaired' subgroup also showed a significant anxiolytic effect. Our results suggest that hippocampal BDNF elevation significantly affects cognitive and emotional behaviours, but the direction and magnitude of the effects critically depend on the precise levels of overexpression. This factor must be taken into account in future studies examining the functional consequences of hippocampal BDNF overexpression.
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210
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Kim HS, Chang YI, Kim JH, Park CK. Alteration of retinal intrinsic survival signal and effect of
α2–adrenergic receptor agonist in the retina of the chronic
ocular hypertension rat. Vis Neurosci 2007; 24:127-39. [PMID: 17640403 DOI: 10.1017/s0952523807070150] [Citation(s) in RCA: 23] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2006] [Accepted: 02/12/2007] [Indexed: 11/07/2022]
Abstract
The purpose of this study is to examine the retinal expression of
intrinsic cell survival molecules and to elucidate the effect of an
α2-adrenergic receptor agonist in the chronic ocular hypertensive rat
model. Chronic ocular hypertension was induced in both eyes of each rat by
episcleral vein cauterization. Two five-microliter drops of the selective
α2-adrenoceptor agonist brimonidine 0.2% (Alphagan; Allergan Inc.,
Irvine, CA, USA) were topically administered twice daily for up to eight
weeks in one eye. The fellow eye received balanced salt solution as a
control. Protein and mRNA expression were evaluated at 1, 4, and 8 weeks
after injury. Retinal expression of BDNF, Akt, and GFAP was assessed using
immunohistochemistry. Retinal levels of mRNA for BDNF, bcl-2, and bcl-xL
were determined using semi-quantitative RT-PCR. Retinal ganglion cell
(RGC) density was evaluated after retrograde labeling with 4-Di-10-ASP
(DiA). A significant decrease in RGC density was observed in ocular
hypertensive eyes. Cauterized eyes showed an increase in GFAP expression
from one week after injury, and the expression of bcl-2, bcl-xL, and BDNF
mRNA was also increased. Treatment of ocular hypertensive eyes with
brimonidine resulted in a reduction in RGC loss, a decrease in the level
of GFAP immunoreactivity, and an increment in BDNF mRNA and p-Akt
expression. Brimonidine appears to protect RGCs from neurodegeneration
through mechanisms involving α2-adrenergic receptor mediated survival
signal activation and up-regulation of endogenous neurotrophic factor
expression in the chronic ocular hypertensive rat retina.
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Affiliation(s)
- Hwa Sun Kim
- Department of Ophthalmology, College of Medicine, The Catholic University of Korea, Seoul, Korea
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211
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Liu X, Brandt CR, Rasmussen CA, Kaufman PL. Ocular drug delivery: Molecules, cells, and genes. Can J Ophthalmol 2007. [DOI: 10.3129/can.j.ophthalmol.i07-049] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
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212
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Levkovitch-Verbin H, Harizman N, Dardik R, Nisgav Y, Vander S, Melamed S. Regulation of cell death and survival pathways in experimental glaucoma. Exp Eye Res 2007; 85:250-8. [PMID: 17586494 DOI: 10.1016/j.exer.2007.04.011] [Citation(s) in RCA: 40] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/03/2006] [Revised: 04/20/2007] [Accepted: 04/25/2007] [Indexed: 10/23/2022]
Abstract
This study investigates cell death and survival pathways in experimental glaucoma using the translimbal photocoagulation laser model. Glaucoma was induced unilaterally in 79 Wistar rats and all eyes developed elevated intraocular pressure. The involvement of caspase-3, p-AKT and members of the MAP kinase pathway was evaluated by immunohistochemistry and Western blotting. We found that protein levels of caspase-3 were elevated from day 15 to day 30 (p<0.05). All investigated members of the MAP kinase pathway were significantly activated. P-SAPK/JNK activation began on day 2, reaching a 6-fold elevation by day 30 (p<0.05). The p-P38 level was elevated on days 2 and 8 (p<0.05), followed by a decrease to baseline on day 15. The level of p-ATF-2, the substrate of P38, was significantly elevated at all time points tested, up to day 30 (p<0.05). P-ERK was detected early (p<0.05) on day 1, returning to normal on day 15. The pro-survival protein p-Akt, a member of the PI3-kinase survival pathway, was also detected early on day 1 (p<0.05) returning to baseline on day 8 and remaining unchanged up to 64days. We conclude that retinal ganglion cell death in glaucoma involves activation, at different time points, of multiple pro-apoptotic pathways (the MAP kinase pathway and the caspase family) and pro-survival (PI-3 Kinase/ Akt and p-ERK).
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Affiliation(s)
- Hani Levkovitch-Verbin
- Sam Rothberg Ophthalmic Molecular Biology Laboratory, Goldschleger Eye Institute, Sheba Medical Center, Sackler Faculty of Medicine, Tel-Aviv University, Tel-Hashomer 52621, Israel.
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213
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214
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Nickells RW. From ocular hypertension to ganglion cell death: a theoretical sequence of events leading to glaucoma. Can J Ophthalmol 2007. [DOI: 10.3129/can.j.ophthalmol.i07-036] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/01/2022]
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215
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Greenberg KP, Geller SF, Schaffer DV, Flannery JG. Targeted transgene expression in muller glia of normal and diseased retinas using lentiviral vectors. Invest Ophthalmol Vis Sci 2007; 48:1844-52. [PMID: 17389520 PMCID: PMC1939809 DOI: 10.1167/iovs.05-1570] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/19/2022] Open
Abstract
PURPOSE Müller glia play crucial roles in retinal homeostasis and function. Genetic modification of Müller cells by viral gene delivery would be valuable for studies of their normal physiology and roles in retinal disease states. However, stable and efficient transgene expression in Müller cells after delivery of gene transfer vectors has remained elusive. Transcriptional and transductional targeting approaches were used to engineer recombinant HIV-1-based lentiviral (LV) vectors capable of highly efficient and sustained Müller cell transgene expression in healthy and diseased rodent retinas. METHODS Expression cassettes containing glia-specific promoters (CD44, glial fibrillary acidic protein, and vimentin) and an enhanced green fluorescent protein (eGFP) cDNA were cloned into LV backbones, which were packaged into infectious vector particles displaying either the vesicular stomatitis virus (VSV) or Ross River virus (RRV) envelope surface glycoproteins. Vectors were injected by intravitreal and subretinal approaches in wild type Sprague-Dawley (SD) and retinal degenerate S334Ter(+/-) transgenic rats aged 1 to 180 days. In vivo fluorescent fundus imaging and immunofluorescent confocal microscopy were used for comparison of expression efficiency, cell type specificity, and temporal expression characteristics. RESULTS The choice of viral pseudotype, regulatory promoter, and surgical delivery site each had a measurable effect on the level of eGFP transgene expression in Müller cells. The highest expression levels in SD retinas were attained with subretinal injection of VSV-G pseudotyped LV vectors containing the CD44 promoter. With these vectors, persistent eGFP expression in Müller glia was observed for more than 6 months, covering 25% to 30% of the retinal surface area after a single subretinal injection. Immunohistochemistry (alpha-glutamine synthetase) revealed that approximately 95% of the Müller cells were transduced in the region near the injection site. Delivery of these viral vectors and subsequent Müller cell eGFP expression had no negative impact on visual function, as assessed by electroretinography (ERG). CONCLUSIONS Pseudotyped LV vectors containing glia-specific promoters efficiently transduce and direct sustained transgene expression in retinal Müller glia. Vectors of this type will be useful for experimental treatment of retinal disease, as well as for physiological and developmental investigations of the retina.
