Genetic rescue models refute nonautonomous rod cell death in retinitis pigmentosa

Retinitis pigmentosa (RP) is an inherited neurodegenerative disease, in which the death of mutant rod photoreceptors leads secondarily to the non-cell autonomous death of cone photoreceptors. Gene therapy is a promising treatment strategy. Unfortunately, current methods of gene delivery treat only a fraction of diseased cells, yielding retinas that are a mosaic of treated and untreated rods, as well as cones. In this study, we created two RP mouse models to test whether dying, untreated rods negatively impact treated, rescued rods. In one model, treated and untreated rods were segregated. In the second model, treated and untreated rods were diffusely intermixed, and their ratio was controlled to achieve low-, medium-, or high-efficiency rescue. Analysis of these mosaic retinas demonstrated that rescued rods (and cones) survive, even when they are greatly outnumbered by dying photoreceptors. On the other hand, the rescued photoreceptors did exhibit long-term defects in their outer segments (OSs), which were less severe when more photoreceptors were treated. In summary, our study suggests that even low-efficiency gene therapy may achieve stable survival of rescued photoreceptors in RP patients, albeit with OS dysgenesis.

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Myeloid Expansion after Insertional Activation of MDS1/EVI1, PRDM16 and SETBP1 in a Successful Chronic Granulomatous Gene Therapy Trial.

Blood ◽

10.1182/blood.v106.11.198.198 ◽

2005 ◽

Vol 106 (11) ◽

pp. 198-198

Author(s):

Kerstin Schwarzwaelder ◽

Manfred Schmidt ◽

Marion G. Ott ◽

Stefan Stein ◽

Hanno Glimm ◽

...

Keyword(s):

Gene Therapy ◽

Side Effects ◽

High Efficiency ◽

Post Treatment ◽

Multiple Time ◽

Gene Therapy Trial ◽

Vector Integration ◽

Integration Sites ◽

Therapy Trial

Abstract Successful gene therapy trials of ADA-SCID and SCID-X1 demonstrated the curative potential of oncoretroviral gene transfer. Integration of the retroviral vectors used in these studies has been thought to be a random process but severe side effects in gene therapy and in vitro studies revealed preferred insertion of these vectors mainly around transcription start sites. In SCID patients proliferation advantage of gene corrected cells was one reason for the success of the trials, whereas in the most recent chronic granulomatous disease (CGD) gene therapy trial corrected cells do not have any selective advantage therefore the two patients received mild busulfan treatment before transplantation. High efficiency transduction and conditioning have helped in the successful correction of the patients. Peripheral blood granulocytes show a stable expression (>10%) of the transgene (gp91phox) in patient 1 (15 months post treatment) as well as in patient 2 (11 months post treatment). We reasoned that, unlike T cells, which have the capability to proliferate independent of their bone marrow progenitors, granulocytes more directly reflect the influence of retrovirus insertion, and should therefore allow to closely monitor clonal fate in vivo and its potential relation to vector insertion. To study the clonality of the corrected myelopoiesis, the long term activity of individual cell clones, and the distribution of integration sites in active cells we carried out high sensitive LAM-PCR. The highly polyclonal composition of transduced cells forming myelopoiesis caused the sustained expression of gp91phox. Individual clones carrying the transgene could be detected at multiple time points. To define whether corrected cells have a proliferation advantage due to their vector integration we started large-scale sequencing and mapping of involved insertion sites. We here present >700 unique mappable integration sites of the two treated patients. The distribution of the SFFV based retroviral vector integration sites in this trial turned non random 5 months after transplantation. Corrected long-term myelopoiesis expanded 3- to 5- fold in the two patients due to activating common integration sites (CIS) in the zinc finger transcription factor homologs MDS1/EVI1, PRDM16, or in SETBP1, suggesting that these genes influence regulation of normal long-term hematopoiesis in humans. Our data indicate that the therapeutic benefit in this trial was activated through insertional side effects, therefore our findings have important implications in novel gene therapy approaches.

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Successful arrest of photoreceptor and vision loss expands the therapeutic window of retinal gene therapy to later stages of disease

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1509914112 ◽

2015 ◽

Vol 112 (43) ◽

pp. E5844-E5853 ◽

Cited By ~ 44

Author(s):

William A. Beltran ◽

Artur V. Cideciyan ◽

Simone Iwabe ◽

Malgorzata Swider ◽

Mychajlo S. Kosyk ◽

...

