Antecedents of Soft Drusen, the Specific Deposits of Age-Related Macular Degeneration, in the Biology of Human Macula

Control of Complement Activation by the Long Pentraxin PTX3: Implications in Age-Related Macular Degeneration

Dysregulation of the complement system is central to age-related macular degeneration (AMD), the leading cause of blindness in the developed world. Most of the genetic variation associated with AMD resides in complement genes, with the greatest risk associated with polymorphisms in the complement factor H (CFH) gene; factor H (FH) is the major inhibitor of the alternative pathway (AP) of complement that specifically targets C3b and the AP C3 convertase. Long pentraxin 3 (PTX3) is a soluble pattern recognition molecule that has been proposed to inhibit AP activation via recruitment of FH. Although present in the human retina, if and how PTX3 plays a role in AMD is still unclear. In this work we demonstrated the presence of PTX3 in the human vitreous and studied the PTX3-FH-C3b crosstalk and its effects on complement activation in a model of retinal pigment epithelium (RPE). RPE cells cultured in inflammatory AMD-like conditions overexpressed the PTX3 protein, and up-regulated AP activating genes. PTX3 bound RPE cells in a physiological setting, however this interaction was reduced in inflammatory conditions, whereby PTX3 had no complement-inhibiting activity on inflamed RPE. However, on non-cellular surfaces, PTX3 formed a stable ternary complex with FH and C3b that acted as a “hot spot” for complement inhibition. Our findings suggest a protective role for PTX3 in response to complement dysregulation in AMD and point to a novel mechanism of complement regulation by this pentraxin with potential implications in pathology and pharmacology of AMD.

Drusen and pachydrusen: the definition, pathogenesis, and clinical significance

The pachychoroid disease spectrum encompasses seven major retinal conditions including central serous chorioretinopathy (CSC), polypoidal choroidal vasculopathy (PCV), and pachychoroid neovasculopathy or type I macular neovascularisation (MNV) secondary to chronic persistent thickening and dysfunction of the choroidal vasculature. Drusen are focal yellow-white deposits of extracellular debris, which consist of complement proteins, esterified and nonesterified cholesterol, apolipoproteins, carbohydrates, and trace elements, above the retinal pigment epithelium (RPE) or between the RPE and Bruch's membrane. Although drusen are an essential disease precursor of advanced age-related macular degeneration (AMD), a new entity "pachydrusen" has been identified to be associated with some of the enitites that constitute the pachychoroid spectrum. It remains to be determined what the exact differences are between soft drusen, pseudodrusen, and pachydrusen in terms of phenotype, genotype, and pathogenesis. Improving our knowledge in these areas will inevitably improve our understanding of their clinical significance especially as in disease prediction in AMD and the pachychroid spectrum disorders. It remains controversial whether PCV is a subtype of AMD. Understanding the pathogenesis of different types of drusen may also help in addressing if phenotype and/or genotype of type 1 MNV associated with pachychoroid are similar to type 1 MNV related to AMD. Furthermore, because pachydrusen links two pachychoroid diseases, CSC and PCV, it is also of great interest to investigate if CSC is an early stage or a predictor of PCV in future research. In this review, we share our experience in clinical practice and the latest published evidence-based literature to emphasize the differences and similarities in morphology, pathogenesis, and clinical significance of drusen and pachydrusen, a new member of the pachychoroid spectrum disorders.

The Diagnosis and Treatment of Age-Related Macular Degeneration

BACKGROUND

Age-related macular degeneration (AMD) is thought to cause approximately 9% of all cases of blindness worldwide. In Germany, half of all cases of blindness and high-grade visual impairment are due to AMD. In this review, the main risk factors, clinical manifestations, and treatments of this disease are presented.

METHODS

This review is based on pertinent publications retrieved by a selective search in PubMed for original articles and reviews, as well as on current position statements by the relevant specialty societies.

RESULTS

AMD is subdivided into early, intermediate, and late stages. The early stage is often asymptomatic; patients in the other two stages often have distorted vision or central visual field defects. The main risk factors are age, genetic predisposition, and nicotine consumption. The number of persons with early AMD in Germany rose from 5.7 million in 2002 to ca. 7 million in 2017. Late AMD is subdivided into the dry late form of the disease, for which there is no treatment at present, and the exudative late form, which can be treated with the intravitreal injection of VEGF inhibitors.

CONCLUSION

More research is needed on the dry late form of AMD in particular, which is currently untreatable. The treatment of the exudative late form with VEGF inhibitors is labor-intensive and requires a close collaboration of the patient, the ophthalmologist, and the primary care physician.

Cholesterol Regulation in Age-Related Macular Degeneration: A Framework for Mathematical Modelling of Drusen Biogenesis

In age-related macular degeneration (AMD), there is, in common with many other age-related diseases, the need to distinguish between changes in the ageing eye that lead to disease and those changes that are considered part of a healthy, ageing eye. Various studies investigating the multitude of mechanisms involved in the aetiology of AMD exist within the field of ophthalmology and related medical fields, yet many aspects of it remain poorly understood and only a limited number of therapies are available. A recent study relates drusen's topographically cellular characteristics to the neural retina's metabolic needs and associated cholesterol involvement within the retina. In particular, there is a need to fully understand the maintenance of cholesterol homeostasis in the retina to prevent normal ageing processes from being perturbed towards maculopathy. Here, we present an extensive review of the clinical and physiological features of the ageing retina, as well as mechanisms implicated in pathology, synthesised from a vast body of the published literature. We use this novel synthesis to construct a comprehensive process schematic, encompassing all key species and physiological processes such as nutrients, waste and lipoprotein management. We are therefore able to express these processes in a mathematical language via a comprehensive modelling framework, comprising a set of twenty-three equations spanning three distinct biological compartments. This very general modelling framework may now be adapted to more focused studies on individual mechanisms, processes or components underlying of the many facets of AMD. As an example of such a focused application, we conclude this article with a one-compartment, four-species model of the retinal pigment epithelium, which considers the parametric conditions under which either cholesterol homeostasis or unregulated accumulation of cholesterol may obtain in the ageing eye.