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Affiliation(s)
- Kenneth P. Greenberg
- Department of Vision Science, University of California, Berkeley, California
- Helen Wills Neuroscience Institute, University of California, Berkeley, California
| | - Scott F. Geller
- Department of Vision Science, University of California, Berkeley, California
- Helen Wills Neuroscience Institute, University of California, Berkeley, California
| | - David V. Schaffer
- Helen Wills Neuroscience Institute, University of California, Berkeley, California
- Department of Chemical Engineering, University of California, Berkeley, California
| | - John G. Flannery
- Department of Vision Science, University of California, Berkeley, California
- Helen Wills Neuroscience Institute, University of California, Berkeley, California
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216
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Allocca M, Tessitore A, Cotugno G, Auricchio A. AAV-mediated gene transfer for retinal diseases. Expert Opin Biol Ther 2007; 6:1279-94. [PMID: 17223737 DOI: 10.1517/14712598.6.12.1279] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Vectors based on the adeno-associated virus (rAAV) are able to transduce the retina of animal models, including non-human primates, for a long-term period, safely and at sustained levels. The ability of the various rAAV serotypes to transduce retinal target cells has been exploited to successfully transfer genes to photoreceptors, retinal pigment epithelium and the inner retina, which are affected in many inherited and non-inherited blinding diseases. rAAV-mediated, constitutive and regulated gene expression at therapeutic levels has been achieved in the retina of animal models, thus providing proof-of-principle of gene therapy efficacy and safety in models of dominant and recessive retinal disorders. In addition, gene transfer of molecules with either neurotrophic or antiangiogenic properties provides useful alternatives to the classic gene replacement for treatment of both mendelian and complex traits affecting the retina. Years of successful rAAV-mediated gene transfer to the retina have resulted in restoration of vision in dogs affected with congenital blindness. This has paved the way to the first attempts at treating inherited retinal diseases in humans with rAAV. Although the results of rAAV clinical trials for non-retinal diseases give a warning that the outcome of viral-mediated gene transfer in humans may be different from that predicted based on results in other species, the immune privilege of the retina combined with the versatility of rAAV serotypes may ultimately provide the first successful treatment of human inherited diseases using rAAV.
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Affiliation(s)
- Mariacarmela Allocca
- Telethon Institute of Genetics and Medicine (TIGEM), Via P. Castellino, 111. 80131 Napoli, Italy.
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217
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Conforti L, Adalbert R, Coleman MP. Neuronal death: where does the end begin? Trends Neurosci 2007; 30:159-66. [PMID: 17339056 DOI: 10.1016/j.tins.2007.02.004] [Citation(s) in RCA: 122] [Impact Index Per Article: 7.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/21/2006] [Revised: 01/22/2007] [Accepted: 02/19/2007] [Indexed: 11/21/2022]
Abstract
Neurodegenerative disorders involve death of cell bodies, axons, dendrites and synapses, but it is surprisingly difficult to determine the spatiotemporal sequence of events and the causal relationships among these events. Neuronal compartments often crucially depend upon one another for survival, and molecular defects in one compartment can trigger cellular degeneration in distant parts of the neuron. Here, we consider the novel approaches used to understand these biologically complex and technically challenging questions in amyotrophic lateral sclerosis, spinal muscular atrophy, glaucoma, Alzheimer's disease, Parkinson's disease and polyglutamine disorders. We conclude that there is partial understanding of what degenerates first and why, but that controversy remains the rule not the exception. Finally, we highlight strategies for resolving these fundamental issues.
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Affiliation(s)
- Laura Conforti
- The Babraham Institute, Babraham, Cambridge CB22 3AT, UK
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218
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Rao VR, Krishnamoorthy RR, Yorio T. Endothelin-1, endothelin A and B receptor expression and their pharmacological properties in GFAP negative human lamina cribrosa cells. Exp Eye Res 2007; 84:1115-24. [PMID: 17433294 DOI: 10.1016/j.exer.2007.02.010] [Citation(s) in RCA: 20] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2006] [Revised: 02/02/2007] [Accepted: 02/12/2007] [Indexed: 11/18/2022]
Abstract
Primary open angle glaucoma (POAG) is a progressive optic neuropathy, characterized, in part by extensive extra cellular matrix remodeling and collapse of the lamina cribrosa (LC). Endothelin-1 (ET-1), a potent vasoactive peptide and its receptors, endothelin receptor A (ET(A)) and endothelin receptor B (ET(B)), have been implicated in glaucomatous optic neuropathy. In this study we examined the expression of ET-1 and its receptors in GFAP negative LC cells. RT-PCR analysis revealed that LC cells express both ET(A), ET(B) receptors and prepro- ET-1, the primary gene transcript of ET-1. A dose-dependent increase in intra-cellular calcium concentrations was observed in the presence of 1, 10 and 100nM ET-1. Increased intracellular calcium concentrations were blocked by the ET(A) selective antagonist BQ610 but not by the ET(B) specific antagonist BQ788. Desensitization to ET(A)-mediated increase in intracellular calcium was observed in LC cells following pre-treatment with ET-1 for 24h. Western blot analysis of LC cells treated with ET-1 for 24h revealed a decreased expression of ET(A) receptor protein at 1, 10 and 100nM concentrations, while a dose dependent increase in the ET(B) receptor was observed with a significant increase at 100nM. Quantitative PCR showed a dose-dependent decrease in ET(A) receptor mRNA levels and an increase in the mRNA levels of ET(B) receptors. A Griess colorimetric assay was used to measure the NO released from LC cells and ET-1 induced a dose-dependent increase in NO release which was significant at 100nM concentration. ET-1 induced NO release was significantly blocked by BQ788, an ET(B) selective antagonist, and as well as BQ610, an ET(A) selective antagonist. These results suggested that human lamina cribrosa cells expressed functional ET(A) and ET(B) receptors and their expression and function was altered in response to prolong exposure to ET-1. This may have an implication in the normal physiology of LC cells and in POAG subjects where elevated levels of ET-1 could impact LC function.
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Affiliation(s)
- Vidhya R Rao
- Department of Pharmacology and Neuroscience, University of North Texas Health Science Center, 3500 Camp Bowie Boulevard, Fort Worth, TX 76107, USA
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219
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Abstract
The Retinal Degeneration Slow (Rds) protein is required by photoreceptors for proper formation of the specialized outer segment organelle. Human mutations in Rds cause a multitude of blinding diseases such as retinitis pigmentosa and macular degeneration. In recent years, the use of animal models and biochemical approaches has provided evidence towards the precise function of Rds and its role in the pathogenesis of human disease. This review addresses the current understanding of the role of Rds in photoreceptor outer segment morphogenesis and provides insight into the design of therapeutic strategies to treat Rds-associated retinal diseases.
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Affiliation(s)
- Rafal Farjo
- Department of Cell Biology, University of Oklahoma Health Sciences Center, Oklahoma City, OK 73104, USA
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220
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Azadi S, Johnson LE, Paquet-Durand F, Perez MTR, Zhang Y, Ekström PAR, van Veen T. CNTF+BDNF treatment and neuroprotective pathways in the rd1 mouse retina. Brain Res 2007; 1129:116-29. [PMID: 17156753 DOI: 10.1016/j.brainres.2006.10.031] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/22/2006] [Revised: 10/05/2006] [Accepted: 10/06/2006] [Indexed: 11/22/2022]
Abstract
The rd1 mouse is a relevant model for studying the mechanisms of photoreceptor degeneration in retinitis pigmentosa. Treatment with ciliary neurotrophic factor (CNTF) in combination with brain derived neurotrophic factor (BDNF) is known to rescue photoreceptors in cultured rd1 retinal explants. To shed light on the underlying mechanisms, we studied the effects of 9 days (starting at postnatal day 2) in vitro CNTF+BDNF treatment on the endogenous production of CNTF, BDNF, fibroblast growth factor 2 (FGF2), or the activation of extracellular signal-regulated kinase (ERK), Akt and cAMP-response-element-binding protein (CREB) in retinal explants. In rd1 explants, CNTF+BDNF decreased the number of TUNEL-positive photoreceptors. The treatment also increased endogenous rd1 levels of CNTF and BDNF, but lowered the level of FGF2 expression in rd1 explants. When wild-type explants were treated, endogenous CNTF was similarly increased, while BDNF and FGF2 levels remained unaffected. In addition, treatment of rd1 retinas strongly increased the phosphorylation of ERK, Akt and CREB. In treated wild-type explants, the same parameters were either unchanged (ERK) or decreased (Akt and CREB). The results suggest a role for Akt, ERK and CREB in conveying the neuroprotective effect of CNTF+BDNF treatment in rd1 retinal explants.
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Affiliation(s)
- Seifollah Azadi
- Department of Ophthalmology, University of Lund, BMC-B13, SE-221 84 LUND, Sweden
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221
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Farjo R, Skaggs J, Quiambao AB, Cooper MJ, Naash MI. Efficient non-viral ocular gene transfer with compacted DNA nanoparticles. PLoS One 2006; 1:e38. [PMID: 17183666 PMCID: PMC1762345 DOI: 10.1371/journal.pone.0000038] [Citation(s) in RCA: 151] [Impact Index Per Article: 8.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/19/2006] [Accepted: 10/10/2006] [Indexed: 11/18/2022] Open
Abstract
Background The eye is an excellent candidate for gene therapy as it is immune privileged and much of the disease-causing genetics are well understood. Towards this goal, we evaluated the efficiency of compacted DNA nanoparticles as a system for non-viral gene transfer to ocular tissues. The compacted DNA nanoparticles examined here have been shown to be safe and effective in a human clinical trial, have no theoretical limitation on plasmid size, do not provoke immune responses, and can be highly concentrated. Methods and Findings Here we show that these nanoparticles can be targeted to different tissues within the eye by varying the site of injection. Almost all cell types of the eye were capable of transfection by the nanoparticle and produced robust levels of gene expression that were dose-dependent. Most impressively, subretinal delivery of these nanoparticles transfected nearly all of the photoreceptor population and produced expression levels almost equal to that of rod opsin, the highest expressed gene in the retina. Conclusions As no deleterious effects on retinal function were observed, this treatment strategy appears to be clinically viable and provides a highly efficient non-viral technology to safely deliver and express nucleic acids in the retina and other ocular tissues.
