Amelioration of Photoreceptor Degeneration by Intravitreal Transplantation of Retinal Progenitor Cells in Rats

Photoreceptor degeneration is a major cause of untreatable blindness worldwide and has recently been targeted by emerging technologies, including cell- and gene-based therapies. Cell types of neural lineage have shown promise for replacing either photoreceptors or retinal pigment epithelial cells following delivery to the subretinal space, while cells of bone marrow lineage have been tested for retinal trophic effects following delivery to the vitreous cavity. Here we explore an alternate approach in which cells from the immature neural retinal are delivered to the vitreous cavity with the goal of providing trophic support for degenerating photoreceptors. Rat and human retinal progenitor cells were transplanted to the vitreous of rats with a well-studied photoreceptor dystrophy, resulting in substantial anatomical preservation and functional rescue of vision. This work provides scientific proof-of-principle for a novel therapeutic approach to photoreceptor degeneration that is currently being evaluated in clinical trials.

Pushing Retinal Imaging Forward: Innovations and Their Clinical Meaning - The 2022 Ophthalmologica Lecture

Retinal imaging has greatly expanded our understanding of various pathological conditions. This article presents a summary of the key points covered during the 2022 Ophthalmologica Lecture held at the Euretina Congress in Hamburg. The first part of the article focuses on the use of optical coherence tomography angiography to examine and comprehend the choroid in age-related macular degeneration (AMD). Subsequently, we delve into the discussion of the "postreceptor neuronal loss" theory in AMD, which was studied using en face structural optical coherence tomography (OCT). Following that, we explore pertinent findings obtained through cross-sectional OCT in retinal and optic nerve diseases, such as AMD, diabetic macular edema, pathologic myopia, central serous chorioretinopathy, and Leber's hereditary optic neuropathy.

Storage stability and antioxidant activities of lutein extracted from yellow silk cocoons (Bombyx mori) in Thailand

This study aimed to determine how different forms of lutein found in nature affected their thermal stability, degradation, and antioxidant activities. The findings show that commercial lutein (CL) degraded faster than silk luteins (SLs) at ≤ 4 °C. The two-stage first-order kinetics of thermal degradation showed that Ea for SLs was 4.6-9.5 times higher than CL. However, at ≥ 25 °C, both the CL and SLs degraded rapidly within one month. SLs had half-life at 4 °C from 10 to 104 wks. FTIR and HRMS analysis revealed that their oxidation products were similar (C₁₈H₂₆O₂: 297 m/z). Based on IC₅₀, antioxidant activities of SLs were superior to CL. The stability and antioxidant capacity of lutein may be influenced by its naturally occurring forms. The naturally occurring forms and unpurified state of lutein can affect its stability and antioxidant activity, which must be considered when storing lutein at different temperatures.

Autophagy Activation Promoted by Pulses of Light and Phytochemicals Counteracting Oxidative Stress during Age-Related Macular Degeneration

The seminal role of autophagy during age-related macular degeneration (AMD) lies in the clearance of a number of reactive oxidative species that generate dysfunctional mitochondria. In fact, reactive oxygen species (ROS) in the retina generate misfolded proteins, alter lipids and sugars composition, disrupt DNA integrity, damage cell organelles and produce retinal inclusions while causing AMD. This explains why autophagy in the retinal pigment epithelium (RPE), mostly at the macular level, is essential in AMD and even in baseline conditions to provide a powerful and fast replacement of oxidized molecules and ROS-damaged mitochondria. When autophagy is impaired within RPE, the deleterious effects of ROS, which are produced in excess also during baseline conditions, are no longer counteracted, and retinal degeneration may occur. Within RPE, autophagy can be induced by various stimuli, such as light and naturally occurring phytochemicals. Light and phytochemicals, in turn, may synergize to enhance autophagy. This may explain the beneficial effects of light pulses combined with phytochemicals both in improving retinal structure and visual acuity. The ability of light to activate some phytochemicals may further extend such a synergism during retinal degeneration. In this way, photosensitive natural compounds may produce light-dependent beneficial antioxidant effects in AMD.

The Essential Role of Light-Induced Autophagy in the Inner Choroid/Outer Retinal Neurovascular Unit in Baseline Conditions and Degeneration

The present article discusses the role of light in altering autophagy, both within the outer retina (retinal pigment epithelium, RPE, and the outer segment of photoreceptors) and the inner choroid (Bruch's membrane, BM, endothelial cells and the pericytes of choriocapillaris, CC). Here autophagy is needed to maintain the high metabolic requirements and to provide the specific physiological activity sub-serving the process of vision. Activation or inhibition of autophagy within RPE strongly depends on light exposure and it is concomitant with activation or inhibition of the outer segment of the photoreceptors. This also recruits CC, which provides blood flow and metabolic substrates. Thus, the inner choroid and outer retina are mutually dependent and their activity is orchestrated by light exposure in order to cope with metabolic demand. This is tuned by the autophagy status, which works as a sort of pivot in the cross-talk within the inner choroid/outer retina neurovascular unit. In degenerative conditions, and mostly during age-related macular degeneration (AMD), autophagy dysfunction occurs in this area to induce cell loss and extracellular aggregates. Therefore, a detailed analysis of the autophagy status encompassing CC, RPE and interposed BM is key to understanding the fine anatomy and altered biochemistry which underlie the onset and progression of AMD.

