The complexities underlying age-related macular degeneration： could amyloid beta play an important role？

Age-related macular degeneration(AMD) causes irreversible loss of central vision for which there is no effective treatment. Incipient pathology is thought to occur in the retina for many years before AMD manifests from midlife onwards to affect a large proportion of the elderly. Although genetic as well as non-genetic/environmental risks are recognized, its complex aetiology makes it difficult to identify susceptibility, or indeed what type of AMD develops or how quickly it progresses in different individuals. Here we summarize the literature describing how the Alzheimer's-linked amyloid beta(Aβ) group of misfolding proteins accumulate in the retina. The discovery of this key driver of Alzheimer's disease in the senescent retina was unexpected and surprising, enabling an altogether different perspective of AMD. We argue that Aβ fundamentally differs from other substances which accumulate in the ageing retina, and discuss our latest findings from a mouse model in which physiological amounts of Aβ were subretinally-injected to recapitulate salient features of early AMD within a short period. Our discoveries as well as those of others suggest the pattern of Aβ accumulation and pathology in donor aged/AMD tissues are closely reproduced in mice, including late-stage AMD phenotypes, which makes them highly attractive to study dynamic aspects of Aβ-mediated retinopathy. Furthermore, we discuss our findings revealing how Aβ behaves at single-cell resolution, and consider the long-term implications for neuroretinal function. We propose Aβ as a key element in switching to a diseased retinal phenotype, which is now being used as a biomarker for latestage AMD.

Research progress of age-related macular degeneration related gene polymorphism at high altitude

Age-related macular degeneration(AMD)is a kind of progressive eye disease that seriously damages vision,and it is one of the important causes of blindness.In recent years,a large number of studies have found that there is a significant correlation between genetic factors and the occurrence and development of AMD.The study of gene polymorphism provides new ideas and directions for clinical diagnosis and treatment.In this paper,we will make a brief review of the research progress related to complement factor H(CFH),serine protease(HtrA1),age-related macular degeneration susceptibility factor 2(ARMS2)and vascular endothelial growth factor(VEGF)gene single nucleotide polymorphisms(SNP).

Amyloid beta deposition related retinal pigment epithelium cell impairment and subretinal microglia activation in aged APPswePS1 transgenic mice

AIM:To identify the pathological role of amyloid beta(Aβ) deposition in retinal degeneration,and explore Aβ deposition on the retinal pigment epithelium cells(RPE) layer and the associated structural and functional changes in Alzheimer's disease transgenic mice.METHODS:RPE changes in the eyes of APPswe/PS1 transgenic and none transgenic(NTG) mice over 20 months old were examined.Histological changes were investigated via hematoxylin and eosin(H&E) staining and transmission electron microscopy(TEM) examination,whereas the expression of amyloid precursor protein(APP),Aβ,Zonula occludens-1(ZO-1) and Ionized calcium binding adaptor molecule-1(IBA-1) were investigated using immunohistochemistry and immunofluorescence techniques.All of the obtained results were quantitatively and statistically analyzed.RESULTS:In aged transgenic mice,an APP-positive immunoreaction and Aβ deposition were detected on the RPE layer but were undetectable in NTG mice.The RPE demonstrated some vacuole changes,shortened basal infoldings and basal deposition in histopathological examination and TEM tests,wherein irregular shapes were indicated by ZO-1 disorganization through fluorescence.Furthermore,IBA-1 positive cells were observed to have accumulated and infiltrated into the RPE layer and localized beneath the RPE/Bruch's membrane(Br M) complex,which was accompanied by an increase in BrM thickness in aged transgenic mice in comparison to NTG mice.The IBA-1 positive cells were found to be co-stained with Aβ deposition on the RPE flat mounts.CONCLUSION:The observed Aβ deposition in the RPE layer may cause RPE dysfunction,which is associated with microglia cells infiltration into the retina of aged transgenic mice,suggesting that Aβ deposition probably plays a significant role in RPE-related degenerative disease.

Blue light induced retinal oxidative stress:Implications for macular degeneration

A number of studies have shown that oxidative stress can be harmful for the retina. The real causal circumstances that lead to degenerative diseases like age related macular degeneration remain obscure. Whether light induced radical stress is a direct interaction of light with photoreceptors or a secondary mechanism within the pigment epithelium or choroid is in discussion. Among the molecular mechanisms involved are production of reactive oxygen species(ROS), secondary lipid peroxidation, protein oxidation and DNA-damage. The initial trigger to write this review was first a recent finding of our group that the photoreceptor outer segments produce great amounts of ROS and second the detection of ectopic enzymes of the respiratory chainlocalized there- in addition to the hitherto known ROS sources like the visual pigments with their intermediates and the photoreceptor mitochondria harbouring the respiratory chain.