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Affiliation(s)
- Rafal Farjo
- Department of Cell Biology, University of Oklahoma Health Sciences CenterOklahoma City, Oklahoma, United States of America
| | - Jeff Skaggs
- Department of Cell Biology, University of Oklahoma Health Sciences CenterOklahoma City, Oklahoma, United States of America
| | - Alexander B. Quiambao
- Department of Cell Biology, University of Oklahoma Health Sciences CenterOklahoma City, Oklahoma, United States of America
| | - Mark J. Cooper
- Copernicus Therapeutics, Inc.Cleveland, Ohio, United States of America
| | - Muna I. Naash
- Department of Cell Biology, University of Oklahoma Health Sciences CenterOklahoma City, Oklahoma, United States of America
- * To whom correspondence should be addressed. E-mail:
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222
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Pease ME, Hammond JC, Quigley HA. Manometric Calibration and Comparison of TonoLab and TonoPen Tonometers in Rats With Experimental Glaucoma and in Normal Mice. J Glaucoma 2006; 15:512-9. [PMID: 17106364 DOI: 10.1097/01.ijg.0000212276.57853.19] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/26/2022]
Abstract
PURPOSE To compare the TonoPen and TonoLab tonometers to each other and to manometrically set intraocular pressure (IOP) in the eyes of normal mice, normal rats, and rats with chronic IOP elevation. METHODS The measurement of IOP by the TonoPen and TonoLab tonometers was made in 21 normal rat eyes, 10 normal mouse eyes, and 16 rats that had either 2 or 4-week experimental glaucoma. IOP was varied from 10 to 50 mm Hg in steps of 10 mm Hg under conditions in which the eye was either open or closed to the reservoir controlling IOP. RESULTS In normal rat eyes, TonoPen overestimated manometric IOP at 10 mm Hg and underestimated it by up to 6 mm Hg at higher IOP, whereas the TonoLab matched set IOP within 1 mm Hg. In glaucoma rat eyes, the TonoLab accurately reflected manometric IOP under open stopcock conditions (linear regression: y = 0.99x -0.62, R = 0.98), whereas in the closed stopcock condition, IOP measured lower at the higher IOP levels (P = 0.0059, paired t test). In uncannulated rat glaucoma eyes, the tonometer used first gave higher IOP [paired t test, P = 0.015 (TonoLab first); P = 0.005 (TonoPen first)]. In normal mouse eyes under the open stopcock condition, the TonoLab nearly matched manometric IOP (linear regression: y = 0.98x + 1.57, R = 0.98). CONCLUSIONS In mouse and rat eyes, including rats with chronic IOP elevation, the TonoLab accurately reflected manometrically set IOP in an efficient manner.
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Affiliation(s)
- Mary E Pease
- Glaucoma Service, Wilmer Ophthalmological Institute, Johns Hopkins University School of Medicine, Baltimore, MD 21287, USA.
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223
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Harvey AR, Hu Y, Leaver SG, Mellough CB, Park K, Verhaagen J, Plant GW, Cui Q. Gene therapy and transplantation in CNS repair: The visual system. Prog Retin Eye Res 2006; 25:449-89. [PMID: 16963308 DOI: 10.1016/j.preteyeres.2006.07.002] [Citation(s) in RCA: 70] [Impact Index Per Article: 3.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/09/2023]
Abstract
Normal visual function in humans is compromised by a range of inherited and acquired degenerative conditions, many of which affect photoreceptors and/or retinal pigment epithelium. As a consequence the majority of experimental gene- and cell-based therapies are aimed at rescuing or replacing these cells. We provide a brief overview of these studies, but the major focus of this review is on the inner retina, in particular how gene therapy and transplantation can improve the viability and regenerative capacity of retinal ganglion cells (RGCs). Such studies are relevant to the development of new treatments for ocular conditions that cause RGC loss or dysfunction, for example glaucoma, diabetes, ischaemia, and various inflammatory and neurodegenerative diseases. However, RGCs and associated central visual pathways also serve as an excellent experimental model of the adult central nervous system (CNS) in which it is possible to study the molecular and cellular mechanisms associated with neuroprotection and axonal regeneration after neurotrauma. In this review we present the current state of knowledge pertaining to RGC responses to injury, neurotrophic and gene therapy strategies aimed at promoting RGC survival, and how best to promote the regeneration of RGC axons after optic nerve or optic tract injury. We also describe transplantation methods being used in attempts to replace lost RGCs or encourage the regrowth of RGC axons back into visual centres in the brain via peripheral nerve bridges. Cooperative approaches including novel combinations of transplantation, gene therapy and pharmacotherapy are discussed. Finally, we consider a number of caveats and future directions, such as problems associated with compensatory sprouting and the reformation of visuotopic maps, the need to develop efficient, regulatable viral vectors, and the need to develop different but sequential strategies that target the cell body and/or the growth cone at appropriate times during the repair process.
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Affiliation(s)
- Alan R Harvey
- School of Anatomy and Human Biology, The University of Western Australia, Crawley, WA 6009, Australia
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224
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Min SH, Molday LL, Seeliger MW, Dinculescu A, Timmers AM, Janssen A, Tonagel F, Tanimoto N, Weber BHF, Molday RS, Hauswirth WW. Prolonged recovery of retinal structure/function after gene therapy in an Rs1h-deficient mouse model of x-linked juvenile retinoschisis. Mol Ther 2006; 12:644-51. [PMID: 16027044 DOI: 10.1016/j.ymthe.2005.06.002] [Citation(s) in RCA: 131] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/16/2005] [Revised: 06/03/2005] [Accepted: 06/06/2005] [Indexed: 11/27/2022] Open
Abstract
X-linked juvenile retinoschisis (RS) is a common cause of juvenile macular degeneration in males. RS is characterized by cystic spoke-wheel-like maculopathy, peripheral schisis, and a negative (b-wave more reduced than a-wave) electroretinogram (ERG). These symptoms are due to mutations in the RS1 gene in Xp22.2 leading to loss of functional protein. No medical treatment is currently available. We show here that in an Rs1h-deficient mouse model of human RS, delivery of the human RS1 cDNA with an AAV vector restored expression of retinoschisin to both photoreceptors and the inner retina essentially identical to that seen in wild-type mice. More importantly, unlike an earlier study with a different AAV vector and promoter, this work shows for the first time that therapeutic gene delivery using a highly specific AAV5-opsin promoter vector leads to progressive and significant improvement in both retinal function (ERG) and morphology, with preservation of photoreceptor cells that, without treatment, progressively degenerate.
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Affiliation(s)
- Seok H Min
- Department of Ophthalmology, University of Florida College of Medicine, Gainesville, 32610, USA.
