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Kaur J, Boyd ED, Ding G, Zhang L, Luo H, Li Q, Li L, Wei M, Landschoot-Ward J, Chopp M, Zhang Z, Jiang Q. The Association between Glymphatic System and Perivascular Macrophages in Brain Waste Clearance. Diagnostics (Basel) 2024; 14:731. [PMID: 38611644 PMCID: PMC11011895 DOI: 10.3390/diagnostics14070731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 03/13/2024] [Accepted: 03/14/2024] [Indexed: 04/14/2024] Open
Abstract
The glymphatic system suggests the convective bulk flow of cerebrospinal fluid (CSF) through perivascular spaces and the interstitial spaces of the brain parenchyma for the rapid removal of toxic waste solutes from the brain. However, the presence of convective bulk flow within the brain interstitial spaces is still under debate. We first addressed this argument to determine the involvement of the glymphatic system in brain waste clearance utilizing contrast-enhanced 3D T1-weighted imaging (T1WI), diffusion tensor imaging (DTI), and confocal microscopy imaging. Furthermore, perivascular macrophages (PVMs), which are immune cells located within perivascular spaces, have not been thoroughly explored for their association with the glymphatic system. Therefore, we investigated tracer uptake by PVMs in the perivascular spaces of both the arteries/arterioles and veins/venules and the potential association of PVMs in assisting the glymphatic system for interstitial waste clearance. Our findings demonstrated that both convective bulk flow and diffusion are responsible for the clearance of interstitial waste solutes from the brain parenchyma. Furthermore, our results suggested that PVMs may play an important function in glymphatic system-mediated interstitial waste clearance. The glymphatic system and PVMs could be targeted to enhance interstitial waste clearance in patients with waste-associated neurological conditions and aging.
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Affiliation(s)
- Jasleen Kaur
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
- Department of Physics, Oakland University, Rochester, MI 48309, USA
| | - Edward D. Boyd
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
- Department of Radiology, Michigan State University, East Lansing, MI 48824, USA
| | - Guangliang Ding
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
- Department of Radiology, Michigan State University, East Lansing, MI 48824, USA
| | - Li Zhang
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
- Department of Physiology, Michigan State University, East Lansing, MI 48824, USA
| | - Hao Luo
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
| | - Qingjiang Li
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
| | - Lian Li
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
| | - Min Wei
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
| | - Julie Landschoot-Ward
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
| | - Michael Chopp
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
- Department of Physics, Oakland University, Rochester, MI 48309, USA
- Department of Physiology, Michigan State University, East Lansing, MI 48824, USA
- Department of Neurology, Wayne State University, Detroit, MI 48202, USA
| | - Zhenggang Zhang
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
- Department of Physiology, Michigan State University, East Lansing, MI 48824, USA
- Department of Neurology, Wayne State University, Detroit, MI 48202, USA
| | - Quan Jiang
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
- Department of Physics, Oakland University, Rochester, MI 48309, USA
- Department of Radiology, Michigan State University, East Lansing, MI 48824, USA
- Department of Neurology, Wayne State University, Detroit, MI 48202, USA
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Tong XJ, Akdemir G, Wadhwa M, Verkman AS, Smith AJ. Large molecules from the cerebrospinal fluid enter the optic nerve but not the retina of mice. Fluids Barriers CNS 2024; 21:1. [PMID: 38178155 PMCID: PMC10768282 DOI: 10.1186/s12987-023-00506-4] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/24/2023] [Accepted: 12/21/2023] [Indexed: 01/06/2024] Open
Abstract
It has been proposed that cerebrospinal fluid (CSF) can enter and leave the retina and optic nerve along perivascular spaces surrounding the central retinal vessels as part of an aquaporin-4 (AQP4) dependent ocular 'glymphatic' system. Here, we injected fluorescent dextrans and antibodies into the CSF of mice at the cisterna magna and measured their distribution in the optic nerve and retina. We found that uptake of dextrans in the perivascular spaces and parenchyma of the optic nerve is highly sensitive to the cisternal injection rate, where high injection rates, in which dextran disperses fully in the sub-arachnoid space, led to uptake along the full length of the optic nerve. Accumulation of dextrans in the optic nerve did not differ significantly in wild-type and AQP4 knockout mice. Dextrans did not enter the retina, even when intracranial pressure was greatly increased over intraocular pressure. However, elevation of intraocular pressure reduced accumulation of fluorescent dextrans in the optic nerve head, and intravitreally injected dextrans left the retina via perivascular spaces surrounding the central retinal vessels. Human IgG distributed throughout the perivascular and parenchymal areas of the optic nerve to a similar extent as dextran following cisternal injection. However, uptake of a cisternally injected AQP4-IgG antibody, derived from a seropositive neuromyelitis optica spectrum disorder subject, was limited by AQP4 binding. We conclude that large molecules injected in the CSF can accumulate along the length of the optic nerve if they are fully dispersed in the optic nerve sub-arachnoid space but that they do not enter the retina.
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Affiliation(s)
- Xiao J Tong
- Department of Ophthalmology, University of California San Francisco, San Francisco, CA, 94131, USA
| | - Gokhan Akdemir
- Departments of Medicine and Physiology, University of California San Francisco, San Francisco, CA, 94131, USA
| | - Meetu Wadhwa
- Departments of Medicine and Physiology, University of California San Francisco, San Francisco, CA, 94131, USA
| | - Alan S Verkman
- Departments of Medicine and Physiology, University of California San Francisco, San Francisco, CA, 94131, USA
| | - Alex J Smith
- Department of Ophthalmology, University of California San Francisco, San Francisco, CA, 94131, USA.
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Wang X, Delle C, Peng W, Plá V, Giannetto M, Kusk P, Sigurdsson B, Sakurai S, Sweeney A, Sun Q, Du T, Libby RT, Nedergaard M. Age- and glaucoma-induced changes to the ocular glymphatic system. Neurobiol Dis 2023; 188:106322. [PMID: 37832797 DOI: 10.1016/j.nbd.2023.106322] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2023] [Revised: 10/11/2023] [Accepted: 10/11/2023] [Indexed: 10/15/2023] Open
Abstract
The ocular glymphatic system supports bidirectional fluid transport along the optic nerve, thereby removes metabolic wastes including amyloid-β. To better understand this biological process, we examined the distributions of intravitreally and intracisternally infused tracers in full-length optic nerves from different age groups of mice. Aging was linked to globally impaired ocular glymphatic fluid transport, similar to what has seen previously in the brain. Aging also reduced the pupillary responsiveness to light stimulation and abolished light-induced facilitation in anterograde ocular glymphatic flow. In contrast to normal aging, in the DBA/2 J model of glaucoma, we found a pathological increase of glymphatic fluid transport to the anterior optic nerve that was associated with dilation of the perivascular spaces. Thus, aging and glaucoma have fundamentally different effects on ocular glymphatic fluid transport. Manipulation of glymphatic fluid transport might therefore present a new target for the treatment of glaucoma.
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Affiliation(s)
- Xiaowei Wang
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark; Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA.
| | - Christine Delle
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
| | - Weiguo Peng
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark; Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA
| | - Virginia Plá
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
| | - Michael Giannetto
- Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA; Neuroscience Graduate Program, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA
| | - Peter Kusk
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
| | - Björn Sigurdsson
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
| | - Shinya Sakurai
- Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA
| | - Amanda Sweeney
- Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA
| | - Qian Sun
- Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA
| | - Ting Du
- Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA
| | - Richard T Libby
- Department of Ophthalmology, University of Rochester Medical Center, Elmwood Avenue 601, Rochester, NY 14642, USA
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark; Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA.
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Kaur J, Ding G, Zhang L, Lu Y, Luo H, Li L, Boyd E, Li Q, Wei M, Zhang Z, Chopp M, Jiang Q. Imaging glymphatic response to glioblastoma. Cancer Imaging 2023; 23:107. [PMID: 37904254 PMCID: PMC10614361 DOI: 10.1186/s40644-023-00628-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2023] [Accepted: 10/19/2023] [Indexed: 11/01/2023] Open
Abstract
BACKGROUND The glymphatic system actively exchanges cerebrospinal fluid (CSF) and interstitial fluid (ISF) to eliminate toxic interstitial waste solutes from the brain parenchyma. Impairment of the glymphatic system has been linked to several neurological conditions. Glioblastoma, also known as Glioblastoma multiforme (GBM) is a highly aggressive form of malignant brain cancer within the glioma category. However, the impact of GBM on the functioning of the glymphatic system has not been investigated. Using dynamic contrast-enhanced magnetic resonance imaging (CE-MRI) and advanced kinetic modeling, we examined the changes in the glymphatic system in rats with GBM. METHODS Dynamic 3D contrast-enhanced T1-weighted imaging (T1WI) with intra-cisterna magna (ICM) infusion of paramagnetic Gd-DTPA contrast agent was used for MRI glymphatic measurements in both GBM-induced and control rats. Glymphatic flow in the whole brain and the olfactory bulb was analyzed using model-derived parameters of arrival time, infusion rate, clearance rate, and residual that describe the dynamics of CSF tracer over time. RESULTS 3D dynamic T1WI data identified reduced glymphatic influx and clearance, indicating an impaired glymphatic system due to GBM. Kinetic modeling and quantitative analyses consistently indicated significantly reduced infusion rate, clearance rate, and increased residual of CSF tracer in GBM rats compared to control rats, suggesting restricted glymphatic flow in the brain with GBM. In addition, our results identified compromised perineural pathway along the optic nerves in GBM rats. CONCLUSIONS Our study demonstrates the presence of GBM-impaired glymphatic response in the rat brain and impaired perineural pathway along the optic nerves. Reduced glymphatic waste clearance may lead to the accumulation of toxic waste solutes and pro-inflammatory signaling molecules which may affect the progression of the GBM.
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Affiliation(s)
- Jasleen Kaur
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Physics, Oakland University, Rochester, MI, USA
| | - Guangliang Ding
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Radiology, Michigan State University, Lasing, MI, USA
| | - Li Zhang
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Physiology, Michigan State University, Lasing, MI, USA
| | - Yong Lu
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
| | - Hao Luo
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
| | - Lian Li
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
| | - Edward Boyd
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Radiology, Michigan State University, Lasing, MI, USA
| | - Qingjiang Li
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
| | - Min Wei
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
| | - Zhenggang Zhang
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Physiology, Michigan State University, Lasing, MI, USA
- Department of Neurology, Wayne State University, Detroit, MI, USA
| | - Michael Chopp
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Physics, Oakland University, Rochester, MI, USA
- Department of Physiology, Michigan State University, Lasing, MI, USA
- Department of Neurology, Wayne State University, Detroit, MI, USA
| | - Quan Jiang
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA.
