Soft Drusen in Age-Related Macular Degeneration: Biology and Targeting Via the Oil Spill Strategies

PATHWAYS TO GEOGRAPHIC ATROPHY IN NONNEOVASCULAR AGE-RELATED MACULAR DEGENERATION

PURPOSE

To characterize and quantify the precursor lesions of geographic atrophy in eyes with age-related macular degeneration.

METHODS

A retrospective study of eyes with a minimum of 6-month follow-up before developing geographic atrophy. Evaluations included color and autofluorescence imaging, along with spectral-domain optical coherence tomography, employing definitions from the Consensus of Atrophy Meeting Group and Consensus on Neovascular Age-Related Macular Degeneration Nomenclature Study Group.

RESULTS

There were 55 eyes of 44 patients, who had a mean age of 81.3 years at onset of atrophy; 35 (63.6%) were female. The mean duration of follow-up before and after the advent of geographic atrophy was 4.9 years and 1.2 years, respectively. Geographic atrophy was preceded by collapse of a druse in 41 eyes (74.5%). Of these, 29 (70.7%) were drusenoid pigment epithelial detachments. Among the eyes with regressing drusen, there were 9 with overlying vitelliform deposit, and all had concurrent subretinal drusenoid deposit; however, 19 of 30 eyes with no vitelliform deposit overlying the druse had concurrent subretinal drusenoid deposit, a difference that was significant ( P < 0.001). Regression of subretinal drusenoid deposit was found in 4 eyes (7.3%), regression of vitelliform deposit associated with subretinal drusenoid deposit in 5 (9.1%), and regression of vitelliform deposit in eyes concurrently harboring drusen was found in 3 (5.4%) and regression of vitelliform deposit alone in 2 (3.6%) at the site of eventual development of geographic atrophy.

CONCLUSION

Geographic atrophy appears to develop from multiple pathways as manifested by the many precursor lesions, all various forms of extracellular deposit, that upon regression, result in a common end-stage appearance.

Acetyl-CoA carboxylase Inhibition increases retinal pigment epithelial cell fatty acid flux and restricts apolipoprotein efflux

Lipid-rich deposits called drusen accumulate under the retinal pigment epithelium (RPE) in the eyes of patients with age-related macular degeneration (AMD) and Sorsby's fundus dystrophy (SFD). Drusen may contribute to photoreceptor and RPE degeneration in these blinding diseases. We hypothesize that stimulating β-oxidation of fatty acids could decrease the availability of lipid with which RPE cells can generate drusen. Inhibitors of acetyl-CoA carboxylase (ACC) stimulate β-oxidation and diminish lipid accumulation in fatty liver disease. In this report we test the hypothesis that an ACC inhibitor, Firsocostat, can diminish lipid deposition by RPE cells. We probed metabolism and cellular function in mouse RPE-choroid tissue and in cultured human RPE cells. We used 13C6-glucose, 13C16-palmitate, and gas chromatography-linked mass spectrometry to monitor effects of Firsocostat on glycolytic, Krebs cycle, and fatty acid metabolism. We quantified lipid abundance, apolipoprotein E (ApoE) and vascular endothelial growth factor (VEGF) release using liquid chromatography-mass spectrometry, enzyme-linked immunosorbent assays and localized ApoE deposits by immunostaining. RPE barrier function was assessed by trans-epithelial electrical resistance (TEER). Firsocostat-mediated ACC inhibition increases β-oxidation, decreases intracellular lipid levels, diminishes lipoprotein release, and increases TEER. When human serum or outer segments are used to stimulate lipoprotein release, fewer lipoproteins are released in the presence of either lipid source and Firsocostat. In a culture model of SFD, Firsocostat stimulates fatty acid oxidation, increases TEER, and decreases ApoE release. We conclude that Firsocostat remodels RPE metabolism and can limit lipid deposition. This suggests that ACC inhibition could be an effective strategy for diminishing pathologic drusen in the eyes of patients with AMD or SFD.

Hyperautofluorescent material inside areas of macular atrophy may reveal non-lipofuscin fluorophores in late stage AMD

PURPOSE

To characterize fundus autofluorescence (FAF) in complete (cRORA) and incomplete retinal pigment epithelium and outer retinal atrophy (iRORA) by fluorescence lifetime imaging ophthalmology (FLIO).

METHODS

Overall, 98 macular atrophy (MA) lesions in 42 eyes of 37 age-related macular degeneration (AMD) patients (mean age: 80.9 ± 5.8 years), 25 of them classified as iRORA and 73 as cRORA by OCT, were investigated by FLIO in a short (SSC: 498-560 nm) and a long wavelength channel (LSC: 560-720 nm). Differences of FAF lifetimes and peak emission wavelength (PEW) between atrophic lesions and intact retinal pigment epithelium (RPE) in the outer ring of the ETDRS grid were considered.

RESULTS

FAF lifetimes in MA were longer and PEW were significantly (p < 0.001) shorter than in intact RPE by 112 ± 78 ps (SSC), 91 ± 64 ps (LSC), 27 ± 18 nm (PEW) in iRORA and by 227 ± 112 ps (SSC), 167 ± 81 ps (LSC), and 54 ± 17 nm (PEW) in cRORA. 37% of iRORA and 24% of cRORA were hyperautofluorescent in SSC. Persistent sub-RPE-BL material in MA was newly found as a hyperautofluorescent entity with lifetimes considerably longer than that of drusen and RPE.

CONCLUSIONS

Despite RPE and, thus, lipofuscin are greatly absent in MA, considerable FAF, preferably at short wavelengths, was found in those lesions. Drusen, persistent sub-RPE-BL material, basal laminar deposits, persistent activated RPE, and sclera were identified as putative sources of this fluorescence. FLIO can help to characterize respective fluorophores.

The Circadian Clock of Müller Glia Is Necessary for Retinal Homeostasis and Neuronal Survival

Biological processes throughout the body are orchestrated in time through the regulation of local circadian clocks. The retina is among the most metabolically active tissues, with demands depending greatly on the light/dark cycle. Most cell types within the retina are known to express the circadian clock in rodents; however, retinal clock expression in the human has not previously been localized. Moreover, the effect of local circadian clock dysfunction on retinal homeostasis is incompletely understood. We demonstrate an age-dependent decline in circadian clock gene and protein expression in the human retina. Using an animal model of targeted Bmal1 deficiency, we identify the circadian clock of the retinal Müller glia as essential for neuronal survival, vascular integrity, and retinal function. These results suggest a potential role for the local retinal circadian clock within the Müller glia in age-related retinal disease and retinal degeneration.

Cholesterol Accumulation Promotes Photoreceptor Senescence and Retinal Degeneration

Purpose

Dysregulated cholesterol metabolism is critical in the pathogenesis of AMD. Cellular senescence contributes to the development of numerous age-associated diseases. In this study, we investigated the link between cholesterol burden and the cellular senescence of photoreceptors.

Methods

Retinas from rod-specific ATP binding cassette subfamily A member 1 (Abca1) and G member 1 (Abcg1) (Abca1/g1-rod/-rod) knockout mice fed with a high-fat diet were analyzed for the signs of cellular senescence. Real-time quantitative PCR and immunofluorescence were used to characterize the senescence profile of the retina and cholesterol-treated photoreceptor cell line (661W). Inducible elimination of p16(Ink4a)-positive senescent cells (INK-ATTAC) mice or the administration of senolytic drugs (dasatinib and quercetin: D&Q) were used to examine the impact of senolytics on AMD-like phenotypes in Abca1/g1-rod/-rod retina.

Results

Increased accumulation of senescent cells as measured by markers of cellular senescence was found in Abca1/g1-rod/-rod retina. Exogenous cholesterol also induced cellular senescence in 661W cells. Selective elimination of senescent cells in Abca1/g1-rod/-rod;INK-ATTAC mice or by administration of D&Q improved visual function, lipid accumulation in retinal pigment epithelium, and Bruch's membrane thickening.

Conclusions

Cholesterol accumulation promotes cellular senescence in photoreceptors. Eliminating senescent photoreceptors improves visual function in a model of retinal neurodegeneration, and senotherapy offers a novel therapeutic avenue for further investigation.

Comparing 2-dimensional macular pigment optical density with objective and subjective perimetry and visual acuity in age-related macular degeneration

PURPOSE

To compare diagnostic power for different severities of age-related macular degeneration (AMD) of two-dimensional macular pigment optical densities (2D-MPOD) and spatially matched objective perimetry, with standard perimetry and best-corrected visual acuity (BCVA).

METHODS

The ObjectiveField Analyser (OFA) provided objective perimetry, and a Heidelberg Spectralis optical coherence tomography (OCT) measured 2D-MPOD in AMD patients, both completed twice over 0.99 ± 0.16 years. From each 2D-MPOD image, we extracted 20 regions/macula, matched to the 20 OFA stimuli/macula. For each region, we calculated 7 measures from the 2D-MPOD pixel values and correlated those with OFA sensitivities and delays. We quantified 2D-MPOD changes, the ability of 2D-MPOD and OFA to discriminate AMD stages, and the discriminatory power of Matrix perimetry and BCVA using percentage area under receiver operator characteristic plots (%AUROC).

RESULTS

In 58 eyes of 29 subjects (71.6 ± 6.3 years, 22 females), we found significant correlations between 2D-MPOD and OFA sensitivities for Age-Related Eye Disease Studies (AREDS)-3 and AREDS-4 severities. Delays showed significant correlations with AREDS-2. For AREDS-4, correlations extended across all eccentricities. Regression associated with the Bland-Altman plots showed significant changes in 2D-MPOD over the study period, especially variability measures. MPOD per-region medians discriminated AREDS-1 from AREDS-3 eyes at a %AUROC of 80.0 ± 6.3%, outperforming OFA, Matrix perimetry, and BCVA.

CONCLUSIONS

MPOD changes correlated with central functional changes and significant correlations extended peripherally in later-stage AMD. Good diagnostic power for earlier-stage AMD and significant change over the study suggest that 2D-MPOD and OFA may provide effective biomarkers.

Retinal debris triggers cytotoxic damage in cocultivated primary porcine RPE cells

Introduction

One of the most common causes of vision loss in the elderly population worldwide is age-related macular degeneration (AMD). Subsequently, the number of people affected by AMD is estimated to reach approximately 288 million by the year 2040. The aim of this study was to develop an ex vivo model that simulates various aspects of the complex AMD pathogenesis.