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225
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Martin KRG, Quigley HA, Valenta D, Kielczewski J, Pease ME. Optic nerve dynein motor protein distribution changes with intraocular pressure elevation in a rat model of glaucoma. Exp Eye Res 2006; 83:255-62. [PMID: 16546168 DOI: 10.1016/j.exer.2005.11.025] [Citation(s) in RCA: 88] [Impact Index Per Article: 4.9] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2005] [Revised: 06/26/2005] [Accepted: 11/30/2005] [Indexed: 10/24/2022]
Abstract
Acute intraocular pressure (IOP) elevation causes accumulation of retrogradely-transported brain derived neurotrophic factor and its receptor at the optic nerve head (ONH) in rats and monkeys. Obstruction of axonal transport may therefore be involved in glaucoma pathogenesis, but it is unknown if obstruction is specific to certain transported factors or represents a generalized failure of retrograde axonal transport. The dynein motor complex mediates retrograde axonal transport in retinal ganglion cells (RGC). Our hypothesis was that elevated IOP interferes with dynein-mediated axonal transport. We studied the distribution of dynein subunits in the retina and optic nerve after acute and chronic experimental IOP elevation in the rat. IOP was elevated unilaterally in 54 rats. Dynein subunit distribution was compared in treated and control eyes by immunohistochemistry and Western blotting at 1 day (n=12), 3 days (n=4), 1 week (n=15), 2 weeks (n=12) and 4 weeks (n=11). For immunohistochemistry, sections through the ONH were probed with an anti-dynein heavy chain (HC) antibody and graded semi-quantitatively by masked observers. Other freshly enucleated eyes were microdissected for separate Western blot quantification of dynein intermediate complex (IC) in myelinated and unmyelinated optic nerve, ONH and retina. Immunohistochemistry showed accumulation of dynein HC at the ONH in IOP elevation eyes compared to controls (P<0.001, Wilcoxon paired sign-rank test, n=29). ONH dynein IC was elevated by 46.5% in chronic IOP elevation eyes compared to controls by Western blotting (P<0.001, 95% CI=25.9% to 67.8%, n=17). The maximum increase in ONH dynein IC was 78.7% after 1 week (P<0.05, n=5), but significant increases were also detected after 4 h and 4 weeks of IOP elevation (P<0.05, n=4 rats per group). Total retinal dynein IC was increased by 8.7% in chronic IOP elevation eyes compared to controls (P<0.03, 95% CI 1.4% to 16.1%, n=24). In the retina, IOP elevation particularly affected the 72 kD subunit of dynein IC, which was 100.7% higher in chronic IOP elevation eyes compared to controls (P<0.00001, 95% CI 71.0% to 130.4%, n=21). Dynein IC changes in myelinated and unmyelinated optic nerve were not significant (P>0.05). We conclude that dynein accumulates at the ONH with experimental IOP elevation in the rat, supporting the hypothesis that disrupted axonal transport in RGC may be involved in the pathogenesis of glaucoma. The effect of IOP elevation on other motor proteins deserves further investigation in the future.
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Affiliation(s)
- Keith R G Martin
- Glaucoma Research Laboratory, Wilmer Eye Institute, Johns Hopkins University, Baltimore, MD, USA.
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226
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Borrás T, Xue W, Choi VW, Bartlett JS, Li G, Samulski RJ, Chisolm SS. Mechanisms of AAV transduction in glaucoma-associated human trabecular meshwork cells. J Gene Med 2006; 8:589-602. [PMID: 16506246 DOI: 10.1002/jgm.886] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/09/2022] Open
Abstract
BACKGROUND Glaucoma is a chronic eye disease which leads to irreversible blindness. The trabecular meshwork tissue controls intraocular pressure (IOP), which is the major risk factor for glaucoma. Gene therapy treatment of chronic diseases requires the use of long-term expression, low toxicity and lack of immune response vectors. Adeno-associated viruses (AAV) possess these characteristics but have been unable to transduce the trabecular meshwork. Because of the importance of regulating elevated IOP by long-term gene therapy, we investigated mechanisms of AAV transduction to the human trabecular meshwork (TM). METHODS Primary human trabecular meshwork cells (HTM) and perfused organ cultures were infected with rAAV2-GFP, RGD-pseudotyped rAAV2-GFP alone, or combined with recombinant DeltaE1/E3 adenoviruses. Intracellular rAAV2 DNA and RNA were measured by relative quantitative and real-time TaqMan polymerase chain reaction (PCR). Host transcriptome was analyzed using high-density oligonucleotide microarrays. One transduction mechanism was tested using self-complementary AAV (scAAV). RESULTS The dramatic transduction enhancement obtained upon co-infection of rAAV2 with DeltaE1/E3 adenoviruses provides insights into transduction mechanisms in the HTM. Even if not transduced, rAAV2 enters TM cells. GeneChip analysis showed significant changes in host genes involved in cell cycle and DNA replication. Consequently, scAAV-GFP transduction was highly efficient. Other transduction-enhancement genes included coxsackie adenovirus receptor (CAR) and genes relevant to trabecular meshwork function. CONCLUSIONS The rate-limiting step of AAV transduction was not viral entry failure but, at least in part, host downregulation of DNA replication. Additional specific host genes might be involved. Our study revealed genes and mechanisms which led for the first time to efficient AAV transduction of the HTM.
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Affiliation(s)
- Teresa Borrás
- Department of Ophthalmology, University of North Carolina School of Medicine, 103 Mason Farm Road, Chapel Hill, NC 27599, USA.
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227
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Abstract
The eye has unique advantages as a target organ for gene therapy of both inherited and acquired ocular disorders and offers a valuable model system for gene therapy. The eye is readily accessible to phenotypic examination and investigation of therapeutic effects in vivo by fundus imaging and electrophysiological techniques. Considerable progress has been made in the development of gene replacement therapies for retinal degenerations resulting from gene defects in photoreceptor cells (rds, RPGRIP, RS-1) and in retinal pigment epithelial cells (MerTK, RPE65, OA1) using recombinant adeno-associated virus and lentivirus-based vectors. Gene therapy also offers a potentially powerful approach to the treatment of complex acquired disorders such as those involving angiogenesis, inflammation and degeneration, by the targeted sustained intraocular delivery of therapeutic proteins. Proposals for clinical trials of gene therapy for early-onset retinal degeneration owing to defects in the gene encoding the visual cycle protein RPE65 have recently received ethical approval.
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Affiliation(s)
- J W B Bainbridge
- Division of Molecular Therapy, Institute of Ophthalmology, University College London, London, UK
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228
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MacLaren RE, Buch PK, Smith AJ, Balaggan KS, MacNeil A, Taylor JS, Osborne NN, Ali RR. CNTF gene transfer protects ganglion cells in rat retinae undergoing focal injury and branch vessel occlusion. Exp Eye Res 2006; 83:1118-27. [PMID: 16831422 DOI: 10.1016/j.exer.2006.05.019] [Citation(s) in RCA: 28] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/09/2005] [Revised: 04/20/2006] [Accepted: 05/26/2006] [Indexed: 11/29/2022]
Abstract
Ciliary neurotrophic factor (CNTF) has been shown to protect ganglion cells in a variety of acute ischaemia models. Here we assess the efficacy of local CNTF gene transfer in protecting retinal ganglion cells when there is focal ischaemia combined with interruption of axoplasmic flow. This dual injury may be more representative of the pathological mechanisms operating in acute retinal diseases, such as vascular events acting at the optic nerve head. Fourteen rats received an intravitreal injection of an adeno-associated viral (AAV) vector expressing a secretable form of CNTF into the right eye and a control vector into the left eye. Three weeks later, each rat underwent a symmetrical small vertical 2mm standardised retinal crush injury approximately 2mm temporal to the optic disc. The injury also occluded the temporal retinal arteriole so that the axon crush was combined with an acute retinal infarction visible on fundoscopy. Changes in the damaged sector were compared histologically four weeks after injury and ganglion cell survival was estimated by comparing cell counts on retinal flat-mounts immunostained with RT-97 antibody. This mode of injury led to a profound loss of both the inner nuclear and ganglion cell layers, but was limited to the lesioned sector. In AAV.CNTF-treated eyes approximately 12% of ganglion cells survived compared with approximately 2% in control eyes (p=0.01). The scotopic electroretinogram (ERG), however, was reduced to about 50% in AAV.CNTF-treated eyes, both before and after injury. We therefore show that CNTF gene transfer confers neuroprotection to ganglion cells undergoing an acute ischaemic injury combined with interruption of axoplasmic flow. This approach may be relevant to optic nerve trauma and a variety of retinal vascular diseases that lead to swelling of the optic nerve head, provided CNTF can be delivered in a way that does not significantly suppress retinal function.
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Affiliation(s)
- Robert E MacLaren
- Division of Molecular Therapy, Institute of Ophthalmology, University College London, London EC1V 9EL, UK.
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229
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Ben Simon GJ, Hovda DA, Harris NG, Gomez-Pinilla F, Goldberg RA. Traumatic Brain Injury Induced Neuroprotection of Retinal Ganglion Cells to Optic Nerve Crush. J Neurotrauma 2006; 23:1072-82. [PMID: 16866620 DOI: 10.1089/neu.2006.23.1072] [Citation(s) in RCA: 10] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/14/2022] Open
Abstract
Optic nerve crush injury leads to death of retinal ganglion cells (RGCs), both as a direct result of the primary injury and via secondary degeneration induced by neurotoxins secreted by dying RGCs. Studies have shown that, if optic nerve crush is preceded by an unrelated injury to another part of the central nervous system, for example, the spinal cord, the ensuing T cell-mediated protective autoimmunity results in a significant increase in RGC survival. In this study, we used the controlled cortical impact paradigm to induce unilateral traumatic brain injury (TBI) in rats at different times before they were contralaterally subjected to a mild optic nerve crush. Survival of RGCs, assessed 2 weeks after crush injury, was significantly increased when the crush was inflicted 11 days after TBI, but not when the two injuries were concomitant. The beneficial effect was unaffected by injection of low-dose methylprednisolone MP (1 mg/kg), but was inhibited after a high-dose injection (30 mg/kg). Brain-derived neurotrophic factor (BDNF) mRNA, assayed at intervals after TBI, was increased in the retina ipsilateral to TBI but decreased in the contralateral retina. BDNF peaked 1 day after TBI, decreased on day 11, and rose again on day 21. It thus seems that brain injury sustained a certain time before optic nerve injury has a protective effect on RGC survival. This neuroprotective effect, which appears unrelated to retinal BDNF, is inhibited by high-dose MP, commonly used clinically to treat traumatic optic neuropathy.
