Aging is not a disease: distinguishing age-related macular degeneration from aging

LONG-TERM REMISSION OF NEOVASCULAR AGE-RELATED MACULAR DEGENERATION WITH AS-NEEDED ANTI-VASCULAR ENDOTHELIAL GROWTH FACTOR THERAPY

PURPOSE

To determine the presenting characteristics of patients with neovascular age-related macular degeneration with long-term remission (LTR), which was defined as the absence of intraretinal/subretinal fluid, or hemorrhage, and absence of leakage on fluorescein angiography for longer than 6 months while on as-needed antivascular endothelial growth factor treatment.

METHODS

The presenting characteristics of patients with LTR were compared with a control group including 32 eyes of 28 age-, gender-, and ethnicity-matched patients who did not achieve LTR.

RESULTS

Seventy-four percent of patients in the LTR group had Type 1 choroidal neovascular membrane and 18.5% had retinal angiomatous proliferation. In the control group, 28 eyes had Type 1 choroidal neovascular membrane (87.5%), and none of the patients had retinal angiomatous proliferation; overall, there was a significant difference in lesion types between the 2 groups (P = 0.036). Eyes with LTR at presentation had significantly thinner subfoveal choroidal thickness (147 vs. 178 μm, P = 0.04). There was more intraretinal fluid and less subretinal fluid at the presentation in the remission group (59.3% intraretinal fluid and 11.1% subretinal fluid) compared with the control group (28.1% intraretinal fluid and 34.4% subretinal fluid, P = 0.03).

CONCLUSION

The presence of retinal angiomatous proliferation, thinner choroidal thickness, more intraretinal fluid, and less subretinal fluid at presentation were associated with LTR in patients receiving as-needed treatment for age-related macular degeneration.

Age-related pro-inflammatory and pro-angiogenic changes in human aqueous humor

AIM

To reveal age-related aqueous cytokine changes in human aqueous humor.

METHODS

Aqueous humor was collected from 12 young children (3-6.5 years old) and 71 healthy adults (22-106 years old) with cataract but without other systemic or ocular disorders. Levels of 22 cytokines, chemokines and vascular endothelial growth factor (VEGF) were measured and analyzed.

RESULTS

The following proteins showed significant increase from childhood to adult: interferon-gamma (IFN-γ), interleukin (IL)-13, IL-6, IL-12(p70), IL-10, CCL2, CCL3, CCL4, CXCL8, CXCL9, CXCL10, IFN-α2 and VEGF (all P<0.05). IFN-γ, IL-13, IL-12(p70), IL-10, CCL3, CXCL9 and VEGF also showed moderate strength age-related increase in the adult group (r>0.5). The strength of correlation between aging and CCL4 were fair (r=0.398). The concentrations of IL-2, IL-4, IL-5, IL-1β and TNF-α were low in both groups.

CONCLUSION

From childhood to adult, the immunological milieu of the anterior chamber become more pro-inflammatory and pro-angiogenic. Such changes may represent the parainflammation state of the human eye.

Evidence for the activation of pyroptotic and apoptotic pathways in RPE cells associated with NLRP3 inflammasome in the rodent eye

Background

Age-related macular degeneration (AMD) is a devastating eye disease causing irreversible vision loss in the elderly. Retinal pigment epithelium (RPE), the primary cell type that is afflicted in AMD, undergoes programmed cell death in the late stages of the disease. However, the exact mechanisms for RPE degeneration in AMD are still unresolved. The prevailing theories consider that each cell death pathway works independently and without regulation of each other. Building upon our previous work in which we induced a short burst of inflammasome activity in vivo, we now investigate the effects of prolonged inflammasome activity on RPE cell death mechanisms in rats.

Methods

Long-Evans rats received three intravitreal injections of amyloid beta (Aβ), once every 4 days, and were sacrificed at day 14. The vitreous samples were collected to assess the levels of secreted cytokines. The inflammasome activity was evaluated by both immunohistochemistry and western blot. The types of RPE cell death mechanisms were determined using specific cell death markers and morphological characterizations.

Results

We found robust inflammasome activation evident by enhanced caspase-1 immunoreactivity, augmented NF-κB nuclear translocalization, increased IL-1β vitreal secretion, and IL-18 protein levels. Moreover, we observed elevated proteolytic cleavage of caspase-3 and gasdermin D, markers for apoptosis and pyroptosis, respectively, in RPE-choroid tissues. There was also a significant reduction in the anti-apoptotic factor, X-linked inhibitor of apoptosis protein, consistent with the overall changes of RPE cells. Morphological analysis showed phenotypic characteristics of pyroptosis including RPE cell swelling.

Conclusions

Our data suggest that two cell death pathways, pyroptosis and apoptosis, were activated in RPE cells after exposure to prolonged inflammasome activation, induced by a drusen component, Aβ. The involvement of two distinct cell death pathways in RPE sheds light on the potential interplay between these pathways and provides insights on the future development of therapeutic strategies for AMD.

Electronic supplementary material

The online version of this article (10.1186/s12974-018-1062-3) contains supplementary material, which is available to authorized users.

Change in choroidal thickness after intravitreal injection for treatment of neovascular age-related macular degeneration: Ranibizumab versus aflibercept

PURPOSE

To compare the changes in subfoveal choroidal thickness after intravitreal ranibizumab or aflibercept injections for neovascular age-related macular degeneration (nAMD).

METHODS

In this retrospective study, 28 eyes with nAMD treated with 3 consecutive monthly injections of ranibizumab (IVR) and 24 eyes with nAMD treated with 3 consecutive monthly injections of aflibercept (IVA) between September 2012 and June 2016 were reviewed. The follow-up time was 6 months. Changes in two groups' best-corrected visual acuity (BCVA) and subfoveal choroidal thickness by using enhanced depth imaging optical coherence tomography at 1st, 3rd and 6th months were recorded and compared.

RESULTS

Choroidal thickness decreased significantly in eyes treated with IVR (P=0.015, 0.01 and 0.01, respectively) or IVA (P=0.001, 0.001 and ˂0.001, respectively) at 1, 3 and 6 months examination but IVA treated eyes presented a significantly further reduction in choroidal thickness when compared with ranibizumab (P=0.03, 0,04 and 0.03, respectively). There was no significant difference between aflibercept and ranibizumab group when change in BCVA from baseline compared at 1, 3 and 6th months (P=0.54, 0.06 and 0.37, respectively). There was no correlation between change in choroidal thickness and the BCVA outcomes in either group.

CONCLUSIONS

Subfoveal choroidal thickness decreased significantly after both of IVR and IVA injections in patients with nAMD. In conclusion, intravitreal injections of ranibizumab or aflibercept affect not only neovascular lesion but also the underlying choroid.