Association of Choroidal Thickness with Intermediate Age-Related Macular Degeneration in a Japanese Population

PURPOSE

To determine the relationship of choroidal thickness with the early stages of age-related macular degeneration (AMD) and their disease features in a Japanese population.

DESIGN

Cross-sectional survey.

PARTICIPANTS

A total of 1293 Japanese persons 65 to 86 years of age residing in the Saku area who underwent eye screening as part of the Japan Public Health Center-based Prospective Study.

METHODS

Comprehensive ophthalmic assessment included fundus photography, measurement of intraocular pressure, and determination of refractive status. OCT with enhanced depth imaging mode was performed and subfoveal choroidal thickness was assessed. Multinomial logistic regression models were used to assess the relationships of choroidal thickness with the early stages of AMD, namely early AMD and intermediate AMD, and their disease features, after adjustment for potential confounders.

MAIN OUTCOME MEASURES

Relationship of choroidal thickness with early AMD, intermediate AMD, and their disease features.

RESULTS

Of 1293 potential participants, 901 (mean age, 73.2 years) had choroidal thickness data, fundus photographs of sufficient quality, and no concomitant retinal disease (including 5 with late AMD). Mean choroidal thickness was 246.1 μm, 15.1% had early AMD, and 9.0% had intermediate AMD. After adjustment for age, gender, and refractive status, choroidal thickness was associated positively with presence of intermediate AMD (for each 1- standard deviation [SD] μm increase: odds ratio [OR], 1.43; 95% confidence interval [CI], 1.13-1.81), whereas no significant association was found with presence of early AMD. Among intermediate AMD features, choroidal thickness was associated positively with presence of AMD pigmentary abnormalities (associated with at least medium drusen; for each 1-SD μm increase: OR, 2.21; 95% CI, 1.42-3.42), whereas no significant association was found with presence of large drusen alone. In addition, among large drusen subtypes, choroidal thickness was associated positively with presence of pachydrusen (for each 1-SD μm increase: OR, 1.53; 95% CI, 1.10-2.13). Furthermore, exploratory analysis revealed that choroidal thickness was associated positively with presence of non-AMD pigmentary abnormalities (for each 1-SD μm increase: OR, 1.92; 95% CI, 1.31-2.18).

CONCLUSIONS

Choroidal thickness seems to be associated with the pathology of intermediate AMD and its features in Asians.

Integrated Microarray and RNAseq Transcriptomic Analysis of Retinal Pigment Epithelium/Choroid in Age-Related Macular Degeneration

We report for the first time an integrated transcriptomic analysis of RPE/choroid dysfunction in AMD (mixed stages) based on combining data from publicly available microarray (GSE29801) and RNAseq (GSE135092) datasets aimed at increasing the ability and power of detection of differentially expressed genes and AMD-associated pathways. The analysis approach employed an integrating quantitative method designed to eliminate bias among different transcriptomic studies. The analysis highlighted 764 meta-genes (366 downregulated and 398 upregulated) in macular AMD RPE/choroid and 445 meta-genes (244 downregulated and 201 upregulated) in non-macular AMD RPE/choroid. Of these, 731 genes were newly detected as differentially expressed (DE) genes in macular AMD RPE/choroid and 434 genes in non-macular AMD RPE/choroid compared with controls. Over-representation analysis of KEGG pathways associated with these DE genes mapped revealed two most significantly associated biological processes in macular RPE/choroid in AMD, namely the neuroactive ligand-receptor interaction pathway (represented by 30 DE genes) and the extracellular matrix-receptor interaction signaling pathway (represented by 12 DE genes). Furthermore, protein-protein interaction (PPI) network identified two central hub genes involved in the control of cell proliferation/differentiation processes, HDAC1 and CDK1. Overall, the analysis provided novel insights for broadening the exploration of AMD pathogenesis by extending the number of molecular determinants and functional pathways that underpin AMD-associated RPE/choroid dysfunction.

Optical Coherence Tomography-Angiography in Geographic Atrophy

Geographic atrophy (GA) represents the non-exudative late stage of age-related macular degeneration and constitutes a leading cause of legal blindness in the developed world. It is characterized by areas of loss of outer retinal layers including photoreceptors, degeneration of the retinal pigment epithelium, and rarefication of the choriocapillaris. As all three layers are functionally connected, the precise temporal sequence and relative contribution of these layers towards the development and progression of GA is unclear. The advent of optical coherence tomography angiography (OCT-A) has allowed for three-dimensional visualization of retinal blood flow. Using OCT-A, recent studies have demonstrated that choriocapillaris flow alterations are particularly associated with the development of GA, exceed atrophy boundaries spatially, and are a prognostic factor for future GA progression. Furthermore, OCT-A may be helpful to differentiate GA from mimicking diseases. Evidence for a potential protective effect of specific forms of choroidal neovascularization in the context of GA has been reported. This article aims to give a comprehensive review of the current literature concerning the application of OCT-A in GA, and summarizes the opportunities and limitations with regard to pathophysiologic considerations, differential diagnosis, study design, and patient assessment.