- Department of Physics, Oakland University, Rochester, MI, USA.
- Department of Radiology, Michigan State University, Lasing, MI, USA.
- Department of Neurology, Wayne State University, Detroit, MI, USA.
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Kaur J, Boyd E, Ding G, Zhang L, Luo H, Li Q, Li L, Wei M, Landschoot-Ward J, Chopp M, Zhang Z, Jiang Q. The Association between Glymphatic System and Perivascular Macrophages in Brain Waste Clearance. Res Sq 2023:rs.3.rs-3390074. [PMID: 37886481 PMCID: PMC10602168 DOI: 10.21203/rs.3.rs-3390074/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
The glymphatic system suggests the convective bulk flow of cerebrospinal fluid (CSF) through perivascular spaces and the interstitial spaces of the brain parenchyma for the rapid removal of toxic waste solutes from the brain. However, the presence of convective bulk flow within the brain interstitial spaces is still under debate. We first addressed this argument to determine the involvement of the glymphatic system in brain waste clearance utilizing contrast-enhanced 3D T1-weighted imaging (T1WI), diffusion tensor imaging (DTI), and confocal microscopy imaging. Furthermore, perivascular macrophages (PVMs), which are immune cells located within perivascular spaces, have not been thoroughly explored for their association with the glymphatic system. Therefore, we investigated tracer uptake by PVMs in the perivascular spaces of both the arteries/arterioles and veins/venules and the potential association of PVMs in assisting the glymphatic system for interstitial waste clearance. Our findings demonstrated that both convective bulk flow and diffusion are responsible for the clearance of interstitial waste solutes from the brain parenchyma. Furthermore, our results suggested that PVMs play an important function in glymphatic system-mediated interstitial waste clearance. The glymphatic system and PVMs could be targeted to enhance interstitial waste clearance in patients with waste-associated neurological conditions and aging.
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Affiliation(s)
- Jasleen Kaur
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Physics, Oakland University, Rochester, MI, USA
| | - Edward Boyd
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Radiology, Michigan State University, Lasing, MI, USA
| | - Guangliang Ding
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Radiology, Michigan State University, Lasing, MI, USA
| | - Li Zhang
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Physiology, Michigan State University, Lasing, MI, USA
| | - Hao Luo
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
| | - Qingjiang Li
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
| | - Lian Li
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
| | - Min Wei
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
| | | | - Michael Chopp
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Physics, Oakland University, Rochester, MI, USA
- Department of Physiology, Michigan State University, Lasing, MI, USA
- Department of Neurology, Wayne State University, Detroit, MI, USA
| | - Zhenggang Zhang
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Physiology, Michigan State University, Lasing, MI, USA
- Department of Neurology, Wayne State University, Detroit, MI, USA
| | - Quan Jiang
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Physics, Oakland University, Rochester, MI, USA
- Department of Radiology, Michigan State University, Lasing, MI, USA
- Department of Neurology, Wayne State University, Detroit, MI, USA
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Clahsen T, Hadrian K, Notara M, Schlereth SL, Howaldt A, Prokosch V, Volatier T, Hos D, Schroedl F, Kaser-Eichberger A, Heindl LM, Steven P, Bosch JJ, Steinkasserer A, Rokohl AC, Liu H, Mestanoglu M, Kashkar H, Schumacher B, Kiefer F, Schulte-Merker S, Matthaei M, Hou Y, Fassbender S, Jantsch J, Zhang W, Enders P, Bachmann B, Bock F, Cursiefen C. The novel role of lymphatic vessels in the pathogenesis of ocular diseases. Prog Retin Eye Res 2023; 96:101157. [PMID: 36759312 DOI: 10.1016/j.preteyeres.2022.101157] [Citation(s) in RCA: 5] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/22/2022] [Revised: 12/13/2022] [Accepted: 12/17/2022] [Indexed: 02/10/2023]
Abstract
Historically, the eye has been considered as an organ free of lymphatic vessels. In recent years, however, it became evident, that lymphatic vessels or lymphatic-like vessels contribute to several ocular pathologies at various peri- and intraocular locations. The aim of this review is to outline the pathogenetic role of ocular lymphatics, the respective molecular mechanisms and to discuss current and future therapeutic options based thereon. We will give an overview on the vascular anatomy of the healthy ocular surface and the molecular mechanisms contributing to corneal (lymph)angiogenic privilege. In addition, we present (i) current insights into the cellular and molecular mechanisms occurring during pathological neovascularization of the cornea triggered e.g. by inflammation or trauma, (ii) the role of lymphatic vessels in different ocular surface pathologies such as dry eye disease, corneal graft rejection, ocular graft versus host disease, allergy, and pterygium, (iii) the involvement of lymphatic vessels in ocular tumors and metastasis, and (iv) the novel role of the lymphatic-like structure of Schlemm's canal in glaucoma. Identification of the underlying molecular mechanisms and of novel modulators of lymphangiogenesis will contribute to the development of new therapeutic targets for the treatment of ocular diseases associated with pathological lymphangiogenesis in the future. The preclinical data presented here outline novel therapeutic concepts for promoting transplant survival, inhibiting metastasis of ocular tumors, reducing inflammation of the ocular surface, and treating glaucoma. Initial data from clinical trials suggest first success of novel treatment strategies to promote transplant survival based on pretransplant corneal lymphangioregression.
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Affiliation(s)
- Thomas Clahsen
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany; Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany
| | - Karina Hadrian
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany; Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany
| | - Maria Notara
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany; Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany
| | - Simona L Schlereth
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany; Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany
| | - Antonia Howaldt
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Verena Prokosch
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Thomas Volatier
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Deniz Hos
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany; Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany
| | - Falk Schroedl
- Center for Anatomy and Cell Biology, Institute of Anatomy and Cell Biology - Salzburg, Paracelsus Medical University, Salzburg, Austria
| | - Alexandra Kaser-Eichberger
- Center for Anatomy and Cell Biology, Institute of Anatomy and Cell Biology - Salzburg, Paracelsus Medical University, Salzburg, Austria
| | - Ludwig M Heindl
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Philipp Steven
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany; Cluster of Excellence: Cellular Stress Responses in Ageing-Associated Diseases, CECAD, University of Cologne, Cologne, Germany
| | - Jacobus J Bosch
- Centre for Human Drug Research and Leiden University Medical Center, Leiden, the Netherlands
| | | | - Alexander C Rokohl
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Hanhan Liu
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Mert Mestanoglu
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Hamid Kashkar
- Institute for Molecular Immunology, Center for Molecular Medicine Cologne (CMMC), CECAD Research Center, Faculty of Medicine and University Hospital of Cologne, University of Cologne, Cologne, Germany
| | - Björn Schumacher
- Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany; Cluster of Excellence: Cellular Stress Responses in Ageing-Associated Diseases, CECAD, University of Cologne, Cologne, Germany
| | - Friedemann Kiefer
- European Institute for Molecular Imaging (EIMI), University of Münster, 48149, Münster, Germany
| | - Stefan Schulte-Merker
- Institute for Cardiovascular Organogenesis and Regeneration, Faculty of Medicine, WWU Münster, Münster, Germany
| | - Mario Matthaei
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Yanhong Hou
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany; Eye Institute and Department of Ophthalmology, Eye & ENT Hospital, Fudan University, 83 Fenyang Road, Xuhui District, Shanghai, China
| | - Sonja Fassbender
- IUF‒Leibniz Research Institute for Environmental Medicine, Duesseldorf, Germany; Immunology and Environment, Life & Medical Sciences (LIMES) Institute, University of Bonn, Bonn, Germany
| | - Jonathan Jantsch
- Institute for Medical Microbiology, Immunology and Hygiene, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Wei Zhang
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Philip Enders
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Björn Bachmann
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany
| | - Felix Bock
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany; Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany
| | - Claus Cursiefen
- Department of Ophthalmology, University of Cologne, Faculty of Medicine and University Hospital Cologne, University of Cologne, Cologne, Germany; Center for Molecular Medicine (CMMC), University of Cologne, Cologne, Germany; Cluster of Excellence: Cellular Stress Responses in Ageing-Associated Diseases, CECAD, University of Cologne, Cologne, Germany.
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Wostyn P, Killer HE. Normal-Tension Glaucoma: A Glymphopathy? Eye Brain 2023; 15:37-44. [PMID: 37056720 PMCID: PMC10086217 DOI: 10.2147/eb.s401306] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/08/2023] [Accepted: 03/07/2023] [Indexed: 04/15/2023] Open
Abstract
Glaucoma is one of the main causes of irreversible blindness in the world. The most common form, primary open-angle glaucoma, is an optic neuropathy that is characterized by a progressive loss of retinal ganglion cells and their axons, leading to structural changes in the optic nerve head and associated visual field defects. Elevated intraocular pressure remains the most important modifiable risk factor for primary open-angle glaucoma. However, a significant proportion of patients develop glaucomatous damage in the absence of increased intraocular pressure, a condition known as normal-tension glaucoma (NTG). The pathophysiology underlying NTG remains unclear. Several studies have revealed that vascular and cerebrospinal fluid (CSF) factors may play significant roles in the development of NTG. Vascular failure caused by functional or structural abnormalities, and compartmentation of the optic nerve subarachnoid space with disturbed CSF dynamics have been shown to be associated with NTG. In the present article, based on the concept of the glymphatic system and observations in patients with NTG, we hypothesize that failure of fluid transport via the glymphatic pathway in the optic nerve may be involved in the pathogenesis of some if not many cases of NTG. According to this hypothesis, vascular and CSF factors may share reduced glymphatic transport and perivascular waste clearance in the optic nerve as a final common pathway leading to the development of NTG. In addition, we speculate that some cases of NTG may reflect glymphatic dysfunction in natural brain aging and central nervous system diseases, such as Alzheimer's disease. Clearly, further studies are needed to gain additional insight into the relative contribution of these factors and conditions to reduced glymphatic transport in the optic nerve.