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Affiliation(s)
- Guy J Ben Simon
- Jules Stein Eye Institute and Department of Ophthalmology, David Geffen School of Medicine at UCLA, Los Angeles, California, USA.
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230
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Li C, Bowles DE, van Dyke T, Samulski RJ. Adeno-associated virus vectors: potential applications for cancer gene therapy. Cancer Gene Ther 2006; 12:913-25. [PMID: 15962012 PMCID: PMC1361306 DOI: 10.1038/sj.cgt.7700876] [Citation(s) in RCA: 82] [Impact Index Per Article: 4.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/03/2023]
Abstract
Augmenting cancer treatment by protein and gene delivery continues to gain momentum based on success in animal models. The primary hurdle of fully exploiting the arsenal of molecular targets and therapeutic transgenes continues to be efficient delivery. Vectors based on adeno-associated virus (AAV) are of particular interest as they are capable of inducing transgene expression in a broad range of tissues for a relatively long time without stimulation of a cell-mediated immune response. Perhaps the most important attribute of AAV vectors is their safety profile in phase I clinical trials ranging from CF to Parkinson's disease. The utility of AAV vectors as a gene delivery agent in cancer therapy is showing promise in preclinical studies. In this review, we will focus on the basic biology of AAV as well as recent progress in the use of this vector in cancer gene therapy.
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Affiliation(s)
- Chengwen Li
- Gene Therapy Center, University of North Carolina (UNC) at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Dawn E Bowles
- Gene Therapy Center, University of North Carolina (UNC) at Chapel Hill, Chapel Hill, North Carolina 27599, USA
| | - Terry van Dyke
- Department of Biochemistry and Biophysics, University of North Carolina (UNC) at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Lineberger Comprehensive Cancer Center, University of North Carolina (UNC) at Chapel Hill, Chapel Hill, North Carolina 27599, USA; and
| | - Richard Jude Samulski
- Gene Therapy Center, University of North Carolina (UNC) at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Department of Pharmacology, University of North Carolina (UNC) at Chapel Hill, Chapel Hill, North Carolina 27599, USA
- Address correspondence and reprint requests to: Professor Richard Jude Samulski/Terry van Dyke, Gene Therapy Center, University of North Carolina (UNC) at Chapel Hill, CB#7352, Chapel Hill, NC27599, USA. E-mails: or
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231
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Bi A, Cui J, Ma YP, Olshevskaya E, Pu M, Dizhoor AM, Pan ZH. Ectopic expression of a microbial-type rhodopsin restores visual responses in mice with photoreceptor degeneration. Neuron 2006; 50:23-33. [PMID: 16600853 PMCID: PMC1459045 DOI: 10.1016/j.neuron.2006.02.026] [Citation(s) in RCA: 512] [Impact Index Per Article: 28.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/29/2005] [Revised: 01/12/2006] [Accepted: 02/23/2006] [Indexed: 11/21/2022]
Abstract
The death of photoreceptor cells caused by retinal degenerative diseases often results in a complete loss of retinal responses to light. We explore the feasibility of converting inner retinal neurons to photosensitive cells as a possible strategy for imparting light sensitivity to retinas lacking rods and cones. Using delivery by an adeno-associated viral vector, here, we show that long-term expression of a microbial-type rhodopsin, channelrhodopsin-2 (ChR2), can be achieved in rodent inner retinal neurons in vivo. Furthermore, we demonstrate that expression of ChR2 in surviving inner retinal neurons of a mouse with photoreceptor degeneration can restore the ability of the retina to encode light signals and transmit the light signals to the visual cortex. Thus, expression of microbial-type channelrhodopsins, such as ChR2, in surviving inner retinal neurons is a potential strategy for the restoration of vision after rod and cone degeneration.
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Affiliation(s)
- Anding Bi
- Department of Anatomy and Cell Biology, Wayne State University School of Medicine, Detroit, Michigan 48201, USA
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232
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Abstract
During the last 30 years, the definition of glaucoma as been revised to eliminate the inclusion of intraocular pressure. Open angle glaucoma is the second leading cause of blindness in the world, but the proportion of those with the disease who become blind is low. Diagnostic methods for glaucoma need improvement. The pathogenetic steps to loss of neurons in glaucoma are increasingly understood and non-pressure lowering therapies are on the horizon.
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Affiliation(s)
- H A Quigley
- Wilmer Ophthalmological Institute, Johns Hopkins Hospital, Baltimore, MD, USA.
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233
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Leaver SG, Cui Q, Plant GW, Arulpragasam A, Hisheh S, Verhaagen J, Harvey AR. AAV-mediated expression of CNTF promotes long-term survival and regeneration of adult rat retinal ganglion cells. Gene Ther 2006; 13:1328-41. [PMID: 16708079 DOI: 10.1038/sj.gt.3302791] [Citation(s) in RCA: 198] [Impact Index Per Article: 11.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/05/2023]
Abstract
We compared the effects of intravitreal injection of bi-cistronic adeno-associated viral (AAV-2) vectors encoding enhanced green fluorescent protein (GFP) and either ciliary neurotrophic factor (CNTF), brain-derived neurotrophic factor (BDNF) or growth-associated protein-43 (GAP43) on adult retinal ganglion cell (RGC) survival and regeneration following (i) optic nerve (ON) crush or (ii) after ON cut and attachment of a peripheral nerve (PN). At 7 weeks after ON crush, quantification of betaIII-tubulin immunostaining revealed that, compared to AAV-GFP controls, RGC survival was not enhanced by AAV-GAP43-GFP but was increased in AAV-CNTF-GFP (mean RGCs/retina: 17 450+/-358 s.e.m.) and AAV-BDNF-GFP injected eyes (10 200+/-4064 RGCs/retina). Consistent with increased RGC viability in AAV-CNTF-GFP and AAV-BDNF-GFP injected eyes, these animals possessed many betaIII-tubulin- and GFP-positive fibres proximal to the ON crush. However, only in the AAV-CNTF-GFP group were regenerating RGC axons seen in distal ON (1135+/-367 axons/nerve, 0.5 mm post-crush), some reaching the optic chiasm. RGCs were immunoreactive for CNTF and quantitative RT-PCR revealed a substantial increase in CNTF mRNA expression in retinas transduced with AAV-CNTF-GFP. The combination of AAV-CNTF-GFP transduction of RGCs with autologous PN-ON transplantation resulted in even greater RGC survival and regeneration. At 7 weeks after PN transplantation there were 27 954 (+/-2833) surviving RGCs/retina, about 25% of the adult RGC population. Of these, 13 352 (+/-1868) RGCs/retina were retrogradely labelled after fluorogold injections into PN grafts. In summary, AAV-mediated expression of CNTF promotes long-term survival and regeneration of injured adult RGCs, effects that are substantially enhanced by combining gene and cell-based therapies/interventions.
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Affiliation(s)
- S G Leaver
- School of Anatomy and Human Biology, The University of Western Australia, Western Australia, Australia
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234
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Yu S, Tanabe T, Yoshimura N. A rat model of glaucoma induced by episcleral vein ligation. Exp Eye Res 2006; 83:758-70. [PMID: 16707124 DOI: 10.1016/j.exer.2006.03.014] [Citation(s) in RCA: 55] [Impact Index Per Article: 3.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/10/2005] [Revised: 02/20/2006] [Accepted: 03/21/2006] [Indexed: 10/24/2022]
Abstract
To establish a reliable animal model of glaucoma, we examined if episcleral vein ligation in rat eyes can induce intraocular pressure (IOP) elevation and concomitant characteristic morphological features of glaucoma. IOP elevation was detected on the next day (30.1+/-4.4 mmHg: operated eyes; 21.0+/-1.8 mmHg: control eyes) and persisted at least 7 months after the procedure (24.5+/-2.3 mmHg: operated eyes; 19.7+/-1.9 mmHg: control eyes). These results suggest that episcleral vein ligation can induce very mild IOP elevation immediately after the operation, which can last over several months. Furthermore, it appears there was little variability in the patterns of IOP elevation among the individual eyes treated with episcleral vein ligation. Morphological changes were detected selectively in the retinal ganglion cell (RGC) layer and optic disc excavation was evident in the late stage of chronic IOP elevation. RGCs were selectively lost by apoptotic death. The number of RGCs was reduced by 18% at 12 weeks and eventually by 35% at 8 months postoperatively. Müller cells downregulated the expression of p27Kip1 and appeared to be partially in a reactive state even at the advanced stages of glaucoma. The expression of basic fibroblast growth factor and ciliary neurotrophic factor, which are neurotrophic factors implicated in the control of cell survivals and neuroprotection, significantly declined at the advanced stages. Taken altogether, these observations indicate that the episcleral vein ligation model based on the simple ligation procedure reproducibly provides a reliable glaucoma model and contributes to give insights into the underlying molecular and cellular bases of human glaucoma and to devise the new medication upon the disease.
