Altered proportion of CCR2+ and CX3CR1+ circulating monocytes in neovascular age-related macular degeneration and polypoidal choroidal vasculopathy

Dynamic changes in macrophage morphology during the progression of choroidal neovascularization in a laser-induced choroidal neovascularization mouse model

BACKGROUND

Neovascular age-related macular degeneration (AMD) is responsible for the majority of severe vision loss cases and is mainly caused by choroidal neovascularization (CNV). This condition persists or recurs in a subset of patients and regresses after 5 or more years of anti-vascular endothelial growth factor (VEGF) treatment. The precise mechanisms of CNV continue to be elucidated. According to our previous studies, macrophages play a critical role in CNV. Herein, we aimed to determine the morphological changes in macrophages in CNV to help us understand the dynamic changes.

METHODS

Mice were subjected to laser injury to induce CNV, and lesion expansion and macrophage transformation were examined by immunofluorescence and confocal analysis. Several strategies were used to verify the dynamic changes in macrophages. Immunofluorescence and confocal assays were performed on choroidal flat mounts to evaluate the morphology and phenotype of macrophages in different CNV phases, and the results were further verified by western blotting and RT-PCR.

RESULTS

The location of infiltrated macrophages changed after laser injury in the CNV mouse model, and macrophage morphology also dynamically changed. Branching macrophages gradually shifted to become round with the progression of CNV, which was certified to be an M2 phenotypic shift.

CONCLUSIONS

Dynamic changes in macrophage morphology were observed during CNV formation, and the round-shaped M2 phenotype could promote neovascularization. In general, the changes in morphology we observed in this study can help us to understand the critical role of macrophages in CNV progression and exploit a potential treatment option for CNV indicated by a shift in macrophage polarity.

Serum levels of IL-4, IL-13 and IL-33 in patients with age-related macular degeneration and myeloproliferative neoplasms

Immune responses play a key role in the pathogenesis and progression of myeloproliferative neoplasms (MPN) and age-related macular degeneration (AMD). Recent studies suggested using MPNs as a "Human Inflammation Model" of drusen development and previous results showed interleukin-4 (IL-4) dysregulation in MPN and AMD. IL-4, IL-13 and IL-33 are all cytokines involved in the type 2 inflammatory response. This study investigated the cytokine levels of IL-4, IL-13 and IL-33 in serum of MPN and AMD patients. This cross-sectional study included 35 patients with MPN with drusen (MPNd) and 27 with MPN and normal retinas (MPNn), 28 patients with intermediate AMD (iAMD) and 29 with neovascular AMD (nAMD). With immunoassays, we quantified and compared levels of IL-4, IL-13 and IL-33 in serum between the groups. The study was conducted at Zealand University Hospital, Roskilde, Denmark, between July 2018 and November 2020. The serum levels of IL-4 were significantly higher in the MPNd group than in the MPNn group (p = 0.003). In regard to IL-33, the difference between MPNd and MPNn was not significant (p = 0.069), however, when subdivided into subgroups, a significant difference was found between polycythemia vera patients with drusen and those without drusen (p = 0.005). We found no IL-13 difference between the MPNd and MPNn groups. Our data didn't show any significant IL-4 or IL-13 serum level difference between the MPNd and iAMD groups but in regard to IL-33, data recorded a significant serum level difference between the two groups. There was no statistically significant difference between the MPNn, iAMD and nAMD groups in levels of IL-4, IL-13 and IL-33. These findings suggested that the serum levels of IL-4 and IL-33 might play a role in drusen development in MPN patients. The results might represent the type 2 inflammatory arm of the disease. The findings support the association between chronic inflammation and drusen.

Association between oral metformin use and the risk of age-related macular degeneration: A systematic review with meta-analysis

Rodent studies demonstrate that oral metformin use may reduce chronic low-grade inflammation, downregulate apoptosis and extend life span. Emerging epidemiological evidence suggests that oral metformin use may protect against development of age-related macular degeneration (AMD) in humans. In this study, we systematically reviewed the literature on the association between oral metformin use and AMD in patients with type 2 diabetes and conducted a quantitative meta-analysis to provide a summary estimate of the association. We searched 12 literature databases on 10 August 2022 and identified nine eligible studies with data on a total of 1 427 074 individuals with diabetes. We found that patients with diabetes using metformin had a significantly lower odds ratio (OR) of having or developing AMD (OR 0.63; 95% CI: 0.46-0.86; p = 0.004). Our analyses also revealed that although the findings were robust in the sensitivity analysis, the Funnel plot indicated a certain publication bias towards finding a protective effect. Results of individual studies suggested inconsistent findings, as some studies found lower risk of AMD from higher total metformin exposure, whereas other studies found a higher risk of AMD from higher total metformin exposure. Taken together, there may be a link between metformin use and lower risk of AMD, but the relationship is only studied in observational studies, various sources of bias can be speculated to influence, and careful interpretation is warranted.