Effect of Esculetin on Tert-Butyl Hydroperoxide-Induced Oxidative Injury in Retinal Pigment Epithelial Cells In Vitro

Esculetin is a coumarin-derived compound with antioxidant and anti-inflammatory properties. The current study aims to evaluate the therapeutic implications of esculetin on retinal dysfunction and uncover the underlying mechanisms. Tert-butyl hydroperoxide (t-BHP) at a concentration of 300 μM was used to induce oxidative stress in human retinal pigment epithelial cell line (ARPE-19) cells. Esculetin at concentrations below 250 μM did not cause cytotoxicity to ARPE-19 cells. Cell viability analysis confirmed that t-BHP induced oxidative injury of ARPE-19 cells. However, ARPE-19 cells were protected from t-BHP-induced oxidative injury by esculetin in a concentration-dependent manner. As a result of the TUNEL assay to confirm apoptosis, esculetin treatment reduced the number of TUNEL-positive cells. Esculetin down-regulated the expression levels of Bax, Caspase-3, and PARP and up-regulated the expression level of Bcl2. Collectively, this study demonstrates that esculetin exerts potent antioxidant properties in ARPE-19 cells, inhibiting t-BHP-induced apoptosis under the regulation of apoptotic factors.

Differences in long-term progression of atrophy between neovascular and non-neovascular age-related macular degeneration

PURPOSE

To compare enlargement rates over 5 years of follow-up in geographic atrophy (GA) versus macular atrophy (MA) associated with macular neovascularization (MNV).

DESIGN

Retrospective, longitudinal comparative case series.

PARTICIPANTS

Consecutive series of age-related macular degeneration (AMD) patients with GA (dry) or MA with MNV.

METHODS

Atrophic regions on serial registered fundus autofluorescence (FAF) images were semiautomatically delineated and area measurements were recorded every 6±3 months for the first 2 years of follow-up and at yearly intervals up to 5 years.

MAIN OUTCOME MEASURES

Annual raw and square root transformed atrophy growth rates.

RESULTS

117 eyes of 95 patients were included (61 in the GA and 56 in the MA cohort); 100% and 38.5% of eyes completed 2 and 5 years of follow-up, respectively. Mean baseline lesion size was similar between the two groups (raw: 1.74 vs. 1.53 mmˆ2, p = 0.56; sqrt transformed: 1.17 vs. 1.02 mm, p = 0.26). Overall enlargement rates were greater for the GA cohort (raw: 1.72 vs. 1.32 mmˆ2/year, p = 0.002; sqrt transformed: 0.41 vs. 0.33 mm/year; p = 0.03), as well as the area of atrophy growth at 5 years (raw: +8.06 vs. +4.55 mmˆ2, p = 0.001; sqrt transformed: +1.93 vs. +1.38 mm, p = 0.02). Estimated sqrt transformed area was also significantly greater for the GA cohort at 2 years (1.84 vs. 1.67 mm, p = 0.01).

CONCLUSIONS

Presence of MNV was associated with a slower rate of expansion resulting in overall smaller areas of atrophy over time. These findings support the hypothesis that MNV may protect against the progression of atrophy.

Oxidative and Nitrosative Stress in Age-Related Macular Degeneration: A Review of Their Role in Different Stages of Disease

Although the exact pathogenetic mechanisms leading to age-related macular degeneration (AMD) have not been clearly identified, oxidative damage in the retina and choroid due to an imbalance between local oxidants/anti-oxidant systems leading to chronic inflammation could represent the trigger event. Different in vitro and in vivo models have demonstrated the involvement of reactive oxygen species generated in a highly oxidative environment in the development of drusen and retinal pigment epithelium (RPE) changes in the initial pathologic processes of AMD; moreover, recent evidence has highlighted the possible association of oxidative stress and neovascular AMD. Nitric oxide (NO), which is known to play a key role in retinal physiological processes and in the regulation of choroidal blood flow, under pathologic conditions could lead to RPE/photoreceptor degeneration due to the generation of peroxynitrite, a potentially cytotoxic tyrosine-nitrating molecule. Furthermore, the altered expression of the different isoforms of NO synthases could be involved in choroidal microvascular changes leading to neovascularization. The purpose of this review was to investigate the different pathways activated by oxidative/nitrosative stress in the pathogenesis of AMD, focusing on the mechanisms leading to neovascularization and on the possible protective role of anti-vascular endothelial growth factor agents in this context.

Procyanidin B2 and rutin in Ginkgo biloba extracts protect human retinal pigment epithelial (RPE) cells from oxidative stress by modulating Nrf2 and Erk1/2 signalling

Oxidative stress plays an important role in the pathogenesis of human retinal diseases. Ginkgo biloba products are widely consumed herbal supplements that contain ingredients with anti-oxidant potentials. However, the active agents in ginkgo biloba extracts (GBE) are unclear. This study assessed the anti-oxidant effects of 19 natural compounds isolated from GBE to provide a rational basis for their use in preventing retinal diseases. The compounds were tested in retinal pigment epithelial (RPE) cells subjected to tert-butyl hydroperoxide (t-BHP)-induced oxidative stress. Cell viability and intracellular reactive oxygen species (ROS) were assessed and flow cytometry was used to delineate the cell death profile. The expression of nuclear factor erythroid 2-related factor-2 (Nrf2) was activated in RPE cells by t-BHP accompanied with an activation of Erk1/2 signaling. GBE-derived rutin and procyanidin B2 ameliorated t-BHP-induced cell death and promoted cell viability by suppressing intracellular ROS generation. These agents also enhanced Nrf2 expression with activating Erk1/2 signaling in RPE cells. In contrast, the other compounds tested were minimally active and did not prevent the loss of cell viability elicited by t-BHP. The present findings suggest that rutin and procyanidin B2 may have potential therapeutic values in the prevention of retinal diseases induced by oxidative damage.

Optical Coherence Tomography Angiography in Intermediate and Late Age-Related Macular Degeneration: Review of Current Technical Aspects and Applications

Optical coherence tomography angiography (OCTA) is a non-invasive diagnostic instrument that has become indispensable for the management of age-related macular degeneration (AMD). OCTA allows quickly visualizing retinal and choroidal microvasculature, and in the last years, its use has increased in clinical practice as well as for research into the pathophysiology of AMD. This review provides a discussion of new technology and application of OCTA in intermediate and late AMD.

