1
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Huynh KT, Walters S, Foley EK, Hunter JJ. Separate lifetime signatures of macaque S cones, M/L cones, and rods observed with adaptive optics fluorescence lifetime ophthalmoscopy. Sci Rep 2023; 13:2456. [PMID: 36774443 PMCID: PMC9922306 DOI: 10.1038/s41598-023-28877-6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/09/2022] [Accepted: 01/25/2023] [Indexed: 02/13/2023] Open
Abstract
In the retina, several molecules involved in metabolism, the visual cycle, and other roles exhibit intrinsic fluorescence. The overall properties of retinal fluorescence depend on changes to the composition of these molecules and their environmental interactions due to transient functional shifts, especially in disease. This behooves the understanding of the origins and deviations of these properties within the multilayered retina at high lateral and axial resolution. Of particular interest is the fluorescence lifetime, a potential biomarker of function and disease independent of fluorescence intensity that can be measured in the retina with adaptive optics fluorescence lifetime ophthalmoscopy (AOFLIO). This work demonstrates the utility of the phasor method of analysis, an alternate approach to traditional multiexponential fitting, to evaluate photoreceptor two-photon excited AOFLIO data and separate them based on functional differences. Phasor analysis on fluorescence lifetime decay data allowed the repeatable segregation of S from M/L cones, likely from differences in functional or metabolic demands. Furthermore, it is possible to track the lifetime changes in S cones after photodamage. Phasor analysis increases the sensitivity of AOFLIO to functional differences between cells and has the potential to improve our understanding of pathways involved in normal and diseased conditions at the cellular scale throughout the retina.
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Affiliation(s)
- Khang T Huynh
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA.
- Center for Visual Science, University of Rochester, Rochester, NY, 14642, USA.
| | - Sarah Walters
- Currently with IDEX Health & Science, West Henrietta, NY, 14586, USA
- The Institute of Optics, University of Rochester, Rochester, NY, 14627, USA
| | - Emma K Foley
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
| | - Jennifer J Hunter
- Department of Biomedical Engineering, University of Rochester, Rochester, NY, 14627, USA
- Center for Visual Science, University of Rochester, Rochester, NY, 14642, USA
- The Institute of Optics, University of Rochester, Rochester, NY, 14627, USA
- Flaum Eye Institute, University of Rochester, Rochester, NY, 14642, USA
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2
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Kam JH, Shinhmar H, Powner MB, Hayes MJ, Aboelnour A, Jeffery G. Mitochondrial decline in the ageing old world primate retina: Little evidence for difference between the centre and periphery. PLoS One 2023; 18:e0273882. [PMID: 37130143 PMCID: PMC10153720 DOI: 10.1371/journal.pone.0273882] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2022] [Accepted: 04/10/2023] [Indexed: 05/03/2023] Open
Abstract
Mitochondrial decline is a key feature of ageing. The retina has more mitochondria than any other tissue and ages rapidly. To understand human retinal ageing it is critical to examine old world primates that have similar visual systems to humans, and do so across central and peripheral regions, as there is evidence for early central decline. Hence, we examine mitochondrial metrics in young and ageing Macaca fascicularis retinae. In spite of reduced ATP with age, primate mitochondrial complex activity did not decline. But mitochondrial membrane potentials were reduced significantly, and concomitantly, mitochondrial membrane permeability increased. The mitochondrial marker Tom20 declined significantly, consistent with reduced mitochondria number, while VDAC, a voltage dependent anion channel and diffusion pore associated with apoptosis increased significantly. In spite of these clear age-related changes, there was almost no evidence for regional differences between the centre and the periphery in these mitochondrial metrics. Primate cones do not die with age, but many showed marked structural decline with vacuous spaces in proximal inner segments normally occupied by endoplasmic reticulum (ER), that regulate mitochondrial autophagy. In many peripheral cones, ER was displaced by the nucleus that transposed across the outer limiting membrane and could become embedded in mitochondrial populations. These data are consistent with significant changes in retinal mitochondria in old world primate ageing but provide little if any evidence that aged central mitochondria suffer more than those in the periphery.