The role of NAD+ metabolism in macrophages in age-related macular degeneration

Age-related macular degeneration (AMD) is a leading cause of legal blindness and moderate and severe vision impairment (MSVI) in people older than 50 years. It is classified in various stages including early, intermediate, and late stage. In the early stages, innate immune system, especially macrophages, play an essential part in disease onset and progression. NAD⁺ is an essential coenzyme involved in cellular senescence and immune cell function, and its role in age-related diseases is gaining increasing attention. The imbalance between the NAD⁺ synthesis and consumption causes the fluctuation of intracellular NAD⁺ level which determines the polarization fate of macrophages. In AMD, the over-expression of NAD⁺-consuming enzymes in macrophages leads to declining of NAD⁺ concentrations in the microenvironment. This phenomenon triggers the activation of inflammatory pathways in macrophages, positive feedback aggregation of inflammatory cells and accumulation of reactive oxygen species (ROS). This review details the role of NAD⁺ metabolism in macrophages and molecular mechanisms during AMD. The selected pathways were identified as potential targets for intervention in AMD, pending further investigation.

Circulating inflammatory monocytes oppose microglia and contribute to cone cell death in retinitis pigmentosa

Retinitis pigmentosa (RP) is an intractable inherited disease that primarily affects the rods through gene mutations followed by secondary cone degeneration. This cone-related dysfunction can lead to impairment of daily life activities, and ultimately blindness in patients with RP. Paradoxically, microglial neuroinflammation contributes to both protection against and progression of RP, but it is unclear which population(s) - tissue-resident microglia and/or peripheral monocyte-derived macrophages (mφ) - are implicated in the progression of the disease. Here we show that circulating blood inflammatory monocytes (IMo) are key effector cells that mediate cone cell death in RP. Attenuation of IMo and peripherally engrafted mφ by Ccl2 deficiency or immune modulation via intravenous nano-particle treatment suppressed cone cell death in rd10 mice, an animal model of RP. In contrast, the depletion of resident microglia by a colony-stimulating factor 1 receptor inhibitor exacerbated cone cell death in the same model. In human patients with RP, IMo was increased and correlated with disease progression. These results suggest that peripheral IMo is a potential target to delay cone cell death and prevent blindness in RP.

Patients with MPNs and retinal drusen show signs of complement system dysregulation and a high degree of chronic low-grade inflammation

BACKGROUND

The hematopoietic stem cell disorders, myeloproliferative neoplasms (MPNs), are characterised by chronic low-grade inflammation (CLI). Recently, we showed that patients with MPNs have an increased prevalence of drusen and age-related macular degeneration (AMD), and drusen prevalence seemed associated with higher CLI. Studying MPNs may reveal more about drusen pathophysiology. This study investigated CLI further by measuring cytokine levels and complement system markers, comparing these between patients with MPNs and AMD.

METHODS

This cross-sectional study, between July 2018 and November 2020 conducted at Zealand University Hospital (ZUH) - Roskilde, Denmark, included 29 patients with neovascular AMD (nAMD), 28 with intermediate-stage AMD (iAMD), 62 with MPNs (35 with drusen - MPNd and 27 with healthy retinas - MPNn). With flow cytometry, we measured complement-regulatory-proteins (Cregs). With immunoassays, we investigated cytokine levels combined into a summary-inflammation-score (SIS).

FINDINGS

The MPNd and nAMD groups had similar SIS, significantly higher than the MPNn and iAMD groups. Additionally, we found SIS to increase over the MPN biological continuum from early cancer stage, essential thrombocytaemia (ET), over polycythaemia vera (PV) to the late-stage primary myelofibrosis (PMF). MPNs showed signs of complement dysregulation, with Cregs expression lower in PV than ET and PMF and even lower in PV patients with drusen.