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Affiliation(s)
- Saiyuu Yu
- Department of Ophthalmology and Visual Sciences, Graduate School of Medicine, Kyoto University, 54 Kyoto 606-8507, Japan
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235
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Yu S, Tanabe T, Dezawa M, Ishikawa H, Yoshimura N. Effects of bone marrow stromal cell injection in an experimental glaucoma model. Biochem Biophys Res Commun 2006; 344:1071-9. [PMID: 16643846 DOI: 10.1016/j.bbrc.2006.03.231] [Citation(s) in RCA: 85] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/16/2006] [Accepted: 03/28/2006] [Indexed: 12/18/2022]
Abstract
We investigated if bone marrow stromal cells (BMSCs) transplanted into the vitreous body of a glaucoma model eye could be integrated in the host retina and also whether they could rescue the retinal ganglion cells (RGCs) from death induced by the elevated intraocular pressure. Glaucoma was induced in the right eye of adult Wistar rats by ligating the episcleral veins. The GFP-expressing BMSCs (GFP-BMSCs) were injected into the vitreous body of both the control and the glaucomatous eyes. After transplantation, GFP-BMSCs were mostly present along with the inner limiting membrane and only a few cells were integrated into the ganglion cell layer. At 2 or 4 weeks after transplantation, GFP-BMSCs were observed to express various trophic factors. The BMSCs injected glaucoma model eyes showed less reduction in the number of RGCs compared to the glaucomatous eyes with PBS injection. This study suggests that BMSC transplantation may be worthy as a neuroprotective tool to treat glaucoma.
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Affiliation(s)
- Saiyuu Yu
- Department of Ophthalmology and Visual Sciences, Graduate School of Medicine, Kyoto University, Kyoto, Japan
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236
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Deng WT, Yan Z, Dinculescu A, Pang J, Teusner JT, Cortez NG, Berns KI, Hauswirth WW. Adeno-associated virus-mediated expression of vascular endothelial growth factor peptides inhibits retinal neovascularization in a mouse model of oxygen-induced retinopathy. Hum Gene Ther 2006; 16:1247-54. [PMID: 16259558 DOI: 10.1089/hum.2005.16.1247] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/13/2023] Open
Abstract
Vascular endothelial growth factor (VEGF) has been demonstrated to be a key stimulator of retinal neovascularization (NV), the most common cause of severe and progressive vision loss. In this study, we used a mouse model of oxygen-induced retinopathy (OIR) to explore the potential of gene expression and secretion of short VEGF peptides as a treatment. Peptide-encoding fragments of exons 6 and 7 of the VEGF gene were cloned into a recombinant adeno-associated virus (rAAV) vector. Expression of each peptide in vector-injected eyes was confirmed by reverse transcription-polymerase chain reaction and Western blot analysis. Intravitreal injection of each rAAV vector inhibited retinal NV by 71-83% (p < 0.001) compared with contralateral control eyes in the OIR mouse. Injection and expression of these peptides did not seem to affect the normal appearance of the retina. The results demonstrated that exon 6- and 7-derived VEGF peptides effectively inhibited oxygen-induced retinal NV. Therefore, these VEGF peptides have potential in the treatment of angiogenesis-associated retinal diseases in humans.
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Affiliation(s)
- Wen-Tao Deng
- Department of Ophthalmology and Powell Gene Therapy Center, University of Florida, College of Medicine, Gainesville, FL 32610, USA.
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237
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Doble N. High-resolution, in vivo retinal imaging using adaptive optics and its future role in ophthalmology. Expert Rev Med Devices 2006; 2:205-16. [PMID: 16293057 DOI: 10.1586/17434440.2.2.205] [Citation(s) in RCA: 13] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/08/2022]
Abstract
Until recently it was impossible to fully realize the optical resolution afforded by the human eye due to the inherent optical aberrations. These aberrations limit the ability to see fine structure in the retinal layers and visual perception of the outside world. A conventional spectacle or contact lens refraction only provides a static amelioration of the lowest order aberrations, namely defocus and astigmatism. In addition, all of these distortions are constantly evolving due to changes in accommodation and head/eye movements. The technique of adaptive optics not only corrects all of the static spatial modes but also measures and corrects any dynamic changes. Such systems have allowed for routine in vivo cellular imaging, the classification of individual photoreceptor cells and have enabled psychophysical testing of human visual function at the neural level. This review introduces the principle of adaptive optics and the key hardware required to implement such a scheme. The integration of adaptive optics into different imaging modalities is presented along with descriptions of current systems in use today and the experimental results obtained to date. Finally, the review concludes by discussing future technology and gives the author's prediction of how the field will evolve over the coming years.
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Affiliation(s)
- Nathan Doble
- Iris AO Inc., 2680 Bancroft Way, Berkeley, CA, USA.
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238
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Fan W, Agarwal N, Cooper NGF. The role of CaMKII in BDNF-mediated neuroprotection of retinal ganglion cells (RGC-5). Brain Res 2005; 1067:48-57. [PMID: 16337157 DOI: 10.1016/j.brainres.2005.10.030] [Citation(s) in RCA: 30] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/14/2005] [Revised: 09/05/2005] [Accepted: 10/09/2005] [Indexed: 12/01/2022]
Abstract
The purpose of the study is to determine if expression or secretion of brain-derived neurotrophic factor (BDNF) in retinal ganglion cells (RGC-5) is mediated by NFkappaB or Ca2+/calmodulin-dependent protein kinase II (CaMKII). RGC-5 cells were exposed to 1 mM glutamate for various periods of time, in the presence or absence of prospective regulatory molecules. BDNF mRNA and protein expression were assessed with the aid of real-time PCR and immunoblots, respectively, and BDNF secretion was determined by ELISA. The NFkappaB inhibitor (TLCK and PTD-p65), or a specific CaMKII inhibitor (m-AIP), was used to study association of NFkappaB or CaMKII with BDNF expression/secretion in RGC-5 cells. Glutamate stimulated a transient increase in BDNF mRNA and protein in RGC-5 cells, and also stimulated an early release of BDNF into the culture media. Neutralizing the BDNF or blocking the TrkB receptor enhanced the glutamate-induced cytotoxicity. NFkappaB nuclear translocation was revealed in response to glutamate treatment. Application of TLCK or PTD-p65 inhibited the glutamate-induced BDNF expression and secretion. Inhibition of CaMKII by m-AIP did not affect expression but significantly enhanced the release of BDNF from glutamate challenged cells. Our data suggest that glutamate treatment may stimulate expression of BDNF in RGC-5 cells through NFkappaB activation. A novel mechanism for neuroprotection is proposed for the CaMKII inhibitor, AIP, which appears to protect RGC-5 cells from cytotoxicity by enhancing the release of BDNF from glutamate challenged cells.
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Affiliation(s)
- Wei Fan
- Department of Anatomical Sciences and Neurobiology, 500 S. Preston St., Louisville, KY 40292, USA
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239
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Hu Y, Leaver SG, Plant GW, Hendriks WTJ, Niclou SP, Verhaagen J, Harvey AR, Cui Q. Lentiviral-mediated transfer of CNTF to schwann cells within reconstructed peripheral nerve grafts enhances adult retinal ganglion cell survival and axonal regeneration. Mol Ther 2005; 11:906-15. [PMID: 15922961 DOI: 10.1016/j.ymthe.2005.01.016] [Citation(s) in RCA: 89] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/15/2004] [Revised: 01/20/2005] [Accepted: 01/24/2005] [Indexed: 11/22/2022] Open
Abstract
We recently described a method for reconstituting peripheral nerve (PN) sheaths using adult Schwann cells (SCs). Reconstructed PN tissue grafted onto the cut optic nerve supports the regeneration of injured adult rat retinal ganglion cell (RGC) axons. To determine whether genetic manipulation of such grafts can further enhance regeneration, adult SCs were transduced with lentiviral vectors encoding either ciliary neurotrophic factor (LV-CNTF) or green fluorescent protein (LV-GFP). SCs expressed transgenes for at least 4 weeks after transplantation. There were high levels of CNTF mRNA and CNTF protein in PN grafts containing LV-CNTF-transduced SCs. Mean RGC survival was significantly increased with these grafts (11,863/retina) compared with LV-GFP controls (7064/retina). LV-CNTF-transduced SCs enhanced axonal regeneration to an even greater extent (3097 vs 393 RGCs/retina in LV-GFP controls). Many regenerated axons were myelinated. The use of genetically modified, reconstituted PN grafts to bridge tissue defects may provide new therapeutic strategies for the treatment of both CNS and PNS injuries.
