Age-related macular degeneration: etiology, pathogenesis, and therapeutic strategies

VEGF receptor 2 inhibitor nintedanib completely reverts VEGF-A165-induced disturbances of barriers formed by retinal endothelial cells or long-term cultivated ARPE-19 cells

Various severe ocular diseases are associated with an elevated intravitreal expression of VEGF-A which increases the permeability of retinal endothelial cells (REC) or retinal pigment epithelial (RPE) cells in vivo and in vitro. Inhibition of VEGF receptor 2 (VEGFR2) is sufficient to completely prevent VEGF-A₁₆₅-induced dysfunctions of barriers formed by long-term cultivated, immortal human ARPE-19 cells or immortalized bovine retinal endothelial cells (iBREC). Extended exposure to VEGF-A could result in additional activation of other growth factor receptors, potentially promoting synergistic effects of corresponding factors on various cellular processes including angiogenesis. Based on these observations, we investigated whether blocking of VEGFR2 is also sufficient to revert VEGF-A-induced changes of the barriers consisting of iBREC (i.e. inner blood-retina barrier) or ARPE-19 cells (i.e. outer blood-retina barrier) in vitro. Alterations of confluent monolayers' properties induced by treatment with VEGF-A₁₆₅ for one day followed by addition of small molecule inhibitors of the VEGFR2 were determined by continuous cell index (CI) measurements using the microelectronic biosensor system for cell-based assays xCELLigence. VEGF-A₁₆₅ induced a long-lasting drop of the otherwise high CI of iBREC accompanied by reduced expression of the tight junction (TJ) protein claudin-1 and subtle changes of the plasma membrane localizations of TJ-protein claudin-5 and of vascular endothelial cadherin. Blocking mainly VEGFR2 with 10 nM nintedanib, 10 nM tivozanib or 500 nM ZM323881 efficiently reverted these changes within one day; higher concentrations of nintedanib or additional inhibition of neuropilin-1 were not superior. Interestingly, the CI of short-term cultivated, confluent ARPE-19 cells slightly increased in the presence of VEGF-A₁₆₅, but was not changed by nintedanib. In contrast, VEGF-A₁₆₅ markedly reduced the transepithelial electrical resistance of ARPE-19 cells cultivated on porous membrane inserts for three weeks, which was also accompanied by a significant loss of the then strongly plasma membrane-expressed TJ-protein ZO-1. These alterations were completely reverted within one day by 10 nM nintedanib of which higher concentrations were not superior. None of the inhibitors tested diminished the strong barrier properties of iBREC or long-term cultivated ARPE-19 cells. Taken together, inhibition of VEGFR2 efficiently reverts VEGF-A₁₆₅-induced barrier disturbances of both cell types forming and regulating the inner and outer blood-retina barrier. As synergistic actions of growth factors seem to play only a minor role in inducing a barrier dysfunction, specific inhibition of VEGFR2 could be an interesting option to treat VEGF-A-induced macular edema without obvious effects on vitality and functions of REC and RPE cells.

TSP1 ameliorates age-related macular degeneration by regulating the STAT3-iNOS signaling pathway

Age-related macular degeneration is a progressive ocular disease that is the leading cause of vision loss among elderly. AMD usually is divided into two types: wet and dry AMD, which is linked with inflammation. Choroidal Neovascularization (CNV) formation or wet AMD is also associated with oxidative stress. Previously, TSP1 has been shown to have a significant alleviating effect on CNV in TSP1 knockout (TSP1-/-) mice. However, the mechanism by which TSP1 ameliorates CNV remains unclear. Here we report that TSP1 reduces nitric oxide production to prevent cells from forming tubes formation and reduced the levels of vascular endothelial growth factor (VEGF) and lipid peroxides (LPO) during oxidative stress. We measured RF/6A cell viability by CCK-8 assay and apoptosis by flow cytometry. RF/6A cell were transfected with TSP1 and STAT3 overexpression, and then the mRNA and protein levels of TSP1 and also the signal pathways were detected by qRT-PCR and Western blot analysis. Migration assays were performed using a transwell system. Co-Immunoprecipitation was used to analyze the binding relationship between CD47 and SHP-2. The results show that overexpression of TSP1 alleviated the damage of oxidative stress to RF/6A cells including increased cell activity and migration, decreased apoptosis and reduced migration compared to the control group. SHP-2 was activated by TSP1 through its receptor CD47 and STAT3 phosphorylation was reduced by activation of SHP-2, thereby blocking STAT3-iNOS pathway and reducing NO concentration in RF/6A cells ultimately protecting them from oxidative stress. Finally, the CNV mice model confirmed that TSP1 overexpression could protect the mice against CNV in vivo, modified the antioxidants levels and decreased the expression of TNF-α and IL-6 under laser irradiation. These results indicate a potential mechanism of TSP1 to slow down formation of CNV in wet AMD, which may bring hope for new treatment strategies.

Diacron reactive oxygen metabolites and biological antioxidant potential tests for patients with age-related macular degeneration

BACKGROUND

Previously, we showed that serum malondialdehyde (MDA) was significantly higher in patients with neovascular age-related macular degeneration (nAMD) than in those without AMD. The Diacron reactive oxygen metabolites (d-ROMs) and biological antioxidant potential (BAP) tests are known markers of oxidative stress. The aim of this study was to use d-ROMs and BAP tests to evaluate changes in systemic oxidative stress in patients with nAMD.

METHODS

Blood serum samples were collected from 34 patients with nAMD (mean age: 76.5 ± 7.7 years; 22 men) and 20 control subjects (mean age: 62.9 ± 14.0 years; 10 men), and d-ROMs and BAP tests were examined.

RESULTS

In men, the mean level of d-ROMs for the nAMD patients was significantly higher than that for the controls (312.0 ± 52.4 vs. 275.1 ± 45.5 U.CARR, respectively; P < .05). There was a significant correlation between d-ROM level and CNV lesion area in the male nAMD group (r = .42, P = .05). There were no significant differences in mean BAP test results between the nAMD patients and controls for either sex (men: 2241 ± 549 vs. 2136 ± 246 μmol/L; women: 2263 ± 292 vs. 2335 ± 161 μmol/L).

CONCLUSION

The d-ROMs test may provide a useful indicator of nAMD in men but not in women.

A novel dendrimer-based complex co-modified with cyclic RGD hexapeptide and penetratin for noninvasive targeting and penetration of the ocular posterior segment

Noninvasive drug delivery is a promising treatment strategy for ocular posterior segment diseases. Many physiological and anatomical barriers of the eye considerably restrict effective diffusion of therapeutics to the target site. To overcome this problem, a novel cyclic arginine-glycine-aspartate (RGD) hexapeptide and penetratin (PEN) co-modified PEGylation polyamidoamine (PAMAM) was designed as a nanocarriers (NCs), and its penetrating and targeting abilities were evaluated. In this study, we show that PAMAM-PEG (reaction molar ratio 1:32) has a relatively high grafting efficiency and low cytotoxicity. The particle size was within the range of 15-20 nm after modification with RGD and PEN. Cellular uptake of RGD-modified NCs involved significant affinity toward integrin αvβ3, which validated the targeting of neovasculature. An in vitro permeation study indicated that modification with PEN significantly improved penetration of the NCs (1.5 times higher). In vivo ocular distribution studies showed that, the NCs (modified with PEN or co-modified with RGD and PEN) were highly distributed in the cornea and retina (p < .001), and modification extended retinal retention time for more than 12 h. Therefore, these NCs appear to be a promising noninvasive ocular drug delivery system for ocular posterior segment diseases.

Caspase-1-dependent inflammasomes mediate photoreceptor cell death in photo-oxidative damage-induced retinal degeneration

Activation of the inflammasome is involved in the progression of retinal degenerative diseases, in particular, in the pathogenesis of Age-Related Macular Degeneration (AMD), with NLRP3 activation the focus of many investigations. In this study, we used genetic and pharmacological approaches to explore the role of the inflammasome in a mouse model of retinal degeneration. We identify that Casp1/11^−/− mice have better-preserved retinal function, reduced inflammation and increased photoreceptor survivability. While Nlrp3^−/− mice display some level of preservation of retinal function compared to controls, pharmacological inhibition of NLRP3 did not protect against photoreceptor cell death. Further, Aim2^−/−, Nlrc4^−/−, Asc^−/−, and Casp11^−/− mice show no substantial retinal protection. We propose that CASP-1-associated photoreceptor cell death occurs largely independently of NLRP3 and other established inflammasome sensor proteins, or that inhibition of a single sensor is not sufficient to repress the inflammatory cascade. Therapeutic targeting of CASP-1 may offer a more promising avenue to delay the progression of retinal degenerations.

Genetic association with intravitreal ranibizumab response for neovascular age-related macular degeneration in Hispanic population

BACKGROUND/PURPOSE:

Age-related macular degeneration (AMD) is the leading cause of visual impairment in patients over 55 years. Currently, the most common therapies for neovascular AMD (nAMD) are intravitreal antiangiogenics. Studies suggest that genetic factors influence on antiangiogenics therapy outcomes. The purpose of this work was to establish the association between complement factor H (CFH) (Y402H), age-related maculopathy susceptibility 2 (ARMS2) (A69S), and high-temperature requirement factor A1 (HTRA1) (rs11200638) polymorphisms and the response to treatment with ranibizumab in patients with nAMD.

