The complement system in age-related macular degeneration: A review of rare genetic variants and implications for personalized treatment

Mechanism of complement inhibition by a mosquito protein revealed through cryo-EM

Salivary complement inhibitors occur in many of the blood feeding arthropod species responsible for transmission of pathogens. During feeding, these inhibitors prevent the production of proinflammatory anaphylatoxins, which may interfere with feeding, and limit formation of the membrane attack complex which could damage arthropod gut tissues. Salivary inhibitors are, in many cases, novel proteins which may be pharmaceutically useful or display unusual mechanisms that could be exploited pharmaceutically. Albicin is a potent inhibitor of the alternative pathway of complement from the saliva of the malaria transmitting mosquito, Anopheles albimanus. Here we describe the cryo-EM structure of albicin bound to C3bBb, the alternative C3 convertase, a proteolytic complex that is responsible for cleavage of C3 and amplification of the complement response. Albicin is shown to induce dimerization of C3bBb, in a manner similar to the bacterial inhibitor SCIN, to form an inactive complex unable to bind the substrate C3. Size exclusion chromatography and structures determined after 30 minutes of incubation of C3b, factor B (FB), factor D (FD) and albicin indicate that FBb dissociates from the inhibited dimeric complex leaving a C3b-albicin dimeric complex which apparently decays more slowly.

Circulating Anti-Endothelial Cell Antibodies in Patients with Geographic Atrophy Related to Dry Age-Related Macular Degeneration

Background and Objectives: Age-related macular degeneration (AMD) is one of the leading causes of central vision loss among elderly patients, and its dry form accounts for the majority of cases. Although several causes and mechanisms for the development and progression of AMD have previously been identified, the pathogenesis of this complex disease is still not entirely understood. As inflammation and immune system involvement are strongly suggested to play a central role in promoting the degenerative process and stimulating the onset of complications, we aimed to analyze the frequency of serum anti-retinal (ARAs) and anti-endothelial cell antibodies (AECAs) in patients with dry AMD and to determine their relationship with the clinical features of the disease, notably the area of geographic atrophy (GA). Materials and Methods: This study included 41 patients with advanced-stage dry AMD and 50 healthy controls without AMD, matched for gender and age. ARAs were detected by indirect immunofluorescence using monkey retina as an antigen substrate, and the presence of AECAs was determined using cultivated human umbilical vein endothelial cells and primate skeletal muscle. Results: ARAs were detected in 36 (87.8%) AMD patients (titers ranged from 1:20 to 1:320) and in 16 (39.0%) (titers ranged from 1:10 to 1:40) controls (p = 0.0000). Twenty of the forty-one patients (48.8%) were positive for AECAs, while in the control group, AECAs were present only in five sera (10.0%). The titers of AECAs in AMD patients ranged from 1:100 to 1:1000, and in the control group, the AECA titers were 1:100 (p = 0.0001). There were no significant correlations between the presence of AECAs and disease activity. Conclusions: This study demonstrates a higher prevalence of circulating AECAs in patients with dry AMD; however, no correlation was found between the serum levels of these autoantibodies and the area of GA.

Moss-produced human complement factor H with modified glycans has an extended half-life and improved biological activity

Most drugs that target the complement system are designed to inhibit the complement pathway at either the proximal or terminal levels. The use of a natural complement regulator such as factor H (FH) could provide a superior treatment option by restoring the balance of an overactive complement system while preserving its normal physiological functions. Until now, the systemic treatment of complement-associated disorders with FH has been deemed unfeasible, primarily due to high production costs, risks related to FH purified from donors' blood, and the challenging expression of recombinant FH in different host systems. We recently demonstrated that a moss-based expression system can produce high yields of properly folded, fully functional, recombinant FH. However, the half-life of the initial variant (CPV-101) was relatively short. Here we show that the same polypeptide with modified glycosylation (CPV-104) achieves a pharmacokinetic profile comparable to that of native FH derived from human serum. The treatment of FH-deficient mice with CPV-104 significantly improved important efficacy parameters such as the normalization of serum C3 levels and the rapid degradation of C3 deposits in the kidney compared to treatment with CPV-101. Furthermore, CPV-104 showed comparable functionality to serum-derived FH in vitro, as well as similar performance in ex vivo assays involving samples from patients with atypical hemolytic uremic syndrome, C3 glomerulopathy and paroxysomal nocturnal hematuria. CPV-104 - the human FH analog expressed in moss - will therefore allow the treatment of complement-associated human diseases by rebalancing instead of inhibiting the complement cascade.

Age-Related Macular Degeneration and Extramacular Drusen: Genetic Associations in the Coimbra Eye Study

Purpose

To explore the association between the genetics of age-related macular degeneration (AMD) and extramacular drusen (EMD) in patients with and without AMD.

Methods

We included 1753 eyes (912 subjects) with phenotypic characterization regarding AMD and EMD. Genetic sequencing and the genetic risk score (GRS) for AMD were performed according to the EYE-RISK consortium methodology. To test for differences in the GRS from EMD cases, AMD cases, and controls, a clustered Wilcoxon rank-sum test was used. The association of AMD, EMD, and the GRS was evaluated using logistic regression models adjusted for age and sex. Individual associations of common risk variants for AMD with EMD were explored.

Results

EMD were found in 755 eyes: 252 (14.4%) with AMD and 503 (28.7%) without. In total, 122 eyes (7.0%) had only AMD, and 876 (50.0%) were controls. EMD were strongly associated with AMD (odds ratio [OR], 3.333; 95% confidence interval [CI], 2.356-4.623; P < 0.001). The GRS was associated with an increased risk of AMD (OR, 1.416; 95% CI, 1.218-1.646; P < 0.001) but not with EMD. Individually, the common risk variants ARMS2 rs10490924 (P = 0.042), C3 rs2230199 (P = 0.042), and CETP rs5817082 (P = 0.042) were associated with EMD, after adjustment for AMD, sex, and age.

Conclusions

We found a strong association between EMD and AMD, suggesting a common pathogenesis. The GRS for AMD was not associated with EMD, but a partially overlapping genetic basis was suggested when assessing individual risk variants. We propose that EMD per se do not represent an increase in the global genetic risk for AMD.

Glycative stress as a cause of macular degeneration

People are living longer and rates of age-related diseases such as age-related macular degeneration (AMD) are accelerating, placing enormous burdens on patients and health care systems. The quality of carbohydrate foods consumed by an individual impacts health. The glycemic index (GI) is a kinetic measure of the rate at which glucose arrives in the blood stream after consuming various carbohydrates. Consuming diets that favor slowly digested carbohydrates releases sugar into the bloodstream gradually after consuming a meal (low glycemic index). This is associated with reduced risk for major age-related diseases including AMD, cardiovascular disease, and diabetes. In comparison, consuming the same amounts of different carbohydrates in higher GI diets, releases glucose into the blood rapidly, causing glycative stress as well as accumulation of advanced glycation end products (AGEs). Such AGEs are cytotoxic by virtue of their forming abnormal proteins and protein aggregates, as well as inhibiting proteolytic and other protective pathways that might otherwise selectively recognize and remove toxic species. Using in vitro and animal models of glycative stress, we observed that consuming higher GI diets perturbs metabolism and the microbiome, resulting in a shift to more lipid-rich metabolomic profiles. Interactions between aging, diet, eye phenotypes and physiology were observed. A large body of laboratory animal and human clinical epidemiologic data indicates that consuming lower GI diets, or lower glycemia diets, is protective against features of early AMD (AMDf) in mice and AMD prevalence or AMD progression in humans. Drugs may be optimized to diminish the ravages of higher glycemic diets. Human trials are indicated to determine if AMD progression can be retarded using lower GI diets. Here we summarized the current knowledge regarding the pathological role of glycative stress in retinal dysfunction and how dietary strategies might diminish retinal disease.

Mitochondrial damage and clearance in retinal pigment epithelial cells

Age-related macular degeneration (AMD) is a devastating eye disease that causes permanent vision loss in the central part of the retina, known as the macula. Patients with such severe visual loss face a reduced quality of life and are at a 1.5 times greater risk of death compared to the general population. Currently, there is no cure for or effective treatment for dry AMD. There are several mechanisms thought to underlie the disease, for example, ageing-associated chronic oxidative stress, mitochondrial damage, harmful protein aggregation and inflammation. As a way of gaining a better understanding of the molecular mechanisms behind AMD and thus developing new therapies, we have created a peroxisome proliferator-activated receptor gamma coactivator 1-alpha and nuclear factor erythroid 2-related factor 2 (PGC1α/NFE2L2) double-knockout (dKO) mouse model that mimics many of the clinical features of dry AMD, including elevated levels of oxidative stress markers, damaged mitochondria, accumulating lysosomal lipofuscin and extracellular drusen-like structures in retinal pigment epithelial cells (RPE). In addition, a human RPE cell-based model was established to examine the impact of non-functional intracellular clearance systems on inflammasome activation. In this study, we found that there was a disturbance in the autolysosomal machinery responsible for clearing mitochondria in the RPE cells of one-year-old PGC1α/NFE2L2-deficient mice. The confocal immunohistochemical analysis revealed an increase in autophagosome marker microtubule-associated proteins 1A/1B light chain 3B (LC3B) as well as multiple mitophagy markers such as PTE-induced putative kinase 1 (PINK1) and E3 ubiquitin ligase (PARKIN), along with signs of damaged mitochondria. However, no increase in autolysosome formation was detected, nor was there a colocalization of the lysosomal marker LAMP2 or the mitochondrial marker, ATP synthase β. There was an upregulation of late autolysosomal fusion Ras-related protein (Rab7) in the perinuclear space of RPE cells, together with autofluorescent aggregates. Additionally, we observed an increase in the numbers of Toll-like receptors 3 and 9, while those of NOD-like receptor 3 were decreased in PGC1α/NFE2L2 dKO retinal specimens compared to wild-type animals. There was a trend towards increased complement component C5a and increased involvement of the serine protease enzyme, thrombin, in enhancing the terminal pathway producing C5a, independent of C3. The levels of primary acute phase C-reactive protein and receptor for advanced glycation end products were also increased in the PGC1α/NFE2L2 dKO retina. Furthermore, selective proteasome inhibition with epoxomicin promoted both nicotinamide adenine dinucleotide phosphate (NADPH) oxidase and mitochondrial-mediated oxidative stress, leading to the release of mitochondrial DNA to the cytosol, resulting in potassium efflux-dependent activation of the absent in melanoma 2 (AIM2) inflammasome and the subsequent secretion of interleukin-1β in ARPE-19 cells. In conclusion, the data suggest that there is at least a relative decrease in mitophagy, increases in the amounts of C5 and thrombin and decreased C3 levels in this dry AMD-like model. Moreover, selective proteasome inhibition evoked mitochondrial damage and AIM2 inflammasome activation in ARPE-19 cells.