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Affiliation(s)
- Ying Hu
- School of Anatomy and Human Biology, Western Australian Institute for Medical Research, UWA Centre for Medical Research, Perth, Australia
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240
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Deng WT, Yan Z, Dinculescu A, Pang J, Teusner JT, Cortez NG, Berns KI, Hauswirth WW. Adeno-Associated Virus-Mediated Expression of Vascular Endothelial Growth Factor Peptides Inhibits Retinal Neovascularization in a Mouse Model of Oxygen-Induced Retinopathy. Hum Gene Ther 2005. [DOI: 10.1089/hum.2005.16.ft-125] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/12/2022] Open
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241
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Zhou Y, Pernet V, Hauswirth WW, Di Polo A. Activation of the Extracellular Signal-Regulated Kinase 1/2 Pathway by AAV Gene Transfer Protects Retinal Ganglion Cells in Glaucoma. Mol Ther 2005; 12:402-12. [PMID: 15975850 DOI: 10.1016/j.ymthe.2005.04.004] [Citation(s) in RCA: 78] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/05/2005] [Revised: 04/11/2005] [Accepted: 04/11/2005] [Indexed: 11/18/2022] Open
Abstract
Glaucoma is the second leading cause of blindness in the world. Loss of vision in glaucomatous optic neuropathy is caused by the selective degeneration of retinal ganglion cells (RGCs). Ocular hypertension is a major risk factor in glaucoma, but visual field defects continue to progress in some patients despite the use of drugs that lower intraocular pressure. At present, there are no effective neuroprotective strategies for the treatment of this disease. The extracellular signal-regulated kinase (Erk) 1/2 pathway is an evolutionarily conserved mechanism used by several peptide factors to promote cell survival. Here we tested if selective activation of Erk1/2 protected RGCs in a rat model of experimental glaucoma. We used recombinant adeno-associated virus to transduce RGCs with genes encoding constitutively active or wild-type MEK1 (approved gene symbol MAP2K1), the upstream activator of Erk1/2. MEK1 gene transfer into RGCs markedly increased neuronal survival: 1366 +/- 70 RGCs/mm(2) (mean +/- SEM) were alive in the dorsal retina at 5 weeks after ocular hypertension surgery, a time when only 680 +/- 86 RGCs/mm(2) of these neurons remained in control eyes. We conclude that the Erk1/2 pathway plays a key role in the protection of RGCs from ocular hypertensive damage. This study identifies a novel gene therapy strategy in which selective activation of the Erk1/2 signaling pathway effectively slows cell death in glaucoma.
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Affiliation(s)
- Yu Zhou
- Department of Pathology and Cell Biology, Université de Montréal, 2900 Boulevard Edouard-Montpetit, Montreal, Quebec, Canada H3T 1J4
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242
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Abstract
Models of experimentally elevated intraocular pressure in rats provide valuable opportunities to discover and study mechanisms of pressure-induced optic nerve damage. The structure and vasculature of the rat optic nerve head have several anatomic similarities and differences from the primate that allow useful comparisons and insights into human glaucoma. Specifically, the ultrastructural relationship between astrocytes, retinal ganglion cell axons and the connective tissues of the optic nerve head appear quite similar to the primate, and have a high potential for revealing cellular mechanisms of axonal injury. Three widely used models of creating elevated IOP in rats exist. However, they are not all equivalent and appear to differ in the relationship they exhibit between the level of pressure and extent of optic nerve damage. This indicates that these models may differ in the mechanisms by which they produce elevated eye pressure. All of these models are amenable to a variety of methods for evaluating damage. These include objective and subjective histologic assessment of the optic nerve, counting cells in the retinal ganglion cell layer of the retina and the use of retinal whole mounts to count retinal ganglion cells that have been back-labeled with dye applied to the superior colliculus. In the decade since their introduction, these versatile models have provided important insights into mechanisms of pressure-induced optic nerve damage using sensitive molecular biology techniques. They have also allowed the evaluation of several potential strategies for neuroprotection in glaucoma, ranging from currently available drugs to gene transfer studies.
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Affiliation(s)
- John C Morrison
- Casey Eye Institute, Oregon Health and Science University, Portland, Oregon 97239-4197, USA.
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243
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Lau J, Dang M, Hockmann K, Ball AK. Effects of acute delivery of endothelin-1 on retinal ganglion cell loss in the rat. Exp Eye Res 2005; 82:132-45. [PMID: 16045909 DOI: 10.1016/j.exer.2005.06.002] [Citation(s) in RCA: 49] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/13/2005] [Revised: 04/02/2005] [Accepted: 06/02/2005] [Indexed: 11/24/2022]
Abstract
The vasoconstrictive peptide, Endothelin-1 (ET-1) has been found at elevated levels in glaucomatous eyes. In this study, a single 5mul intraocular injection of ET-1 was injected into the rat eye in order to characterize an in vivo retinal ganglion cell (RGC)-specific cell death model. The most effective concentration of ET-1 at inducing RGC loss at 2 weeks post-injection was determined using 5, 50 and 500mum concentrations of ET-1. The density of surviving RGCs was determined by counting Fluorogold labelled RGCs. A significant loss (25%) of RGCs was observed using only the 500mum concentration when compared to PBS-injected controls. GFAP immunohistochemistry revealed an increase in GFAP expression in Müller cell end-feet, as well as a total increase in GFAP expression (80%), following ET-1 treatment. These changes in GFAP expression are indicative of glial hyperactivity in response to stress. The specificity of ET-1 mediated cell death for RGCs was determined by measuring the changes in retinal thickness and TUNEL labeling. Retinal thickness was quantified using confocal and light microscopy. In confocal measurements, Yo Pro-1 was used to stain nuclear layers and the thickness of retinal layers determined from reconstructions. No significant loss in thickness was observed in any retinal layers. The same observations were seen in semi-thin sections when viewed by conventional transmitted light microscopy. The lack of significant thickness changes in the outer nuclear, outer plexiform or inner nuclear layer suggests that there was no significant cell loss in the retina other than in the RGC layer. Exclusive co-localization of TUNEL-labelled nuclei with Fluorogold-labelled cytoplasm provided additional evidence for RGC-specific death that most likely occurs via an apoptotic mechanism. A cell death time course was performed to determine RGC loss over time. RGC losses of 25, 25, 36 and 44% were observed at 1, 2, 3 and 4 weeks post-ET-1 injection, compared to PBS-injected controls. The total number of remaining RGC axons was determined by multiplying the number of optic nerve (ON) axons per unit area, by the cross-sectional area. There was a 31% loss in total ON axons in ET-1 treated eyes at 3 weeks post injection. Functional integrity of the visual system was determined by observing changes in the pupillary light reflex. ET-1 treatment resulted in a slowing of the pupil velocity by 31% and an average increase in the duration of contraction of 1.85sec (32% increase). These experiments provide evidence that acute ET-1 injections can produce RGC-specific cell death and many cellular changes that are similar to glaucoma. This potential glaucoma model leaves the optic nerve intact and may be used in subsequent experiments, which are involved in increasing RGC survival and functional recovery.
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Affiliation(s)
- Jonathan Lau
- Department of Pathology and Molecular Medicine, HSC Rm 1R1, McMaster University, 1200 Main St. West, Hamilton, Ont., Canada
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244
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Lebherz C, Auricchio A, Maguire AM, Rivera VM, Tang W, Grant RL, Clackson T, Bennett J, Wilson JM. Long-term inducible gene expression in the eye via adeno-associated virus gene transfer in nonhuman primates. Hum Gene Ther 2005; 16:178-86. [PMID: 15761258 DOI: 10.1089/hum.2005.16.178] [Citation(s) in RCA: 45] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/13/2022] Open
Abstract
Adeno-associated viral gene therapy has shown promise for the treatment of inherited and degenerative diseases in a variety of animal models. Some of the most dramatic results have been obtained in the field of ocular gene therapy, where efficacy has been tremendous in inherited and acquired retinal disorders. For the promise of this approach to be realized it will be necessary to create vectors capable of pharmacologic or physiologic regulation of the transgene. We describe in this paper a dimerizer-inducible viral expression system that is able to reproducibly drive expression of the reporter gene erythropoietin in the eyes of nonhuman primates over a period of 2.5 years. The expression profiles were characterized by minimal basal expression in the absence of inducer and dose-responsive maximal expression in the presence of inducer drug.