Effect of aging and lifestyle on photoreceptors and retinal pigment epithelium: cross-sectional study in a healthy Danish population

Photoreceptors and their supporting retinal pigment epithelium constitute the key functional parts of the retina. Here, a study was undertaken to show how aging and lifestyle factors affect the photoreceptor layer and the retinal pigment epithelium and Bruch's membrane complex (RPE-BM) in vivo in a healthy Danish population using spectral-domain optical coherence tomography. This was a cross-sectional study of healthy humans aged ≥50 years. All participants were interviewed for medical history and lifestyle factors. Maculae of all participants were scanned using spectral-domain optical coherence tomography. The thickness of the photoreceptor layer and the RPE-BM was measured on one eye from each participant. In 150 eyes of 150 participants, it was found that aging was associated with a decrease in the thickness of the photoreceptor layer (-0.143 μm/year, P = 0.031) and an increase in the thickness of the RPE-BM layer (0.100 μm/year, P = 0.029) at the foveal minimum. Regarding lifestyle factors, alcohol intake or BMI were not associated with any significant trend, but physical inactivity and smoking had effects on the photoreceptor layer (decreased thickness) and the RPE-BM layer (increased thickness) indicating an accelerated aging process of the macula. Taken together, aging affects photoreceptors and the RPE-BM, and these aging trends are accelerated in smokers and the physically inactive.

New Treatment Modalities for Geographic Atrophy

Age‑related macular degeneration (AMD) is a significant cause of global visual morbidity and is projected to affect 288 million people by the year 2040. The advent of treatment with anti‒vascular endothelial growth factor (anti‑VEGF) drugs has revolutionized the treatment of neovascular AMD (nAMD) but there have been no similar breakthroughs for the treatment of geographic atrophy (GA) to retard its progression. The advancements in imaging and new understanding of disease mechanisms, based on molecular and genetic models, have paved the way for the development of novel experimental treatment options for GA that aim to cater to a thus far largely unmet need. This review paper focuses on the recent clinical trials of new treatment options for slowing GA progression rates with emphasis on the agents that are currently undergoing, or have already undergone, significant clinical trial testing. Several new groups of drugs, including those targeting the complement cascade and agents considered as neuroprotective, have shown some promising results and could potentially pave the way forward in the treatment of this devastating disease.

The reason for the amelioration of N-methyl-N-nitrosourea-induced retinitis pigmentosa in rats by hydrogen-rich saline

AIM

To investigate the effects of hydrogen-rich saline (HRS) on microglia activation and Sirtuin type 1 (Sirt1) in rats with N-methyl-N-nitrosourea (MNU)-induced retinitis pigmentosa (RP).

METHODS

Rats were divided into norm (N) group, model (M) group and HRS (H) group. Rats in M and H groups were given saline and HRS respectively prior to and after administration of MNU. At one day (d1) and d3 afterwards, electroretinogram and histological examination were performed to confirm the effects of HRS on retinal function and structure of MNU-induced RP. Immunofluorescence staining of anti-ionized calcium-binding adapter molecule 1 (Iba1), a maker of microglia cells, was performed, with quantitative real-time polymerase chain reaction (qRT-PCR) for its mRNA quantification. Moreover, Sirt1 mRNA and protein expression in the retinas were detected by Western blot and qRT-PCR.

RESULTS

HRS preserved the retinal function and mitigated the reduction of photoreceptor degeneration in MNU-treated retinas. The presence of microglia cells was somewhat more obvious in H group than that in M group at d1. HRS suppressed the further activation of microglia cells, with the number of microglia cells less than that of M group at d3. Results of qRT-PCR of Iba1 were consistent with those of immunofluorescence staining, with the mRNA expression of Iba1 in H group more intensive than that of M group at d1 (P<0.05), while less than that of M group at d3 (P<0.05). Furthermore, the Sirt1 mRNA and protein expression decreased after MNU administration, while HRS mitigated the MNU-induced downregulation of Sirt1.

CONCLUSION

HRS can effectively keep microglia activation induced by MNU to an appropriate extent, while upregulate Sirt1 in MNU-induced RP.

Age-Related Macular Degeneration: A Connection between Human Herpes Virus-6A-Induced CD46 Downregulation and Complement Activation?

Viruses are able to interfere with the immune system by docking to receptors on host cells that are important for proper functioning of the immune system. A well-known example is the human immunodeficiency virus that uses CD4 cell surface molecules to enter host lymphocytes and thereby deleteriously destroying the helper cell population of the immune system. A more complicated mechanism is seen in multiple sclerosis (MS) where human herpes virus-6A (HHV-6A) infects astrocytes by docking to the CD46 surface receptor. Such HHV-6A infection in the brain of MS patients has recently been postulated to enable Epstein-Barr virus (EBV) to transform latently infected B-lymphocytes in brain lesions leading to the well-known phenomenon of oligoclonal immunoglobulin production that is widely used in the diagnosis of MS. The cellular immune response to HHV-6A and EBV is one part of the pathogenic mechanisms in MS. A more subtle pathogenic mechanism can be seen in the downregulation of CD46 on astrocytes by the infecting HHV-6A. Since CD46 is central in regulating the complement system, a lack of CD46 can lead to hyperactivation of the complement system. In fact, activation of the complement system in brain lesions is a well-known pathogenic mechanism in MS. In this review, it is postulated that a similar mechanism is central in the development of age-related macular degeneration (AMD). One of the earliest changes in the retina of AMD patients is the loss of CD46 expression in the retinal pigment epithelial (RPE) cells in the course of geographic atrophy. Furthermore, CD46 deficient mice spontaneously develop dry-type AMD-like changes in their retina. It is also well known that certain genetic polymorphisms in the complement-inhibiting pathways correlate with higher risks of AMD development. The tenet is that HHV-6A infection of the retina leads to downregulation of CD46 and consequently to hyperactivation of the complement system in the eyes of susceptible individuals.

THE PATHOPHYSIOLOGY OF GEOGRAPHIC ATROPHY SECONDARY TO AGE-RELATED MACULAR DEGENERATION AND THE COMPLEMENT PATHWAY AS A THERAPEUTIC TARGET

Geographic atrophy is an advanced form of age-related macular degeneration that can significantly impact visual function, but has no approved treatment. This review focuses on the pathophysiology of geographic atrophy, particularly the role of complement cascade dysregulation and emerging therapies targeting the complement cascade.

Purpose:

Geographic atrophy (GA) is an advanced, vision-threatening form of age-related macular degeneration (AMD) affecting approximately five million individuals worldwide. To date, there are no approved therapeutics for GA treatment; however, several are in clinical trials. This review focuses on the pathophysiology of GA, particularly the role of complement cascade dysregulation and emerging therapies targeting the complement cascade.

Methods:

Primary literature search on PubMed for GA, complement cascade in age-related macular degeneration. ClinicalTrials.gov was searched for natural history studies in GA and clinical trials of drugs targeting the complement cascade for GA.

Results:

Cumulative damage to the retina by aging, environmental stress, and other factors triggers inflammation via multiple pathways, including the complement cascade. When regulatory components in these pathways are compromised, as with several GA-linked genetic risk factors in the complement cascade, chronic inflammation can ultimately lead to the retinal cell death characteristic of GA. Complement inhibition has been identified as a key candidate for therapeutic intervention, and drugs targeting the complement pathway are currently in clinical trials.

Conclusion:

The complement cascade is a strategic target for GA therapy. Further research, including on natural history and genetics, is crucial to expand the understanding of GA pathophysiology and identify effective therapeutic targets.