METHODS:

A cross-sectional study with 61 eyes with nAMD treated with ranibizumab was performed. Association between polymorphisms from CFH, ARMS2, and HTRA1 with the response to treatment was established.

RESULTS:

The mean age of patients was 76.6 (51–91) years. Only 37.7% of patients had a functional response and 26.2% had an anatomic response. TT polymorphism Y402H from CFH gene was associated with an increased likelihood of functional response to treatment. Otherwise, there was not a statistically significant association between anatomic and functional response to gene polymorphisms rs11200638 from HTRA1 and rs10490924 from ARMS 2.

CONCLUSIONS:

This study suggests that the response to intravitreal antiangiogenic therapy with ranibizumab was not associated to main polymorphisms from genes HTRA1 and ARMS2. However, it was found that the response to treatment differed according to CFH genotype, suggesting that further investigations are needed to establish if patients with the CC and TC genotype may need to be monitored more closely for disease recurrence than the TT genotype.

Altered Long Non-coding RNAs Involved in Immunological Regulation and Associated with Choroidal Neovascularization in Mice

Choroidal neovascularization (CNV) is a severe complication of the wet form of age-related macular degeneration (AMD). Long non-coding RNAs (lncRNAs) have been implicated in the pathogenesis of different ocular neovascular diseases. To identify the function and therapeutic potential of lncRNAs in CNV, we assessed lncRNAs and mRNA expression profile in a mouse model of laser-induced CNV by microarray analysis. The results of altered lncRNAs were validated by qRT-PCR. Bioinformatics analyses, including Gene Ontology (GO) analysis and Kyoto Encyclopedia of Genes and Genomes (KEGG) pathway analysis, were performed to clarify the potential biological functions and signaling pathways with which altered genes are most closely related. Moreover, to identify the interaction of lncRNAs and mRNAs, we constructed a coding-non-coding gene co-expression (CNC) network. By microarray analysis, we identified 716 altered lncRNAs and 821 altered mRNAs in CNV mice compared to controls. A CNC network profile based on 7 validated altered lncRNAs (uc009ewo.1, AK148935, uc029sdr.1, ENSMUST00000132340, AK030988, uc007mds.1, ENSMUST00000180519) as well as 282 interacted and altered mRNAs, and were connected by 713 edges. GO and KEGG analyses suggested that altered mRNAs, as well as those lncRNA-interacted mRNAs were enriched in immune system process and chemokine signaling pathway. Thus, lncRNAs are significantly altered in this mouse model of CNV and are involved in immunological regulation, suggesting that lncRNAs may play a critical role in the pathogenesis of CNV. Thus, dysregulated lncRNAs and their target genes might be promising therapeutic targets to suppress CNV in AMD.

Effect of Inhibition of Colony-Stimulating Factor 1 Receptor on Choroidal Neovascularization in Mice

Neovascular age-related macular degeneration is one of the leading causes of blindness. Microglia and macrophages play a critical role in choroidal neovascularization (CNV) and may, therefore, be potential targets to modulate the disease course. This study evaluated the effect of the colony-stimulating factor-1 receptor inhibitor PLX5622 on experimental laser-induced CNV. A 98% reduction of retinal microglia cells was observed in the retina 1 week after initiation of PLX5622 treatment, preventing accumulation of macrophages within the laser site and leading to a reduction of leukocytes within the choroid after CNV induction. Mice treated with PLX5622 had a significantly faster decrease of the CNV lesion size, as revealed by in vivo imaging and immunohistochemistry from day 3 to day 14 compared with untreated mice. Several inflammatory modulators, such as chemokine (C-C motif) ligand 9, granulocyte-macrophage colony-stimulating factor, soluble tumor necrosis factor receptor-I, IL-1α, and matrix metallopeptidase-2, were elevated in the acute phase of the disease when microglia were ablated with PLX5622, whereas other cytokines (eg, interferon-γ, IL-4, and IL-10) were reduced. Our results suggest that colony-stimulating factor-1 receptor inhibition may be a novel therapeutic target in patients with neovascular age-related macular degeneration.

Incremental economic burden associated with exudative age-related macular degeneration: a population-based study

BACKGROUND

The exudative age-related macular degeneration (AMD) causes considerable healthcare costs for patients and healthcare system, which are expected to grow as the population ages. The objective of this study was to assess the incremental economic burden of exudative AMD by comparing total healthcare costs between the exudative AMD group and non-AMD group to understand economic burden related to exudative AMD.

METHODS

This retrospective cohort study used the National Health Insurance Service database including the entire Korean population. Exudative AMD group included individuals with at least one claim for ranibizumab and one claim using the registration code for exudative AMD (V201). Non-AMD group was defined as individuals without any claims regarding the diagnostic code of H35.3 or ranibizumab. The exudative AMD group and non-AMD group were matched using a propensity-score model. Incremental healthcare resource utilization and healthcare costs were measured during a one-year follow-up by employing econometric models: ordinary least squares (OLS) with log transformation and heteroscedastic retransformation; and generalized linear model (GLM) with a log link function and gamma distribution.

RESULTS

A total of 7119 exudative AMD patients were matched to 7119 non-AMD patients. The number of outpatient visits was higher in the exudative AMD group (P-value < 0.0001), while the length of hospitalization was shorter in exudative AMD group (P-value < 0.0001). Exudative AMD patients had total costs 2.13 times (95%CI, 2.08-2.17) greater than non-AMD group using OLS, and total costs 4.06 times (95%CI, 3.82-4.31) greater than non-AMD group using GLM. Annual incremental total costs were estimated as $5519 (OLS) and $3699 (GLM).

CONCLUSIONS

Exudative AMD was associated with significantly increased healthcare costs compared to the non-AMD group. Attention is needed to manage the socioeconomic burden of exudative AMD.

Anti-Angiogenic Activity Of Bevacizumab-Bearing Dexamethasone-Loaded PLGA Nanoparticles For Potential Intravitreal Applications

Purpose

Age-related macular degeneration is a multifactorial disease involving inflammation and choroidal neovascularization. Vascular endothelial growth factor (VEGF) has been regarded as a potential therapeutic target to treat choroidal neovascularization. Dexamethasone can interfere with the expression or action of VEGF while bevacizumab targets and combines with VEGF. We propose electrostatically-conjugated bevacizumab-bearing dexamethasone-loaded poly (D,L-lactide-co-glycolide)/polyethylenimine nanoparticles (eBev-DPPNs) for angiogenic combination treatment of ocular diseases.

Methods

We prepared a novel nanoparticle composed of poly (D, L-lactide-co-glycolide) and polyethylenimine and loaded the nanoparticles with dexamethasone. Bevacizumab was adsorbed onto the surfaces of the nanoparticles by electrostatic interactions. The eBev-DPPNs were evaluated according to their size, polydispersity index, zeta potential, morphology, drug loading, release behavior, and stability. The structural stability of bevacizumab on the surface of the nanoparticles was also analyzed. Subsequently, angiogenesis was investigated in the presence of the eBev-DPPNs using cell apoptosis, wound healing, Transwell invasion, and tube formation assays on the human umbilical vein endothelial cells (HUVECs) in vitro and chick embryo chorioallantoic membrane assay in vivo. The eBev-DPPNs intravitreal injection was applied in the laser-induced rabbit choroidal neovascularization (CNV) model to confirm the role for potential intravitreal applications.

Results

The eBev-DPPNs was about 200 nm in diameter, with a narrow diameter distribution, and the surface charge was neutral (0.85 ± 0.37mV), which made the eBev-DPPNs stable under physiological conditions. The apoptosis, migration, invasion, and tube formation assays showed that the eBev-DPPNs had a good anti-angiogenic effect on HUVECs. The eBev-DPPNs also provided a strong inhibitory effect on VEGF secretion from HUVECs. Moreover, in vivo chick embryo chorioallantoic membrane assay showed eBev-DPPNs greatly reduced the amount of blood vessels. The leakage area of CNV decreased in the eBev-DPPNs group on rabbit CNV model.

Conclusion

The eBev-DPPNs are a promising novel anti-angiogenesis therapeutic for potential intravitreal applications such as age-related macular degeneration.

Real-world data in retinal diseases treated with anti-vascular endothelial growth factor (anti-VEGF) therapy - a systematic approach to identify and characterize data sources

BACKGROUND

Real-world data (RWD) has been a valuable addition to the scientific literature regarding treatment pathways, clinical outcomes and characteristics of patients with retinal diseases in recent years. Registries, observational studies and patient databases are often used for real-world research. However, there is limited information for each data source on the design, consistency, data captured, limitations and usability for assessing research questions. Using a systematic approach, we identified RWD sources for patients with retinal diseases and assessed them for completeness of data relating to different outcomes.

METHODS

A systematic literature review was carried out to identify RWD sources for patients with retinal disease. Potentially relevant articles published between 2006 and 2016 were screened following electronic searches in Embase and MEDLINE. Congress and supplementary searches were undertaken to identify RWD sources that may not be referenced in full publications. For each data source, availability and quantity of data on baseline status, clinical outcomes, treatment and management, safety, and patient-reported and economic burden were assessed using a bespoke completeness assessment tool based on International Consortium for Health Outcomes Measurement guidelines for macular degeneration. Completeness of data for each area of interest in each data source was assessed and rated using a 'good-moderate-poor' rating system based on availability and quantity of available data. Each data source was then given an overall score based on its score for each of the 7 areas of interest.