Methods

For this purpose, primary porcine retinal pigment epithelial cells (ppRPE) were isolated and cultured. One group was exposed to medium containing sodium iodate (NaIO3) to induce degeneration. The others were exposed to different supplemented media, such as bovine serum albumin (BSA), homogenized porcine retinas (HPR), or rod outer segments (ROOS) for eight days to promote retinal deposits. Then, these ppRPE cells were cocultured with porcine neuroretina explants for another eight days. To assess the viability of ppRPE cells, live/dead assay was performed at the end of the study. The positive RPE65 and ZO1 area was evaluated by immunocytochemistry and the expression of RLBP1, RPE65, and TJP1 was analyzed by RT-qPCR. Additionally, drusen (APOE), inflammation (ITGAM, IL6, IL8, NLRP3, TNF), oxidative stress (NFE2L2, SOD1, SOD2), and hypoxia (HIF1A) markers were investigated. The concentration of the inflammatory cytokines IL-6 and IL-8 was determined in medium supernatants from day 16 and 24 via ELISA.

Results

Live/dead assay suggests that especially exposure to NaIO3 and HPR induced damage to ppRPE cells, leading in a significant ppRPE cell loss. All supplemented media resulted in decreased RPE-characteristic markers (RPE65; ZO-1) and gene expression like RLBP1 and RPE65 in the cultured ppRPE cells. Besides, some inflammatory, oxidative as well as hypoxic stress markers were altered in ppRPE cells cultivated with NaIO3. The application of HPR induced an enhanced APOE expression. Pre-exposure of the ppRPE cells led to a diminished number of cones in all supplemented media groups compared to controls.

Discussion

Overall, this novel coculture model represents an interesting initial approach to incorporating deposits into coculture to mimic AMD pathogenesis. Nevertheless, the effects of the media used need to be investigated in further studies.

Local and Global Associations of Reticular Pseudodrusen in Age-Related Macular Degeneration

PURPOSE

To investigate the spatial distribution of reticular pseudodrusen (RPD) in eyes with age-related macular degeneration (AMD) and their correlation with functional measures, retinal thickness, and changes over time.

DESIGN

Longitudinal, cohort study.

PARTICIPANTS

Thirty-five participants with RPD and spectrum of AMD severity (including no AMD).

METHODS

Multimodal imaging was graded by a reading center, including evaluation of color fundus imaging to assess AMD severity scores. Reticular pseudodrusen presence on OCT volumes was confirmed on en face imaging and the RPD extent was contoured on infrared images. One study eye per participant underwent rod-mediated dark adaptation, measuring rod intercept time (RIT) at 5° and, if needed, 12° superior to the fovea.

MAIN OUTCOME MEASURES

The primary outcome was RIT and OCT thickness measures which were correlated with RPD area.

RESULTS

A total of 51 eyes had ≥ 1 visit with RPD detected (mean follow-up, 2.19 ± 2.04 years; range, 0-5 years), totaling 169 eye-based visits with RPD. Of the 51 eyes with RPD, 5 (9.8%) developed geographic atrophy and 17 (33.3%) progressed to neovascular AMD. Larger RPD areas were detected more frequently in AMD severity scores 6-7. Reticular pseudodrusen area within an eye generally increased over time. The lesion distribution showed a predilection for the superior retina, especially the outer superior subfield of the ETDRS grid, with the central subfield having least involvement. Reticular pseudodrusen area was inversely correlated with central subfield thickness and positively correlated with RIT at 5° (P = 0.001; r2 = 0.01) and 12° (P = 0.004; r2 = 0.01). Rod-mediated dark adaptation at 5° reached the test ceiling in > 85% of visits, irrespective of RPD lesion presence/absence at the test location. Retinal thickness decreased monotonically, with the central subfield demonstrating the greatest percentage change over 5 years (Δ = -5.47%).

CONCLUSIONS

In AMD, RPD involve predominantly the superior retina but can involve all ETDRS subfields and evolve over time. Eyes with RPD exhibit structural and functional impairments that can be measured beyond the boundaries of the RPD lesions, suggesting changes associated with RPD are associated with both local changes and a more widespread process.

FINANCIAL DISCLOSURES

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

PHENOTYPIC CHARACTERIZATION OF PREDICTORS FOR DEVELOPMENT AND PROGRESSION OF GEOGRAPHIC ATROPHY USING OPTICAL COHERENCE TOMOGRAPHY

PURPOSE

To evaluate the impact of optical coherence tomography phenotypes preceding atrophy related to age-related macular degeneration on the progression of atrophic lesions.

METHODS

In this observational retrospective cohort study, a total of 70 eyes of 60 consecutive patients with intermediate age-related macular degeneration with a minimum follow-up of 24 months were included. The atrophy was quantified using fundus autofluorescence, also considering the directionality of atrophy as centrifugal and centripetal progression rates. The main outcome measures were geographic atrophy (GA) progression rate (mm 2 /year) and square root transformation of GA (mm 2 /year).

RESULTS

The best-fit model for GA (odds ratio: 1.81, P < 0.001) and square root transformation of GA (odds ratio: 1.36, P < 0.001) areas revealed that the main baseline predictor was the presence of a retinal pigment epithelium-basal lamina-Bruch membrane splitting. Large drusen at baseline appeared protective for the GA area lesion expansion over time (odds ratio: 0.52, P < 0.001) when considered with other confounders.

CONCLUSION

A thin retinal pigment epithelium-basal lamina-Bruch membrane splitting without evidence of neovascularization on optical coherence tomography angiography likely represents an optical coherence tomography signature for late basal laminar deposits. Identifying this phenotype can help identify individuals with a higher risk of rapid progression and atrophy expansion.

LONG-TERM PRESERVATION OF VISUAL ACUITY AFTER RESORPTION OF ACQUIRED VITELLIFORM LESIONS IN AGE-RELATED MACULAR DEGENERATION

PURPOSE

To report the long-term (23 years) clinical and multimodal imaging features of acquired vitelliform lesions (AVLs) associated with nonneovascular age-related macular degeneration.

METHODS

Retrospective case report. Color and red-free fundus photographs, high-resolution optical coherence tomography, fluorescein and indocyanine green angiography, and optical coherence tomography-angiography were performed.

RESULTS

A 58-year-old man presented with bilateral AVLs in the setting of nonneovascular age-related macular degeneration. At baseline, his best-corrected visual acuity was 20/30 in his right eye and 20/20 in his left eye. Red-free fundus photographs showed AVLs with cuticular drusen in both eyes corresponding to a "stars-in-the-sky" pattern on fluorescein. Indocyanine green angiography showed no evidence of macular neovascularization. Throughout the 23-year follow-up, the patient reported consuming 20 mg/day of lutein supplement. At the end of follow-up, his best-corrected visual acuity was 20/20 in both eyes. Color fundus photographs showed resorption of the AVLs in both eyes and High-Res optical coherence tomography showed relative preservation of the outer retinal bands in the fovea. Optical coherence tomography-angiography confirmed the absence of macular neovascularization.

CONCLUSION

In nonneovascular age-related macular degeneration, spontaneous resorption of AVLs may be associated with long-term maintenance of visual acuity and relative preservation of the outer retinal morphology.

Prominin-1 null Xenopus laevis develop subretinal drusenoid-like deposits, cone-rod dystrophy, and RPE atrophy

Mutations in the PROMININ-1 (PROM1) gene are associated with inherited, non-syndromic vision loss. Here, we used CRISPR/Cas9 to induce truncating prom1-null mutations in Xenopus laevis to create a disease model. We then tracked progression of retinal degeneration in these animals from the ages of 6 weeks to 3 years old. We found that retinal degeneration caused by prom1-null is age-dependent and likely involves death or damage to the retinal pigment epithelium (RPE) that precedes photoreceptor degeneration. As prom1-null frogs age, they develop large cellular debris deposits in the subretinal space and outer segment layer which resemble subretinal drusenoid deposits (SDD) in their location, histology, and representation in color fundus photography and optical coherence tomography (OCT). In older frogs, these SDD-like deposits accumulate in size and number, and they are present before retinal degeneration occurs. Evidence for an RPE origin of these deposits includes infiltration of pigment granules into the deposits, thinning of RPE as measured by OCT, and RPE disorganization as measured by histology and OCT. The appearance and accumulation of SDD-like deposits and RPE thinning and disorganization in our animal model suggests an underlying disease mechanism for prom1-null mediated blindness of death and dysfunction of the RPE preceding photoreceptor degeneration, instead of direct effects upon photoreceptor outer segment morphogenesis, as was previously hypothesized.

Unveiling Statins and Genetics in Age-Related Macular Degeneration: The Coimbra Eye Study-Report 9

Purpose

To assess the association of age-related macular degeneration (AMD) progression and statins, connected with AMD genetic risk, and if there is an interplay between statins and genetics.

Methods

In this analysis, 682 subjects made two visits (6.5-year follow-up) of the Coimbra Eye Study. Subjects who started taking statins at any time point between the two visits were considered. Progressors were defined as not having AMD at baseline and having any AMD at follow-up. Genetic risk scores (GRSs) were calculated individually with 52 independent variants associated with AMD. Time to progression was estimated using unadjusted Kaplan-Meier curves. An extended Cox model was used for the association between statins and GRS with the risk for AMD progression. Multiplicative and additive interactions were assessed.

Results

Median survival time was 7.50 years for subjects not taking statins and 7.62 for subjects taking statins (P < 0.001). Statin intake reduced the risk for progression to AMD in 48%, adjusting for age, sex, body mass index, smoking, and diabetes (model 1) and GRS (model 2). The combined effects of not taking statins and having high GRS increased the progression risk fourfold compared to taking statins and having low GRS (hazard ratio [HR] = 4.25; 95% confidence interval [CI], 1.62-11.16; P = 0.003). For subjects not taking statins, an increased risk of progression was found for those subjects with high GRS compared to subjects with low GRS (HR = 1.80; 95% CI, 1.13-2.85; P = 0.013). No statistically significant multiplicative or additive interactions were found.

Conclusions

Statins seem to be protective against AMD progression, and genetics may play a role in treatment response.

