The gene therapy revolution in ophthalmology

Unlocking therapeutic potential: dual gene therapy for ameliorating the disease phenotypes in a mouse model of RPE65 Leber congenital amaurosis

Leber congenital amaurosis (LCA) is the most common genetic cause of congenital visual impairment in infants and children. Patients with LCA who harbor RPE65 mutations exhibit a deficiency in photoreceptor rhodopsin, leading to severe night blindness and visual impairment following birth. Since either gene replacement therapy or anti-apoptosis therapy alone cannot maintain both functional and morphological normality for a long time in the animal model, we propose a robust treatment strategy, that is, gene replacement therapy combined with anti-apoptotic therapy to protect photoreceptors from further degeneration while compensating for lost RPE65 function. Here, rd12 mice were injected subretinally at postnatal day 14 with four vector administrations, respectively. At 6 months after treatment, it was discovered that injection of three vectors, AAV8 (Y733F)-CBA-hRPE65, AAV8(Y733F)-CBA-hRPE65-BCL-2-L10 and mixture of half-dose AAV8(Y733F)-CBA-hRPE65 and half-dose AAV8 (Y733F)-CBA-BCL-2-L10, could partially restore the visual function of rd12 mice. Meanwhile, these treated eyes also exhibited a thicker outer nuclear layer (ONL) structure. However, despite the fact that the eyes of rd12 mice injected with the AAV8 (Y733F)-CBA-BCL-2-L10 vector displayed a slightly thicker ONL structure compared to untreated eyes, the visual function of the treated eyes did not recover. Continuing the observation period to 12 months after treatment, we found that compared to rd12 mice at 6-month post-treatment, rd12 mice injected with AAV8 (Y733F)-CBA-hRPE65 or mixture of half-dose AAV8(Y733F)-CBA-hRPE65 and half-dose AAV8 (Y733F)-CBA-BCL-2-L10 exhibited varying degrees of decline in both visual function and ONL thickness. However, in the case of rd12 mice injected with the AAV8(Y733F)-CBA-hRPE65-BCL-2-L10 vector, the ONL thickness remains consistent at both 6 and 12 months after treatment. These mice continued to maintain a relatively strong visual function and showed restoration in the levels of RPE65 and Rhodopsin protein expression. Our findings illustrate that early postnatal treatment with AAV vectors containing both the hRPE65 gene and the Bcl-2L10 anti-apoptotic gene provide enhanced and sustained retinal protection.

Burden and clinical profile of genetic eye diseases in children in Nigeria: a descriptive cross-sectional study

Introduction

ophthalmic genetics is rapidly evolving globally but is still nascent in much of sub-Saharan Africa, with gaps in knowledge about the burden in the region. This study evaluated the burden and manifestations of genetic eye diseases in children in Ibadan, Nigeria.

Methods

this was a hospital-based cross-sectional study in which new and follow-up paediatric eye clinic patients were recruited consecutively at the University College Hospital, Ibadan. Children with genetic eye diseases had comprehensive ocular and systemic examinations, and their pedigrees were charted to determine the probable modes of inheritance. The main outcome variables were the proportion of study participants with genetic eye diseases, the probable modes of inheritance, and the clinical diagnoses. Summary statistics were performed using means and standard deviations for numerical variables and proportions for categorical variables.

Results

fifty-two (12%) of 444 children had genetic eye diseases, and their mean (SD) age was 88.8 ± 50.4 months. Thirteen different phenotypic diagnoses were made following the evaluation of the 52 children, including primary congenital glaucoma (13, 25%) and familial non-syndromic cataracts (8, 15%). The probable modes of inheritance were derived from the pedigree charts, and 30 (58%) conditions were presumed to be sporadic.

Conclusion

this study demonstrated a significant burden and a wide range of paediatric genetic eye diseases in this tertiary referral centre in Nigeria. This information provides invaluable evidence for planning ophthalmic genetic services.

Retrospective and prospective study of progressive retinal atrophy in dogs presented to the veterinary hospital of the Federal University of Parana, Brazil

Background:

Progressive retinal atrophy (PRA) is one of the main causes of blindness in dogs. Despite its clinical importance, there is limited epidemiological information available, particularly in South America.