RESULTS

A total of 128 RWD sources from 32 countries were identified. Of the identified sources, 64 sources from 16 countries of interest were analyzed. Most of these sources provided information on baseline status and clinical outcomes and treatment, but few collected data on economic and patient-reported burden. Of the RWD sources analyzed, 10 scored highly in the overall completeness assessment, collecting data on most or all of the areas of interest; these sources are considered to be robust data sources for performing ophthalmology real-world studies.

CONCLUSIONS

The study provides a comprehensive list of RWD sources for patients with retinal disease, many of which will be useful for conducting real-world studies in the field of ophthalmology.

Oxidative stress-mediated TXNIP loss causes RPE dysfunction

The disruption of the retinal pigment epithelium (RPE), for example, through oxidative damage, is a common factor underlying age-related macular degeneration (AMD). Aberrant autophagy also contributes to AMD pathology, as autophagy maintains RPE homeostasis to ensure blood–retinal barrier (BRB) integrity and protect photoreceptors. Thioredoxin-interacting protein (TXNIP) promotes cellular oxidative stress by inhibiting thioredoxin reducing capacity and is in turn inversely regulated by reactive oxygen species levels; however, its role in oxidative stress-induced RPE cell dysfunction and the mechanistic link between TXNIP and autophagy are largely unknown. Here, we observed that TXNIP expression was rapidly downregulated in RPE cells under oxidative stress and that RPE cell proliferation was decreased. TXNIP knockdown demonstrated that the suppression of proliferation resulted from TXNIP depletion-induced autophagic flux, causing increased p53 activation via nuclear localization, which in turn enhanced AMPK phosphorylation and activation. Moreover, TXNIP downregulation further negatively impacted BRB integrity by disrupting RPE cell tight junctions and enhancing cell motility by phosphorylating, and thereby activating, Src kinase. Finally, we also revealed that TXNIP knockdown upregulated HIF-1α, leading to the enhanced secretion of VEGF from RPE cells and the stimulation of angiogenesis in cocultured human retinal microvascular endothelial cells. This suggests that the exposure of RPE cells to sustained oxidative stress may promote choroidal neovascularization, another AMD pathology. Together, these findings reveal three distinct mechanisms by which TXNIP downregulation disrupts RPE cell function and thereby exacerbates AMD pathogenesis. Accordingly, reinforcing or restoring BRB integrity by targeting TXNIP may serve as an effective therapeutic strategy for preventing or attenuating photoreceptor damage in AMD.

A protein found in retinal cells promotes the development of age-related macular degeneration and may provide a therapeutic target. Sight loss through macular degeneration is triggered by disruption to the retinal pigment epithelium (RPE), a layer of cells that carries nutrients to the eye. RPE cells can be disrupted under oxidative stress conditions, but how this influences macular degeneration is unclear. Jeong-Ki Min and Sang-Hyun Lee at the Korea Research Institute of Bioscience and Biotechnology in Daejeon, South Korea, and co-workers found that oxidative stress reduces levels of the thioredoxin-interacting protein (TXNIP) in human RPE cell cultures. This interrupts cellular communication and disturbs the balance between cell proliferation and cell recycling. It also increases the levels of proteins that promote excess blood vessel formation, a key process contributing to macular degeneration.

Molecular Mechanisms of Complement System Proteins and Matrix Metalloproteinases in the Pathogenesis of Age-Related Macular Degeneration

Age-related macular degeneration (AMD) is an eye disorder affecting predominantly the older people above the age of 50 years in which the macular region of the retina deteriorates, resulting in the loss of central vision. The key factors associated with the pathogenesis of AMD are age, smoking, dietary, and genetic risk factors. There are few associated and plausible genes involved in AMD pathogenesis. Common genetic variants (with a minor allele frequency of >5% in the population) near the complement genes explain 40-60% of the heritability of AMD. The complement system is a group of proteins that work together to destroy foreign invaders, trigger inflammation, and remove debris from cells and tissues. Genetic changes in and around several complement system genes, including the CFH, contribute to the formation of drusen and progression of AMD. Similarly, Matrix metalloproteinases (MMPs) that are normally involved in tissue remodeling also play a critical role in the pathogenesis of AMD. MMPs are involved in the degradation of cell debris and lipid deposits beneath retina but with age their functions get affected and result in the drusen formation, succeeding to macular degeneration. In this review, AMD pathology, existing knowledge about the normal and pathological role of complement system proteins and MMPs in the eye is reviewed. The scattered data of complement system proteins, MMPs, drusenogenesis, and lipofusogenesis have been gathered and discussed in detail. This might add new dimensions to the understanding of molecular mechanisms of AMD pathophysiology and might help in finding new therapeutic options for AMD.

Loss of NAMPT in aging retinal pigment epithelium reduces NAD+ availability and promotes cellular senescence

Retinal pigment epithelium (RPE) performs numerous functions critical to retinal health and visual function. RPE senescence is a hallmark of aging and degenerative retinal disease development. Here, we evaluated the temporal expression of key nicotinamide adenine dinucleotide (NAD⁺)-biosynthetic genes and associated levels of NAD⁺, a principal regulator of energy metabolism and cellular fate, in mouse RPE. NAD⁺ levels declined with age and correlated directly with decreased nicotinamide phosphoribosyltransferase (NAMPT) expression, increased expression of senescence markers (p16^INK4a, p21^Waf/Cip1, ApoJ, CTGF and β-galactosidase) and significant reductions in SIRT1 expression and activity. We simulated in vitro the age-dependent decline in NAD⁺ and the related increase in RPE senescence in human (ARPE-19) and mouse primary RPE using the NAMPT inhibitor FK866 and demonstrated the positive impact of NAD⁺-enhancing therapies on RPE cell viability. This, we confirmed in vivo in the RPE of mice injected sub-retinally with FK866 in the presence or absence of nicotinamide mononucleotide. Our data confirm the importance of NAD⁺ to RPE cell biology normally and in aging and demonstrate the potential utility of therapies targeting NAMPT and NAD⁺ biosynthesis to prevent or alleviate consequences of RPE senescence in aging and/or degenerative retinal diseases in which RPE dysfunction is a crucial element.

Sostdc1 is expressed in all major compartments of developing and adult mammalian eyes

PURPOSE

This study was conducted in order to study Sostdc1 expression in rat and human developing and adult eyes.

METHODS

Using the yeast signal sequence trap screening method, we identified the Sostdc1 cDNA encoding a protein secreted by the adult rat retinal pigment epithelium. We determined by in situ hybridization, RT-PCR, immunohistochemistry, and western blot analysis Sostdc1 gene and protein expression in developing and postnatal rat ocular tissue sections. We also investigated Sostdc1 immunohistolocalization in developing and adult human ocular tissues.

RESULTS

We demonstrated a prominent Sostdc1 gene expression in the developing rat central nervous system (CNS) and eyes at early developmental stages from E10.5 days postconception (dpc) to E13 dpc. Specific Sostdc1 immunostaining was also detected in most adult cells of rat ocular tissue sections. We also identified the rat ocular embryonic compartments characterized by a specific Sostdc1 immunohistostaining and specific Pax6, Sox2, Otx2, and Vsx2 immunohistostaining from embryonic stages E10.5 to E13 dpc. Furthermore, we determined the localization of SOSTDC1 immunoreactivity in ocular tissue sections of developing and adult human eyes. Indeed, we detected SOSTDC1 immunostaining in developing and adult human retinal pigment epithelium (RPE) and neural retina (NR) as well as in several developing and adult human ocular compartments, including the walls of choroidal and scleral vessels. Of utmost importance, we observed a strong SOSTDC1 expression in a pathological ocular specimen of type 2 Peters' anomaly complicated by retinal neovascularization as well in the walls ofother pathological extra-ocular vessels.  CONCLUSION: As rat Sostdc1 and human SOSTDC1 are dual antagonists of the Wnt/β-catenin and BMP signaling pathways, these results underscore the potential crucial roles of these pathways and their antagonists, such as Sostdc1 and SOSTDC1, in developing and adult mammalian normal eyes as well as in syndromic and nonsyndromic congenital eye diseases.

Human Umbilical Tissue-Derived Cells Secrete Soluble VEGFR1 and Inhibit Choroidal Neovascularization

Exudative age-related macular degeneration (AMD), characterized by choroidal neovascularization (CNV), is the leading cause of irreversible blindness in developed countries. Anti-vascular endothelial growth factor (VEGF) drugs are the standard treatment for AMD, but they have limitations. Cell therapy is a promising approach for ocular diseases, and it is being developed in the clinic for the treatment of retinal degeneration, including AMD. We previously showed that subretinal injection of human umbilical tissue-derived cells (hUTCs) in a rodent model of retinal degeneration preserved photoreceptors and visual function through rescue of retinal pigment epithelial (RPE) cell phagocytosis. Here we investigated the effect of hUTCs on a rat model of laser-induced CNV and on a human RPE cell line, ARPE-19, for VEGF production. We demonstrate that subretinal injection of hUTCs significantly inhibited CNV and lowered choroidal VEGF in vivo. VEGF release from ARPE-19 decreased when co-cultured with hUTCs. Soluble VEGF receptor 1 (sVEGFR1) is identified as the only factor in hUTC conditioned medium (CM) that binds to VEGF. The level of exogenous recombinant VEGF in hUTC CM was dramatically reduced and could be recovered with sVEGFR1-neutralizing antibody. This suggests that hUTC inhibits angiogenesis through the secretion of sVEGFR1 and could serve as a novel treatment for angiogenic ocular diseases, including AMD.

