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Fayed AE, Menten MJ, Kreitner L, Paetzold JC, Rueckert D, Bassily SM, Fikry RR, Hagag AM, Sivaprasad S. Retinal vasculature of different diameters and plexuses exhibit distinct vulnerability in varying severity of diabetic retinopathy. Eye (Lond) 2024; 38:1762-1769. [PMID: 38514853 PMCID: PMC11156674 DOI: 10.1038/s41433-024-03021-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2023] [Revised: 02/08/2024] [Accepted: 03/06/2024] [Indexed: 03/23/2024] Open
Abstract
OBJECTIVES To study the changes in vessel densities (VD) stratified by vessel diameter in the retinal superficial and deep vascular complexes (SVC/DVC) using optical coherence tomography angiography (OCTA) images obtained from people with diabetes and age-matched healthy controls. METHODS We quantified the VD based on vessel diameter categorized as <10, 10-20 and >20 μm in the SVC/DVC obtained on 3 × 3 mm2 OCTA scans using a deep learning-based segmentation and vascular graph extraction tool in people with diabetes and age-matched healthy controls. RESULTS OCTA images obtained from 854 eyes of 854 subjects were divided into 5 groups: healthy controls (n = 555); people with diabetes with no diabetic retinopathy (DR, n = 90), mild and moderate non-proliferative DR (NPDR) (n = 96), severe NPDR (n = 42) and proliferative DR (PDR) (n = 71). Both SVC and DVC showed significant decrease in VD with increasing DR severity (p < 0.001). The largest difference was observed in the <10 μm vessels of the SVC between healthy controls and no DR (13.9% lower in no DR, p < 0.001). Progressive decrease in <10 μm vessels of the SVC and DVC was seen with increasing DR severity (p < 0.001). However, 10-20 μm vessels only showed decline in the DVC, but not the SVC (p < 0.001) and there was no change observed in the >20 μm vessels in either plexus. CONCLUSIONS Our findings suggest that OCTA is able to demonstrate a distinct vulnerability of the smallest retinal vessels in both plexuses that worsens with increasing severity of DR.
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Affiliation(s)
- Alaa E Fayed
- Department of Ophthalmology, Kasr Al-Ainy School of Medicine, Cairo University, Giza, Egypt.
- Watany Eye Hospital, Cairo, Egypt.
- Oxford Eye Hospital, Oxford University Hospitals NHS Foundation Trust, Oxford, UK.
| | - Martin J Menten
- Lab for AI in Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
- BioMedIA, Imperial College London, London, UK
| | - Linus Kreitner
- Lab for AI in Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
| | - Johannes C Paetzold
- Lab for AI in Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
- BioMedIA, Imperial College London, London, UK
| | - Daniel Rueckert
- Lab for AI in Medicine, Klinikum rechts der Isar, Technical University of Munich, Munich, Germany
- BioMedIA, Imperial College London, London, UK
| | | | - Ramy R Fikry
- Department of Ophthalmology, Kasr Al-Ainy School of Medicine, Cairo University, Giza, Egypt
- Watany Eye Hospital, Cairo, Egypt
| | - Ahmed M Hagag
- NIHR Moorfields Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust, London, UK
- Boehringer Ingelheim Limited, London, UK
| | - Sobha Sivaprasad
- NIHR Moorfields Biomedical Research Centre, Moorfields Eye Hospital NHS Foundation Trust, London, UK
- University College London, London, UK
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Alarcon-Martinez L, Shiga Y, Villafranca-Baughman D, Cueva Vargas JL, Vidal Paredes IA, Quintero H, Fortune B, Danesh-Meyer H, Di Polo A. Neurovascular dysfunction in glaucoma. Prog Retin Eye Res 2023; 97:101217. [PMID: 37778617 DOI: 10.1016/j.preteyeres.2023.101217] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/24/2023] [Revised: 09/23/2023] [Accepted: 09/25/2023] [Indexed: 10/03/2023]
Abstract
Retinal ganglion cells, the neurons that die in glaucoma, are endowed with a high metabolism requiring optimal provision of oxygen and nutrients to sustain their activity. The timely regulation of blood flow is, therefore, essential to supply firing neurons in active areas with the oxygen and glucose they need for energy. Many glaucoma patients suffer from vascular deficits including reduced blood flow, impaired autoregulation, neurovascular coupling dysfunction, and blood-retina/brain-barrier breakdown. These processes are tightly regulated by a community of cells known as the neurovascular unit comprising neurons, endothelial cells, pericytes, Müller cells, astrocytes, and microglia. In this review, the neurovascular unit takes center stage as we examine the ability of its members to regulate neurovascular interactions and how their function might be altered during glaucomatous stress. Pericytes receive special attention based on recent data demonstrating their key role in the regulation of neurovascular coupling in physiological and pathological conditions. Of particular interest is the discovery and characterization of tunneling nanotubes, thin actin-based conduits that connect distal pericytes, which play essential roles in the complex spatial and temporal distribution of blood within the retinal capillary network. We discuss cellular and molecular mechanisms of neurovascular interactions and their pathophysiological implications, while highlighting opportunities to develop strategies for vascular protection and regeneration to improve functional outcomes in glaucoma.
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Affiliation(s)
- Luis Alarcon-Martinez
- Department of Neuroscience, Université de Montréal, PO Box 6128, Station centre-ville, Montreal, QC, Canada; Neuroscience Division, Centre de recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), 900 Saint Denis Street, Montreal, QC, Canada; Centre for Eye Research Australia, University of Melbourne, Melbourne, Australia
| | - Yukihiro Shiga
- Department of Neuroscience, Université de Montréal, PO Box 6128, Station centre-ville, Montreal, QC, Canada; Neuroscience Division, Centre de recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), 900 Saint Denis Street, Montreal, QC, Canada
| | - Deborah Villafranca-Baughman
- Department of Neuroscience, Université de Montréal, PO Box 6128, Station centre-ville, Montreal, QC, Canada; Neuroscience Division, Centre de recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), 900 Saint Denis Street, Montreal, QC, Canada
| | - Jorge L Cueva Vargas
- Department of Neuroscience, Université de Montréal, PO Box 6128, Station centre-ville, Montreal, QC, Canada; Neuroscience Division, Centre de recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), 900 Saint Denis Street, Montreal, QC, Canada
| | - Isaac A Vidal Paredes
- Department of Neuroscience, Université de Montréal, PO Box 6128, Station centre-ville, Montreal, QC, Canada; Neuroscience Division, Centre de recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), 900 Saint Denis Street, Montreal, QC, Canada
| | - Heberto Quintero
- Department of Neuroscience, Université de Montréal, PO Box 6128, Station centre-ville, Montreal, QC, Canada; Neuroscience Division, Centre de recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), 900 Saint Denis Street, Montreal, QC, Canada
| | - Brad Fortune
- Discoveries in Sight Research Laboratories, Devers Eye Institute and Legacy Research Institute, Legacy Healthy, Portland, OR, USA
| | - Helen Danesh-Meyer
- Department of Ophthalmology, New Zealand National Eye Centre, Faculty of Medical and Health Sciences, University of Auckland, New Zealand
| | - Adriana Di Polo
- Department of Neuroscience, Université de Montréal, PO Box 6128, Station centre-ville, Montreal, QC, Canada; Neuroscience Division, Centre de recherche du Centre Hospitalier de l'Université de Montréal (CRCHUM), 900 Saint Denis Street, Montreal, QC, Canada.
