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Zareba M, Skumatz CMB, Sarna TJ, Burke JM. Photic injury to cultured RPE varies among individual cells in proportion to their endogenous lipofuscin content as modulated by their melanosome content. Invest Ophthalmol Vis Sci 2014; 55:4982-90. [PMID: 25034597 DOI: 10.1167/iovs.14-14310] [Citation(s) in RCA: 15] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022] Open
Abstract
PURPOSE We determined whether photic stress differentially impairs organelle motility of RPE lipofuscin and melanin granules, whether lethal photic stress kills cells in proportion to lipofuscin abundance, and whether killing is modulated by melanosome content. METHODS Motility of endogenous lipofuscin and melanosome granules within the same human RPE cells in primary culture was quantified by real-time imaging during sublethal blue light irradiation. Cell death during lethal irradiation was quantified by dynamic imaging of the onset of nuclear propidium iodide fluorescence. Analyzed were individual cells containing different amounts of autofluorescent lipofuscin, or similar amounts of lipofuscin and a varying content of phagocytized porcine melanosomes, or phagocytized black latex beads (control for light absorbance). RESULTS Lipofuscin granules and melanosomes showed motility slowing with mild irradiation, but slowing was greater for lipofuscin. On lethal irradiation, cell death was earlier in cells with higher lipofuscin content, but delayed by the copresence of melanosomes. Delayed death did not occur with black beads, suggesting that melanosome protection was due to properties of the biological granule, not simple screening. CONCLUSIONS Greater organelle motility slowing of the more photoreactive lipofuscin granule compared to melanosomes suggests that lipofuscin mediates mild photic injury within RPE cells. With lethal light stress endogenous lipofuscin mediates killing, but the effect is cell autonomous and modulated by coincident melanosome content. Developing methods to quantify the frequency of individual cells with combined high lipofuscin and low melanosome content may have value for predicting the photic stress susceptibility of the RPE monolayer in situ.
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Affiliation(s)
- Mariusz Zareba
- Department of Ophthalmology, Eye Institute, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Christine M B Skumatz
- Department of Ophthalmology, Eye Institute, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
| | - Tadeusz J Sarna
- Department of Biophysics, Faculty of Biochemistry, Biophysics and Biotechnology, Jagiellonian University, Krakow, Poland
| | - Janice M Burke
- Department of Ophthalmology, Eye Institute, Medical College of Wisconsin, Milwaukee, Wisconsin, United States
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Ach T, Huisingh C, McGwin G, Messinger JD, Zhang T, Bentley MJ, Gutierrez DB, Ablonczy Z, Smith RT, Sloan KR, Curcio CA. Quantitative autofluorescence and cell density maps of the human retinal pigment epithelium. Invest Ophthalmol Vis Sci 2014; 55:4832-41. [PMID: 25034602 DOI: 10.1167/iovs.14-14802] [Citation(s) in RCA: 166] [Impact Index Per Article: 16.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/28/2023] Open
Abstract
PURPOSE Lipofuscin (LF) accumulation within RPE cells is considered pathogenic in AMD. To test whether LF contributes to RPE cell loss in aging and to provide a cellular basis for fundus autofluorescence (AF) we created maps of human RPE cell number and histologic AF. METHODS Retinal pigment epithelium-Bruch's membrane flat mounts were prepared from 20 donor eyes (10 ≤ 51 and 10 > 80 years; postmortem: ≤4.2 hours; no retinal pathologies), preserving foveal position. Phalloidin-binding RPE cytoskeleton and LF-AF (488-nm excitation) were imaged at up to 90 predefined positions. Maps were assembled from 83,330 cells in 1470 locations. From Voronoi regions representing each cell, the number of neighbors, cell area, and total AF intensity normalized to an AF standard was determined. RESULTS Highly variable between individuals, RPE-AF increases significantly with age. A perifoveal ring of high AF mirrors rod photoreceptor topography and fundus-AF. Retinal pigment epithelium cell density peaks at the fovea, independent of age, yet no net RPE cell loss is detectable. The RPE monolayer undergoes considerable lifelong re-modeling. The relationship of cell size and AF, a surrogate for LF concentration, is orderly and linear in both groups. Autofluorescence topography differs distinctly from the topography of age-related rod loss. CONCLUSIONS Digital maps of quantitative AF, cell density, and packing geometry provide metrics for cellular-resolution clinical imaging and model systems. The uncoupling of RPE LF content, cell number, and photoreceptor topography in aging challenges LF's role in AMD.