Keyword(s):

Gene Therapy ◽

Retinitis Pigmentosa ◽

Large Animal Model ◽

Therapeutic Window ◽

Large Animal ◽

Visual Behavior ◽

Rate Of Progression ◽

Photoreceptor Neurons ◽

Retinal Gene Therapy

Inherited retinal degenerations cause progressive loss of photoreceptor neurons with eventual blindness. Corrective or neuroprotective gene therapies under development could be delivered at a predegeneration stage to prevent the onset of disease, as well as at intermediate-degeneration stages to slow the rate of progression. Most preclinical gene therapy successes to date have been as predegeneration interventions. In many animal models, as well as in human studies, to date, retinal gene therapy administered well after the onset of degeneration was not able to modify the rate of progression even when successfully reversing dysfunction. We evaluated consequences of gene therapy delivered at intermediate stages of disease in a canine model of X-linked retinitis pigmentosa (XLRP) caused by a mutation in the Retinitis Pigmentosa GTPase Regulator (RPGR) gene. Spatiotemporal natural history of disease was defined and therapeutic dose selected based on predegeneration results. Then interventions were timed at earlier and later phases of intermediate-stage disease, and photoreceptor degeneration monitored with noninvasive imaging, electrophysiological function, and visual behavior for more than 2 y. All parameters showed substantial and significant arrest of the progressive time course of disease with treatment, which resulted in long-term improved retinal function and visual behavior compared with control eyes. Histology confirmed that the humanRPGRtransgene was stably expressed in photoreceptors and associated with improved structural preservation of rods, cones, and ON bipolar cells together with correction of opsin mislocalization. These findings in a clinically relevant large animal model demonstrate the long-term efficacy ofRPGRgene augmentation and substantially broaden the therapeutic window for intervention in patients withRPGR-XLRP.

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Advanced Materials for Gene Delivery

Advanced Materials Research ◽

10.4028/www.scientific.net/amr.995.29 ◽

2014 ◽

Vol 995 ◽

pp. 29-47 ◽

Cited By ~ 1

Author(s):

Mohammad A. Jafar Mazumder ◽

Md. Hasan Zahir ◽

Sharif F. Zaman

Keyword(s):

Gene Therapy ◽

Gene Delivery ◽

Genetic Disorders ◽

Basic Research ◽

Advanced Materials ◽

Clinical Settings ◽

Efficient Gene ◽

Efficient Delivery ◽

Promising Treatment

Gene therapy is a widespread and promising treatment of many diseases resulting from genetic disorders, infections and cancer. The feasibility of the gene therapy is mainly depends on the development of appropriate method and suitable vectors. For an efficient gene delivery, it is very important to use a carrier that is easy to produce, stable, non-oncogenic and non-immunogenic. Currently most of the vectors actually suffer from many problems. Therefore, the ideal gene therapy delivery system should be developed that can be easily used for highly efficient delivery and able to maintain long-term gene expression, and can be applicable to basic research as well as clinical settings. This article provides a brief over view on the concept and aim of gene delivery, the different gene delivery systems and use of different materials as a carrier in the area of gene therapy.

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Correction for Koch et al., Genetic rescue models refute nonautonomous rod cell death in retinitis pigmentosa

Proceedings of the National Academy of Sciences ◽

10.1073/pnas.1708940114 ◽

2017 ◽

Vol 114 (27) ◽

pp. E5484-E5484

Keyword(s):

Cell Death ◽

Retinitis Pigmentosa ◽

Genetic Rescue ◽

Rod Cell

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Faculty Opinions recommendation of Genetic rescue models refute nonautonomous rod cell death in retinitis pigmentosa.

Faculty Opinions – Post-Publication Peer Review of the Biomedical Literature ◽

10.3410/f.727580750.793531764 ◽

2017 ◽

Author(s):

Gordon Fain

Keyword(s):

Cell Death ◽

Retinitis Pigmentosa ◽

Genetic Rescue ◽

Rod Cell

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Movement of retinal along cone and rod photoreceptors

Visual Neuroscience ◽

10.1017/s0952523800001735 ◽

1994 ◽

Vol 11 (2) ◽

pp. 389-399 ◽

Cited By ~ 29

Author(s):

Jing Jin ◽

Gregor J. Jones ◽

M. Carter Cornwall

Keyword(s):

Cell Body ◽

Dark Adaptation ◽

Visual Pigment ◽

Outer Segment ◽

Light Adaptation ◽

Rod Photoreceptors ◽

Rod Outer Segment ◽

Rods And Cones ◽

Outer Segments ◽

Rod Cell

AbstractSingle isolated photoreceptors can be taken through a visual cycle of light adaptation by bleaching visual pigment, followed by dark adaptation when supplied with 11–cis retinal. Light adaptation after bleaching is manifested by faster response kinetics and a permanent reduction in sensitivity to light flashes, presumed to be due to the presence of bleached visual pigment. The recovery of flash sensitivity during dark adaptation is assumed to be due to regeneration of visual pigment to pre-bleach levels. In previous work, the outer segments of bleached, light-adapted cells were exposed to 11–cis retinal. In the present work, the cell bodies of bleached photoreceptors were exposed. We report a marked difference between rods and cones. Bleached cones recover sensitivity when their cell bodies are exposed to 11–cis retinal. Bleached rods do not. These results imply that retinal can move freely along the cone photoreceptor, but retinal either is not taken up by the rod cell body or retinal cannot move from the rod cell body to the rod outer segment. The free transfer of retinal along cone but not along rod photoreceptors could explain why, during dark adaptation in the retina, cones have access to a store of 11–cis retinal which is not available to rods. Additional experiments investigated the movement of retinal along bleached rod outer segments. The results indicate that retinal can move along the rod outer segment, but that this movement is slow, occurring at about the same rate as the regeneration of visual pigment.

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