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Ong JX, Bou Ghanem GO, Nesper PL, Moonjely J, Fawzi AA. Optical Coherence Tomography Angiography of Volumetric Arteriovenous Relationships in the Healthy Macula and Their Derangement in Disease. Invest Ophthalmol Vis Sci 2023; 64:6. [PMID: 37133834 PMCID: PMC10166119 DOI: 10.1167/iovs.64.5.6] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/31/2022] [Accepted: 04/09/2023] [Indexed: 05/04/2023] Open
Abstract
Purpose To characterize relative arteriovenous connectivity of the healthy macula imaged by optical coherence tomography angiography (OCTA) using a new volumetric tool. Methods OCTA volumes were obtained for 20 healthy controls (20 eyes). Two graders identified superficial arterioles and venules. We implemented a custom watershed algorithm to identify capillaries most closely connected to arterioles and venules by using the large vessels as seeds to flood the vascular network. We calculated ratios of arteriolar- to venular-connected capillaries (A/V ratios) and adjusted flow indices (AFIs) for superficial capillary plexuses (SCPs), middle capillary plexuses (MCPs), and deep capillary plexuses (DCPs). We also analyzed two eyes with proliferative diabetic retinopathy (PDR) and one eye with macular telangiectasia (MacTel) to evaluate the utility of this method in visualizing pathological vascular connectivity. Results In healthy eyes, the MCP showed a greater proportion of arteriolar-connected vessels than the SCP and DCP (all P < 0.001). In the SCP, the arteriolar-connected AFI exceeded the venular-connected AFI, but this pattern reversed in the MCP and DCP, with higher venular-connected AFI (all P < 0.001). In PDR eyes, preretinal neovascularization originated from venules, whereas intraretinal microvascular abnormalities were heterogeneous, with some originating from venules and others representing dilated MCP capillary loops. In MacTel, diving SCP venules formed the epicenter of the outer retinal anomalous vascular network. Conclusions Healthy eyes showed a higher MCP A/V ratio but relatively slower arteriolar vs. venular flow velocity in the MCP and DCP, which may explain deep retinal vulnerability to ischemia. In eyes with complex vascular pathology, our connectivity findings were consistent with histopathologic studies.
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Affiliation(s)
- Janice X Ong
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
| | - Ghazi O Bou Ghanem
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
| | - Peter L Nesper
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
| | - Jessica Moonjely
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
| | - Amani A Fawzi
- Department of Ophthalmology, Feinberg School of Medicine, Northwestern University, Chicago, Illinois, United States
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Ramtohul P, Iovino C, Au A, Bacci T, Pichi F, Corradetti G, Corvi F, Manoharan N, Marin AI, Tadayoni R, Sadda S, Freund KB, Sarraf D. Clinical and Morphologic Characteristics of Perivenular Fernlike Leakage on Ultrawide-field Fluorescein Angiography. Ophthalmol Retina 2022; 6:1070-1079. [PMID: 35545196 DOI: 10.1016/j.oret.2022.05.001] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/15/2022] [Revised: 05/02/2022] [Accepted: 05/03/2022] [Indexed: 06/15/2023]
Abstract
PURPOSE To analyze the spectrum of the perivenular fernlike leakage on ultrawide-field fluorescein angiography (UWFA) and discuss its potential implications in the current understanding of the retinal venous outflow. DESIGN Retrospective, observational case series. PARTICIPANTS Eyes presenting with fernlike patterns of dye leakage on UWFA were included in this study. METHODS Analysis of the clinical characteristics and multimodal imaging findings using UWFA and wide-angle swept-source OCT-angiography (SS-OCTA). MAIN OUTCOME MEASURES The disease spectrum, anatomic origin, and clinical implications of this fernlike leakage. RESULTS Multimodal retinal images from 40 eyes of 29 patients with fernlike leakage on UWFA were studied. The underlying etiologies included a wide range of inflammatory disorders, including pars planitis (18 eyes) and central retinal vein occlusion (2 eyes). On UWFA, the fernlike leakage originated from the retinal capillaries and venules directly adjacent to the veins and spared the periarterial zone. This perivenular fernlike leakage involved the far periphery in all cases and progressed more diffusely and centripetally in cases with more severe intraocular inflammation. On wide-angle SS-OCTA, the impairment of deep capillary plexus (DCP) flow signals precisely colocalized with the perivenular fernlike leakages identified on UWFA. CONCLUSIONS The fernlike leakage on UWFA refers to the distinctive perivenular dye leakage that originates from the retinal capillaries and venules. Multimodal imaging correlation suggests that the predominant impairment is at the level of the DCP. The axial symmetry of the fernlike leakage with the veins and sparing of the periarterial zone may support the dominant venous role of the DCP.
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Affiliation(s)
- Prithvi Ramtohul
- Centre Hospitalier Universitaire de l'Hôpital Nord, chemin des Bourrely, Marseille, France; Vitreous Retina Macula Consultants of New York, New York, New York
| | - Claudio Iovino
- Eye Clinic, Multidisciplinary Department of Medical, Surgical and Dental Sciences, University of Campania Luigi Vanvitelli, Naples, Italy
| | - Adrian Au
- Stein Eye Institute, University of California Los Angeles, Los Angeles, California
| | - Tommaso Bacci
- Vitreous Retina Macula Consultants of New York, New York, New York; Ophthalmology Unit, Department of Medicine, Surgery and Neuroscience, University of Siena, Siena University Hospital, Siena, Italy
| | - Francesco Pichi
- Eye Institute, Cleveland Clinic Abu Dhabi, Abu Dhabi, United Arab Emirates; Cleveland Clinic Lerner College of Medicine, Case Western Reserve University, Cleveland, Ohio
| | - Giulia Corradetti
- Department of Ophthalmology, Doheny Image Reading Center, Doheny Eye Institute, University of California Los Angeles (UCLA) Affiliated, Los Angeles, California
| | - Federico Corvi
- Department of Ophthalmology, Doheny Image Reading Center, Doheny Eye Institute, University of California Los Angeles (UCLA) Affiliated, Los Angeles, California
| | - Niranjan Manoharan
- Department of Ophthalmology, University of Colorado School of Medicine, Aurora, Colorado
| | - Alejandro Itzam Marin
- Department of Ophthalmology, University of Colorado School of Medicine, Aurora, Colorado
| | - Ramin Tadayoni
- Université de Paris, Ophthalmology Department, AP-HP, Hôpital Lariboisière, Paris, France; Hôpital Fondation Adolphe de Rothschild, 75019, Paris, France
| | - SriniVas Sadda
- Department of Ophthalmology, Doheny Image Reading Center, Doheny Eye Institute, University of California Los Angeles (UCLA) Affiliated, Los Angeles, California
| | - K Bailey Freund
- Vitreous Retina Macula Consultants of New York, New York, New York; Department of Ophthalmology, NYU Grossman School of New York, New York, New York
| | - David Sarraf
- Stein Eye Institute, University of California Los Angeles, Los Angeles, California.
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5
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Balaratnasingam C, An D, Hein M, Yu P, Yu DY. Studies of the retinal microcirculation using human donor eyes and high-resolution clinical imaging: Insights gained to guide future research in diabetic retinopathy. Prog Retin Eye Res 2022; 94:101134. [PMID: 37154065 DOI: 10.1016/j.preteyeres.2022.101134] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/23/2022] [Revised: 09/18/2022] [Accepted: 10/03/2022] [Indexed: 11/06/2022]
Abstract
The microcirculation plays a key role in delivering oxygen to and removing metabolic wastes from energy-intensive retinal neurons. Microvascular changes are a hallmark feature of diabetic retinopathy (DR), a major cause of irreversible vision loss globally. Early investigators have performed landmark studies characterising the pathologic manifestations of DR. Previous works have collectively informed us of the clinical stages of DR and the retinal manifestations associated with devastating vision loss. Since these reports, major advancements in histologic techniques coupled with three-dimensional image processing has facilitated a deeper understanding of the structural characteristics in the healthy and diseased retinal circulation. Furthermore, breakthroughs in high-resolution retinal imaging have facilitated clinical translation of histologic knowledge to detect and monitor progression of microcirculatory disturbances with greater precision. Isolated perfusion techniques have been applied to human donor eyes to further our understanding of the cytoarchitectural characteristics of the normal human retinal circulation as well as provide novel insights into the pathophysiology of DR. Histology has been used to validate emerging in vivo retinal imaging techniques such as optical coherence tomography angiography. This report provides an overview of our research on the human retinal microcirculation in the context of the current ophthalmic literature. We commence by proposing a standardised histologic lexicon for characterising the human retinal microcirculation and subsequently discuss the pathophysiologic mechanisms underlying key manifestations of DR, with a focus on microaneurysms and retinal ischaemia. The advantages and limitations of current retinal imaging modalities as determined using histologic validation are also presented. We conclude with an overview of the implications of our research and provide a perspective on future directions in DR research.