Renin-Angiotensin System Inhibitor Usage and Age-Related Macular Degeneration among Hypertensive Patients: Results from the National Health and Nutrition Examination Survey, 2005-2008

Purpose

To assess whether renin-angiotensin system inhibitor (RASI) utilization is associated with age-related macular degeneration (AMD) prevalence among hypertensive patients.

Methods

A US population-based, cross-sectional study was conducted. 3,023 hypertensive participants aged 40 years and older with gradable retinal images and ascertained RASI usage in the National Health and Nutrition Examination Survey (NHANES), 2005-2008, were finally enrolled into the study. RASI usage was obtained by interview, and AMD was determined through retinal image assessment. We performed multivariable analyses to assess the relationship between utilization of RASIs and AMD prevalence. We also took drug treatment duration into account, in order to better understand the effects of RASIs.

Results

Multivariable logistic regression analyses revealed that AMD prevalence had no significant association with RASI usage but was inversely correlated with RASI treatment duration (odds ratio (OR) = 0.87, 95% confidence interval (CI) = 0.78-0.98, p=0.02). Long-term usage (>5 years) of RASIs was significantly associated with not only reduced overall risk of AMD (OR = 0.23, 95% CI = 0.14-0.38, p < 0.001) but also lower propensity to have early (OR = 0.23, 95% CI = 0.14-0.37, p < 0.001) and late (OR = 0.25, 95% CI = 0.07-0.87, p=0.03) AMD. Furthermore, long-term RASI users were less prone to develop soft drusen (OR = 0.67, 95% CI = 0.45-0.99, p=0.04) and geographic atrophy (GA) (OR = 0.39, 95% CI = 0.22-0.71, p=0.003).

Conclusions

Evidence supporting that RASI utilization could directly protect against AMD in hypertensive patients was still insufficient, but long-term RASI treatment seemed to be beneficial for both early and late AMD, implicating a promising therapeutic approach that RASIs might offer for AMD prevention and management.

Local Abundance of Macular Xanthophyll Pigment Is Associated with Rod- and Cone-Mediated Vision in Aging and Age-Related Macular Degeneration

Purpose

We assessed the association between the abundance of macular xanthophyll carotenoid pigment using dual-wavelength autofluorescence and multimodal vision testing including rod-mediated dark adaptation (RMDA), a measure of retinoid re-supply, in adults ≥60 years old with and without age-related macular degeneration (AMD).

Methods

AMD severity was determined using the nine-step Age-Related Eye Disease Study grading. Tests probed cones (best-corrected visual acuity, contrast sensitivity), cones and rods (low-luminance visual acuity, low-luminance deficit, mesopic light sensitivity), or rods only (scotopic light sensitivity, RMDA). Signal attenuation by macular pigment optical density (MPOD) was estimated using a ratio of blue and green autofluorescence signal to yield mean MPOD in a 1°-diameter fovea-centered disk, mean MPOD in a 2°-diameter disk centered on a perifoveal RMDA test location, and macular pigment optical volume (MPOV, or integrated MPOD) in a 4°-diameter fovea-centered disk. Age-adjusted associations between vision and imaging measures were determined.

Results

In 88 eyes of 88 subjects (age, 74.9 ± 5.8 years) with normal eyes (n = 32), early AMD (n = 23), or intermediate AMD (n = 33), foveal and perifoveal MPOD and MPOV were higher in the AMD eyes than in the normal eyes. At the RMDA test location, higher MPOD was unrelated to AMD severity but was associated with faster RMDA.

Conclusions

In older adults with and without AMD, higher macular xanthophyll concentrations are associated with better best-corrected visual acuity and RMDA. Data are consistent with a model of cone resilience and rod vulnerability in aging and AMD and can be further explored in a larger sample study.

Altered photoreceptor metabolism in mouse causes late stage age-related macular degeneration-like pathologies

The main cause for blindness in the elderly worldwide is age-related macular degeneration (AMD). What causes AMD remains unknown. The high metabolic demands of photoreceptors are thought to contribute to disease pathogenesis, yet whether photoreceptor metabolism differs in individuals with AMD has not been determined. Here, we show that photoreceptor metabolism does differ between diseased and nondiseased individuals. Mimicking the metabolic profile of diseased individuals in mouse resulted in the similar advanced pathologies as those that cause blindness in humans. A disease model with photoreceptors as a contributing factor explains also why AMD affects preferentially the macula; it is the region of highest photoreceptor density. The data might open new avenues to study the role of PRs in disease pathogenesis.

Age-related macular degeneration (AMD) is the leading cause of blindness in the elderly. While the histopathology of the different disease stages is well characterized, the cause underlying the progression, from the early drusen stage to the advanced macular degeneration stage that leads to blindness, remains unknown. Here, we show that photoreceptors (PRs) of diseased individuals display increased expression of two key glycolytic genes, suggestive of a glucose shortage during disease. Mimicking aspects of this metabolic profile in PRs of wild-type mice by activation of the mammalian target of rapamycin complex 1 (mTORC1) caused early drusen-like pathologies, as well as advanced AMD-like pathologies. Mice with activated mTORC1 in PRs also displayed other early disease features, such as a delay in photoreceptor outer segment (POS) clearance and accumulation of lipofuscin in the retinal-pigmented epithelium (RPE) and of lipoproteins at the Bruch’s membrane (BrM), as well as changes in complement accumulation. Interestingly, formation of drusen-like deposits was dependent on activation of mTORC1 in cones. Both major types of advanced AMD pathologies, including geographic atrophy (GA) and neovascular pathologies, were also seen. Finally, activated mTORC1 in PRs resulted in a threefold reduction in di-docosahexaenoic acid (DHA)–containing phospholipid species. Feeding mice a DHA-enriched diet alleviated most pathologies. The data recapitulate many aspects of the human disease, suggesting that metabolic adaptations in photoreceptors could contribute to disease progression in AMD. Identifying the changes downstream of mTORC1 that lead to advanced pathologies in mouse might present new opportunities to study the role of PRs in AMD pathogenesis.