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Affiliation(s)
- Thomas Ach
- University of Alabama at Birmingham, Department of Ophthalmology, Birmingham, Alabama, United States
| | - Carrie Huisingh
- University of Alabama at Birmingham, Department of Ophthalmology, Birmingham, Alabama, United States
| | - Gerald McGwin
- University of Alabama at Birmingham, Department of Ophthalmology, Birmingham, Alabama, United States University of Alabama at Birmingham, Department of Epidemiology, Birmingham, Alabama, United States
| | - Jeffrey D Messinger
- University of Alabama at Birmingham, Department of Ophthalmology, Birmingham, Alabama, United States
| | - Tianjiao Zhang
- University of Alabama at Birmingham, Department of Ophthalmology, Birmingham, Alabama, United States
| | - Mark J Bentley
- University of Alabama at Birmingham, Department of Computer and Information Sciences, Birmingham, Alabama, United States
| | - Danielle B Gutierrez
- Center for Coastal Studies, Texas A&M University-Corpus Christi, Corpus Christi, Texas, United States
| | - Zsolt Ablonczy
- Medical University of South Carolina, Department of Ophthalmology, Charleston, South Carolina, United States
| | - R Theodore Smith
- New York University School of Medicine, Department of Ophthalmology, New York, New York, United States
| | - Kenneth R Sloan
- University of Alabama at Birmingham, Department of Computer and Information Sciences, Birmingham, Alabama, United States
| | - Christine A Curcio
- University of Alabama at Birmingham, Department of Ophthalmology, Birmingham, Alabama, United States
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103
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Palczewska G, Golczak M, Williams DR, Hunter JJ, Palczewski K. Endogenous fluorophores enable two-photon imaging of the primate eye. Invest Ophthalmol Vis Sci 2014; 55:4438-47. [PMID: 24970255 DOI: 10.1167/iovs.14-14395] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.9] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022] Open
Abstract
PURPOSE Noninvasive two-photon imaging of a living mammalian eye can reveal details of molecular processes in the retina and RPE. Retinyl esters and all-trans-retinal condensation products are two types of retinoid fluorophores present in these tissues. We measured the content of these two types of retinoids in monkey and human eyes to validate the potential of two-photon imaging for monitoring retinoid changes in human eyes. METHODS Two-photon microscopy (TPM) was used to visualize excised retina from monkey eyes. Retinoid composition and content in human and monkey eyes were quantified by HPLC and mass spectrometry (MS). RESULTS Clear images of inner and outer segments of rods and cones were obtained in primate eyes at different eccentricities. Fluorescence spectra from outer segments revealed a maximum emission at 480 nm indicative of retinols and their esters. In cynomolgus monkey and human retinal extracts, retinyl esters existed predominantly in the 11-cis configuration along with notable levels of 11-cis-retinol, a characteristic of cone-enriched retinas. Average amounts of di-retinoid-pyridinium-ethanolamine (A2E) in primate and human eyes were 160 and 225 pmol/eye, respectively. CONCLUSIONS These data show that human retina contains sufficient amounts of retinoids for two-photon excitation imaging. Greater amounts of 11-cis-retinyl esters relative to rodent retinas contribute to the fluorescence signal from both monkey and human eyes. These observations indicate that TPM imaging found effective in mice could detect early age- and disease-related changes in human retina.