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Affiliation(s)
- Chandrakumar Balaratnasingam
- Lions Eye Institute, Nedlands, Western Australia, Australia; Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia; Department of Ophthalmology, Sir Charles Gairdner Hospital, Western Australia, Australia.
| | - Dong An
- Lions Eye Institute, Nedlands, Western Australia, Australia; Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
| | - Martin Hein
- Lions Eye Institute, Nedlands, Western Australia, Australia; Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
| | - Paula Yu
- Lions Eye Institute, Nedlands, Western Australia, Australia; Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
| | - Dao-Yi Yu
- Lions Eye Institute, Nedlands, Western Australia, Australia; Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
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Flow goes forward and cells step backward: endothelial migration. Exp Mol Med 2022; 54:711-719. [PMID: 35701563 PMCID: PMC9256678 DOI: 10.1038/s12276-022-00785-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/17/2022] [Revised: 03/28/2022] [Accepted: 04/04/2022] [Indexed: 12/28/2022] Open
Abstract
Systemic and pulmonary circulations constitute a complex organ that serves multiple important biological functions. Consequently, any pathological processing affecting the vasculature can have profound systemic ramifications. Endothelial and smooth muscle are the two principal cell types composing blood vessels. Critically, endothelial proliferation and migration are central to the formation and expansion of the vasculature both during embryonic development and in adult tissues. Endothelial populations are quite heterogeneous and are both vasculature type- and organ-specific. There are profound molecular, functional, and phenotypic differences between arterial, venular and capillary endothelial cells and endothelial cells in different organs. Given this endothelial cell population diversity, it has been challenging to determine the origin of endothelial cells responsible for the angiogenic expansion of the vasculature. Recent technical advances, such as precise cell fate mapping, time-lapse imaging, genome editing, and single-cell RNA sequencing, have shed new light on the role of venous endothelial cells in angiogenesis under both normal and pathological conditions. Emerging data indicate that venous endothelial cells are unique in their ability to serve as the primary source of endothelial cellular mass during both developmental and pathological angiogenesis. Here, we review recent studies that have improved our understanding of angiogenesis and suggest an updated model of this process. Cells that line the inside of veins possess a unique ability to grow new blood vessels and a better understanding of these cells could lead to new treatments for cancer, autoimmunity and other diseases associated with abnormal blood vessel formation. Michael Simons and colleagues from Yale University School of Medicine in New Haven, USA, review the attributes of venous endothelial cells, such as their unique ability to proliferate and migrate against blood flow, and then to form new intricate networks of minute blood vessels, in response to appropriate signals. The authors discuss emerging evidence implicating these cells in a variety of diseases, and suggest that drugs aimed at modulating the molecular function or migratory activities of venous endothelial cells could be used to correct abnormal blood vessel expansion.
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Cabral D, Fradinho AC, Pereira T, Ramakrishnan MS, Bacci T, An D, Tenreiro S, Seabra MC, Balaratnasingam C, Freund KB. Macular Vascular Imaging and Connectivity Analysis Using High-Resolution Optical Coherence Tomography. Transl Vis Sci Technol 2022; 11:2. [PMID: 35648637 PMCID: PMC9172017 DOI: 10.1167/tvst.11.6.2] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/02/2022] [Accepted: 05/06/2022] [Indexed: 11/24/2022] Open
Abstract
Purpose To characterize macular blood flow connectivity in vivo using high-resolution optical coherence tomography (HighRes OCT). Methods Cross-sectional, observational study. Dense (6-µm interscan distance) perifoveal HighRes OCT raster scans were performed on healthy participants. To mitigate the limitations of projection-resolved OCT-angiography, flow and structural data were used to observe the vascular structures of the superficial vascular complex (SVC) and the deep vascular complex. Vascular segmentation and rendering were performed using Imaris 9.5 software. Inflow and outflow patterns were classified according to vascular diameter and branching order from superficial arteries and veins, respectively. Results Eight eyes from eight participants were included in this analysis, from which 422 inflow and 459 outflow connections were characterized. Arteries had direct arteriolar connections to the SVC (78%) and to the intermediate capillary plexus (ICP, 22%). Deep capillary plexus (DCP) inflow derived from small-diameter vessels succeeding ICP arterioles. The most prevalent outflow pathways coursed through superficial draining venules (74%). DCP draining venules ordinarily merged with ICP draining venules and drained independently of superficial venules in 21% of cases. The morphology of DCP draining venules in structural HighRes OCT is distinct from other vessels crossing the inner nuclear layer and can be used to identify superficial veins. Conclusions Vascular connectivity analysis supports a hybrid circuitry of blood flow within the human parafoveal macula. Translational Relevance Characterization of parafoveal macular blood flow connectivity in vivo using a precise segmentation of HighRes OCT is consistent with ground-truth microscopy studies and shows a hybrid circuitry.
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Affiliation(s)
- Diogo Cabral
- Vitreous Retina Macula Consultants of New York, NY, USA
- CEDOC, NOVA Medical School I Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisbon, Portugal
| | - Ana C. Fradinho
- CEDOC, NOVA Medical School I Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisbon, Portugal
| | - Telmo Pereira
- CEDOC, NOVA Medical School I Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisbon, Portugal
| | | | - Tommaso Bacci
- Vitreous Retina Macula Consultants of New York, NY, USA
| | - Dong An
- Centre for Ophthalmology and Visual Science, University of Western Australia, Nedlands, Western Australia, Australia
- Lions Eye Institute, Nedlands, Western Australia, Australia
| | - Sandra Tenreiro
- CEDOC, NOVA Medical School I Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisbon, Portugal
| | - Miguel C. Seabra
- CEDOC, NOVA Medical School I Faculdade de Ciências Médicas, Universidade NOVA de Lisboa, Lisbon, Portugal
- UCL Institute of Ophthalmology, London, UK
| | - Chandrakumar Balaratnasingam
- Centre for Ophthalmology and Visual Science, University of Western Australia, Nedlands, Western Australia, Australia
- Lions Eye Institute, Nedlands, Western Australia, Australia
| | - K. Bailey Freund
- Vitreous Retina Macula Consultants of New York, NY, USA
- Department of Ophthalmology, NYU Grossman School of Medicine, New York, NY, USA
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Zouache MA. Variability in Retinal Neuron Populations and Associated Variations in Mass Transport Systems of the Retina in Health and Aging. Front Aging Neurosci 2022; 14:778404. [PMID: 35283756 PMCID: PMC8914054 DOI: 10.3389/fnagi.2022.778404] [Citation(s) in RCA: 7] [Impact Index Per Article: 3.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/16/2021] [Accepted: 01/13/2022] [Indexed: 11/17/2022] Open
Abstract
Aging is associated with a broad range of visual impairments that can have dramatic consequences on the quality of life of those impacted. These changes are driven by a complex series of alterations affecting interactions between multiple cellular and extracellular elements. The resilience of many of these interactions may be key to minimal loss of visual function in aging; yet many of them remain poorly understood. In this review, we focus on the relation between retinal neurons and their respective mass transport systems. These metabolite delivery systems include the retinal vasculature, which lies within the inner portion of the retina, and the choroidal vasculature located externally to the retinal tissue. A framework for investigation is proposed and applied to identify the structures and processes determining retinal mass transport at the cellular and tissue levels. Spatial variability in the structure of the retina and changes observed in aging are then harnessed to explore the relation between variations in neuron populations and those seen among retinal metabolite delivery systems. Existing data demonstrate that the relation between inner retinal neurons and their mass transport systems is different in nature from that observed between the outer retina and choroid. The most prominent structural changes observed across the eye and in aging are seen in Bruch’s membrane, which forms a selective barrier to mass transfers at the interface between the choroidal vasculature and the outer retina.
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Aschauer J, Aschauer S, Pollreisz A, Datlinger F, Gatterer C, Mylonas G, Egner B, Hofer D, Steiner I, Hengstenberg C, Schmidt-Erfurth U. Identification of Subclinical Microvascular Biomarkers in Coronary Heart Disease in Retinal Imaging. Transl Vis Sci Technol 2021; 10:24. [PMID: 34787666 PMCID: PMC8606892 DOI: 10.1167/tvst.10.13.24] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/29/2022] Open
Abstract
Purpose Cardiovascular disease and foremost coronary heart disease (CHD) are the worldwide leading causes of death. The aim of this study was to use non-invasive, multimodel retinal imaging to define microvascular features in patients with and without coronary angiography (CA)-confirmed CHD. Methods In this prospective, cross-sectional pilot study we included adult patients who presented to a tertiary referral center for elective CA due to suspected CHD. All patients underwent widefield fundus photography for retinopathy grading. Optical coherence tomography angiography was used to measure vessel density (VD) of the individual capillary plexuses in 6 × 6-mm macular volume scans. Adaptive optics imaging was performed to assess the first-order arteriolar lumen diameter (LD), total diameter (TD), wall-to-lumen ratio (WLR), and wall cross-section area, as well as to qualitatively describe vessel morphology. Results Of the included 45 patients (13 females; 65 ± 10 years old), 27 were confirmed with CHD in elective CA. The most prevalent retinal vascular pathologies were arteriovenous nickings, focal arterial narrowings, and microaneurysms. VD in the superficial capillary plexus, deep capillary plexus, and choriocapillaris was lower in CHD patients, although the odds ratios were not significantly different from 1 (P = 0.06–0.92). Median arterial LD, TD, and WLR values were 98.3 µm (interquartile range [IQR] = 13.0), 122.9 µm (IQR = 17.6), and 0.26 µm (IQR = 0.07), respectively, with a trend toward a higher WLR in CHD patients. Conclusions In a cardiovascular risk population, high-resolution quantitative and qualitative microvascular phenotyping in the retina may provide valuable subclinical indicators for coronary artery impairment, although larger clinical trials are needed. Translational Relevance Subclinical retinal microvascular changes may serve as non-invasive, cost-effective biomarkers for risk stratification of patients with CHD.