MicroRNA-24 protects retina from degeneration in rats by down-regulating chitinase-3-like protein 1

MicroRNAs (miRNAs) have been shown to play critical roles in the pathogenesis and progression of degenerative retinal diseases like age-related macular degeneration (AMD). In this study, we first demonstrated that miR-24 plays an important role in maintaining retinal structure and visual function of rats by targeting chitinase-3-like protein 1 (CHI3L1). In the retinal pigment epithelial (RPE) cells of Royal College of Surgeons (RCS) rats, an animal model of genetic retinal degeneration (RD), miR-24 was found lower and CHI3L1 level was higher in comparison with those in Sprague-Dawley (SD) rats. Other changes in the eyes of RCS rats include activated AKT/mTOR and ERK pathways and abnormal autophagy in the RPE cells. Such roles of miR-24 and CHI3L1 were further confirmed in RCS rats by subretinal injection of agomiR-24, which decreased CHI3L1 level and preserved retinal structure and function. Upstream, NF-κB was identified as the regulator of miR-24 in the RPE cells of these rats. On the other hand, in SD rats, intraocular treatment of antagomiR-24 induced pathological changes similar to those in RCS rats. The results revealed the protective roles for miR-24 to RPE cells and a mechanism for RD in RCS rats was proposed: extracellular stress stimuli first activate the NF-κB signaling pathway, which lowers miR-24 expression so that CHI3L1 increased. CHI3L1 sequentially results in aberrant autophagy and RPE dysfunction by activating AKT/mTOR and ERK pathways. Taken together, although the possibility, that the therapeutic effects in RCS rats are caused by other transcriptional changes regulated by miR-24, cannot be excluded, these findings indicate that miR-24 protects rat retina by targeting CHI3L1. Thus, miR-24 and CHI3L1 might be the targets for developing more effective therapy for degenerative retinal diseases like AMD.

Enantioselective Synthesis of Homoisoflavanones by Asymmetric Transfer Hydrogenation and Their Biological Evaluation for Antiangiogenic Activity

Neovascular eye diseases are a major cause of blindness. Excessive angiogenesis is a feature of several conditions, including wet age-related macular degeneration, proliferative diabetic retinopathy, and retinopathy of prematurity. Development of novel antiangiogenic small molecules for the treatment of neovascular eye disease is essential to provide new therapeutic leads for these diseases. We have previously reported the therapeutic potential of anti-angiogenic homoisoflavanone derivatives with efficacy in retinal and choroidal neovascularization models, although these are racemic compounds due to the C3-stereogenic center in the molecules. This work presents asymmetric synthesis and structural determination of anti-angiogenic homoisoflavanones and pharmacological characterization of the stereoisomers. We describe an enantioselective synthesis of homoisoflavanones by virtue of ruthenium-catalyzed asymmetric transfer hydrogenation accompanying dynamic kinetic resolution, providing a basis for the further development of these compounds into novel experimental therapeutics for neovascular eye diseases.

IL-1 Family Members Mediate Cell Death, Inflammation and Angiogenesis in Retinal Degenerative Diseases

Inflammation underpins and contributes to the pathogenesis of many retinal degenerative diseases. The recruitment and activation of both resident microglia and recruited macrophages, as well as the production of cytokines, are key contributing factors for progressive cell death in these diseases. In particular, the interleukin 1 (IL-1) family consisting of both pro- and anti-inflammatory cytokines has been shown to be pivotal in the mediation of innate immunity and contribute directly to a number of retinal degenerations, including Age-Related Macular Degeneration (AMD), diabetic retinopathy, retinitis pigmentosa, glaucoma, and retinopathy of prematurity (ROP). In this review, we will discuss the role of IL-1 family members and inflammasome signaling in retinal degenerative diseases, piecing together their contribution to retinal disease pathology, and identifying areas of research expansion required to further elucidate their function in the retina.

Piceatannol Protects Human Retinal Pigment Epithelial Cells against Hydrogen Peroxide Induced Oxidative Stress and Apoptosis through Modulating PI3K/Akt Signaling Pathway

This study investigated the protective effect and the molecular mechanism of piceatannol on hydrogen peroxide (H₂O₂)-induced retinal pigment epithelium cell (ARPE-19) damage. Piceatannol treatment significantly inhibited H₂O₂-induced RPE cell death and reactive oxygen species (ROS) generation by 64.4% and 75.0%, respectively. Results of flow cytometry showed that H₂O₂-induced ARPE-19 cells apoptosis was ameliorated by piceatannol supplementation, along with decreased relative protein expressions of Bax/Bcl-2, Cleave-Caspase-3, and Cleave-PARP. Moreover, piceatannol treatment induced NF-E2-related factor 2 (Nrf2) signaling activation, which was evidenced by increased transcription of anti-oxidant genes, glutamate-cysteine ligase catalytic subunit (GCLc), SOD, and HO-1. Knockdown of Nrf2 through targeted siRNA alleviated piceatannol-mediated HO-1 transcription, and significantly abolished piceatannol-mediated cytoprotection. LY294002 (PI3K inhibitor) dramatically blocked piceatannol-mediated increasing of Nrf2 nuclear translocation, HO-1 expression, and cytoprotective activity, indicating the involvement of PI3K/Akt pathway in the cytoprotective effect of piceatannol. The results from this suggest the potential of piceatannol in reducing the risk of age-related macular degeneration.

Systemic activation of the complement system in patients with advanced age-related macular degeneration

Purpose:

To examine the role of systemic activation of the complement system (assessed by levels of circulating C3a, Ba, and sC5b-9) in patients (n = 122) with advanced age-related macular degeneration, geographic atrophy, and neovascular age-related macular degeneration, compared with cataract controls (n = 27).

Methods:

Plasma complement factors were measured using enzyme-linked immunosorbent assays. Statistical analysis included univariate and multivariate logistic regression (p < 0.05).

Results:

Adjusted for age, the odds ratios of C3a and sC5b-9 for any advanced age-related macular degeneration were 1.78 (95% confidence interval = 1.16–2.73, p < 0.01) and 1.20 (95% confidence interval = 1.04–1.39, p = 0.01), respectively. We found a significantly elevated adjusted odds ratio of C3a (adjusted odds ratio = 1.71, 95% confidence interval = 1.12–2.60, p = 0.01) and sC5b-9 (adjusted odds ratio = 1.22, 95% confidence interval = 1.04–1.43, p = 0.01) for neovascular age-related macular degeneration. Adjusted for age, neither C3a, sC5b-9, nor Ba were associated with geographic atrophy.

Conclusion:

We suggest a role for elevated plasma levels of C3a and sC5b-9 in patients with neovascular age-related macular degeneration. The study’s results reinforce the need for more investigation to assess the impact of therapeutic interventions targeted at the complement signaling pathways in age-related macular degeneration.

MicroRNA-124 Dysregulation is Associated With Retinal Inflammation and Photoreceptor Death in the Degenerating Retina

Purpose

We sought to determine the role and retinal cellular location of microRNA-124 (miR-124) in a neuroinflammatory model of retinal degeneration. Further, we explored the anti-inflammatory relationship of miR-124 with a predicted messenger RNA (mRNA) binding partner, chemokine (C-C motif) ligand 2 (Ccl2), which is crucially involved in inflammatory cell recruitment in the damaged retina.

Methods

Human AMD donor eyes and photo-oxidative damaged (PD) mice were labeled for miR-124 expression using in situ hybridization. PDGFRa-cre RFP mice were used for Müller cell isolation from whole retinas. MIO-M1 immortalized cells and rat primary Müller cells were used for in vitro analysis of miR-124 expression and its relationship with Ccl2. Therapeutic efficacy was tested with intravitreal administration of miR-124 mimic in mice, with electroretinography used to determine retinal function. IBA1 immunohistochemistry and photoreceptor row counts were used for assessment of inflammation and cell death.

Results

MiR-124 expression was correlated with progressive retinal damage, inflammation, and cell death in human AMD and PD mice. In addition, miR-124 expression was inversely correlated to Ccl2 expression in mice following PD. MiR-124 was localized to both neuronal-like photoreceptors and glial (Müller) cells in the retina, with a redistribution from neurons to glia occurring as a consequence of PD. Finally, intravitreal administration of miR-124 mimics decreased retinal inflammation and photoreceptor cell death, and improved retinal function.

Conclusions

This study has provided an understanding of the mechanism behind miR-124 in the degenerating retina and demonstrates the usefulness of miR-124 mimics for the modulation of retinal degenerations.

Membrane patterns in eyes with choroidal neovascularization on optical coherence tomography angiography

BACKGROUND

To evaluate morphologic patterns of choroidal neovascular membranes using optical coherence tomography angiography (OCTA) in patients with treatment-naive, continuously treated, and previously treated exudative age-related macular degeneration (AMD).