INTERPRETATION

This study suggests that MPNd have a higher CLI than MPNn and may indicate systemic CLI to play a greater part in, and even initiate drusen formation. We suggest using MPNs as a "Human Inflammation Model" of drusen development. The CLI in MPNs elicits drusen formation, triggering more CLI creating a vicious cycle, increasing the risk of developing AMD.

FUNDING

Fight for Sight, Denmark, and Region Zealand's research promotion fund.

Retinal drusen in patients with chronic myeloproliferative blood cancers are associated with an increased proportion of senescent T cells and signs of an aging immune system

The cause of age-related macular degeneration (AMD) is unknown, but evidence indicates that both innate and adaptive immunity play a role in the pathogenesis. Our recent work has investigated AMD in patients with myeloproliferative neoplasms (MPNs) since they have increased drusen and AMD prevalence. We have previously found increased levels of chronic low-grade inflammation (CLI) in MPN patients with drusen (MPNd) compared to MPN patients with normal retinas (MPNn). CLI and AMD are both associated with aging, and we, therefore, wanted to study immunosenescence markers in MPNd, MPNn, and AMD. The purpose was to identify differences between MPNd and MPNn, which might reveal novel information relevant to drusen pathophysiology and thereby the AMD pathogenesis. Our results suggest that MPNd have a T cell differentiation profile resembling AMD and more effector memory T cells than MPNn. The senescence-associated-secretory-phenotype (SASP) is associated with effector T cells. SASP is thought to play a role in driving CLI seen with advancing age. Senescent cells with SASP may damage healthy tissue, including the eye tissues affected in AMD. The finding of increased effector cells in MPNd could implicate a role for adaptive immunity and senescent T cells together with increased CLI in drusen pathophysiology.

Complement Activation Products and Cytokines in Pachychoroid Neovasculopathy and Neovascular Age-Related Macular Degeneration

Purpose

To investigate the characteristics of complement activation products and angiogenic cytokines in the aqueous humor in eyes with pachychoroid neovasculopathy (PNV) and neovascular age-related macular degeneration (nAMD).

Methods

This was a prospective, comparative, observational study. All patients with choroidal neovascularization were classified as PNV without polyps, PNV with polyps (polypoidal choroidal vasculopathy [PCV]), or drusen-associated nAMD according to the presence or absence of pachychoroid features and soft drusen. This study included a total of 105 eyes. Aqueous humor samples were collected from 25 eyes with PNV without polyps, 23 eyes with PCV, and 24 eyes with drusen-associated nAMD before intravitreal anti-vascular endothelial growth factor (VEGF) injection and cataract surgery in 33 control eyes. Clinical samples were measured for complement component 3a (C3a), C4a, C5a, VEGF, and macrophage chemoattractant protein 1 (MCP-1) using a bead-based immunoassay.

Results

C3a and MCP-1 levels were significantly higher in PCV (P = 0.032 and P = 0.039, respectively) and drusen-associated nAMD (P = 0.01 for both comparisons) than in controls, and no difference was seen in C3a and MCP-1 levels between PNV and controls (P = 0.747 and P = 0.294, respectively). VEGF levels were significantly higher in PNV (P = 0.016), PCV (P = 0.009), and drusen-associated nAMD (P = 0.043) than in controls. In PNV, the VEGF levels elevated without elevated C3a and MCP-1.

Conclusions

PNV, PCV, and drusen-associated nAMD had significantly distinct profiles of complement activation products and cytokines in the aqueous humor.

Deficits in Monocyte Function in Age Related Macular Degeneration: A Novel Systemic Change Associated With the Disease

Age-related macular degeneration (AMD) is characterized by the accumulation of debris in the posterior eye. In this study we evaluated peripheral blood monocyte phagocytic function at various stages of AMD and in aged matched control participants. Real-time tri-color flow cytometry was used to quantify phagocytic function of peripheral blood monocyte subsets (non-classic, intermediate and classic) isolated from subjects with intermediate or late AMD and compared with age matched healthy controls. Assessment of phagocytic function of monocytes isolated from those with and without reticular pseudodrusen was also made, and the effect of glatiramer acetate on phagocytic function assessed. Phagocytic function was reduced in all subjects with AMD, irrespective of stage of disease. However, there was no correlation between phagocytic function and drusen load, nor any difference between the level of phagocytosis in those with or without reticular pseudodrusen. Treatment with glatiramer acetate increased phagocytosis of classical and non-classical monocytes, normalizing the reduction in phagocytosis observed in those with AMD. These findings suggest that defective systemic phagocytosis is associated with both intermediate and late stages of AMD, highlighting a potential role in the accumulation of debris that occurs early in the disease process. Assessing peripheral monocyte phagocytic function provides further insights into the etiology of this disease and offer a novel therapeutic target.