Functionally validated imaging endpoints in the Alabama study on early age-related macular degeneration 2 (ALSTAR2): design and methods

Background

Age-related macular degeneration (AMD), a leading cause of irreversible vision impairment in the United States and globally, is a disease of the photoreceptor support system involving the retinal pigment epithelium (RPE), Bruch’s membrane, and the choriocapillaris in the setting of characteristic extracellular deposits between outer retinal cells and their blood supply. Research has clearly documented the selective vulnerability of rod photoreceptors and rod-mediated (scotopic) vision in early AMD, including delayed rod-mediated dark adaptation (RMDA) and impaired rod-mediated light and pattern sensitivity. The unifying hypothesis of the Alabama Study on Early Macular Degeneration (ALSTAR2) is that early AMD is a disease of micronutrient deficiency and vascular insufficiency, due to detectable structural changes in the retinoid re-supply route from the choriocapillaris to the photoreceptors. Functionally this is manifest as delayed rod-mediated dark adaptation and eventually as rod-mediated visual dysfunction in general.

Methods

A cohort of 480 older adults either in normal macular health or with early AMD will be enrolled and followed for 3 years to examine cross-sectional and longitudinal associations between structural and functional characteristics of AMD. Using spectral domain optical coherence tomography, the association between (1) subretinal drusenoid deposits and drusen, (2) RPE cell bodies, and (3) the choriocapillaris’ vascular density and rod- and cone-mediated vision will be examined. An accurate map and timeline of structure-function relationships in aging and early AMD gained from ALSTAR2, especially the critical transition from aging to disease, will identify major characteristics relevant to future treatments and preventative measures.

Discussion

A major barrier to developing treatments and prevention strategies for early AMD is a limited understanding of the temporal interrelationships among structural and functional characteristics while transitioning from aging to early AMD. ALSTAR2 will enable the development of functionally valid, structural biomarkers for early AMD, suitable for use in forthcoming clinical trials as endpoint/outcome measures. The comprehensive dataset will also allow hypothesis-testing for mechanisms that underlie the transition from aging to AMD, one of which is a newly developed Center-Surround model of cone resilience and rod vulnerability.

Trial registration

ClinicalTrials.gov Identifier NCT04112667, October 7, 2019.

Unstimulated, Serum-free Cultures of Retinal Pigment Epithelium Excrete Large Mounds of Drusen-like Deposits

Purpose: A hallmark of age-related macular degeneration is the accumulation of deposits of lipids and proteins, called drusen, in Bruch's membrane. Several culture models of retinal pigment epithelia (RPE) develop drusen-like deposits. We examined whether prolonged culture of RPE with a retina-like tissue affected the number or size of these deposits. Methods: RPE and retinal progenitor cells (RPC) were differentiated from induced pluripotent stem cells derived from fetal tissue and maintained in serum-free medium containing the B27 supplement. RPE was cultured on Transwell filter inserts, and RPC were cultured on a planar matrix composed of gelatin, hyaluronic acid, and chondroitin sulfate. After seeding the filter, RPC were layered on top of the RPE. RPE ± RPC were cultured for six months. The function of RPE tight junctions was assessed by the transepithelial electrical resistance. Cultures were stained for actin, neutral lipids, APOE, TIMP3, vitronectin, and calcium deposits. Morphometric analysis was used to determine the number and volume of the "druse". Results: After six months, the TER was greater for the co-cultures (304 ± 11 Ω× cm² vs 243 ± 7 Ω× cm², p < .01). RPE formed mounds of druse-like deposits that contained, vitronectin, APOE, TIMP3 and calcium deposits, but lipids were undetected. The mounds overlay areas of the filter where no lipid was detected in the pores, and the RPE overlying the mounds was often thin. The number of "druse"/100,000 μm² was 5.0 ± 0.4 (co-cultures) vs 2.3 ± 0.1 (monocultures) (p < .05). The total volume of "drusen"/100,000 μm³ was 15,133 ± 1544 (co-cultures) vs 5,993 ± 872 (monocultures) (p < .05). There was no statistical difference between the size-distribution of druse-like particles formed by each culture. Conclusions: Covering the apical membrane of RPE with a thick tissue increased the number of druse-like deposits. The apparent size limitation of the deposits may reflect the apparent interruption of the of lipid cycle found at the basal membrane of the RPE.

Spatial distribution of macular pigment estimated by autofluorescence imaging in elderly Japanese individuals

PURPOSE

To determine the spatial distribution types of macular pigment (MP) in elderly Japanese individuals and to consider their origin.

STUDY DESIGN

Observational case series.

METHODS

Local MP optical density (MPOD) at some eccentricities and MP volume were measured using the MPOD module of a MultiColor Spectralis in 96 pseudophakic eyes of 96 participants (age range, 52-86 years; mean age, 72.8 ± 8.3 years). The MP distribution types were determined from the MP spatial profiles. The retinal thickness (RT) at the foveal center, at both 0.5° and 0.9° eccentricities, and the foveal width were measured using optical coherence tomography.