Aim:

The main objective of this study was to perform a retrospective, and prospective analysis of PRA in dogs admitted at the Veterinary Hospital of the Federal University of Paraná, Brazil.

Methods:

Medical records of dogs admitted between 2014 and 2018 were selected through the archives of the Comparative Ophthalmology Laboratory. A total of 130 dogs with medical records indicating clinical signs suggestive of PRA, independent of the electroretinography confirmation, were selected. In order to investigate common characteristics, each patient’s clinical history, ophthalmic examination, and visual status were reviewed (obstacle course, pupillary light reflex, dazzle reflex, visual tracking to a cotton ball, and menace responses). Additionally, a prospective study was performed, where flash electroretinography was performed on 30 animals with clinical signs suggestive of PRA, and 14 animals were selected for fundus photography. Data were assessed through descriptive and inferential statistics.

Results:

A total of 2,055 dogs were evaluated between January 2014 and December 2018. Of those, 130 animals were presumptively diagnosed with PRA (6.33%), consisting of 18 different breeds and 27 dogs with a mixed pedigree. Poodles were the most prevalent breed (n = 26; 20.00%), followed by Cocker Spaniels (n = 19; 14.62%). In the reported caseload, Pomeranians showed a considerably higher odds ratio for PRA development (15.36%).

Conclusion:

Pomeranians presented a high odds ratio, suggesting that further studies may be performed with breeds with a high potential for developing this disease.

A Review on Mesenchymal Stem Cells for Treatment of Retinal Diseases

Mesenchymal Stem Cells (MSCs) have been studied extensively for the treatment of several retinal diseases. The therapeutic potential of MSCs lies in its ability to differentiate into multiple lineages and secretome enriched with immunomodulatory, anti-angiogenic and neurotrophic factors. Several studies have reported the role of MSCs in repair and regeneration of the damaged retina where the secreted factors from MSCs prevent retinal degeneration, improve retinal morphology and function. MSCs also donate mitochondria to rescue the function of retinal cells and exosomes secreted by MSCs were found to have anti-apoptotic and anti-inflammatory effects. Based on several promising results obtained from the preclinical studies, several clinical trials were initiated to explore the potential advantages of MSCs for the treatment of retinal diseases. This review summarizes the various properties of MSCs that help to repair and restore the damaged retinal cells and its potential for the treatment of retinal degenerative diseases.

A new mouse model for retinal degeneration due to Fam161a deficiency

FAM161A mutations are the most common cause of inherited retinal degenerations in Israel. We generated a knockout (KO) mouse model, Fam161a^tm1b/tm1b, lacking the major exon #3 which was replaced by a construct that include LacZ under the expression of the Fam161a promoter. LacZ staining was evident in ganglion cells, inner and outer nuclear layers and inner and outer-segments of photoreceptors in KO mice. No immunofluorescence staining of Fam161a was evident in the KO retina. Visual acuity and electroretinographic (ERG) responses showed a gradual decrease between the ages of 1 and 8 months. Optical coherence tomography (OCT) showed thinning of the whole retina. Hypoautofluorescence and hyperautofluorescence pigments was observed in retinas of older mice. Histological analysis revealed a progressive degeneration of photoreceptors along time and high-resolution transmission electron microscopy (TEM) analysis showed that photoreceptor outer segment disks were disorganized in a perpendicular orientation and outer segment base was wider and shorter than in WT mice. Molecular degenerative markers, such as microglia and CALPAIN-2, appear already in a 1-month old KO retina. These results indicate that a homozygous Fam161a frameshift mutation affects retinal function and causes retinal degeneration. This model will be used for gene therapy treatment in the future.

Efficacy of 5-Fluorouracil in the Treatment of Pterygium

Objective To determine the efficacy of 5-Fluorouracil (FU) in the treatment of pterygium. Methodology After meeting the inclusion criteria 101 patients were enrolled in this study. Informed consent and demographic information was taken from all the patients. Patients underwent ophthalmic clinical examination that included slit lamp examination to grade pterygium. Before starting 5-FU injections, all topical medication was stopped. After four weeks the effects of 5-FU and its efficacy was noted. The patients were reviewed again after six months to note any recurrence. All the collected data was entered and analyzed on Statistical Package for Social Sciences (SPSS) version 20 (IBM Corp., Armonk, NY). Results In our study the mean age of the patients was 37.74 ± 10.15 years, male to female ratio of the patients was 1.06:1. The primary type of pterygium was noted in 54 (53.5%) and recurrent was noted in 47 (46.5%) patients. The efficacy achieved in 88 (87.13%) patients, four had recurrence of pterygium and of 101 patients 26 underwent surgical excision. Conclusion The use of 5-FU is safe and effective for the treatment of pterygium and it can be implemented as a primary treatment especially in the hot temperate zone where it is very common and aggressive with high recurrence rate. 5-FU not only halts its progression but also reduces the size and vascularity thus decreasing the need for surgery and steroid use and preventing recurrence.