Correlations Between the Neutrophil-Lymphocyte Ratio, Platelet-Lymphocyte Ratio, and Serum Lipid Fractions With Neovascular Age-Related Macular Degeneration

Introduction Age-related macular degeneration, a chronic and progressive disease, is one of the leading causes of vision loss globally among the elderly population. Multiple hypotheses have been proposed regarding its pathogenesis, including the presence of lipid metabolism alteration. Dysfunctional lipid handling within retinal pigment epithelial cells has been implicated in the accumulation of lipofuscin and subsequent induction of oxidative stress and inflammation, all contributing to retinal degeneration. The present study aims to comparatively analyze the serum lipid fraction distributions in patients with neovascular age-related macular degeneration (AMD) and controls. Materials and methods A retrospective study was carried out between January 2021 and December 2023 on 91 naïve patients with neovascular AMD and 90 controls admitted for routine cataract surgery. All subjects underwent a comprehensive ophthalmological exam, including ophthalmoscopy and optical coherence tomography (OCT) with central macular thickness (CMT) measurement. A complete blood count with differential and lipid fractions values was analyzed. The neutrophil-lymphocyte ratio (NLR), platelet-lymphocyte ratio (PLR), total cholesterol (TC), high-density lipoprotein cholesterol (HDL-C), low-density lipoprotein cholesterol (LDL-C), and triglycerides (TG) were comparatively analyzed between the control group and the test group. Results The groups were comparable in terms of age (73.84 ±7.52 years for the neovascular AMD group vs 72.1±10.92 years in controls; p=0.8) and gender distribution (p=0.243). The mean NLR and PLR values were slightly higher in the AMD group but not statistically significant (p=0.51, p>0.99, respectively). Comparative analysis of lipid profile fractions showed significantly higher HDL-C values in the exudative AMD group compared to normal subjects (61.27±19.4 mg/dL vs 50.99±7.86 mg/dL, p=0.006). Also, the proportion of subjects with HDL-C>60 mg/dL was higher in the exudative AMD group (p=0.014). There were no significant differences in total cholesterol (189.77±53.39 mg/dL vs 190.43±37.84 mg/dL, p=0.681), LDL-C, and TG. Logistic regression analysis showed that serum HDL-C and HDL-C values >60 mg/dL are significantly associated factors with neovascular AMD. However, there is no statistical correlation between the values of these biochemical parameters and visual acuity or CMT in the neovascular AMD patient group. Conclusions There were no correlations between NLR and PLR with neovascular AMD in the study group. Higher HDL-C values exceeding 60 mg/dL were associated with neovascular age-related macular degeneration and could represent a possible therapeutic target in neovascular AMD.

Proteostatic Remodeling of Small Heat Shock Chaperones─Crystallins by Ran-Binding Protein 2─and the Peptidyl-Prolyl cis-trans Isomerase and Chaperone Activities of Its Cyclophilin Domain

Disturbances in protein phase transitions promote protein aggregation─a neurodegeneration hallmark. The modular Ran-binding protein 2 (Ranbp2) is a cytosolic molecular hub for rate-limiting steps of phase transitions of Ran-GTP-bound protein ensembles exiting nuclear pores. Chaperones also regulate phase transitions and proteostasis by suppressing protein aggregation. Ranbp2 haploinsufficiency promotes the age-dependent neuroprotection of the chorioretina against phototoxicity by proteostatic regulations of neuroprotective substrates of Ranbp2 and by suppressing the buildup of polyubiquitylated substrates. Losses of peptidyl-prolyl cis-trans isomerase (PPIase) and chaperone activities of the cyclophilin domain (CY) of Ranbp2 recapitulate molecular effects of Ranbp2 haploinsufficiency. These CY impairments also stimulate deubiquitylation activities and phase transitions of 19S cap subunits of the 26S proteasome that associates with Ranbp2. However, links between CY moonlighting activity, substrate ubiquitylation, and proteostasis remain incomplete. Here, we reveal the Ranbp2 regulation of small heat shock chaperones─crystallins in the chorioretina by proteomics of mice with total or selective modular deficits of Ranbp2. Specifically, loss of CY PPIase of Ranbp2 upregulates αA-Crystallin, which is repressed in adult nonlenticular tissues. Conversely, impairment of CY's chaperone activity opposite to the PPIase pocket downregulates a subset of αA-Crystallin's substrates, γ-crystallins. These CY-dependent effects cause age-dependent and chorioretinal-selective declines of ubiquitylated substrates without affecting the chorioretinal morphology. A model emerges whereby inhibition of Ranbp2's CY PPIase remodels crystallins' expressions, subdues molecular aging, and preordains the chorioretina to neuroprotection by augmenting the chaperone capacity and the degradation of polyubiquitylated substrates against proteostatic impairments. Further, the druggable Ranbp2 CY holds pan-therapeutic potential against proteotoxicity and neurodegeneration.

Oxidative Stress, Persistent Inflammation and Blood Coagulation Alterations in Serum Proteome of Patients with Neovascular Age-Related Macular Degeneration

Neovascular age-related macular degeneration (AMD) is a major cause of irreversible blindness in elderly populations in developed countries. AMD's etiopathology is multifactorial, with strong environmental and genetic components, but the exact molecular pathomechanisms underlying the disease are still unknown. In this study, we analyzed blood serum collected from 74 neovascular AMD patients and 58 healthy controls to identify proteins that may serve as potential biomarkers and expand our knowledge about the etiopathogenesis of the disease. The study revealed 17 differentially expressed proteins-11 up-regulated and 6 down-regulated-in neovascular AMD, which are involved in the biological processes previously linked with the disease-oxidative stress and persistent inflammation, impaired cellular transport, lipid metabolism and blood coagulation. In conclusion, the differences in the expressions of the proteins identified in this study may contribute to our understanding of the mechanisms underlying AMD and possibly serve in future as promising biomarkers.

Human versus Artificial Intelligence: Validation of a Deep Learning Model for Retinal Layer and Fluid Segmentation in Optical Coherence Tomography Images from Patients with Age-Related Macular Degeneration

Artificial intelligence (AI) models have received considerable attention in recent years for their ability to identify optical coherence tomography (OCT) biomarkers with clinical diagnostic potential and predict disease progression. This study aims to externally validate a deep learning (DL) algorithm by comparing its segmentation of retinal layers and fluid with a gold-standard method for manually adjusting the automatic segmentation of the Heidelberg Spectralis HRA + OCT software Version 6.16.8.0. A total of sixty OCT images of healthy subjects and patients with intermediate and exudative age-related macular degeneration (AMD) were included. A quantitative analysis of the retinal thickness and fluid area was performed, and the discrepancy between these methods was investigated. The results showed a moderate-to-strong correlation between the metrics extracted by both software types, in all the groups, and an overall near-perfect area overlap was observed, except for in the inner segment ellipsoid (ISE) layer. The DL system detected a significant difference in the outer retinal thickness across disease stages and accurately identified fluid in exudative cases. In more diseased eyes, there was significantly more disagreement between these methods. This DL system appears to be a reliable method for accessing important OCT biomarkers in AMD. However, further accuracy testing should be conducted to confirm its validity in real-world settings to ultimately aid ophthalmologists in OCT imaging management and guide timely treatment approaches.

En Face Optical Coherence Tomography Illustrates the Trizonal Distribution of Drusen and Subretinal Drusenoid Deposits in the Macula

PURPOSE

To analyze the topographic distribution of macular drusen and subretinal drusenoid deposits (SDDs) using single-capture en face spectral domain optical coherence tomography (SD-OCT) imaging.

DESIGN

Retrospective case series.

METHODS

Analysis of 33 eyes of 20 patients with evidence of SDDs. Structural en face OCT images were reconstructed using a 40-µm-thick slab positioned from 48 to 88 µm above the Bruch membrane. The Early Treatment of Diabetic Retinopathy Study (ETDRS) grid and a rod/cone density map were overlaid on the en face OCT images, and the distribution of different subtypes of SDDs and macular drusen were assessed.

RESULTS

A total of 31 eyes (94%) showed a trizonal distribution pattern of drusen and SDDs. Whereas small to large drusen tended to aggregate in the central circle, dot SDDs predominated in the inner ring and the inner portion of the outer ring of the ETDRS grid and ribbon SDDs localized to the outer ring and outside the ETDRS grid. Of note, drusen colocalized to the region of greatest cone density, whereas ribbon SDDs colocalized to the area of greatest rod density. The dot SDDs mapped to the intermediate region with mixed rod and cone representation.

CONCLUSION

Dot and ribbon subtypes of SDDs and macular drusen show a characteristic trizonal distribution. The locations of these lesions colocalize according to the different densities of the cones and rods in the retina and may reflect varying pathophysiological activities of these photoreceptor subtypes.

Probing Deposit-Driven Age-Related Macular Degeneration Via Thicknesses of Outer Retinal Bands and Choroid: ALSTAR2 Baseline

Purpose

We aimed to identify structural differences in normal eyes, early age-related macular degeneration (AMD), and intermediate AMD eyes using optical coherence tomography (OCT) in a well-characterized, large cross-sectional cohort.

Methods

Subjects ≥ 60 years with healthy normal eyes, as well as early or intermediate AMD were enrolled in the Alabama Study on Age-related Macular Degeneration 2 (ALSTAR2; NCT04112667). Using Spectralis HRA + OCT2, we obtained macular volumes for each participant. An auto-segmentation software was used to segment six layers and sublayers: photoreceptor inner and outer segments, subretinal drusenoid deposits (SDDs), retinal pigment epithelium + basal lamina (RPE + BL), drusen, and choroid. After manually refining the segmentations of all B-scans, mean thicknesses in whole, central, inner and outer rings of the ETDRS grid were calculated and compared among groups.

Results

This study involved 502 patients, 252 were healthy, 147 had early AMD, and 103 had intermediate AMD eyes (per Age-Related Eye Disease Study [AREDS] 9-step). Intermediate AMD eyes exhibited thicker SDD and drusen, thinner photoreceptor inner segments, and RPE compared to healthy and early AMD eyes. They also had thicker photoreceptor outer segments than early AMD eyes. Early AMD eyes had thinner photoreceptor outer segments than normal eyes but a thicker choroid than intermediate AMD eyes. Using the Beckman scale, 42% of the eyes initially classified as early AMD shifted to intermediate AMD, making thickness differences for photoreceptor outer segments and choroid insignificant.

