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van Veluw SJ, Benveniste H, Bakker ENTP, Carare RO, Greenberg SM, Iliff JJ, Lorthois S, Van Nostrand WE, Petzold GC, Shih AY, van Osch MJP. Is CAA a perivascular brain clearance disease? A discussion of the evidence to date and outlook for future studies. Cell Mol Life Sci 2024; 81:239. [PMID: 38801464 PMCID: PMC11130115 DOI: 10.1007/s00018-024-05277-1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/14/2023] [Revised: 04/20/2024] [Accepted: 05/13/2024] [Indexed: 05/29/2024]
Abstract
The brain's network of perivascular channels for clearance of excess fluids and waste plays a critical role in the pathogenesis of several neurodegenerative diseases including cerebral amyloid angiopathy (CAA). CAA is the main cause of hemorrhagic stroke in the elderly, the most common vascular comorbidity in Alzheimer's disease and also implicated in adverse events related to anti-amyloid immunotherapy. Remarkably, the mechanisms governing perivascular clearance of soluble amyloid β-a key culprit in CAA-from the brain to draining lymphatics and systemic circulation remains poorly understood. This knowledge gap is critically important to bridge for understanding the pathophysiology of CAA and accelerate development of targeted therapeutics. The authors of this review recently converged their diverse expertise in the field of perivascular physiology to specifically address this problem within the framework of a Leducq Foundation Transatlantic Network of Excellence on Brain Clearance. This review discusses the overarching goal of the consortium and explores the evidence supporting or refuting the role of impaired perivascular clearance in the pathophysiology of CAA with a focus on translating observations from rodents to humans. We also discuss the anatomical features of perivascular channels as well as the biophysical characteristics of fluid and solute transport.
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Affiliation(s)
- Susanne J van Veluw
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA.
| | - Helene Benveniste
- Department of Anesthesiology, Yale School of Medicine, New Haven, CT, USA
| | - Erik N T P Bakker
- Department of Biomedical Engineering, Amsterdam University Medical Center, Location AMC, Amsterdam Neuroscience Research Institute, Amsterdam, The Netherlands
| | - Roxana O Carare
- Clinical Neurosciences, University of Southampton, Southampton, UK
| | - Steven M Greenberg
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, Boston, MA, USA
| | - Jeffrey J Iliff
- VA Puget Sound Health Care System, University of Washington, Seattle, WA, USA
| | - Sylvie Lorthois
- Institut de Mécanique Des Fluides de Toulouse, IMFT, Université de Toulouse, CNRS, Toulouse, France
| | - William E Van Nostrand
- Department of Biomedical and Pharmaceutical Science, George & Anne Ryan Institute for Neuroscience, University of Rhode Island, Kingston, RI, USA
| | - Gabor C Petzold
- German Center for Neurodegenerative Disease, Bonn, Germany
- Division of Vascular Neurology, Department of Neurology, University Hospital Bonn, Bonn, Germany
| | - Andy Y Shih
- Center for Developmental Biology and Regenerative Medicine, Seattle Children's Research Institute, University of Washington, Seattle, WA, USA
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2
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Joshi K, Diaz A, O'Keeffe K, Schaffer JD, Chiarot PR, Huang P. Flow in temporally and spatially varying porous media: a model for transport of interstitial fluid in the brain. J Math Biol 2024; 88:69. [PMID: 38664246 DOI: 10.1007/s00285-024-02092-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/11/2023] [Revised: 02/02/2024] [Accepted: 04/02/2024] [Indexed: 05/12/2024]
Abstract
Flow in a porous medium can be driven by the deformations of the boundaries of the porous domain. Such boundary deformations locally change the volume fraction accessible by the fluid, creating non-uniform porosity and permeability throughout the medium. In this work, we construct a deformation-driven porous medium transport model with spatially and temporally varying porosity and permeability that are dependent on the boundary deformations imposed on the medium. We use this model to study the transport of interstitial fluid along the basement membranes in the arterial walls of the brain. The basement membrane is modeled as a deforming annular porous channel with the compressible pore space filled with an incompressible, Newtonian fluid. The role of a forward propagating peristaltic heart pulse wave and a reverse smooth muscle contraction wave on the flow within the basement membranes is investigated. Our results identify combinations of wave amplitudes that can induce either forward or reverse transport along these transport pathways in the brain. The magnitude and direction of fluid transport predicted by our model can help in understanding the clearance of fluids and solutes along the Intramural Periarterial Drainage route and the pathology of cerebral amyloid angiopathy.