Big DNA as a tool to dissect an age-related macular degeneration-associated haplotype

Age-related Macular Degeneration(AMD)is a leading cause of blindness in the developed world,especially in aging populations,and is therefore an important target for new therapeutic development.Recently,there have been several studies demonstrating strong associations between AMD and sites of heritable genetic variation at multiple loci,including a highly significant association at 10q26.The 10q26 risk region contains two genes,HTRA1 and ARMS2,both of which have been separately implicated as causative for the disease,as well as dozens of sites of non-coding variation.To date,no studies have successfully pinpointed which of these variant sites are functional in AMD,nor definitively identified which genes in the region are targets of such regulatory variation.In order to efficiently decipher which sites are functional in AMD phenotypes,we describe a general framework for combinatorial assembly of large‘synthetic haplotypes’along with delivery to relevant disease cell types for downstream functional analysis.We demonstrate the successful and highly efficient assembly of a first-draft 119kb wild-type‘assemblon’covering the HTRA1/ARMS2 risk region.We further propose the parallelized assembly of a library of combinatorial variant synthetic haplotypes covering the region,delivery and analysis of which will identify functional sites and their effects,leading to an improved understanding of AMD development.We anticipate that the methodology proposed here is highly generalizable towards the difficult problem of identifying truly functional variants from those discovered via GWAS or other genetic association studies.

Management of subretinal hemorrhage

Subretinal hemorrhage is a vision threatening complication of exudative age related macular degeneration(AMD) and polypoidal choroidal vasculopathy(PCV). Timely removal or displacement of subretinal hemorrhage from the central macula, ideally within 7 to 10 days after onset, is critical to allowing potential recovery of vision. Surgical techniques with the use of a bubble to displace the subretinal hemorrhage can now be performed with tissue plasminogen activator to lyze the blood and with or without vitrectomy.

AB041.The implication of miRNA let-7f in retinal pigment epithelium degeneration under oxidative stress

Background:Age-related macular degeneration(AMD)is the most suspected cause of vision loss in the elderly.Given the considerable evidence,oxidative stress is thought to be a primary contributing factor to AMD.Retinal pigment epithelium(RPE)could be detrimentally compromised by oxidative stress along which blebs called retinal microparticles(RMPs)start to shed.In continue these particles would be taken by retina,causing RPE senescence,dysfunction and ultimately cell death.Along with the intracellular damages,accumulative deposit of microparticles in subretinal region can cause most known histological hallmark of dry AMD namely drusen.Based on our preliminary study,of 20 present miRNAs,Let-7f is the most abundant microRNAs in RMPs.As the accused substrate of RMPs through which retina function is compromised has yet to be well understood,we aimed to investigate pathophysiological role of let-7f and specific signaling triggered in RPE dysfunction.In brief,the principal objective is to further understand how RMPs implicate in RPE dysfunction.Methods:By oxidative stress inducing,RMPs were isolated from cultured ARPE-19 cells.We considered the effect of RMPs on ARPE-19 cells viability using MTT assay.In addition,to see whether RMPs effect could be ascribed to let-7f,ARPE-19 cells were transfected by carrier containing miRNA Let-7f.These transfected cells were then subjected senescence(β-galactosidase)and cell cycle assay to explore the molecular events responsible for Let-7f induced RPE cell dysfunction.Results:Regarding result we found that RMPs adversely affected RPE cell growth and resulted in significant decrease(≥30%)in cell viability.Let-7f-treated cells also revealed considerable increases of the senescence-associatedβ-galactosidase activity.Alongside RMPs impact,let-7f treatment group also showed similar result in cell growth.Conclusions:To the best of our knowledge,RPE cells uptake microparticles derived from oxidative-injured retinal cells,deteriorating integrity of vision compartments.Not only these finding would suggest that RMP’s impression likely corresponds to the miRNA let-7f,but introduce Let-7f as a mediator exacerbating the oxidative damages to RPE cells.This undesirable interplay is followed probably by dry AMD.Taken together,it seems by finding involved downstream pathways under RMPs pathogenesis,we can inhibit AMD disease in the early stage as well.In this line,we plan to investigate consecutive effect of RMP-associated miRNA inhibition in oxidative damage of retinal pigment epithelium.