RESULTS

The mean local MPOD at the foveal center was 0.79. Spatial distribution was classified into four types: central peak (24.0%), ring-like (40.6%), intermediate (22.9%), and central dip (12.5%). The ring-like type was the most frequent in these Japanese participants. The central-peak type showed lower MPOD than did the other types in the area outside 0.9°. The ring-like type occurred frequently in eyes with small RT at 0.5° and wider foveal width. A rough contour of the Müller cell cone was found more frequently in the central-dip type than in the other types.

CONCLUSIONS

The present characteristics of the different distribution patterns could be explained by the hypothesis that MP presents mainly in the Müller cell cone within 0.5° and in Müller cells in the outer and inner plexiform layers in the area outside 0.5°. The anatomic characteristics of Müller cells at the fovea and parafovea likely affect the MP distribution.

The Interplay between Retinal Pathways of Cholesterol Output and Its Effects on Mouse Retina

In mammalian retina, cholesterol excess is mainly metabolized to oxysterols by cytochromes P450 27A1 (CYP27A1) and 46A1 (CYP46A1) or removed on lipoprotein particles containing apolipoprotein E (APOE). In contrast, esterification by sterol-O-acyltransferase 1 (SOAT) plays only a minor role in this process. Accordingly, retinal cholesterol levels are unchanged in Soat1^-/- mice but are increased in Cyp27a1^-/-Cyp46a1^-/- and Apoe^-/- mice. Herein, we characterized Cyp27a1^-/-Cyp46a1^-/-Soat1^-/- and Cyp27a1^-/-Cyp46a1^-/-Apoe^-/- mice. In the former, retinal cholesterol levels, anatomical gross structure, and vasculature were normal, yet the electroretinographic responses were impaired. Conversely, in Cyp27a1^-/-Cyp46a1^-/-Apoe^-/- mice, retinal cholesterol levels were increased while anatomical structure and vasculature were unaffected with only male mice showing a decrease in electroretinographic responses. Sterol profiling, qRT-PCR, proteomics, and transmission electron microscopy mapped potential compensatory mechanisms in the Cyp27a1^-/-Cyp46a1^-/-Soat1^-/- and Cyp27a1^-/-Cyp46a1^-/-Apoe^-/- retina. These included decreased cholesterol biosynthesis along with enhanced formation of intra- and extracellular vesicles, possibly a reserve mechanism for lowering retinal cholesterol. In addition, there was altered abundance of proteins in Cyp27a1^-/-Cyp46a1^-/-Soat1^-/- mice that can affect photoreceptor function, survival, and retinal energy homeostasis (glucose and fatty acid metabolism). Therefore, the levels of retinal cholesterol do not seem to predict retinal abnormalities, and it is rather the network of compensatory mechanisms that appears to determine retinal phenotype.

Quantifying Retinal Pigment Epithelium Dysmorphia and Loss of Histologic Autofluorescence in Age-Related Macular Degeneration

Purpose

Lipofuscin and melanolipofuscin organelles in retinal pigment epithelium (RPE) cells are signal sources for clinical fundus autofluorescence (AF). To elucidate the subcellular basis of AF imaging, we identified, characterized, and quantified the frequency of RPE morphology and AF phenotypes in donor eyes with age-related macular degeneration (AMD).

Methods

In 25 RPE-Bruch's membrane flat mounts from 25 eyes, we analyzed 0.4-μm z-stack epifluorescence images of RPE stained with phalloidin for actin cytoskeleton. Using a custom ImageJ plugin, we classified cells selected in a systematic unbiased fashion in six phenotypes representing increasing degrees of pathology. For each cell, area, AF intensity, and number of Voronoi neighbors were compared with phenotype 1 (uniform AF, polygonal morphology) via generalized estimating equations. We also analyzed each cell's neighborhood.

Results

In 29,323 cells, compared with phenotype 1, all other phenotypes, in order of increasing pathology, had significantly larger area, reduced AF, and more variable number of neighbors. Neighborhood area and AF showed similar, but subtler, trends. Cells with highly autofluorescent granule aggregates are no more autofluorescent than others and are in fact lower overall in AF. Pre-aggregates were found in phenotype 1. Phenotype 2, which exhibited degranulation despite normal cytoskeleton, was the most numerous nonhealthy phenotype (16.23%).

Conclusions

Despite aggregation of granules that created hyperAF aggregates within cells, overall AF on a per cell basis decreased with increasing severity of dysmorphia (abnormal shape). Data motivate further development of subcellular resolution in clinical fundus AF imaging and inform an ongoing reexamination of the role of lipofuscin in AMD.

Diet Mimicking "Fast Food" Causes Structural Changes to the Retina Relevant to Age-Related Macular Degeneration

Introduction: Metabolic syndrome is a disorder characterized by a constellation of findings including truncal obesity, elevated blood pressure, abnormal cholesterol levels, and high blood glucose. Recent evidence suggests that metabolic syndrome may be associated with increased risk of age-related macular degeneration (AMD) and other eye diseases. Recently, C57BL/6J wild-type mice fed with a "fast food" diet consisting of high fat, cholesterol, and fructose-supplemented water showed unique systemic pathology consistent with metabolic syndrome and nonalcoholic steatohepatitis. Additionally, these mice showed higher levels of fibrosis, inflammation, endoplasmic reticulum stress, and mitochondrial dysfunction compared to mice fed with only a high-fat diet alone. Since similar pathways are activated in AMD, we sought to determine whether mice fed a "fast food" diet exhibited retinal changes.Methods: 3-month-old wild-type mice were randomized to a standard chow (n = 11) or a "fast food" (n = 18) diet and fed for 9 months. At 1 year of age, tissues were collected and retinas were analyzed using transmission electron microscopy. Quantitative measures of Bruch's membrane thickness and retinal pigment epithelium (RPE) cell counts were performed.Results: "Fast food" fed mice showed ocular pathology relevant to various stages of AMD including basal laminar deposits, focal thickening of Bruch's membrane, and a significant loss of RPE cells.Discussion/conclusion: A wild-type mouse model of metabolic syndrome fed a "fast food" diet developed changes to the retina similar to some of the pathologic features seen in AMD. Further investigations into this and similar animal models as well as further epidemiological studies are needed to more clearly define the association between metabolic syndrome and AMD.