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Affiliation(s)
- Peter Wostyn
- Department of Psychiatry, PC Sint-Amandus, Beernem, Belgium
- Correspondence: Peter Wostyn, Department of Psychiatry, PC Sint-Amandus, Reigerlostraat 10, Beernem, 8730, Belgium, Tel +32-472713719, Fax +32-50-819720, Email
| | - Hanspeter Esriel Killer
- Department of Biomedicine, University of Basel, Basel, Switzerland
- Augenärzte Zentrum Aarau, Aarau, Switzerland
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8
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Xu Y, Cheng L, Yuan L, Yi Q, Xiao L, Chen H. Progress on Brain and Ocular Lymphatic System. Biomed Res Int 2022; 2022:6413553. [PMID: 36425338 PMCID: PMC9681545 DOI: 10.1155/2022/6413553] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/12/2022] [Revised: 09/11/2022] [Accepted: 10/26/2022] [Indexed: 02/06/2024]
Abstract
In recent years, 2 major discoveries have modified the traditional understanding of the brain. First, meningeal lymphatic vessels (MLV) were found in the dural sinus, which may absorb and drain cerebrospinal fluid (CSF). Second, the glymphatic system was discovered, composed of para-arterial CSF influx channel, paravenous interstitial fluid (ISF) efflux channel, and the water channel aquaporin-4 (AQP4) in astrocytes connecting the 2 channels. Accumulating evidence demonstrates that the lymphatic system of the brain plays a vital role within the circulation of CSF and, therefore, in the removal of metabolites. Therefore, it is involved in the incidence and development of some central nervous system (CNS) diseases. The optic nerve and retina are the extension of the CNS in the orbit. Whether they have a lymphatic system and how they clear the metabolites of the optic nerve and retina are still unclear. Recent studies have found that the ocular lymphatic system has a crucial impact on bounding eye diseases, like disorders of the optic nerve and retina. Therefore, here we review the recent research progress concerning the structure and function of MLV and glymphatic system. We also discuss the biomarkers for identification of lymphatic vessels, the composition of ocular lymphatic systems, and the possible association with diseases.
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Affiliation(s)
- Yang Xu
- Eye School of Chengdu University of TCM, Chengdu, China
- Key Laboratory of Sichuan Province Ophthalmopathy Prevention & Cure and Visual Function Protection, China
| | - Lu Cheng
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory of Ocular Fundus Diseases, Shanghai, China
- National Clinical Research Center for Eye Diseases, Shanghai, China
| | - Lu Yuan
- Eye School of Chengdu University of TCM, Chengdu, China
- Key Laboratory of Sichuan Province Ophthalmopathy Prevention & Cure and Visual Function Protection, China
| | - Qianya Yi
- Eye School of Chengdu University of TCM, Chengdu, China
- Key Laboratory of Sichuan Province Ophthalmopathy Prevention & Cure and Visual Function Protection, China
| | - Liuyi Xiao
- University of Electronic Science and Technology of China, Chengdu, China
| | - Hui Chen
- Eye School of Chengdu University of TCM, Chengdu, China
- Department of Ophthalmology, Shanghai General Hospital, Shanghai Jiao Tong University School of Medicine, Shanghai, China
- Shanghai Key Laboratory of Ocular Fundus Diseases, Shanghai, China
- National Clinical Research Center for Eye Diseases, Shanghai, China
- University of Electronic Science and Technology of China, Chengdu, China
- University of Shanghai for Science and Technology, Shanghai, China
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9
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Uddin N, Rutar M. Ocular Lymphatic and Glymphatic Systems: Implications for Retinal Health and Disease. Int J Mol Sci 2022; 23:10139. [PMID: 36077535 DOI: 10.3390/ijms231710139] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/31/2022] [Revised: 09/01/2022] [Accepted: 09/02/2022] [Indexed: 11/17/2022] Open
Abstract
Clearance of ocular fluid and metabolic waste is a critical function of the eye in health and disease. The eye has distinct fluid outflow pathways in both the anterior and posterior segments. Although the anterior outflow pathway is well characterized, little is known about posterior outflow routes. Recent studies suggest that lymphatic and glymphatic systems play an important role in the clearance of fluid and waste products from the posterior segment of the eye. The lymphatic system is a vascular network that runs parallel to the blood circulatory system. It plays an essential role in maintenance of fluid homeostasis and immune surveillance in the body. Recent studies have reported lymphatics in the cornea (under pathological conditions), ciliary body, choroid, and optic nerve meninges. The evidence of lymphatics in optic nerve meninges is, however, limited. An alternative lymphatic system termed the glymphatic system was recently discovered in the rodent eye and brain. This system is a glial cell-based perivascular network responsible for the clearance of interstitial fluid and metabolic waste. In this review, we will discuss our current knowledge of ocular lymphatic and glymphatic systems and their role in retinal degenerative diseases.
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10
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Abstract
The importance of the perivascular space (PVS) as one of the imaging markers of cerebral small vessel disease (CSVD) has been widely appreciated by the neuroradiologists. The PVS surrounds the small blood vessels in the brain and has a signal consistent with the cerebrospinal fluid (CSF) on MR. In a variety of physio-pathological statuses, the PVS may expand. The discovery of the cerebral glymphatic system has provided a revolutionary perspective to elucidate its pathophysiological mechanisms. Research on the function and pathogenesis of this system has become a prevalent topic among neuroradiologists. It is now believed that this system carries out the similar functions as the lymphatic system in other parts of the body and plays an important role in the removal of metabolic waste and the maintenance of homeostatic fluid circulation in the brain. In this article, we will briefly describe the composition of the cerebral glymphatic system, the influencing factors, the MR manifestations of the PVS and the related imaging technological advances. The aim of this research is to provide a reference for future clinical studies of the PVS and glymphatic system.
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Affiliation(s)
- Linya Yu
- Department of Radiology, The First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
| | - Xiaofei Hu
- Department of Radiology, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
| | - Haitao Li
- Department of Radiology, Southwest Hospital, Third Military Medical University (Army Medical University), Chongqing, China
- Haitao Li
| | - Yilei Zhao
- Department of Radiology, The First Affiliated Hospital, School of Medicine, Zhejiang University, Hangzhou, China
- *Correspondence: Yilei Zhao
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11
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Wostyn P, Killer HE. Further evidence for the presence of a glymphatic pathway in the human optic nerve. Surg Radiol Anat 2022; 44:767-768. [DOI: 10.1007/s00276-022-02936-5] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/08/2022] [Accepted: 03/30/2022] [Indexed: 11/29/2022]
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12
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Ong J, Tavakkoli A, Strangman G, Zaman N, Kamran SA, Zhang Q, Ivkovic V, Lee AG. Neuro-ophthalmic Imaging and Visual Assessment Technology for Spaceflight Associated Neuro-ocular Syndrome (SANS). Surv Ophthalmol 2022; 67:1443-1466. [DOI: 10.1016/j.survophthal.2022.04.004] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/15/2021] [Revised: 04/15/2022] [Accepted: 04/18/2022] [Indexed: 12/11/2022]
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13
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Wostyn P, Gibson CR, Mader TH. The odyssey of the ocular and cerebrospinal fluids during a mission to Mars: the "ocular glymphatic system" under pressure. Eye (Lond) 2022; 36:686-691. [PMID: 34373611 PMCID: PMC8956714 DOI: 10.1038/s41433-021-01721-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/03/2020] [Revised: 07/10/2021] [Accepted: 07/26/2021] [Indexed: 02/07/2023] Open
Abstract
A significant proportion of the astronauts who spend extended periods in microgravity develop ophthalmic abnormalities including optic disc edema, globe flattening, chorioretinal folds, and hyperopic refractive error shifts. A constellation of these neuro-ophthalmic findings has been termed "spaceflight-associated neuro-ocular syndrome". Understanding this syndrome is currently a top priority for NASA, especially in view of future long-duration missions (e.g., Mars missions). The recent discovery of an "ocular glymphatic system" can potentially help to unlock mechanisms underlying microgravity-induced optic disc edema. Indeed, a major paradigm shift is currently occurring in our understanding of transport of fluids and solutes through the optic nerve following the recent discovery of an optic nerve glymphatic pathway for influx of cerebrospinal fluid. In addition, the recent identification of an entirely new glymphatic pathway for efflux of ocular fluid may have profound implications for fluid dynamics in the eye. Observations pertaining to this ocular glymphatic pathway provide critical new insights into how intracranial pressure can alter basic fluid transport in the eye. We believe that these novel findings have the potential to be game changers in our understanding of the pathogenesis of optic disc edema in astronauts. In the present review, we integrate these new insights with findings on the intracranial and neuro-ophthalmologic effects of microgravity in one coherent conceptual framework. Further studies in this area of investigation could not only provide exciting new insights into the mechanisms underlying microgravity-induced optic disc edema but also offer opportunities to develop countermeasure strategies.
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Affiliation(s)
- Peter Wostyn
- Department of Psychiatry, PC Sint-Amandus, Beernem, Belgium
| | - Charles Robert Gibson
- Coastal Eye Associates, Webster, TX USA ,grid.481680.30000 0004 0634 8729KBR, NASA Space Medicine Operations Division, Houston, TX USA
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14
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Abstract
Long-term exposure to microgravity and space radiation leads to physiological and pathological changes in human biology. Pathological neuro-ocular changes are collected under the name spaceflight-associated neuro-ocular syndrome. This review examines studies on the effects of microgravity and space radiation on the ocular structures and their results. In addition, we discuss treatment methods and hypotheses to reduce the effects of microgravity and space radiation on biological structures.
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Affiliation(s)
| | - Gökhan Öğretmenoğlu
- Adana City Training and Research Hospital, Clinic of Ophthalmology, Adana, Turkey
| | - Şansal Gedik
- Selçuk University Faculty of Medicine, Department of Ophthalmology, Konya, Turkey
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15
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Zheng C, Liu S, Zhang X, Hu Y, Shang X, Zhu Z, Huang Y, Wu G, Xiao Y, Du Z, Liang Y, Chen D, Zang S, Hu Y, He M, Zhang X, Yu H. Shared genetic architecture between the two neurodegenerative diseases: Alzheimer's disease and glaucoma. Front Aging Neurosci 2022; 14:880576. [PMID: 36118709 PMCID: PMC9476600 DOI: 10.3389/fnagi.2022.880576] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/21/2022] [Accepted: 07/13/2022] [Indexed: 02/05/2023] Open
Abstract
BACKGROUND Considered as the representatives of neurodegenerative diseases, Alzheimer's disease (AD) and glaucoma are complex progressive neuropathies affected by both genetic and environmental risk factors and cause irreversible damages. Current research indicates that there are common features between AD and glaucoma in terms of epidemiology and pathophysiology. However, the understandings and explanations of their comorbidity and potential genetic overlaps are still limited and insufficient. METHOD Genetic pleiotropy analysis was performed using large genome-wide association studies summary statistics of AD and glaucoma, with an independent cohort of glaucoma for replication. Conditional and conjunctional false discovery rate methods were applied to identify the shared loci. Biological function and network analysis, as well as the expression level analysis were performed to investigate the significance of the shared genes. RESULTS A significant positive genetic correlation between AD and glaucoma was identified, indicating that there were significant polygenetic overlaps. Forty-nine shared loci were identified and mapped to 11 shared protein-coding genes. Functional genomic analyses of the shared genes indicate their modulation of critical physiological processes in human cells, including those occurring in the mitochondria, nucleus, and cellular membranes. Most of the shared genes indicated a potential modulation of metabolic processes in human cells and tissues. Furthermore, human protein-protein interaction network analyses revealed that some of the shared genes, especially MTCH2, NDUFS3, and PTPMT1, as well as SPI1 and MYBPC3, may function concordantly. The modulation of their expressions may be related to metabolic dysfunction and pathogenic processes. CONCLUSION Our study identified a shared genetic architecture between AD and glaucoma, which may explain their shared features in epidemiology and pathophysiology. The potential involvement of these shared genes in molecular and cellular processes reflects the "inter-organ crosstalk" between AD and glaucoma. These results may serve as a genetic basis for the development of innovative and effective therapeutics for AD, glaucoma, and other neurodegenerative diseases.