Reprogramming of Differentiated Mammalian and Human Retinal Pigment Epithelium: Current Achievements and Prospects

Abstract

Impairment of the homeostatic and functional integrity of the retina and retinal pigment epithelium (RPE) is the main cause of some degenerative diseases of the human eye, which are accompanied by loss of eyesight. Despite the significant progress made over the past decades in the development of new methods for treatment for this pathology, there are still several complications when using surgical methods for correction of eyesight and so far insurmountable limitations in the applications of modern approaches, such as gene therapy and genetic engineering. One of the promising approaches to the treatment of degenerative diseases of the retina may be an approach based on the application of regenerative capacities of its endogenous cells with high plasticity, in particular, of RPE cells and Müller glia. Currently, vertebrate RPE cells are of great interest as a source of new photoreceptors and other neurons in the degrading retina in vivo. In this regard, the possibilities of their direct reprogramming by genetic, epigenetic, and chemical methods and their combination are being investigated. This review focuses on research in gene-directed reprogramming of vertebrate RPE cells into retinal neurons, with detailed analysis of the genes used as the main reprogramming factors, comparative analysis, and extrapolation of experimental data from animals to humans. Also, this review covers studies on the application of alternative approaches to gene-directed reprogramming, such as chemical-mediated reprogramming with the use of cocktails of therapeutic low-molecular-weight compounds and microRNAs. In general, the research results indicate the complexity of the process for direct reprogramming of human RPE cells into retinal neurons. However, taking into account the results of direct reprogramming of vertebrate cells and the accessibility of human RPE cells for various vectors that deliver a variety of molecules to cells, such as transcription factors, chimeric endonucleases, recombinant proteins, and low-weight molecular compounds, the most optimal combination of factors for the successful conversion of human RPE cells to retinal neurons can be suggested.

Choroidal Thickness in Different Types of Inherited Retinal Dystrophies

Purpose

To compare the choroidal thickness among eyes with retinitis pigmentosa (RP), Stargardt disease, Usher syndrome, cone-rod dystrophy, and healthy eyes of sex- and age-matched individuals.

Methods

In this comparative study, 503 eyes with RP (n = 264), cone-rod dystrophy (n = 109), Stargardt disease (n = 76), and Usher syndrome (n = 54) were included. To validate the data, 109 healthy eyes of 56 sex- and age-matched individuals were studied as controls. Choroidal imaging was performed using enhanced depth imaging-optical coherence tomography. Choroidal thickness was measured manually using MATLAB software at 13 points in nasal and temporal directions from the foveal center with the interval of 500 µm and the choroidal area encompassing the measured points was calculated automatically.

Results

The mean age was 36.33 ± 13.07 years (range, 5 to 72 years). The mean choroidal thickness at 13 points of the control eyes was statistically significantly higher than that in eyes with RP (P < 0.001) and Usher syndrome (P< 0.05), but not significantly different from that in eyes with Stargardt disease and cone-rod dystrophy. Among different inherited retinal dystrophies (IRDs), the choroidal thickness was the lowest in eyes with RP (P < 0.001). Choroidal thickness in the subfoveal area correlated negatively with best-corrected visual acuity (r = -0.264, P < 0.001) and the duration of ocular symptoms (r = -0.341, P < 0.001) in all studied IRDs. No significant correlation was observed between the subfoveal choroidal thickness and central macular thickness (r = -0.24, P = 0.576).