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Affiliation(s)
- Jaimie Hoh Kam
- Department of Visual Science, Institute of Ophthalmology, University College London, London, United Kingdom
| | - Harpreet Shinhmar
- Department of Visual Science, Institute of Ophthalmology, University College London, London, United Kingdom
| | | | - Matthew John Hayes
- Department of Visual Science, Institute of Ophthalmology, University College London, London, United Kingdom
| | - Asmaa Aboelnour
- Department of Histology, Damanhour University, Damanhour, Egypt
| | - Glen Jeffery
- Department of Visual Science, Institute of Ophthalmology, University College London, London, United Kingdom
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3
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Haverkamp S, Reinhard K, Peichl L, Mietsch M. No evidence for age-related alterations in the marmoset retina. Front Neuroanat 2022; 16:945295. [PMID: 36120100 PMCID: PMC9479465 DOI: 10.3389/fnana.2022.945295] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/16/2022] [Accepted: 07/13/2022] [Indexed: 12/19/2022] Open
Abstract
The physiological aging process of the retina is accompanied by various and sometimes extensive changes: Macular degeneration, retinopathies and glaucoma are the most common findings in the elderly and can potentially lead to irreversible visual disablements up to blindness. To study the aging process and to identify possible therapeutic targets to counteract these diseases, the use of appropriate animal models is mandatory. Besides the most commonly used rodent species, a non-human primate, the common marmoset (Callithrix jacchus) emerged as a promising animal model of human aging over the last years. However, the visual aging process in this species is only partially characterized, especially with regard to retinal aberrations. Therefore, we assessed here for the first time potential changes in retinal morphology of the common marmoset of different age groups. By cell type specific immunolabeling, we analyzed different cell types and distributions, potential photoreceptor and ganglion cell loss, and structural reorganization. We detected no signs of age-related differences in staining patterns or densities of various cell populations. For example, there were no signs of photoreceptor degeneration, and there was only minimal sprouting of rod bipolar cells in aged retinas. Altogether, we describe here the maintenance of a stable neuronal architecture, distribution and number of different cell populations with only mild aberrations during the aging process in the common marmoset retina. These findings are in stark contrast to previously reported findings in rodent species and humans and deserve further investigations to identify the underlying mechanisms and possible therapeutic targets.
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Affiliation(s)
- Silke Haverkamp
- Department of Computational Neuroethology, Max Planck Institute for Neurobiology of Behavior—Caesar, Bonn, Germany
| | - Katja Reinhard
- Retinal Circuits and Optogenetics, Centre for Integrative Neuroscience, University of Tübingen, Tübingen, Germany
| | - Leo Peichl
- Institute of Clinical Neuroanatomy, Dr. Senckenbergische Anatomie, Goethe University Frankfurt, Frankfurt am Main, Germany
| | - Matthias Mietsch
- Laboratory Animal Science Unit, German Primate Center, Göttingen, Germany
- DZHK (German Center for Cardiovascular Research), Partner Site Göttingen, Göttingen, Germany
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4
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Munds RA, Cooper EB, Janiak MC, Lam LG, DeCasien AR, Bauman Surratt S, Montague MJ, Martinez MI, Research Unit CB, Kawamura S, Higham JP, Melin AD. Variation and heritability of retinal cone ratios in a free-ranging population of rhesus macaques. Evolution 2022; 76:1776-1789. [PMID: 35790204 PMCID: PMC9544366 DOI: 10.1111/evo.14552] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/24/2022] [Revised: 05/03/2022] [Accepted: 05/12/2022] [Indexed: 01/22/2023]
Abstract
A defining feature of catarrhine primates is uniform trichromacy-the ability to distinguish red (long; L), green (medium; M), and blue (short; S) wavelengths of light. Although the tuning of photoreceptors is conserved, the ratio of L:M cones in the retina is variable within and between species, with human cone ratios differing from other catarrhines. Yet, the sources and structure of variation in cone ratios are poorly understood, precluding a broader understanding of color vision variability. Here, we report a large-scale study of a pedigreed population of rhesus macaques (Macaca mulatta). We collected foveal RNA and analyzed opsin gene expression using cDNA and estimated additive genetic variance of cone ratios. The average L:M ratio and standard error was 1.03:1 ± 0.02. There was no age effect, and genetic contribution to variation was negligible. We found marginal sex effects with females having larger ratios than males. S cone ratios (0.143:1 ± 0.002) had significant genetic variance with a heritability estimate of 43% but did not differ between sexes or age groups. Our results contextualize the derived human condition of L-cone dominance and provide new information about the heritability of cone ratios and variation in primate color vision.