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Affiliation(s)
- Chunwen Zheng
- Shantou University Medical College, Shantou, China
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Shunming Liu
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Xiayin Zhang
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Yunyan Hu
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Xianwen Shang
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Zhuoting Zhu
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Yu Huang
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Guanrong Wu
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Yu Xiao
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Zijing Du
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Yingying Liang
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Daiyu Chen
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Siwen Zang
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Yijun Hu
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Mingguang He
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
- State Key Laboratory of Ophthalmology, Zhongshan Ophthalmic Center, Sun Yat-sen University, Guangzhou, China
- Centre for Eye Research Australia, Royal Victorian Eye and Ear Hospital, East Melbourne, VIC, Australia
| | - Xueli Zhang
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
- Medical Research Center, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
| | - Honghua Yu
- Guangdong Eye Institute, Department of Ophthalmology, Guangdong Provincial People’s Hospital, Guangdong Academy of Medical Sciences, Guangzhou, China
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16
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Abstract
Optic nerve health is essential for proper function of the visual system. However, the pathophysiology of certain neurodegenerative disease processes affecting the optic nerve, such as glaucoma, is not fully understood. Recently, it was hypothesized that a lack of proper clearance of neurotoxins contributes to neurodegenerative diseases. The ability to clear metabolic waste is essential for tissue homeostasis in mammals, including humans. While the brain lacks the traditional lymphatic drainage system identified in other anatomical regions, there is growing evidence of a glymphatic system in the central nervous system, which structurally includes the optic nerve. Named to acknowledge the supportive role of astroglial cells, this perivascular fluid drainage system is essential to remove toxic metabolites from the central nervous system. Herein, we review existing literature describing the physiology and dysfunction of the glymphatic system specifically as it relates to the optic nerve. We summarize key imaging studies demonstrating the existence of a glymphatic system in the optic nerves of wild-type rodents, aquaporin 4-null rodents, and humans; glymphatic imaging studies in diseases where the optic nerve is impaired; and current evidence regarding pharmacological and lifestyle interventions that may help promote glymphatic function to improve optic nerve health. We conclude by highlighting future research directions that could be applied to improve imaging detection and guide therapeutic interventions for diseases affecting the optic nerve.
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Affiliation(s)
- Anisha Kasi
- Department of Ophthalmology, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, NY, USA
| | - Crystal Liu
- Department of Ophthalmology, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, NY, USA
| | - Muneeb A Faiq
- Department of Ophthalmology, NYU Grossman School of Medicine, NYU Langone Health, New York University, New York, NY, USA
| | - Kevin C Chan
- Department of Ophthalmology; Department of Radiology; Neuroscience Institute, NYU Grossman School of Medicine, NYU Langone Health; Center for Neural Science, College of Arts and Science, New York University, New York, NY, USA
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17
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Kaur J, Fahmy LM, Davoodi-Bojd E, Zhang L, Ding G, Hu J, Zhang Z, Chopp M, Jiang Q. Waste Clearance in the Brain. Front Neuroanat 2021; 15:665803. [PMID: 34305538 PMCID: PMC8292771 DOI: 10.3389/fnana.2021.665803] [Citation(s) in RCA: 25] [Impact Index Per Article: 8.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 06/15/2021] [Indexed: 12/15/2022] Open
Abstract
Waste clearance (WC) is an essential process for brain homeostasis, which is required for the proper and healthy functioning of all cerebrovascular and parenchymal brain cells. This review features our current understanding of brain WC, both within and external to the brain parenchyma. We describe the interplay of the blood-brain barrier (BBB), interstitial fluid (ISF), and perivascular spaces within the brain parenchyma for brain WC directly into the blood and/or cerebrospinal fluid (CSF). We also discuss the relevant role of the CSF and its exit routes in mediating WC. Recent discoveries of the glymphatic system and meningeal lymphatic vessels, and their relevance to brain WC are highlighted. Controversies related to brain WC research and potential future directions are presented.
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Affiliation(s)
- Jasleen Kaur
- Department of Neurology, Henry Ford Health System, Detroit, MI, United States
- Department of Physics, Oakland University, Rochester, MI, United States
| | - Lara M. Fahmy
- Department of Neurology, Henry Ford Health System, Detroit, MI, United States
- Department of Psychiatry and Behavioral Neurosciences, Wayne State University, Detroit, MI, United States
| | - Esmaeil Davoodi-Bojd
- Department of Neurology, Henry Ford Health System, Detroit, MI, United States
- Department of Radiology, Henry Ford Health System, Detroit, MI, United States
| | - Li Zhang
- Department of Neurology, Henry Ford Health System, Detroit, MI, United States
| | - Guangliang Ding
- Department of Neurology, Henry Ford Health System, Detroit, MI, United States
| | - Jiani Hu
- Department of Radiology, Wayne State University, Detroit, MI, United States
| | - Zhenggang Zhang
- Department of Neurology, Henry Ford Health System, Detroit, MI, United States
- Department of Neurology, Wayne State University, Detroit, MI, United States
| | - Michael Chopp
- Department of Neurology, Henry Ford Health System, Detroit, MI, United States
- Department of Physics, Oakland University, Rochester, MI, United States
| | - Quan Jiang
- Department of Neurology, Henry Ford Health System, Detroit, MI, United States
- Department of Physics, Oakland University, Rochester, MI, United States
- Department of Neurology, Wayne State University, Detroit, MI, United States
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18
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Kumaria A, Gruener AM, Dow GR, Smith SJ, Macarthur DC, Ingale HA. An explanation for Terson syndrome at last: the glymphatic reflux theory. J Neurol 2021; 269:1264-1271. [PMID: 34170402 DOI: 10.1007/s00415-021-10686-4] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/30/2021] [Revised: 06/20/2021] [Accepted: 06/21/2021] [Indexed: 10/21/2022]
Abstract
Terson Syndrome (TS) describes the presence of intraocular hemorrhage in patients with intracranial hemorrhage, typically subarachnoid hemorrhage. Despite TS being a well-defined and frequently occurring phenomenon, its pathophysiology remains controversial. This review will present the current understanding of TS, with view to describing a contemporary and more plausible pathomechanism of TS, given recent advances in ophthalmic science and neurobiology. Previously proposed theories include a sudden rise in intracranial pressure (ICP) transmitted to the optic nerve sheath leading to rupture of retinal vessels; or intracranial blood extending to the orbit via the optic nerve sheath. The origin of blood in TS is uncertain, but retinal vessels appear to be an unlikely source. In addition, an anatomical pathway for blood to enter the eye from the intracranial space remains poorly defined. An ocular glymphatic system has recently been described, drainage of which from the globe into intracranial glymphatics is reliant on the pressure gradient between intraocular pressure and intracranial pressure. The glymphatic pathway is the only extravascular anatomical conduit between the subarachnoid space and the retina. We propose that subarachnoid blood in skull base cisterns near the optic nerve is the substrate of blood in TS. Raised ICP causes it to be refluxed through glymphatic channels into the globe, resulting in intraocular hemorrhage. We herewith present glymphatic reflux as an alternative theory to explain the phenomenon of Terson Syndrome.
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Affiliation(s)
- Ashwin Kumaria
- Department of Neurosurgery, Queen's Medical Centre, Nottingham University Hospitals NHS Trust, Derby Road, Nottingham, NG7 2UH, UK.
| | - Anna M Gruener
- School of Medicine, University of Nottingham, Nottingham, UK.,Department of Ophthalmology, Queen's Medical Centre, Nottingham University Hospitals NHS Trust, Nottingham, UK
| | - Graham R Dow
- Department of Neurosurgery, Queen's Medical Centre, Nottingham University Hospitals NHS Trust, Derby Road, Nottingham, NG7 2UH, UK
| | - Stuart J Smith
- Department of Neurosurgery, Queen's Medical Centre, Nottingham University Hospitals NHS Trust, Derby Road, Nottingham, NG7 2UH, UK.,School of Medicine, University of Nottingham, Nottingham, UK
| | - Donald C Macarthur
- Department of Neurosurgery, Queen's Medical Centre, Nottingham University Hospitals NHS Trust, Derby Road, Nottingham, NG7 2UH, UK.,School of Medicine, University of Nottingham, Nottingham, UK
| | - Harshal A Ingale
- Department of Neurosurgery, Queen's Medical Centre, Nottingham University Hospitals NHS Trust, Derby Road, Nottingham, NG7 2UH, UK
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19
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Wang X, Lou N, Eberhardt A, Yang Y, Kusk P, Xu Q, Förstera B, Peng S, Shi M, Ladrón-de-Guevara A, Delle C, Sigurdsson B, Xavier ALR, Ertürk A, Libby RT, Chen L, Thrane AS, Nedergaard M. An ocular glymphatic clearance system removes β-amyloid from the rodent eye. Sci Transl Med 2021; 12:12/536/eaaw3210. [PMID: 32213628 DOI: 10.1126/scitranslmed.aaw3210] [Citation(s) in RCA: 111] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2018] [Revised: 08/24/2019] [Accepted: 12/30/2019] [Indexed: 12/31/2022]
Abstract
Despite high metabolic activity, the retina and optic nerve head lack traditional lymphatic drainage. We here identified an ocular glymphatic clearance route for fluid and wastes via the proximal optic nerve in rodents. β-amyloid (Aβ) was cleared from the retina and vitreous via a pathway dependent on glial water channel aquaporin-4 (AQP4) and driven by the ocular-cranial pressure difference. After traversing the lamina barrier, intra-axonal Aβ was cleared via the perivenous space and subsequently drained to lymphatic vessels. Light-induced pupil constriction enhanced efflux, whereas atropine or raising intracranial pressure blocked efflux. In two distinct murine models of glaucoma, Aβ leaked from the eye via defects in the lamina barrier instead of directional axonal efflux. The results suggest that, in rodents, the removal of fluid and metabolites from the intraocular space occurs through a glymphatic pathway that might be impaired in glaucoma.
