scholarly journals Adeno-Associated Viral Vectors as a Tool for Large Gene Delivery to the Retina

Genes ◽  
2019 ◽  
Vol 10 (4) ◽  
pp. 287 ◽  
Author(s):  
Trapani
Keyword(s):  
Gene Therapy ◽  
Viral Vectors ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Retinal Diseases ◽  
Considerable Effort ◽  
Safety And Efficacy ◽  
Large Gene ◽  
Packaging Capacity ◽  
Large Genes

Gene therapy using adeno-associated viral (AAV) vectors currently represents the most promising approach for the treatment of many inherited retinal diseases (IRDs), given AAV’s ability to efficiently deliver therapeutic genes to both photoreceptors and retinal pigment epithelium, and their excellent safety and efficacy profiles in humans. However, one of the main obstacles to widespread AAV application is their limited packaging capacity, which precludes their use from the treatment of IRDs which are caused by mutations in genes whose coding sequence exceeds 5 kb. Therefore, in recent years, considerable effort has been made to identify strategies to increase the transfer capacity of AAV vectors. This review will discuss these new developed strategies, highlighting the advancements as well as the limitations that the field has still to overcome to finally expand the applicability of AAV vectors to IRDs due to mutations in large genes.

scholarly journals Leber congenital amaurosis/early-onset severe retinal dystrophy: current management and clinical trials

2021 ◽  
pp. bjophthalmol-2020-318483
Author(s):  
Malena Daich Varela ◽  
Thales Antonio Cabral de Guimaraes ◽  
Michalis Georgiou ◽  
Michel Michaelides
Keyword(s):  
Gene Therapy ◽  
Clinical Trials ◽  
Early Onset ◽  
Viral Vectors ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Retinal Dystrophy ◽  
European Medicines Agency ◽  
Current Management ◽  
Leber Congenital Amaurosis

Leber congenital amaurosis (LCA) is a severe congenital/early-onset retinal dystrophy. Given its monogenic nature and the immunological and anatomical privileges of the eye, LCA has been particularly targeted by cutting-edge research. In this review, we describe the current management of LCA, and highlight the clinical trials that are on-going and planned. RPE65-related LCA pivotal trials, which culminated in the first Food and Drug Administration-approved and European Medicines Agency-approved ocular gene therapy, have paved the way for a new era of genetic treatments in ophthalmology. At present, multiple clinical trials are available worldwide applying different techniques, aiming to achieve better outcomes and include more genes and variants. Genetic therapy is not only implementing gene supplementation by the use of adeno-associated viral vectors, but also clustered regularly interspaced short palindromic repeats (CRISPR)-mediated gene editing and post-transcriptional regulation through antisense oligonucleotides. Pharmacological approaches intending to decrease photoreceptor degeneration by supplementing 11-cis-retinal and cell therapy’s aim to replace the retinal pigment epithelium, providing a trophic and metabolic retinal structure, are also under investigation. Furthermore, optoelectric devices and optogenetics are also an option for patients with residual visual pathway. After more than 10 years since the first patient with LCA received gene therapy, we also discuss future challenges, such as the overlap between different techniques and the long-term durability of efficacy. The next 5 years are likely to be key to whether genetic therapies will achieve their full promise, and whether stem cell/cellular therapies will break through into clinical trial evaluation.

scholarly journals Pathogenic Effects of Mineralocorticoid Pathway Activation in Retinal Pigment Epithelium

2021 ◽  
Vol 22 (17) ◽  
pp. 9618
Author(s):  
Jérémie Canonica ◽  
Min Zhao ◽  
Tatiana Favez ◽  
Emmanuelle Gelizé ◽  
Laurent Jonet ◽  
...  
Keyword(s):  
Extracellular Matrix ◽  
Retinal Pigment Epithelium ◽  
Barrier Function ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Retinal Diseases ◽  
Mesenchymal Transition ◽  
Rpe Cells ◽  
Pathway Activation ◽  
And Migration