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Affiliation(s)
| | - Marcin Golczak
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, United States
| | - David R Williams
- Center for Visual Science, University of Rochester, Rochester, New York, United States The Institute of Optics, University of Rochester, Rochester, New York, United States
| | - Jennifer J Hunter
- Center for Visual Science, University of Rochester, Rochester, New York, United States Flaum Eye Institute, University of Rochester, Rochester, New York, United States Department of Biomedical Engineering, University of Rochester, Rochester, New York, United States
| | - Krzysztof Palczewski
- Department of Pharmacology, Case Western Reserve University, Cleveland, Ohio, United States
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104
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Höhn A, Jung T, Grune T. Pathophysiological importance of aggregated damaged proteins. Free Radic Biol Med 2014; 71:70-89. [PMID: 24632383 DOI: 10.1016/j.freeradbiomed.2014.02.028] [Citation(s) in RCA: 91] [Impact Index Per Article: 9.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/02/2014] [Revised: 02/28/2014] [Accepted: 02/28/2014] [Indexed: 02/06/2023]
Abstract
Reactive oxygen species (ROS) are formed continuously in the organism even under physiological conditions. If the level of ROS in cells exceeds the cellular defense capacity, components such as RNA/DNA, lipids, and proteins are damaged and modified, thus affecting the functionality of organelles as well. Proteins are especially prominent targets of various modifications such as oxidation, glycation, or conjugation with products of lipid peroxidation, leading to the alteration of their biological function, nonspecific interactions, and the production of high-molecular-weight protein aggregates. To ensure the maintenance of cellular functions, two proteolytic systems are responsible for the removal of oxidized and modified proteins, especially the proteasome and organelles, mainly the autophagy-lysosomal systems. Furthermore, increased protein oxidation and oxidation-dependent impairment of proteolytic systems lead to an accumulation of oxidized proteins and finally to the formation of nondegradable protein aggregates. Accordingly, the cellular homeostasis cannot be maintained and the cellular metabolism is negatively affected. Here we address the current knowledge of protein aggregation during oxidative stress, aging, and disease.
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Affiliation(s)
- Annika Höhn
- Department of Nutritional Toxicology, Institute of Nutrition, Friedrich-Schiller-University Jena, 07743 Jena, Germany
| | - Tobias Jung
- Department of Nutritional Toxicology, Institute of Nutrition, Friedrich-Schiller-University Jena, 07743 Jena, Germany
| | - Tilman Grune
- Department of Nutritional Toxicology, Institute of Nutrition, Friedrich-Schiller-University Jena, 07743 Jena, Germany.
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105
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Accumulation of modified proteins and aggregate formation in aging. Exp Gerontol 2014; 57:122-31. [PMID: 24877899 DOI: 10.1016/j.exger.2014.05.016] [Citation(s) in RCA: 54] [Impact Index Per Article: 5.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/01/2014] [Revised: 05/22/2014] [Accepted: 05/26/2014] [Indexed: 12/22/2022]
Abstract
Increasing cellular damage during the aging process is considered to be one factor limiting the lifespan of organisms. Besides the DNA and lipids, proteins are frequent targets of non-enzymatic modifications by reactive substances including oxidants and glycating agents. Non-enzymatic protein modifications may alter the protein structure often leading to impaired functionality. Although proteolytic systems ensure the removal of modified proteins, the activity of these proteases was shown to decline during the aging process. The additional age-related increase of reactive compounds as a result of impaired antioxidant systems leads to the accumulation of damaged proteins and the formation of protein aggregates. Both, non-enzymatic modified proteins and protein aggregates impair cellular functions and tissue properties by a variety of mechanisms. This is increasingly important in aging and age-related diseases. In this review, we will give an overview on oxidation and glycation of proteins and the function of modified proteins in aggregate formation. Furthermore, their effects as well as their role in aging and age-related diseases will be highlighted.