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Affiliation(s)
- Xiaowei Wang
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark.,Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA
| | - Nanhong Lou
- Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA
| | - Allison Eberhardt
- Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA
| | - Yujia Yang
- Center for Eye Disease and Development, Vision Science Graduate Program, and School of Optometry, University of California Berkeley, Berkeley, CA 94720, USA
| | - Peter Kusk
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
| | - Qiwu Xu
- Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA
| | - Benjamin Förstera
- Institute for Stroke and Dementia Research, Klinikum der Universität München, Ludwig Maximilians University of Munich (LMU), 81377 Munich, Germany.,Institute for Tissue Engineering and Regenerative Medicine (iTERM), Helmholtz Center München, 85764 Munich, Germany
| | - Sisi Peng
- Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA
| | - Meng Shi
- Center for Eye Disease and Development, Vision Science Graduate Program, and School of Optometry, University of California Berkeley, Berkeley, CA 94720, USA
| | - Antonio Ladrón-de-Guevara
- Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA
| | - Christine Delle
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
| | - Björn Sigurdsson
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
| | - Anna L R Xavier
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark
| | - Ali Ertürk
- Institute for Stroke and Dementia Research, Klinikum der Universität München, Ludwig Maximilians University of Munich (LMU), 81377 Munich, Germany.,Institute for Tissue Engineering and Regenerative Medicine (iTERM), Helmholtz Center München, 85764 Munich, Germany
| | - Richard T Libby
- Department of Ophthalmology, University of Rochester Medical Center, Rochester, NY 14642, USA
| | - Lu Chen
- Center for Eye Disease and Development, Vision Science Graduate Program, and School of Optometry, University of California Berkeley, Berkeley, CA 94720, USA.
| | - Alexander S Thrane
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark.,Department of Ophthalmology, Haukeland University Hospital, Jonas Lies Vei 65, 5021 Bergen, Norway
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, Faculty of Medical and Health Sciences, University of Copenhagen, Blegdamsvej 3B, 2200 Copenhagen N, Denmark. .,Center for Translational Neuromedicine, University of Rochester Medical School, Elmwood Avenue 601, Rochester, NY 14642, USA
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20
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Hanekamp S, Ćurčić-Blake B, Caron B, McPherson B, Timmer A, Prins D, Boucard CC, Yoshida M, Ida M, Hunt D, Jansonius NM, Pestilli F, Cornelissen FW. White matter alterations in glaucoma and monocular blindness differ outside the visual system. Sci Rep 2021; 11:6866. [PMID: 33767217 PMCID: PMC7994383 DOI: 10.1038/s41598-021-85602-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/11/2020] [Accepted: 02/15/2021] [Indexed: 01/23/2023] Open
Abstract
The degree to which glaucoma has effects in the brain beyond the eye and the visual pathways is unclear. To clarify this, we investigated white matter microstructure (WMM) in 37 tracts of patients with glaucoma, monocular blindness, and controls. We used brainlife.io for reproducibility. White matter tracts were subdivided into seven categories ranging from those primarily involved in vision (the visual white matter) to those primarily involved in cognition and motor control. In the vision tracts, WMM was decreased as measured by fractional anisotropy in both glaucoma and monocular blind subjects compared to controls, suggesting neurodegeneration due to reduced sensory inputs. A test-retest approach was used to validate these results. The pattern of results was different in monocular blind subjects, where WMM properties increased outside the visual white matter as compared to controls. This pattern of results suggests that whereas in the monocular blind loss of visual input might promote white matter reorganization outside of the early visual system, such reorganization might be reduced or absent in glaucoma. The results provide indirect evidence that in glaucoma unknown factors might limit the reorganization as seen in other patient groups following visual loss.
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Affiliation(s)
- Sandra Hanekamp
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA.
- Department of Intelligent Systems Engineering, Luddy School of Informatics and Engineering, Indiana University, Bloomington, IN, USA.
- Department of Psychology, The University of Texas at Austin, Austin, TX, USA.
| | - Branislava Ćurčić-Blake
- Department of Biomedical Sciences of Cells and Systems, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Bradley Caron
- Program in Neuroscience, Indiana University, Bloomington, IN, USA
- Program in Vision Science, School of Optometry, Indiana University, Bloomington, IN, USA
| | - Brent McPherson
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA
| | - Anneleen Timmer
- Laboratory for Experimental Ophthalmology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Doety Prins
- Laboratory for Experimental Ophthalmology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Christine C Boucard
- Department of Ophthalmology, Jikei University School of Medicine, Tokyo, Japan
| | - Masaki Yoshida
- Department of Ophthalmology, Jikei University School of Medicine, Tokyo, Japan
| | - Masahiro Ida
- Department of Radiology, National Hospital Organization Mito Medical Center, Ibaraki, Japan
| | - David Hunt
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA
| | - Nomdo M Jansonius
- Laboratory for Experimental Ophthalmology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
| | - Franco Pestilli
- Department of Psychological and Brain Sciences, Indiana University, Bloomington, IN, USA.
- Department of Intelligent Systems Engineering, Luddy School of Informatics and Engineering, Indiana University, Bloomington, IN, USA.
- Department of Psychology, The University of Texas at Austin, Austin, TX, USA.
- Program in Neuroscience, Indiana University, Bloomington, IN, USA.
- Program in Vision Science, School of Optometry, Indiana University, Bloomington, IN, USA.
| | - Frans W Cornelissen
- Laboratory for Experimental Ophthalmology, University Medical Center Groningen, University of Groningen, Groningen, The Netherlands
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21
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Tsutsumi S, Ono H, Ishii H. Hyperintense areas in the intraorbital optic nerve evaluated by T2-weighted magnetic resonance imaging: a glymphatic pathway? Surg Radiol Anat 2021; 43:1273-1278. [PMID: 33399917 DOI: 10.1007/s00276-020-02649-7] [Citation(s) in RCA: 7] [Impact Index Per Article: 2.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/03/2020] [Accepted: 12/04/2020] [Indexed: 01/27/2023]
Abstract
PURPOSE The present study aimed to explore the glymphatic pathway in the intraorbital optic nerve (ON) using magnetic resonance imaging (MRI). METHODS Following conventional MRI examination, a total of 89 outpatients underwent T2-weighted imaging in thin-sliced coronal and sagittal sections. Moreover, three injected cadaver heads were dissected. RESULTS In the cadaver specimens, differences in appearance between the central and peripheral parts of the ON were not observed. On the axial T2-weighted MRI performed in the initial examination, the central part of the intraorbital ONs was delineated as a well-demarcated, linear hyperintense area in 19% of patients. On the thin-sliced serial coronal images, the hyperintense areas were identified on both sides in 91% of patients. They were delineated as continuous hyperintense areas in the ONs with an inconsistent appearance even in the same nerve. In 12.4% of patients, the areas were divided into the upper and lower parts by a horizontal septum, while others showed variable morphologies, lacking a septum. On thin-sliced sagittal images, hyperintense areas were identified in 46% of patients. CONCLUSION Hyperintense areas in the intraorbital ON detected on T2-weighted sequences may involve a glymphatic pathway with perivascular spaces of the ON and central retinal artery. These may be collapsed and difficult to identify on surgical and cadaver specimens.
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Affiliation(s)
- Satoshi Tsutsumi
- Department of Neurological Surgery, Juntendo University Urayasu Hospital, 2-1-1 Tomioka, Urayasu, Chiba, 279-0021, Japan.
| | - Hideo Ono
- Division of Radiological Technology, Medical Satellite Yaesu Clinic, Tokyo, Japan
| | - Hisato Ishii
- Department of Neurological Surgery, Juntendo University Urayasu Hospital, 2-1-1 Tomioka, Urayasu, Chiba, 279-0021, Japan
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22
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Jacobsen HH, Sandell T, Jørstad ØK, Moe MC, Ringstad G, Eide PK. In Vivo Evidence for Impaired Glymphatic Function in the Visual Pathway of Patients With Normal Pressure Hydrocephalus. Invest Ophthalmol Vis Sci 2020; 61:24. [PMID: 33201186 PMCID: PMC7683855 DOI: 10.1167/iovs.61.13.24] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/11/2022] Open
Abstract
Purpose Impaired ability to remove toxic metabolites from central nervous system may be an important link between cerebral and ophthalmic degenerative diseases. The aim of the present study was to compare the glymphatic function in the visual pathway in patients with idiopathic normal pressure hydrocephalus (iNPH), a neurodegenerative dementia subtype, with a reference group. Methods We compared 31 subjects with Definite iNPH (i.e., shunt-responsive) with 13 references in a prospective and observational study. After intrathecal injection of the magnetic contrast agent gadobutrol (Gadovist, 0.5 mL, 1.0 mmol/mL, Bayer Pharma AG), serving as a tracer, consecutive magnetic resonance imaging (MRI) scans were obtained (next 24-48 hours). The normalized MRI T1 signal recorded in the cerebrospinal fluid (CSF) and along the visual pathway served as a semi-quantitative measure of tracer enrichment. Gadobutrol does not penetrate the blood-brain barrier and is thus confined to the extravascular space. Overnight measurements of pulsatile intracranial pressure were used as a surrogate marker for the intracranial compliance. Results The tracer enriched the prechiasmatic cistern similarly in both groups, but clearance was delayed in the iNPH group. Moreover, both delayed enrichment and clearance of the tracer were observed in the visual pathway in the iNPH subjects. The enrichment in the visual pathway and the CSF correlated. Individuals with elevated pulsatile intracranial pressure showed reduced enrichment within the visual pathway. Conclusions There was delayed enrichment and clearance of a tracer in the visual pathway of iNPH patients, which suggests impaired glymphatic function in the visual pathway in this disease.