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Affiliation(s)
- Rachel A. Munds
- Department of Anthropology and ArchaeologyUniversity of CalgaryCalgaryABT2N 1N4Canada
| | - Eve B. Cooper
- Department of AnthropologyNew York UniversityNew YorkNew York10003,New York Consortium in Evolutionary PrimatologyNew YorkNew York10460
| | - Mareike C. Janiak
- Department of Anthropology and ArchaeologyUniversity of CalgaryCalgaryABT2N 1N4Canada,Department of AnthropologyNew York UniversityNew YorkNew York10003,School of Science, Engineering and EnvironmentUniversity of SalfordSalfordM5 4NTUnited Kingdom
| | - Linh Gia Lam
- Department of Anthropology and ArchaeologyUniversity of CalgaryCalgaryABT2N 1N4Canada
| | - Alex R. DeCasien
- Department of AnthropologyNew York UniversityNew YorkNew York10003,New York Consortium in Evolutionary PrimatologyNew YorkNew York10460,Section on Developmental NeurogenomicsNational Institute of Mental HealthBethesdaMaryland20892
| | | | - Michael J. Montague
- Department of NeuroscienceUniversity of PennsylvaniaPhiladelphiaPennsylvania19104
| | - Melween I. Martinez
- Caribbean Primate Research CenterUniversity of Puerto RicoSan JuanPuerto Rico00936
| | | | - Shoji Kawamura
- Department of Integrated BiosciencesUniversity of TokyoKashiwa277‐8562Japan
| | - James P. Higham
- Department of AnthropologyNew York UniversityNew YorkNew York10003,New York Consortium in Evolutionary PrimatologyNew YorkNew York10460
| | - Amanda D. Melin
- Department of Anthropology and ArchaeologyUniversity of CalgaryCalgaryABT2N 1N4Canada,Department of Medical GeneticsUniversity of CalgaryCalgaryABT2N 1N4Canada,Alberta Children's Hospital Research InstituteUniversity of CalgaryCalgaryABT2N 1N4Canada
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5
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Bringmann A, Barth T, Wiedemann R, Wiedemann P. Age- and sex-related variations of individual retinal layer thickness in the foveal center of healthy eyes. Exp Eye Res 2022; 219:109038. [DOI: 10.1016/j.exer.2022.109038] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2022] [Accepted: 03/12/2022] [Indexed: 11/26/2022]
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6
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Differences in chromatic noise suppression of luminance contrast discrimination in young and elderly people. Vis Neurosci 2022; 39:E006. [DOI: 10.1017/s0952523822000050] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/07/2022]
Abstract
Abstract
Aging causes impairment of contrast sensitivity and chromatic discrimination, leading to changes in the perceptual interactions between color and luminance information. We aimed to investigate the influence of chromatic noise on luminance contrast thresholds in young and older adults. Forty participants were divided equally into Young (29.6 ± 6.3-year-old) and Elderly Groups (57.8 ± 6.6-year-old). They performed a luminance contrast discrimination task in the presence of chromatic noise maskers using a mosaic stimulus in a mosaic background. Four chromatic noise masking protocols were applied (protan, deutan, tritan, and no-noise protocols). We found that luminance contrast thresholds were significantly elevated by the addition of chromatic noise in both age groups (P < 0.05). In the Elderly group, but not the younger group, thresholds obtained in the tritan protocol were lower than those obtained from protan and deutan protocols (P < 0.05). For all protocols, the luminance contrast thresholds of elderly participants were higher than in young people (P < 0.01). Tritan chromatic noise was less effective in inhibiting luminance discrimination in elderly participants.
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7
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Shinhmar H, Hogg C, Neveu M, Jeffery G. Weeklong improved colour contrasts sensitivity after single 670 nm exposures associated with enhanced mitochondrial function. Sci Rep 2021; 11:22872. [PMID: 34819619 PMCID: PMC8613193 DOI: 10.1038/s41598-021-02311-1] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/20/2021] [Accepted: 11/09/2021] [Indexed: 11/29/2022] Open
Abstract
Mitochondrial decline in ageing robs cells of ATP. However, animal studies show that long wavelength exposure (650–900 nm) over weeks partially restores ATP and improves function. The likely mechanism is via long wavelengths reducing nanoscopic interfacial water viscosity around ATP rota pumps, improving their efficiency. Recently, repeated 670 nm exposures have been used on the aged human retina, which has high-energy demands and significant mitochondrial and functional decline, to improve vision. We show here that single 3 min 670 nm exposures, at much lower energies than previously used, are sufficient to significantly improve for 1 week cone mediated colour contrast thresholds (detection) in ageing populations (37–70 years) to levels associated with younger subjects. But light needs to be delivered at specific times. In environments with artificial lighting humans are rarely dark-adapted, hence cone function becomes critical. This intervention, demonstrated to improve aged mitochondrial function can be applied to enhance colour vision in old age.