SUBJECTS

We assessed retrospectively 184 eyes of 153 patients diagnosed with type 1, type 2, and mixed-type neovascularization associated with AMD. The type of neovascularization and clinical activity were assessed by clinical examination and spectral domain optical coherence tomography (SD-OCT). Morphological patterns of neovascular membranes were categorized using en face images on the AngioVue (Optovue) OCTA system.

RESULTS

The mean age of patients was 77.9 ± 8.6 years (range, 52-96 years). The most frequently identified type of membrane morphology was well-defined in the treatment-naive group (69% of the eyes) and in eyes receiving ongoing anti-VEGF treatments (77% of the eyes). Long-filamentous morphology was the most frequent type in the previously treated group (53%), in which only 33% had a well-defined membrane. All clinically active cases had a well-defined pattern, such as a medusa or sea-fan shaped pattern, or an ill-defined pattern, and none had a long-filamentous neovascular network. Almost half of the clinically inactive cases (47%) had well- or ill-defined, identifiable membrane morphology on OCTA. A long-filamentous membrane pattern, which was consistent with chronicity of lesion, was seen only in eyes with inactive neovascularization.

CONCLUSIONS

The membrane morphology on OCTA was not associated with clinical activity, except that the presence of long dilated filamentous linear vessels was associated with chronicity and lesion inactivity.

The association of matrix metalloproteinases polymorphisms and interleukins in advanced age-related macular degeneration

PURPOSE

To assess the impact of matrix metalloproteinase (MMP)1-1607 1G/2G (rs1799750), MMP7-181 A/G (rs11568818) single-nucleotide polymorphism and systemic cytokins interleukin-1 beta (IL-1β), IL-6 levels on the development of exudative age-related macular degeneration (eAMD) Methodology: The study group comprised 282 patients with eAMD, and the control group enrolled 379 randomly selected persons. The genotyping of MMP1-1607 (rs1799750) and MMP7-181 (rs11568818) was performed by using the polymerase chain reaction-based restriction fragment length polymorphism method. To determine IL-1β and IL-6 serum levels, the immunoenzymatic method with monoclonal antibodies coated plates was performed.

RESULTS

MMP1 rs1799750 1G/2G genotype was more frequently found in the development of eAMD. It was associated with a 4.3-fold increased risk for eAMD under the codominant model and a 4.9-fold increased risk for eAMD under the overdominant model. The effect was more pronounced at the age of less than 65 years. IL-1β concentration was significantly higher for MMP1 rs1799750 1G/1G genotype and MMP7 rs11568818 A/G genotype in eAMD patients compared with control group subjects.

CONCLUSIONS

MMP1 rs1799750 1G/2G genotype was found to play a significant role in the development of eAMD at the age of less than 65 years. IL-1β concentration was significantly higher in eAMD patients for MMP1 rs1799750 1G/1G genotype and MMP7 rs11568818 A/G genotype compared with control group subjects.

Relationship of Area of Soft Drusen in Retina with Cerebral Amyloid-β Accumulation and Blood Amyloid-β Level in the Elderly

BACKGROUND

Histopathological studies have confirmed that soft drusen contains amyloid-β (Aβ).

OBJECTIVE

To examine the relationship between the area of soft drusen in the macular area and cerebral Aβ accumulation or plasma Aβ level in elderly persons without dementia.

METHODS

Fourteen consecutive patients (18 eyes) aged ≥50 years with macular soft drusen were studied prospectively. From color fundus photographs, the area of soft drusen (pixel) within a 6,000 μm diameter with the macula as center was measured. Standard uptake value ratio (SUVR) was obtained from positron emission tomography using florbetapir, which indicates the ratio of cerebral cortical-to-cerebellar Aβ accumulation. Ratio of plasma Aβ1-42 to Aβ1-40 level was calculated.

RESULTS

Mean age was 73.3±7.6 years. The soft drusen area was 4.32±2.42 mm2. The SUVR was 1.08±0.15. Plasma Aβ1-42/Aβ1-40 ratio was 0.17±0.08. When SUVR ≥1.10 was defined as positive and <1.10 as negative, the soft drusen area in SUVR-positive patients (6.19±1.14 mm2) was significantly (p = 0.0043) larger than that in SUVR-negative patients (3.13±2.27 mm2). Multivariate regression analysis showed that SUVR positivity correlated with soft drusen area (p = 0.0484) and with Voxel-based Specific Regional Analysis System for Alzheimer's Disease score (p = 0.0360). However, there was no correlation with gender (p = 0.1921), age (p = 0.2361), Alzheimer's Disease Assessment Scale score (p = 0.6310), Mini-Mental State Examination score (p = 0.4246), or plasma Aβ1-42/Aβ1-40 ratio (p = 0.8398).

CONCLUSION

Among elderly persons without dementia, the area of soft drusen was larger in those with more extensive cerebral Aβ accumulation. The area of soft drusen may be a biomarker of cerebral Aβ accumulation.

Subfoveal Choroidal Thickness as a Potential Predictor of Clinical Response to Stereotactic Radiotherapy for Neovascular Age-Related Macular Degeneration

BACKGROUND AND OBJECTIVE

Stereotactic radiotherapy (SRT) is a new adjuvant treatment modality that has been shown to reduce the need for repetitive intravitreal injections (IVIs) in patients with neovascular age-related macular degeneration (nAMD). The authors aimed to determine baseline predictors of clinical response to SRT.

PATIENTS AND METHODS

This was a retrospective, observational case series of patients with nAMD who underwent SRT and subsequently had at least 12 months of complete follow-up. After SRT and one mandatory IVI, patients were examined every 4 weeks and received further treatment on a pro re nata basis. Examination included enhanced depth imaging spectral-domain optical coherence tomography (SD-OCT) to measure subfoveal choroidal thickness (SFCT) and central macular thickness (CMT). Patients' data were retrieved from medical records and included demographics, disease duration, lesion size, best-corrected visual acuity (BCVA), previous number of IVIs, and type of drug applied.

RESULTS

A total of 35 eyes of 35 patients (76.23 years ± 7.05 years) were included, and 21 eyes (60%) responded well to SRT. The annual injection rate decreased from 6.86 before SRT to 3.46 afterward, whereas BCVA improved from 0.49 logMAR at baseline to 0.37 logMAR at final follow-up. From a morphologic point of view, CMT and SFCT decreased by 71 μm and 37 μm, respectively, at 12-month follow-up compared to baseline. Of all investigated parameters, only SFCT proved to be significant, as a higher baseline SFCT was found to be a strong negative predictor for the number of IVIs needed after SRT (regression coefficient: -0.678; P < .001).

CONCLUSIONS

Baseline SFCT may help predict which patients with nAMD will respond more favorably to SRT. The authors found eyes with a thicker baseline SFCT needed fewer IVIs after SRT. [Ophthalmic Surg Lasers Imaging Retina. 2018;49:320-328.].

Retinal capillary perfusion: Spatial and temporal heterogeneity

The central role of the cardiovascular system is to maintain adequate capillary perfusion. The spatially and temporally heterogeneous nature of capillary perfusion has been reported in some organs. However, such heterogeneous perfusion properties have not been sufficiently explored in the retina. Arguably, spatial and temporal heterogeneity of capillary perfusion could be more predominant in the retina than that in other organs. This is because the retina is one of the highest metabolic demand neural tissues yet it has a limited blood supply due to optical requirements. In addition, the unique heterogeneous distribution of retinal neural cells within different layers and regions, and the significant heterogeneity of intraretinal oxygen distribution and consumption add to the complexity. Retinal blood flow distribution must match consumption of nutrients such as oxygen and glucose within the retina at the cellular level in order to effectively maintain cell survival and function. Sophisticated local blood flow control in the microcirculation is likely required to control the retinal capillary perfusion to supply local retinal tissue and accommodate temporal and spatial variations in metabolic supply and demand. The authors would like to update the knowledge of the retinal microvessel and capillary network and retinal oxidative metabolism from their own studies and the work of others. The coupling between blood supply and energy demands in the retina is particularly interesting. We will mostly describe information regarding the retinal microvessel network and retinal oxidative metabolism relevant to the spatial and temporal heterogeneity of capillary perfusion. We believe that there is significant and necessary spatial and temporal heterogeneity and active regulation of retinal blood flow in the retina, particularly in the macular region. Recently, retinal optical coherence tomography angiography (OCTA) has been widely used in ophthalmology, both experimentally and clinically. OCTA could be a valuable tool for examining retinal microvessel and capillary network structurally and has potential for determining retinal capillary perfusion and its control. We have demonstrated spatial and temporal heterogeneity of capillary perfusion in the retina both experimentally and clinically. We have also found close relationships between the smallest arterioles and capillaries within paired arterioles and venules and determined the distribution of smooth muscle cell contraction proteins in these vessels. Spatial and temporal heterogeneity of retinal capillary perfusion could be a useful parameter to determine retinal microvessel regulatory capability as an early assay for retinal vascular diseases. This topic will be of great interest, not only for the eye but also other organs. The retina could be the best model for such investigations. Unlike cerebral vessels, retinal vessels can be seen even at the capillary level. The purpose of this manuscript is to share our current understanding with the readers and encourage more researchers and clinicians to investigate this field. We begin by reviewing the general principles of microcirculation properties and the spatial and temporal heterogeneity of the capillary perfusion in other organs, before considering the special requirements of the retina. The local heterogeneity of oxygen supply and demand in the retina and the need to have a limited and well-regulated retinal circulation to preserve the transparency of the retina is discussed. We then consider how such a delicate balance of metabolic supply and consumption is achieved. Finally we discuss how new imaging methodologies such as optical coherence tomography angiography may be able to detect the presence of spatial and temporal heterogeneity of capillary perfusion in a clinical setting. We also provide some new information of the control role of very small arterioles in the modulation of retinal capillary perfusion which could be an interesting topic for further investigation.