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106
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Holz FG, Strauss EC, Schmitz-Valckenberg S, van Lookeren Campagne M. Geographic Atrophy. Ophthalmology 2014; 121:1079-91. [DOI: 10.1016/j.ophtha.2013.11.023] [Citation(s) in RCA: 207] [Impact Index Per Article: 20.7] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/25/2013] [Revised: 11/08/2013] [Accepted: 11/11/2013] [Indexed: 12/12/2022] Open
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Poliakov E, Strunnikova NV, Jiang JK, Martinez B, Parikh T, Lakkaraju A, Thomas C, Brooks BP, Redmond TM. Multiple A2E treatments lead to melanization of rod outer segment-challenged ARPE-19 cells. Mol Vis 2014; 20:285-300. [PMID: 24644403 PMCID: PMC3955416] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2013] [Accepted: 03/11/2014] [Indexed: 11/07/2022] Open
Abstract
PURPOSE Daily phagocytosis of outer segments (OSs) and retinoid recycling by the RPE lead to the accumulation of storage bodies in the RPE containing autofluorescent lipofuscin, which consists of lipids and bisretinoids such as A2E and its oxidation products. Accumulation of A2E and its oxidation products is implicated in the pathogenesis of several retinal degenerative diseases. However, A2E accumulates in the RPE during normal aging. In this study, we used a cell model to determine the homeostatic mechanisms of RPE cells in response to A2E accumulation. METHODS To distinguish between pathologic and normal responses of the RPE to A2E accumulation, we treated established ARPE-19 cells (cultured for 3 weeks after reaching confluence) with low micromolar amounts of A2E for several weeks. We compared the lysosomal function, lysosomal pH, degree of OS digestion, and melanization of the treated cells to untreated control cells in response to a challenge of purified rod OSs (ROSs). A2E was analyzed with high-performance liquid chromatography (HPLC); and A2E and melanin were identified with mass spectrometry. RESULTS We found that post-confluent ARPE-19 cells took up and accumulated A2E under dim light conditions. Spectral analysis of the HPLC separations and mass spectrometry showed that A2E-fed cells contained A2E and oxidized A2E (furan-A2E). A2E accumulation led to a modest increase (up to 0.25 unit) in lysosomal pH in these cells. The specific activity of cathepsin D and lysosomal acid phosphatase was reduced in the A2E-treated cells, but ROS degradation was not impaired. We found that, upon challenge with ROSs, melanin pigment was induced in the lysosomal fraction of the A2E-treated ARPE-19 cells. Thus, the ARPE-19 cells responded to the A2E treatment and ROS challenge by producing a melanin-containing lysosome fraction. We speculate that this prevents them from becoming impaired in OS processing. CONCLUSIONS We used a modified ARPE-19 cell model in which melanization was elicited as a response to chronic accumulation of A2E. We found that although A2E treatment led, as has been previously reported, to modest lysosomal alkalinization and lysosomal impairment of ARPE-19 cells, a potential homeostatic mechanism may involve production of a special type of lysosomes containing melanin.
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Affiliation(s)
- Eugenia Poliakov
- Laboratory of Retinal Cell and Molecular Biology, NEI, NIH, Bethesda, MD
| | | | - Jian-kang Jiang
- NIH Chemical Genomics Center, National Center for Advancing Translational Sciences, NIH, Rockville, MD
| | - Bianca Martinez
- Laboratory of Retinal Cell and Molecular Biology, NEI, NIH, Bethesda, MD
| | - Toral Parikh
- Laboratory of Retinal Cell and Molecular Biology, NEI, NIH, Bethesda, MD
| | - Aparna Lakkaraju
- Department of Ophthalmology and Visual Sciences, School of Medicine and Public Health, University of Wisconsin-Madison, Madison, WI
| | - Craig Thomas
- NIH Chemical Genomics Center, National Center for Advancing Translational Sciences, NIH, Rockville, MD
| | - Brian P. Brooks
- Ophthalmic Genetics and Visual Function Branch, NEI, NIH, Bethesda, MD
| | - T. Michael Redmond
- Laboratory of Retinal Cell and Molecular Biology, NEI, NIH, Bethesda, MD
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Ablonczy Z, Smith N, Anderson DM, Grey AC, Spraggins J, Koutalos Y, Schey KL, Crouch RK. The utilization of fluorescence to identify the components of lipofuscin by imaging mass spectrometry. Proteomics 2014; 14:936-44. [PMID: 24453194 DOI: 10.1002/pmic.201300406] [Citation(s) in RCA: 18] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/15/2013] [Revised: 12/16/2013] [Accepted: 12/21/2013] [Indexed: 11/08/2022]
Abstract
Lipofuscin, an aging marker in the retinal pigment epithelium (RPE) associated with the development of age-related macular degeneration, is primarily characterized by its fluorescence. The most abundant component of RPE lipofuscin is N-retinylidene-N-retinylethanolamine (A2E) but its exact composition is not known due to the complexity of the RPE extract. In this study, we utilized MALDI imaging to find potential molecules responsible for lipofuscin fluorescence in RPE tissue from Abca4(-/-) , Sv129, and C57Bl6/J mice aged 2 and 6 months. To assert relationships, the individual images in the MALDI imaging datasets were correlated with lipofuscin fluorescence recorded from the same tissues following proper registration. Spatial correlation information, which is usually lost in bioanalytics, pinpointed a relatively small number of potential lipofuscin components. The comparison of four samples in each condition further limited the possibility of false positives and provided various new, age- and strain-specific targets. Validating the usefulness of the fluorescence-enhanced imaging strategy, many known adducts of A2E were identified in the short list of lipofuscin components. These results provided evidence that mass spectrometric imaging can be utilized as a tool to begin to identify the molecular substructure of clinically-relevant diagnostic information.