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Affiliation(s)
- Corinna Lebherz
- Gene Therapy Program, Department of Medicine, Division of Medical Genetics, University of Pennsylvania, Philadelphia, PA 19104, USA
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245
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Abstract
PURPOSE There has been recent interest in the potential use of gene therapy techniques to treat ocular disease. In this article, we consider the optic nerve diseases that are potentially most amenable to gene therapy. METHODS We discuss the recent success of gene transfer experiments in animal models of glaucoma, optic neuritis, Leber's hereditary optic neuropathy (LHON), and optic nerve transection, and we assess the possibility of using similar techniques to treat human disease in the future. RESULTS We have achieved highly efficient transfection of retinal ganglion cells in a rat model of glaucoma following a single intravitreal injection of adeno-associated virus (AAV). In our model, we have found that AAV-mediated gene therapy with brain-derived neurotrophic factor has a significant neuroprotective effect compared to saline or control virus injections. Guy and co-workers have successfully used AAV-mediated gene therapy to replace the defective mitochondrial enzyme subunit in cells derived from human patients with LHON. Gene therapy techniques have also shown promise in animal models of optic neuritis and optic nerve trauma. CONCLUSIONS Human diseases with single-gene defects such as LHON may soon be treated successfully by gene therapy, assuming that vectors continue to improve and are well tolerated in the human eye. Other optic nerve diseases such as glaucoma that do not have a single-gene defect may also benefit from gene therapy to enhance RGC survival. In all cases, the risks of treatment will need to be balanced against the potential benefits.
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Affiliation(s)
- K R G Martin
- Eye Department, Addenbrookes Hospital, Cambridge, UK.
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246
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Pernet V, Hauswirth WW, Di Polo A. Extracellular signal-regulated kinase 1/2 mediates survival, but not axon regeneration, of adult injured central nervous system neurons in vivo. J Neurochem 2005; 93:72-83. [PMID: 15773907 DOI: 10.1111/j.1471-4159.2005.03002.x] [Citation(s) in RCA: 63] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/19/2023]
Abstract
Neurotrophins play important roles in the response of adult neurons to injury. The intracellular signaling mechanisms used by neurotrophins to regulate survival and axon growth in the mature CNS in vivo are not well understood. The goal of this study was to define the role of the extracellular signal-regulated kinases 1/2 (Erk1/2) pathway in the survival and axon regeneration of adult rat retinal ganglion cells (RGCs), a prototypical central neuron population. We used recombinant adeno-associated virus (AAV) to selectively transduce RGCs with genes encoding constitutively active or wild-type mitogen-activated protein kinase kinase 1 (MEK1), the upstream activator of Erk1/2. In combination with anterograde and retrograde tracing techniques, we monitored neuronal survival and axon regeneration in vivo. MEK1 gene delivery led to robust and selective transgene expression in multiple RGC compartments including cell bodies, dendrites, axons and targets in the brain. Furthermore, MEK1 activation induced in vivo phosphorylation of Erk1/2 in RGC bodies and axons. Quantitative analysis of cell survival demonstrated that Erk1/2 activation promoted robust RGC neuroprotection after optic nerve injury. In contrast, stimulation of the Erk1/2 pathway was not sufficient to induce RGC axon growth beyond the lesion site. We conclude that the Erk1/2 pathway plays a key role in the survival of axotomized mammalian RGCs in vivo, and that activation of other signaling components is required for axon regeneration in the growth inhibitory CNS environment.
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Affiliation(s)
- Vincent Pernet
- Department of Pathology and Cell Biology, Université de Montréal, Montreal, Quebec, Canada
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247
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Schuettauf F, Vorwerk C, Naskar R, Orlin A, Quinto K, Zurakowski D, Dejneka NS, Klein RL, Meyer EM, Bennett J. Adeno-associated viruses containing bFGF or BDNF are neuroprotective against excitotoxicity. Curr Eye Res 2005; 29:379-86. [PMID: 15764082 DOI: 10.1080/02713680490517872] [Citation(s) in RCA: 42] [Impact Index Per Article: 2.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/23/2022]
Abstract
PURPOSE Brain-derived neurotrophic factor (BDNF) and basic fibroblast growth factor (bFGF) hold much promise for the protection of retinal ganglion cells against excitotoxic cell death. We tested the possibility of delivering these growth factors to retinal ganglion cells via an adeno-associated viral (AAV) vector and tested their efficacy in two models of excitotoxicity. METHODS Rat retinas were infected with AAV vectors encoding bFGF or BDNF. A control vector containing green fluorescent protein (GFP) was injected in the contralateral eye. Eyes were subjected to either an intravitreal injection of N-methyl-D-aspartate (NMDA) or optic nerve crush, and ganglion cell survival was evaluated. RESULTS AAV.CMV.bFGF and AAV.CBA.BDNF were neuroprotective against NMDA injection 1 month post-treatment. Additionally, AAV.CMV.bFGF was protective against optic nerve crush. CONCLUSION AAV-mediated delivery of bFGF and BDNF can promote retinal cell survival following excitotoxic insult.
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Affiliation(s)
- Frank Schuettauf
- Department of Ophthalmology, University of Pennsylvania, Scheie Eye Institute, Philadelphia, Pennsylvania, USA.
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248
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Morrison JC, Johnson EC, Cepurna W, Jia L. Understanding mechanisms of pressure-induced optic nerve damage. Prog Retin Eye Res 2005; 24:217-40. [PMID: 15610974 DOI: 10.1016/j.preteyeres.2004.08.003] [Citation(s) in RCA: 175] [Impact Index Per Article: 9.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Patients with glaucoma can suffer progressive vision loss, even in the face of what appears to be excellent intraocular pressure (IOP) control. Some of this may be secondary to non-pressure-related (pressure-independent) factors. However, it is likely that chronically elevated IOP produces progressive changes in the optic nerve head, the retina, or both that alter susceptibility of remaining optic nerve fibers to IOP. In order to understand the nature of these progressive changes, relevant, cost-effective animal models are necessary. Several rat models are now used to produce chronic, elevated IOP, and methods exist for measuring the resulting IOP and determining the extent of the damage this causes to the retina and optic nerve. A comparison of damage, pressure and duration shows that these models are not necessarily equivalent. These tools are beginning to uncover clear evidence that elevated IOP produces progressive changes in the optic nerve head and retina. In the optic nerve head, these include axonal and non-axonal effects, the latter pointing to involvement of extracellular matrix and astrocyte responses. In the retina, retinal ganglion cells appear to undergo changes in neurotrophin response as well as morphologic changes prior to actual cell death. These, and other, as yet uncovered, abnormalities in the optic nerve head and retina may influence relative susceptibility to IOP and explain progressive optic nerve damage and visual field loss, in spite of apparent, clinically adequate IOP control. Ultimately, this knowledge may lead to the development of new treatments designed to preserve vision in these difficult patients.
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Affiliation(s)
- John C Morrison
- Kenneth C. Swan Ocular Neurobiology Laboratory, Casey Eye Institute, Oregon Health and Sciences University, 3375 S.W Terwilliger Blvd., Portland, OR 97239, USA.
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249
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Abstract
The choice of vectors, transgenes, regulatory elements, delivery approaches and the capacity to transduce the appropriate target cell type all influence the effectiveness of gene therapy for neurological diseases. Furthermore, even if many strategies are sound and effective in experimental animals, issues relating to side effects of gene therapy, longevity of therapeutic transgene expression and diffusion throughout the brain can limit the clinical potential of gene therapy. During the past 12-18 months, there have been significant advances in the following areas: the capacity to target vectors to predetermined cells types; the development of gene therapy approaches for the treatment of dominant inherited and neurodegenerative diseases; the capacity to achieve systemic delivery of viral vectors to the brain; and the development of viral vectors to model neurological diseases.
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Affiliation(s)
- Pedro Ricardo Lowenstein
- Gene Therapeutics Research Institute, Cedars-Sinai Medical Center and Department of Medicine, University of California, Los Angeles, USA.
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