Conclusions

With AMD stages, the most consistent structural differences involve appearance of drusen and SDD, followed by RPE + BL thickness, and then thickness of photoreceptor inner and outer segments. Structural changes in the transition from aging to intermediate AMD include alterations in the outer retinal bands, including the appearance of deposits on either side of the RPE.

An overview of retinal light damage models for preclinical studies on age-related macular degeneration: identifying molecular hallmarks and therapeutic targets

Age-related macular degeneration (AMD) is a complex, multifactorial disease leading to progressive and irreversible retinal degeneration, whose pathogenesis has not been fully elucidated yet. Due to the complexity and to the multiple features of the disease, many efforts have been made to develop animal models which faithfully reproduce the overall AMD hallmarks or that are able to mimic the different AMD stages. In this context, light damage (LD) rodent models of AMD represent a suitable and reliable approach to mimic the different AMD forms (dry, wet and geographic atrophy) while maintaining the time-dependent progression of the disease. In this review, we comprehensively reported how the LD paradigms reproduce the main features of human AMD. We discuss the capability of these models to broaden the knowledge in AMD research, with a focus on the mechanisms and the molecular hallmarks underlying the pathogenesis of the disease. We also critically revise the remaining challenges and future directions for the use of LD models.

Quantitative Autofluorescence at AMD's Beginnings Highlights Retinal Topography and Grading System Differences: ALSTAR2 Baseline

INTRODUCTION

The aims of the study were to describe baseline quantitative (short-wavelength) autofluorescence (qAF) findings in a large pseudophakic cohort at age-related macular degeneration (AMD)'s beginnings and to assess qAF8 as an outcome measure and evaluate Age-Related Eye Disease Study (AREDS) and Beckman grading systems.

METHODS

In the ALSTAR2 baseline cohort (NCT04112667), 346 pseudophakic eyes of 188 persons (74.0 ± 5.5 years) were classified as normal (N = 160 by AREDS, 158 by Beckman), early AMD (eAMD) (N = 104, 66), and intermediate AMD (iAMD) (N = 82, 122). Groups were compared via mean qAF intensities in a 6°-8° annulus (qAF8) and maps of differences between observations and the overall mean, divided by standard deviation (Z-score).

RESULTS

qAF8 did not differ significantly among diagnostic groups by either stratification (p = 0.0869 AREDS; p = 0.0569 by Beckman). Notably, 45 eyes considered eAMD by AREDS became iAMD by Beckman. For AREDS-stratified eyes, Z-score maps showed higher centrally located qAF for normal, near the mean in eAMD, and lower values for iAMD. Maps deviated from this pattern for Beckman-stratified eyes.

CONCLUSIONS

In a large sample of pseudophakic eyes, qAF8 does not differ overall from normal aging to iAMD but also does not capture the earliest AMD activity in the macula lutea. AREDS classification gives results more consistent with a slow decline in histologic autofluorescence than Beckman classification.

Non-Neovascular Age-Related Macular Degeneration Assessment: Focus on Optical Coherence Tomography Biomarkers

The imagistic evaluation of non-neovascular age-related macular degeneration (AMD) is crucial for diagnosis, monitoring progression, and guiding management of the disease. Dry AMD, characterized primarily by the presence of drusen and retinal pigment epithelium atrophy, requires detailed visualization of the retinal structure to assess its severity and progression. Several imaging modalities are pivotal in the evaluation of non-neovascular AMD, including optical coherence tomography, fundus autofluorescence, or color fundus photography. In the context of emerging therapies for geographic atrophy, like pegcetacoplan, it is critical to establish the baseline status of the disease, monitor the development and expansion of geographic atrophy, and to evaluate the retina's response to potential treatments in clinical trials. The present review, while initially providing a comprehensive description of the pathophysiology involved in AMD, aims to offer an overview of the imaging modalities employed in the evaluation of non-neovascular AMD. Special emphasis is placed on the assessment of progression biomarkers as discerned through optical coherence tomography. As the landscape of AMD treatment continues to evolve, advanced imaging techniques will remain at the forefront, enabling clinicians to offer the most effective and tailored treatments to their patients.

Prevalence and Risk Factors of Age-Related Macular Degeneration in South Korea: Korea National Health and Nutrition Examination Survey

PURPOSE

To evaluate the prevalence and risk factors of age-related macular degeneration (AMD) in the Korean population.

METHODS

In this cross-sectional study based on the Korea National Health and Nutrition Examination Survey (2017-2020) data 13,737 participants aged ≥ 40 years with assessable fundus images were included. The prevalence and risk factors of AMD were evaluated. The prevalence of early AMD, geographic atrophy (GA), and neovascular AMD were also assessed. Logistic regression analyses were used to identify risk factors.

RESULTS

The prevalence (95% confidence interval [CI]) of AMD was 13.94% (13.15-14.72). The prevalence (95% CI) of early AMD, GA, and neovascular AMD was 13.07% (12.29-13.85), 0.26% (0.17-0.35), and 0.61% (0.47-0.75), respectively. The prevalence increased with age; it was 3.61%, 11.33%, 20.31%, 31.37%, and 33.98% in participants in their 40s, 50s, 60s, 70s, and ≥ 80 years, respectively. In multivariate analysis, AMD was positively associated with older age (p < 0.001; odds ratio [OR], 1.08; 95% CI, 1.07-1.09), male sex (p = 0.014; OR, 1.27; 95% CI, 1.05-1.53), and lower degree of education (p < 0.001; OR, 1.36 (for junior high school graduates); 95% CI, 1.12-1.65).

CONCLUSIONS

AMD was detected in approximately one-third of individuals aged ≥ 70 years, thus indicating that AMD is a common disease among older Koreans. Regular fundus examinations in populations with risk factors for AMD as well as education on methods to prevent or delay AMD progression, such as the Mediterranean diet, are necessary.

Microsomal triglyceride transfer protein is necessary to maintain lipid homeostasis and retinal function

Lipid processing by the retinal pigment epithelium (RPE) is necessary to maintain retinal health and function. Dysregulation of retinal lipid homeostasis due to normal aging or age-related disease triggers lipid accumulation within the RPE, on Bruch's membrane (BrM), and in the subretinal space. In its role as a hub for lipid trafficking into and out of the neural retina, the RPE packages a significant amount of lipid into lipid droplets for storage and into apolipoprotein B (APOB)-containing lipoproteins (Blps) for export. Microsomal triglyceride transfer protein (MTP), encoded by the MTTP gene, is essential for Blp assembly. Herein we test the hypothesis that MTP expression in the RPE is essential to maintain lipid balance and retinal function using the newly generated RPEΔMttp mouse model. Using non-invasive ocular imaging, electroretinography, and histochemical and biochemical analyses we show that genetic depletion of Mttp from the RPE results in intracellular lipid accumulation, increased photoreceptor-associated cholesterol deposits, and photoreceptor cell death, and loss of rod but not cone function. RPE-specific reduction in Mttp had no significant effect on plasma lipids and lipoproteins. While APOB was decreased in the RPE, most ocular retinoids remained unchanged, with the exception of the storage form of retinoid, retinyl ester. Thus suggesting that RPE MTP is critical for Blp synthesis and assembly but is not directly involved in plasma lipoprotein metabolism. These studies demonstrate that RPE-specific MTP expression is necessary to establish and maintain retinal lipid homeostasis and visual function.

Age-Related Macular Degeneration, a Mathematically Tractable Disease

A progression sequence for age-related macular degeneration onset may be determinable with consensus neuroanatomical nomenclature augmented by drusen biology and eye-tracked clinical imaging. This narrative review proposes to supplement the Early Treatment of Diabetic Retinopathy Study (sETDRS) grid with a ring to capture high rod densities. Published photoreceptor and retinal pigment epithelium (RPE) densities in flat mounted aged-normal donor eyes were recomputed for sETDRS rings including near-periphery rich in rods and cumulatively for circular fovea-centered regions. Literature was reviewed for tissue-level studies of aging outer retina, population-level epidemiology studies regionally assessing risk, vision studies regionally assessing rod-mediated dark adaptation (RMDA), and impact of atrophy on photopic visual acuity. The 3 mm-diameter xanthophyll-rich macula lutea is rod-dominant and loses rods in aging whereas cone and RPE numbers are relatively stable. Across layers, the largest aging effects are accumulation of lipids prominent in drusen, loss of choriocapillary coverage of Bruch's membrane, and loss of rods. Epidemiology shows maximal risk for drusen-related progression in the central subfield with only one third of this risk level in the inner ring. RMDA studies report greatest slowing at the perimeter of this high-risk area. Vision declines precipitously when the cone-rich central subfield is invaded by geographic atrophy. Lifelong sustenance of foveal cone vision within the macula lutea leads to vulnerability in late adulthood that especially impacts rods at its perimeter. Adherence to an sETDRS grid and outer retinal cell populations within it will help dissect mechanisms, prioritize research, and assist in selecting patients for emerging treatments.

Value and Significance of Hypofluorescent Lesions Seen on Late-Phase Indocyanine Green Angiography

Background and Purpose

The hypofluorescence of fundus lesions observed during the late phase of indocyanine green angiography (ICGA) in various diseases has often been overlooked or misinterpreted. This article explores the significance of fundus lesions that are initially isofluorescent during the early phase of ICGA but become hypofluorescent later in the examination.

Findings

Pathologies such as multiple evanescent white spot syndrome, acute posterior placoid syphilitic chorioretinitis, chronic central serous chorioretinopathy, choroidal hemangioma, and some fundus with drusen, present this phenomenon of late hypofluorescence.

Interpretation

The interpretation of ICGA images and the role of indocyanine green (ICG) uptake by the retinal pigment epithelium (RPE) in late fundus fluorescence is debated. Experimental evidence suggests that ICG accumulates progressively in the RPE after intravenous injection of the dye or after direct contact in vitro, making it a potential marker of RPE activity. Although the exact mechanisms of ICG diffusion through the choroid and its binding to the RPE require further investigation, the late hypofluorescence observed in certain ICGA diseases provides information on different modalities of RPE dysfunction.

Financial Disclosures

The author has no proprietary or commercial interest in any materials discussed in this article.