Propensity-Matched Analysis of the Risk of Age-Related Macular Degeneration with Systemic Immune-Mediated Inflammatory Disease

PURPOSE

The pathogenesis of age-related macular degeneration (AMD) involves aberrant complement activation and is a leading cause of vision loss worldwide. Complement aberrations are also implicated in many systemic immune-mediated inflammatory diseases (IMIDs), but the relationship between AMD and these conditions remains undescribed. The aim of this study is to first assess the association between AMD and IMIDs, and then assess the risk of AMD in patients with specific IMIDs associated with AMD.

DESIGN

Cross-sectional study and cohort study.

SUBJECTS AND CONTROLS

Patients with AMD were compared with control patients with cataracts and no AMD to ensure evaluation by an ophthalmologist. Patients with IMIDs were compared with patients without IMIDs but with cataracts.

METHODS

This study used deidentified data from a national database (2006-2023), using International Classification of Diseases 10 codes to select for IMIDs. Propensity score matching was based on patients on age, sex, race, ethnicity, and smoking. Odds ratios were generated for IMIDs and compared between AMD and control patients. For IMIDs associated with AMD, the risk of AMD in patients with the IMID versus patients without IMIDs was determined utilizing a cohort study design.

MAIN OUTCOME MEASURES

Odds ratio of IMID, risk ratios (RRs), and 95% confidence intervals (CIs) of AMD diagnosis, given an IMID.

RESULTS

After propensity score matching, AMD and control cohorts (n = 217 197 each) had a mean ± standard deviation age of 74.7 ± 10.4 years, were 56% female, and 9% of patients smoked. Age-related macular degeneration showed associations with systemic lupus erythematosus (SLE), Crohn's disease, ulcerative colitis, rheumatoid arthritis (RA), psoriasis, sarcoidosis, scleroderma, giant cell arteritis, and vasculitis. Cohorts for each positively associated IMID were created and matched to control cohorts with no IMID history. Patients with RA (RR, 1.40; 95% CI, 1.30-1.49), SLE (RR, 1.73; 95% CI, 1.37-2.18), Crohn's disease (RR, 1.42; 95% CI, 1.20-1.71), ulcerative colitis (RR, 1.45; 95% CI, 1.29-1.63), psoriasis (RR, 1.48; 95% CI, 1.37-1.60), vasculitis (RR, 1.48; 95% CI, 1.33-1.64), scleroderma (RR, 1.65; 95% CI, 1.35-2.02), and sarcoidosis (RR, 1.42; 95% CI, 1.24-1.62) showed a higher risk of developing AMD compared with controls.

CONCLUSIONS

The results suggest that there is an increased risk of developing AMD in patients with RA, SLE, Crohn's disease, ulcerative colitis, psoriasis, vasculitis, scleroderma, and sarcoidosis compared with patients with no IMIDs.

FINANCIAL DISCLOSURE(S)

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

Predictive Performance of an Updated Polygenic Risk Score for Age-Related Macular Degeneration

PURPOSE

A recent genome-wide association study of age-related macular degeneration (AMD) identified new AMD-associated risk variants. These variants now can be incorporated into an updated polygenic risk score (PRS). This study aimed to assess the performance of an updated PRS, PRS2023, in an independent cohort of older individuals with retinal imaging data and to compare performance with an older PRS, PRS2016.

DESIGN

Cross-sectional study.

PARTICIPANTS

A total of 4175 participants of European ancestry, 70 years of age or older, with genotype and retinal imaging data.

METHODS

We used logistic regression models and area under the receiver operating characteristic curve (AUC) to assess the performance of PRS2023 compared with PRS2016. AMD status and severity were graded using color fundus photography.

MAIN OUTCOME MEASURES

Association of PRS2023 and PRS2016 with AMD risk at baseline.

RESULTS

At enrollment among 4175 participants, 2605 participants (62.4%) had no AMD and 853 participants (20.4%), 671 participants (16.1%), and 46 participants (1.1%) had early, intermediate, and late-stage AMD, respectively. More than 27% of the participants with a high PRS2023 (top quartile) had intermediate or late-stage AMD, compared with < 15% for those in the middle 2 quartiles and less than 13% for those in the lowest quartile. Both PRS2023 and PRS2016 were associated significantly with AMD after adjustment for age, sex, smoking status, and lipid levels, with increasing odds ratios (ORs) for worsening AMD grades. PRS2023 outperformed PRS2016 (P = 0.03 for all AMD and P = 0.03 for late AMD, DeLong test comparing AUC). PRS2023 was associated with late-stage AMD with an adjusted OR of 5.05 (95% confidence interval [CI], 3.41-7.47) per standard deviation. The AUC of a model containing conventional or nongenetic risk factors and PRS2023 was 91% (95% CI, 87%-95%) for predicting late-stage AMD, which improved 12% over the model without the PRS (AUC, 79%; P < 0.001 for difference).

CONCLUSIONS

A new PRS, PRS2023, for AMD outperforms a previous PRS and predicts increasing risk for late-stage AMD (with stronger association for more severe imaging-confirmed AMD grades). Our findings have clinical implications for the improved prediction and risk stratification of AMD.

FINANCIAL DISCLOSURE(S)

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

CRISPR Manipulation of Age-Related Macular Degeneration Haplotypes in the Complement System: Potential Future Therapeutic Applications/Avenues

Age-related macular degeneration (AMD) is the leading cause of irreversible vision loss among the elderly in the developed world. Whilst AMD is a multifactorial disease, the involvement of the complement system in its pathology is well documented, with single-nucleotide polymorphisms (SNPs) in different complement genes representing an increased risk factor. With several complement inhibitors explored in clinical trials showing limited success, patients with AMD are still without a reliable treatment option. This indicates that there is still a gap of knowledge in the functional implications and manipulation of the complement system in AMD, hindering the progress towards translational treatments. Since the discovery of the CRISPR/Cas system and its development into a powerful genome engineering tool, the field of molecular biology has been revolutionised. Genetic variants in the complement system have long been associated with an increased risk of AMD, and a variety of haplotypes have been identified to be predisposing/protective, with variation in complement genes believed to be the trigger for dysregulation of the cascade leading to inflammation. AMD-haplotypes (SNPs) alter specific aspects of the activation and regulation of the complement cascade, providing valuable insights into the pathogenic mechanisms of AMD with important diagnostic and therapeutic implications. The effect of targeting these AMD-related SNPs on the regulation of the complement cascade has been poorly explored, and the CRISPR/Cas system provides an ideal tool with which to explore this avenue. Current research concentrates on the association events of specific AMD-related SNPs in complement genes without looking into the effect of targeting these SNPs and therefore influencing the complement system in AMD pathogenesis. This review will explore the current understanding of manipulating the complement system in AMD pathogenesis utilising the genomic manipulation powers of the CRISPR/Cas systems. A number of AMD-related SNPs in different complement factor genes will be explored, with a particular emphasis on factor H (CFH), factor B (CFB), and complement C3 (C3).

Adverse COVID-19 outcomes in American Veterans with age-related macular degeneration: a case-control study

OBJECTIVES

Prior studies suggest that patients with age-related macular degeneration (AMD) have poorer COVID-19 outcomes. This study aims to evaluate whether AMD is associated with adverse COVID-19 outcomes in a large clinical database.

DESIGN

Case-control study.

SETTING

We obtained demographic and clinical data from a national US Veterans Affairs (VA) database for all Veterans aged 50 years or older with positive COVID-19 testing prior to 2 May 2021.

PRIMARY AND SECONDARY OUTCOME MEASURES

The primary outcome measure was hospitalisation. Secondary outcome measures were intensive care unit admission, mechanical ventilation and death. Potential associations between AMD and outcome measures occurring within 60 days of COVID-19 diagnosis were evaluated using multiple logistic regression analyses.

RESULTS

Of the 171 325 patients in the study cohort, 7913 (5%) had AMD and 2152 (1%) had severe AMD, defined as advanced atrophic or exudative AMD disease coding. Multiple logistic regression adjusting for age, Charlson Comorbidity Index, sex, race, ethnicity and COVID-19 timing showed that an AMD diagnosis did not significantly increase the odds of hospitalisation (p=0.11). Using a Bonferroni-adjusted significance level of 0.006, AMD and severe AMD also were not significant predictors for the secondary outcomes, except for AMD being modestly protective for death (p=0.002).

CONCLUSIONS

After adjusting for other variables, neither AMD nor severe AMD was a risk factor for adverse COVID-19 outcomes in the VA healthcare system. These findings indicate that an AMD diagnosis alone should not alter recommended ophthalmic management based on COVID-19 adverse outcome risk.

Oral Metformin Inhibits Choroidal Neovascularization by Modulating the Gut-Retina Axis

Purpose

Emerging data indicate that metformin may prevent the development of age-related macular degeneration (AMD). Whereas the underlying mechanisms of metformin's anti-aging properties remain undetermined, one proposed avenue is the gut microbiome. Using the laser-induced choroidal neovascularization (CNV) model, we investigate the effects of oral metformin on CNV, retinal pigment epithelium (RPE)/choroid transcriptome, and gut microbiota.