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Affiliation(s)
- Harpreet Shinhmar
- Institute of Ophthalmology, University College London, 11-43 Bath Street, London, EC1V9EL, UK
| | - Chris Hogg
- Institute of Ophthalmology, University College London, 11-43 Bath Street, London, EC1V9EL, UK
| | - Magella Neveu
- Institute of Ophthalmology, University College London, 11-43 Bath Street, London, EC1V9EL, UK
| | - Glen Jeffery
- Institute of Ophthalmology, University College London, 11-43 Bath Street, London, EC1V9EL, UK.
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8
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Pathogenic mechanisms contributing to the vulnerability of aging human photoreceptor cells. Eye (Lond) 2021; 35:2917-2929. [PMID: 34079093 DOI: 10.1038/s41433-021-01602-1] [Citation(s) in RCA: 8] [Impact Index Per Article: 2.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2020] [Revised: 04/29/2021] [Accepted: 05/10/2021] [Indexed: 01/04/2023] Open
Abstract
In human retina, photoreceptor cell death (PCD) is a slow but conspicuous event, which continues with aging. Rods die earlier than cones, the latter continue to alter in a subtle manner until advanced aging. This review summarizes the existing information on age-related changes in photoreceptor cells, especially cones and analyses the possible associated factors. Oxidative and nitrosative stress are involved in photoreceptor alterations, which may stem from light and iron toxicity and other sources. Lipid peroxidation in macular photoreceptor outer segments and mitochondrial aberrations are prominent in aging. It is important to understand how those changes ultimately trigger PCD. The redistribution of calbindin D-28K and long/middle-wavelength-sensitive opsin in the parafoveal and perifoveal cones, anomalies in their somata and axons are strong predictors of their increasing vulnerability with aging. Signs of reduced autophagy, with autophagosomes containing organelle remnants are seen in aging photoreceptor cells. Currently, mechanisms that lead to human PCD are unknown; some observations favour apoptosis as a pathway. Since cones appear to change slowly, there is an opportunity to reverse those changes before they die. Therefore, a full understanding of how cones alter and the molecular pathways they utilize for survival must be the future research goal. Recent approaches to prevent PCD in aging and diseases are highlighted.
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9
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Shinhmar H, Grewal M, Sivaprasad S, Hogg C, Chong V, Neveu M, Jeffery G. Optically Improved Mitochondrial Function Redeems Aged Human Visual Decline. J Gerontol A Biol Sci Med Sci 2021; 75:e49-e52. [PMID: 32596723 DOI: 10.1093/gerona/glaa155] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/25/2020] [Indexed: 02/06/2023] Open
Abstract
The age spectrum of human populations is shifting toward the older with larger proportions suffering physical decline. Mitochondria influence the pace of aging as the energy they provide for cellular function in the form of adenosine triphosphate (ATP) declines with age. Mitochondrial density is greatest in photoreceptors, particularly cones that have high energy demands and mediate color vision. Hence, the retina ages faster than other organs, with a 70% ATP reduction over life and a significant decline in photoreceptor function. Mitochondria have specific light absorbance characteristics influencing their performance. Longer wavelengths spanning 650->1,000 nm improve mitochondrial complex activity, membrane potential, and ATP production. Here, we use 670-nm light to improve photoreceptor performance and measure this psychophysically in those aged 28-72 years. Rod and cone performance declined significantly after approximately 40 years of age. 670-nm light had no impact in younger individuals, but in those around 40 years and older, significant improvements were obtained in color contrast sensitivity for the blue visual axis (tritan) known to display mitochondrial vulnerability. The red visual axis (protan) improved but not significantly. Rod thresholds also improved significantly in those >40 years. Using specific wavelengths to enhance mitochondrial performance will be significant in moderating the aging process in this metabolically demanding tissue.