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Affiliation(s)
- Julia Aschauer
- Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria.,Vienna Clinical Trial Center, Medical University of Vienna, Vienna, Austria
| | - Stefan Aschauer
- Division of Cardiology, Department of Internal Medicine II, Medical University of Vienna, Vienna, Austria
| | - Andreas Pollreisz
- Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria.,Vienna Clinical Trial Center, Medical University of Vienna, Vienna, Austria
| | - Felix Datlinger
- Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria.,Vienna Clinical Trial Center, Medical University of Vienna, Vienna, Austria
| | - Constantin Gatterer
- Division of Cardiology, Department of Internal Medicine II, Medical University of Vienna, Vienna, Austria
| | - Georgios Mylonas
- Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria
| | - Berit Egner
- Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria
| | - Dominik Hofer
- Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria
| | - Irene Steiner
- CeMSIIS, Institute for Medical Statistics, Medical University of Vienna, Vienna, Austria
| | - Christian Hengstenberg
- Division of Cardiology, Department of Internal Medicine II, Medical University of Vienna, Vienna, Austria
| | - Ursula Schmidt-Erfurth
- Department of Ophthalmology and Optometry, Medical University of Vienna, Vienna, Austria
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10
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Bennett HC, Kim Y. Pericytes Across the Lifetime in the Central Nervous System. Front Cell Neurosci 2021; 15:627291. [PMID: 33776651 PMCID: PMC7994897 DOI: 10.3389/fncel.2021.627291] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/09/2020] [Accepted: 02/23/2021] [Indexed: 12/25/2022] Open
Abstract
The pericyte is a perivascular cell type that encapsulates the microvasculature of the brain and spinal cord. Pericytes play a crucial role in the development and maintenance of the blood-brain barrier (BBB) and have a multitude of important functions in the brain. Recent evidence indicates that pericyte impairment has been implicated in neurovascular pathology associated with various human diseases such as diabetes mellitus, Alzheimer's disease (AD), and stroke. Although the pericyte is essential for normal brain function, knowledge about its developmental trajectory and anatomical distribution is limited. This review article summarizes the scientific community's current understanding of pericytes' regional heterogeneity in the brain and their changes during major life stages. More specifically, this review article focuses on pericyte differentiation and migration during brain development, regional population differences in the adult brain, and changes during normal and pathological aging. Most of what is known about pericytes come from studies of the cerebral cortex and hippocampus. Therefore, we highlight the need to expand our understanding of pericyte distribution and function in the whole brain to better delineate this cell type's role in the normal brain and pathological conditions.
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Affiliation(s)
- Hannah C Bennett
- Department of Neural and Behavioral Sciences, Penn State University, Hershey, PA, United States
| | - Yongsoo Kim
- Department of Neural and Behavioral Sciences, Penn State University, Hershey, PA, United States
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11
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Alarcon-Martinez L, Yemisci M, Dalkara T. Pericyte morphology and function. Histol Histopathol 2021; 36:633-643. [PMID: 33595091 DOI: 10.14670/hh-18-314] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/12/2022]
Abstract
The proper delivery of blood is essential for healthy neuronal function. The anatomical substrate for this precise mechanism is the neurovascular unit, which is formed by neurons, glial cells, endothelia, smooth muscle cells, and pericytes. Based on their particular location on the vessel wall, morphology, and protein expression, pericytes have been proposed as cells capable of regulating capillary blood flow. Pericytes are located around the microvessels, wrapping them with their processes. Their morphology and protein expression substantially vary along the vascular tree. Their contractibility is mediated by a unique cytoskeleton organization formed by filaments of actin that allows pericyte deformability with the consequent mechanical force transferred to the extracellular matrix for changing the diameter. Pericyte ultrastructure is characterized by large mitochondria likely to provide energy to regulate intracellular calcium concentration and fuel contraction. Accordingly, pericytes with compromised energy show a sustained intracellular calcium increase that leads to persistent microvascular constriction. Pericyte morphology is highly plastic and adapted for varying contractile capability along the microvascular tree, making pericytes ideal cells to regulate the capillary blood flow in response to local neuronal activity. Besides the vascular regulation, pericytes also play a role in the maintenance of the blood-brain/retina barrier, neovascularization and angiogenesis, and leukocyte transmigration. Here, we review the morphological and functional features of the pericytes as well as potential specific markers for the study of pericytes in the brain and retina.
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Affiliation(s)
- Luis Alarcon-Martinez
- Department of Neuroscience and Centre de Recherche du Centre Hospitalier de l'Université de Montréal, Université de Montréal, Montréal, QC, Canada.
| | - Muge Yemisci
- Department of Neurology, Faculty of Medicine, Hacettepe University, Ankara, Turkey.,Institute of Neurological Sciences and Psychiatry, Hacettepe University, Ankara, Turkey
| | - Turgay Dalkara
- Institute of Neurological Sciences and Psychiatry, Hacettepe University, Ankara, Turkey
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12
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An D, Yu P, Freund KB, Yu DY, Balaratnasingam C. Three-Dimensional Characterization of the Normal Human Parafoveal Microvasculature Using Structural Criteria and High-Resolution Confocal Microscopy. Invest Ophthalmol Vis Sci 2021; 61:3. [PMID: 32749461 PMCID: PMC7443114 DOI: 10.1167/iovs.61.10.3] [Citation(s) in RCA: 36] [Impact Index Per Article: 12.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/27/2022] Open
Abstract
Purpose To use structural criteria to reconcile the three-dimensional organization and connectivity of the parafoveal microvasculature. Methods The parafoveal microvasculature was perfused and labeled in 16 normal human donor eyes for lectin, alpha smooth muscle actin, and filamentous actin. Established structural criteria gathered using confocal microscopy, including vessel diameter, endothelial cell morphology, and presence/density of smooth muscle cells, were used to differentiate arteries, arterioles, capillaries, venules, and veins. Three-dimensional visualization strategies were used to define the connections between retinal arteries and veins within the superficial vascular plexus (SVP), intermediate capillary plexus (ICP), and deep capillary plexus (DCP). Results The parafoveal microvasculature has two different inflow patterns and seven different outflow patterns. The SVP and ICP were connected to retinal arteries by arterioles. Inflow into the DCP occurred only via small arterioles (a1; mean diameter, 8.3 µm) that originated from the ICP. Direct connections between the DCP and retinal arteries were not identified. Each capillary plexus formed its own venule that drained independently or in conjunction with venules from other plexuses into a retinal vein at the level of the ganglion cell layer. For the DCP, a1 was significantly smaller than its draining venule (mean diameter, 18.8 µm; P < 0.001). Conclusions The SVP and ICP of the parafoveal microvasculature have both in series and in parallel arterial and venous connections. Arterial supply to the DCP originates from the ICP, but with direct drainage to the retinal vein. These findings may help to develop an understanding of the pattern of retinal lesions characterizing a myriad of retinal vascular diseases.