Photoreceptor alteration in intermediate age-related macular degeneration

The aim of this study was to analyze photoreceptor alterations occurring in eyes with intermediate age-related macular degeneration (AMD) and to investigate their associations with choriocapillaris (CC) flow. In this retrospective case-control study, we collected data from 35 eyes with intermediate AMD from 35 patients who had swept source optical coherence tomography structural and angiography imaging obtained. A control group of 35 eyes from 35 healthy subjects was included for comparison. Our main outcome measure for comparison between groups was the normalized reflectivity of en face image segmented at the ellipsoid zone (EZ) level, which was calculated to quantify the photoreceptor damage. OCTA metrics to quantify CC flow signal were also computed. These metrics were measured in a circle centered on the fovea and with a diameter of 5 mm. In intermediate AMD eyes, the macular area occupied by drusen was identified. Therefore, the EZ reflectivity and CC flow signal were separately measured in regions without drusen ("drusen-free" region). Measurements were generated using previously published algorithms. Mean ± SD age was 74.1 ± 6.8 years in the intermediate AMD group and 72.1 ± 6.0 years in the control group (p = 0.206). The normalized EZ reflectivity was 0.76 ± 0.10 in the intermediate AMD group and 0.85 ± 0.08 in the control group (p < .0001). In the "drusen-free" region, the normalized EZ reflectivity was 0.77 ± 0.10 (p < .0001  vs. healthy controls) and was positively correlated with the CC flow signal density (ρ = - 0.340 and p = 0.020). In conclusion, eyes with intermediate AMD exhibit a diffuse reduced EZ normalized reflectivity, and this reduction is correlated with CC flow signal in the regions without drusen. This study supports the concept of the damage of the unit comprised of photoreceptor, CC, and intervening tissues as an early event in AMD.

Intravitreal Dexamethasone Implant as a Sustained Release Drug Delivery Device for the Treatment of Ocular Diseases: A Comprehensive Review of the Literature

Drug delivery into the vitreous chamber remains a great challenge in the pharmaceutical industry due to the complex anatomy and physiology of the eye. Intravitreal injection is the mainstream route of drug administration to the posterior segment of the eye. The purpose of this review is to assess the current literature about the widening use of the intravitreal 0.7 mg dexamethasone (Dex) implant, and to provide a comprehensive collection of all the ocular disorders that benefit from Dex administration. Although anti-vascular endothelial growth-factors (VEGFs) have been largely indicated as a first-choice level, the Dex implant represents an important treatment option, especially in selected cases, such as vitrectomized eyes or patients in whom anti-VEGF failed or are contraindicated. In this article, the safety profile as well as the list of the possible complications related to intravitreal Dex injection are also discussed.

Optical coherence tomography angiography for detection of macular neovascularization associated with atrophy in age-related macular degeneration

PURPOSE

To evaluate the ability of optical coherence tomography angiography (OCTA) to detect macular neovascularization (MNV) in eyes with atrophy compared with fluorescein angiography (FA), indocyanine green angiography (ICGA), and optical coherence tomography (OCT).

METHODS

In this prospective study, eyes with MNV and atrophy (termed macular atrophy or MA) secondary to age-related macular degeneration (AMD), and AMD eyes with geographic atrophy (GA) without MNV underwent multimodal imaging with FA, ICGA, structural OCT, and OCTA. The presence of MNV was determined using all imaging modalities by senior retina specialists and was considered the gold standard reference. Each individual imaging modality was then evaluated independently by two expert readers for the presence of MNV in a masked fashion. Morphologic characteristics of the MNV were evaluated on the custom OCTA slab.

RESULTS

Twenty-one patients with MA+MNV and 21 with GA only were enrolled. Manual segmentation on OCTA allowed detection of the MNV in 95.2% of eyes with MA+MNV and in 4.7% of eyes with GA, showing high specificity (95.2%) and sensitivity (95.2%). FA, ICGA, and OCT detected MNV in 57.1%, 52.3%, and 66.7% of eyes with MA+MNV and in 14.2%, 9.5%, and 42.8% with GA. Sensitivity and specificity were 85.7% and 57.1% for FA, 90.5% and 52.4% for ICGA, and 66.7% and 57.1% for OCT.

CONCLUSIONS

OCTA appears to be superior to other imaging modalities for identification of MNV in eyes with macular atrophy. OCTA should be considered as part of the multimodal imaging evaluation of eyes with atrophy, particularly in the context of clinical trials.

Characteristics of Ophthalmology Trials Registered in ClinicalTrials.gov, 2007-2018

PURPOSE

To perform a comprehensive analysis of characteristics of ophthalmology trials registered in ClinicalTrials.gov.

DESIGN

Cross-sectional study.

METHODS

All 4,203 ophthalmologic clinical trials registered on ClinicalTrials.gov between October 1, 2007, and April 30, 2018, were identified by using medical subject headings (MeSH). Disease condition terms were verified by manual review. Trial characteristics were assessed through frequency calculations. Hazard ratios and 95% confidence intervals were determined for characteristics associated with early discontinuation.

RESULTS

The majority of trials were multiarmed (73.6%), single-site (69.4%), randomized (64.8%), and had <100 enrollees (66.3%). A total of 33% used a data-monitoring committee (DMC), and 50.6% incorporated blinding. Other groups (51.6%) were funded by industry, whereas 2.6% were funded by the US National Institutes of Health (NIH). NIH trials were significantly more likely to address oncologic (NIH = 15.5%, Other = 3%, Industry = 1.5%; P < 0.001) or pediatric disease (NIH = 20.9%, Other = 5.9%, Industry = 1.4%; P < 0.001). Industry-sponsored trials (69.6% of phase 3 trials) were significantly more likely to be randomized (Industry = 68.7%, NIH = 58.9%, Other = 60.8%; P < 0.001) and blinded (Industry = 57.2%, NIH = 42.7%, Other = 43.5%; P < 0.001). A total of 359 trials (8.5%) were discontinued early, and 530 trials (12.6%) had unknown status. Trials were less likely to be discontinued if funded by sources other than industry (hazard ratio [HR], 0.72; 95% confidence interval [CI], 0.55-0.95; P = 0.021) and/or had a DMC (HR, 0.71; 95% CI, 0.55-0.92; P = 0.010).