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Affiliation(s)
| | - Manjot Grewal
- Institute of Ophthalmology, University College London, UK
| | | | - Chris Hogg
- Institute of Ophthalmology, University College London, UK
| | | | - Magella Neveu
- Institute of Ophthalmology, University College London, UK
| | - Glen Jeffery
- Institute of Ophthalmology, University College London, UK
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10
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Kam JH, Weinrich TW, Shinhmar H, Powner MB, Roberts NW, Aboelnour A, Jeffery G. Fundamental differences in patterns of retinal ageing between primates and mice. Sci Rep 2019; 9:12574. [PMID: 31467395 PMCID: PMC6715671 DOI: 10.1038/s41598-019-49121-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2019] [Accepted: 08/06/2019] [Indexed: 01/09/2023] Open
Abstract
Photoreceptors have high metabolic demands and age rapidly, undermining visual function. We base our understanding mainly on ageing mice where elevated inflammation, extracellular deposition, including that of amyloid beta, and rod and cone photoreceptor loss occur, but cones are not lost in ageing primate although their function declines, revealing that primate and mouse age differently. We examine ageing primate retinae and show elevated stress but low inflammation. However, aged primates have a >70% reduction in adenosine triphosphate (ATP) and a decrease in cytochrome c oxidase. There is a shift in cone mitochondrial positioning and glycolytic activity increases. Bruch’s membrane thickens but unlike in mice, amyloid beta is absent. Hence, reduced ATP may explain cone functional decline in ageing but their retained presence offers the possibility of functional restoration if they can be fuelled appropriately to restore cellular function. This is important because as humans we largely depend on cone function to see and are rarely fully dark adapted. Presence of limited aged inflammation and amyloid beta deposition question some of the therapeutic approaches taken to resolve problems of retinal ageing in humans and the possible lack of success in clinical trials in macular degeneration that have targeted inflammatory agents.
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Affiliation(s)
- Jaimie Hoh Kam
- University College London, Institute of Ophthalmology, EC1V9EL, London, UK
| | - Tobias W Weinrich
- University College London, Institute of Ophthalmology, EC1V9EL, London, UK
| | - Harpreet Shinhmar
- University College London, Institute of Ophthalmology, EC1V9EL, London, UK
| | - Michael B Powner
- City, University of London, Centre of Applied Vision Research, EC1V0HB, London, UK
| | - Nicholas W Roberts
- School of Biological Sciences, University of Bristol, BS8 1TQ, Bristol, UK
| | - Asmaa Aboelnour
- Histology and Cytology Department, Faculty of Veterinary Medicine, Damanhour University, Damanhour, Egypt
| | - Glen Jeffery
- University College London, Institute of Ophthalmology, EC1V9EL, London, UK.
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11
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Mitochondrial absorption of short wavelength light drives primate blue retinal cones into glycolysis which may increase their pace of aging. Vis Neurosci 2019; 36:E007. [PMID: 31199213 DOI: 10.1017/s0952523819000063] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
Photoreceptors have high energy demands and densely packed mitochondria through which light passes before phototransduction. Old world primates including humans have three cone photoreceptor types mediating color vision with short (S blue), medium (M green), and long (L red) wavelength sensitivities. However, S-cones are enigmatic. They comprise <10% of the total cone population, their responses saturate early, and they are susceptible in aging and disease. Here, we show that primate S-cones actually have few mitochondria and are fueled by glycolysis, not by mitochondrial respiration. Glycolysis has a limited ability to sustain activity, potentially explaining early S-cone saturation. Mitochondria act as optical filters showing reduced light transmission at 400-450 nm where S-cones are most sensitive (420 nm). This absorbance is likely to arise in a mitochondrial porphyrin that absorbs strongly in the Soret band. Hence, reducing mitochondria will improve S-cone sensitivity but result in increased glycolysis as an alternative energy source, potentially increasing diabetic vulnerability due to restricted glucose access. Further, glycolysis carries a price resulting in premature functional decline as seen in aged S-cones. Soret band absorption may also impact on mitochondrial rich M and L cones by reducing sensitivity at the lower end of their spectral sensitivity range resulting in increased differentiation from S-cone responses. These data add to the list of unique characteristic of S-cones and may also explain aspects of their vulnerability.