Novel stem cell and gene therapy in diabetic retinopathy, age related macular degeneration, and retinitis pigmentosa

Degenerative retinal disease leads to significant visual morbidity worldwide. Diabetic retinopathy and macular degeneration are leading causes of blindness in the developed world. While current therapies for these diseases slow disease progression, stem cell and gene therapy may also reverse the effects of these, and other, degenerative retinal conditions. Novel therapies being investigated include the use of various types of stem cells in the regeneration of atrophic or damaged retinal tissue, the prolonged administration of neurotrophic factors and/or drug delivery, immunomodulation, as well as the replacement of mutant genes, and immunomodulation through viral vector delivery. This review will update the reader on aspects of stem cell and gene therapy in diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa and other less common inherited retinal dystrophies. These therapies include the use of adeno-associated viral vector-based therapies for treatment of various types of retinitis pigmentosa and dry age-related macular degeneration. Other potential therapies reviewed include the use of mesenchymal stem cells in local immunomodulation, and the use of stem cells in generating structures like three-dimensional retinal sheets for transplantation into degenerative retinas. Finally, aspects of stem cell and gene therapy in diabetic retinopathy, age-related macular degeneration, retinitis pigmentosa, and other less common inherited retinal dystrophies will be reviewed.

Proteomic Profiles in Advanced Age-Related Macular Degeneration Using an Aptamer-Based Proteomic Technology

Purpose

To explore top-ranked plasma proteins related to neovascular age-related macular degeneration (AMD) and geographic atrophy (GA), and explore pathways related to neovascular AMD and GA.

Methods

We conducted a pilot study of patients with neovascular AMD (n = 10), GA (n = 10), and age-matched cataract controls (n = 10) who were recruited into an AMD registry. We measured 4001 proteins in ethylenediaminetetraacetic acid plasma samples using an aptamer-based proteomic technology. Relative concentrations of each of 4001 proteins were log (base 2) transformed and compared between cases of neovascular AMD and GA versus controls using linear regression. Pathway analysis was conducted using pathways downloaded from Reactome.

Results

In this pilot study, higher levels of vinculin and lower levels of CD177 were found in patients with neovascular AMD compared with controls. Neuregulin-4 was higher and soluble intercellular adhesion molecule-1 was lower in patients with GA compared with controls. For neovascular AMD, cargo trafficking to the periciliary membrane, fibroblast growth factor receptor 3b ligand binding and activation, and vascular endothelial growth factor–related pathways were in the top ranked pathways. The top-ranked pathways for GA included several related to ErbB4 signaling.

Conclusions

We found different proteins and different pathways associated with neovascular AMD and GA. Vinculin and some of the top-ranked pathways have been previously associated with AMD, whereas others have not been described.

Translational Relevance

Biomarkers identified in plasma likely reflect systemic alterations in protein expression and may improve our understanding of the mechanisms leading to AMD.

Cell Therapy for Retinal Dystrophies: From Cell Suspension Formulation to Complex Retinal Tissue Bioengineering

Retinal degeneration is an irreversible phenomenon caused by various disease conditions including age-related macular degeneration (AMD) and retinitis pigmentosa (RP). During the course of these diseases, photoreceptors (PRs) are susceptible to degeneration due to their malfunctions or to a primary dysfunction of the retinal pigment epithelium (RPE). Once lost, these cells could not be endogenously regenerated in humans, and cell therapy to replace the lost cells is one of the promising strategies to recover vision. Depending on the nature of the primary defect and the stage of the disease, RPE cells, PRs, or both might be transplanted to achieve therapeutic effects. We describe in this review the current knowledge and recent progress to develop such approaches. The different cell sources proposed for cell therapy including human pluripotent stem cells are presented with their advantages and limits. Another critical aspect described herein is the pharmaceutical formulation of the end product to be delivered into the eye of patients. Finally, we also outline the future research directions in order to develop a complex multilayered retinal tissue for end-stage patients.

Celastrol protects human retinal pigment epithelial cells against hydrogen peroxide mediated oxidative stress, autophagy, and apoptosis through sirtuin 3 signal pathway

Age-related macular degeneration (AMD), one of the most common causes of visual impairment, often occurrs in the elderly in developed countries. Oxidative stress, autophagy, and apoptosis of retinal pigment epithelial (RPE) cells play roles in the pathogenesis of AMD. In the current study, the protective effect of celastrol against hydrogen peroxide (H₂ O₂ )-induced oxidative stress and apoptosis was investigated using a human RPE cell line (ARPE-19). H₂ O₂ inhibited ARPE-19 cells' survival and autophagy and induced their oxidative stress and apoptosis. Compared with the H₂ O₂ group, 3-(4,5-dimethylthiazol-2-yl)-2,5-diphenyl tetrazolium bromide (MTT) assay showed that celastrol increased ARPE-19 cells' survival in a dose- and time-dependent manner. Further, studies have suggested that celastrol has antioxidative stress and antiapoptosis effects in H₂ O₂ -treated ARPE-19 cells. Also, cell autophagy is activated by celastrol in H₂ O₂ -treated ARPE-19 cells. Reverse transcription polymerase chain reaction and Western blot showed that celastrol elevated the messenger RNA (mRNA) and protein expression of sirtuin 3 (SIRT3) in H₂ O₂ -induced ARPE-19 cells. Inhibition of the level of SIRT3 by SIRT3 small interfering RNA (siRNA) reversed the effects of celastrol on oxidative stress, autophagy, and apoptosis in H₂ O₂ -induced ARPE-19 cells. In conclusion, these observations suggest that celastrol activates the SIRT3 pathway in RPE cells and protects against H₂ O₂ -induced oxidative stress and apoptosis.

Stability, Cytotoxicity, and Retinal Pigment Epithelial Cell Binding of Hyaluronic Acid-Coated PLGA Nanoparticles Encapsulating Lutein

The application of lutein was limited due to water insolubility and susceptible to heat and light degradation. In this study, hyaluronic acid (HA)-coated PLGA nanoparticles encapsulating lutein were fabricated by a solvent displacement method to improve the physicochemical properties and the stability of lutein. A biphasic release profile of lutein was observed, following zero-order release kinetics. The physical stability of lutein stored at 4°C, 30°C, and 40°C for 30 days was enhanced when lutein was encapsulated in the nanoparticles. The degradation of lutein in PLGA NPs coated with HA was fitted to a second-order kinetic model. The rate constant increased with increasing storage temperature. The activation energy of lutein-NPs was 63.26 kJ/mol. The half-lives of lutein in PLGA-NPs were about 49, 4, and 2 days at a storage temperature of 4°C, 30°C, and 40°C, respectively. The results suggested that lutein-NPs should be stored at 4°C to prevent physical and chemical degradation. The photodegradation of lutein in NPs followed a second-order kinetic model. The rate constant was 0.0155 mg^-1 ml day^-1. Cell viability study revealed that HA-coated PLGA nanoparticles encapsulating lutein did not show toxicity against retinal pigment epithelial cells (ARPE-19). The NPs bound ARPE-19 cells in a time- and a dose-dependent manner. The binding efficiency of lutein-NPs decreased at higher concentrations, suggesting that the NPs might reach binding saturation capacity. In conclusion, HA-coated PLGA nanoparticles could be used to deliver lutein and improved physicochemical property of lutein. Graphical abstract ᅟ.

Correlation of optical coherence tomography angiography and microperimetry (MP3) features in wet age-related macular degeneration

PURPOSE

To evaluate and correlate the functional treatment response using microperimetry (MP3) with the morphological findings on optical coherence tomography angiography (OCTA) in wet AMD pre- and post-treatment with anti-vascular endothelial growth factor (VEGF). This was a single-centre prospective, interventional study.

METHODS

Patients with wet AMD were treated with 3 injections of intravitreal anti-VEGF at monthly intervals for 3 months and followed at 1, 2, 3, and 6 months postinjection. Using "overlay" features, morphologic characteristics of OCTA at the site of choroidal neovascular membrane (CNVM) lesion were analyzed and correlated functionally with MP3. Data were collected including visual acuity at presentation and follow-up with multimodal imaging features, treatment details, complications (if any), and treatment given for that complication. Descriptive observational analysis and paired t-test was used to compare the appearance of the neovascular network on OCTA imaging with retinal sensitivity on MP3.

RESULTS

OCTA in the pretreatment phase revealed CNVM as an abnormal vascular network arising from the choroid and invading the subretinal space. On MP3, decreased retinal sensitivity was observed corresponding to the area of CNVM. Post-treatment, OCTA revealed reduction in abnormal vascular network in 51 (91.07%) eyes that correlated with increased retinal sensitivity at the corresponding area on MP3. Statistical analysis showed baseline mean retinal sensitivity at the site of CNVM as 320.07 dB, which improved to 521.53 and 730.20 dB at 1 and 3 months postinjection follow-up, respectively.