Interactions of the choroid, Bruch's membrane, retinal pigment epithelium, and neurosensory retina collaborate to form the outer blood-retinal-barrier

The three interacting components of the outer blood-retinal barrier are the retinal pigment epithelium (RPE), choriocapillaris, and Bruch's membrane, the extracellular matrix that lies between them. Although previously reviewed independently, this review integrates these components into a more wholistic view of the barrier and discusses reconstitution models to explore the interactions among them. After updating our understanding of each component's contribution to barrier function, we discuss recent efforts to examine how the components interact. Recent studies demonstrate that claudin-19 regulates multiple aspects of RPE's barrier function and identifies a barrier function whereby mutations of claudin-19 affect retinal development. Co-culture approaches to reconstitute components of the outer blood-retinal barrier are beginning to reveal two-way interactions between the RPE and choriocapillaris. These interactions affect barrier function and the composition of the intervening Bruch's membrane. Normal or disease models of Bruch's membrane, reconstituted with healthy or diseased RPE, demonstrate adverse effects of diseased matrix on RPE metabolism. A stumbling block for reconstitution studies is the substrates typically used to culture cells are inadequate substitutes for Bruch's membrane. Together with human stem cells, the alternative substrates that have been designed offer an opportunity to engineer second-generation culture models of the outer blood-retinal barrier.

Subretinal Drusenoid Deposits in the Elderly in a Population-Based Study (the Montrachet Study)

Purpose

The aim of this study was to investigate the prevalence of subretinal drusenoid deposits (SDD) and to identify associated factors in an elderly population.

Methods

The participants of the population-based Montrachet study underwent an exhaustive ophthalmologic examination, including color fundus photography and macular spectral domain-optical coherence tomography (SD-OCT), coupled with infrared reflectance imaging. The presence of SDD and other age-related macular degeneration lesions, according to the European Eye Epidemiology SD-OCT classification of macular diseases, and subfoveal choroidal thickness were recorded. Moreover, the association of SDD and both clinical and demographic factors as well as plasma levels of vitamin E and lutein/zeaxanthin (L/Z) were analyzed.

Results

The mean age of patients was 82.3 ± 3.8 years and 62.7% were female. The prevalence of SDD was 18.1% (n = 205) in the subjects with at least one eye interpretable (n = 1135). In multivariate analysis, SDD was positively associated with increasing age (OR, 4.6; 95% CI, 2.8-7.7; P < 0.001 for subjects aged >85 years), female sex (OR, 1.7; 95% CI, 1.2-2.4; P = 0.005), and plasma L/Z level (OR, 1.2; 95% CI, 1.0-1.5; P = 0.039), and negatively associated with lipid-lowering drugs use (OR, 0.5; 95% CI, 0.3-0.9; P = 0.014 for statin medications) and subfoveal choroidal thickness (OR, 0.8; 95% CI, 0.7-0.9; P = 0.002).

Conclusions

The prevalence of SDD was high in subjects older than 75 years, more frequent in women, and was associated with a thinner choroid. The association with lipid-lowering drugs deserves further investigation.

Pathological Mineralization: The Potential of Mineralomics

Pathological mineralization has been reported countless times in the literature and is a well-known phenomenon in the medical field for its connections to a wide range of diseases, including cancer, cardiovascular, and neurodegenerative diseases. The minerals involved in calcification, however, have not been directly studied as extensively as the organic components of each of the pathologies. These have been studied in isolation and, for most of them, physicochemical properties are hitherto not fully known. In a parallel development, materials science methods such as electron microscopy, spectroscopy, thermal analysis, and others have been used in biology mainly for the study of hard tissues and biomaterials and have only recently been incorporated in the study of other biological systems. This review connects a range of soft tissue diseases, including breast cancer, age-related macular degeneration, aortic valve stenosis, kidney stone diseases, and Fahr’s syndrome, all of which have been associated with mineralization processes. Furthermore, it describes how physicochemical material characterization methods have been used to provide new information on such pathologies. Here, we focus on diseases that are associated with calcium-composed minerals to discuss how understanding the properties of these minerals can provide new insights on their origins, considering that different conditions and biological features are required for each type of mineral to be formed. We show that mineralomics, or the study of the properties and roles of minerals, can provide information which will help to improve prevention methods against pathological mineral build-up, which in the cases of most of the diseases mentioned in this review, will ultimately lead to new prevention or treatment methods for the diseases. Importantly, this review aims to highlight that chemical composition alone cannot fully support conclusions drawn on the nature of these minerals.

Dyslipidemia in retinal metabolic disorders

The light‐sensitive photoreceptors in the retina are extremely metabolically demanding and have the highest density of mitochondria of any cell in the body. Both physiological and pathological retinal vascular growth and regression are controlled by photoreceptor energy demands. It is critical to understand the energy demands of photoreceptors and fuel sources supplying them to understand neurovascular diseases. Retinas are very rich in lipids, which are continuously recycled as lipid‐rich photoreceptor outer segments are shed and reformed and dietary intake of lipids modulates retinal lipid composition. Lipids (as well as glucose) are fuel substrates for photoreceptor mitochondria. Dyslipidemia contributes to the development and progression of retinal dysfunction in many eye diseases. Here, we review photoreceptor energy demands with a focus on lipid metabolism in retinal neurovascular disorders.