A New Generation of Gene Therapies as the Future of Wet AMD Treatment

Age-related macular degeneration (AMD) is an eye disease and the most common cause of vision loss in the Western World. In its advanced stage, AMD occurs in two clinically distinguished forms, dry and wet, but only wet AMD is treatable. However, the treatment based on repeated injections with vascular endothelial growth factor A (VEGFA) antagonists may at best stop the disease progression and prevent or delay vision loss but without an improvement of visual dysfunction. Moreover, it is a serious mental and financial burden for patients and may be linked with some complications. The recent first success of intravitreal gene therapy with ADVM-022, which transformed retinal cells to continuous production of aflibercept, a VEGF antagonist, after a single injection, has opened a revolutionary perspective in wet AMD treatment. Promising results obtained so far in other ongoing clinical trials support this perspective. In this narrative/hypothesis review, we present basic information on wet AMD pathogenesis and treatment, the concept of gene therapy in retinal diseases, update evidence on completed and ongoing clinical trials with gene therapy for wet AMD, and perspectives on the progress to the clinic of "one and done" therapy for wet AMD to replace a lifetime of injections. Gene editing targeting the VEGFA gene is also presented as another gene therapy strategy to improve wet AMD management.

Calpain-specific breakdown fragment in human drusen

PURPOSE

With aging and age-related macular dystrophy (AMD), proteolytic fragments are deposited in extracellular drusen located between the RPE and Bruch's membrane. Localized hypoxia may be a risk factor for AMD. Our hypothesis is that following hypoxia, activation of proteolytic enzymes called calpains may cause proteolysis/degeneration of retinal cells and RPE. No direct evidence has yet demonstrated activation of calpains in AMD. The purpose of the present study was to identify calpain-cleaved proteins in drusen.

METHODS

Seventy-six (76) drusen were analyzed in human eye sections from six normal and twelve AMD human donor eyes. The sections were subjected to immunofluorescence for the calpain-specific 150 kDa breakdown product from α-spectrin, SBDP150 - a marker for calpain activation, and for recoverin - a marker for photoreceptor cells.

RESULTS

Among 29 nodular drusen, 80% from normal eyes and 90% from AMD eyes stained positive for SBDP150. Among 47 soft drusen, mostly from AMD eyes, 72% stained positive for SBDP150. Thus, the majority of both soft and nodular drusen from AMD donors contained SBDP150.

CONCLUSIONS

SBDP150 was detected for the first time in soft and nodular drusen from human donors. Our results suggest that calpain-induced proteolysis participates in the degeneration of photoreceptors and/or RPE cells during aging and AMD. Calpain inhibitors may ameliorate AMD progression.

Proteostatic remodeling of small heat shock chaperones - crystallins by Ran-binding protein 2 and the peptidyl-prolyl cis-trans isomerase and chaperone activities of its cyclophilin domain

Disturbances in phase transitions and intracellular partitions of nucleocytoplasmic shuttling substrates promote protein aggregation - a hallmark of neurodegenerative diseases. The modular Ran-binding protein 2 (Ranbp2) is a cytosolic molecular hub for rate-limiting steps of disassembly and phase transitions of Ran-GTP-bound protein ensembles exiting nuclear pores. Chaperones also play central roles in phase transitions and proteostasis by suppressing protein aggregation. Ranbp2 haploinsufficiency promotes the age-dependent neuroprotection of the chorioretina against photo-oxidative stress by proteostatic regulations of Ranbp2 substrates and by countering the build-up of poly-ubiquitylated substrates. Further, the peptidyl-prolyl cis-trans isomerase (PPIase) and chaperone activities of the cyclophilin domain (CY) of Ranbp2 modulate the proteostasis of selective neuroprotective substrates, such as hnRNPA2B1, STAT3, HDAC4 or L/M-opsin, while promoting a decline of ubiquitylated substrates. However, links between CY PPIase activity on client substrates and its effect(s) on ubiquitylated substrates are unclear. Here, proteomics of genetically modified mice with deficits of Ranbp2 uncovered the regulation of the small heat shock chaperones - crystallins by Ranbp2 in the chorioretina. Loss of CY PPIase of Ranbp2 up-regulates αA-crystallin proteostasis, which is repressed in non-lenticular tissues. Conversely, the αA-crystallin's substrates, γ-crystallins, are down-regulated by impairment of CY's C-terminal chaperone activity. These CY-dependent effects cause the age-dependent decline of ubiquitylated substrates without overt chorioretinal morphological changes. A model emerges whereby the Ranbp2 CY-dependent remodeling of crystallins' proteostasis subdues molecular aging and preordains chorioretinal neuroprotection by augmenting the chaperone buffering capacity and the decline of ubiquitylated substrates against proteostatic impairments. Further, CY's moonlighting activity holds pan -therapeutic potential against neurodegeneration.

APOB100 transgenic mice exemplify how the systemic circulation content may affect the retina without altering retinal cholesterol input

Apolipoprotein B (APOB) is a constituent of unique lipoprotein particles (LPPs) produced in the retinal pigment epithelium (RPE), which separates the neural retina from Bruch's membrane (BrM) and choroidal circulation. These LPPs accumulate with age in BrM and contribute to the development of age-related macular degeneration, a major blinding disease. The APOB100 transgenic expression in mice, which unlike humans lack the full-length APOB100, leads to lipid deposits in BrM. Herein, we further characterized APOB100 transgenic mice. We imaged mouse retina in vivo and assessed chorioretinal lipid distribution, retinal sterol levels, retinal cholesterol input, and serum content as well as tracked indocyanine green-bound LPPs in mouse plasma and retina after an intraperitoneal injection. Retinal function and differentially expressed proteins were also investigated. APOB100 transgenic mice had increased serum LDL content and an additional higher density HDL subpopulation; their retinal cholesterol levels (initially decreased) became normal with age. The LPP cycling between the RPE and choroidal circulation was increased. Yet, LPP trafficking from the RPE to the neural retina was limited, and total retinal cholesterol input did not change. There were lipid deposits in the RPE and BrM, and retinal function was impaired. Retinal proteomics provided mechanistic insights. Collectively, our data suggested that the serum LDL/HDL ratio may not affect retinal pathways of cholesterol input as serum LPP load is mainly handled by the RPE, which offloads LPP excess to the choroidal circulation rather than neural retina. Different HDL subpopulations should be considered in studies linking serum LPPs and age-related macular degeneration.

Relationship Between Retinal Layer Thickness and Genetic Susceptibility to Age-Related Macular Degeneration in Asian Populations

Purpose

For OCT retinal thickness measurements to be used as a prodromal age-related macular degeneration (AMD) risk marker, the 3-dimensional (3D) topographic variation of the relationship between genetic susceptibility to AMD and retinal thickness needs to be assessed. We aimed to evaluate individual retinal layer thickness changes and topography at the macula that are associated with AMD genetic susceptibility.

Design

Genetic association study.

Participants

A total of 1579 healthy participants (782 Chinese, 353 Malays, and 444 Indians) from the multiethnic Singapore Epidemiology of Eye Diseases study were included.

Methods

Spectral-domain OCT and automatic segmentation of individual retinal layers were performed to produce 10 retinal layer thickness measurements at each ETDRS subfield, producing 3D topographic information. Age-related macular degeneration genetic susceptibility was represented via single nucleotide polymorphisms (SNPs) and aggregated via whole genome (overall) and pathway-specific age-related macular degeneration polygenic risk score (PRSAMD).

Main Outcome Measures

Associations of individual SNPs, overall PRSAMD, and pathway-specific PRSAMD with retinal thickness were analyzed by individual retinal layer and ETDRS subfield.

Results

CFH rs10922109, ARMS2-HTRA1 rs3750846, and LIPC rs2043085 were the top AMD susceptibility SNPs associated with retinal thickness of individual layers (P < 1.67 × 10-3), all at the central subfield. The overall PRSAMD was most associated with thinner L9 (outer segment photoreceptor/retinal pigment epithelium complex) thickness at the central subfield (β = -0.63 μm; P = 5.45 × 10-9). Pathway-specific PRSAMD for the complement cascade (β = -0.53 μm; P = 9.42 × 10-7) and lipoprotein metabolism (β = -0.05 μm; P = 0.0061) were associated with thinner photoreceptor layers (L9 and L7 [photoreceptor inner/outer segments], respectively) at the central subfield. The mean PRSAMD score was larger among Indians compared with that of the Chinese and had the thinnest thickness at the L9 central subfield (β = -1.00 μm; P = 2.91 × 10-7; R2 = 5.5%). Associations at other retinal layers and ETDRS regions were more heterogeneous.

Conclusions

Overall genetic susceptibility to AMD and the aggregate effects of the complement cascade and lipoprotein metabolism pathway are associated most significantly with L7 and L9 photoreceptor thinning at the central macula in healthy individuals. Photoreceptor thinning has potential to be a prodromal AMD risk marker, and topographic variation should be considered.

Financial Disclosures

Proprietary or commercial disclosure may be found in the Footnotes and Disclosures at the end of this article.

Lysolipids are prominent in subretinal drusenoid deposits, a high-risk phenotype in age-related macular degeneration

Introduction

Age related macular degeneration (AMD) causes legal blindness worldwide, with few therapeutic targets in early disease and no treatments for 80% of cases. Extracellular deposits, including drusen and subretinal drusenoid deposits (SDD; also called reticular pseudodrusen), disrupt cone and rod photoreceptor functions and strongly confer risk for advanced disease. Due to the differential cholesterol composition of drusen and SDD, lipid transfer and cycling between photoreceptors and support cells are candidate dysregulated pathways leading to deposit formation. The current study explores this hypothesis through a comprehensive lipid compositional analysis of SDD.

Methods

Histology and transmission electron microscopy were used to characterize the morphology of SDD. Highly sensitive tools of imaging mass spectrometry (IMS) and nano liquid chromatography tandem mass spectrometry (nLC-MS/MS) in positive and negative ion modes were used to spatially map and identify SDD lipids, respectively. An interpretable supervised machine learning approach was utilized to compare the lipid composition of SDD to regions of uninvolved retina across 1873 IMS features and to automatically discern candidate markers for SDD. Immunohistochemistry (IHC) was used to localize secretory phospholipase A2 group 5 (PLA2G5).

Results

Among the 1873 detected features in IMS data, three lipid classes, including lysophosphatidylcholine (LysoPC), lysophosphatidylethanolamine (LysoPE) and lysophosphatidic acid (LysoPA) were observed nearly exclusively in SDD while presumed precursors, including phosphatidylcholine (PC), phosphatidylethanolamine (PE) and phosphatidic acid (PA) lipids were detected in SDD and adjacent photoreceptor outer segments. Molecular signals specific to SDD were found in central retina and elsewhere. IHC results indicated abundant PLA2G5 in photoreceptors and retinal pigment epithelium (RPE).