Conclusion

Choroidal thinning in four different types of IRDs does not follow a similar pattern and depends on the type of IRD and the duration of ocular symptoms. A larger cohort is required to verify these findings

Updates on the molecular genetics of primary congenital glaucoma (Review)

Primary congenital glaucoma (PCG) is one of the primary causes of blindness in children and is characterized by congenital trabecular meshwork and anterior chamber angle dysplasia. While being a rare condition, PCG severely impairs the quality of life of affected patients. However, the pathogenesis of PCG remains to be fully elucidated. It has previously been indicated that genetic factors serve a critical role in the pathogenesis of PCG, although patients with PCG exhibit significant genetic heterogeneity. Mutations in the cytochrome P450 family 1 subfamily B member 1 gene have been implicated in PCG and further genes that have been reported to be involved in PCG are myocilin, forkhead box C1, collagen type I α1 chain and latent transforming growth factor β binding protein 2. The present review aims to provide an up to date understanding of the genes associated with PCG and the use of molecular technologies in the identification of such genes and mutations. This may pave the way for the development of preventative methods, early diagnosis and improved therapeutic strategies in PCG.

ElVisML: an open data format for the exchange and storage of electrophysiological data in ophthalmology

PURPOSE

The ISCEV standards and recommendations for electrophysiological recordings in ophthalmology define a set of protocols with stimulus parameters, acquisition settings, and recording conditions, to unify the data and enable comparability of results across centers. Up to now, however, there are no standards to define the storage and exchange of such electrophysiological recordings. The aim of this study was to develop an open standard data format for the exchange and storage of visual electrophysiological data (ElVisML).

METHODS

We first surveyed existing data formats for biomedical signals and examined their suitability for electrophysiological data in ophthalmology. We then compared the suitability of text-based and binary formats, as well as encoding in Extensible Markup Language (XML) and character/comma-separated values.

RESULTS

The results of the methodological consideration led to the development of ElVisML with an XML-encoded text-based format. This allows referential integrity, extensibility, the storing of accompanying units, as well as ensuring confidentiality and integrity of the data. A visualization of ElVisML documents (ElVisWeb) has additionally been developed, which facilitates the exchange of recordings on mailing lists and allows open access to data along with published articles.

CONCLUSIONS

The open data format ElVisML ensures the quality, validity, and integrity of electrophysiological data transmission and storage as well as providing manufacturer-independent access and long-term archiving in a future-proof format. Standardization of the format of such neurophysiology data would promote the development of new techniques and open software for the use of neurophysiological data in both clinic and research.

An optimized gene transfection system in WERI-Rb1 cells

The pathogenesis of Rb1 gene inactivation indicates that gene therapy could be a promising treatment for retinoblastoma. An appropriate gene transfer system is the basis for successful gene therapy; however, little attention has been given to an effective gene transfer system for retinoblastoma therapy in previous studies. This study was designed to provide an optimized transgene system for WERI-Rb1 cells (W-RBCs). Green fluorescent protein (GFP) was adopted as a reporter. Four classic viral vectors based on retroviruses, recombinant adeno-associated viruses (rAAV2, rAAV2/1), lentiviruses (LVs) and a novel non-viral vector X-treme HP reagent were adopted for W-RBC gene transfection. The efficacy and cytotoxicity were comprehensively compared among the different vectors through GFP expression and the trypan blue exclusion test. Furthermore, the serum and cell culture status were also optimized for better transfection. Cells transfected by rAAV2/1 expressed more GFP protein and exhibited less staining with trypan blue, compared to the rAAV2 counterpart. However, in comparison to the retroviral group, both the rAAV2/1 and LV groups had considerably less GFP⁺ cells. Interestingly, the X-treme HP presented a similar GFP transfection capacity to the retroviral vector, but with a much lower cytotoxicity. Furthermore, there were more GFP⁺ cells in a suspended condition than that in an adherent culture. Moreover, cells in a serum-positive system expressed more GFP, while cells in a serum-free system showed lower GFP expression and higher cytotoxicity. In conclusion, the retroviral vector and the X-treme HP are effective for W-RBC gene transfection, while the X-treme HP is more preferable due to its lower cytotoxicity. Moreover, the suspended cell culture system is superior to the adherent system, and the serum protects cell viability and facilitates the gene transfection of W-RBCs. This study presents an effective, convenient, and low toxic transfection system for gene delivery in W-RBCs and provides a promising system for further gene therapy of retinoblastoma.