Methods

Specific pathogen free (SPF) male mice were treated via daily oral gavage of metformin 300 mg/kg or vehicle. Male mice were selected to minimize sex-specific differences to laser induction and response to metformin. Laser-induced CNV size and macrophage/microglial infiltration were assessed by isolectin and Iba1 immunostaining. High-throughput RNA-seq of the RPE/choroid was performed using Illumina. Fecal pellets were analyzed for gut microbiota composition/pathways with 16S rRNA sequencing/shotgun metagenomics, as well as microbial-derived metabolites, including small-chain fatty acids and bile acids. Investigation was repeated in metformin-treated germ-free (GF) mice and antibiotic-treated/GF mice receiving fecal microbiota transplantation (FMT) from metformin-treated SPF mice.

Results

Metformin treatment reduced CNV size (P < 0.01) and decreased Iba1+ macrophage/microglial infiltration (P < 0.005). One hundred forty-five differentially expressed genes were identified in the metformin-treated group (P < 0.05) with a downregulation in pro-angiogenic genes Tie1, Pgf, and Gata2. Furthermore, metformin altered the gut microbiome in favor of Bifidobacterium and Akkermansia, with a significant increase in fecal levels of butyrate, succinate, and cholic acid. Metformin did not suppress CNV in GF mice but colonization of microbiome-depleted mice with metformin-derived FMT suppressed CNV.

Conclusions

These data suggest that oral metformin suppresses CNV, the hallmark lesion of advanced neovascular AMD, via gut microbiome modulation.

Treating patients with geographic atrophy: are we there yet?

Geographic atrophy (GA) is a progressive degenerative disease that significantly contributes to visual impairment in individuals aged 50 years and older. The development of GA is influenced by various modifiable and non-modifiable risk factors, including age, smoking, and specific genetic variants, particularly those related to the complement system regulators. Given the multifactorial and complex nature of GA, several treatment approaches have been explored, such as complement inhibition, gene therapy, and cell therapy. The recent approval by the Food and Drug Administration of pegcetacoplan, a complement C3 inhibitor, marks a significant breakthrough as the first approved treatment for GA. Furthermore, numerous interventions are currently in phase II or III trials, alongside this groundbreaking development. In light of these advancements, this review provides a comprehensive overview of GA, encompassing risk factors, prevalence, genetic associations, and imaging characteristics. Additionally, it delves into the current landscape of GA treatment, emphasizing the latest progress and future considerations. The goal of starting this discussion is to ultimately identify the most suitable candidates for each therapy, highlight the importance of tailoring treatments to individual cases, and continue monitoring the long-term implications of these emerging interventions.

Integrated multi-omics single cell atlas of the human retina

Single-cell sequencing has revolutionized the scale and resolution of molecular profiling of tissues and organs. Here, we present an integrated multimodal reference atlas of the most accessible portion of the mammalian central nervous system, the retina. We compiled around 2.4 million cells from 55 donors, including 1.4 million unpublished data points, to create a comprehensive human retina cell atlas (HRCA) of transcriptome and chromatin accessibility, unveiling over 110 types. Engaging the retina community, we annotated each cluster, refined the Cell Ontology for the retina, identified distinct marker genes, and characterized cis-regulatory elements and gene regulatory networks (GRNs) for these cell types. Our analysis uncovered intriguing differences in transcriptome, chromatin, and GRNs across cell types. In addition, we modeled changes in gene expression and chromatin openness across gender and age. This integrated atlas also enabled the fine-mapping of GWAS and eQTL variants. Accessible through interactive browsers, this multimodal cross-donor and cross-lab HRCA, can facilitate a better understanding of retinal function and pathology.

Exploring the contribution of ARMS2 and HTRA1 genetic risk factors in age-related macular degeneration

Age-related macular degeneration (AMD) is the leading cause of severe irreversible central vision loss in individuals over 65 years old. Genome-wide association studies (GWASs) have shown that the region at chromosome 10q26, where the age-related maculopathy susceptibility (ARMS2/LOC387715) and HtrA serine peptidase 1 (HTRA1) genes are located, represents one of the strongest associated loci for AMD. However, the underlying biological mechanism of this genetic association has remained elusive. In this article, we extensively review the literature by us and others regarding the ARMS2/HTRA1 risk alleles and their functional significance. We also review the literature regarding the presumed function of the ARMS2 protein and the molecular processes of the HTRA1 protein in AMD pathogenesis in vitro and in vivo, including those of transgenic mice overexpressing HtrA1/HTRA1 which developed Bruch's membrane (BM) damage, choroidal neovascularization (CNV), and polypoidal choroidal vasculopathy (PCV), similar to human AMD patients. The elucidation of the molecular mechanisms of the ARMS2 and HTRA1 susceptibility loci has begun to untangle the complex biological pathways underlying AMD pathophysiology, pointing to new testable paradigms for treatment.

Whole Genome Sequencing Identifies Novel Common and Low-Frequency Variants Associated With Age-Related Macular Degeneration

Purpose

To identify associations of common, low-frequency, and rare variants with advanced age-related macular degeneration (AMD) using whole genome sequencing (WGS).

Methods

WGS data were obtained for 2123 advanced AMD patients (participants of clinical trials for advanced AMD) and 2704 controls (participants of clinical trials for asthma [N = 2518] and Alzheimer's disease [N = 186]), and joint genotype calling was performed, followed by quality control of the dataset. Single variant association analyses were performed for all identified common, low-frequency, and rare variants. Gene-based tests were executed for rare and low-frequency variants using SKAT-O and three groups of variants based on putative impact information: (1) all variants, (2) modifier impact variants, and (3) high- and moderate-impact variants. To ascertain independence of the identified associations from previously reported AMD and asthma loci, conditional analyses were performed.

Results

Previously identified AMD variants at the CFH, ARMS2/HTRA1, APOE, and C3 loci were associated with AMD at a genome-wide significance level. We identified new single variant associations for common variants near the PARK7 gene and in the long non-coding RNA AC103876.1, and for a rare variant near the TENM3 gene. In addition, gene-based association analyses identified a burden of modifier variants in eight intergenic and gene-spanning regions and of high- and moderate-impact variants in the C3, CFHR5, SLC16A8, and CFI genes.

Conclusions

We describe the largest WGS study in AMD to date. We confirmed previously identified associations and identified several novel associations that are worth exploring in further follow-up studies.

10q26 - The enigma in age-related macular degeneration

Despite comprehensive research efforts over the last decades, the pathomechanisms of age-related macular degeneration (AMD) remain far from being understood. Large-scale genome wide association studies (GWAS) were able to provide a defined set of genetic aberrations which contribute to disease risk, with the strongest contributors mapping to distinct regions on chromosome 1 and 10. While the chromosome 1 locus comprises factors of the complement system with well-known functions, the role of the 10q26-locus in AMD-pathophysiology remains enigmatic. 10q26 harbors a cluster of three functional genes, namely PLEKHA1, ARMS2 and HTRA1, with most of the AMD-associated genetic variants mapping to the latter two genes. High linkage disequilibrium between ARMS2 and HTRA1 has kept association studies from reliably defining the risk-causing gene for long and only very recently the genetic risk region has been narrowed to ARMS2, suggesting that this is the true AMD gene at this locus. However, genetic associations alone do not suffice to prove causality and one or more of the 14 SNPs on this haplotype may be involved in long-range control of gene expression, leaving HTRA1 and PLEKHA1 still suspects in the pathogenic pathway. Both, ARMS2 and HTRA1 have been linked to extracellular matrix homeostasis, yet their exact molecular function as well as their role in AMD pathogenesis remains to be uncovered. The transcriptional regulation of the 10q26 locus adds an additional level of complexity, given, that gene-regulatory as well as epigenetic alterations may influence expression levels from 10q26 in diseased individuals. Here, we provide a comprehensive overview on the 10q26 locus and its three gene products on various levels of biological complexity and discuss current and future research strategies to shed light on one of the remaining enigmatic spots in the AMD landscape.

Interaction between genetics and the adherence to the Mediterranean diet: the risk for age-related macular degeneration. Coimbra Eye Study Report 8

BACKGROUND

Age-related macular degeneration (AMD) is a multifactorial degenerative disease of the macula. Different factors, environmental, genetic and lifestyle, contribute to its onset and progression. However, how they interconnect to promote the disease, or its progression, is still unclear. With this work, we aim to assess the interaction of the genetic risk for AMD and the adherence to the Mediterranean diet in the Coimbra Eye Study.

METHODS

Enrolled subjects (n = 612) underwent ophthalmological exams and answered a food questionnaire. Adherence to the Mediterranean diet was assessed with mediSCORE. An overall value was calculated for each participant, ranging from 0 to 9, using the sum of 9 food groups, and a cut off value of ≥ 6 was considered high adherence. Rotterdam Classification was used for grading. Participants' genotyping was performed in collaboration with The European Eye Epidemiology Consortium. The genetic risk score (GRS) was calculated for each participant considering the number of alleles at each variant and their effect size. Interaction was assessed with additive and multiplicative models, adjusted for age, sex, physical exercise, and smoking.

RESULTS

The AMD risk was reduced by 60% in subjects with high adherence to the Mediterranean diet compared to subjects with low adherence to the Mediterranean diet. Combined effects of having low adherence to the Mediterranean diet and high GRS led to almost a 5-fold increase in the risk for AMD, compared to low GRS and high adherence to the Mediterranean diet. The multiplicative scale suggested a multiplicative interaction, although not statistically significant [odds ratio (OR) = 1.111, 95% CI 0.346-3.569, P = 0.859]. The additive model showed a causal positive effect of the interaction of GRS and adherence to the Mediterranean diet: relative excess risk due to interaction (RERI) = 150.9%, (95% CI: - 0.414 to 3.432, P = 0.062), attributable proportion due to interaction (AP) = 0.326 (95% CI: - 0.074 to 0.726, P = 0.055) and synergy index (SI) = 1.713 (95% CI: 0.098-3.329, P = 0.019). High GRS people benefited from adhering to the Mediterranean diet with a 60% risk reduction. For low-GRS subjects, a risk reduction was also seen, but not significantly.