Discussion

The abundance of lysolipids in SDD implicates lipid remodeling or degradation in deposit formation, consistent with ultrastructural evidence of electron dense lipid-containing structures distinct from photoreceptor outer segment disks and immunolocalization of secretory PLA2G5 in photoreceptors and RPE. Further studies are required to understand the role of lipid signals observed in and around SDD.

Acetyl-CoA carboxylase Inhibition increases RPE cell fatty acid oxidation and limits apolipoprotein efflux

Purpose

In age-related macular degeneration (AMD) and Sorsby's fundus dystrophy (SFD), lipid-rich deposits known as drusen accumulate under the retinal pigment epithelium (RPE). Drusen may contribute to photoreceptor and RPE degeneration in AMD and SFD. We hypothesize that stimulating β-oxidation in RPE will reduce drusen accumulation. Inhibitors of acetyl-CoA carboxylase (ACC) stimulate β-oxidation and diminish lipid accumulation in fatty liver disease. In this report we test the hypothesis that an ACC inhibitor, Firsocostat, limits the accumulation of lipid deposits in cultured RPE cells.

Methods

We probed metabolism and cellular function in mouse RPE-choroid, human fetal- derived RPE cells, and induced pluripotent stem cell-derived RPE cells. We used 13 C6-glucose and 13 C16-palmitate to determine the effects of Firsocostat on glycolytic, Krebs cycle, and fatty acid metabolism. 13 C labeling of metabolites in these pathways were analyzed using gas chromatography-linked mass spectrometry. We quantified ApoE and VEGF release using enzyme-linked immunosorbent assays. Immunostaining of sectioned RPE was used to visualize ApoE deposits. RPE function was assessed by measuring the trans-epithelial electrical resistance (TEER).

Results

ACC inhibition with Firsocostat increases fatty acid oxidation and remodels lipid composition, glycolytic metabolism, lipoprotein release, and enhances TEER. When human serum is used to induce sub-RPE lipoprotein accumulation, fewer lipoproteins accumulate with Firsocostat. In a culture model of Sorsby's fundus dystrophy, Firsocostat also stimulates fatty acid oxidation, improves morphology, and increases TEER.

Conclusions

Firsocostat remodels intracellular metabolism and improves RPE resilience to serum-induced lipid deposition. This effect of ACC inhibition suggests that it could be an effective strategy for diminishing drusen accumulation in the eyes of patients with AMD.

Targeting 7KCh-Induced Cell Death Response Mediated by p38, P2X7 and GSDME in Retinal Pigment Epithelium Cells with Sterculic Acid

Age-related macular degeneration (AMD) is the main cause of blindness in developed countries. AMD is characterized by the formation of drusen, which are lipidic deposits, between retinal pigment epithelium (RPE) and the choroid. One of the main molecules accumulated in drusen is 7-Ketocholesterol (7KCh), an oxidized-cholesterol derivative. It is known that 7KCh induces inflammatory and cytotoxic responses in different cell types and the study of its mechanism of action is interesting in order to understand the development of AMD. Sterculic acid (SA) counteracts 7KCh response in RPE cells and could represent an alternative to improve currently used AMD treatments, which are not efficient enough. In the present study, we determine that 7KCh induces a complex cell death signaling characterized by the activation of necrosis and an alternative pyroptosis mediated by P2X7, p38 and GSDME, a new mechanism not yet related to the response to 7KCh until now. On the other hand, SA treatment can successfully attenuate the activation of both necrosis and pyroptosis, highlighting its therapeutic potential for the treatment of AMD.

INFLAMMATORY CELL ACTIVITY IN TREATED NEOVASCULAR AGE-RELATED MACULAR DEGENERATION: A Histologic Case Study

BACKGROUND

Imaging indicators of macular neovascularization risk can help determine patient eligibility for new treatments for geographic atrophy secondary to age-related macular degeneration. Because type 1 macular neovascularization includes inflammation, we assessed by histology the distribution of cells with inflammatory potential in two fellow eyes with age-related macular degeneration.

METHODS

Two eyes of a White woman in her 90's with type 3 macular neovascularization treated with antivascular endothelial growth factor were prepared for high-resolution histology. Eye-tracked spectral domain optical coherence tomography applied to the preserved donor eyes linked in vivo imaging to histology. Cells were enumerated in the intraretinal, subretinal, and subretinal retinal pigment epithelium (RPE)-basal lamina compartments on 199 glass slides. Cells with numerous organelles were considered to RPE-derived; cells with sparse RPE organelles were considered non-RPE phagocytes.

RESULTS

Both eyes had soft drusen and abundant subretinal drusenoid deposit. In the retina and subretinal space, RPE-derived cells, including hyperreflective foci, were common (n = 125 and 73, respectively). Non-RPE phagocytes were infrequent (n = 5 in both). Over drusen, RPE morphology transitioned smoothly from the age-normal layer toward the top, suggesting transdifferentiation. The sub-RPE-basal lamina space had RPE-derived cells (n = 87) and non-RPE phagocytes (n = 49), including macrophages and giant cells.

CONCLUSION

Numerous sub-RPE-basal lamina cells of several types are consistent with the documented presence of proinflammatory lipids in drusen and aged Bruch's membrane. The relatively compartmentalized abundance of infiltrating cells suggests that drusen contents are more inflammatory than subretinal drusenoid deposit, perhaps reflecting their environments. Ectopic RPE occurs frequently. Some manifest as hyperreflective foci. More cells may be visible as optical coherence tomography technologies evolve.

Hyperreflective foci distribution in eyes with dry age-related macular degeneration with subretinal drusenoid deposits

PURPOSE

To investigate the distribution of hyperreflective foci (HRF) in eyes with dry age-related macular degeneration (AMD).

METHODS

We retrospectively reviewed optical coherence tomography (OCT) images of 58 dry AMD eyes presenting HRF. The distribution of HRF according to the early treatment diabetic retinopathy study area was analyzed according to the presence of subretinal drusenoid deposits (SDDs).

RESULTS

We classified 32 eyes and 26 eyes into the dry AMD with SDD group (SDD group) and dry AMD without SDD group (non-SDD group), respectively. The non-SDD group had higher prevalence and density of HRF at the fovea (65.4% and 1.71 ± 1.48) than the SDD group (37.5% and 0.48 ± 0.63, P = 0.035 and P < 0.001, respectively). However, the prevalence and density of HRF in the outer circle area of the SDD group (81.3% and 0.11 ± 0.09) were greater than those of the non-SDD group (53.8% and 0.05 ± 0.06, p = 0.025 and p = 0.004, respectively). The SDD group showed higher prevalence and mean densities of HRF in the superior and temporal area than in the non-SDD group (all, p < 0.05).

CONCLUSION

HRF distributions in dry AMD varied according to the presence of SDDs. This might support that the degenerative features may be different between dry AMD eyes with and without SDDs.

HISTOLOGY, DIMENSIONS, AND FLUORESCEIN STAINING CHARACTERISTICS OF NODULAR AND CUTICULAR DRUSEN IN AGE-RELATED MACULAR DEGENERATION

PURPOSE

To enable in vivo analysis of drusen composition and lifecycle, the macular nodular and cuticular drusen were assessed using histology.

METHODS

Median and interquartile range of base widths of single (nonconfluent) nodular drusen in three sources were determined histologically: 43 eyes of 43 clinically undocumented donors, in an online resource; one eye with punctate hyperfluorescence in fluorescein angiography; and two eyes of one patient with bilateral "starry sky" cuticular drusen. All tissues were processed for high-resolution epoxy-resin histology and for cuticular drusen, transmission electron microscopy.

RESULTS

All drusen localized between the retinal pigment epithelium basal lamina and inner collagenous layer of the Bruch membrane. They were solid, globular, homogeneously stained with toluidine blue, and uncovered by basal laminar deposit and basal mounds. Median base widths were 13.0 µ m (Source 1, N = 128 drusen, interquartile range 7.7, 20.0 µ m), 15.3 µ m (Source 2, N = 87, interquartile range 10.6, 20.5 µ m), and 7.3 µ m (Source 3, N = 78, interquartile range 3.9, 14.1 µ m).

CONCLUSION

In three samples, >90% of solitary nodular drusen were <30 µ m, the visibility threshold in color fundus photography; these drusen are hyperfluorescent in fluorescein angiography. Whether these progress to soft drusen, known as high-risk from epidemiology studies and hypofluorescent, may be determinable from multimodal imaging datasets that include fluorescein angiography.

LOW-DOSE SUPPLEMENTATION WITH RETINOL IMPROVES RETINAL FUNCTION IN EYES WITH AGE-RELATED MACULAR DEGENERATION BUT WITHOUT RETICULAR PSEUDODRUSEN

PURPOSE

The aim of this study was to determine the functional impact of oral vitamin A supplementation in patients with intermediate age-related macular degeneration with and without reticular pseudodrusen (RPD) demonstrating dysfunction in dark adaptation.

METHODS

Five patients with intermediate age-related macular degeneration and without RPD (AMD group; mean ± SD age 78.0 ± 4.7 years) and seven with RPD (RPD group; age 74.1 ± 11.2 years) were supplemented with 16,000 IU of vitamin A palmitate for 8 weeks. Assessment at baseline, 4, 8, and 12 weeks included scotopic thresholds, dark adaptation, best-corrected and low luminance visual acuities, and the low-luminance quality of life questionnaire.

RESULTS

In the linear mixed model, rod intercept time improved significantly in the AMD group (mean [95% CI] change -1.1 minutes [-1.8; -0.5] after 4 weeks ( P < 0.001) and -2.2 min [-2.9 to -1.6] after 8 weeks of vitamin A supplementation ( P < 0.001). The dark adaptation cone plateau also significantly improved (i.e., more sensitive cone threshold) at 4 and 8 weeks ( P = 0.026 and P = 0.001). No other parameters improved in the AMD group, and there was no significant improvement in any parameter in the RPD group despite significantly elevated serum vitamin A levels measurable in both groups after supplementation ( P = 0.024 and P = 0.013).

CONCLUSION

Supplementation with 16,000 IU vitamin A, a lower dose than used in previous studies, partially overcomes the pathophysiologic functional changes in AMD eyes. The lack of improvement in the RPD group may indicate structural impediments to increasing vitamin A availability in these patients and/or may reflect the higher variability observed in the functional parameters for this group.