Clinical and genetic characteristics of pachydrusen in patients with exudative age-related macular degeneration

We investigated the clinical and genetic characteristics of patients with unilateral exudative age-related macular degeneration (AMD), including typical AMD, polypoidal choroidal vasculopathy, and retinal angiomatous proliferation, in whom pachydrusen was seen. Patients with unilateral exudative AMD with at least a 12-month follow-up period were included. According to the fellow eye condition, 327 consecutive patients were classified into 4 groups: Group 0: no drusen (42.8%), Group 1: pachydrusen (12.2%), Group 2: soft drusen (30.3%), Group 3: pseudodrusen with or without soft drusen (14.7%). Development of exudative AMD in the fellow eye was retrospectively studied for a 60-month period and this inter-group comparisons were performed. Genotyping was performed for ARMS2 A69S and CFH I62V. The thickness of the choroid in the fellow eyes increased significantly in Group 1 than in other groups (all P < 1.0 × 10⁻⁷). The development of exudative AMD in the fellow eye was significantly less frequent in Group 1 than in Groups 2 or 3 (P = 0.022 and 0.0015, respectively). Risk allele frequency of ARMS2 A69S was significantly lower in Group 1 than in Group 2 and 3 (all P < 1.0 × 10⁻⁴). Patients with pachydrusen have genetic and clinical characteristics distinct from those of soft drusen and pseudodrusen.

Dysregulated claudin-5 cycling in the inner retina causes retinal pigment epithelial cell atrophy

Age-related macular degeneration (AMD) is the leading cause of central retinal vision loss worldwide, with an estimated 1 in 10 people over the age of 55 showing early signs of the condition. There are currently no forms of therapy available for the end stage of dry AMD, geographic atrophy (GA). Here, we show that the inner blood-retina barrier (iBRB) is highly dynamic and may play a contributory role in GA development. We have discovered that the gene CLDN5, which encodes claudin-5, a tight junction protein abundantly expressed at the iBRB, is regulated by BMAL1 and the circadian clock. Persistent suppression of claudin-5 expression in mice exposed to a cholesterol-enriched diet induced striking retinal pigment epithelium (RPE) cell atrophy, and persistent targeted suppression of claudin-5 in the macular region of nonhuman primates induced RPE cell atrophy. Moreover, fundus fluorescein angiography in human and nonhuman primate subjects showed increased retinal vascular permeability in the evening compared with the morning. These findings implicate an inner retina-derived component in the early pathophysiological changes observed in AMD, and we suggest that restoring the integrity of the iBRB may represent a novel therapeutic target for the prevention and treatment of GA secondary to dry AMD.

Age-Related Scattered Hypofluorescent Spots on Late-Phase Indocyanine Green Angiography as Precursor Lesions of Polypoidal Choroidal Vasculopathy

Purpose

Age-related scattered hypofluorescent spots on late-phase indocyanine green angiography (ASHS-LIA) might represent lipid accumulation in Bruch's membrane in the form of basal linear deposits (BlinD). The present study was conducted to describe the clinical characteristics of polypoidal choroidal vasculopathy (PCV) associated with ASHS-LIA.

Methods

Consecutive patients with treatment-naïve PCV who underwent color fundus photography (FP), fundus fluorescein angiography (FFA), indocyanine green angiography (ICGA), and spectral-domain optical coherence tomography (SD-OCT) at the Zhongshan Ophthalmic Center from June 2016 through May 2018, were reviewed. ASHS-LIA and choroidal vascular hyperpermeability (CVH) were evaluated by ICGA. Subfoveal choroidal thickness (SFCT) was assessed by SD-OCT.

Results

A total of 187 patients were eligible for inclusion in this study (mean, 63.2 ± 7.6 years; range, 41-85 years). Of these patients, 117 (62.6%) showed ASHS-LIA, 57 (30.5%) had bilateral lesions and 70 (37.4%) showed CVH. Moreover, compared with patients without ASHS-LIA, PCV patients with ASHS-LIA were older (P = 0.001), more frequently had bilateral lesions (P = 0.001), and less frequently showed CVH (P = 0.006). SFCT in eyes with ASHS-LIA was significantly greater than that in eyes without ASHS-LIA after adjusting for age, sex, and CVH (P = 0.026). Nevertheless, there was no significant difference in best-corrected visual acuity or lesion characteristics between the two groups.

Conclusions

ASHS-LIA, which is very common in PCV patients, might be involved in the pathogenesis of PCV. PCV with ASHS-LIA was more frequently associated with bilateral involvement, less CVH, and a thicker choroid than PCV without ASHS-LIA.

Peripheral Retinal Lesions in Eyes with Age-Related Macular Degeneration Using Ultra-Widefield Imaging: A Systematic Review with Meta-analyses

TOPIC

Age-related macular degeneration (AMD) is highly prevalent among the elderly. We systematically reviewed the literature to provide an overview of ultra-widefield imaging (UWFI) of peripheral retinal lesions in AMD.

CLINICAL RELEVANCE

Information regarding retinal characteristics and prevalence of AMD is based mainly on studies using color photography of the central retina, where early and potentially severe manifestations of the disease are found. However, this approach has the effect of neglecting the periphery. Studies using UWFI provide new evidence to show that clinical features associated with AMD are not exclusive to the area of the macula.