CONCLUSIONS

Genetics and Mediterranean diet interact to protect against AMD, proving there is an interplay between genetics and environmental factors.

TRIAL REGISTRATION

The AMD Incidence (NCT02748824) and Lifestyle and Food Habits Questionnaire in the Portuguese Population Aged 55 or More (NCT01715870) studies are registered at www.

CLINICALTRIALS

gov . Five-year Incidence of Age-related Macular Degeneration in the Central Region of Portugal (AMD IncidencePT); NCT02748824: date of registration: 22/04/16. Lifestyle and Food Habits Questionnaire in the Portuguese Population Aged 55 or More; NCT01715870: date of registration: 29/10/12.

Electrochemical nano-biosensor based on electrospun indium zinc oxide nanofibers for the determination of complement component 3 protein

Age-related macular degeneration (AMD) is a progressive chronic neurodegenerative retinal disease leading to vision loss, irreversible blindness, and visual impairment in older adults worldwide. Complement component 3 (C3) protein has been identified as the most predominant biomarker towards early diagnosis of AMD; therefore, there is an utmost requirement for non-invasive detection of C3 protein in the tear fluids of AMD patients. Considering this, we report an insightful electrochemical sensor capable of detecting clinically relevant concentrations ranging from 10 fg/mL to 1 μg/mL using electrospun indium-doped zinc oxide (InZnO) nanofibers as the transducing layer. The InZnO nanofibers have facilitated high anti-C3 antibody loading of 3.42 × 10^-9 mol/cm² and enhanced the overall charge transport mechanism at the sensor interface. The biofunctionalization process of the biosensor was investigated thoroughly using X-ray photoelectron spectroscopy (XPS) as well as different electrochemical techniques. The target C3 proteins were captured on the fabricated biosensor surface and determined through changes in charge transfer resistance (R_CT) while executing electrochemical impedance spectroscopy (EIS) and peak current (I_p) in the case of cyclic voltammetry (CV) and differential pulse voltammetry (DPV), respectively. The InZnO nanofiber-based nano-biosensor demonstrated a very low limit of detections (LODs) of 5.214 fg/mL and 0.241 fg/mL with an excellent sensitivity of 4.6709 (ΔR/R) (g/mL)^-1 cm^-2 and 54.4939 (ΔI_p/I_p)% (g/mL)^-1 cm^-2 for EIS and DPV techniques, respectively. By virtue of high antibody loading, ultrasensitive and ultra-selective capability, the indium-doped ZnO nanofibers show huge potential to be used as a high-performance diagnostic platform for AMD diagnosis.

Antioxidative Role of Heterophagy, Autophagy, and Mitophagy in the Retina and Their Association with the Age-Related Macular Degeneration (AMD) Etiopathogenesis

Age-related macular degeneration (AMD), an oxidative stress-linked neurodegenerative disease, leads to irreversible damage of the central retina and severe visual impairment. Advanced age and the long-standing influence of oxidative stress and oxidative cellular damage play crucial roles in AMD etiopathogenesis. Many authors emphasize the role of heterophagy, autophagy, and mitophagy in maintaining homeostasis in the retina. Relevantly modifying the activity of both macroautophagy and mitophagy pathways represents one of the new therapeutic strategies in AMD. Our review provides an overview of the antioxidative roles of heterophagy, autophagy, and mitophagy and presents associations between dysregulations of these molecular mechanisms and AMD etiopathogenesis. The authors performed an extensive analysis of the literature, employing PubMed and Google Scholar, complying with the 2013-2023 period, and using the following keywords: age-related macular degeneration, RPE cells, reactive oxygen species, oxidative stress, heterophagy, autophagy, and mitophagy. Heterophagy, autophagy, and mitophagy play antioxidative roles in the retina; however, they become sluggish and dysregulated with age and contribute to AMD development and progression. In the retina, antioxidative roles also play in RPE cells, NFE2L2 and PGC-1α proteins, NFE2L2/PGC-1α/ARE signaling cascade, Nrf2 factor, p62/SQSTM1/Keap1-Nrf2/ARE pathway, circulating miRNAs, and Yttrium oxide nanoparticles performed experimentally in animal studies.

Heme Interactions as Regulators of the Alternative Pathway Complement Responses and Implications for Heme-Associated Pathologies

Heme (Fe²⁺-protoporphyrin IX) is a pigment of life, and as a prosthetic group in several hemoproteins, it contributes to diverse critical cellular processes. While its intracellular levels are tightly regulated by networks of heme-binding proteins (HeBPs), labile heme can be hazardous through oxidative processes. In blood plasma, heme is scavenged by hemopexin (HPX), albumin and several other proteins, while it also interacts directly with complement components C1q, C3 and factor I. These direct interactions block the classical pathway (CP) and distort the alternative pathway (AP). Errors or flaws in heme metabolism, causing uncontrolled intracellular oxidative stress, can lead to several severe hematological disorders. Direct interactions of extracellular heme with alternative pathway complement components (APCCs) may be implicated molecularly in diverse conditions at sites of abnormal cell damage and vascular injury. In such disorders, a deregulated AP could be associated with the heme-mediated disruption of the physiological heparan sulphate-CFH coat of stressed cells and the induction of local hemostatic responses. Within this conceptual frame, a computational evaluation of HBMs (heme-binding motifs) aimed to determine how heme interacts with APCCs and whether these interactions are affected by genetic variation within putative HBMs. Combined computational analysis and database mining identified putative HBMs in all of the 16 APCCs examined, with 10 exhibiting disease-associated genetic (SNPs) and/or epigenetic variation (PTMs). Overall, this article indicates that among the pleiotropic roles of heme reviewed, the interactions of heme with APCCs could induce differential AP-mediated hemostasis-driven pathologies in certain individuals.

Systemic Metabolomics in a Framework of Genetics and Lifestyle in Age-Related Macular Degeneration

Insights into the pathogenesis of age-related macular degeneration (AMD), a leading cause of blindness, point towards a complex interplay of genetic and lifestyle factors triggering various systemic pathways. This study aimed to characterize metabolomic profiles for AMD and to evaluate their position in the trias with genetics and lifestyle. This study included 5923 individuals from five European studies. Blood metabolomics were assessed using a nuclear magnetic resonance platform of 146 metabolites. Associations were studied using regression analyses. A genetic risk score (GRS) was calculated using β-values of 49 AMD variants, a lifestyle risk score (LRS) using smoking and diet data, and a metabolite risk score (MRS) using metabolite values. We identified 61 metabolites associated with early-intermediate AMD, of which 94% were lipid-related, with higher levels of HDL-subparticles and apolipoprotein-A1, and lower levels of VLDL-subparticles, triglycerides, and fatty acids (false discovery rate (FDR) p-value < 1.4 × 10^-2). Late AMD was associated with lower levels of the amino acids histidine, leucine, valine, tyrosine, and phenylalanine, and higher levels of the ketone bodies acetoacetate and 3-hydroxybutyrate (FDR p-value < 1.5 × 10^-3). A favorable lifestyle characterized by a healthy diet was associated with higher levels of amino acids and lower levels of ketone bodies, while an unfavorable lifestyle, including smoking, showed opposite effects (FDR p-value < 2.7 × 10^-2). The MRS mediated 5% of the effect of the GRS and 20% of that of the LRS on late AMD. Our findings show that metabolomic profiles differ between AMD stages and show that blood metabolites mostly reflect lifestyle. The severity-specific profiles spur further interest into the systemic effects related to disease conversion.

Role of Complement in the Onset of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is a progressive degenerative disease of the central retina and the leading cause of severe loss of central vision in people over age 50. Patients gradually lose central visual acuity, compromising their ability to read, write, drive, and recognize faces, all of which greatly impact daily life activities. Quality of life is significantly affected in these patients, and there are worse levels of depression as a result. AMD is a complex, multifactorial disease in which age and genetics, as well as environmental factors, all play a role in its development and progression. The mechanism by which these risk factors interact and converge towards AMD are not fully understood, and therefore, drug discovery is challenging, with no successful therapeutic attempt to prevent the development of this disease. In this review, we describe the pathophysiology of AMD and review the role of complement, which is a major risk factor in the development of AMD.

Future prospects for human genetics and genomics in drug discovery

Evidence from human genetics supporting the therapeutic hypothesis increases the likelihood that a drug will succeed in clinical trials. Rare and common disease genetics yield a wide array of alleles with a range of effect sizes that can proxy for the effect of a drug in disease. Recent advances in large scale population collections and whole genome sequencing approaches have provided a rich resource of human genetic evidence to support drug target selection. As the range of phenotypes profiled increases and ever more alleles are discovered across world-wide populations, these approaches will increasingly influence multiple stages across the lifespan of a drug discovery programme.

Common and rare genetic risk variants in age-related macular degeneration and genetic risk score in the Coimbra eye study

PURPOSE

To determine the contribution of common and rare genetic variants in age-related macular degeneration (AMD) in a Portuguese population from the Coimbra Eye Study (CES), and the genetic risk score (GRS).

METHODS

Participants underwent ophthalmologic examination and imaging. A centralized reading centre performed AMD staging. Genetic sequencing was carried out with the EYE-RISK assay. Sixty-nine single nucleotide polymorphisms (SNPs) were genotyped and tested for association with AMD. Case-control and progression-to-AMD analyses were performed using logistic regression to assess allelic odds ratio (OR) at a 95% confidence interval (CI) for each variant. GRS was calculated for cases/controls and progressors/non-progressors. Cumulative impact of rare variants was compared between cases/controls using logistic regression.