Idiopathic polypoidal choroidal vasculopathy: a review of literature with clinical update on current management practices

PURPOSE

Polypoidal choroidal vasculopathy is a major cause of visual disability in a vast majority of Asian population due to exudative maculopathy. Although it is a distinctive disease entity with characteristic pathophysiology, genetics, immunology and clinical features, but it is still misdiagnosed as neovascular age related macular degeneration as both the diseases are a part of pachychoroid spectrum and have some similar features. Also, there are varied options for the management of this disease, but there are no clear recommendations. So, a detailed review of the literature has been done along with special attention to the recent therapeutic advances to help the readers get a better understanding of the disease and its current management practices.

METHOD

Detailed review of literature regarding polypoidal choroidal vasculopathy was done. The disease pathophysiology, genetics, risk factors, diagnostic modalities along with current treatment guidelines were extensively studied and compiled.

RESULT

A comprehensive clinical update on polypoidal choroidal vasculopathy was compiled with special emphasis on the recent diagnostic modalities and treatment guidelines.

CONCLUSION

Polypoidal choroidal vasculopathy is a distinct clinical entity which can be diagnosed based on indocyanine green angiography and optical coherence tomography. Treatment includes various options like photodynamic therapy, anti VEGF agents and thermal laser ablation. A review of literature has been done and recent diagnostic modalities with management practices have been compiled for the better understanding of the disease.

Systemic levels of C-reactive protein in patients with age-related macular degeneration: A systematic review with meta-analyses

Ageing of the retina is associated with the gradual accumulation of basal deposits and the formation of drusen. However, in some individuals this process is exacerbated and causes development of age-related macular degeneration. Late features of age-related macular degeneration include geographic atrophy of the neuroretina or choroidal neovascularization. Such changes lead to blurred vision, metamorphopsia, and scotoma, and is the leading cause of vision loss in developed countries. Chronic low-grade inflammation has been investigated because of its relationship to ageing and its role in the gap between chronological and biological ageing. Here, we systematically reviewed studies investigating systemic C-reactive protein in patients with age-related macular degeneration. We identified 53 studies with 60,598 participants (10,392 patients and 38,901 controls). Our meta-analyses revealed that early age-related macular degeneration was not associated to systemic C-reactive protein (Cohen's d = 0.03 [-0.04 to 0.10]; OR = 1.06 [0.93-1.20]; P = 0.39) whereas late age-related macular degeneration (Cohen's d = 0.38 [0.24 to 0.51]; OR = 1.99 [1.55-2.52]; P < 0.0001), and neovascular age-related macular degeneration (Cohen's d = 0.40 [0.24 to 0.56]; OR = 2.07 [1.55-2.76]; P < 0.0001) was associated with a small-to-moderate increase in systemic C-reactive protein. Our review provides an overview of this extensively studied field, provide summary estimates that provide insight into when and to what extent systemic C-reactive protein is associated with age-related macular degeneration, and help in distinguishing the potentially reversible disease processes from that of irreversible retinal ageing.

Plasma levels of inflammatory chemokines in patients with polypoidal choroidal vasculopathy

PURPOSE

Chemokines are a group of cytokines that guide immune cell migration. We studied plasma levels of inflammatory chemokines in patients with polypoidal choroidal vasculopathy (PCV) and compared with healthy age-matched control individuals.

METHODS

This was a clinic-based prospective case-control study of participants (n = 60) with either PCV (n = 26) or age-matched healthy controls (n = 34). We sampled fresh venous blood and isolated plasma for analysis. We used U-PLEX Human Assays to quantify concentrations of the inflammatory chemokines MCP-1/CCL2, RANTES/CCL5, eotaxin/CCL11, IP-10/CXCL10 and fractalkine/CX3CL1.