Altered activation state of circulating neutrophils in patients with neovascular age-related macular degeneration

Background

Neutrophil dysfunction plays a key role in the development of diseases characterized by inflammation and angiogenesis. Here, we studied the systemic expression of neutrophil markers reflecting activation, adhesion, and resolution of inflammation in patients with neovascular age-related macular degeneration (AMD).

Results

This was a prospective case-control study of patients with neovascular AMD and age-matched healthy control individuals. Patients were recruited from an outpatient program, and control individuals were recruited amongst patients’ relatives. Current smokers and individuals with either active immune-disease or ongoing cancer were not included, as these factors are known to affect neutrophil function. Fresh-drawn venous blood was processed for flow cytometric analysis of neutrophil markers. We determined percentages of positive cells and compared expression levels using fluorescence intensity measures. We found conditional differences on marker expression between patients with neovascular AMD (n = 29) and controls (n = 28): no differences were found when looking broadly, but several differences emerged when focusing on non-smokers. Here, patients with neovascular AMD had increased expression of the activity marker cluster of differentiation (CD) 66b (P = 0.003; Mann-Whitney U test), decreased expression of adhesion marker CD162 (P = 0.044; Mann-Whitney U test), and lower expression of the resolution of inflammation marker C-X-C chemokine receptor 2 (P = 0.044; Mann-Whitney U test).

Conclusions

We present novel evidence suggesting that the activity of circulating neutrophils, sensitive to smoking, may differ in patients with neovascular AMD.

Scaffolds for retinal pigment epithelial cell transplantation in age-related macular degeneration

In several retinal degenerative diseases, including age-related macular degeneration, the retinal pigment epithelium, a highly functionalized cell monolayer, becomes dysfunctional. These retinal diseases are marked by early retinal pigment epithelium dysfunction reducing its ability to maintain a healthy retina, hence making the retinal pigment epithelium an attractive target for treatment. Cell therapies, including bolus cell injections, have been investigated with mixed results. Since bolus cell injection does not promote the proper monolayer architecture, scaffolds seeded with retinal pigment epithelium cells and then implanted have been increasingly investigated. Such cell-seeded scaffolds address both the dysfunction of the retinal pigment epithelium cells and age-related retinal changes that inhibit the efficacy of cell-only therapies. Currently, several groups are investigating retinal therapies using seeded cells from a number of cell sources on a variety of scaffolds, such as degradable, non-degradable, natural, and artificial substrates. This review describes the variety of scaffolds that have been developed for the implantation of retinal pigment epithelium cells.

NADPH Oxidase Contributes to Photoreceptor Degeneration in Constitutively Active RAC1 Mice

Purpose

The active form of small GTPase RAC1 is required for activation of NADPH oxidase (NOX), which in turn generates reactive oxygen species (ROS) in nonphagocytic cells. We explored whether NOX-induced oxidative stress contributes to rod degeneration in retinas expressing constitutively active (CA) RAC1.

Methods

Transgenic (Tg)–CA-RAC1 mice were given apocynin (10 mg/kg, intraperitoneal), a NOX inhibitor, or vehicle daily for up to 13 weeks. Superoxide production and oxidative damage were assessed by dihydroethidium staining and by protein carbonyls and malondialdehyde levels, respectively. Outer nuclear layer (ONL) cells were counted and electroretinogram (ERG) amplitudes measured in Tg-CA-RAC1 mice. Outer nuclear layer cells were counted in wild-type (WT) mice after transfer of CA-Rac1 gene by subretinal injection of AAV8-pOpsin-CA Rac1-GFP.

Results

Transgenic-CA-RAC1 retinas had significantly fewer photoreceptor cells and more apoptotic ONL cells than WT controls from postnatal week (Pw) 3 to Pw13. Superoxide accumulation and protein and lipid oxidation were increased in Tg-CA-RAC1 retinas and were reduced in mice treated with apocynin. Apocynin reduced the loss of photoreceptors and increased the rod ERG a- and b-wave amplitudes when compared with vehicle-injected transgenic controls. Photoreceptor loss was also observed in regions of adult WT retina transduced with AAV8-pOpsin-CA Rac1-GFP but not in neighboring regions that were not transduced or in AAV8-pOpsin-GFP–transduced retinas.

Conclusions

Constitutively active RAC1 promotes photoreceptor cell death by oxidative damage that occurs, at least partially, through NOX-induced ROS. Reactive oxygen species are likely involved in multiple forms of retinal degenerations, and our results support investigating RAC1 inhibition as a therapeutic approach that targets this disease pathway.

Concerted regulation of retinal pigment epithelium basement membrane and barrier function by angiocrine factors

The outer blood-retina barrier is established through the coordinated terminal maturation of the retinal pigment epithelium (RPE), fenestrated choroid endothelial cells (ECs) and Bruch's membrane, a highly organized basement membrane that lies between both cell types. Here we study the contribution of choroid ECs to this process by comparing their gene expression profile before (P5) and after (P30) the critical postnatal period when mice acquire mature visual function. Transcriptome analyses show that expression of extracellular matrix-related genes changes dramatically over this period. Co-culture experiments support the existence of a novel regulatory pathway: ECs secrete factors that remodel RPE basement membrane, and integrin receptors sense these changes triggering Rho GTPase signals that modulate RPE tight junctions and enhance RPE barrier function. We anticipate our results will spawn a search for additional roles of choroid ECs in RPE physiology and disease.

Cell-based therapeutic strategies for replacement and preservation in retinal degenerative diseases

Cell-based therapeutics offer diverse options for treating retinal degenerative diseases, such as age-related macular degeneration (AMD) and retinitis pigmentosa (RP). AMD is characterized by both genetic and environmental risks factors, whereas RP is mainly a monogenic disorder. Though treatments exist for some patients with neovascular AMD, a majority of retinal degenerative patients have no effective therapeutics, thus indicating a need for universal therapies to target diverse patient populations. Two main cell-based mechanistic approaches are being tested in clinical trials. Replacement therapies utilize cell-derived retinal pigment epithelial (RPE) cells to supplant lost or defective host RPE cells. These cells are similar in morphology and function to native RPE cells and can potentially supplant the responsibilities of RPE in vivo. Preservation therapies utilize supportive cells to aid in visual function and photoreceptor preservation partially by neurotrophic mechanisms. The goal of preservation strategies is to halt or slow the progression of disease and maintain remaining visual function. A number of clinical trials are testing the safety of replacement and preservation cell therapies in patients; however, measures of efficacy will need to be further evaluated. In addition, a number of prevailing concerns with regards to the immune-related response, longevity, and functionality of the grafted cells will need to be addressed in future trials. This review will summarize the current status of cell-based preclinical and clinical studies with a focus on replacement and preservation strategies and the obstacles that remain regarding these types of treatments.

Macular thickness in healthy eyes of adults (N = 4508) and relation to sex, age and refraction: the Tromsø Eye Study (2007-2008)

Purpose

To provide sex‐stratified normative data on retinal thickness and study the relationship with sex, age and refractive status.

Methods

Population‐based study including 2617 women and 1891 men, aged 38–87 (mean 61 ± 8) years, without diabetes, glaucoma and retinal diseases, and spherical equivalent refraction (SER) within ±6 dioptres. Retinal thickness was measured with optical coherence tomography (spectral domain Cirrus HD‐OCT).