RESULTS

In case-control analysis (237 cases/640 controls) variants associated with risk of disease were: ARMS2 rs10490924, ARMS2_HTRA1 rs3750846, CFH rs35292876, SLC16A8 rs8135665, TGFBR1 rs1626340. Major risk variants ARMS2/HTRA1 rs3750846, CFH rs570618 and C3 rs2230199 had unexpected lower allele frequency (AF), and the highest risk-conferring variant was a rare variant, CFH rs35292876 (OR, 2.668; p-value = 0.021). In progression-to-AMD analysis (137 progressors/630 non-progressors), variants associated with risk of progression were ARMS2 rs10490924, ARMS2_HTRA1 rs3750846, CFH rs35292876. GRS of cases/controls was 1.124 ± 1.187 and 0.645 ± 1.124 (p-value < 0.001), and of progressors/non-progressors was 1.190 ± 1.178 and 0.669 ± 1.141 (p-value < 0.001). Higher proportion of pathogenic rare CFH variants was observed in cases (OR, 9.661; p-value < 0.001).

CONCLUSIONS

Both common and rare variants were associated with AMD, but a CFH rare variant conferred the highest risk of disease while three major risk variants had a lower-than-expected AF in our population originary from a geographic region with lower prevalence of AMD. GRS was still significantly higher in AMD patients. Damaging CFH rare variants were cumulatively more common in AMD cases.

Lifestyle Intervention Randomized Controlled Trial for Age-Related Macular Degeneration (AMD-Life): Study Design

Age-related macular degeneration (AMD) has a strong genetic basis, but environmental factors such as smoking and a healthy diet can decrease the genetic fate by up to 50%. Current guidelines for clinical management include recommendations for a healthy lifestyle and antioxidant supplementation. However, many ophthalmologists do not inform their patients of this AMD-beneficial lifestyle. An important reason is the lack of trust that transition of lifestyle will be feasible in persons of advanced age and lack of methodology to measure lifestyle or its biological effects. To address these issues, we set up the lifestyle intervention study AMD-Life. It aims to investigate whether personalized risk-profiling (including genetic testing) and/or additional coaching can motivate patients to change their lifestyle. It also explores which biomarkers best reflect lifestyle change beneficial for AMD. The first year is a three-arm, self-contained open-label randomized clinical trial. A total of 150 AMD patients aged 55-85 years were randomized into three arms: (A) merely standard recommendations; (B) A conditions plus personalized risk profiling based on genetics and lifestyle, (C) B conditions plus coaching. The second year tests sustainability of lifestyle changes without active intervention. AMD-Life can provide further insight into the relevance of these interventions for the clinical management of AMD.

Gene targeting as a therapeutic avenue in diseases mediated by the complement alternative pathway

The complement alternative pathway (AP) is implicated in numerous diseases affecting many organs, ranging from the rare hematological disease paroxysmal nocturnal hemoglobinuria (PNH), to the common blinding disease age-related macular degeneration (AMD). Critically, the AP amplifies any activating trigger driving a downstream inflammatory response; thus, components of the pathway have become targets for drugs of varying modality. Recent validation from clinical trials using drug modalities such as inhibitory antibodies has paved the path for gene targeting of the AP or downstream effectors. Gene targeting in the complement field currently focuses on supplementation or suppression of complement regulators in AMD and PNH, largely because the eye and liver are highly amenable to drug delivery through local (eye) or systemic (liver) routes. Targeting the liver could facilitate treatment of numerous diseases as this organ generates most of the systemic complement pool. This review explains key concepts of RNA and DNA targeting and discusses assets in clinical development for the treatment of diseases driven by the alternative pathway, including the RNA-targeting therapeutics ALN-CC5, ARO-C3, and IONIS-FB-LRX, and the gene therapies GT005 and HMR59. These therapies are but the spearhead of potential drug candidates that might revolutionize the field in coming years.

Age-related macular degeneration: A disease of extracellular complement amplification

Age-related macular degeneration (AMD) is a major cause of vision impairment in the Western World, and with the aging world population, its incidence is increasing. As of today, for the majority of patients, no treatment exists. Multiple genetic and biochemical studies have shown a strong association with components in the complement system and AMD, and evidence suggests a major role of remodeling of the extracellular matrix underlying the outer blood/retinal barrier. As part of the innate immune system, the complement cascade acts as a first-line defense against pathogens, and upon activation, its amplification loop ensures a strong, rapid, and sustained response. Excessive activation, however, can lead to host tissue damage and cause complement-associated diseases like AMD. AMD patients present with aberrant activation of the alternative pathway, especially in ocular tissues but also on a systemic level. Here, we review the latest findings of complement activation in AMD, and we will discuss in vivo observations made in human tissue, cellular models, the potential synergy of different AMD-associated pathways, and conclude on current clinical trials and the future outlook.

A novel method for real-time analysis of the complement C3b:FH:FI complex reveals dominant negative CFI variants in age-related macular degeneration

Age-related macular degeneration (AMD) is linked to 2 main disparate genetic pathways: a chromosome 10 risk locus and the alternative pathway (AP) of complement. Rare genetic variants in complement factor H (CFH; FH) and factor I (CFI; FI) are associated with AMD. FH acts as a soluble cofactor to facilitate FI's cleavage and inactivation of the central molecule of the AP, C3b. For personalised treatment, sensitive assays are required to define the functional significance of individual AP genetic variants. Generation of recombinant FI for functional analysis has thus far been constrained by incomplete processing resulting in a preparation of active and inactive protein. Using an internal ribosomal entry site (IRES)-Furin-CFI expression vector, fully processed FI was generated with activity equivalent to serum purified FI. By generating FI with an inactivated serine protease domain (S525A FI), a real-time surface plasmon resonance assay of C3b:FH:FI complex formation for characterising variants in CFH and CFI was developed and correlated well with standard assays. Using these methods, we further demonstrate that patient-associated rare genetic variants lacking enzymatic activity (e.g. CFI I340T) may competitively inhibit the wild-type FI protein. The dominant negative effect identified in inactive factor I variants could impact on the pharmacological replacement of FI currently being investigated for the treatment of dry AMD.

Genome-Wide Pleiotropy Study Identifies Association of PDGFB with Age-Related Macular Degeneration and COVID-19 Infection Outcomes

Age-related macular degeneration (AMD) has been implicated as a risk factor for severe consequences from COVID-19. We evaluated the genetic architecture shared between AMD and COVID-19 (critical illness, hospitalization, and infections) using analyses of genetic correlations and pleiotropy (i.e., cross-phenotype meta-analysis) of AMD (n = 33,976) and COVID-19 (n ≥ 1,388,342) and subsequent analyses including expression quantitative trait locus (eQTL), differential gene expression, and Mendelian randomization (MR). We observed a significant genetic correlation between AMD and COVID-19 infection (r_G = 0.10, p = 0.02) and identified novel genome-wide significant associations near PDGFB (best SNP: rs130651; p = 2.4 × 10^-8) in the pleiotropy analysis of the two diseases. The disease-risk allele of rs130651 was significantly associated with increased gene expression levels of PDGFB in multiple tissues (best eQTL p = 1.8 × 10^-11 in whole blood) and immune cells (best eQTL p = 7.1 × 10^-20 in T-cells). PDGFB expression was observed to be higher in AMD cases than AMD controls {fold change (FC) = 1.02; p = 0.067}, as well as in the peak COVID-19 symptom stage (11-20 days after the symptom onset) compared to early/progressive stage (0-10 days) among COVID-19 patients over age 40 (FC = 2.17; p = 0.03) and age 50 (FC = 2.15; p = 0.04). Our MR analysis found that the liability of AMD risk derived from complement system dysfunction {OR (95% CI); hospitalization = 1.02 (1.01-1.03), infection = 1.02 (1.01-1.03) and increased levels of serum cytokine PDGF-BB {β (95% CI); critical illness = 0.07 (0.02-0.11)} are significantly associated with COVID-19 outcomes. Our study demonstrated that the liability of AMD is associated with an increased risk of COVID-19, and PDGFB may be responsible for the severe COVID-19 outcomes among AMD patients.

Relationships between Lipid-Related Metabolites and Age-Related Macular Degeneration Vary with Complement Genotype

OBJECTIVE

Lipid dysregulation and complement system (CS) activation are 2 important pathophysiology pathways for age-related macular degeneration (AMD). We hypothesized that the relationship between lipids and AMD may also differ according to CS genotype profile. Thus, the objective was to investigate the relationships between lipid-related metabolites and AMD according to CS genotypes.

DESIGN

Population-based cross-sectional study.

PARTICIPANTS

A total of 6947 participants from Singapore Epidemiology of Eye Diseases study with complete relevant data were included.

METHODS

We investigated a total of 32 blood lipid-related metabolites from nuclear magnetic resonance metabolomics data including lipoproteins and their subclasses, cholesterols, glycerides, and phospholipids, as well as 4 CS single nucleotide polymorphisms (SNPs): rs10922109 (complement factor H), rs10033900 (complement factor I), rs116503776 (C2-CFB-SKIV2L), and rs2230199 (C3). We first investigated the associations between AMD and the 32 lipid-related metabolites using multivariable logistic regression models. Then, to investigate whether the effect of lipid-related metabolites on AMD differ according to the CS SNPs, we tested the possible interactions between the CS SNPs and the lipid-related metabolites.

MAIN OUTCOME MEASURES

Age-related macular degeneration was defined using the Wisconsin grading system.