RESULTS

Plasma levels of fractalkine was significantly higher in patients with PCV when compared to healthy controls (mean ± SD: 7291 ± 2461 pg/ml versus 5879 ± 2001 pg/ml; p = 0.021). Plasma levels of MCP-1 (p = 0.846), RANTES (p = 0.288), eotaxin (p = 0.496) and IP-10 (p = 0.352) did not differ significantly between the groups. To evaluate possible biomarker quality of fractalkine, we used a ROC analysis and found a positive but weak discriminatory ability (AUC = 0.68).

CONCLUSION

Patients with PCV have a higher plasma level of fractalkine. Although the differences do not possess strong biomarker qualities, they inform on disease processes of a poorly understood disease and suggest that the fractalkine-CX3CR1 axis may be involved. As this study did not investigate local chemokine concentrations, we are unable to confirm or disprove any local chorioretinal interaction, and our findings should be interpreted with such caution.

Plasma Levels of Matrix Metalloprotease MMP-9 and Tissue Inhibitor TIMP-1 in Caucasian Patients with Polypoidal Choroidal Vasculopathy

BACKGROUND

Matrix metalloproteinase 9 (MMP-9) and tissue inhibitor of metalloproteinases 1 (TIMP-1) are regulating enzymes of the extracellular matrix. A systemic imbalance of MMP-9 and TIMP-1, thought to reflect an imbalance of the extracellular matrix homeostasis, is previously associated with polypoidal choroidal vasculopathy (PCV) in Asian patients. Previous studies suggest inter-ethnical differences in the genetic background and etiology of PCV. To further explore this issue, we studied the plasma levels of MMP-9 and TIMP-1 in Caucasian patients with PCV and compared to healthy age-matched controls.

METHODS

For this prospective case-control study, 60 participants were recruited who were either patients with PCV (n = 26) or healthy controls (n = 34). All participants underwent detailed clinical examination. We sampled fresh venous blood, isolated plasma, and quantified plasma concentrations of the extracellular matrix regulators MMP-9 and TIMP-1 using electrochemiluminescence immunoassays.

RESULTS

Plasma levels of MMP-9 (p = 0.4), TIMP-1 (p = 0.9), and MMP-9/TIMP-1 ratio (p = 0.4) did not differ significantly between patients with PCV and healthy controls. No differences appeared after adjusting for influencing co-variates in multivariate analyses.

CONCLUSION

We demonstrate that Caucasian patients with PCV do not have altered levels of plasma MMP-9 or plasma TIMP-1. These findings suggest no strong evidence of a systemic imbalance of the extracellular matrix homeostasis in Caucasian patients with PCV. Our findings are in line with studies of other aspects of PCV that are also subject to significant inter-ethnical differences.

Potential Role of Myeloid-Derived Suppressor Cells (MDSCs) in Age-Related Macular Degeneration (AMD)

Myeloid cells, such as granulocytes/neutrophils and macrophages, have responsibilities that include pathogen destruction, waste material degradation, or antigen presentation upon inflammation. During persistent stress, myeloid cells can remain partially differentiated and adopt immunosuppressive functions. Myeloid-derived suppressor cells (MDSCs) are primarily beneficial upon restoring homeostasis after inflammation. Because of their ability to suppress adaptive immunity, MDSCs can also ameliorate autoimmune diseases and semi-allogenic responses, e.g., in pregnancy or transplantation. However, immunosuppression is not always desirable. In certain conditions, such as cancer or chronically inflamed tissue, MDSCs prevent restorative immune responses and thereby aggravate disease progression. Age-related macular degeneration (AMD) is the most common disease in Western countries that severely threatens the central vision of aged people. The pathogenesis of this multifactorial disease is not fully elucidated, but inflammation is known to participate in both dry and wet AMD. In this paper, we provide an overview about the potential role of MDSCs in the pathogenesis of AMD.

Association of CD11b+ Monocytes and Anti-Vascular Endothelial Growth Factor Injections in Treatment of Neovascular Age-Related Macular Degeneration and Polypoidal Choroidal Vasculopathy

Importance

CD11b+ immune cells have been implicated in the formation of choroidal neovascularization in experimental studies on animals and disease-association studies on humans. However, the clinical importance of such observations remains unknown.

Objective

To investigate whether the proportion of CD11b+ circulating monocytes is associated with the number of anti-vascular endothelial growth factor (anti-VEGF) injections in neovascular age-related macular degeneration (AMD) and polypoidal choroidal vasculopathy (PCV).