Glucocorticoids are amongst the most used drugs to treat retinal diseases of various origins. Yet, the transcriptional regulations induced by glucocorticoid receptor (GR) and mineralocorticoid receptor (MR) activation in retinal pigment epithelium cells (RPE) that form the outer blood–retina barrier are unknown. Levels of endogenous corticoids, ligands for MR and GR, were measured in human ocular media. Human RPE cells derived from induced pluripotent stem cells (iRPE) were used to analyze the pan-transcriptional regulations induced by aldosterone—an MR-specific agonist, or cortisol or cortisol + RU486—a GR antagonist. The retinal phenotype of transgenic mice that overexpress the human MR (P1.hMR) was analyzed. In the human eye, the main ligand for GR and MR is cortisol. The iRPE cells express functional GR and MR. The subset of genes regulated by aldosterone and by cortisol + RU-486, and not by cortisol alone, mimics an imbalance toward MR activation. They are involved in extracellular matrix remodeling (CNN1, MGP, AMTN), epithelial–mesenchymal transition, RPE cell proliferation and migration (ITGB3, PLAUR and FOSL1) and immune balance (TNFSF18 and PTX3). The P1.hMR mice showed choroidal vasodilation, focal alteration of the RPE/choroid interface and migration of RPE cells together with RPE barrier function alteration, similar to human retinal diseases within the pachychoroid spectrum. RPE is a corticosteroid-sensitive epithelium. MR pathway activation in the RPE regulates genes involved in barrier function, extracellular matrix, neural regulation and epithelial differentiation, which could contribute to retinal pathology.

scholarly journals Choroideremia: from genetic and clinical phenotyping to gene therapy and future treatments

2018 ◽  
Vol 10 ◽  
pp. 251584141881749 ◽  
Author(s):  
Andreas Mitsios ◽  
Adam M. Dubis ◽  
Mariya Moosajee
Keyword(s):  
Gene Therapy ◽  
Stem Cell ◽  
Current Knowledge ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Nonsense Suppression ◽  
Treatment Interventions ◽  
Natural History Studies ◽  
Stem Cell Treatment ◽  
Clinical Phenotyping

Choroideremia is an X-linked inherited chorioretinal dystrophy leading to blindness by late adulthood. Choroideremia is caused by mutations in the CHM gene which encodes Rab escort protein 1 (REP1), an ubiquitously expressed protein involved in intracellular trafficking and prenylation activity. The exact site of pathogenesis remains unclear but results in degeneration of the photoreceptors, retinal pigment epithelium and choroid. Animal and stem cell models have been used to study the molecular defects in choroideremia and test effectiveness of treatment interventions. Natural history studies of choroideremia have provided additional insight into the clinical phenotype of the condition and prepared the way for clinical trials aiming to investigate the safety and efficacy of suitable therapies. In this review, we provide a summary of the current knowledge on the genetics, pathophysiology, clinical features and therapeutic strategies that might become available for choroideremia in the future, including gene therapy, stem cell treatment and small-molecule drugs with nonsense suppression action.

scholarly journals Complement modulation in the retinal pigment epithelium rescues photoreceptor degeneration in a mouse model of Stargardt disease

2017 ◽  
Vol 114 (15) ◽  
pp. 3987-3992 ◽  
Author(s):  
Tamara L. Lenis ◽  
Shanta Sarfare ◽  
Zhichun Jiang ◽  
Marcia B. Lloyd ◽  
Dean Bok ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Retinal Pigment Epithelium ◽  
Complement System ◽  
Complement Activation ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Host Cells ◽  
Etiologic Factor ◽  
Photoreceptor Degeneration ◽  
The Complement System

Recessive Stargardt macular degeneration (STGD1) is caused by mutations in the gene for the ABCA4 transporter in photoreceptor outer segments. STGD1 patients and Abca4−/− (STGD1) mice exhibit buildup of bisretinoid-containing lipofuscin pigments in the retinal pigment epithelium (RPE), increased oxidative stress, augmented complement activation and slow degeneration of photoreceptors. A reduction in complement negative regulatory proteins (CRPs), possibly owing to bisretinoid accumulation, may be responsible for the increased complement activation seen on the RPE of STGD1 mice. CRPs prevent attack on host cells by the complement system, and complement receptor 1-like protein y (CRRY) is an important CRP in mice. Here we attempted to rescue the phenotype in STGD1 mice by increasing expression of CRRY in the RPE using a gene therapy approach. We injected recombinant adeno-associated virus containing the CRRY coding sequence (AAV-CRRY) into the subretinal space of 4-wk-old Abca4−/− mice. This resulted in sustained, several-fold increased expression of CRRY in the RPE, which significantly reduced the complement factors C3/C3b in the RPE. Unexpectedly, AAV-CRRY–treated STGD1 mice also showed reduced accumulation of bisretinoids compared with sham-injected STGD1 control mice. Furthermore, we observed slower photoreceptor degeneration and increased visual chromophore in 1-y-old AAV-CRRY–treated STGD1 mice. Rescue of the STGD1 phenotype by AAV-CRRY gene therapy suggests that complement attack on the RPE is an important etiologic factor in STGD1. Modulation of the complement system by locally increasing CRP expression using targeted gene therapy represents a potential treatment strategy for STGD1 and other retinopathies associated with complement dysregulation.