RESULTS

Among the 6947 participants, the prevalence of AMD was 6.1%, and the mean age was 58.3 years. First, higher levels of cholesterol in high-density lipoprotein (HDL) and medium and large HDL particles were associated with an increased risk of AMD, and higher levels of serum total triglycerides (TG) and several very-low-density lipoprotein subclass particles were associated with a decreased risk of AMD. Second, these lipids had significant interaction effects on AMD with 2 CS SNPs: rs2230199 and rs116503776 (after correction for multiple testing). For rs2230199, in individuals without risk allele, higher total cholesterol in HDL2 was associated with an increased AMD risk (odds ratio [OR] per standard deviation increase, 1.20; 95% confidence interval (CI), 1.06-1.37; P = 0.005), whereas, in individuals with at least 1 risk allele, higher levels of these particles were associated with a decreased AMD risk (OR, 0.69; 95% CI, 0.45-1.05; P = 0.079). Conversely, for rs116503776, in individuals without risk allele, higher serum total TG were associated with a decreased AMD risk (OR, 0.84; 95% CI, 0.74-0.95; P = 0.005), whereas, in individuals with 2 risk alleles, higher levels of these particles were associated with an increased risk of AMD (OR, 2.3, 95% CI, 0.99-5.39, P = 0.054).

CONCLUSIONS

Lipid-related metabolites exhibit opposite directions of effects on AMD according to CS genotypes. This indicates that lipid metabolism and CS may have synergistic interplay in the AMD pathogenesis.

Systems genomics in age-related macular degeneration

Genomic studies in age-related macular degeneration (AMD) have identified genetic variants that account for the majority of AMD risk. An important next step is to understand the functional consequences and downstream effects of the identified AMD-associated genetic variants. Instrumental for this next step are 'omics' technologies, which enable high-throughput characterization and quantification of biological molecules, and subsequent integration of genomics with these omics datasets, a field referred to as systems genomics. Single cell sequencing studies of the retina and choroid demonstrated that the majority of candidate AMD genes identified through genomic studies are expressed in non-neuronal cells, such as the retinal pigment epithelium (RPE), glia, myeloid and choroidal cells, highlighting that many different retinal and choroidal cell types contribute to the pathogenesis of AMD. Expression quantitative trait locus (eQTL) studies in retinal tissue have identified putative causal genes by demonstrating a genetic overlap between gene regulation and AMD risk. Linking genetic data to complement measurements in the systemic circulation has aided in understanding the effect of AMD-associated genetic variants in the complement system, and supports that protein QTL (pQTL) studies in plasma or serum samples may aid in understanding the effect of genetic variants and pinpointing causal genes in AMD. A recent epigenomic study fine-mapped AMD causal variants by determing regulatory regions in RPE cells differentiated from induced pluripotent stem cells (iPSC-RPE). Another approach that is being employed to pinpoint causal AMD genes is to produce synthetic DNA assemblons representing risk and protective haplotypes, which are then delivered to cellular or animal model systems. Pinpointing causal genes and understanding disease mechanisms is crucial for the next step towards clinical translation. Clinical trials targeting proteins encoded by the AMD-associated genomic loci C3, CFB, CFI, CFH, and ARMS2/HTRA1 are currently ongoing, and a phase III clinical trial for C3 inhibition recently showed a modest reduction of lesion growth in geographic atrophy. The EYERISK consortium recently developed a genetic test for AMD that allows genotyping of common and rare variants in AMD-associated genes. Polygenic risk scores (PRS) were applied to quantify AMD genetic risk, and may aid in predicting AMD progression. In conclusion, genomic studies represent a turning point in our exploration of AMD. The results of those studies now serve as a driving force for several clinical trials. Expanding to omics and systems genomics will further decipher function and causality from the associations that have been reported, and will enable the development of therapies that will lessen the burden of AMD.

Common and rare variants in patients with early onset drusen maculopathy

Early onset drusen maculopathy (EODM) can lead to advanced macular degeneration at a young age, affecting quality of life. However, the genetic causes of EODM are not well studied. We performed whole genome sequencing in 49 EODM patients. Common genetic variants were analysed by calculating genetic risk scores based on 52 age-related macular generation (AMD)-associated variants, and we analysed rare variants in candidate genes to identify potential deleterious variants that might contribute to EODM development. We demonstrate that the 52 AMD-associated variants contributed to EODM, especially variants located in the complement pathway. Furthermore, we identified 26 rare genetic variants predicted to be pathogenic based on in silico prediction tools or based on reported pathogenicity in literature. These variants are located predominantly in the complement and lipid metabolism pathways. Last, evaluation of 18 genes causing inherited retinal dystrophies that can mimic AMD characteristics, revealed 11 potential deleterious variants in eight EODM patients. However, phenotypic characteristics did not point towards a retinal dystrophy in these patients. In conclusion, this study reports new insights into rare variants that are potentially involved in EODM development, and which are relevant for future studies unravelling the aetiology of EODM.

Genetic Aspects of Age-Related Macular Degeneration and Their Therapeutic Potential

Age-related macular degeneration (AMD) is a complex and multifactorial disease, resulting from the interaction of environmental and genetic factors. The continuous discovery of associations between genetic polymorphisms and AMD gives reason for the pivotal role attributed to the genetic component to its development. In that light, genetic tests and polygenic scores have been created to predict the risk of development and response to therapy. Still, none of them have yet been validated. Furthermore, there is no evidence from a clinical trial that the determination of the individual genetic structure can improve treatment outcomes. In this comprehensive review, we summarize the polymorphisms of the main pathogenetic ways involved in AMD development to identify which of them constitutes a potential therapeutic target. As complement overactivation plays a major role, the modulation of targeted complement proteins seems to be a promising therapeutic approach. Herein, we summarize the complement-modulating molecules now undergoing clinical trials, enlightening those in an advanced phase of trial. Gene therapy is a potential innovative one-time treatment, and its relevance is quickly evolving in the field of retinal diseases. We describe the state of the art of gene therapies now undergoing clinical trials both in the field of complement-suppressors and that of anti-VEGF.

Pitfalls in complement analysis: A systematic literature review of assessing complement activation

Background

The complement system is an essential component of our innate defense and plays a vital role in the pathogenesis of many diseases. Assessment of complement activation is critical in monitoring both disease progression and response to therapy. Complement analysis requires accurate and standardized sampling and assay procedures, which has proven to be challenging.

Objective

We performed a systematic analysis of the current methods used to assess complement components and reviewed whether the identified studies performed their complement measurements according to the recommended practice regarding pre-analytical sample handling and assay technique. Results are supplemented with own data regarding the assessment of key complement biomarkers to illustrate the importance of accurate sampling and measuring of complement components.

Methods

A literature search using the Pubmed/MEDLINE database was performed focusing on studies measuring the key complement components C3, C5 and/or their split products and/or the soluble variant of the terminal C5b-9 complement complex (sTCC) in human blood samples that were published between February 2017 and February 2022. The identified studies were reviewed whether they had used the correct sample type and techniques for their analyses.

Results

A total of 92 out of 376 studies were selected for full-text analysis. Forty-five studies (49%) were identified as using the correct sample type and techniques for their complement analyses, while 25 studies (27%) did not use the correct sample type or technique. For 22 studies (24%), it was not specified which sample type was used.

Conclusion

A substantial part of the reviewed studies did not use the appropriate sample type for assessing complement activation or did not mention which sample type was used. This deviation from the standardized procedure can lead to misinterpretation of complement biomarker levels and hampers proper comparison of complement measurements between studies. Therefore, this study underlines the necessity of general guidelines for accurate and standardized complement analysis

Potential role of extracellular granzyme B in wet age-related macular degeneration and fuchs endothelial corneal dystrophy

Age-related ocular diseases are the leading cause of blindness in developed countries and constitute a sizable socioeconomic burden worldwide. Age-related macular degeneration (AMD) and Fuchs endothelial corneal dystrophy (FECD) are some of the most common age-related diseases of the retina and cornea, respectively. AMD is characterized by a breakdown of the retinal pigment epithelial monolayer, which maintains retinal homeostasis, leading to retinal degeneration, while FECD is characterized by degeneration of the corneal endothelial monolayer, which maintains corneal hydration status, leading to corneal edema. Both AMD and FECD pathogenesis are characterized by disorganized local extracellular matrix (ECM) and toxic protein deposits, with both processes linked to aberrant protease activity. Granzyme B (GrB) is a serine protease traditionally known for immune-mediated initiation of apoptosis; however, it is now recognized that GrB is expressed by a variety of immune and non-immune cells and aberrant extracellular localization of GrB substantially contributes to various age-related pathologies through dysregulated cleavage of ECM, tight junction, and adherens junction proteins. Despite growing recognition of GrB involvement in multiple age-related pathologies, its role in AMD and FECD remains poorly understood. This review summarizes the pathophysiology of, and similarities between AMD and FECD, outlines the current knowledge of the role of GrB in AMD and FECD, as well as hypothesizes putative contributions of GrB to AMD and FECD pathogenesis and highlights the therapeutic potential of pharmacologically inhibiting GrB as an adjunctive treatment for AMD and FECD.

Update on Viral Gene Therapy Clinical Trials for Retinal Diseases

In 2001, the first large animal was successfully treated with a gene therapy that restored its vision. Lancelot, the Briard dog that was treated, suffered from a human childhood blindness called Leber's congenital amaurosis type 2. Sixteen years later, the gene therapy was approved by the U.S. Food and Drug Administration. The success of this gene therapy in dogs led to a fast expansion of the ocular gene therapy field. By now every class of inherited retinal dystrophy has been treated in at least one animal model and many clinical trials have been initiated in humans. In this study, we review the status of viral gene therapies for the retina, with a focus on ongoing human clinical trials. It is likely that in the next decade we will see several new viral gene therapies approved.