Design, Setting, and Participants

These observational cohort studies collected data from January 1, 2010, through December 31, 2013, and from January 1, 2015, through December 31, 2018. Fresh venous blood samples were acquired for flow cytometric immune studies in patients with neovascular AMD or PCV receiving treatment with aflibercept or ranibizumab as needed for 36 months. Patients (n = 81) without immune diseases were consecutively recruited from a single center in Denmark.

Exposures

Proportion of CD11b+ circulating monocytes.

Main Outcomes and Measures

The estimation of the number of intravitreal anti-VEGF injections given at 12, 24, and 36 months by the proportion of CD11b+ circulating monocytes and the correlation between these values. The angiogenic role of CD11b+ circulating monocytes was further evaluated by investigating the expression of the known proangiogenic receptor CCR2.

Results

Eighty-one patients were included in the analysis (54% women; mean [SD] age, 76 [7] years). The proportion of CD11b+ monocytes at baseline positively estimated the future number of anti-VEGF injections at 12 (ρ = 0.77; 95% CI, 0.35-0.93; P = .004), 24 (ρ = 0.82; 95% CI, 0.44-0.95; P = .002), and 36 (ρ = 0.78; 95% CI, 0.34-0.94; P = .005) months. This association was also found retrospectively in a larger sample of patients with neovascular AMD at 12 (ρ = 0.46; 95% CI, 0.16-0.68; P = .004), 24 (ρ = 0.49; 95% CI, 0.20-0.70; P = .002), and 36 (ρ = 0.65; 95% CI, 0.41-0.80; P < .001) months and patients with PCV at 12 (ρ = 0.27; 95% CI, -0.28 to 0.68; P = .30), 24 (ρ = 0.60; 95% CI, 0.12-0.85; P = .02), and 36 (ρ = 0.70; 95% CI, 0.27-0.90; P = .005) months, suggesting that this association is not specific to AMD but rather reflects VEGF activity in neovascularization. CD11b+ monocytes highly coexpressed CCR2, an important monocytic marker of proangiogenic activity.

Conclusions and Relevance

Results of this study demonstrated that the proportion of circulating CD11b+ monocytes estimated and correlated with the number of anti-VEGF injections in patients with neovascular AMD and PCV. Additional longitudinal studies are needed to determine whether these findings have clinical relevance to influence treatment algorithms or provide novel targets for medical therapy.

Contribution of microglia and monocytes to the development and progression of age related macular degeneration

PURPOSE

Age related macular degeneration (AMD) is the leading cause of irreversible vision loss in industrialised nations. Based on genetics, as well as proteome analysis of drusen, the role the innate immune system in the development and/or progression of the disease is well established. Mononuclear phagocytes, such as microglia and monocytes, play critical roles in innate immunity. Here, the role of retinal microglia in mediating normal retinal function, and how these cells change with age is discussed, so as to understand their role in the development and progression of AMD.

RECENT FINDINGS

It is now known that microglia dynamically survey the neural environment, responding rapidly to even the most subtle neural injury. The dynamic and phagocytic roles of microglia can change with age contributing to alteration in the response of these cells to damage with age. Accumulation of innate immune cells in the subretinal space is a hallmark feature of the development of AMD, reflecting either an increase in migration of monocytes into the retina, or a failure of immune cell elimination from the retina. Furthermore, changes in phagocytic ability of immune cells could contribute to the accumulation of drusen deposits in the posterior eye.

SUMMARY

An overview of how retinal microglia maintain retinal homeostasis under normal conditions is provided, and then how they contribute to each stage of AMD. In addition, circulating monocytes are altered in those with AMD, contributing to the overall inflammatory state. Understanding the role of cells of the innate immune system in AMD may uncover novel therapeutic targets with which to reduce either the development or progression of disease.

Age-related macular degeneration: A two-level model hypothesis

Age-related diseases, including age-related macular degeneration (AMD), are of growing importance in a world where population ageing has become a dominant global trend. Although a wide variety of risk factors for AMD have been identified, age itself remains by far the most important risk factor, making it an urgent priority to understand the connections between underlying ageing mechanisms and pathophysiology of AMD. Ageing is both multicausal and variable, so that differences between individuals in biological ageing processes are the focus of a growing number of pathophysiological studies seeking to explain how ageing contributes to chronic, age-related conditions. The aim of this review is to integrate the available knowledge on the pathophysiology of AMD within the framework of the biology of ageing. One highly significant feature of biological ageing is systemic inflammation, which arises as a second-level response to a first level of molecular damage involving oxidative stress, mutations etc. Combining these insights, the various co-existing pathophysiological explanations in AMD arrange themselves according to a two-level hypothesis. Accordingly, we describe how AMD can be considered the consequence of age-related random accumulation of molecular damage at the ocular level and the subsequent systemic inflammatory host response thereof. We summarize evidence and provide original data to enlighten where evidence is lacking. Finally, we discuss how this two-level hypothesis provides a foundation for thoughts and future studies in prevention, prognosis, and intervention.