CONCLUSIONS

Ophthalmology trials in the past decade reveal heterogeneity across study funding sources. NIH trials were more likely to support historically underfunded subspecialties, whereas Industry trials were more likely to face early discontinuation. These trends emphasize the importance of carefully monitored and methodologically sound trials with deliberate funding allocation.

Choroidal Vascularity Index: An In-Depth Analysis of This Novel Optical Coherence Tomography Parameter

Remarkable improvements in optical coherence tomography (OCT) technology have resulted in highly sophisticated, noninvasive machines allowing detailed and advanced morphological evaluation of all retinal and choroidal layers. Postproduction semiautomated imaging analysis with dedicated public-domain software allows precise quantitative analysis of binarized OCT images. In this regard, the choroidal vascularity index (CVI) is emerging as a new imaging tool for the measurement and analysis of the choroidal vascular system by quantifying both luminal and stromal choroidal components. Numerous reports have been published so far regarding CVI and its potential applications in healthy eyes as well as in the evaluation and management of several chorioretinal diseases. Current literature suggests that CVI has a lesser variability and is influenced by fewer physiologic factors as compared to choroidal thickness. It can be considered a relatively stable parameter for evaluating the changes in the choroidal vasculature. In this review, the principles and the applications of this advanced imaging modality for studying and understanding the contributing role of choroid in retinal and optic nerve diseases are discussed. Potential advances that may allow the widespread adoption of this tool in the routine clinical practice are also presented.

Quantitative choriocapillaris evaluation in intermediate age-related macular degeneration by swept-source optical coherence tomography angiography

PURPOSE

To investigate choriocapillaris (CC) perfusion, by evaluating flow voids (FV), in eyes with intermediate age-related macular degeneration (iAMD) using swept-source optical coherence tomography angiography (SS-OCT-A).

METHODS

Patients with bilateral or unilateral iAMD and normal controls underwent SS-OCT and OCT-A examination. Choriocapillaris (CC) FVs were quantitatively assessed on OCT-A images using matlab (version 2017b; MathWorks, Natick, MA, USA), after a preprocessing aimed at compensating for CC attenuation artefacts. Three different thresholds [1 standard deviation (SD), 1.25 SD and 1.5 SD] were applied. Final FV percentage (FV%) was calculated as the ratio between area with absent flow and total scanned area.

RESULTS

Of 41 patients with iAMD and 16 normal subjects enrolled in the study, 39 eyes (39 patients) with iAMD and all 16 normal eyes (16 control subjects) were included in the final analysis. Mean FV% (1 SD) was 13.45 ± 0.66 in controls, 14.19 ± 1.23 in bilateral iAMD and 14.21 ± 0.99 in unilateral iAMD (p = 0.03, for difference between controls and bilateral iAMD). Mean FV% (1.25 SD) was 6.55 ± 0.65 in controls, 7.33 ± 1.4 in bilateral iAMD and 7.06 ± 1.4 in unilateral iAMD (p = 0.048, for difference between controls and bilateral iAMD). Mean FV% (1.5 SD) was 2.71 ± 0.82 in controls, 2.55 ± 1.12 in bilateral iAMD and 3.25 ± 1.17 in unilateral iAMD (p = 0.038, for difference between bilateral and unilateral iAMD).

CONCLUSION

A significantly higher FV% was found in patients with iAMD versus controls. A higher trend in FV% was found in unilateral iAMD (with neovascular AMD in the fellow eye) versus bilateral iAMD, when applying the lowest threshold. Further, larger and longitudinal studies are needed to confirm this data.

Treatments for dry age-related macular degeneration and Stargardt disease: a systematic review

BACKGROUND

Age-related macular degeneration (AMD) is the leading cause of visual loss in older people. Advanced AMD takes two forms, neovascular (wet) and atrophic (dry). Stargardt disease (STGD) is the commonest form of inherited macular dystrophy.

OBJECTIVE

To carry out a systematic review of treatments for dry AMD and STGD, and to identify emerging treatments where future NIHR research might be commissioned.

DESIGN

Systematic review.

METHODS

We searched MEDLINE, EMBASE, Web of Science and The Cochrane Library from 2005 to 13 July 2017 for reviews, journal articles and meeting abstracts. We looked for studies of interventions that aim to preserve or restore vision in people with dry AMD or STGD. The most important outcomes are those that matter to patients: visual acuity (VA), contrast sensitivity, reading speed, ability to drive, adverse effects of treatment, quality of life, progression of disease and patient preference. However, visual loss is a late event and intermediate predictors of future decline were accepted if there was good evidence that they are strong predictors of subsequent visual outcomes. These include changes detectable by investigation, but not necessarily noticed by people with AMD or STGD. ClinicalTrials.gov, the World Health Organization search portal and the UK Clinical Trials gateway were searched for ongoing and recently completed clinical trials.

RESULTS

The titles and abstracts of 7948 articles were screened for inclusion. The full text of 398 articles were obtained for further screening and checking of references and 112 articles were included in the final report. Overall, there were disappointingly few good-quality studies (including of sufficient size and duration) reporting useful outcomes, particularly in STGD. However we did identify a number of promising research topics, including drug treatments, stem cells, new forms of laser treatment, and implantable intraocular lens telescopes. In many cases, research is already under way, funded by industry or governments.

LIMITATIONS

In AMD, the main limitation came from the poor quality of much of the evidence. Many studies used VA as their main outcome despite not having sufficient duration to observe changes. The evidence on treatments for STGD is sparse. Most studies tested interventions with no comparison group, were far too short term, and the quality of some studies was poor.