SIG-1451, a Novel, Non-Steroidal Anti-Inflammatory Compound, Attenuates Light-Induced Photoreceptor Degeneration by Affecting the Inflammatory Process

Age-related macular degeneration is a progressive retinal disease that is associated with factors such as oxidative stress and inflammation. In this study, we evaluated the protective effects of SIG-1451, a non-steroidal anti-inflammatory compound developed for treating atopic dermatitis and known to inhibit Toll-like receptor 4, in light-induced photoreceptor degeneration. SIG-1451 was intraperitoneally injected into rats once per day before exposure to 1000 lx light for 24 h; one day later, optical coherence tomography showed a decrease in retinal thickness, and electroretinogram (ERG) amplitude was also found to have decreased 3 d after light exposure. Moreover, SIG-1451 partially protected against this decrease in retinal thickness and increase in ERG amplitude. One day after light exposure, upregulation of inflammatory response-related genes was observed, and SIG-1451 was found to inhibit this upregulation. Iba-1, a microglial marker, was suppressed in SIG-1451-injected rats. To investigate the molecular mechanism underlying these effects, we used lipopolysaccharide (LPS)-stimulated rat immortalised Müller cells. The upregulation of C-C motif chemokine 2 by LPS stimulation was significantly inhibited by SIG-1451 treatment, and Western blot analysis revealed a decrease in phosphorylated I-κB levels. These results indicate that SIG-1451 indirectly protects photoreceptor cells by attenuating light damage progression, by affecting the inflammatory responses.

Phenotypic Expression of CFH Rare Variants in Age-Related Macular Degeneration Patients in the Coimbra Eye Study

Purpose

To determine the association between rare genetic variants in complement factor H (CFH) and phenotypic features in age-related macular degeneration (AMD) patients from the Coimbra Eye Study (CES).

Methods

AMD patients from the Incidence CES (NCT02748824) underwent ophthalmologic examination and color fundus photography, spectral-domain optical coherence tomography (SD-OCT), fundus autofluorescence, and near-infrared imaging. Multimodal phenotypic characterization was carried out in a centralized reading center. The coding and splice-site regions of the CFH gene were sequenced through single-molecule molecular inversion probe-based next-generation sequencing in association with the EYE-RISK consortium. Variants with minor allele frequency <0.05 resulting in splice-site or protein change were selected. Differences in phenotypic features between carriers and noncarriers were analyzed using generalized estimated equations logistic regression models, considering intereye correlations.

Results

We included 39 eyes of 23 patients carrying rare CFH variants and 284 eyes of 188 noncarriers. Carrier status was associated with having higher drusen burden in the macula in the inner Early Treatment Diabetic Retinopathy Study circle (odds ratio [OR], 5.44 [95% confidence interval {CI}, 1.61-18.37]; P = 0.006), outer circle (OR, 4.37 [95% CI, 1.07-17.77]; P = 0.04), and full grid (OR, 4.82 [95% CI, 1.13-20.52]; P = 0.033). In SD-OCT, a lower total macular volume and lower inner retinal layers' volume (OR, 0.449 [95% CI, 0.226-0.894]; P = 0.023; OR, 0.496 [95% CI, 0.252-0.979]; P = 0.043) and pigment epithelial detachments (PEDs) (OR, 5.24 [95% CI, 1.08-25.44]; P = 0.04) were associated with carrying a rare CFH variant. Carriers with subretinal drusenoid deposits (SDD) had the rare variant P258L in all cases except one.

Conclusions

We identified in our cohort phenotypic differences between carriers and noncarriers of rare variants in the CFH gene. Carriers had more severe disease, namely superior drusen burden, PEDs, and thinner retinas. The rare variant P258L may be associated with SDD. Carriers are probably at increased risk of progression.

Molecular Genetic Mechanisms in Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is among the leading causes of irreversible blindness worldwide. In addition to environmental risk factors, such as tobacco use and diet, genetic background has long been established as a major risk factor for the development of AMD. However, our ability to predict disease risk and personalize treatment remains limited by our nascent understanding of the molecular mechanisms underlying AMD pathogenesis. Research into the molecular genetics of AMD over the past two decades has uncovered 52 independent gene variants and 34 independent loci that are implicated in the development of AMD, accounting for over half of the genetic risk. This research has helped delineate at least five major pathways that may be disrupted in the pathogenesis of AMD: the complement system, extracellular matrix remodeling, lipid metabolism, angiogenesis, and oxidative stress response. This review surveys our current understanding of each of these disease mechanisms, in turn, along with their associated pathogenic gene variants. Continued research into the molecular genetics of AMD holds great promise for the development of precision-targeted, personalized therapies that bring us closer to a cure for this debilitating disease.

Sex-Differences and Associations Between Complement Activation and Synovial Vascularization in Patients with Late-Stage Knee Osteoarthritis

Purpose

Synovial inflammation in knee osteoarthritis (OA) causes disorganized synovial angiogenesis and complement activation in synovial fluid, but links between complement and synovial microvascular pathology have not been established. Since complement causes vascular pathology in other diseases and since sex-differences exist in complement activation and in OA, we investigated sex differences in synovial fluid complement factors, synovial tissue vascular pathology, and associations between complement and synovial vascular pathology in patients with late-stage knee OA.

Methods

Patients with symptomatic, late-stage radiographic knee OA undergoing total knee arthroplasty or high tibial osteotomy provided matched synovial fluid and tissue biopsies during surgery. Complement factors (C2, C5, adipsin, MBL, and CFI) and terminal complement complex (sC5b-C9) were measured in synovial fluid by multiplex or enzyme-linked immunosorbent assay, respectively. Features of synovial vascular pathology (vascularization, perivascular edema, and vasculopathy) were assessed by histopathology. Multivariate linear regression models were used to assess associations between synovial fluid complement factors and histopathological features of vascular pathology, with adjustment for age, sex, body mass index, and sex interaction. Sex-disaggregated comparisons were completed.

Results

Synovial fluid biomarker and histopathology data were included from 97 patients. Most synovial fluid complement factors and synovial tissue histopathological features were similar between sexes. Synovial fluid C5 trended to lower levels in males (-20.93 ng/mL [95%CI -42.08, 0.23] p=0.05). Median vasculopathy scores (0.42 [95%CI 0.07, 0.77] p=0.02) were higher in males. In the full cohort, C5 concentration was associated with lower vascularization scores (-0.005 [95%CI -0.010, -0.0001] p=0.04) while accounting for sex*C5 interaction. In sex-disaggregated analyses, increased C5 concentration was associated with lower vascularization scores (-0.005 [95%CI –0.009, -0.0001] p=0.04) in male patients, but not in female patients. Males had higher sC5b-C9 compared to females. Additionally, males with high C5 had a higher synovial fluid concentration of sC5b-C9 compared to males with low C5. No differences were found in females.

Conclusion

Higher synovial fluid C5 levels were associated with increased complement activation and decreased synovial vascularization in males but not in females with OA. Future studies should test whether synovial fluid complement activation suppresses synovial angiogenesis and identify mechanisms accounting for C5-related sex-differences in synovial fluid complement activation in patients with knee OA.

Evaluating a Causal Relationship between Complement Factor I Protein Level and Advanced Age-Related Macular Degeneration Using Mendelian Randomization

Importance

Risk of advanced age-related macular degeneration (AAMD) is associated with rare genetic variants in the gene encoding Complement factor I (CFI), which is associated with lower circulating CFI protein levels, but the nature of the relationship is unclear.

Objective

Can genetic factors be used to infer whether low circulating CFI is associated with AAMD risk?

Design

Two-sample inverse variance weighted Mendelian Randomisation (MR) was used to evaluate evidence for a relationship between CFI levels and AAMD risk, comparing CFI levels from genetically predefined subsets in AAMD and control cohorts.

Setting

Published genetic and proteomic data was combined with data from cohorts of Geographic Atrophy (GA) patients in a series of MR analyses.

Participants

We derived genetic instruments for systemic CFI level in 3,301 healthy European participants in the INTERVAL study. To evaluate a genetic causal odds ratio (OR) for the effect of CFI levels on AAMD risk, we used results from a genome-wide association study of 12,711 AAMD cases and 14,590 European controls from the International AMD Genomics Consortium (IAMDGC), and CFI levels from patients entered into the research studies SCOPE and SIGHT.

Results

We identified one common CFI variant rs7439493 which was strongly associated with low CFI level, explaining 4.8% of phenotypic variance. Using rs7439493 our MR analysis estimated that AAMD odds increased per standard deviation (SD) decrease in CFI level; OR 1.47 (95% confidence interval (CI) 1.30-1.65, P=2.1×10-10). We identified one rare variant (rs141853578 encoding p.Gly119Arg) which was genome-wide significantly associated with CFI levels after imputation; based on this, a 1 SD decrease in CFI leads to increased AAMD odds of 1.79 (95% CI 1.46-2.19, P=1.9×10-8). The rare variant rs141853578 explained a further 1.7% of phenotypic variance. To benchmark the effect of low CFI levels on AAMD odds using a CFI-specific proteomic assay, we estimated the effect using CFI levels from 24 rs141853578 positive GA patients; each 1 SD (3.5μg/mL) reduction in CFI was associated with 1.67 fold increased odds of AAMD (95% CI 1.40-2.00, P=1.85×10-8).

Conclusion and relevance

Excellent concordance in direction and effect size derived from rare and common variant calculations provide good genetic evidence for a potentially causal role of lower CFI level increasing AAMD risk.

A Phase I, Single Ascending Dose Study of GEM103 (Recombinant Human Complement Factor H) in Patients with Geographic Atrophy

Purpose

To establish the safety, tolerability, pharmacokinetics, and pharmacodynamics of an intravitreal injection of recombinant human complement factor H (CFH), GEM103, in individuals with genetically defined age-related macular degeneration (AMD) and geographic atrophy (GA).

Design

Phase I single ascending-dose, open-label clinical trial (ClinicalTrials.gov identifier, NCT04246866).

Participants

Twelve individuals 50 years of age or older with a confirmed diagnosis of foveal GA in the study eye.

Methods

Participants were assigned to the increasing dose cohorts and received 1 50-μl intravitreal injection of GEM103 at doses of 50 μg/eye, 100 μg/eye, 250 μg/eye, or 500 μg/eye; dose escalation was dependent on the occurrence of dose-limiting toxicities.