Choriocapillaris Impairment Is Associated With Delayed Rod-Mediated Dark Adaptation in Age-Related Macular Degeneration

Purpose

Progress toward treatment and prevention of age-related macular degeneration (AMD) requires imaging end points that relate to vision. We investigated choriocapillaris flow signal deficits (FD%) and visual function in eyes of individuals aged ≥60 years, with and without AMD.

Methods

One eye of each participant in the baseline visit of the Alabama Study on Early Age-Related Macular Degeneration 2 (ALSTAR2; NCT04112667) was studied. AMD presence and severity was determined using the Age-Related Eye Disease Study (AREDS) grading system. FD% was quantified using macular spectral domain optical coherence tomography angiography (OCTA) scans. Vision tests included rod-mediated dark adaptation (RMDA), best-corrected visual acuity, and contrast sensitivity (photopic and mesopic), and microperimetric light sensitivity (scotopic, mesopic, and photopic). Presence of subretinal drusenoid deposits (SDD) was determined using multimodal imaging.

Results

In 410 study eyes of 410 participants (mean [SD] age = 71.7 years [5.9]), FD% was higher in early AMD (mean [SD] = 54.0% [5.5], N = 122) and intermediate AMD (59.8% [7.4], N = 92), compared to normal (52.1% [5.3], N = 196) eyes. Among visual functions evaluated, RMDA showed the strongest association with FD% (r = 0.35, P < 0.0001), followed by contrast sensitivity (r = -0.22, P < 0.0001). Eyes with SDD had worse FD% (58.3% [7.4], N = 87), compared to eyes without SDD (53.4% [6.0], N = 323, P = < 0.0001).

Conclusions

Choriocapillaris FD% were associated with AMD severity and with impaired vision, especially RMDA. Reduced metabolic transport and exchange across the choriocapillaris-Bruch's membrane retinal pigment epithelium (RPE) complex, a causal factor for high-risk soft drusen formation, also may impair photoreceptor sustenance from the circulation. This includes retinoid resupply, essential to dynamic rod function.

Apolipoprotein ε in Brain and Retinal Neurodegenerative Diseases

Alzheimer's disease (AD) is the most common form of dementia that remains incurable and has become a major medical, social, and economic challenge worldwide. AD is characterized by pathological hallmarks of senile plaques (SP) and neurofibrillary tangles (NFTs) that damage the brain up to twenty years before a clinical diagnosis is made. Interestingly these pathological features have also been observed in retinal neurodegenerative diseases including age related macular degeneration (ARMD), glaucoma and diabetic retinopathy (DR). An association of AD with these diseases has been suggested in epidemiological studies and several common pathological events and risk factors have been identified between these diseases. The E4 allele of Apolipoprotein E (APOE) is a well-established genetic risk factor for late onset AD. The ApoE ε4 allele is also associated with retinal neurodegenerative diseases however in contrast to AD, it is considered protective in AMD, likewise ApoE E2 allele, which is a protective factor for AD, has been implicated as a risk factor for AMD and glaucoma. This review summarizes the evidence on the effects of ApoE in retinal neurodegenerative diseases and discusses the overlapping molecular pathways in AD. The involvement of ApoE in regulating amyloid beta (Aβ) and tau pathology, inflammation, vascular integrity, glucose metabolism and vascular endothelial growth factor (VEGF) signaling is also discussed.

INDOCYANINE GREEN ANGIOGRAPHY OF TYPE 1 MACULAR NEOVASCULARIZATION IN AGE-RELATED MACULAR DEGENERATION AND CENTRAL SEROUS CHORIORETINOPATHY REVEALS DIFFERENT DISEASE MECHANISMS

PURPOSE

To assess the rate of late phase hyperfluorescent plaque (LPHP) in Type 1 macular neovascularization (MNV) in central serous chorioretinopathy (CSCR) and age-related macular degeneration (AMD) and to evaluate its prognostic value.

METHODS

Retrospective study including Type 1 MNV in AMD and CSCR, from 2012 to 2020. Eyes with a late indocyanine green angiography image (>20 minutes) and clear visualization of MNV on optical coherence tomography angiography (OCTA) were included. Quantitative and qualitative parameters on optical coherence tomography and best-corrected visual acuity were recorded at baseline and after three monthly antivascular endothelial growth factor injections.

RESULTS

Eighty-three eyes were included, 35 with CSCR and 48 with AMD. Patients in the CSCR group were significantly younger than in the AMD group (61.3 ± 10.4 vs. 80.2 ± 6.8 years, respectively, P < 0.001), predominantly male (68.6% CSCR vs. 35.4% AMD; P = 0.003), and with a thicker choroid (379 ± 93.3 µ m vs. 204.2 ± 93.2 µ m; P < 0.001). Type 1 MNV in CSCR showed fewer LPHP compared with AMD (31.4% vs. 77.1%; P < 0.001). The baseline visual acuity was lower in patients with LPHP (0.37 ± 0.22 vs. 0.27 ± 0.28 logarithm of the minimum angle of resolution, P = 0.03). On multivariate analysis, AMD was associated with the presence of LPHP ( P < 0.001). No significant difference in the response to antivascular endothelial growth factor was observed.

CONCLUSION

Leakage of macromolecules from MNV and accumulation in the retinal pigment epithelium and/or in the stroma imaged by the LPHP is less common in eyes with Type 1 MNV in CSCR than in AMD. Late phase indocyanine green angiography imaging offers an insight into the metabolism of the dye and the environment surrounding the neovascular membrane.

Downregulation of lysosomal trafficking in ARPE19 cells leads to decreased transfection efficiency at high passage

PURPOSE

ARPE19 cells are a commonly used cell culture model for the study of retinal pigment epithelial cell biology and pathologies. However, numerous studies have demonstrated that ARPE19 undergo morphologic, transcriptomic and genomic alterations over time and with increasing passage number. Herein, we explore the mechanisms underlying increased resistance to the delivery of exogenous genetic material via transfection in ARPE19 cells using mass spectrometry.

METHODS

ARPE19 cells (N=5 wells/reagent) were seeded in 6-well plates at passages 24 through 30. At 70% confluency an mCherry reporter construct was delivered via transfection using Lipofectamine 3000, Lipofectamine LTX, Lipofectamine Stem, or PEI (polyethylenimine) reagents. After 72 hours, transfection efficiency was quantified by fluorescence microscopy and flow cytometry. Mass spectrometry and immunofluorescence of ARPE19 cells were performed at passages 24 and 30 to evaluate altered protein synthesis and localization between passage numbers.

RESULTS

ARPE19 transfection showed a maximum transfection efficiency of 32.4% at P26 using Lipofectamine 3000 reagent. All lipofectamine based reagents demonstrated statistically significant decreases in transfection efficiency between passages 24 and 30. Mass spectrometry analysis revealed 18 differentially expressed proteins, including down-regulation of clathrin light chain B (CLTB) and legumain (LGMN) that was confirmed via immunofluorescence imaging, which indicated altered intracellular localization.

CONCLUSIONS

ARPE19 cells demonstrate passage number dependent changes in lipofectamine-based transfection efficiency. Mass spectrometry and immunofluorescence indicates the observed decrease in transfection efficiency involves the dysregulation of endocytosis and intracellular endolysosomal trafficking at later passages.

TRANSLATIONAL RELEVANCE

This study contributes to mounting evidence for changes in ARPE19 cell physiology with increasing passage number. This information is of value for the continued use of ARPE19 cells as a model system for RPE biology and the development of therapeutics.

Causal effects of serum lipid biomarkers on early age-related macular degeneration using Mendelian randomization

BACKGROUND

Age-related macular degeneration (AMD) is one of the major causes of vision loss. Early AMD needs to be taken seriously, but the causal effects of lipid biomarkers on early AMD remain unclear.

METHODS

In this study, two-sample Mendelian randomization (MR) analysis was performed to systematically assess the causal relationships between seven serum lipid biomarkers (apolipoprotein A (ApoA), apolipoprotein B (ApoB), total cholesterol (CHOL), high-density lipoprotein cholesterol (HDL-C), direct low-density lipoprotein cholesterol (LDL-C), lipoprotein A [Lp(a)], and triglycerides (TG)) and risk of early AMD. In total, 14,034 cases and 91,214 controls of European ancestry were included in the analysis (number of SNPs = 11,304,110).

RESULTS

MR estimates revealed that a higher HDL-C level is strongly associated with increased risk of early AMD (OR = 1.25, 95% CI: 1.15-1.35, P = 2.61 × 10^-8). In addition, level of ApoA is also positively associated with risk of early AMD (OR = 2.04, 95% CI: 1.50-2.77, P = 6.27 × 10^-6). Conversely, higher levels of TG significantly decrease the risk of early AMD (OR = 0.77, 95% CI: 0.71-0.84, P = 5.02 × 10^-10). Sensitivity analyses further supported these associations. Moreover, multivariable MR analyses, adjusted for the effects of correlated lipid biomarkers, yielded similar results.

CONCLUSION

This study identifies causal relationships between elevated circulating HDL-C/ApoA levels and increased risk of early AMD, in addition to finding that TG specifically reduces the risk of early AMD. These findings contribute to a better understanding of the role of lipid metabolism in drusen formation, particularly in early AMD development.

Quantitative characterizations of the cholesterol-related pathways in the retina and brain of hamsters

The retina and brain are separated from the systemic circulation by the anatomical barriers, which are permeable (the outer blood-retinal barrier) and impermeable (the blood-brain and inner blood-retina barriers) to cholesterol. Herein we investigated whether the whole-body cholesterol maintenance affects cholesterol homeostasis in the retina and brain. We used hamsters, whose whole-body cholesterol handling is more similar to those in humans than in mice and conducted separate administrations of deuterated water and deuterated cholesterol. We assessed the quantitative significance of the retinal and brain pathways of cholesterol input and compared the results with those from our previous studies in mice. The utility of the measurements in the plasma of deuterated 24-hydroxycholesterol, the major cholesterol elimination product from the brain, was investigated as well. We established that despite a 7-fold higher serum LDL to HDL ratio and other cholesterol-related differences, in situ biosynthesis remained the major source of cholesterol for hamster retina, although its quantitative significance was reduced to 53% as compared to 72-78% in mouse retina. In the brain, the principal pathway of cholesterol input was also the same, in situ biosynthesis, accounting for 94% of the total brain cholesterol input (96% in mice); the interspecies differences pertained to the absolute rates of the total cholesterol input and turnover. We documented the correlations between deuterium enrichments of the brain 24-hydroxycholesterol, brain cholesterol, and plasma 24-hydroxycholesterol, which suggested that deuterium enrichment of plasma 24-hydroxycholesteol could be an in vivo marker of cholesterol elimination and turnover in the brain.