Results

Women had thinner retina than men. Retinal thickness was significantly associated with refraction, where mean change in retinal thickness per 1 D increase in SER was −1.3 (0.2) μm in the fovea, 0.7 (0.1) μm in the pericentral ring and 1.4 (0.1) μm in the peripheral ring. In the fovea, there was a non‐monotonic curved relationship between retinal thickness and age in both sexes with a maximum at about 60 years (p < 0.001). In the pericentral ring, the mean reduction in retinal thickness per 10‐year increase was 2.7 (0.3) μm in women and 4.0 (0.4) μm in men and corresponding results in the peripheral ring were 2.3 (0.3) μm in women and 2.6 (0.4) μm in men. In both regions, there was evidence for a nonlinear pattern with an increased rate of change with higher age. There was a significant interaction between sex and age for retinal thickness of the pericentral ring (p = 0.041).

Conclusion

Women had thinner retina than men, and thickness varied with refractive status. Retinal thickness was associated with age in all macular regions, and the rate of change in retinal thickness varied at different ages.

Effect of Epiretinal Membranes on Antivascular Endothelial Growth Factor Treatment for Neovascular Age-Related Macular Degeneration

PURPOSE

To evaluate the effect of epiretinal membranes (ERMs), detected with spectral-domain optical coherence tomography (SD-OCT), on the outcome of antivascular endothelial growth factor (VEGF) treatment for neovascular age-related macular degeneration (nAMD).

METHODS

A total of 434 eyes with treatment-naive nAMD were retrospectively included and analyzed. All patients were administered an initial series of 3 monthly loading injections of ranibizumab or aflibercept, followed by further injections as required. The visual and anatomical outcomes were compared between the eyes with ERMs and those without. Features of ERMs at baseline assessed with SD-OCT were evaluated and correlated with visual outcomes.

RESULTS

Sixty-eight eyes (15.7%) with nAMD presented ERMs at baseline. The mean best-corrected visual acuity (BCVA) of these eyes, expressed as the logarithm of the minimum angle of resolution, improved from 0.75 ± 0.48 (Snellen equivalent: 20/112) to 0.59 ± 0.44 (20/77) after 12 months of treatment (P = 0.021). Central foveal thickness also decreased from 381 ± 191 μm to 294 ± 167 μm (P < 0.001). Compared to the eyes without ERMs (366 eyes), the eyes with ERMs had a significantly thicker central fovea after treatment (P = 0.020). However, the intergroup differences in BCVA improvement were not significant. No significant association was found between visual outcome after treatment and ERM features on OCT at baseline.

CONCLUSIONS

In eyes with nAMD, ERMs were infrequent. Central foveal thickness was significantly greater after anti-VEGF treatment in eyes with nAMD and ERMs. However, the presence of ERMs in eyes with nAMD did not affect visual outcome.

Can innate and autoimmune reactivity forecast early and advance stages of age-related macular degeneration?

Age-related macular degeneration (AMD) is a major cause of central vision loss in persons over 55years of age in developed countries. AMD is a complex disease in which genetic, environmental and inflammatory factors influence its onset and progression. Elevation in serum anti-retinal autoantibodies, plasma and local activation of complement proteins of the alternative pathway, and increase in secretion of proinflammatory cytokines have been seen over the course of disease. Genetic studies of AMD patients confirmed that genetic variants affecting the alternative complement pathway have a major influence on AMD risk. Because the heterogeneity of this disease, there is no sufficient strategy to identify the disease onset and progression sole based eye examination, thus identification of reliable serological biomarkers for diagnosis, prognosis and response to treatment by sampling patient's blood is necessary. This review provides an outline of the current knowledge on possible serological (autoantibodies, complement factors, cytokines, chemokines) and related genetic biomarkers relevant to the pathology of AMD, and discusses their application for prediction of disease activity and prognosis in AMD.

Contributions of age-related alterations of the retinal pigment epithelium and of glia to the AMD-like pathology in OXYS rats

Age-related macular degeneration (AMD) is a major cause of blindness in developed countries, and the molecular pathogenesis of early events of AMD is poorly understood. It is known that age-related alterations of retinal pigment epithelium (RPE) cells and of glial reactivity are early hallmarks of AMD. Here we evaluated contributions of the age-related alterations of the RPE and of glia to the development of AMD-like retinopathy in OXYS rats. We showed that destructive alterations in RPE cells are a primary change during the development of retinopathy in OXYS rats. Furthermore, a defect of retinal maturation and decreased immune function at the preclinical stage of retinopathy were observed in OXYS rats in addition to the impairment of RPE cell proliferation and of their capacity for division. At the active stage of the disease, the atrophic alterations increased, and reactive gliosis was observed when disease progressed, but immune function stayed weakened. Unexpectedly, we did not observe migration of microglia and macrophages into the photoreceptor layer. These results and the wide spectrum of age-related retinal alterations in humans as well as individual differences in the risk of AMD may be attributed to genetic factors and to differences in the underlying molecular events.

Mesopic Pelli-Robson contrast sensitivity and MP-1 microperimetry in healthy ageing and age-related macular degeneration

PURPOSE

To determine whether decreasing illumination of the Pelli-Robson contrast sensitivity (CS) chart and MP-1 microperimeter to low mesopic conditions is more sensitive to vision changes occurring with healthy ageing and in early and intermediate age-related macular degeneration (AMD) and whether these mesopic tests can differentiate visual function between healthy older participants with and without AMD risk genotypes.

METHODS

Retinal sensitivity was measured in 98 healthy participants (19-85 years) and 21 AMD (AREDS Grade 2/3) patients (73.9 ± 6.5 years) using the Pelli-Robson CS chart and MP-1 microperimeter under low mesopic and standard illumination. The effect of ageing and AMD on retinal sensitivity was estimated using regression analysis. Healthy older participants (>50 years; n = 24) were genotyped for AMD risk genes CFH and/or ARMS2 and retinal sensitivity was compared between genotypes.

RESULTS

With healthy ageing, photopic and mesopic Pelli-Robson CS showed a similar decline (-0.004 log CS/year). In AMD, photopic CS showed a similar decline to healthy ageing (-0.004 log CS/year) while mesopic CS was significantly reduced (-0.007 log CS/year). Both standard and low mesopic microperimetry showed a significant decline (-0.51 and -0.73% contrast/year) with healthy ageing and greater decline (-0.73 and -0.99% contrast/year) with AMD onset. Pelli-Robson CS and microperimetry sensitivity did not differ between AMD risk genotypes in healthy participants.

CONCLUSIONS

Mesopic Pelli-Robson CS detects functional deficits before photopic CS in early and intermediate AMD that can be differentiated from ageing. This test can be easily administered in clinical practice and may provide a means for early detection of retinal dysfunction.