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Affiliation(s)
- Henrik Holvin Jacobsen
- Department of Ophthalmology, Oslo University Hospital, Oslo, Norway.,Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Tiril Sandell
- Department of Ophthalmology, Oslo University Hospital, Oslo, Norway.,Department of Ophthalmology, Vestre Viken Hospital, Drammen, Norway
| | | | - Morten C Moe
- Department of Ophthalmology, Oslo University Hospital, Oslo, Norway.,Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Geir Ringstad
- Division of Radiology and Nuclear Medicine, Department of Radiology, Oslo University Hospital-Rikshospitalet, Oslo, Norway
| | - Per Kristian Eide
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Neurosurgery, Oslo University Hospital-Rikshospitalet, Oslo, Norway
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23
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Wostyn P. The "ocular glymphatic clearance system": a key missing piece of the Alzheimer's disease-glaucoma puzzle found? Eye (Lond) 2021; 35:1281. [PMID: 32518395 DOI: 10.1038/s41433-020-1008-8] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/26/2020] [Revised: 05/23/2020] [Accepted: 05/26/2020] [Indexed: 11/08/2022] Open
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Singh AK, Verma S. Use of ocular biomarkers as a potential tool for early diagnosis of Alzheimer's disease. Indian J Ophthalmol 2020; 68:555-561. [PMID: 32174567 PMCID: PMC7210832 DOI: 10.4103/ijo.ijo_999_19] [Citation(s) in RCA: 16] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2019] [Revised: 09/10/2019] [Accepted: 10/26/2019] [Indexed: 02/05/2023] Open
Abstract
Alzheimer's disease (AD) is the most common neurodegenerative disease worldwide which unfortunately has no known effective cure to date. Despite many clinical trials indicating the effectiveness of preclinical treatment, a sensitive tool for screening of AD is yet to be developed. Due to multiple similarities between ocular and the brain tissue, the eye is being explored by researchers for this purpose, with utmost attention focused on the retinal tissue. Besides visual functional impairment, neuronal degeneration and apoptosis, retinal nerve fiber degeneration, increase in the cup-to-disc ratio, and retinal vascular thinning and tortuosity are the changes observed in the retinal tissue which are related to AD. Studies have shown that targeting these changes in the retina is an effective way of reducing the degeneration of retinal neuronal tissue. Similar mechanisms of neurodegeneration have been demonstrated in the brain and the eyes of AD patients. Multiple studies are underway to investigate the potential of diagnosing AD and detection of amyloid-β (Aβ) levels in the retinal tissue. Since the tissues in the anterior segment of the eye are more accessible for in vivo imaging and examination, they have more potential as screening biomarkers. This article provides a concise review of available literature on the ocular biomarkers in anterior and posterior segments of the eye including the cornea, aqueous humour (AH), crystalline lens, and retina in AD. This review will also highlight the newer technological tools available for the detection of potential biomarkers in the eye for early diagnosis of AD.
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Affiliation(s)
- Ajay K Singh
- Consultant and Anterior Segment Surgeon, Department of Ophthalmology, Asian Institute of Medical Sciences, Faridabad, Haryana, India
| | - Shilpa Verma
- WNS Global Services Pvt. Ltd., Gurugram, Haryana, India
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25
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Abstract
The central nervous system (CNS) was previously thought to be the only organ system lacking lymphatic vessels to remove waste products from the interstitial space. Recently, based on the results from animal experiments, the glymphatic system was hypothesized. In this hypothesis, cerebrospinal fluid (CSF) enters the periarterial spaces, enters the interstitial space of the brain parenchyma via aquaporin-4 (AQP4) channels in the astrocyte end feet, and then exits through the perivenous space, thereby clearing waste products. From the perivenous space, the interstitial fluid drains into the subarachnoid space and meningeal lymphatics of the parasagittal dura. It has been reported that the glymphatic system is particularly active during sleep. Impairment of glymphatic system function might be a cause of various neurodegenerative diseases such as Alzheimer’s disease, normal pressure hydrocephalus, glaucoma, and others. Meningeal lymphatics regulate immunity in the CNS. Many researchers have attempted to visualize the function and structure of the glymphatic system and meningeal lymphatics in vivo using MR imaging. In this review, we aim to summarize these in vivo MR imaging studies and discuss the significance, current limitations, and future directions. We also discuss the significance of the perivenous cyst formation along the superior sagittal sinus, which is recently discovered in the downstream of the glymphatic system.
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Affiliation(s)
- Shinji Naganawa
- Department of Radiology, Nagoya University Graduate School of Medicine
| | - Toshiaki Taoka
- Department of Radiology, Nagoya University Graduate School of Medicine
- Department of Innovative Biomedical Visualization (iBMV), Nagoya University Graduate School of Medicine
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26
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Alkabie S, Lange A, Manogaran P, Stoessl AJ, Costello F, Barton JJS. Optical coherence tomography of patients with Parkinson's disease and progressive supranuclear palsy. Clin Neurol Neurosurg 2019; 189:105635. [PMID: 31855622 DOI: 10.1016/j.clineuro.2019.105635] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2018] [Revised: 11/23/2019] [Accepted: 12/07/2019] [Indexed: 01/28/2023]
Abstract
OBJECTIVES To determine if Parkinson's disease (PD) and progressive supranuclear palsy (PSP) differed on retinal measurements using optical coherence tomography (OCT). PATIENTS AND METHODS In a prospective, controlled, cross-sectional cohort study, we recruited patients with PD or PSP for more than three years, as well as control subjects. We measured peripapillary retinal nerve fiber layer (RNFL) thickness and macular volume using spectral-domain OCT. The association between these OCT measures and the disease characteristics of duration and disability were examined using a linear mixed effect model. RESULTS We analyzed eyes from n = 12 PD patients, n = 11 PSP patients, and n = 12 control subjects. RNFL thickness was reduced in eyes from patients with PSP, but there were no differences in macular volume between groups. RNFL thickness and macular volume were not significantly different between eyes from patients with PD and controls. Worse disability was associated with reduced macular volumes. CONCLUSION PSP but not PD is associated with thinning of the peripapillary RNFL when symptoms have been present for more than three years.
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Affiliation(s)
- Samir Alkabie
- Division of Neurology, University of British Columbia, Vancouver, BC, Canada; Department of Neurology, State University of New York Downstate Medical Center, Brooklyn, NY, USA; Department of Neurology, Kings County Hospital, Brooklyn, NY, USA.
| | - Alex Lange
- Neuro-ophthalmology, Department of Ophthalmology, University of British Columbia, Vancouver, BC, Canada; Vista Klinik, Vista Diagnostics and Laser Vista, Binningen, Switzerland
| | - Praveena Manogaran
- Department of Neurology, University Hospital Zurich and University of Zurich, Zurich, Switzerland; Department of Information Technology and Electrical Engineering, Swiss Federal Institute of Technology, Zurich, Switzerland
| | - A Jon Stoessl
- Division of Neurology, University of British Columbia, Vancouver, BC, Canada
| | - Fiona Costello
- Neuro-ophthalmology, Department of Clinical Neurosciences and Surgery, University of Calgary, Hotchkiss Brain Institute, Calgary, Alberta, Canada
| | - Jason J S Barton
- Neuro-ophthalmology, Department of Ophthalmology, University of British Columbia, Vancouver, BC, Canada
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27
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Jacobsen HH, Ringstad G, Jørstad ØK, Moe MC, Sandell T, Eide PK. The Human Visual Pathway Communicates Directly With the Subarachnoid Space. Invest Ophthalmol Vis Sci 2019; 60:2773-2780. [PMID: 31247084 DOI: 10.1167/iovs.19-26997] [Citation(s) in RCA: 32] [Impact Index Per Article: 6.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/24/2022] Open
Abstract
Purpose Explore in vivo whether there is direct communication between the cerebrospinal fluid (CSF) and extravascular compartment of human visual pathway structures. Methods A prospective and observational study included 10 subjects who underwent intrathecal gadolinium-enhanced magnetic resonance imaging (MRI) for suspected CSF circulation disorder, but with a negative result and with no known ophthalmic diseases. After precontrast T1-weighted MRI, 0.5 mL of gadobutrol (Gadovist, 1.0 mmol/mL) was injected intrathecally. Gadobutrol distributes in the extravascular space, and served as a CSF tracer. Consecutive MRI scans were obtained throughout 24 to 48 hours. To assess gadobutrol contrast enrichment, regions of interest (ROIs) were placed at multiple locations along the visual pathway, from the primary visual cortex to the eye's vitreous body. CSF tracer dependent T1 signal was measured in each ROI. A linear mixed-model was used for statistical analyses. Results CSF tracer enrichment was found within the optic nerve, optic chiasm, optic tract, and primary visual cortex (P < 0.001). Peak tracer enrichment in the visual pathway generally occurred after 24 hours and was preceded by peak enhancement in the prechiasmatic cistern after 4 to 6 hours. Conclusions The results indicate direct communication between CSF of subarachnoid space and the extravascular space of the human visual pathway. Extravascular entry of the CSF tracer is a prerequisite for a glymphatic system, the present findings may suggest its presence. The existence of a glymphatic system in the human visual pathway could bring novel perspectives on the pathophysiology and treatment of ophthalmic diseases.