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13
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Chandrasekera E, An D, McAllister IL, Yu DY, Balaratnasingam C. Three-Dimensional Microscopy Demonstrates Series and Parallel Organization of Human Peripapillary Capillary Plexuses. Invest Ophthalmol Vis Sci 2019; 59:4327-4344. [PMID: 30193305 DOI: 10.1167/iovs.18-24105] [Citation(s) in RCA: 20] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose To define the three-dimensional topologic organization of the human peripapillary capillary plexuses in order to better understand the hemodynamic characteristics of this retinal circulation. Methods The retinal microvasculature was perfusion labeled in five normal human donor eyes, and optical stacks were collected from regions immediately superior, temporal, inferior, and nasal to the optic disk by using confocal scanning laser microscopy. The spatial location and morphometric characteristics of capillary plexuses were compared. Three-dimensional visualization strategies were used to document the organization of vascular conduits that interconnect capillary beds and to study the communications between capillary beds and precapillary arterioles and postcapillary venules. Results The peripapillary microcirculation is composed of four capillary plexuses, including the radial peripapillary capillary plexus at the level of the nerve fiber layer, the superficial capillary plexus (SCP) at the level of the ganglion cell layer, the intermediate capillary plexus located at the inner boundary of the inner nuclear layer, and the deep capillary plexus located at the outer boundary of the inner nuclear layer. Capillary diameter and density were significantly different between the four plexuses (both P ≤ 0.011). The SCP is the only capillary bed that receives feeding and draining branches directly from precapillary arterioles and postcapillary venules, respectively. Four different inflow and outflow patterns characterized the communication between the SCP and surrounding capillary beds. Conclusions The capillary plexuses of the human peripapillary microcirculation are arranged in series and parallel and manifest specializations that likely reflect the unique metabolic demands and biochemical environment of the retinal layers.
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Affiliation(s)
- Erandi Chandrasekera
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
| | - Dong An
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia
| | - Ian L McAllister
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia.,Lions Eye Institute, Nedlands, Western Australia, Australia.,Department of Ophthalmology, Royal Perth Hospital, Perth, Western Australia, Australia
| | - Dao-Yi Yu
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia.,Lions Eye Institute, Nedlands, Western Australia, Australia
| | - Chandrakumar Balaratnasingam
- Centre for Ophthalmology and Visual Science, University of Western Australia, Perth, Australia.,Lions Eye Institute, Nedlands, Western Australia, Australia.,Department of Ophthalmology, Sir Charles Gairdner Hospital, Nedlands, Western Australia, Australia
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14
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Nguyen CTO, Hui F, Charng J, Velaedan S, van Koeverden AK, Lim JKH, He Z, Wong VHY, Vingrys AJ, Bui BV, Ivarsson M. Retinal biomarkers provide "insight" into cortical pharmacology and disease. Pharmacol Ther 2017; 175:151-177. [PMID: 28174096 DOI: 10.1016/j.pharmthera.2017.02.009] [Citation(s) in RCA: 29] [Impact Index Per Article: 4.1] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/18/2023]
Abstract
The retina is an easily accessible out-pouching of the central nervous system (CNS) and thus lends itself to being a biomarker of the brain. More specifically, the presence of neuronal, vascular and blood-neural barrier parallels in the eye and brain coupled with fast and inexpensive methods to quantify retinal changes make ocular biomarkers an attractive option. This includes its utility as a biomarker for a number of cerebrovascular diseases as well as a drug pharmacology and safety biomarker for the CNS. It is a rapidly emerging field, with some areas well established, such as stroke risk and multiple sclerosis, whereas others are still in development (Alzheimer's, Parkinson's, psychological disease and cortical diabetic dysfunction). The current applications and future potential of retinal biomarkers, including potential ways to improve their sensitivity and specificity are discussed. This review summarises the existing literature and provides a perspective on the strength of current retinal biomarkers and their future potential.
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Affiliation(s)
- Christine T O Nguyen
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia.
| | - Flora Hui
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Jason Charng
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Shajan Velaedan
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Anna K van Koeverden
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Jeremiah K H Lim
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Zheng He
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Vickie H Y Wong
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Algis J Vingrys
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Bang V Bui
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
| | - Magnus Ivarsson
- Department of Optometry and Vision Sciences, University of Melbourne, Parkville, 3010, Victoria, Australia
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15
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Ultrastructure of the human retina in aging and various pathological states. Micron 2012; 43:759-81. [DOI: 10.1016/j.micron.2012.01.011] [Citation(s) in RCA: 62] [Impact Index Per Article: 5.2] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/23/2012] [Accepted: 01/24/2012] [Indexed: 11/22/2022]
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16
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Kur J, Newman EA, Chan-Ling T. Cellular and physiological mechanisms underlying blood flow regulation in the retina and choroid in health and disease. Prog Retin Eye Res 2012; 31:377-406. [PMID: 22580107 DOI: 10.1016/j.preteyeres.2012.04.004] [Citation(s) in RCA: 448] [Impact Index Per Article: 37.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/16/2012] [Revised: 04/17/2012] [Accepted: 04/22/2012] [Indexed: 02/06/2023]
Abstract
We review the cellular and physiological mechanisms responsible for the regulation of blood flow in the retina and choroid in health and disease. Due to the intrinsic light sensitivity of the retina and the direct visual accessibility of fundus blood vessels, the eye offers unique opportunities for the non-invasive investigation of mechanisms of blood flow regulation. The ability of the retinal vasculature to regulate its blood flow is contrasted with the far more restricted ability of the choroidal circulation to regulate its blood flow by virtue of the absence of glial cells, the markedly reduced pericyte ensheathment of the choroidal vasculature, and the lack of intermediate filaments in choroidal pericytes. We review the cellular and molecular components of the neurovascular unit in the retina and choroid, techniques for monitoring retinal and choroidal blood flow, responses of the retinal and choroidal circulation to light stimulation, the role of capillaries, astrocytes and pericytes in regulating blood flow, putative signaling mechanisms mediating neurovascular coupling in the retina, and changes that occur in the retinal and choroidal circulation during diabetic retinopathy, age-related macular degeneration, glaucoma, and Alzheimer's disease. We close by discussing issues that remain to be explored.
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Affiliation(s)
- Joanna Kur
- Department of Neuroscience, University of Minnesota, Minneapolis, MN 55455, USA
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17
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Ganesan P, He S, Xu H. Modelling of pulsatile blood flow in arterial trees of retinal vasculature. Med Eng Phys 2011; 33:810-23. [DOI: 10.1016/j.medengphy.2010.10.004] [Citation(s) in RCA: 11] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/11/2010] [Revised: 09/30/2010] [Accepted: 10/05/2010] [Indexed: 11/16/2022]
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18
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Powner MB, Scott A, Zhu M, Munro PMG, Foss AJE, Hageman GS, Gillies MC, Fruttiger M. Basement membrane changes in capillaries of the ageing human retina. Br J Ophthalmol 2011; 95:1316-22. [PMID: 21606466 DOI: 10.1136/bjo.2011.204222] [Citation(s) in RCA: 16] [Impact Index Per Article: 1.2] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/03/2022]
Abstract
OBJECTIVES The ultrastructural appearance of retinal capillaries can yield important information about disease mechanisms, but is not well characterised in human post mortem samples. We therefore aimed to create a baseline for the appearance of capillaries and establish how this is influenced by post mortem fixation delays and donor age. METHODS Electron microscopy was used to characterise retinal capillaries in 20 anonymous donors (with no known eye diseases) of various ages and with various post mortem fixation delays. In addition, samples from six patients with conditions that are known to affect the retinal vasculature (four cases of type 2 diabetes without diabetic retinopathy, one case of diabetic retinopathy and one case of macular telangiectasia type 2) were analysed. RESULTS Vacuoles were found in capillary basement membranes at the vessel-glia interface in all samples, from both the normal and disease cases. Vacuole frequency increased with donor age but was not influenced by post mortem fixation delays. CONCLUSION Vacuoles in the basement membrane are a normal feature of adult human retinal capillaries and do not indicate disease. Their incidence increases with age and might be a contributing factor to late-onset pathologies of the retinal vasculature.
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Affiliation(s)
- Michael B Powner
- MacTel Laboratory Research Group, UCL Institute of Ophthalmology, University College London, London, UK
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19
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Ganesan P, He S, Xu H. Development of an image-based model for capillary vasculature of retina. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2011; 102:35-46. [PMID: 21277036 DOI: 10.1016/j.cmpb.2010.12.009] [Citation(s) in RCA: 14] [Impact Index Per Article: 1.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 11/23/2009] [Revised: 12/10/2010] [Accepted: 12/12/2010] [Indexed: 05/27/2023]
Abstract
The paper presents a method of development of a detailed network model to represent retinal capillary vasculature. The capillary model is a circular mesh consisting of concentric rings with an increasing diameter. Each of the rings has uniformly distributed bifurcation nodes to represent capillary vessels. The model is customized using the data that has been measured from confocal microscopic images of a mouse retina. The capillary model developed can be connected to networks of larger vessels of the vasculature such as arterial and venous networks to form a complete model of the retinal network. A method to automate such interface connections between capillary and other vascular networks using connecting vessels (i.e., pre-capillary and post-capillary) is also presented in the paper. Such a detailed image-based capillary model together with the arterial and venular networks can be used for various circulation simulations to obtain accurate information on hemodynamic quantities such as the spatial distribution of pressure and flow in the vasculature for both physiological and pathological conditions. The method presented for the development of the capillary model can also be adopted for vasculatures of other organs.