Primate neural retina upregulates IL-6 and IL-10 in response to a herpes simplex vector suggesting the presence of a pro-/anti-inflammatory axis

Injection of herpes simplex virus vectors into the vitreous of primate eyes induces an acute, transient uveitis. The purpose of this study was to characterize innate immune responses of macaque neural retina tissue to the herpes simplex virus type 1-based gene delivery vector hrR3. PCR array analysis demonstrated the induction of the pro-inflammatory cytokine IL-6, as well as the anti-inflammatory cytokine IL-10, following hrR3 exposure. Secretion of IL-6 was detected by ELISA and cone photoreceptors and Muller cells were the predominant IL-6 positive cell types. RNA in situ hybridization confirmed that IL-6 was expressed in photoreceptor and Muller cells. The IL-10 positive cells in the inner nuclear layer were identified as amacrine cells by immunofluorescence staining with calretinin antibody. hrR3 challenge resulted in activation of NFκB (p65) in Muller glial cells, but not in cone photoreceptors, suggesting a novel regulatory mechanism for IL-6 expression in cone cells. hrR3 replication was not required for IL-6 induction or NFκB (p65) activation. These data suggest a pro-inflammatory (IL-6)/anti-inflammatory (IL-10) axis exists in neural retina and the severity of acute posterior uveitis may be determined by this interaction. Further studies are needed to identify the trigger for IL-6 and IL-10 induction and the mechanism of IL-6 induction in cone cells.

Cyclic RGD peptides target human trabecular meshwork cells while ameliorating connective tissue growth factor-induced fibrosis

The major risk factor for primary open-angle glaucoma is increased intraocular pressure stemming from elevated outflow resistance in the trabecular meshwork (TM) region. Integrins play a pivotal role in the TM by influencing its biological properties and growth factor signaling. Pathologic changes in the TM are partially mediated by growth factors like connective tissue growth factor (CTGF). Specific targeting of TM cells could play a critical clinical role by increasing the therapeutic efficacy of nanoparticles, e.g. for nonviral gene delivery. Quantum dots with cyclo(RGDfC) covalently immobilized to their surface effectively targeted cultured TM cells and were rapidly and efficiently endocytosed by binding to α_vβ₃ and α_vβ₅ integrins. Compared to the integrin-overexpressing U87-MG cell line, the association of RGD-modified nanoparticles with the TM cells was significantly higher. Binding and uptake into TM cells was receptor-mediated and suppressible with free peptide. Soluble cyclic RGD peptides effectively attenuated CTGF-mediated effects and inhibited CTGF signaling. Due to their antagonism for αvβ3 and αvβ5 integrins, these cyclic RGD pentapeptides effectively ameliorated the CTGF-induced effects and strongly promoted specific nanoparticle association. Thus, cyclic RGD peptides are powerful multifunctional ligands for both addressing nanomaterials to the TM and interfering with pathologic CTGF signaling upon arrival.

Gene therapy to rescue retinal degeneration caused by mutations in rhodopsin

Retinal gene therapy has proven safe and at least partially successful in clinical trials and in numerous animal models. Gene therapy requires characterization of the progression of the disease and understanding of its genetic cause. Testing gene therapies usually requires an animal model that recapitulates the key features of the human disease, though photoreceptors and cells of the retinal pigment epithelium produced from patient-derived stem cells may provide an alternative test system for retinal gene therapy. Gene therapy also requires a delivery system that introduces the therapeutic gene to the correct cell type and does not cause unintended damage to the tissue. Current systems being tested in the eye are nanoparticles, pseudotyped lentiviruses, and adeno-associated virus (AAV) of various serotypes. Here, we describe the techniques of AAV vector design as well as the in vivo and ex vivo tests necessary for assessing the efficacy of retinal gene therapy to treat retinal degeneration caused by mutations in the rhodopsin gene.