CONCLUSION

Combining the findings of OCTA and MP3 using "overlay" features gives us precise information of structure-function correlation at presentation and also in response to treatment. It also helps to improve patient's compliance, confidence to treatment, and their understanding of the disease process as well.

Novel devices for studying acute and chronic mechanical stress in retinal pigment epithelial cells

Choroidal neovascularization (CNV) is a major cause of blindness in patients with age-related macular degeneration (AMD). Overexpression of vascular endothelial growth factor (VEGF), a potent angiogenic protein, by retinal pigment epithelial (RPE) cells is a key stimulator of CNV. Mechanical stress occurs during different stages of AMD and is a possible inducer of VEGF expression in RPE cells. However, robust and realistic approaches to studying acute and chronic mechanical stress under various AMD stages do not exist. The majority of previous work has studied cyclic stretching of RPE cells grown on flexible substrates, but an ideal model must be able to mimic localized and continuous stretching of the RPE as would occur in AMD in vivo. To bridge this gap, we developed two in vitro devices to model chronic and acute mechanical stress on RPE cells during different stages of AMD. In one device, high levels of continuous mechanical stress were applied to focal regions of the RPE monolayer by stretching the underlying silicon substrate to study the role of chronic mechanical stimulation. In the second device, RPE cells were grown on porous plastic substrates and acute stress was studied by stretching small areas. Using these devices, we studied the effect of mechanical stress on VEGF expression in RPE cells. Our results suggest that mechanical stress in RPE cells induces VEGF expression and promotes in vitro angiogenesis. These results confirm the hypothesis that mechanical stress is involved in the initiation and progression of CNV.

Multi-line Adaptive Perimetry (MAP): A New Procedure for Quantifying Visual Field Integrity for Rapid Assessment of Macular Diseases

Purpose

In order to monitor visual defects associated with macular degeneration (MD), we present a new psychophysical assessment called multiline adaptive perimetry (MAP) that measures visual field integrity by simultaneously estimating regions associated with perceptual distortions (metamorphopsia) and visual sensitivity loss (scotoma).

Methods

We first ran simulations of MAP with a computerized model of a human observer to determine optimal test design characteristics. In experiment 1, predictions of the model were assessed by simulating metamorphopsia with an eye-tracking device with 20 healthy vision participants. In experiment 2, eight patients (16 eyes) with macular disease completed two MAP assessments separated by about 12 weeks, while a subset (10 eyes) also completed repeated Macular Integrity Assessment (MAIA) microperimetry and Amsler grid exams.

Results

Results revealed strong repeatability of MAP and high accuracy, sensitivity, and specificity (0.89, 0.81, and 0.90, respectively) in classifying patient eyes with severe visual impairment. We also found a significant relationship in terms of the spatial patterns of performance across visual field loci derived from MAP and MAIA microperimetry. However, there was a lack of correspondence between MAP and subjective Amsler grid reports in isolating perceptually distorted regions.

Conclusions

These results highlight the validity and efficacy of MAP in producing quantitative maps of visual field disturbances, including simultaneous mapping of metamorphopsia and sensitivity impairment.

Translational Relevance

Future work will be needed to assess applicability of this examination for potential early detection of MD symptoms and/or portable assessment on a home device or computer.

The expression of adenosine receptors changes throughout light induced retinal degeneration in the rat

The modulation of adenosine receptors, A1 (A1R) and A2A (A2AR), is neuroprotective in different models of retinal injury. In order to understand the processes underlying retinal degeneration, we studied the expression of adenosine receptors in the retinas of control and continuously illuminated (CI) rats by qRT-PCR, Western blot (WB) and immunohistochemistry (IHC). Significant increases of A1R, A2AR, and A2BR mRNAs at 1, 5, and 7 days of CI (P < 0.0001) were observed by qRT-PCR. Also, a significant increase of A3R mRNA was detected after 5 and 7 days of CI. WB studies showed a significant rise of A1R on day 1 of CI and on days 5 and 7 (P < 0.0001), while A2AR increase was seen from 2 days of CI on (P < 0.001). After 1 day of CI, A1R immunoreactivity (A1R-IR) increased in ganglion cell layer, inner nuclear layer, and in both the outer and inner plexiform layers. After 2 days of CI, the A1R-IR went back to control levels. After 5 days of CI, a second rise in A1R, which persisted until 7 days of CI, was measured (P < 0.0001). A significant rise of A2aR immunoreactivity was also observed at day 2 of CI at GCL and INL and subsided at days 5 and 7 (P < 0.0001). The observed up-regulation of A1R after 1 day of CI, corresponds with the peak of oxidative stress; while the rise of A2aR at day 2 of CI, coincides with the massive apoptosis of photoreceptors. We postulate that an early modulation of adenosine receptors could delay or prevent the degeneration of photoreceptors.

Retinal pigment epithelium-derived transforming growth factor-β2 inhibits the angiogenic response of endothelial cells by decreasing vascular endothelial growth factor receptor-2 expression

Transforming growth factor-β (TGF-β) is a multifunctional cytokine that is known to modulate various aspects of endothelial cell (EC) biology. Retinal pigment epithelium (RPE) is important for regulating angiogenesis of choriocapillaris and one of the main cell sources of TGF-β secretion, particularly TGF-β2. However, it is largely unclear whether and how TGF-β2 affects angiogenic responses of ECs. In the current study, we demonstrated that TGF-β2 reduces vascular endothelial growth factor receptor-2 (VEGFR-2) expression in ECs and thereby inhibits vascular endothelial growth factor (VEGF) signaling and VEGF-induced angiogenic responses such as EC migration and tube formation. We also demonstrated that the reduction of VEGFR-2 expression by TGF-β2 is due to the suppression of JNK signaling. In coculture of RPE cells and ECs, RPE cells decreased VEGFR-2 levels in ECs and EC migration. In addition, we showed that TGF-β2 derived from RPE cells is involved in the reduction of VEGFR-2 expression and inhibition of EC migration. These results suggest that TGF-β2 plays an important role in inhibiting the angiogenic responses of ECs during the interaction between RPE cells and ECs and that angiogenic responses of ECs may be amplified by a decrease in TGF-β2 expression in RPE cells under pathologic conditions.

Quantitative Evaluation of Choroidal Neovascularization under Pro Re Nata Anti-Vascular Endothelial Growth Factor Therapy with OCT Angiography

PURPOSE

To use optical coherence tomography angiography (OCTA) derived quantitative metrics to assess the response of choroidal neovascularization to pro-re-nata (PRN) anti-endothelial growth factor (anti-VEGF) treatment in neovascular age-related macular degeneration (AMD).

DESIGN

Prospective longitudinal cohort study.

PARTICIPANTS

Fourteen eyes from 14 study participants with treatment-naïve neovascular AMD were enrolled.

METHODS

Subjects were evaluated monthly and treated with intravitreal anti-VEGF agents under a PRN protocol for one year. At each visit, two 3×3 mm2 OCTA scans were obtained. Custom image processing was applied to segment the outer retinal slab, suppress projection artifact, and automatically detect CNV. CNV membrane area (mm2) and CNV vessel area (mm2) was calculated.

MAIN OUTCOMES

Individual and mean CNV membrane area and CNV vessel area at each visit; within-visit repeatability determined by coefficient of variation.

RESULTS

Eight eyes had entire CNV within 3×3 mm2 scanning area and had adequate image quality for CNV quantification. One case (case #2) was excluded from analysis due to the presence of a large subretinal hemorrhage overlying the CNV membrane. In the remaining cases, CNV vessel area was reduced by 39%, 50%, 43%, and 41% at months 1, 3, 6, and 12 respectively. CNV membrane area was reduced by 39%, 51%, 54%, and 45% at months 1, 3, 6, and 12. At month 6, mean change from baseline was not statistically significant for CNV vessel area, while it was statistically significant for CNV membrane area. Neither metric was significantly different compared to baseline at month 12. Individual analyses revealed each CNV had a unique response under PRN treatment. Within-visit repeatability was was 7.96% (coefficient of variation) for CNV vessel area and 7.37% for CNV membrane area.

CONCLUSIONS

In this small exploratory study of CNV response to PRN anti-VEGF treatment, both CNV vessel area and membrane area were reduced compared to baseline after three months. After one year of follow-up, these reductions were no longer statistically significant. When anti-VEGF treatment was held, increasing CNV vessel area over time often resulted in exudation, but it was not possible to exactly when exudation occurs.

Effects of blue-light irradiation during dental treatment

In dentistry, blue light is widely used for tooth bleaching and restoration procedures involving composite resin. In addition, many dentists use magnification loupes to enable them to provide more accurate dental treatment. Therefore, the use of light is indispensable in dental treatment. However, light can cause various toxicities, and thermal injuries caused by light irradiation are regarded as particularly important. In recent years, the eye damage and non-thermal injuries caused by blue light, the so-called "blue light hazard", have gained attention. Unfortunately, much of the research in this field has just begun, but our recent findings demonstrated that blue-light irradiation generates reactive oxygen species (ROS) and induces oxidative stress in oral tissue. However, they also showed that such oxidative stress is inhibited by antioxidants. There have not been any reports that suggested that the ROS-induced phototoxicity associated with blue-light irradiation causes direct clinical damage, but some disorders are caused by the accumulation of ROS. Therefore, it is presumed that it is necessary to suppress the accumulation of oxidative stressors in oral tissues during treatment. In the future, we have to promote discussion about the suppression of phototoxicity in dentistry, including concerning the use of antioxidants to protect against phototoxic damage.