FUTURE WORK

We think that the topics on which the Health Technology Assessment (HTA) and Efficacy Mechanism and Evaluation (EME) programmes might consider commissioning primary research are in STGD, a HTA trial of fenretinide (ReVision Therapeutics, San Diego, CA, USA), a visual cycle inhibitor, and EME research into the value of lutein and zeaxanthin supplements, using short-term measures of retinal function. In AMD, we suggest trials of fenretinide and of a potent statin. There is epidemiological evidence from the USA that the drug, levodopa, used for treating Parkinson's disease, may reduce the incidence of AMD. We suggest that similar research should be carried out using the large general practice databases in the UK. Ideally, future research should be at earlier stages in both diseases, before vision is impaired, using sensitive measures of macular function. This may require early detection of AMD by screening.

STUDY REGISTRATION

This study is registered as PROSPERO CRD42016038708.

FUNDING

The National Institute for Health Research HTA programme.

Topographic Analysis of the Choriocapillaris in Intermediate Age-related Macular Degeneration

PURPOSE

To quantitate regional differences in the choriocapillaris (CC) of patients with intermediate age-related macular degeneration (iAMD), using swept-source optical coherence tomography angiography (SS-OCTA) imaging.

DESIGN

Cross-sectional study.

METHODS

Subjects were imaged with the SS-OCTA system (PLEX Elite 9000, Carl Zeiss Meditec Inc, Dublin, California, USA). The CC en face images were first compensated for the signal attenuation caused by drusen by using the structural information from the same slab. Subsequently, for each eye, 2 compensated CC en face images generated from 2 different OCTA volume scan sets were registered and averaged. The averaged CC images were then exported to ImageJ and binarized for subsequent quantitative analysis. In addition to the analysis of the whole averaged CC en face image in iAMD eyes, quantitative analysis was also performed in 3 different regions: (1) drusen region, (2) 150-μm-wide ring around the drusen border, and (3) drusen-free region.

RESULTS

Thirty eyes (30 patients) with iAMD and 30 healthy eyes from 30 controls were enrolled. Compared with controls, iAMD eyes displayed a lower number of signal voids (median and interquartile range [IQR]: 2561 and 2343-2746 vs 2734 and 2558-2834; P = .013), a greater signal void average size (median, IQR: 581.9 μm², 466.1-726.9 μm² vs 503.8 μm², 429.1-576.8 μm²; P = .027), and a greater total signal void area (median, IQR: 26.0%, 22.1%-29.6% vs 23.8%, 21.2%-26.4%; P = .038). In multiple regression analysis, the presence of iAMD was not significantly associated with any of the CC variables. By contrast, the drusen region area was significantly associated with CC alterations. In the evaluation of the iAMD group, both the area underneath drusen and the 150-μm-wide ring region around drusen were characterized by an increased total signal void area (P = .005 and P = .045, respectively) vs the drusen-free region.

CONCLUSIONS

Intermediate AMD eyes demonstrated increased CC flow impairment, which co-localizes to the area of CC beneath and immediately surrounding drusen.

PEDF protects human retinal pigment epithelial cells against oxidative stress via upregulation of UCP2 expression

To investigate the protective function of pigment epithelium-derived factor (PEDF) against oxidative stress (OS) in ARPE-19 cells, ARPE-19 cells were divided into different OS groups and treated with various concentrations of H₂O₂ (0, 75, 150 and 200 µmol/l) for 24 h. To establish the protective group, 200 ng/ml of PEDF was administered to ARPE-19 cells. Cell Counting Kit-8 assays and cell growth curve experiments were performed to determine levels of cell viability; lactate dehydrogenase and propidium iodide (PI) staining assays were also performed. The expression levels of genes associated with apoptosis as well as uncoupling protein 2 (UCP2) were detected by reverse transcription-quantitative, or semi-quantitative polymerase chain reaction. Furthermore, an OS injury animal model was established in both C57BL/6 and BALB/c mice via injection of 5 µg of PEDF in the vitreous cavity and subsequent injection of 150 µM H₂O₂ following a 24 h time interval. Hematoxylin and eosin (H&E) staining, as well as UCP2 immunofluorescent labeling were also performed. One-way analysis of variance was used to determine statistically significant differences, followed by multiple comparison analysis using the Newman Keuls method. The results of cell viability assays demonstrated that the numbers of apoptotic cells were increased following treatment with H₂O₂ in a dose-dependent manner; however, this effect was reversed following treatment with PEDF. The expression levels of caspase 3 and B cell lymphoma (Bcl2) associated X genes associated with apoptosis were inhibited, whereas levels of the anti-apoptotic gene Bcl2 were enhanced following treatment with PEDF in different passages of ARPE-19 cells. Significant differences were demonstrated in the levels of UCP2 gene expression between the PEDF+ H₂O₂ treated group and cells treated with H₂O₂ alone. Labeling of the UCP2 detector in the confocal images demonstrated decreased UCP2 protein staining in the retinal pigment epithelium (RPE) cells and RPE layers following H₂O₂ injury; however, this effect was inhibited following treatment with PEDF. H&E staining was performed to investigate the thickness of the RPE layers, and the results revealed that thicknesses were significantly increased in sections treated with PEDF during OS, due to increased numbers of RPE cells. Furthermore, PEDF was demonstrated to increase UCP2 gene expression in ARPE-19 cells and animal RPE layers under OS, which suggested that PEDF may protect RPE cells and tissues during oxidative injury.

Impact of Choriocapillaris Flow on Multifocal Electroretinography in Intermediate Age-Related Macular Degeneration Eyes

Purpose

To investigate the relationship between perfusion of the choriocapillaris (CC) and macular function in eyes with intermediate age-related macular degeneration.