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Affiliation(s)
- P Ganesan
- School of Engineering, University of Aberdeen, UK
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20
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21
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22
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Ganesan P, He S, Xu H. Analysis of retinal circulation using an image-based network model of retinal vasculature. Microvasc Res 2010; 80:99-109. [PMID: 20156460 DOI: 10.1016/j.mvr.2010.02.005] [Citation(s) in RCA: 29] [Impact Index Per Article: 2.1] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/15/2009] [Revised: 01/20/2010] [Accepted: 02/04/2010] [Indexed: 11/29/2022]
Abstract
This paper presents the results of a circulation analysis using an image based network model of a murine retinal vasculature, which closely represents the 3D vascular distribution of the retina. The uneven distribution of the red blood cells at vascular network bifurcations (i.e., plasma skimming effect), the microvascular diameter effect (i.e., Fahraeus-Lindqvist effect) and the role of endothelium surface layer (i.e., in vivo viscosity) were considered in determining the viscosity of the blood in the retinal vessel segments. The study yielded detailed distributions of the hemodynamic quantities in the arterial and venous trees shown in various anatomical based contour plots. Quantitative analysis was also carried out based on statistical distributions. The analysis shows that the distribution of the blood hematocrit (H(D)) in the retinal network is very non-uniform, with lower values at the pre-equator region (near the optic disc) and higher values in the equator region of the retina. This has significant influence on the distribution of apparent viscosity, pressure and wall shear stress (WSS) in the vasculature. The viscosity is generally higher in smaller vessels (i.e., pre-capillary vessels) but exceptions occur in some vessels where the H(D) is small. WSS is greater in smaller vessels located near the optic disc than that in the mainstream retinal vessels. The results presented can be directly useful to ophthalmologists and researchers working with retinal vasculature.
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Affiliation(s)
- P Ganesan
- School of Engineering, University of Aberdeen, Aberdeen, UK
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23
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Development of an image-based network model of retinal vasculature. Ann Biomed Eng 2010; 38:1566-85. [PMID: 20135352 DOI: 10.1007/s10439-010-9942-4] [Citation(s) in RCA: 22] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/13/2009] [Accepted: 01/19/2010] [Indexed: 10/19/2022]
Abstract
The paper presents an image-based network model of retinal vasculature taking account of the 3D vascular distribution of the retina. Mouse retinas were prepared using flat-mount technique and vascular images were obtained using confocal microscopy. The vascular morphometric information obtained from confocal images was used for the model development. The network model developed directly represents the vascular geometry of all the large vessels of the arteriolar and venular trees and models the capillaries using uniformly distributed meshes. The vasculatures in different layers of the retina, namely the superficial, intermediate, and deep layer, were modeled separately in the network and were linked through connecting vessels. The branching data of the vasculatures was recorded using the method of connectivity matrix of network (the graph theory). Such an approach is able to take into account the detailed vasculature of individual retinas concerned. Using the network model developed, a circulation analysis based on Poiseuille's equation was carried out. The investigations produced predictions of spatial distribution of the pressure, flow, and wall shear stress in the entire retinal vasculature. The method developed can be used as a tool for continuous monitoring of the retinal circulation for clinical assessments as well as experimental studies.
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24
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Roine S, Harju M, Kivelä TT, Pöyhönen M, Nikoskelainen E, Tuisku S, Kalimo H, Viitanen M, Summanen PA. Ophthalmologic findings in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy: a cross-sectional study. Ophthalmology 2006; 113:1411-7. [PMID: 16877080 DOI: 10.1016/j.ophtha.2006.03.030] [Citation(s) in RCA: 33] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2005] [Revised: 03/19/2006] [Accepted: 03/19/2006] [Indexed: 11/23/2022] Open
Abstract
OBJECTIVE To determine the ophthalmologic findings, especially the nature of retinal vascular changes, and their clinical significance in cerebral autosomal dominant arteriopathy with subcortical infarcts and leukoencephalopathy (CADASIL), a disease that causes migraine, recurrent strokes, and finally subcortical vascular dementia. DESIGN Cross-sectional study. PARTICIPANTS Thirty-eight CADASIL patients (19 to 61 years old; 20 in a prestroke group, 15 in a stroke group, and 3 in a dementia group), all with the R133C NOTCH3 mutation and including one homozygous patient, underwent a detailed ophthalmologic examination. METHODS Common cardiovascular risk factors were evaluated. Ophthalmologic examination included best-corrected visual acuity, anterior- and posterior-segment biomicroscopy, and measurement of intraocular pressure. In 33 patients and 16 healthy controls (20-64 years old), retinal fundus photographs were taken. Diameters of all arterioles and venules located in the area from 0.5 to 1.0 disc diameters from the optic disc margin were measured with a computer-based program and arteriole-to-venule (A/V) ratios were calculated from digitized photographs. RESULTS General arterial narrowing and arteriovenous nickings were common. Straightening of the retinal arterioles and a marked wall reflex (n = 6) occurred. The A/V ratio of CADASIL patients was significantly (P< 0.001) lower than that of controls. One patient had one retinal microinfarct and hemorrhages. The homozygous patient had a chorioretinal scar as a sign of circulatory deficiency. Anterior-segment changes included mild iris atrophy (n = 5) and various degrees of lens opacities. Visual acuity was normal in all but 2 patients, who had cataract and amblyopia. CONCLUSIONS The generalized arteriopathy of CADASIL causes a wide variety of changes in retinal arterioles but only minimal functional disturbances. These findings are consistent with alterations in arterioles in the cerebral cortex with which the retina and its arterioles are analogous, but contrast with the severe damage of cerebral white matter arterioles.
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Affiliation(s)
- Susanna Roine
- Department of Neurology, University and University Hospital of Turku, Turku, Finland.
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25
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Tedeschi-Reiner E, Strozzi M, Skoric B, Reiner Z. Relation of atherosclerotic changes in retinal arteries to the extent of coronary artery disease. Am J Cardiol 2005; 96:1107-9. [PMID: 16214446 DOI: 10.1016/j.amjcard.2005.05.070] [Citation(s) in RCA: 168] [Impact Index Per Article: 8.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 01/06/2005] [Revised: 05/31/2005] [Accepted: 05/31/2005] [Indexed: 11/26/2022]
Abstract
The aim of this study was to explore the relation between atherosclerosis of the retinal arteries and the extent and severity of coronary artery disease (CAD). In 109 patients, aged 40 to 80 years, who underwent coronary angiography for suspected CAD, the degree of retinal arterial atherosclerosis (stages 1 to 4 according to Scheie) was determined. The fundus examination was done using direct ophthalmoscopy by an ophthalmologist blinded to the extent of the CAD. The CAD extent was evaluated by Gensini score, and coronary angiograms were analyzed by 2 expert observers who had no knowledge of the patients' retinal artery status. The extent and severity of retinal vessel atherosclerosis correlated strongly with the extent and severity of CAD. Thus, atherosclerotic changes in the retinal arteries may be a predictor of the extent of CAD.
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Kim J, Oh YS, Shinn SH. Troglitazone reverses the inhibition of nitric oxide production by high glucose in cultured bovine retinal pericytes. Exp Eye Res 2005; 81:65-70. [PMID: 15978256 DOI: 10.1016/j.exer.2005.01.010] [Citation(s) in RCA: 12] [Impact Index Per Article: 0.6] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/15/2004] [Revised: 01/12/2005] [Accepted: 01/16/2005] [Indexed: 12/01/2022]
Abstract
In the retinal microcirculation, there is a basal release of nitric oxide (NO) which maintains the retinal blood flow. The proportions of endothelial cells and pericytes in the retinal capillaries are almost equal, so pericytes appear to play a important role in the regulation of microcirculatory hemodynamics in the retina. It has been suggested that the pathogenesis of early diabetic retinopathy may involve a reduced bioavailability or diminished production of NO. In this study, we investigated the role of troglitazone, a potent agonist of peroxisome proliferator activated receptor-gamma (PPARgamma) used for the treatment of diabetes, on the NO release and the effect of exposure to high glucose on the production of NO in cultured bovine retinal pericytes. Troglitazone significantly increased NO production and iNOS expression after 24hr in a dose-and PPARgamma-dependent manner. Elevation of D-glucose, but not L-glucose, from 5.5 to 30 mm for 24 hr decreased NO production, but co-treatment with troglitazone reversed high glucose-induced inhibition of NO production as well as iNOS expression. In conclusion, high glucose inhibits iNOS expression and subsequently NO synthesis in cultured bovine retinal pericytes, and troglitazone restores the NO production.