Effects of senescent secretory phenotype acquisition on human retinal pigment epithelial stem cells

Regenerative medicine approaches based on mesenchymal stem cells (MSCs) are being investigated to treat several aging-associated diseases, including age-related macular degeneration (AMD). Loss of retinal pigment epithelium (RPE) cells occurs early in AMD, and their transplant has the potential to slow disease progression.

The human RPE contains a subpopulation of cells - adult RPE stem cells (RPESCs) – that are capable of self-renewal and of differentiating into RPE cells in vitro. However, age-related MSC changes involve loss of function and acquisition of a senescence-associated secretory phenotype (SASP), which can contribute to the maintenance of a chronic state of low-grade inflammation in tissues and organs.

In a previous study we isolated, characterized, and differentiated RPESCs. Here, we induced replicative senescence in RPESCs and tested their acquisition of the senescence phenotype and the SASP as well as the differentiation ability of young and senescent RPESCs.

Senescent RPESCs showed a significantly reduced proliferation ability, high senescence-associated β-galactosidase activity, and SASP acquisition. RPE-specific genes were downregulated and p21 and p53 protein expression was upregulated.

These findings document the effects of senescence and SASP acquisition on RPESC differentiation ability and highlight the need for a greater understanding of their role in AMD pathogenesis.

Neutrophil-to-lymphocyte ratio in age-related macular degeneration: a systematic review and meta-analysis

Age-related macular degeneration (AMD) is aetiologically linked to immunological ageing and dysfunction. One aspect of this is the altered neutrophil-to-lymphocyte ratio (NLR), which in other domains have been associated with inflammation and angiogenesis, and therefore investigated in patients with AMD in several papers. In this systematic review and meta-analysis, we summarize findings in patients with AMD in relation to NLR, both qualitatively and quantitatively. We searched PubMed/MEDLINE, EMBASE, Web of Science, and the Cochrane Central and identified six studies from where we extracted data on 1178 individuals (777 patients with AMD and 401 healthy controls). Patients with AMD had a higher NLR (weighted mean difference: 0.37, CI 95% 0.08 to 0.66, p = 0.013) when compared to healthy controls. In subgroup analyses, we did not find a significant difference between patients with dry AMD and healthy controls (weighted mean difference: 0.34, CI 95% -0.03 to 0.69, p = 0.068), but did find a strong significant difference between patients with neovascular AMD and healthy controls (weighted mean difference: 0.54, CI 95% 0.23 to 0.86, p = 0.00068). Hence, we find that the association between AMD and elevated NLR may have stronger relevance to the neovascular subtype of AMD. However, the clinical value of measuring the NLR remains unclear.

The transcriptome of peripheral blood mononuclear cells in patients with clinical subtypes of late age-related macular degeneration

Background

Peripheral blood mononuclear cells (PBMCs) are implicated in the pathogenesis of age-related macular degeneration (AMD). We here mapped the global gene transcriptome of PBMCs from patients with different clinical subtypes of late AMD.

Results

We sampled fresh venous blood from patients with geographic atrophy (GA) secondary to AMD without choroidal neovascularizations (n = 19), patients with neovascular AMD without GA (n = 38), patients with polypoidal choroidal vasculopathy (PCV) (n = 19), and aged control individuals with healthy retinae (n = 20). We isolated PBMCs, extracted RNA, and used microarray to investigate gene expression. Volcano plots identified statistically significant differentially expressed genes (P < 0.05) at a high magnitude (≥30% higher/lower) for GA (62 genes), neovascular AMD (41 genes), and PCV (41 genes). These clinical subtypes differed substantially across gene expression and the following pathways identified in enrichment analyses. In a subgroup analysis, we investigated presence vs. absence of subretinal fibrosis and found 826 differentially expressed genes (≥30% higher/lower, P < 0.05) with relation to mRNA splicing, endothelial migration, and interleukin-1 signaling.