METHODS

Eligible studies had to detect lesions of the peripheral retina (based on the original definition of a standard macular grid, with the addition of 2 zones classed as peripheral) using UWFI in eyes with AMD. Ultra-widefield imaging included pseudocolor photography, fundus autofluorescence, fluorescein angiography, and indocyanine green angiography. Eligibility was restricted to human participants and studies written in English. We searched the bibliographic databases PubMed, the Cochrane Library, EMBASE, and the Web of Science on March 27, 2018. We calculated the prevalence of peripheral findings in eyes with AMD and performed similar meta-analyses on the healthy control group. A random-effects model was used because of possible study heterogeneity.

RESULTS

Twelve studies were eligible for the review, which included 3261 or more eyes. Studies were clinic based, apart from 1 study that was a random population sample of individuals 62 years of age or older. Studies were cross-sectional in nature, apart from 1 case-control study. The peripheral lesions most commonly observed were drusen, atrophy, and changes to the retinal pigment epithelium. In eyes with AMD, peripheral lesions were found in 82.7% of eyes (confidence interval, 78.4%-86.7%) compared with 33.3% of healthy eyes (confidence interval, 28.3%-38.5%).

CONCLUSIONS

Peripheral changes were found to be highly prevalent in eyes with AMD, supporting the claim that the disease is panretinal and not macula only. The clinical significance of peripheral lesions in AMD remains incompletely understood, and therefore, further UWFI studies are recommended.

On the origin of proteins in human drusen: The meet, greet and stick hypothesis

Retinal drusen formation is not only a clinical hallmark for the development of age-related macular degeneration (AMD) but also for other disorders, such as Alzheimer's disease and renal diseases. The initiation and growth of drusen is poorly understood. Attention has focused on lipids and minerals, but relatively little is known about the origin of drusen-associated proteins and how they are retained in the space between the basal lamina of the retinal pigment epithelium and the inner collagenous layer space (sub-RPE-BL space). While some authors suggested that drusen proteins are mainly derived from cellular debris from processed photoreceptor outer segments and the RPE, others suggest a choroidal cell or blood origin. Here, we reviewed and supplemented the existing literature on the molecular composition of the retina/choroid complex, to gain a more complete understanding of the sources of proteins in drusen. These "drusenomics" studies showed that a considerable proportion of currently identified drusen proteins is uniquely originating from the blood. A smaller, but still large fraction of drusen proteins comes from both blood and/or RPE. Only a small proportion of drusen proteins is uniquely derived from the photoreceptors or choroid. We next evaluated how drusen components may "meet, greet and stick" to each other and/or to structures like hydroxyapatite spherules to form macroscopic deposits in the sub-RPE-BL space. Finally, we discuss implications of our findings with respect to the previously proposed homology between drusenogenesis in AMD and plaque formation in atherosclerosis.

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

AMD is a major cause of legal blindness in older adults approachable through multidisciplinary research involving human tissues and patients. AMD is a vascular-metabolic-inflammatory disease, in which two sets of extracellular deposits, soft drusen/basal linear deposit (BLinD) and subretinal drusenoid deposit (SDD), confer risk for end-stages of atrophy and neovascularization. Understanding how deposits form can lead to insights for new preventions and therapy. The topographic correspondence of BLinD and SDD with cones and rods, respectively, suggest newly realized exchange pathways among outer retinal cells and across Bruch's membrane and the subretinal space, in service of highly evolved, eye-specific physiology. This review focuses on soft drusen/BLinD, summarizing evidence that a major ultrastructural component is large apolipoprotein B,E-containing, cholesterol-rich lipoproteins secreted by the retinal pigment epithelium (RPE) that offload unneeded lipids of dietary and outer segment origin to create an atherosclerosis-like progression in the subRPE-basal lamina space. Clinical observations and an RPE cell culture system combine to suggest that soft drusen/BLinD form when secretions of functional RPE back up in the subRPE-basal lamina space by impaired egress across aged Bruch's membrane-choriocapillary endothelium. The soft drusen lifecycle includes growth, anterior migration of RPE atop drusen, then collapse, and atrophy. Proof-of-concept studies in humans and animal models suggest that targeting the “Oil Spill in Bruch's membrane” offers promise of treating a process in early AMD that underlies progression to both end-stages. A companion article addresses the antecedents of soft drusen within the biology of the macula.

Calcified nodules in retinal drusen are associated with disease progression in age-related macular degeneration

Drusen are lipid-, mineral-, and protein-containing extracellular deposits that accumulate between the basal lamina of the retinal pigment epithelium (RPE) and Bruch's membrane (BrM) of the human eye. They are a defining feature of age-related macular degeneration (AMD), a common sight-threatening disease of older adults. The appearance of heterogeneous internal reflectivity within drusen (HIRD) on optical coherence tomography (OCT) images has been suggested to indicate an increased risk of progression to advanced AMD. Here, in a cohort of patients with AMD and drusen, we show that HIRD indicated an increased risk of developing advanced AMD within 1 year. Using multimodal imaging in an independent cohort, we demonstrate that progression to AMD was associated with increasing degeneration of the RPE overlying HIRD. Morphological analysis of clinically imaged cadaveric human eye samples revealed that HIRD was formed by multilobular nodules. Nanoanalytical methods showed that nodules were composed of hydroxyapatite and that they differed from spherules and BrM plaques, other refractile features also found in the retinas of patients with AMD. These findings suggest that hydroxyapatite nodules may be indicators of progression to advanced AMD and that using multimodal clinical imaging to determine the composition of macular calcifications may help to direct therapeutic strategies and outcome measures in AMD.