Main Outcome Measures

Safety assessments included ocular and systemic adverse events (AEs), ocular examinations, clinical laboratory and vital signs, and serum antidrug antibody levels. Biomarkers, measured in the aqueous humor (AH), included CFH and complement activation biomarkers factor Ba and complement component 3a.

Results

No dose-limiting toxicities were reported, enabling escalation to the maximum study dose. No anti-GEM103 antidrug antibodies were detected during the study. Four participants experienced AEs; these were nonserious, mild or moderate in severity, and unrelated to GEM103. The AEs in 2 of these participants were related to the intravitreal injection procedure. No clinically significant ophthalmic changes and no ocular inflammation were observed. Visual acuity was maintained and stable throughout the 8-week follow-up period. No choroidal neovascularization occurred. CFH levels increased in a dose-dependent manner after GEM103 administration with supraphysiological levels observed at week 1; levels were more than baseline for 8 weeks or more in all participants receiving single doses of 100 μg or more. Complement activation biomarkers were reduced 7 days after dose administration.

Conclusions

A single intravitreal administration of GEM103 (up to 500 μg/eye) was well tolerated in individuals with GA. Of the few mild or moderate AEs reported, none were determined to be related to GEM103. No intraocular inflammation or choroidal neovascularization developed. CFH levels in AH were increased and stable for 8 weeks, with pharmacodynamic data suggesting that GEM103 restored complement regulation. These results support further development in a repeat-dose trial in patients with GA with AMD.

Complement-Amplifying Conditions in Atypical Hemolytic Uremic Syndrome: A Canadian Case Series

Rationale

Thrombotic microangiopathies (TMAs) are systemic disorders that often affect the kidneys and encompass a heterogeneous group of conditions, including atypical hemolytic uremic syndrome (aHUS). The complement pathway is thought to play a crucial role in the pathogenesis of aHUS, and a favorable response can be obtained through complement C5 inhibition. There is emerging evidence to suggest that the same is also true for several other forms of TMA.

Objective

The purpose of this series is to report cases of aHUS in which both an innate defect of the alternative complement pathway and a complement-amplifying condition were suspected.

Methods

This case series describes 8 patients who were managed in Canadian tertiary centers for aHUS and who presented initially with complement-amplifying conditions.

Results

In all cases, aHUS was associated with organ dysfunction and in some, with an innate defect of the alternative complement pathway. The complement-amplifying conditions identified were diverse including immune disorders, pregnancy, and a Shiga toxin infection. Patients improved rapidly when treated with eculizumab or plasma exchange.

Conclusions

These observations illustrate the seriousness of secondary aHUS. They also add to existing lines of evidence that the complement pathway is potentially involved in this condition and that it should be considered as a therapeutic target of interest under such circumstances.

Genetic Variants of Complement Factor H Y402H (rs1061170), C2 R102G (rs2230199), and C3 E318D (rs9332739) and Response to Intravitreal Anti-VEGF Treatment in Patients with Exudative Age-Related Macular Degeneration

Background and Objectives: To assess the association between the single nucleotide polymorphisms (SNPs) in the genes encoding complement factors CFH, C2, and C3 (Y402H rs1061170, R102G rs2230199, and E318D rs9332739, respectively) and response to intravitreal anti-vascular endothelial growth factor (VEGF) therapy in patients with exudative age-related macular degeneration (AMD). Materials and Methods: The study included 111 patients with exudative AMD treated with intravitreal bevacizumab or ranibizumab injections. Response to therapy was assessed on the basis of best-corrected visual acuity (BCVA) and central retinal thickness (CRT) measured every 4 weeks for 12 months. The control group included 58 individuals without AMD. The SNPs were genotyped by a real-time polymerase chain reaction in genomic DNA isolated from peripheral blood samples. Results: The CC genotype in SNP rs1061170 of the CFH gene was more frequent in patients with AMD than in controls (p = 0.0058). It was also more common among the 28 patients (25.2%) with poor response to therapy compared with good responders (p = 0.0002). Poor responders, especially those without this genotype, benefited from switching to another anti-VEGF drug. At the last follow-up assessment, carriers of this genotype had significantly worse BCVA (p = 0.0350) and greater CRT (p = 0.0168) than noncarriers. TT genotype carriers showed improved BCVA (p = 0.0467) and reduced CRT compared with CC and CT genotype carriers (p = 0.0194). No associations with AMD or anti-VEGF therapy outcomes for SNP rs9332739 in the C2 gene and SNP rs2230199 in the C3 gene were found. Conclusions: The CC genotype for SNP rs1061170 in the CFH gene was associated with AMD in our population. Additionally, it promoted a poor response to anti-VEGF therapy. On the other hand, TT genotype carriers showed better functional and anatomical response to anti-VEGF therapy at 12 months than carriers of the other genotypes for this SNP.

Functional analysis of rare genetic variants in complement factor I in advanced age-related macular degeneration

Factor I (FI) is a serine protease inhibitor of the complement system. Heterozygous rare genetic variants in complement factor I (CFI) are associated with advanced age-related macular degeneration (AMD). The clinical impact of these variants is unknown since a majority have not been functionally characterized and are classified as 'variants of uncertain significance' (VUS). This study assessed the functional significance of VUS in CFI. Our previous cross-sectional study using a serum-based assay demonstrated that CFI variants in advanced AMD can be categorized into three types. Type 1 variants cause a quantitative deficiency of FI. Type 2 variants demonstrate a qualitative deficiency. However, Type 3 variants consist of VUS that are less dysfunctional than Types 1 and 2 but are not as biologically active as wild type (WT). In this study, we employed site-directed mutagenesis followed by expression of the recombinant variant and a comprehensive set of functional assays to characterize nine Type 3 variants that were identified in 37 individuals. Our studies establish that the expression of the recombinant protein compared with WT is reduced for R202I, Q217H, S221Y and G263V. Further, G362A and N536K, albeit expressed normally, have significantly less cofactor activity. These results led to re-categorization of CFI variants R202I, Q217H, S221Y and G263V as Type 1 variants and to reclassification of N536K and G362A as Type 2. The variants K441R, Q462H and I492L showed no functional defect and remained as Type 3. This study highlights the utility of an in-depth biochemical analysis in defining the pathologic and clinical implications of complement variants underlying AMD.

Vitreous Humor Proteome: Targeting Oxidative Stress, Inflammation, and Neurodegeneration in Vitreoretinal Diseases

Oxidative stress is defined as an unbalance between pro-oxidants and antioxidants, as evidenced by an increase in reactive oxygen and reactive nitrogen species production over time. It is important in the pathophysiology of retinal disorders such as diabetic retinopathy, age-related macular degeneration, retinal detachment, and proliferative vitreoretinopathy, which are the focus of this article. Although the human organism’s defense mechanisms correct autoxidation caused by endogenous or exogenous factors, this may be insufficient, causing an imbalance in favor of excessive ROS production or a weakening of the endogenous antioxidant system, resulting in molecular and cellular damage. Furthermore, modern lifestyles and environmental factors contribute to increased chemical exposure and stress induction, resulting in oxidative stress. In this review, we discuss the current information about oxidative stress and the vitreous proteome with a special focus on vitreoretinal diseases. Additionally, we explore therapies using antioxidants in an attempt to rescue the body from oxidation, restore balance, and maximize healthy body function, as well as new investigational therapies that have shown significant therapeutic potential in preclinical studies and clinical trial outcomes, along with their goals and strategic approaches to combat oxidative stress.

Complement cascade inhibition in geographic atrophy: a review

The pathophysiology of dry age-related macular degeneration (AMD) and specifically geographic atrophy (GA) has been linked to the complement cascade. This cascade is part of the innate immune system and is made up of the classical, alternative, and lectin pathways. The pathways comprise a system of plasma and membrane-associated serum proteins that are activated with identification of a nonself entity. A number of these proteins have been implicated in the development and progression of dry AMD. The three pathways converge at C3 and cascade down through C5, making both of these proteins viable targets for the treatment of dry AMD. In addition, there are a number of complement factors, CFB, CFD, CFH, and CFI, which are potential therapeutic targets as well. Several different complement-directed therapeutics are being studied for the treatment of dry AMD with the hope that one of these approaches will emerge as the first approved treatment for GA.

Osteopontin accumulates in basal deposits of human eyes with age-related macular degeneration and may serve as a biomarker of aging

A common clinical phenotype of several neurodegenerative and systemic disorders including Alzheimer's disease and atherosclerosis is the abnormal accumulation of extracellular material, which interferes with routine cellular functions. Similarly, patients with age-related macular degeneration (AMD), the leading cause of vision loss among the aged population, present with extracellular lipid- and protein-filled basal deposits in the back of the eye. While the exact mechanism of growth and formation of these deposits is poorly understood, much has been learned from investigating their composition, providing critical insights into AMD pathogenesis, prevention, and therapeutics. We identified human osteopontin (OPN), a phosphoprotein expressed in a variety of tissues in the body, as a newly discovered component of basal deposits in AMD patients, with a distinctive punctate staining pattern. OPN expression within these lesions, which are associated with AMD disease progression, were found to co-localize with abnormal calcium deposition. Additionally, OPN puncta colocalized with an AMD risk-associated complement pathway protein, but not with apolipoprotein E or vitronectin, two other well-established basal deposit components. Mechanistically, we found that retinal pigment epithelial cells, cells vulnerable in AMD, will secrete OPN into the extracellular space, under oxidative stress conditions, supporting OPN biosynthesis locally within the outer retina. Finally, we report that OPN levels in plasma of aged (non-AMD) human donors were significantly higher than levels in young (non-AMD) donors, but were not significantly different from donors with the different clinical subtypes of AMD. Collectively, our study defines the expression pattern of OPN in the posterior pole as a function of disease, and its local expression as a potential histopathologic biomarker of AMD.