Conclusions

We here map the global gene transcriptome of PBMCs related to clinical subtypes of late AMD and find evidence of subtype-specific immunological involvement. Our findings provide a transcriptomic insight into the systemic immunity associated with AMD.

Electronic supplementary material

The online version of this article (10.1186/s12979-019-0160-0) contains supplementary material, which is available to authorized users.

Treatment failure in neovascular age-related macular degeneration is associated with a complex chemokine receptor profile

Objective

To investigate if chemokine expression patterns on leucocyte subsets influence the short-term anatomical treatment response of intravitreal antivascular endothelial growth factor therapy against neovascular age-related macular degeneration (AMD).

Methods and analysis

This study was conducted as a prospective observational cohort study of 79 patients with neovascular AMD. We used optical coherence tomography to quantify central retinal thickness (CRT) and to evaluate the presence of intraretinal and subretinal fluids in treatment-naive patients at baseline and after loading dose. Anatomical response was categorised into either good responders (complete regression of fluid or a reduction of >75% in CRT), partial responders (reduction of 0%-75% in CRT) or non-responders (increase of CRT). Expression levels of chemokine receptors (CCR1, CCR2, CCR3, CCR5, CXCR3 and CX3CR1) were measured on leucocyte subsets (monocytes, CD4 +T cells, and CD8 +T cells) using flow cytometry. Finally, we explored potential correlation patterns of chemokine expression between the leucocyte subsets using group-specific correlation networks.

Results

Non-responders had higher CCR1 expression on monocytes (p=0.016) and lower CCR3 expression on CD8+ T cells (p=0.037). Correlation network analyses of chemokine receptor expression patterns on leucocyte subsets revealed intergroup differences.

Conclusion

Short-term anatomical treatment response in neovascular AMD varies according to the leucocyte subset chemokine expression pattern, which confirms that immune dysfunction is a complex issue in AMD. Our results suggest that focusing on chemokines may be a relevant approach towards personalised treatment in neovascular AMD.

Polypoidal choroidal vasculopathy: a comprehensive clinical update

Polypoidal choroidal vasculopathy as a disease is yet to be comprehended completely. The clinical features consisting of huge serosanguineous retinal pigment epithelial and neurosensory layer detachments, although unique may closely mimick neovascular age-related macular degeneration and other counterparts. The investigative modalities starting from indocyanine angiography to optical coherence tomography angiography provide diagnostic challenges. The management strategies based on the available therapies are plenty and not vivid. A detailed review with clarifying images has been compiled with an aim to help the readers in getting a better understanding of the disease.

Plasma markers of chronic low-grade inflammation in polypoidal choroidal vasculopathy and neovascular age-related macular degeneration

PURPOSE

Ageing is the strongest predictor of neovascular age-related macular degeneration (AMD), where neuroinflammation is known to play a major role. Less is known about polypoidal choroidal vasculopathy (PCV), which is an important differential diagnosis to neovascular AMD. Here, we report plasma markers of inflammation with age (inflammaging) in patients with PCV, patients with neovascular AMD and a healthy age-matched control group.

METHODS

We isolated plasma from fresh venous blood obtained from participants (n = 90) with either PCV, neovascular AMD, or healthy maculae. Interleukin(IL)-1β, IL-6, IL-8, IL-10 and tumour necrosis factor receptor 2 (TNF-R2) were measured using U-PLEX Human Assays. Routine plasma C-reactive protein (CRP) was measured using Dimension Vista 1500.

RESULTS

Patients with PCV had plasma levels of IL-1β, IL-6, IL-8, IL-10 and TNF-R2 similar to that in healthy controls. Patients with neovascular AMD had significantly higher plasma IL-1β, IL-6 and IL-10 than healthy controls, whereas no significant differences were observed for plasma IL-8 and TNF-R2. Differences between plasma IL-1β, IL-6 and IL-10 possessed a positive but weak ability in discriminating neovascular AMD from PCV. Both patients with PCV and patients with neovascular AMD had significantly higher levels of routine plasma CRP.

CONCLUSION

Patients with PCV differ from patients with neovascular AMD in terms of plasma inflammaging profile. Apart from increased CRP, no signs of inflammaging were observed in patients with PCV. In patients with neovascular AMD, we find a specific angiogenesis-twisted inflammaging profile.