Light-induced retinal damage using different light sources, protocols and rat strains reveals LED phototoxicity

To save energy, the European directives from the Eco-design of Energy Using Products (2005/32/CE) have recommended the replacement of incandescent lamps by more economic devices such as Light Emitting Diodes (LEDs). However, the emission spectrum of these devices is enriched in blue radiations, known to be potentially dangerous to the retina. Recent studies showed that light exposure contributes to the onset of early stages of age-related macular degeneration (AMD). Here, we investigate, in albinos and pigmented rats, the effects of different exposure protocols. Twenty-four hours exposure at high luminance was compared to a cyclic (dark/light) exposure at domestic levels for 1week and 1month, using different LEDs (Cold-white, blue and green), as well as fluorocompact bulbs and fluorescent tubes. The data suggest that the blue component of the white-LED may cause retinal toxicity at occupational domestic illuminance and not only in extreme experimental conditions, as previously reported. It is important to note that the current regulations and standards have been established on the basis of acute light exposure and do not take into account the effects of repeated exposure.

Persistent inflammatory state after photoreceptor loss in an animal model of retinal degeneration

Microglia act as the resident immune cells of the central nervous system, including the retina. In response to damaging stimuli microglia adopt an activated state, which can progress into a phagocytic phenotype and play a potentially harmful role by eliciting the expression and release of pro-inflammatory cytokines. The aim of the present study was to assess longitudinal changes in microglia during retinal degeneration in the homozygous P23H rat, a model of dominant retinitis pigmentosa. Microglial phenotypes, morphology and density were analyzed by immunohistochemistry, flow cytometry, and cytokine antibody array. In addition, we performed electroretinograms to evaluate the retinal response. In the P23H retina, sclera, choroid and ciliary body, inflammatory cells increased in number compared with the control at all ages analyzed. As the rats became older, a higher number of amoeboid MHC-II(+) cells were observed in the P23H retina, which correlated with an increase in the expression of pro-inflammatory cytokines. These findings suggest that, in the P23H model, retinal neuroinflammation persists throughout the rat's life span even after photoreceptor depletion. Therefore, the inclusion of anti-inflammatory drugs at advanced stages of the neurodegenerative process may provide better retinal fitness so the remaining cells could still be used as targets of cellular or gene therapies.

Macular thickness and volume in the elderly: A systematic review

Ageing leads to a number of changes in the body including the macula. Detailed imaging using optical coherence tomography have enabled in vivo studies of how macula changes with age. Here we systematically review 49 studies (9115 participants and 11,577 eyes) to provide an overview of how ageing manifests in the macula of the elderly focusing on clinical relevant measures that are thicknesses and volumes of different macular areas. Ageing seems to increase center point foveal thickness. Ageing does not seem to change the center subfield thickness significantly. Ageing decreases the inner and outer macular thickness, and the overall macular thickness and volume. Studies find that specific retinal layers at specific locations seem to be the contributor to these changes. These findings confirm that age-related changes suggested in histological studies are measurable in vivo on thickness and volume and differ depending on location. Studies are needed to explore reasons for the large variance in measurements and how ageing by itself contributes to development of macular disease.

Neurovascular cross talk in diabetic retinopathy: Pathophysiological roles and therapeutic implications

Diabetic retinopathy (DR) is the leading cause of blindness in the working-age population in developed countries, and its prevalence will increase as the global incidence of diabetes grows exponentially. DR begins with an early nonproliferative stage in which retinal blood vessels and neurons degenerate as a consequence of chronic hyperglycemia, resulting in vasoregression and persistent retinal ischemia, metabolic disequilibrium, and inflammation. This is conducive to overcompensatory pathological neovascularization associated with advanced proliferative DR. Although DR is considered a microvascular complication, the retinal microvasculature is intimately associated with and governed by neurons and glia; neurodegeneration, neuroinflammation, and dysregulation of neurovascular cross talk are responsible in part for vascular abnormalities in both early nonproliferative DR and advanced proliferative DR. Neuronal activity directly regulates microvascular dilation and blood flow in the process of neurovascular coupling. Retinal neurons also secrete guidance cues in response to injury, ischemia, or metabolic stress that may either promote or suppress vascular outgrowth, either alleviating or exacerbating DR, contingent on the stage of disease and retinal microenvironment. Neurodegeneration, impaired neurovascular coupling, and dysregulation of neuronal guidance cues are key events in the pathogenesis of DR, and correcting these events may prevent or delay development of advanced DR. The review discusses the mechanisms of neurovascular cross talk and its dysregulation in DR, and their potential therapeutic implications.

Methods for culturing retinal pigment epithelial cells: a review of current protocols and future recommendations

The retinal pigment epithelium is an important part of the vertebrate eye, particularly in studying the causes and possible treatment of age-related macular degeneration. The retinal pigment epithelium is difficult to access in vivo due to its location at the back of the eye, making experimentation with age-related macular degeneration treatments problematic. An alternative to in vivo experimentation is cultivating the retinal pigment epithelium in vitro, a practice that has been going on since the 1970s, providing a wide range of retinal pigment epithelial culture protocols, each producing cells and tissue of varying degrees of similarity to natural retinal pigment epithelium. The purpose of this review is to provide researchers with a ready list of retinal pigment epithelial protocols, their effects on cultured tissue, and their specific possible applications. Protocols using human and animal retinal pigment epithelium cells, derived from tissue or cell lines, are discussed, and recommendations for future researchers included.

Age-Related Macular Degeneration: Genetics and Biology

Age-related macular degeneration (AMD), widely prevalent across the globe, is a major stakeholder among adult visual morbidity and blindness, not only in the Western world but also in Asia. Several risk factors have been identified, including critical genetic factors, which were never imagined 2 decades ago. The etiopathogenesis is emerging to demonstrate that immune and complement-related inflammation pathway members chronically exposed to environmental insults could justifiably influence disease morbidity and treatment outcomes. Approximately half a dozen physiological and biochemical cascades are disrupted in the AMD disease genesis, eventually leading to the distortion and disruption of the subretinal space, subretinal pigment epithelium, and Bruch membrane, thus setting off chaos and disorder for signs and symptoms to manifest. Approximately 3 dozen genetic factors have so far been identified, including the recent ones, through powerful genomic technologies and large robust sample sizes. The noteworthy genetic variants (common and rare) are complement factor H, complement factor H-related genes 1 to 5, C3, C9, ARMS2/HTRA1, vascular endothelial growth factor A, vascular endothelial growth factor receptor 2/KDR, and rare variants (show causal link) such as TIMP3, fibrillin, COL4A3, MMP19, and MMP9. Despite the enormous amount of scientific information generated over the years, diagnostic genetic or biomarker tests are still not available for clinicians to understand the natural course of the disease and its management in a patient. However, further research in the field should reduce this gap not only by aiding the clinician but also through the possibilities of clinical intervention with complement pathway-related inhibitors entering preclinical and clinical trials in the near future.