The Blood-ocular Barriers and their Dysfunction: Anatomy, Physiology, Pathology

Complex barriers comprise the blood-aqueous (BAB) and the blood-retinal barrier (BRB), and separate anterior and posterior eye chambers, vitreous body, and sensory retina from the circulation. They prevent pathogens and toxins from entering the eye, control movement of fluid, proteins, and metabolites, and contribute to the maintenance of the ocular immune status. Morphological correlates of blood-ocular barriers are tight junctions between neighboring endothelial and epithelial cells, which function as gatekeepers of the paracellular transport of molecules, thereby limiting their uncontrolled access to ocular chambers and tissues. The BAB is composed of tight junctions between endothelial cells of the iris vasculature, endothelial cells of Schlemm's canal inner wall, and cells of the nonpigmented ciliary epithelium. The BRB consists of tight junctions between endothelial cells of the retinal vessels (inner BRB) and epithelial cells of the retinal pigment epithelium (outer BRB). These junctional complexes respond rapidly to pathophysiological changes, thus enabling vascular leakage of blood-derived molecules and inflammatory cells into ocular tissues and chambers. Blood-ocular barrier function, which can be clinically measured by laser flare photometry or fluorophotometry, is compromised in traumatic, inflammatory, or infectious processes, but also frequently contributes to the pathophysiology of chronic diseases of the anterior eye segment and the retina, as exemplified by diabetic retinopathy and age-related macular degeneration.

Identification of 7-Ketocholesterol-Modulated Pathways and Sterculic Acid Protective Effect in Retinal Pigmented Epithelium Cells by Using Genome-Wide Transcriptomic Analysis

Age-related macular degeneration (AMD) is the leading cause of blindness in developed countries. AMD is characterized by the formation of lipidic deposits between the retinal pigment epithelium (RPE) and the choroid called drusen. 7-Ketocholesterol (7KCh), an oxidized-cholesterol derivative, is closely related to AMD as it is one of the main molecules accumulated in drusen. 7KCh induces inflammatory and cytotoxic responses in different cell types, and a better knowledge of the signaling pathways involved in its response would provide a new perspective on the molecular mechanisms that lead to the development of AMD. Furthermore, currently used therapies for AMD are not efficient enough. Sterculic acid (SA) attenuates the 7KCh response in RPE cells and is presented as an alternative to improve these therapies. By using genome-wide transcriptomic analysis in monkey RPE cells, we have provided new insight into 7KCh-induced signaling in RPE cells, as well as the protective capacity of SA. 7KCh modulates the expression of several genes associated with lipid metabolism, endoplasmic reticulum stress, inflammation and cell death and induces a complex response in RPE cells. The addition of SA successfully attenuates the deleterious effect of 7KCh and highlights its potential for the treatment of AMD.

In Vivo Longitudinal Measurement of Cone Photoreceptor Density in Intermediate Age-Related Macular Degeneration

PURPOSE

To evaluate cone photoreceptor density in clinically unremarkable retinal regions in patients with age-related macular degeneration (AMD) using adaptive optics scanning laser ophthalmoscopy (AOSLO).

DESIGN

Prospective case series with normal comparison group.

METHODS

Ten eyes of 7 patients with intermediate AMD were studied, including 4 with predominantly subretinal drusenoid deposits (SDD) and 3 without SDD. Macular regions with a clinical absence of AMD-associated lesions were identified by cone packing structure on AOSLO and optical coherence tomography. Cone density was measured in 1174 clinically unremarkable regions within the central subfield (CSF), the inner (IR), and outer rings (OR) of the Early Treatment Diabetic Retinopathy Study grid over 39.6 ± 3.3 months and compared with age-matched normal values obtained in 17 participants.

RESULTS

Cone density decreased at 98.3% of the examined locations over time in the eyes with AMD. In the CSF, IR, and OR, cones declined by -255 ± 135, -133 ± 45, and -59 ± 24 cones/degree2/year, respectively, in eyes with SDD, and by -212 ± 89, -83 ± 37, and -27 ± 18 cones/degree2/year, respectively, in eyes without SDD. The percentage of retinal loci with cone density lower than normal (Z score < -2) increased over the follow-up: from 42% at the baseline to 80% at the last visit in eyes with SDD and from 31% to 70% in eyes without SDD.

CONCLUSIONS

AOSLO revealed cone photoreceptor loss in regions that appear otherwise unremarkable clinically. These findings may help explain the loss of mesopic sensitivity reported in these areas in eyes with intermediate AMD.

Age-related macular degeneration

Age-related macular degeneration is an increasingly important public health issue due to ageing populations and increased longevity. Age-related macular degeneration affects individuals older than 55 years and threatens high-acuity central vision required for important tasks such as reading, driving, and recognising faces. Advances in retinal imaging have identified biomarkers of progression to late age-related macular degeneration. New treatments for neovascular age-related macular degeneration offer potentially longer-lasting effects, and progress is being made towards a treatment for atrophic late age-related macular degeneration. An effective intervention to slow progression in the earlier stages of disease, or to prevent late age-related macular degeneration development remains elusive, and our understanding of underlying mechanistic pathways continues to evolve.

A Protocol to Evaluate and Quantify Retinal Pigmented Epithelium Pathologies in Mouse Models of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a debilitating retinal disorder in aging populations. It is widely believed that dysfunction of the retinal pigmented epithelium (RPE) is a key pathobiological event in AMD. To understand the mechanisms that lead to RPE dysfunction, mouse models can be utilized by researchers. It has been established by previous studies that mice can develop RPE pathologies, some of which are observed in the eyes of individuals diagnosed with AMD. Here, we describe a phenotyping protocol to assess RPE pathologies in mice. This protocol includes the preparation and evaluation of retinal cross-sections using light microscopy and transmission electron microscopy, as well as that of RPE flat mounts by confocal microscopy. We detail the common types of murine RPE pathologies observed by these techniques and ways to quantify them through unbiased methods for statistical testing. As proof of concept, we use this RPE phenotyping protocol to quantify the RPE pathologies observed in mice overexpressing transmembrane protein 135 (Tmem135) and aged wild-type C57BL/6J mice. The main goal of this protocol is to present standard RPE phenotyping methods with unbiased quantitative assessments for scientists using mouse models of AMD.

Changes in drusen-associated autofluorescence over time observed by fluorescence lifetime imaging ophthalmoscopy in age-related macular degeneration

PURPOSE

To observe fundus autofluorescence (FAF) lifetimes and peak emission wavelength (PEW) of drusen with respect to the pathology of the overlying RPE in the follow-up of AMD-patients.

METHODS

Forty eyes of 38 patients (age: 75.1 ± 7.1 years) with intermediate AMD were included. FAF lifetimes and PEW were recorded by fluorescence lifetime imaging ophthalmoscopy (FLIO). Twenty-six eyes had a follow-up investigation between months 12 and 36, and 10 at months 37-72. AMD progression was retrieved from color fundus photography (CFP) and OCT. Drusen were classified with respect to changes in the overlying RPE into groups no, questionable or faint, and apparent hyperpigmentation based on CFP.

RESULTS

Among the 210 hyperautofluorescent drusen found at baseline, those with hyperpigmentation had longer lifetimes and shorter PEW than those without. Drusen without hyperpigmentation had shorter lifetimes and PEW than neighboring RPE (all p < 0.001) at baseline, but drusen lifetimes increased, and PEW shortened further over follow-up. Eyes, showing AMD progression, had significantly longer FAF lifetimes at baseline than non-progressing eyes: 282 ± 102 ps versus 245 ± 98 ps, p < 0.001 and 365 ± 44 ps vs. 336 ± 48 ps, p = 0.025 for short and long wavelength FLIO channel, respectively.

CONCLUSIONS

Depending on hyperpigmentation properties, drusen show lifetimes and PEW different from that of adjacent RPE which change over the natural history of AMD. This difference and change, however, might reflect progressive dysmorphia of the RPE rather than representing fluorescence of drusen material itself. Nevertheless, the observed FAF changes could make FLIO a useful tool for the early detection of AMD progression risk.

Six-year incidence of age-related macular degeneration and correlation to OCT-derived drusen volume measurements in a Chinese population

AIMS

To report the 6-year incidence of optical coherence tomography (OCT)-derived age-related changes in drusen volume and related systemic and ocular associations.

METHODS

Chinese adults aged 40 years and older were assessed at baseline and 6 years with colour fundus photography (CFP) and spectral domain (SD) OCT. CFPs were graded for age-related macular degeneration (AMD) features and drusen volume was generated using commercially available automated software.

RESULTS

A total of 4172 eyes of 2580 participants (mean age 58.12±9.03 years; 51.12% women) had baseline and 6-year follow-up CFP for grading, of these, 2130 eyes of 1305 participants had gradable SD-OCT images, available for analysis. Based on CFP grading, 136 (3.39%) participants developed incident early AMD and 10 (0.25%) late AMD. Concurrently, retinal pigment epithelial-Bruch's membrane (RPE-BrC) volumes decreased, remained stable and increased in 6.8%, 78.5% and 14.7%, respectively, over 6 years. In eyes where RPE-BrC volumes were >0 mm³ at baseline, this was associated with two-fold higher prevalence rate of any AMD at baseline (p<0.001). Multivariable analysis showed that when compared with eyes where RPE-BrC volume was unchanged, volume decrease was significantly associated with older age (OR=1.30; p<0.001), smoking (OR=2.21; p=0.001) and chronic kidney disease (OR=3.4, p=0.008), while increase was associated with older age (OR=1.36; p<0.001) and hypertension (OR=1.43; p=0.016).

CONCLUSION

AMD incidence detected at 6 years on CFP and correlated OCT-derived drusen volume measurement change is low. Older age and some systemic risk factors are associated with drusen volume change, and our data provide new insights into relationship between systemic risk factors and outer retinal morphology in Asian eyes.