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Affiliation(s)
- Jaetaek Kim
- Division of Endocrinology and Metabolism, Department of Internal Medicine, College of Medicine, Chung-Ang University, Seoul, South Korea.
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27
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Knudsen LL. Ocular fluorophotometry in human subjects and in swine - with particular reference to long-term pharmacokinetics. ACTA ACUST UNITED AC 2002. [DOI: 10.1034/j.1600-0420.80.s235.1.x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
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Bek T, Ledet T. Vascular occlusion in diabetic retinopathy. A qualitative and quantitative histopathological study. ACTA OPHTHALMOLOGICA SCANDINAVICA 1996; 74:36-40. [PMID: 8689478 DOI: 10.1111/j.1600-0420.1996.tb00678.x] [Citation(s) in RCA: 15] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 02/01/2023]
Abstract
The retinal vessels from seven diabetic patients and from six age-matched normal controls were studied qualitatively and quantitatively using various histological staining techniques. In diabetic patients the walls of retinal arterioles and capillaries showed significantly more staining than normals for periodic acid Schiff (neutral glycoproteins), Sirius red (connective tissue), and for Alcian blue at pH 2.6, pH 5.8 and at pH 5.8 combined with MgCl22 in concentrations less than 0.9 M (acid mucopolysaccharides). In the retina from diabetic patients there was no difference between the number of capillaries staining with these dyes in areas of vascular occlusion, and in adjacent control areas. Furthermore, in areas of vascular occlusion, the material accumulated centrally to occlude the lumen of ghost vessels did not stain with any of the dyes used. A homogenous material, accumulated in the outer retina in areas of vascular occlusion in the retina from diabetic patients, only stained with Alcian blue at pH 5.8 combined with MgCl2 in concentrations less than 0.4 M, suggesting a different molecular composition from the Alcian blue material accumulated in the retinal vascular walls. The findings are in accordance with the knowledge that basement membranes of retinal vessels are thickened in diabetes mellitus. However, the findings also indicate that basement membrane thickening cannot fully account for vascular occlusion in diabetic retinopathy.
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Affiliation(s)
- T Bek
- Department of Ophthalmology, Arhus University Hospital, Denmark
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29
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Tilton RG. Capillary pericytes: perspectives and future trends. JOURNAL OF ELECTRON MICROSCOPY TECHNIQUE 1991; 19:327-44. [PMID: 1795186 DOI: 10.1002/jemt.1060190308] [Citation(s) in RCA: 82] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/28/2022]
Abstract
A complete understanding of the microcirculation requires full knowledge of the structure and function of each of the constituent cells, including pericytes. Vascular endothelium and smooth muscle cells have been investigated intensively during the last two decades, but much less is known about the metabolism and function of capillary pericytes. However, the development of new electron microscopy techniques and the application of new cell culture and molecular biology techniques should allow for the rapid elucidation of the cellular biochemistry and the microvascular function and pathology of this ubiquitous capillary cell.
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Affiliation(s)
- R G Tilton
- Department of Pathology, Washington University School of Medicine, St. Louis, Missouri 63110
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Krauss R. New technique to demonstrate the network of blood capillaries of the human retina in their three-dimensional arrangement. Graefes Arch Clin Exp Ophthalmol 1990; 228:187-90. [PMID: 2186975 DOI: 10.1007/bf00935731] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/30/2022] Open
Abstract
A method is presented that demonstrates the whole network of the blood capillaries of the human retina, making it possible (using a dark-field microscope at high magnification) to view the three-dimensional arrangement of this network in different planes by moving the drive of the microscope. The basic principle includes filling the vascular system with oxygen in statu nascendi by injection of H2O2 into the vitreous body of the intact eye and achieving fixation of the retinal tissue by application of a mixture of H2O2 and ethanol, and rendering the dry and flat retinal preparation transparent by soaking it in a specially prepared resin. The retinal vessels are made visible in an optically empty dark field by diffraction of light in a gas-filled specimen. This method allows preparation of the human retinal vasculature in simply enucleated eyes without cannulation of the central retinal artery and, therefore, it may be appropriate to support pathological and anatomical investigations.
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Affiliation(s)
- R Krauss
- Augenklinik, Rheinisch-Westfälischen Technischen Hochschule, Aachen, Federal Republic of Germany
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Krauss R. New technique to demonstrate the network of blood capillaries of the human retina in their three-dimensional arrangement. Graefes Arch Clin Exp Ophthalmol 1990. [DOI: 10.1007/bf02764316] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 10/22/2022] Open
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32
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Carlson EC. Human retinal capillary basement membrane leaflets are morphologically distinct: a correlated TEM and SEM analysis. Exp Eye Res 1989; 49:967-81. [PMID: 2558905 DOI: 10.1016/s0014-4835(89)80020-x] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/01/2023]
Abstract
Because retinal capillaries and their associated basement membranes (BMs) are significantly altered in a number of diseases (most notably diabetic retinopathy), the human retinal microvasculature is of interest to both basic scientists and clinicians. Consequently, numerous TEM studies centered primarily on cellular elements of retinal microvessels have been carried out. Ultrastructural studies emphasizing retinal capillary extracellular matrix (ECM) materials including BMs however, are nearly non-existent. Accordingly, the current correlated TEM/SEM investigation was undertaken. The study shows that retinal capillary walls are comprised of a continuous layer of endothelial cells and a discontinuous layer of intramural pericytes which are in frequent contact. These are underlain and/or surrounded by a retinal capillary BM complex which includes pericytic matrix, fibrillar collagen, and subendothelial, pericytic and Müller cell BM leaflets. Following sequential detergent treatment, all retinal cells are solubilized. Vessel ECM components, however, maintain their in vivo histoarchitectural relationships. Moreover, on the basis of substructure, susceptibility to non-specific proteases and anionic site density, BM leaflets are morphologically distinct. In addition, high-resolution SEM studies show that BM surface characteristics are tissue specific. It is concluded that retinal capillary BM complexes are comprised of structurally unique subcomponents the characteristics of which should be considered in future studies of retinal capillary BM structure, composition and function and particularly in investigations in which retinal capillaries are pathologically altered.
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Affiliation(s)
- E C Carlson
- Department of Anatomy and Cell Biology, School of Medicine, University of North Dakota, Grand Forks 58202
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Stone J, Dreher Z. Relationship between astrocytes, ganglion cells and vasculature of the retina. J Comp Neurol 1987; 255:35-49. [PMID: 3819008 DOI: 10.1002/cne.902550104] [Citation(s) in RCA: 230] [Impact Index Per Article: 6.2] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/07/2023]
Abstract
We have studied the distribution of astrocytes in the ganglion cell and nerve fibre layers of the retina in cat, rat, rabbit, and possum using anti-serum and a monoclonal antibody against glial fibrillary acidic protein (GFAP) and our own monoclonal antibody against glial filaments. The distribution of retinal astrocytes appears to be strongly determined by the vasculature of the retina; astrocytes are absent from almost all the retina of the possum and from the avascular regions of the rabbit retina. In the cat and rabbit, retinal astrocytes also show a strong affinity for the bundles of ganglion cell axons found at the inner surface of the retina. Retinal astrocytes do not invest the somas of ganglion cells, and even in areas of retina in which they are numerous, they are sharply confined to the layer of ganglion cell axons. It is suggested that retinal astrocytes are "immigrant" fibrous astrocytes that enter the retina with its vasculature.