Treatment of ocular disorders by gene therapy

Gene therapy to treat ocular disorders is still starting, and current therapies are primarily experimental, with most human clinical trials still in research state, although beginning to show encouraging results. Currently 33 clinical trials have been approved, are in progress, or have been completed. The most promising results have been obtained in clinical trials of ocular gene therapy for Leber Congenital Amaurosis, which have prompted the study of several ocular diseases that are good candidates to be treated with gene therapy: glaucoma, age-related macular degeneration, retinitis pigmentosa, or choroideremia. The success of gene therapy relies on the efficient delivery of the genetic material to target cells, achieving optimum long-term gene expression. Although viral vectors have been widely used, their potential risk associated mainly with immunogenicity and mutagenesis has promoted the design of non-viral vectors. In this review, the main administration routes and the most studied delivery systems, viral and non-viral, for ocular gene therapy are presented. The primary ocular disease candidates to be treated with gene therapy have been also reviewed, including the genetic basis and the most relevant preclinical and clinical studies.

Stem cells as tools for studying the genetics of inherited retinal degenerations

The ability to provide early clinical intervention for inherited disorders is heavily dependent on knowledge of a patient's disease-causing mutations and the resultant pathophysiologic mechanism(s). Without knowing a patient's disease-causing gene, and how gene mutations alter the health and functionality of affected cells, it would be difficult to develop and deliver patient-specific molecular or small molecule therapies. Many believe that the field of stem cell biology holds the keys to the future development of disease-, patient-, and cell-specific therapies. In the case of the eye, which is susceptible to an extremely common late-onset degenerative disease known as age-related macular degeneration, stem cell-based therapies could increase the quality of life for millions of patients worldwide. Furthermore, autologous, patient-specific induced pluripotent stem cells could be a viable source to treat rare Mendelian retinal degenerative diseases such as retinitis pigmentosa, Stargardt disease, and Best disease, to name a few.

Perceptions and understanding of genetics and genetic eye disease and attitudes to genetic testing and gene therapy in a primary eye care setting

BACKGROUND

Genetic eye pathology represents a significant percentage of the causes of blindness in industrialized countries. This study explores the level of understanding and perceptions of genetics and inherited eye diseases and the attitudes to genetic testing and gene therapy.

METHODS

The study was conducted in two parts. Participant groups included were: undergraduate students of optometry, primary eye care professionals and members of the general public. A preliminary study aimed to understand perceptions and to explore the level of knowledge about genetics in general, eye genetics and gene therapy. A second survey was designed to explore attitudes to genetic testing and gene therapy.

RESULTS

The majority of participants (82%) perceived genetics as an important science. However, none of them showed a high level of understanding of genetics and inherited eye diseases. Undergraduate students and primary eye care professionals were better informed about inherited eye diseases than the general public (p = 0.001). The majority (80%) across all three groups had a positive attitude to genetic testing and gene therapy. There was a lack of knowledge about the genetic services available among all groups of participants.

CONCLUSION

This calls for serious thinking about the level of dissemination of information about genetics and inherited eye diseases. It shows a broadly supportive attitude to genomic medicine among the public. Improving public awareness and education in inherited eye diseases can improve the utility of genetic testing and therapy.

Flicker cone function in normal and day blind sheep: a large animal model for human achromatopsia caused by CNGA3 mutation

PURPOSE

Recently we reported on day blindness in sheep caused by a mutation in the CNGA3 gene, thus making affected sheep a naturally occurring large animal model for therapeutic intervention in CNGA3 achromatopsia patients. The purpose of this study was to characterize flicker cone function in normal and day blind sheep, with the aim of generating a normative data base for ongoing gene therapy studies.

METHODS

Electoretinographic (ERG) cone responses were evoked with full-field conditions in 10 normal, 6 heterozygous carriers and 36 day blind sheep. Following light adaptation (10 min, 30 cd/m(2)), responses were recorded at four increasing light intensities (1, 2.5, 5 and 10 cd s/m(2)). At each of these intensities, a single photopic flash response followed by 8 cone flicker responses (10-80 Hz) was recorded. Results were used to generate a normative data base for the three groups. Differences between day blind and normal control animals were tested in two age-matched groups (n = 10 per group).

RESULTS

The normal sheep cone ERG wave is bipartite in nature, with critical flicker fusion frequency (CFF) >80 Hz. In all four flash intensities, the single photopic flash a-wave and b-wave amplitudes were significantly lower (p < 0.005), and implicit times significantly delayed (p < 0.0001), in day blind animals. In all four flash intensities, CFF values were significantly lower (p < 0.0001) in day blind sheep.

CONCLUSIONS

Cone function is severely depressed in day blind sheep. Our results will provide a normative data base for ongoing gene therapy studies.