scholarly journals Intercellular Trafficking of Adenovirus-Delivered HSV VP22 from the Retinal Pigment Epithelium to the Photoreceptors—Implications for Gene Therapy

2002 ◽  
Vol 6 (6) ◽  
pp. 813-823 ◽  
Author(s):  
Siobhan M. Cashman ◽  
Sonia L. Sadowski ◽  
David J. Morris ◽  
Jeanne Frederick ◽  
Rajendra Kumar-Singh
Keyword(s):  
Gene Therapy ◽  
Retinal Pigment Epithelium ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Intercellular Trafficking

Human iPSC modeling reveals mutation-specific responses to gene therapy in Best disease

2019 ◽  
Author(s):  
Divya Sinha ◽  
Benjamin Steyer ◽  
Pawan K. Shahi ◽  
Katherine Mueller ◽  
Rasa Valiauga ◽  
...  
Keyword(s):  
Gene Therapy ◽  
Genome Editing ◽  
Pigment Epithelium ◽  
Retinal Pigment ◽  
Gene Replacement ◽  
Patient Specific ◽  
Genomic Alteration ◽  
Inherited Disorders ◽  
Induced Pluripotent ◽  
Best Disease

AbstractDominantly inherited disorders are not typically considered therapeutic candidates for gene augmentation. Here, we utilized patient-specific induced pluripotent stem cell-derived retinal pigment epithelium (iPSC-RPE) to test the potential of gene augmentation to treat Best disease, a dominant macular dystrophy caused by over 200 missense mutations in BEST1. Gene augmentation in iPSC-RPE fully restored BEST1 calcium-activated chloride channel activity and improved rhodopsin degradation in iPSC-RPE models of recessive bestrophinopathy and dominant Best disease caused by two different ion binding domain mutations. A dominant Best disease iPSC-RPE model that did not respond to gene augmentation showed normalization of BEST1 channel activity following CRISPR-Cas9 editing of the mutant allele. We then tested gene editing in all three dominant Best disease iPSC-RPE models, which produced premature stop codons exclusively within the mutant BEST1 alleles. Single-cell profiling demonstrated no adverse perturbation of RPE transcriptional programs in any model, although off-target analysis detected a silent genomic alteration in one model. These results suggest that gene augmentation is a viable first-line approach for some dominant Best disease patients and that non-responders are candidates for alternate approaches such as genome editing. However, testing genome editing strategies for on-target efficiency and off-target events using patient-matched iPSC-RPE model systems is warranted. In summary, personalized iPSC-RPE models can be used to select among a growing list of gene therapy options to maximize safety and efficacy while minimizing time and cost. Similar scenarios likely exist for other genotypically diverse channelopathies, expanding the therapeutic landscape for affected patients.SignificanceDominantly inherited disorders pose distinct challenges for gene therapies, particularly in the face of extreme mutational diversity. We tested whether a broad gene replacement strategy could reverse the cellular phenotype of Best disease, a dominant blinding condition that targets retinal pigment epithelium (RPE). Using RPE generated from patient-specific induced pluripotent stem cells (iPSCs), we show that gene replacement functionally overcomes some, but not all, of the tested mutations. In comparison, all dominant Best disease models tested were phenotypically corrected after mutation-specific genome editing, although one off-target genomic alteration was discovered. Our results support a two-tiered approach to gene therapy for Best disease, guided by safety and efficacy testing in iPSC-RPE models to maximize personal and public health value.

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