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Affiliation(s)
- Henrik Holvin Jacobsen
- Department of Ophthalmology, Oslo University Hospital, Oslo, Norway.,Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Geir Ringstad
- Division of Radiology and Nuclear Medicine, Department of Radiology, Oslo University Hospital, Rikshospitalet, Oslo, Norway
| | - Øystein Kalsnes Jørstad
- Department of Ophthalmology, Oslo University Hospital, Oslo, Norway.,Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Morten C Moe
- Department of Ophthalmology, Oslo University Hospital, Oslo, Norway.,Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Tiril Sandell
- Department of Ophthalmology, Oslo University Hospital, Oslo, Norway
| | - Per Kristian Eide
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Neurosurgery, Oslo University Hospital, Rikshospitalet, Oslo, Norway
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28
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Wostyn P, De Deyn PP. The retinal nerve fiber layer as a window to the glymphatic system. Clin Neurol Neurosurg 2019; 188:105593. [PMID: 31756617 DOI: 10.1016/j.clineuro.2019.105593] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.2] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2019] [Revised: 10/30/2019] [Accepted: 11/09/2019] [Indexed: 11/17/2022]
Affiliation(s)
- Peter Wostyn
- Department of Psychiatry, PC Sint-Amandus, Reigerlostraat 10, 8730 Beernem, Belgium.
| | - Peter Paul De Deyn
- Department of Biomedical Sciences, Laboratory of Neurochemistry and Behavior, Institute Born-Bunge, University of Antwerp, Universiteitsplein 1, 2610 Antwerp, Belgium; Department of Neurology and Alzheimer Research Center, University of Groningen and University Medical Center Groningen, Hanzeplein 1, 9700 RB Groningen, the Netherlands; Department of Neurology and Memory Clinic, Middelheim General Hospital (ZNA), Lindendreef 1, 2020 Antwerp, Belgium
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29
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Wostyn P, Mader TH, Gibson CR, Killer HE. The perivascular space of the central retinal artery as a potential major cerebrospinal fluid inflow route: implications for optic disc edema in astronauts. Eye (Lond) 2019; 34:779-780. [PMID: 31541218 DOI: 10.1038/s41433-019-0594-9] [Citation(s) in RCA: 7] [Impact Index Per Article: 1.4] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/12/2019] [Accepted: 09/03/2019] [Indexed: 11/09/2022] Open
Affiliation(s)
- Peter Wostyn
- Department of Psychiatry, PC Sint-Amandus, Beernem, Belgium.
| | | | | | - Hanspeter Esriel Killer
- Department of Ophthalmology, Cantonal Hospital Aarau, Aarau, Switzerland.,Department of Biomedicine, University of Basel, Basel, Switzerland
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31
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Wostyn P, Mader TH, Gibson CR, Killer HE. The escape of retrobulbar cerebrospinal fluid in the astronaut's eye: mission impossible? Eye (Lond) 2019; 33:1519-1524. [PMID: 31065103 DOI: 10.1038/s41433-019-0453-8] [Citation(s) in RCA: 19] [Impact Index Per Article: 3.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/18/2018] [Revised: 04/04/2019] [Accepted: 04/08/2019] [Indexed: 01/22/2023] Open
Abstract
Ophthalmic abnormalities including unilateral and bilateral optic disc edema, optic nerve sheath distention, globe flattening, choroidal folds, and hyperopic shifts have been observed in astronauts during and after long-duration spaceflight. An increased understanding of factors contributing to this syndrome, termed spaceflight-associated neuro-ocular syndrome, is currently a top priority for the ESA and NASA, especially since this medical obstacle could impact the visual health of astronauts as well as the success of future missions, including continued trips to the International Space Station, a return to the moon, or a future human mission to Mars. Currently, the exact mechanisms causing this neuro-ocular syndrome are not fully understood. In the present paper, we propose a hypothetical framework by which optic disc edema in astronauts may result, at least partly, from the forcing of perioptic cerebrospinal fluid into the optic nerve and optic disc along perivascular spaces surrounding the central retinal vessels, related to long-standing microgravity fluid shifts and variations in optic nerve sheath anatomy and compliance. Although this hypothesis remains speculative at the present time, future research in this area of investigation could not only provide exciting new insights into the mechanisms underlying microgravity-induced optic disc swelling but also offer opportunities to develop countermeasure strategies.
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Affiliation(s)
- Peter Wostyn
- Department of Psychiatry, PC Sint-Amandus, Beernem, Belgium.
| | | | | | - Hanspeter Esriel Killer
- Department of Ophthalmology, Cantonal Hospital Aarau, Aarau, Switzerland.,Department of Biomedicine, University of Basel, Basel, Switzerland
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32
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Wostyn P. Glaucoma as a dangerous interplay between ocular fluid and cerebrospinal fluid. Med Hypotheses 2019; 127:97-99. [PMID: 31088658 DOI: 10.1016/j.mehy.2019.04.008] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.6] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/19/2019] [Revised: 04/09/2019] [Accepted: 04/12/2019] [Indexed: 01/03/2023]
Abstract
Glaucoma is a leading cause of irreversible blindness worldwide. Primary open-angle glaucoma, the most common type, is characterized by progressive degeneration of retinal ganglion cells and their axons in the optic nerve, resulting in progressive deterioration of visual fields. The optic nerve head is generally considered to be the primary site of axonal injury in glaucoma. Although the pathophysiology of glaucomatous optic neuropathy is not well understood, elevated intraocular pressure is considered the most important modifiable risk factor. However, in normal-tension glaucoma, intraocular pressure is not elevated and thus other risk factors must also be involved in the optic neuropathy of primary open-angle glaucoma. Several studies reported significantly lower intracranial pressure in patients with glaucoma compared with healthy subjects, suggesting that low intracranial pressure may result in a high pressure difference across the lamina cribrosa, influencing the physiology and pathophysiology of the optic nerve head by the effect of a mechanical force. Moreover, a rapidly evolving literature suggests the existence of an 'ocular glymphatic system'. This opens up new ways to understand the mechanisms underlying a range of ocular diseases such as glaucoma. In the present paper, I hypothesize that an imbalance between intraocular pressure and intracranial pressure, apart from generating mechanical forces at the lamina cribrosa, may lead to a dangerous interplay between ocular fluid and cerebrospinal fluid resulting in impaired cerebrospinal fluid entry into the optic nerve subarachnoid space and optic nerve perivascular spaces, and the perivascular space surrounding the central retinal artery in particular, thereby inhibiting glymphatic clearance of waste products from the retrobulbar or retrolaminar portion of the optic nerve. Should further research demonstrate that the proposed viewpoint is largely correct, it would hold great potential for our understanding of glaucomatous optic nerve damage and would have important implications for diagnosis and therapy of this devastating disorder.
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Affiliation(s)
- Peter Wostyn
- Department of Psychiatry, PC Sint-Amandus, Reigerlostraat 10, 8730 Beernem, Belgium.
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33
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Abstract
The glymphatic system has emerged as an important player in central nervous system (CNS) diseases, by regulating the vasculature impairment, effectively controlling the clearance of toxic peptides, modulating activity of astrocytes, and being involved in the circulation of neurotransmitters in the brain. Recently, several studies have indicated decreased activity of the glymphatic pathway under diabetes conditions such as in insulin resistance and hyperglycemia. Furthermore, diabetes leads to the disruption of the blood-brain barrier and decrease of apolipoprotein E (APOE) expression and the secretion of norepinephrine in the brain, involving the impairment of the glymphatic pathway and ultimately resulting in cognitive decline. Considering the increased prevalence of diabetes-induced dementia worldwide, the relationship between the glymphatic pathway and diabetes-induced dementia should be investigated and the mechanisms underlying their relationship should be discussed to promote the development of an effective therapeutic approach in the near future. Here, we have reviewed recent evidence for the relationship between glymphatic pathway dysfunction and diabetes. We highlight that the enhancement of the glymphatic system function during sleep may be beneficial to the attenuation of neuropathology in diabetes-induced dementia. Moreover, we suggest that improving glymphatic system activity may be a potential therapeutic strategy for the prevention of diabetes-induced dementia.
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Affiliation(s)
- Young-Kook Kim
- Department of Biochemistry, Chonnam National University Medical School, Gwangju, South Korea.,Department of Biomedical Sciences, Center for Creative Biomedical Scientists, Chonnam National University, Gwangju, South Korea
| | - Kwang Il Nam
- Department of Anatomy, Chonnam National University Medical School, Gwangju, South Korea
| | - Juhyun Song
- Department of Biomedical Sciences, Center for Creative Biomedical Scientists, Chonnam National University, Gwangju, South Korea.,Department of Anatomy, Chonnam National University Medical School, Gwangju, South Korea
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34
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35
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Yao F, Zhang E, Gao Z, Ji H, Marmouri M, Xia X. Did you choose appropriate tracer for retrograde tracing of retinal ganglion cells? The differences between cholera toxin subunit B and Fluorogold. PLoS One 2018; 13:e0205133. [PMID: 30289890 PMCID: PMC6173421 DOI: 10.1371/journal.pone.0205133] [Citation(s) in RCA: 18] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/04/2018] [Accepted: 09/19/2018] [Indexed: 12/31/2022] Open
Abstract
Cholera toxin subunit B (CTB) and Fluorogold(FG) are two widely utilized retrograde tracers to assess the number and function of retinal ganglion cells (RGCs). However, the relative advantages and disadvantages of these tracers remain unclear, which may lead to their inappropriate application. In this study, we compared these tracers by separately injecting the tracer into the superior Colliculi (SC) in rats, one or 2 weeks later, the rats were sacrificed, and their retinas, brains, and optic nerves were collected. From the first to second week, FG displayed a greater number of labeled RGCs and a larger diffusion area in the SC than CTB; The number of CTB labeled RGCs and the diffusion area of CTB in the SC increased significantly, but there was no distinction between FG; Furthermore, CTB exhibited more labeled RGC neurites and longer neurites than FG, but no difference was evident between the same trace; The optic nerves labeled using CTB were much clearer than those labeled using FG. In conclusion, both CTB and FG can be used for the retrograde labeling of RGCs in rats at 1 or 2 weeks. FG achieves retrograde labeling of a greater number of RGCs than CTB, whereas CTB better delineates the morphology of RGCs. Furthermore, CTB seems more suitable for retrograde labeling of some small, non-image forming nuclei in the brain to which certain RGC subtypes project their axons.
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Affiliation(s)
- Fei Yao
- Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Endong Zhang
- Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Zhaolin Gao
- Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Hongpei Ji
- Department of Ophthalmology, The People’s Hospital of Guizhou Province, Guiyang, Guizhou, China
| | - Mahmoud Marmouri
- Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, Hunan, China
| | - Xiaobo Xia
- Department of Ophthalmology, Xiangya Hospital, Central South University, Changsha, Hunan, China
- * E-mail:
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Wostyn P, Van Dam D, De Deyn PP. Intracranial pressure and glaucoma: Is there a new therapeutic perspective on the horizon? Med Hypotheses 2018; 118:98-102. [DOI: 10.1016/j.mehy.2018.06.026] [Citation(s) in RCA: 8] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2018] [Revised: 06/18/2018] [Accepted: 06/27/2018] [Indexed: 11/24/2022]
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Colligris P, Perez de Lara MJ, Colligris B, Pintor J. Ocular Manifestations of Alzheimer's and Other Neurodegenerative Diseases: The Prospect of the Eye as a Tool for the Early Diagnosis of Alzheimer's Disease. J Ophthalmol 2018; 2018:8538573. [PMID: 30151279 PMCID: PMC6091327 DOI: 10.1155/2018/8538573] [Citation(s) in RCA: 44] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Track Full Text] [Download PDF] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/02/2018] [Revised: 06/07/2018] [Accepted: 06/26/2018] [Indexed: 12/20/2022] Open
Abstract
Dementia, including Alzheimer's disease (AD), is a major disorder, leading to several ocular manifestations amongst the elderly population. These visual disorders may be due to retinal nerve degenerative changes, including nerve fibre layer thinning, degeneration of retinal ganglion cells, and changes to vascular parameters. There is no cure for Alzheimer's, but medicines can slow down the development of many of the classic symptoms, such as loss of memory and communication skills, mood swings, and depression. The disease diagnosis is difficult, and it is only possible through PET scans of the brain, detecting evidence of the accumulation of amyloid and tau. PET is expensive and invasive, requiring the injection of radioactive tracers, which bind with these proteins and glow during scanning. Recently, scientists developed promising eye-scan techniques that may detect Alzheimer's disease at its earliest stage, before major symptoms appear, leading to improved management of the disease symptoms. In this review, we are discussing the visual abnormalities of Alzheimer's and other neurodegenerative diseases, focused on ocular functional-visual-structural biomarkers, retinal pathology, and potential novel diagnostic tools.