Methods

In this prospective, observational, cross-sectional study, macular optical coherence tomography angiography images and multifocal electroretinograms were obtained in 20 eyes with intermediate age-related macular degeneration from 20 patients. The main outcome measures were (1) the percent nonperfused choriocapillaris area (PNPCA), which represents a measure of the total area of CC vascular dropout, and (2) the average size of the CC signal voids, which represent contiguous regions of CC dropout. Furthermore, amplitude and implicit time of multifocal electroretinograms N1 and P1 waves in the two central rings (R1 and R2) were included in the analysis.

Results

Of the 20 patients enrolled, only 17 eyes from 17 patients (13 women) were included in this analysis. Three patients were excluded because of poor scan quality. Mean ± SD age was 75.1 ± 7.9 years (range, 62-89 years). The best corrected visual acuity was 0.17 ± 0.13 logarithm of the minimum angle of resolution. In univariate analysis, both the PNPCA and average signal void size were found to have a significant direct relationship with N1 implicit time in the R2 ring (P = 0.006 and P = 0.035, respectively). Neither PNPCA nor the average signal void size was associated with P1 or N1 implicit times in R1.

Conclusions

In intermediate age-related macular degeneration eyes, PNPCA and average signal void size are related to N1 multifocal electroretinogram implicit times, which suggests an association between CC perfusion and photoreceptor function.

Postreceptor Neuronal Loss in Intermediate Age-related Macular Degeneration

PURPOSE

To investigate the relationship between ganglion cell complex (GCC) thickness and photoreceptor alterations in eyes with intermediate age-related macular degeneration (AMD).

DESIGN

Retrospective case-control study.

METHODS

We collected data from 68 eyes with intermediate AMD from 68 patients with spectral-domain optical coherence tomography (SDOCT) imaging. A control group of 50 eyes from 50 healthy subjects was included for comparison. Our main outcome measures for comparison between groups were (1) the average and minimum GCC thickness and (2) the "normalized" reflectivity of the ellipsoid zone (EZ) en face image.

RESULTS

The average and minimum GCC thicknesses were thinner in AMD patients (69.54 ± 9.30 μm and 63.22 ± 14.11 μm, respectively) than in healthy controls (78.57 ± 6.28 μm and 76.28 ± 6.85 μm, P < .0001 and P < .0001, respectively). Agreement was found to be excellent in the "normalized" EZ reflectivity assessment (intraclass correlation coefficient = 0.986, coefficient of variation = 1.11). The EZ "normalized" reflectivity was 0.67 ± 0.11 in controls and 0.61 ± 0.09 in the AMD group (P = .006). In univariate analysis, EZ "normalized" reflectivity was found to have a significant direct relationship with average (P < .0001) and minimum (P < .0001) GCC thickness in AMD patients, but not in controls (P = .852 and P = .892, respectively).

CONCLUSIONS

Eyes with intermediate AMD exhibit GCC thinning, as well as a reduced EZ "normalized" reflectivity, and these parameters are correlated. This study supports the concept of postreceptor retinal neuronal loss as a contributor to retinal thinning in intermediate AMD.

The role and therapeutic potential of melatonin in age-related ocular diseases

The eye is continuously exposed to solar UV radiation and pollutants, making it prone to oxidative attacks. In fact, oxidative damage is a major cause of age-related ocular diseases including cataract, glaucoma, age-related macular degeneration, and diabetic retinopathy. As the nature of lens cells, trabecular meshwork cells, retinal ganglion cells, retinal pigment epithelial cells, and photoreceptors is postmitotic, autophagy plays a critical role in their cellular homeostasis. In age-related ocular diseases, this process is impaired, and thus, oxidative damage becomes irreversible. Other conditions such as low-grade chronic inflammation and angiogenesis also contribute to the development of retinal diseases (glaucoma, age-related macular degeneration and diabetic retinopathy). As melatonin is known to have remarkable qualities such as antioxidant/antinitridergic, mitochondrial protector, autophagy modulator, anti-inflammatory, and anti-angiogenic, it can represent a powerful tool to counteract all these diseases. The present review analyzes the role and therapeutic potential of melatonin in age-related ocular diseases, focusing on nitro-oxidative stress, autophagy, inflammation, and angiogenesis mechanisms.

DNA damage response and autophagy in the degeneration of retinal pigment epithelial cells-Implications for age-related macular degeneration (AMD)

In this review we will discuss the links between autophagy, a mechanism involved in the maintenance of cellular homeostasis and controlling cellular waste management, and the DNA damage response (DDR), comprising various mechanisms preserving the integrity and stability of the genome. A reduced autophagy capacity in retinal pigment epithelium has been shown to be connected in the pathogenesis of age-related macular degeneration (AMD), an eye disease. This degenerative disease is a major and increasing cause of vision loss in the elderly in developed countries, primarily due to the profound accumulation of intra- and extracellular waste: lipofuscin and drusen. An abundance of reactive oxygen species is produced in the retina since this tissue has a high oxygen demand and contains mitochondria-rich cells. The retina is exposed to light and it also houses many photoactive molecules. These factors are clearly reflected in both the autophagy and DNA damage rates, and in both nuclear and mitochondrial genomes. It remains to be revealed whether DNA damage and DDR capacity have a more direct role in the development of AMD.

Timing of Antioxidant Gene Therapy: Implications for Treating Dry AMD

Purpose

To investigate whether antioxidant gene therapy protects the structure and function of retina in a murine model of RPE atrophy, and to determine whether antioxidant gene therapy can prevent degeneration once it has begun.

Methods

We induced mitochondrial oxidative stress in RPE by conditional deletion of Sod2, the gene for manganese superoxide dismutase (MnSOD). These mice exhibited localized atrophy of the RPE and overlying photoreceptors. We restored Sod2 to the RPE of one eye using adeno-associated virus (AAV) by subretinal injection at an early (6 weeks) and a late stage (6 months), injecting the other eye with an AAV vector expressing green fluorescent protein (GFP). Retinal degeneration was monitored over a period of 9 months by electroretinography (ERG) and spectral-domain optical coherence tomography (SD-OCT). Immunohistochemical and histologic analyses were conducted to measure oxidative stress markers and to visualize retinal structure.