Retinal pigment epithelial cell multinucleation in the aging eye - a mechanism to repair damage and maintain homoeostasis

Retinal pigment epithelial (RPE) cells are central to retinal health and homoeostasis. Dysfunction or death of RPE cells underlies many age-related retinal degenerative disorders particularly age-related macular degeneration. During aging RPE cells decline in number, suggesting an age-dependent cell loss. RPE cells are considered to be postmitotic, and how they repair damage during aging remains poorly defined. We show that RPE cells increase in size and become multinucleate during aging in C57BL/6J mice. Multinucleation appeared not to be due to cell fusion, but to incomplete cell division, that is failure of cytokinesis. Interestingly, the phagocytic activity of multinucleate RPE cells was not different from that of mononuclear RPE cells. Furthermore, exposure of RPE cells in vitro to photoreceptor outer segment (POS), particularly oxidized POS, dose-dependently promoted multinucleation and suppressed cell proliferation. Both failure of cytokinesis and suppression of proliferation required contact with POS. Exposure to POS also induced reactive oxygen species and DNA oxidation in RPE cells. We propose that RPE cells have the potential to proliferate in vivo and to repair defects in the monolayer. We further propose that the conventionally accepted 'postmitotic' status of RPE cells is due to a modified form of contact inhibition mediated by POS and that RPE cells are released from this state when contact with POS is lost. This is seen in long-standing rhegmatogenous retinal detachment as overtly proliferating RPE cells (proliferative vitreoretinopathy) and more subtly as multinucleation during normal aging. Age-related oxidative stress may promote failure of cytokinesis and multinucleation in RPE cells.

Risk factors and biomarkers of age-related macular degeneration

A biomarker can be a substance or structure measured in body parts, fluids or products that can affect or predict disease incidence. As age-related macular degeneration (AMD) is the leading cause of blindness in the developed world, much research and effort has been invested in the identification of different biomarkers to predict disease incidence, identify at risk individuals, elucidate causative pathophysiological etiologies, guide screening, monitoring and treatment parameters, and predict disease outcomes. To date, a host of genetic, environmental, proteomic, and cellular targets have been identified as both risk factors and potential biomarkers for AMD. Despite this, their use has been confined to research settings and has not yet crossed into the clinical arena. A greater understanding of these factors and their use as potential biomarkers for AMD can guide future research and clinical practice. This article will discuss known risk factors and novel, potential biomarkers of AMD in addition to their application in both academic and clinical settings.

Inflammation and its role in age-related macular degeneration

Inflammation is a cellular response to factors that challenge the homeostasis of cells and tissues. Cell-associated and soluble pattern-recognition receptors, e.g. Toll-like receptors, inflammasome receptors, and complement components initiate complex cellular cascades by recognizing or sensing different pathogen and damage-associated molecular patterns, respectively. Cytokines and chemokines represent alarm messages for leukocytes and once activated, these cells travel long distances to targeted inflamed tissues. Although it is a crucial survival mechanism, prolonged inflammation is detrimental and participates in numerous chronic age-related diseases. This article will review the onset of inflammation and link its functions to the pathogenesis of age-related macular degeneration (AMD), which is the leading cause of severe vision loss in aged individuals in the developed countries. In this progressive disease, degeneration of the retinal pigment epithelium (RPE) results in the death of photoreceptors, leading to a loss of central vision. The RPE is prone to oxidative stress, a factor that together with deteriorating functionality, e.g. decreased intracellular recycling and degradation due to attenuated heterophagy/autophagy, induces inflammation. In the early phases, accumulation of intracellular lipofuscin in the RPE and extracellular drusen between RPE cells and Bruch's membrane can be clinically detected. Subsequently, in dry (atrophic) AMD there is geographic atrophy with discrete areas of RPE loss whereas in the wet (exudative) form there is neovascularization penetrating from the choroid to retinal layers. Elevations in levels of local and systemic biomarkers indicate that chronic inflammation is involved in the pathogenesis of both disease forms.

The effects of VEGF-A-inhibitors aflibercept and ranibizumab on the ciliary body and iris of monkeys

PURPOSE

To investigate the effects of intravitreal ranibizumab (Lucentis®) and aflibercept (Eylea®) on the ciliary body and the iris of 12 cynomolgus monkeys with regard to the fenestrations of their blood vessels.

MATERIALS AND METHODS

Structural changes in the ciliary body and in the iris were investigated with light, fluorescent, and transmission electron microscopy (TEM). The latter was used to specifically quantify fenestrations of the endothelium of blood vessels after treatment with aflibercept and ranibizumab. Each of the two ciliary bodies treated with aflibercept and the two treated with ranibizumab and their controls were examined after 1 and 7 days respectively. Ophthalmological investigations including funduscopy and intraocular pressure measurements were also applied.

RESULTS

Ophthalmological investigations did not reveal any changes within the groups. Both drugs reduced the VEGF concentration in the ciliary body pigmented epithelium. The structure of the ciliary body was not influenced, while the posterior pigmented epithelium of the iris showed vacuoles after aflibercept treatment. Ranibizumab was mainly concentrated on the surface layer of the ciliary epithelium, in the blood vessel walls and the lumen of some of the blood vessels, and in the cells of the epithelium of the ciliary body. Aflibercept was more concentrated in the stroma and not in the cells of the epithelium, but as with ranibizumab, also in the blood vessel walls and some of their lumina, and again on the surface layer of the epithelium. Both aflibercept-and ranibizumab-treated eyes showed a decreased number of fenestrations of the capillaries in the ciliary body compared to the untreated controls. On day 1 and day 7, aflibercept had fewer fenestrations than the ranibizumab samples of the same day.

CONCLUSIONS

Both aflibercept and ranibizumab were found to reach the blood vessel walls of the ciliary body, and effectively reduced their fenestrations. Aflibercept might eliminate VEGF to a greater extent, possibly due to a higher elimination of fenestrations in a shorter time. Moreover, the vacuoles found in the iris need further research, in order to evaluate whether they carry a possible pathological potential.

Prolactin protects retinal pigment epithelium by inhibiting sirtuin 2-dependent cell death

The identification of pathways necessary for retinal pigment epithelium (RPE) function is fundamental to uncover therapies for blindness. Prolactin (PRL) receptors are expressed in the retina, but nothing is known about the role of PRL in RPE. Using the adult RPE 19 (ARPE-19) human cell line and mouse RPE, we identified the presence of PRL receptors and demonstrated that PRL is necessary for RPE cell survival via anti-apoptotic and antioxidant actions. PRL promotes the antioxidant capacity of ARPE-19 cells by reducing glutathione. It also blocks the hydrogen peroxide-induced increase in deacetylase sirtuin 2 (SIRT2) expression, which inhibits the TRPM2-mediated intracellular Ca(2+) rise associated with reduced survival under oxidant conditions. RPE from PRL receptor-null (prlr(-/-)) mice showed increased levels of oxidative stress, Sirt2 expression and apoptosis, effects that were exacerbated in animals with advancing age. These observations identify PRL as a regulator of RPE homeostasis.