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Burns MS, Bellhorn RW, Korte GE, Heriot WJ. Chapter 10 Plasticity of the retinal vasculature. ACTA ACUST UNITED AC 1986. [DOI: 10.1016/0278-4327(86)90013-1] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
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36
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Stefansson E, Landers MB, Wolbarsht ML. Oxygenation and Vasodilatation in Relation to Diabetic and Other Proliferative Retinopathies. Ophthalmic Surg Lasers Imaging Retina 1983. [DOI: 10.3928/1542-8877-19830301-01] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/20/2022]
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Hinds JW, McNelly NA. Capillaries in aging rat olfactory bulb: a quantitative light and electron microscopic analysis. Neurobiol Aging 1982; 3:197-207. [PMID: 7162549 DOI: 10.1016/0197-4580(82)90040-9] [Citation(s) in RCA: 32] [Impact Index Per Article: 0.8] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/23/2023]
Abstract
Olfactory bulbs from Charles River (Crl) rats from 3 to 36 months have been examined with light and electron microscopy. Total capillary length, surface, and volume, as well as number of endothelial cells, increases during the twofold increase in olfactory bulb volume from 3 to 18 months, but the relative density of these parameters shows no change during this time; from 18 to 36 months when neuronal cell body and dendrites are decreasing markedly in size, the relative density of capillaries shows only a modest decrease. Capillary lumen size and capillary wall thickness remain the same throughout life, but basal lamina thickness doubles from 3 to 24 months and then remains constant from 24 to 36 months. The incidence of several unusual ultrastructural features of the outer capillary basal lamina has been shown to increase with age.
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Slatter DH, Nelson AW, Young S, Stringer JM, Fisher MW. Retinal vessels of canine eyes at different ages--a qualitative and quantitative study. Exp Eye Res 1979; 28:369-79. [PMID: 446565 DOI: 10.1016/0014-4835(79)90112-x] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/15/2022]
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Roggendorf W, Cervós-Navarro J, Lazaro-Lacalle MD. Ultrastructure of venules in the cat brain. Cell Tissue Res 1978; 192:461-74. [PMID: 699028 DOI: 10.1007/bf00212326] [Citation(s) in RCA: 30] [Impact Index Per Article: 0.7] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/24/2022]
Abstract
Intracerebral venules of the cat were examined to establish criteria for a distinct separation between the venous and arterial system, and to characterize, in greater detail, the mural construction of individual venules. The intracerebral venules compared with those of other organs. Venules do not have a vascular wall composed clearly of endothelium, media, and adventitia, as is characteristic of arteries and arterioles. The venous endothlium has a similar structure to that of capillaries. The periendothelial cells of the venule differ in shape depending on the vascular diameter. The number of periendothelial cell processes in postcapillary venules increases progressively. Segments in which the basal lamina of the endothelium merges with that of the glia cover a smaller portion of the circumference than in venous capillary loops. In collecting venules, the endothelium is almost completely enveloped by periendothelial cells which have a larger number of filaments. There are no typical smooth muscle cells in the intracerebral venules. The perivascular space becomes wider in collecting venules, contains adventitial cells, phagocytes and a great number of collagen fibers.
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Carlson EC, Brendel K, Hjelle JT, Meezan E. Ultrastructural and biochemical analyses of isolated basement membranes from kidney glomeruli and tubules and brain and retinal microvessels. JOURNAL OF ULTRASTRUCTURE RESEARCH 1978; 62:26-53. [PMID: 564975 DOI: 10.1016/s0022-5320(78)80028-8] [Citation(s) in RCA: 120] [Impact Index Per Article: 2.6] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 12/23/2022]
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Abstract
A total of 110 arterioles were examined in the brains of cats; different sites were studied including the cortex, putamen, pons and crus cerebri. No internal elastic laminae were seen in the subendothelial space, although occasional fragments of elastic material were present in the larger arterioles. The media was composed of one, two or three layers of smooth muscle cells which interlocked in such a way that the vessel wall thickness was constant. Numerous tight junctions were seen between adjacent smooth muscle cells and between the endothelium and smooth muscle cells. Apart from the usual cell organelles, the smooth muscle cells of arterioles had numerous dense patches on the cell surface. The structure of the adventitia varied according to the diameter of the vessel and the site in the brain; it contained adventitial cells, bundles of collagen fibres and nerve fibres. Innervation of arterioles was more constant in the brain stem than in the cortex. Metarterioles had less specialised, atypical smooth muscle cells, a discontinuous media and numerous, extensive myoendothelial tight junctions; they were not innervated by nerve fibres. The diameter of metarterioles was less than 10 micronm whereas that of arterioles was 10-45 micronm. The possible functional aspects of arteriolar innervation are discussed.
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Abstract
Capillaries from bovine, monkey, and human retinas maintained in tissue culture produced a monolayer of cells. Autoradiographic and electron microscopic evidence indicated that the mural cells (intramural pericytes) were the cells that proliferated. Since intramural pericytes are damaged selectively in diabetes mellitus, their availability in culture will be useful in seeking means to control diabetic retinopathy.
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Abstract
We demonstrated the existence in the retina of an argyrophilic perivascular membrane comparable in all respects to that which exists throughout the vascular system. We compared our findings by light microscopy with those previously reported. We identified, by electron microscopy, the normal general location of the network between the basal laminae of the glial and vessel cells and demonstrated its selective staining with silver methenamine. These perivascular fibers, intercapillary strands, and bridges develop in relation to the process of retinal vascularization and the potential for forming these fibers is reactivated in senility and disease, as in diabetes. We summarized the evidence by concluding that these fibers are most likely composed of reticulin; it appears provable that in the past there may have been some confusion with neural fibers.
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Abstract
Meade, J. B., Whitwell, F., Bickford, B. J., and Waddington, J. K. B. (1974).Thorax,29, 1-15. Primary haemangiopericytoma of lung. Haemangiopericytoma is a rare neoplasm which may occur at any age and arise in almost any part of the body. At least 247 examples have been reported in the world literature, but only 24 appear to have arisen primarily in the lung. A summary of the features of these cases, collected from the literature, is presented, and four additional cases are described. The tumour may be innocent [ill] malignant, but there are no characteristic clinical or radiological features to distinguish it from other neoplasms of the lung. Because of uncertainty as to diagnosis and prognosis, surgical excision appears to be the treatment of choice. In the whole series of 28 cases, rather more than half (16) were female, and they tended to be older than the male patients. The mortality from recurrence was higher in males than in females (50% compared with 32%). The prognosis in general seems to be best with small, asymptomatic tumours, especially in female patients. A brief account is given of the nature and function of the pericyte. It was originally thought to be a cell of muscular type, but recent research suggests that it is a multipotent cell capable of development into other cell types and having phagocytic properties. It lies in the basement membrane of capillary blood vessels and may have some connection with antibody formation, but its exact function has not yet been elucidated.
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Ashton N, Tripathi B, Knight G. Effect of oxygen on the developing retinal vessels of the rabbit. I. Anatomy and development of the retinal vessels of the rabbit. Exp Eye Res 1972; 14:214-20. [PMID: 4640870 DOI: 10.1016/0014-4835(72)90006-1] [Citation(s) in RCA: 17] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/11/2023]
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Vegge T. A study of the ultrastructure of the small iris vessels in the vervet monkey (Ceropithecus aethiops). ZEITSCHRIFT FUR ZELLFORSCHUNG UND MIKROSKOPISCHE ANATOMIE (VIENNA, AUSTRIA : 1948) 1971; 123:195-208. [PMID: 4332349 DOI: 10.1007/bf02583473] [Citation(s) in RCA: 27] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/10/2023]
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48
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Daicker B. [The adventitional and intervascular reticulin fibers of the human retina]. ALBRECHT VON GRAEFES ARCHIV FUR KLINISCHE UND EXPERIMENTELLE OPHTHALMOLOGIE. ALBRECHT VON GRAEFE'S ARCHIVE FOR CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY 1971; 181:179-91. [PMID: 4930028 DOI: 10.1007/bf02390249] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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49
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Daicker B. [Hyperplasia of the adventitional and mural reticulin fibers in diabetic retinopathy]. ALBRECHT VON GRAEFES ARCHIV FUR KLINISCHE UND EXPERIMENTELLE OPHTHALMOLOGIE. ALBRECHT VON GRAEFE'S ARCHIVE FOR CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY 1971; 181:192-206. [PMID: 4930029 DOI: 10.1007/bf02390250] [Citation(s) in RCA: 4] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/13/2023]
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50
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Matsusaka T. The fine structure of retinal capillaries in normal and increased permeability as revealed by ruthenium red staining. ALBRECHT VON GRAEFES ARCHIV FUR KLINISCHE UND EXPERIMENTELLE OPHTHALMOLOGIE. ALBRECHT VON GRAEFE'S ARCHIVE FOR CLINICAL AND EXPERIMENTAL OPHTHALMOLOGY 1971; 183:140-51. [PMID: 4108800 DOI: 10.1007/bf00407179] [Citation(s) in RCA: 3] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/08/2023]
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