Results

One month after delivery, the AAV-Sod2 injection resulted in production of MnSod in the RPE and negligible expression in the neural retina. Electroretinography and OCT suggested no adverse effects due to increased expression of MnSOD or subretinal injection. Decrease in the ERG response and thinning retinal thickness was significantly delayed in eyes with early treatment with the Sod2 vector, but treatment at 6 months of age did not affect the ERG decline seen in these mice.

Conclusions

We conclude that antioxidant gene therapy may be effective in preventing the detrimental effects of oxidative stress, but may not be beneficial once substantial tissue damage has occurred.

Epidemiology of age-related macular degeneration (AMD): associations with cardiovascular disease phenotypes and lipid factors

Age-related macular degeneration (AMD) is the leading cause of irreversible blindness in adults over 50 years old. Genetic, epidemiological, and molecular studies are beginning to unravel the intricate mechanisms underlying this complex disease, which implicate the lipid-cholesterol pathway in the pathophysiology of disease development and progression. Many of the genetic and environmental risk factors associated with AMD are also associated with other complex degenerative diseases of advanced age, including cardiovascular disease (CVD). In this review, we present epidemiological findings associating AMD with a variety of lipid pathway genes, cardiovascular phenotypes, and relevant environmental exposures. Despite a number of studies showing significant associations between AMD and these lipid/cardiovascular factors, results have been mixed and as such the relationships among these factors and AMD remain controversial. It is imperative that researchers not only tease out the various contributions of such factors to AMD development but also the connections between AMD and CVD to develop optimal precision medical care for aging adults.

Norbixin Protects Retinal Pigmented Epithelium Cells and Photoreceptors against A2E-Mediated Phototoxicity In Vitro and In Vivo

The accumulation of N-retinylidene-N-retinylethanolamine (A2E, a toxic by-product of the visual pigment cycle) in the retinal pigment epithelium (RPE) is a major cause of visual impairment in the elderly. Photooxidation of A2E results in retinal pigment epithelium degeneration followed by that of associated photoreceptors. Present treatments rely on nutrient supplementation with antioxidants. 9’-cis-Norbixin (a natural diapocarotenoid, 97% purity) was prepared from Bixa orellana seeds. It was first evaluated in primary cultures of porcine retinal pigment epithelium cells challenged with A2E and illuminated with blue light, and it provided an improved photo-protection as compared with lutein or zeaxanthin. In Abca4^-/-Rdh8^-/- mice (a model of dry AMD), intravitreally-injected norbixin maintained the electroretinogram and protected photoreceptors against light damage. In a standard rat blue-light model of photodamage, norbixin was at least equally as active as phenyl-N-tert-butylnitrone, a free radical spin-trap. Chronic experiments performed with Abca4^-/-Rdh8^-/- mice treated orally for 3 months with norbixin showed a reduced A2E accumulation in the retina. Norbixin appears promising for developing an oral treatment of macular degeneration. A drug candidate (BIO201) with 9’-cis-norbixin as the active principle ingredient is under development, and its potential will be assessed in a forthcoming clinical trial.

Apigenin Attenuates Oxidative Injury in ARPE-19 Cells thorough Activation of Nrf2 Pathway

The current study was aimed at evaluating the therapeutic implication of apigenin and to elucidate the underlying mechanism. The tert-butyl hydroperoxide (t-BHP) at 200 μM was used to induce oxidative stress-associated injury in ARPE-19 cells. Apigenin at concentrations less than 800 μM did not cause cytotoxic effects on ARPE-19 cells. Cell viability assay showed that apigenin at 200 μM significantly promoted cell survival in t-BHP-treated ARPE-19 cells. Additionally, apigenin at 100 μM significantly protected ARPE-19 cells from t-BHP-induced apoptosis. Molecular examinations demonstrated that apigenin at 400 μM significantly upregulated the mRNA and protein expression of Nrf2 and stimulated its nuclear translocation in ARPE-19 cells treated with or without t-BHP. Apigenin 400 μM also significantly elevated the expression of HO-1, NQO1, and GCLM at both mRNA and protein levels in the presence or absence of t-BHP. Furthermore, apigenin at 400 μM significantly increased the activities of SOD, CAT, GSH-PX, and T-AOC and reduced the levels of ROS and MDA in t-BHP-treated ARPE-19 cells. However, these effects of apigenin were all abolished by being transfected with Nrf2 siRNA. Collectively, our current data indicated that apigenin exerted potent antioxidant properties in ARPE-19 cells challenged with t-BHP, which were dependent on activation of Nrf2 signaling.

The Complement Regulatory Protein CD46 Deficient Mouse Spontaneously Develops Dry-Type Age-Related Macular Degeneration-Like Phenotype

In the mouse, membrane cofactor protein (CD46), a key regulator of the alternative pathway of the complement system, is only expressed in the eye and on the inner acrosomal membrane of spermatozoa. We noted that although Cd46(-/-) mice have normal systemic alternative pathway activating ability, lack of CD46 leads to dysregulated complement activation in the eye, as evidenced by increased deposition of C5b-9 in the retinal pigment epithelium (RPE) and choroid. A knockout of CD46 induced the following cardinal features of human dry age-related macular degeneration (AMD) in 12-month-old male and female mice: accumulation of autofluorescent material in and hypertrophy of the RPE, dense deposits in and thickening of Bruch's membrane, loss of photoreceptors, cells in subretinal space, and a reduction of choroidal vessels. Collectively, our results demonstrate spontaneous age-related degenerative changes in the retina, RPE, and choroid of Cd46(-/-) mice that are consistent with human dry AMD. These findings provide the exciting possibility of using Cd46(-/-) mice as a convenient and reliable animal model for dry AMD. Having such a relatively straight-forward model for dry AMD should provide valuable insights into pathogenesis and a test model system for novel drug targets. More important, tissue-specific expression of CD46 gives the Cd46(-/-) mouse model of dry AMD a unique advantage over other mouse models using knockout strains.