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Affiliation(s)
- Pade Colligris
- Universidad Alfonso X, Madrid, Spain
- Ocupharm Diagnostics SL, Madrid, Spain
| | | | - Basilio Colligris
- Ocupharm Diagnostics SL, Madrid, Spain
- Universidad Complutense de Madrid, Madrid, Spain
| | - Jesus Pintor
- Ocupharm Diagnostics SL, Madrid, Spain
- Universidad Complutense de Madrid, Madrid, Spain
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Abstract
PURPOSE OF REVIEW A pressure difference between the intraocular and intracranial compartments at the site of the lamina cribrosa has been hypothesized to have a pathophysiological role in several optic nerve head diseases. This paper reviews the current literature on the translamina cribrosa pressure difference (TLCPD), the associated pressure gradient, and its potential pathophysiological role, as well as the methodology to assess TLCPD. RECENT FINDINGS For normal-tension glaucoma (NTG), initial studies indicated low intracranial pressure (ICP) while recent findings indicate that a reduced ICP is not mandatory. Data from studies on the elevated TLCPD as a pathophysiological factor of NTG are equivocal. From the identification of potential postural effects on the cerebrospinal fluid (CSF) communication between the intracranial and retrolaminar space, we hypothesize that the missing link could be a dysfunction of an occlusion mechanism of the optic nerve sheath around the optic nerve. In upright posture, this could cause an elevated TLCPD even with normal ICP and we suggest that this should be investigated as a pathophysiological component in NTG patients.
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Affiliation(s)
- Gauti Jóhannesson
- Department of Clinical Sciences, Ophthalmology, Umeå University, Umeå, Sweden. .,Wallenberg Centre for Molecular Medicine, Umeå University, Umeå, Sweden.
| | - Anders Eklund
- Department of Radiation Sciences, Biomedical Engineering, Umeå University, Umeå, Sweden
| | - Christina Lindén
- Department of Clinical Sciences, Ophthalmology, Umeå University, Umeå, Sweden
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Wostyn P, Killer HE, De Deyn PP. Why a One-Way Ticket to Mars May Result in a One-Way Directional Glymphatic Flow to the Eye. J Neuroophthalmol 2017; 37:462-3. [PMID: 28991101 DOI: 10.1097/WNO.0000000000000578] [Citation(s) in RCA: 11] [Impact Index Per Article: 1.8] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/25/2022]
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May CA, Rutkowski P. Hypothesis: Watershed zones in the human eye are a key for understanding glaucomatous retinal damage. Med Hypotheses 2017; 109:1-5. [PMID: 29150265 DOI: 10.1016/j.mehy.2017.09.009] [Citation(s) in RCA: 1] [Impact Index Per Article: 0.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/05/2017] [Revised: 09/07/2017] [Accepted: 09/14/2017] [Indexed: 11/22/2022]
Abstract
The pathogenesis of glaucoma is complex which has led to numerous hypothesizes concerning the important factors creating this specific type of inner retinal degeneration namely apoptosis of retinal ganglion cells. We favor a primary vascular etiology and provide evidence that the pathogenesis of glaucoma should not be confined to changes exclusively at the optic nerve head but must include changes occurring in the peripheral retina with particular emphasis on the watershed zones of both the retina and choroid. This focus may help to sharpen ones awareness for early glaucoma treatment particularly in patients with minimal findings suggestive of glaucoma.
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Bacyinski A, Xu M, Wang W, Hu J. The Paravascular Pathway for Brain Waste Clearance: Current Understanding, Significance and Controversy. Front Neuroanat 2017; 11:101. [PMID: 29163074 PMCID: PMC5681909 DOI: 10.3389/fnana.2017.00101] [Citation(s) in RCA: 91] [Impact Index Per Article: 13.0] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/09/2017] [Accepted: 10/24/2017] [Indexed: 12/03/2022] Open
Abstract
The paravascular pathway, also known as the “glymphatic” pathway, is a recently described system for waste clearance in the brain. According to this model, cerebrospinal fluid (CSF) enters the paravascular spaces surrounding penetrating arteries of the brain, mixes with interstitial fluid (ISF) and solutes in the parenchyma, and exits along paravascular spaces of draining veins. Studies have shown that metabolic waste products and solutes, including proteins involved in the pathogenesis of neurodegenerative diseases such as amyloid-beta, may be cleared by this pathway. Consequently, a growing body of research has begun to explore the association between glymphatic dysfunction and various disease states. However, significant controversy exists in the literature regarding both the direction of waste clearance as well as the anatomical space in which the waste-fluid mixture is contained. Some studies have found no evidence of interstitial solute clearance along the paravascular space of veins. Rather, they demonstrate a perivascular pathway in which waste is cleared from the brain along an anatomically distinct perivascular space in a direction opposite to that of paravascular flow. Although possible explanations have been offered, none have been able to fully reconcile the discrepancies in the literature, and many questions remain. Given the therapeutic potential that a comprehensive understanding of brain waste clearance pathways might offer, further research and clarification is highly warranted.
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Affiliation(s)
- Andrew Bacyinski
- School of Medicine, Wayne State University, Detroit, MI, United States
| | - Maosheng Xu
- Department of Radiology, The First Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, China
| | - Wei Wang
- Department of Radiology, The First Affiliated Hospital of Zhejiang Chinese Medical University, Hangzhou, China
| | - Jiani Hu
- Department of Radiology, Wayne State University, Detroit, MI, United States
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Wostyn P, De Deyn PP. Intracranial pressure-induced optic nerve sheath response as a predictive biomarker for optic disc edema in astronauts. Biomark Med 2017; 11:1003-1008. [PMID: 28869392 DOI: 10.2217/bmm-2017-0218] [Citation(s) in RCA: 13] [Impact Index Per Article: 1.9] [Reference Citation Analysis] [What about the content of this article? (0)] [Affiliation(s)] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 11/21/2022] Open
Abstract
A significant proportion of the astronauts who spend extended periods in microgravity develop ophthalmic abnormalities. Understanding this syndrome, called visual impairment and intracranial pressure (VIIP), has become a high priority for National Aeronautics and Space Administration, especially in view of future long-duration missions (e.g., Mars missions). Moreover, to ensure selection of astronaut candidates who will be able to complete long-duration missions with low risk of the VIIP syndrome, it is imperative to identify biomarkers for VIIP risk prediction. Here, we hypothesize that the optic nerve sheath response to alterations in intracranial pressure may be a potential predictive biomarker for optic disc edema in astronauts. If confirmed, this biomarker could be used for preflight identification of astronauts at risk for developing VIIP-associated optic disc edema.
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Affiliation(s)
- Peter Wostyn
- Department of Psychiatry, PC Sint-Amandus, 8730 Beernem, Belgium
| | - Peter Paul De Deyn
- Laboratory of Neurochemistry & Behavior, Institute Born-Bunge, University of Antwerp, Department of Biomedical Sciences, 2610 Antwerp, Belgium.,Department of Neurology & Alzheimer Research Center, University of Groningen & University Medical Center Groningen, 9700 RB Groningen, The Netherlands.,Department of Neurology & Memory Clinic, Middelheim General Hospital (ZNA), 2020 Antwerp, Belgium
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Wostyn P, De Groot V, Van Dam D, Audenaert K, Killer HE, De Deyn PP. The Glymphatic Hypothesis of Glaucoma: A Unifying Concept Incorporating Vascular, Biomechanical, and Biochemical Aspects of the Disease. Biomed Res Int 2017; 2017:5123148. [PMID: 28948167 DOI: 10.1155/2017/5123148] [Citation(s) in RCA: 36] [Impact Index Per Article: 5.1] [Reference Citation Analysis] [What about the content of this article? (0)] [Abstract] [Track Full Text] [Download PDF] [Figures] [Subscribe] [Scholar Register] [Received: 05/20/2017] [Accepted: 08/01/2017] [Indexed: 10/29/2022]
Abstract
The pathophysiology of primary open-angle glaucoma is still largely unknown, although a joint contribution of vascular, biomechanical, and biochemical factors is widely acknowledged. Since glaucoma is a leading cause of irreversible blindness worldwide, exploring its underlying pathophysiological mechanisms is extremely important and challenging. Evidence from recent studies appears supportive of the hypothesis that a "glymphatic system" exists in the eye and optic nerve, analogous to the described "glymphatic system" in the brain. As discussed in the present paper, elucidation of a glymphatic clearance pathway in the eye could provide a new unifying hypothesis of glaucoma that can incorporate many aspects of the vascular, biomechanical, and biochemical theories of the disease. It should be stressed, however, that the few research data currently available cannot be considered as proof of the existence of an "ocular glymphatic system" and that much more studies are needed to validate this possibility. Even though nothing conclusive can yet be said, the recent reports suggesting a paravascular transport system in the eye and optic nerve are encouraging and, if confirmed, may offer new perspectives for the development of novel diagnostic and therapeutic strategies for this devastating disorder.
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Wostyn P, De Groot V, Van Dam D, Audenaert K, Killer HE, De Deyn PP. Evidence for the existence of a communication between the eye and the brain? Acta Neurochir (Wien) 2017; 159:1413-1414. [PMID: 28516362 DOI: 10.1007/s00701-017-3218-9] [Citation(s) in RCA: 2] [Impact Index Per Article: 0.3] [Reference Citation Analysis] [What about the content of this article? (0)] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/13/2017] [Accepted: 05/09/2017] [Indexed: 01/22/2023]
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Affiliation(s)
- Dong An
- Lions Eye Institute, Nedlands, Western Australia, Australia
| | | | - Dao-Yi Yu
- Lions Eye Institute, Nedlands, Western Australia, Australia
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