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12
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Cone photoreceptor classification in the living human eye from photostimulation-induced phase dynamics. Proc Natl Acad Sci U S A 2019; 116:7951-7956. [PMID: 30944223 PMCID: PMC6475411 DOI: 10.1073/pnas.1816360116] [Citation(s) in RCA: 76] [Impact Index Per Article: 15.2] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/13/2022] Open
Abstract
The three spectral types of cone photoreceptors underlie color perception and are largely responsible for inherited and acquired color vision anomalies. In vivo mapping of the trichromatic cone mosaic by imaging provides the most direct and quantitative means to assess the role of photoreceptors in color vision, but remains challenging because cone reflections only weakly differentiate cone types. Here, we show a noninvasive light microscopy modality that reveals the cell’s spectral type, using the optical phase change that arises within the cell when stimulated with light. Our procedure is orders of magnitude faster and more accurate than prior approaches and makes in vivo cone classification promising for a much wider range of color vision applications. Human color vision is achieved by mixing neural signals from cone photoreceptors sensitive to different wavelengths of light. The spatial arrangement and proportion of these spectral types in the retina set fundamental limits on color perception, and abnormal or missing types are responsible for color vision loss. Imaging provides the most direct and quantitative means to study these photoreceptor properties at the cellular scale in the living human retina, but remains challenging. Current methods rely on retinal densitometry to distinguish cone types, a prohibitively slow process. Here, we show that photostimulation-induced optical phase changes occur in cone cells and carry substantial information about spectral type, enabling cones to be differentiated with unprecedented accuracy and efficiency. Moreover, these phase dynamics arise from physiological activity occurring on dramatically different timescales (from milliseconds to seconds) inside the cone outer segment, thus exposing the phototransduction cascade and subsequent downstream effects. We captured these dynamics in cones of subjects with normal color vision and a deuteranope, and at different macular locations by: (i) marrying adaptive optics to phase-sensitive optical coherence tomography to avoid optical blurring of the eye, (ii) acquiring images at high speed that samples phase dynamics at up to 3 KHz, and (iii) localizing phase changes to the cone outer segment, where photoactivation occurs. Our method should have broad appeal for color vision applications in which the underlying neural processing of photoreceptors is sought and for investigations of retinal diseases that affect cone function.
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13
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Malkemper EP, Peichl L. Retinal photoreceptor and ganglion cell types and topographies in the red fox (Vulpes vulpes
) and Arctic fox (Vulpes lagopus
). J Comp Neurol 2018; 526:2078-2098. [DOI: 10.1002/cne.24493] [Citation(s) in RCA: 5] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/18/2018] [Revised: 06/13/2018] [Accepted: 06/14/2018] [Indexed: 11/10/2022]
Affiliation(s)
- Erich Pascal Malkemper
- Department of General Zoology; Faculty of Biology, University of Duisburg-Essen; Essen Germany
- Department of Game Management and Wildlife Biology, Faculty of Forestry and Wood Sciences; Czech University of Life Sciences; Praha 6 Czech Republic
| | - Leo Peichl
- Max Planck Institute for Brain Research; Frankfurt am Main Germany
- Institute of Cellular and Molecular Anatomy, Dr. Senckenbergische Anatomie, Goethe University Frankfurt; Frankfurt am Main Germany
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14
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Aboelnour A, Van der Spuy J, Powner M, Jeffery G. Primate retinal cones express phosphorylated tau associated with neuronal degeneration yet survive in old age. Exp Eye Res 2017; 165:105-108. [PMID: 28974357 PMCID: PMC5725308 DOI: 10.1016/j.exer.2017.09.013] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/21/2017] [Revised: 09/22/2017] [Accepted: 09/28/2017] [Indexed: 01/24/2023]
Abstract
Photoreceptor cells have high energy demands and suffer significantly with age. In aged rodents both rods and cones are lost, but in primates there is no evidence for aged cone loss, although their function declines. Here we ask if aged primate cones suffer from reduced function because of declining metabolic ability. Tau is a microtubule associated protein critical for mitochondrial function in neurons. Its phosphorylation is a feature of neuronal degeneration undermining respiration and mitochondrial dynamics. We show that total tau is widely distributed in the primate outer retina with little age-related change, being present in both rods and cones and their processes. However, all cones specifically accumulate phosphorylated tau, which was not seen in rods. The presence of this protein will likely undermine cone cell function. However, tau phosphorylation inhibits apoptosis. These data may explain why aged primate cones have reduced function but appear to be resistant to cell death. Consequently, therapies designed to remove phosphorylated tau may carry the risk of inducing cone photoreceptor cell death and further undermine ageing visual function.
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Affiliation(s)
- Asmaa Aboelnour
- Histology and Cytology Department, Faculty of Veterinary Medicine, Damanhour University, Egypt
| | | | - Michael Powner
- Department of Optometry and Visual Science, City University London, UK
| | - Glen Jeffery
- Institute of Ophthalmology, University College London, UK.
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