Subretinal macrophages produce classical complement activator C1q leading to the progression of focal retinal degeneration

BACKGROUND

The role of the alternative complement pathway and its mediation by retinal microglia and macrophages, is well-established in the pathogenesis of Age-Related Macular Degeneration (AMD). However, the contribution of the classical complement pathway towards the progression of retinal degenerations is not fully understood, including the role of complement component 1q (C1q) as a critical activator molecule of the classical pathway. Here, we investigated the contribution of C1q to progressive photoreceptor loss and neuroinflammation in retinal degenerations.

METHODS

Wild-type (WT), C1qa knockout (C1qa^-/-) and mice treated with a C1q inhibitor (ANX-M1; Annexon Biosciences), were exposed to photo-oxidative damage (PD) and were observed for progressive lesion development. Retinal function was assessed by electroretinography, followed by histological analyses to assess photoreceptor degeneration. Retinal inflammation was investigated through complement activation, macrophage recruitment and inflammasome expression using western blotting, qPCR and immunofluorescence. C1q was localised in human AMD donor retinas using immunohistochemistry.

RESULTS

PD mice had increased levels of C1qa which correlated with increasing photoreceptor cell death and macrophage recruitment. C1qa^-/- mice did not show any differences in photoreceptor loss or inflammation at 7 days compared to WT, however at 14 days after the onset of damage, C1qa^-/- retinas displayed less photoreceptor cell death, reduced microglia/macrophage recruitment to the photoreceptor lesion, and higher visual function. C1qa^-/- mice displayed reduced inflammasome and IL-1β expression in microglia and macrophages in the degenerating retina. Retinal neutralisation of C1q, using an intravitreally-delivered anti-C1q antibody, reduced the progression of retinal degeneration following PD, while systemic delivery had no effect. Finally, retinal C1q was found to be expressed by subretinal microglia/macrophages located in the outer retina of early AMD donor eyes, and in mouse PD retinas.

CONCLUSIONS

Our data implicate subretinal macrophages, C1q and the classical pathway in progressive retinal degeneration. We demonstrate a role of local C1q produced by microglia/macrophages as an instigator of inflammasome activation and inflammation. Crucially, we have shown that retinal C1q neutralisation during disease progression may slow retinal atrophy, providing a novel strategy for the treatment of complement-mediated retinal degenerations including AMD.

Polymorphisms in PEDF linked with the susceptibility to age-related macular degeneration: A case-control study

To study the relationship between pigment epithelium-derived factor (PEDF) rs1136287, rs1894286 polymorphisms and the risk of age-related macular degeneration (AMD) in northern Chinese populations.The study was carried out on case-control methods. Ninety-six patients with AMD and 98 health controls were recruited who were matched with the former by age and gender, rs1136287 and rs1894286 were genotyped by polymerase chain reaction-restriction fragment length polymorphism (PCR-RFLP). Hardy-Weinberg equilibrium (HWE) was also checked by χ test. The distribution frequencies of genotype, allele, and haplotype were calculated by direct counting method. The genotype, allele, and haplotype distribution differences between the case and control groups were analyzed by chi-square test, and odds ratio (OR) and 95% confidence interval (CI) was used to express the relative risk of AMD in northern Chinese populations. The linkage disequilibrium (LD) and haplotype analyses were conducted with Haploview software.The genotype and allele distribution frequencies in rs1136287 were obviously between in cases and controls (P < .05). TT genotype might lead to 3.24 times risk of AMD occurrence compared with CC genotype (OR = 3.24, 95% CI = 1.26-8.32), and C allele also played an increased risk role in the attack of AMD (OR = 1.58, 95% CI = 1.06-2.38). The T-C haplotype frequency of rs1136287-rs1894286 in PEDF were significantly correlated to the increased susceptibility to AMD (OR = 1.57, 95% CI = 1.02-2.40).The rs1136287 polymorphism in PEDF may be related to the occurrence risk of AMD. Additionally, a haplotype is also a non-ignorable risk factor.

AGE-RELATED MACULAR DEGENERATION-ASSOCIATED PERIPAPILLARY CHOROIDAL NEOVASCULARIZATION IN THE ERA OF ANTI-VASCULAR ENDOTHELIAL GROWTH FACTOR THERAPY

PURPOSE

To characterize the natural history and response of age-related macular degeneration-associated peripapillary choroidal neovascularization to anti-vascular endothelial growth factor therapy.

METHODS

This was a retrospective case series of patients with peripapillary choroidal neovascularization secondary to neovascular age-related macular degeneration. All patients underwent complete ophthalmologic examination and retinal imaging including fluorescein angiography and spectral domain optical coherence tomography at each visit. Eyes with subretinal or intraretinal macular fluid were treated with anti-vascular endothelial growth factor monotherapy using a modified as-needed treatment algorithm.

RESULTS

Thirty-three eyes of 27 patients were included. The median age was 82 years (range, 62-94), and the median duration of follow-up was 65 months (range, 6-165). Fourteen eyes (58%) without fovea-involving fluid at baseline subsequently developed exudation after a median observation period of 16 months (range, 4-107). Ten of 24 eyes (42%) without initial macular fluid remained dry during the entire follow-up. The median number of injections required until complete fluid reabsorption was 3 (range, 1-21) during the first treatment cycle. The median time to fluid recurrence was 6 months (range, 3-74).

CONCLUSION

Peripapillary choroidal neovascularization secondary to wet age-related macular degeneration has a slow progression, may not require treatment for a prolonged period, and responds rapidly to anti-vascular endothelial growth factor treatment with good visual outcomes.

Extended HLA-G haplotypes in patients with age-related macular degeneration

The study aims to determine if genetic polymorphisms in the human leukocyte antigen (HLA)-G gene are associated with age-related macular degeneration (AMD). HLA-G is important for immunological tolerance, and it is also known to have angiogenic effects. Polymorphisms in the 5'-upstream regulatory region (URR) and 3'-untranslated region (UTR) of HLA-G have been associated with a number of diseases, especially with respect to a 14 bp insertion/deletion (ins/del) polymorphism in the 3'UTR. Full gene sequencing was performed on a cohort of 146 AMD patients and 63 healthy controls aged 60 years or older and HLA-G haplotypes were determined. Analyses were performed on a publicly available gene expression dataset from the NCBI GEO database (accession number GSE29801) from which expression data for HLA-G, -C and -A were extracted. Analysis of the GEO dataset showed that both HLA-G and -C was expressed in the back of the eye and that expression was upregulated in the macular area of AMD. No differences were observed between patients and controls when analysing the distribution of haplotypes in the HLA-G promoter, coding region, 3'UTR or the 14 bp ins/del polymorphism of the 3'UTR. The increased expression of HLA-G in the macula of AMD patients indicates a role of HLA-G in the micro environment as part of the AMD pathogenesis. This is supported by the expression of HLA-C, which has previously been shown to play a role in AMD. The HLA-G haplotype distribution did not display any differences between AMD patients and controls. This article is protected by copyright. All rights reserved.

Adenosine A1 receptor: A neuroprotective target in light induced retinal degeneration

Light induced retinal degeneration (LIRD) is a useful model that resembles human retinal degenerative diseases. The modulation of adenosine A1 receptor is neuroprotective in different models of retinal injury. The aim of this work was to evaluate the potential neuroprotective effect of the modulation of A1 receptor in LIRD. The eyes of rats intravitreally injected with N6-cyclopentyladenosine (CPA), an A1 agonist, which were later subjected to continuous illumination (CI) for 24 h, showed retinas with a lower number of apoptotic nuclei and a decrease of Glial Fibrillary Acidic Protein (GFAP) immunoreactive area than controls. Lower levels of activated Caspase 3 and GFAP were demonstrated by Western Blot (WB) in treated animals. Also a decrease of iNOS, TNFα and GFAP mRNA was demonstrated by RT-PCR. A decrease of Iba 1⁺/MHC-II⁺ reactive microglial cells was shown by immunohistochemistry. Electroretinograms (ERG) showed higher amplitudes of a-wave, b-wave and oscillatory potentials after CI compared to controls. Conversely, the eyes of rats intravitreally injected with dipropylcyclopentylxanthine (DPCPX), an A1 antagonist, and subjected to CI for 24 h, showed retinas with a higher number of apoptotic nuclei and an increase of GFAP immunoreactive area compared to controls. Also, higher levels of activated Caspase 3 and GFAP were demonstrated by Western Blot. The mRNA levels of iNOS, nNOS and inflammatory cytokines (IL-1β and TNFα) were not modified by DPCPX treatment. An increase of Iba 1⁺/MHC-II⁺ reactive microglial cells was shown by immunohistochemistry. ERG showed that the amplitudes of a-wave, b-wave, and oscillatory potentials after CI were similar to control values. A single pharmacological intervention prior illumination stress was able to swing retinal fate in opposite directions: CPA was neuroprotective, while DPCPX worsened retinal damage. In summary, A1 receptor agonism is a plausible neuroprotective strategy in LIRD.