NLRP3 Upregulation in Retinal Pigment Epithelium in Age-Related Macular Degeneration

Inflammation and oxidative stress are involved in age-related macular degeneration (AMD) and possibly associated with an activation of neuronal apoptosis inhibitor protein/class II transcription activator of the Major Histocompatibility Complex (MHC)/heterokaryon incompatibility/telomerase-associated protein 1, leucine-rich repeat or nucleotide-binding domain, leucine-rich repeat-containing family, and pyrin domain-containing 3 (NLRP3) inflammasome. In the present study, we used a translational approach to address this hypothesis. In patients with AMD, we observed increased mRNA levels of NLRP3, pro-interleukin-1 beta (IL-1β) and pro-IL-18 in AMD lesions of the retinal pigment epithelium (RPE) and photoreceptor. In vitro, a similar increase was evoked by oxidative stress or lipopolysaccharide (LPS) stimulation in the adult retinal pigment epithelium (ARPE-19) cell line, and the increase was reduced in siRNA transfected cells to knockdown NLRP3. Ultrastructural studies of ARPE-19 cells showed a swelling of the cytoplasm, mitochondrial damage, and occurrence of autophagosome-like structures. NLRP3 positive dots were detected within autophagosome-like structures or in the extracellular space. Next, we used a mouse model of AMD, Ccl2/Cx3cr1 double knockout on rd8 background (DKO rd8) to ascertain the in vivo relevance. Ultrastructural studies of the RPE of these mice showed damaged mitochondria, autophagosome-like structures, and cytoplasmic vacuoles, which are reminiscent of the pathology seen in stressed ARPE-19 cells. The data suggest that the NLRP3 inflammasome may contribute in AMD pathogenesis.

Mesenchymal Stem Cells Modulate Light-induced Activation of Retinal Microglia Through CX3CL1/CX3CR1 Signaling

PURPOSE

To evaluate the effect of CX3CL1/CX3CR1 signaling on the interaction between mesenchymal stem cells (MSCs) and retinal microglia.

METHODS

Supernatants of homogenized retina were harvested from light-damaged SD rats (ISHR) to stimulated retinal microglia. Stimulated microglia were cocultured with MSCs, CX3CL1 over-expressing MSCs (CX3CL1-MSCs) or CX3CL1-blocked MSCs (anti-CX3CL1-MSCs) for 24 hours, and their molecular and functional changes were examined. Moreover, soluble CX3CL1 was directly added to microglia cultures.

RESULTS

ISHR stimulation activated retinal microglia. MSCs coculture inhibited the protein expression of pro-inflammatory factors by activated microglia, increased the protein expression of neurotrophic factors, and was accompanied with upregulation of CX3CR1. Meanwhile, MSCs suppressed proliferative and migratory function of activated microglia, but promoted the phagocytic capability. These effects were strengthened by CX3CL1- MSCs, and reversed by anti-CX3CL1-MSCs. Soluble CX3CL1 could enhanced microglial migration.

CONCLUSIONS

MSCs might restore homeostatic functions of retinal microglia responded to light damage mainly through CX3CL1/CX3CR1 signaling.

Classifying aging as a disease in the context of ICD-11

Aging is a complex continuous multifactorial process leading to loss of function and crystalizing into the many age-related diseases. Here, we explore the arguments for classifying aging as a disease in the context of the upcoming World Health Organization's 11th International Statistical Classification of Diseases and Related Health Problems (ICD-11), expected to be finalized in 2018. We hypothesize that classifying aging as a disease with a "non-garbage" set of codes will result in new approaches and business models for addressing aging as a treatable condition, which will lead to both economic and healthcare benefits for all stakeholders. Actionable classification of aging as a disease may lead to more efficient allocation of resources by enabling funding bodies and other stakeholders to use quality-adjusted life years (QALYs) and healthy-years equivalent (HYE) as metrics when evaluating both research and clinical programs. We propose forming a Task Force to interface the WHO in order to develop a multidisciplinary framework for classifying aging as a disease with multiple disease codes facilitating for therapeutic interventions and preventative strategies.

Parainflammation, chronic inflammation, and age-related macular degeneration

Inflammation is an adaptive response of the immune system to noxious insults to maintain homeostasis and restore functionality. The retina is considered an immune-privileged tissue as a result of its unique anatomic and physiologic properties. During aging, the retina suffers from a low-grade chronic oxidative insult, which sustains for decades and increases in level with advancing age. As a result, the retinal innate-immune system, particularly microglia and the complement system, undergoes low levels of activation (parainflammation). In many cases, this parainflammatory response can maintain homeostasis in the healthy aging eye. However, in patients with age-related macular degeneration, this parainflammatory response becomes dysregulated and contributes to macular damage. Factors contributing to the dysregulation of age-related retinal parainflammation include genetic predisposition, environmental risk factors, and old age. Dysregulated parainflammation (chronic inflammation) in age-related macular degeneration damages the blood retina barrier, resulting in the breach of retinal-immune privilege, leading to the development of retinal lesions. This review discusses the basic principles of retinal innate-immune responses to endogenous chronic insults in normal aging and in age-related macular degeneration and explores the difference between beneficial parainflammation and the detrimental chronic inflammation in the context of age-related macular degeneration.

Delivery strategies for treatment of age-related ocular diseases: From a biological understanding to biomaterial solutions

Age-related ocular diseases, such as age-related macular degeneration (AMD), diabetic retinopathy, and glaucoma, result in life-long functional deficits and enormous global health care costs. As the worldwide population ages, vision loss has become a major concern for both economic and human health reasons. Due to recent research into biomaterials and nanotechnology major advances have been gained in the field of ocular delivery. This review provides a summary and discussion of the most recent strategies employed for the delivery of both drugs and cells to the eye to treat a variety of age-related diseases. It emphasizes the current challenges and limitations to ocular delivery and how the use of innovative materials can overcome these issues and ultimately provide treatment for age-related degeneration and regeneration of lost tissues. This review also provides critical considerations and an outlook for future studies in the field of ophthalmic delivery.

Polypoidal choroidal vasculopathy in patients aged less than 50 years: characteristics and 6-month treatment outcome

PURPOSE

To investigate the characteristics and 6-month treatment outcome of polypoidal choroidal vasculopathy (PCV) in patients aged <50 years.

METHODS

This retrospective study included 22 eyes from 22 patients who were <50 years old and had been diagnosed with treatment naïve PCV. Analyses of treatment outcome were performed in eyes treated with anti-vascular endothelial growth factor (VEGF) therapy. Eyes that exhibited submacular hemorrhage of ≥1 disc diameter and involving the fovea were included in the hemorrhage group. The remaining eyes were included in the no-hemorrhage group. The baseline best-corrected visual acuity (BCVA) was compared with that at 6 months within each group.

RESULTS

The mean age of the 22 patients was 46.5 ± 1.8 (range, 43-49) years. Submacular hemorrhage was noted in ten eyes (45.5 %). The presence of drusen was noted in one eye and pseudodrusen was not noted in any of the eyes included. Treatment outcome was analyzed in 18 eyes. A mean number of 2.9 ± 0.5 intravitreal anti-VEGF injections were administered during the 6-month follow-up period. In the no-hemorrhage group (n = 10), the BCVA at diagnosis and at 6 months was 0.55 ± 0.32 and 0.35 ± 0.22 respectively (P = 0.011). In the hemorrhage group (n = 8), the values were 0.99 ± 0.45 and 0.74 ± 0.63 respectively (P = 0.128).

CONCLUSIONS

A relatively high proportion of young PCV patients exhibited submacular hemorrhage at initial presentation. In those without submacular hemorrhage, intravitreal anti-VEGF therapy was found to be beneficial.