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Affiliation(s)
- Zsolt Ablonczy
- Department of Ophthalmology, Medical University of South Carolina, Charleston, SC, USA
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109
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Affiliation(s)
- Janet R Sparrow
- Departments of Ophthalmology and Pathology and Cell Biology, Columbia University, New York, New York
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110
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Thao MT, Renfus DJ, Dillon J, Gaillard ER. A2E-mediated photochemical modification to fibronectin and its implications to age-related changes in Bruch's membrane. Photochem Photobiol 2013; 90:329-34. [PMID: 24303925 DOI: 10.1111/php.12200] [Citation(s) in RCA: 9] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2013] [Accepted: 10/23/2013] [Indexed: 11/28/2022]
Abstract
Lipofuscin accumulates normally with age and is more pronounced in retinal dystrophies such as age-related macular degeneration. The major bis-retinoid component of lipofuscin is A2E. In addition to cell damage effects by A2E, we have previously demonstrated that blue-light-mediated A2E leads to modifications in the basement membrane protein laminin. Therefore, the purpose of this study was to advance the understanding of A2E photooxidation effects on fibronectin, the major glycoprotein of Bruch's membrane. In this study, A2E was irradiated with blue light in the presence of a fibronectin peptide consisting of amino acids from the integrin binding region. The modification sites were identified via LC/MS. Our research indicated that blue light irradiation caused cleavage throughout the A2E molecule closest to the pyridinium ring, and attached to the fibronectin peptide preferentially at lysine and arginine residues. All of these reactions are similar to the Maillard reaction. Altogether this study suggests that blue-light-irradiated A2E modifies peptides and forms advance glycation endproducts. Furthermore, these results can be used to identify modifications that occur in Bruch's membrane in vivo.
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Affiliation(s)
- Mai T Thao
- Department of Chemistry and Biochemistry, Northern Illinois University, DeKalb, IL
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111
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Kanagasingam Y, Bhuiyan A, Abràmoff MD, Smith RT, Goldschmidt L, Wong TY. Progress on retinal image analysis for age related macular degeneration. Prog Retin Eye Res 2013; 38:20-42. [PMID: 24211245 DOI: 10.1016/j.preteyeres.2013.10.002] [Citation(s) in RCA: 95] [Impact Index Per Article: 8.6] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2013] [Revised: 10/26/2013] [Accepted: 10/30/2013] [Indexed: 01/12/2023]
Abstract
Age-related macular degeneration (AMD) is the leading cause of vision loss in those over the age of 50 years in the developed countries. The number is expected to increase by ∼1.5 fold over the next ten years due to an increase in aging population. One of the main measures of AMD severity is the analysis of drusen, pigmentary abnormalities, geographic atrophy (GA) and choroidal neovascularization (CNV) from imaging based on color fundus photograph, optical coherence tomography (OCT) and other imaging modalities. Each of these imaging modalities has strengths and weaknesses for extracting individual AMD pathology and different imaging techniques are used in combination for capturing and/or quantification of different pathologies. Current dry AMD treatments cannot cure or reverse vision loss. However, the Age-Related Eye Disease Study (AREDS) showed that specific anti-oxidant vitamin supplementation reduces the risk of progression from intermediate stages (defined as the presence of either many medium-sized drusen or one or more large drusen) to late AMD which allows for preventative strategies in properly identified patients. Thus identification of people with early stage AMD is important to design and implement preventative strategies for late AMD, and determine their cost-effectiveness. A mass screening facility with teleophthalmology or telemedicine in combination with computer-aided analysis for large rural-based communities may identify more individuals suitable for early stage AMD prevention. In this review, we discuss different imaging modalities that are currently being considered or used for screening AMD. In addition, we look into various automated and semi-automated computer-aided grading systems and related retinal image analysis techniques for drusen, geographic atrophy and choroidal neovascularization detection and/or quantification for measurement of AMD severity using these imaging modalities. We also review the existing telemedicine studies which include diagnosis and management of AMD, and how automated disease grading could benefit telemedicine. As there is no treatment for dry AMD and only early intervention can prevent the late AMD, we emphasize mass screening through a telemedicine platform to enable early detection of AMD. We also provide a comparative study between the imaging modalities and identify potential study areas for further improvement and future research direction in automated AMD grading and screening.