Drug discovery in ophthalmology: past success, present challenges, and future opportunities

BACKGROUND

Drug discovery has undergone major transformations in the last century, progressing from the recognition and refinement of natural products with therapeutic benefit, to the systematic screening of molecular libraries on whole organisms or cell lines and more recently to a more target-based approach driven by greater knowledge of the physiological and pathological pathways involved. Despite this evolution increasing challenges within the drug discovery industry are causing escalating rates of failure of development pipelines.

DISCUSSION

We review the challenges facing the drug discovery industry, and discuss what attempts are being made to increase the productivity of drug development, including a refocusing on the study of the basic biology of the disease, and an embracing of the concept of 'translational research'. We consider what ophthalmic drug discovery can learn from the sector in general and discuss strategies to overcome the present limitations. This includes advances in the understanding of the pathogenesis of disease; improvements in animal models of human disease; improvements in ophthalmic drug delivery and attempts at patient stratification within clinical trials. As we look to the future, we argue that investment in ophthalmic drug development must continue to cover the whole translational spectrum (from 'bench to bedside and back again') with recognition that both biological discovery and clinical understanding will drive drug discovery, providing safe and effective therapies for ocular disease.

Quercetin phospholipid complex significantly protects against oxidative injury in ARPE-19 cells associated with activation of Nrf2 pathway

Age-related macular degeneration (AMD) is a major cause of blindness worldwide. Oxidative stress plays a crucial role in the pathogenesis of dry AMD. Quercetin has potent anti-oxidative activities, but poor bioavailability limits its therapeutic application. Herein, we prepared the phospholipid complex of quercetin (quercetin-PC), characterized its structure by differential scanning calorimetry, infrared spectrum and x-ray diffraction. Quercetin-PC had equilibrium solubility of 38.36 and 1351.27μg/ml in water and chloroform, respectively, which was remarkably higher than those of quercetin alone. Then we established hydrogen peroxide (H2O2)-induced oxidative injury model in human ARPE-19 cells to examine the effects of quercetin-PC. Quercetin-PC, stronger than quercetin, promoted cell proliferation, and the proliferation rate was increased to be 78.89% when treated with Quercetin-PC at 400μM. Moreover, quercetin-PC effectively prevented ARPE-19 cells from apoptosis, and the apoptotic rate was reduced to be 3.1% when treated with Quercetin-PC at 200μM. In addition, quercetin-PC at 200μM significantly increased the activities of SOD, CAT and GSH-PX, and reduced the levels of reactive oxygen species and MDA in H2O2-treated ARPE-19 cells, but quercetin at 200μM failed to do so. Molecular examinations revealed that quercetin-PC at 200μM significantly activated Nrf2 nuclear translocation and significantly enhanced the expression of target genes HO-1, NQO-1 and GCL by different folds at both mRNA and protein levels. Our current data collectively indicated that quercetin-PC had stronger protective effects against oxidative-induced damages in ARPE-19 cells, which was associated with activation of Nrf2 pathway and its target genes implicated in antioxidant defense.

Age-related macular degeneration: a complementopathy?

Age-related macular degeneration (AMD) is a progressive eye disease affecting many elderly individuals. It has a multifactorial pathogenesis and is associated with numerous environmental (e.g. smoking, light and nutrition) and genetic risk factors. A breakthrough in the mechanisms causing AMD is emerging; the involvement of the alternative pathway of the complement system appears to play a pivotal role. This has led to the statement that AMD is a disease caused by a hyperactive complement system, allowing the term 'complementopathy' to define it more precisely. Abundant evidence includes: the identification of drusen components as activators of complement, immunohistochemical data showing the presence of many species of the complement system in the retinal pigment epithelium-Bruch's membrane-choroidocapillary region of AMD eyes, a strong association of AMD with certain genetic complement protein variants, raised complement levels in blood from AMD patients and the preliminary successful treatments of geographic atrophy with complement factor D (FD) inhibitors. FD is the rate-limiting enzyme of the alternative complement pathway, and is produced by adipose tissue. Recent findings suggest that nutrition may play a role in controlling the level of FD in the circulation. Addressing modifiable risk factors such as smoking and nutrition may thus offer opportunities for the prevention of AMD.

Emerging therapeutic options in age-related macular degeneration

Intravitreal injection of anti-VEGF drugs currently represents the standard of treatment for exudative age-related macular degeneration. Several therapeutic options including steroids, inhibitors of complement factors, anti-platelet-derived growth factor agents, new anti-VEGF drugs, designed ankyrin repeat proteins, sustained drug delivery devices as an alternative to intravitreal injections and encapsulated cell technology are the objects of several studies and trials worldwide in association with anti-VEGF therapy or not. Expectations are that such efforts will help overcome limitations of current therapy with anti-VEGF, extending the duration of effects and hopefully contributing to the regression of neovascular lesions.

Lutein and Factor D: two intriguing players in the field of age-related macular degeneration

Age-related macular degeneration (AMD) is a progressive eye disease that impairs central vision among elderly populations in Western, industrialized countries. In this review we will focus on the role of factor D (FD) and lutein in AMD. FD is a rate-limiting enzyme of the alternative complement activation pathway that may play an important role in the development of AMD. Several independent studies have shown a significant increase in the level of a number of complement factors of the alternative pathway, including factor D in the blood of AMD patients as compared to healthy individuals, which suggests a systemic involvement in the pathogenesis of AMD. FD, also called adipsin, is mainly produced by adipose tissue. Besides playing a role in the activation of the alternative pathway, FD is also known to regulate the immune system. Of interest is our preliminary finding that lutein supplementation of early AMD cases was shown to lower the level of systemic FD. If confirmed, these findings provide further support for the application of anti-factor D intervention as a new approach to control the development of this disease.