Macular perfusion in healthy Chinese: an optical coherence tomography angiogram study

PURPOSE

To investigate macular perfusion in healthy Chinese individuals and examine its dependence on age and sex.

METHODS

Healthy adult Chinese individuals were recruited. Macular perfusion was measured by spectral-domain optical coherence tomography (OCT) using the split-spectrum amplitude-decorrelation angiography (SSADA) algorithm. The parafoveal flow index and vessel area density as well as the area of the foveal capillary-free zone (CFZ) were quantified.

RESULTS

A total of 76 eyes in 45 subjects were included (20 males and 25 females, mean age 36 ± 11 years). The mean parafoveal flow index was 0.099 ± 0.013; the mean vessel area density was 0.891 ± 0.073; and the mean CFZ area was 0.474 ± 0.172 mm2. All three parameters were significantly correlated with age (flow index: P = 0.00; vessel area density: P = 0.00; CFZ area: P = 0.02). The flow index and vessel area density decreased annually by 0.6% and 0.4%, respectively, and CFZ area increased by 1.48% annually. The CFZ area was larger in females than in males, while all three parameters seemed to change more rapidly with age in males than in females.

CONCLUSIONS

In healthy Chinese eyes, macular perfusion decreased with increasing age, and decreased more rapidly in males than in females. The application of OCT angiograms may provide a useful approach for monitoring macular perfusion, although caution must be exercised with regard to age- and sex-related variations.

IL10-driven STAT3 signalling in senescent macrophages promotes pathological eye angiogenesis

Macrophage dysfunction plays a pivotal role during neovascular proliferation in diseases of ageing including cancers, atherosclerosis and blinding eye disease. In the eye, choroidal neovascularization (CNV) causes blindness in patients with age-related macular degeneration (AMD). Here we report that increased IL10, not IL4 or IL13, in senescent eyes activates STAT3 signalling that induces the alternative activation of macrophages and vascular proliferation. Targeted inhibition of both IL10 receptor-mediated signalling and STAT3 activation in macrophages reverses the ageing phenotype. In addition, adoptive transfer of STAT3-deficient macrophages into eyes of old mice significantly reduces the amount of CNV. Systemic and CD163⁺ eye macrophages obtained from AMD patients also demonstrate STAT3 activation. Our studies demonstrate that impaired SOCS3 feedback leads to permissive IL10/STAT3 signalling that promotes alternative macrophage activation and pathological neovascularization. These findings have significant implications for our understanding of the pathobiology of age-associated diseases and may guide targeted immunotherapy.

Pathological neovascularization causes blinding eye disease. Here the authors show that IL10 activates STAT3 signalling in the macrophages in the ageing eye, promoting their polarization towards a pro-angiogenic phenotype; interfering with this pathway reverses the pathology in a mouse model.

Inflammation and Cell Death in Age-Related Macular Degeneration: An Immunopathological and Ultrastructural Model

The etiology of Age-related Macular Degeneration (AMD) remains elusive despite the characterization of many factors contributing to the disease in its late-stage phenotypes. AMD features an immune system in flux, as shown by changes in macrophage polarization with age, expression of cytokines and complement, microglial accumulation with age, etc. These point to an allostatic overload, possibly due to a breakdown in self vs. non-self when endogenous compounds and structures acquire the appearance of non-self over time. The result is inflammation and inflammation-mediated cell death. While it is clear that these processes ultimately result in degeneration of retinal pigment epithelium and photoreceptor, the prevalent type of cell death contributing to the various phenotypes is unknown. Both molecular studies as well as ultrastructural pathology suggest pyroptosis, and perhaps necroptosis, are the predominant mechanisms of cell death at play, with only minimal evidence for apoptosis. Herein, we attempt to reconcile those factors identified by experimental AMD models and integrate these data with pathology observed under the electron microscope—particularly observations of mitochondrial dysfunction, DNA leakage, autophagy, and cell death.

Small Drusen and Age-Related Macular Degeneration: The Beaver Dam Eye Study

We tested the hypothesis that large areas of small hard drusen (diameter <63 µm) and intermediate drusen (diameter 63–124 µm) are associated with the incidence of age-related macular degeneration (AMD). Eyes of 3344 older adults with at least two consecutive visits spaced five years apart over a 20-year period were included. A 6-level severity scale, including no drusen, four levels of increasing area (from minimal (<2596 µm²) to large (>9086 µm²)) of only small hard drusen, and intermediate drusen, was used. The five-year incidence of AMD was 3% in eyes at the start of the interval with no, minimal, small, and moderate areas of only small drusen and 5% and 25% for eyes with large area of only small drusen and intermediate drusen, respectively. Compared to eyes with a moderate area of small drusen, the odds ratio (OR) of developing AMD in eyes with a large area of only small drusen was 1.8 (p < 0.001). Compared to eyes with large area of only small drusen, eyes with intermediate drusen had an OR of 5.5 (p < 0.001) of developing AMD. Our results are consistent with our hypothesis that large areas of only small drusen are associated with the incidence of AMD.

Age-related increases in amyloid beta and membrane attack complex: evidence of inflammasome activation in the rodent eye

BACKGROUND

The membrane attack complex (MAC) is a key player in the pathogenesis of age-related macular degeneration (AMD) and is a putative activator of the NLRP3 inflammasome. Amyloid beta (Aβ), a component of drusen deposits, has also been implicated in inflammasome activation by our work and those of others. However, the interactions of MAC and Aβ are still poorly understood, especially their roles in aging and retinal degenerative pathologies. Since inflammasome activation may represent a key cellular pathway underlying age-related chronic inflammation in the eye, the purpose of this study is to identify the effects associated with MAC and inflammasome activation in the retinal pigment epithelium (RPE)/choroid and to evaluate the therapeutic merits of MAC suppression.

METHODS

Adult Long-Evans rats were divided into treatment and control groups. Treatment groups received oral aurin tricarboxylic acid complex (ATAC), a MAC inhibitor, in drinking-water, and control groups received drinking-water alone (No ATAC). Groups were sacrificed at 7.5 or 11.5 months, after approximately 40 days of ATAC treatment. To study age-related changes of Aβ and MAC in RPE/choroid, naive animals were sacrificed at 2.5, 7.5, and 11.5 months. Eye tissues underwent immunohistochemistry and western blot analysis for MAC, Aβ, NF-κB activation, as well as cleaved caspase-1 and IL-18. Vitreal samples were collected and assessed by multiplex assays for secreted levels of IL-18 and IL-1β. Statistical analyses were performed, and significance level was set at p ≤ 0.05.

RESULTS

In vivo studies demonstrated an age-dependent increase in MAC, Aβ, and NF-κB activation in the RPE/choroid. Systemic ATAC resulted in a prominent reduction in MAC formation and a concomitant reduction in inflammasome activation measured by cleaved caspase-1 and secreted levels of IL-18 and IL-1β, but not in NF-κB activation. In vitro studies demonstrated Aβ-induced MAC formation on RPE cells.

CONCLUSIONS

Age-dependent increases in Aβ and MAC are present in the rodent outer retina. Our results suggest that suppressing MAC formation and subsequent inflammasome activation in the RPE/choroid may reduce chronic low-grade inflammation associated with IL-18 and IL-1β in the outer retina.