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Affiliation(s)
- Yogesan Kanagasingam
- Australian e-Health Research Centre, Commonwealth Scientific and Industrial Research Organization (CSIRO), 65 Brockway Road, Floreat, Underwood Avenue, WA 6014, Australia. http://aehrc.com/
| | - Alauddin Bhuiyan
- Australian e-Health Research Centre, Commonwealth Scientific and Industrial Research Organization (CSIRO), 65 Brockway Road, Floreat, Underwood Avenue, WA 6014, Australia; Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne 3002, Australia
| | - Michael D Abràmoff
- Ophthalmology and Visual Sciences, Electrical and Computer Engineering, Biomedical Engineering, University of Iowa, 200 Hawkins Drive, Iowa City, IA 52242, USA
| | - R Theodore Smith
- Retinal Image Analysis Laboratory, Department of Ophthalmology, NYU School of Medicine, NY, NY 10016, USA
| | - Leonard Goldschmidt
- VA Palo Alto Health Care Systems, 3801 Miranda Avenue, Palo Alto, CA 94304-1290, USA
| | - Tien Y Wong
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, 32 Gisborne Street, East Melbourne 3002, Australia
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Ablonczy Z, Higbee D, Grey AC, Koutalos Y, Schey KL, Crouch RK. Similar molecules spatially correlate with lipofuscin and N-retinylidene-N-retinylethanolamine in the mouse but not in the human retinal pigment epithelium. Arch Biochem Biophys 2013; 539:196-202. [PMID: 23969078 DOI: 10.1016/j.abb.2013.08.005] [Citation(s) in RCA: 26] [Impact Index Per Article: 2.4] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/01/2013] [Revised: 08/08/2013] [Accepted: 08/10/2013] [Indexed: 01/08/2023]
Abstract
The accumulation of lipofuscin in the retinal pigment epithelium (RPE) has been implicated in the development of age-related macular degeneration (AMD) in humans. The exact composition of lipofuscin is not known but its best characterized component is N-retinylidene-N-retinylethanolamine (A2E), a byproduct of the retinoid visual cycle. Utilizing our recently developed matrix-assisted laser desorption/ionization imaging mass spectrometry (MALDI-IMS)-based technique to determine the spatial distribution of A2E, this study compares the relationships of lipofuscin fluorescence and A2E in the murine and human RPE on representative normal tissue. To identify molecules with similar spatial patterns, the images of A2E and lipofuscin were correlated with all the individual images in the MALDI-IMS dataset. In the murine RPE, there was a remarkable correlation between A2E and lipofuscin. In the human RPE, however, minimal correlation was detected. These results were reflected in the marked distinctions between the molecules that spatially correlated with the images of lipofuscin and A2E in the human RPE. While the distribution of murine lipofuscin showed highest similarities with some of the known A2E-adducts, the composition of human lipofuscin was significantly different. These results indicate that A2E metabolism may be altered in the human compared to the murine RPE.
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Affiliation(s)
- Zsolt Ablonczy
- Department of Ophthalmology, Medical University of South Carolina, Charleston, SC 29425, United States.
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113
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Affiliation(s)
- R Theodore Smith
- Department of Ophthalmology, New York University School of Medicine, New York, New York, USA.
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