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Affiliation(s)
- Ketaki Joshi
- Department of Mechanical Engineering, Watson College of Engineering and Applied Science, State University of New York at Binghamton, Binghamton, NY, 13902, USA
| | - Adrian Diaz
- Department of Mechanical Engineering, Watson College of Engineering and Applied Science, State University of New York at Binghamton, Binghamton, NY, 13902, USA
| | - Katherine O'Keeffe
- Department of Mechanical Engineering, Watson College of Engineering and Applied Science, State University of New York at Binghamton, Binghamton, NY, 13902, USA
| | - J David Schaffer
- Institute for Justice and Well-Being, State University of New York at Binghamton, Binghamton, NY, 13902, USA
| | - Paul R Chiarot
- Department of Mechanical Engineering, Watson College of Engineering and Applied Science, State University of New York at Binghamton, Binghamton, NY, 13902, USA
| | - Peter Huang
- Department of Mechanical Engineering, Watson College of Engineering and Applied Science, State University of New York at Binghamton, Binghamton, NY, 13902, USA.
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3
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Li H, Li B, Luo W, Qi X, Hao Y, Yang C, Li W, Li J, Hua Z, Guo T, Zheng Z, Yu X, Liu L, Zhao J, Li T, Huang D, Hu J, Li Z, Wang F, Li H, Ma C, Ji F. Regulation of interstitial fluid flow in adventitia along vasculature by heartbeat and respiration. iScience 2024; 27:109407. [PMID: 38532885 PMCID: PMC10963235 DOI: 10.1016/j.isci.2024.109407] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/06/2023] [Revised: 01/29/2024] [Accepted: 02/29/2024] [Indexed: 03/28/2024] Open
Abstract
Converging studies showed interstitial fluid (ISF) adjacent to blood vessels flows in adventitia along vasculature into heart and lungs. We aim to reveal circulatory pathways and regulatory mechanism of such adventitial ISF flow in rat model. By MRI, real-time fluorescent imaging, micro-CT, and histological analysis, ISF was found to flow in adventitial matrix surrounded by fascia and along systemic vessels into heart, then flow into lungs via pulmonary arteries and back to heart via pulmonary veins, which was neither perivascular tissues nor blood or lymphatic vessels. Under physiological conditions, speckle-like adventitial ISF flow rate was positively correlated with heart rate, increased when holding breath, became pulsative during heavy breathing. During cardiac or respiratory cycle, each dilation or contraction of heart or lungs can generate to-and-fro adventitial ISF flow along femoral veins. Discovered regulatory mechanisms of adventitial ISF flow along vasculature by heart and lungs will revolutionize understanding of cardiovascular system.
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Affiliation(s)
- Hongyi Li
- Research Center for Interstitial Fluid Circulation, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
- Department of Geriatrics, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - Bei Li
- Research Center for Interstitial Fluid Circulation, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - Wenqi Luo
- Department of Cardiac Surgery, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - Xi Qi
- Peking University Fifth School of Clinical Medicine, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - You Hao
- Institute of Computing Technology, Chinese Academy of Sciences, Beijing 100190, P.R. China
| | - Chaozhi Yang
- School of Computer Science and Technology, China University of Petroleum (East China), Qingdao 266580, P.R. China
| | - Wenqing Li
- Research Center for Interstitial Fluid Circulation, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - Jiazheng Li
- Department of Anesthesiology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - Zhen Hua
- Department of Anesthesiology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - Tan Guo
- Department of Radiology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - Zhijian Zheng
- Department of Acupuncture, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - Xue Yu
- Department of Cardiology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - Lei Liu
- Department of Pharmacy, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - Jianping Zhao
- Department of Cardiology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - Tiantian Li
- Department of Cardiology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - Dahai Huang
- Department of Geriatrics, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - Jun Hu
- Key Lab of Interfacial Physics and Technology, Shanghai Institute of Applied Physics, Chinese Academy of Sciences, Shanghai 201210, P.R. China
- Shanghai Synchrotron Radiation Facility, Shanghai Advanced Research Institute, Chinese Academy of Sciences, Shanghai 201210, P.R. China
| | - Zongmin Li
- School of Computer Science and Technology, China University of Petroleum (East China), Qingdao 266580, P.R. China
| | - Fang Wang
- Department of Cardiology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
| | - Hua Li
- Institute of Computing Technology, Chinese Academy of Sciences, Beijing 100190, P.R. China
| | - Chao Ma
- Institute of Basic Medical Sciences, Chinese Academy of Medical Sciences, Department of Human Anatomy, Histology and Embryology, School of Basic Medicine, Peking Union Medical College, Beijing 100005, P.R. China
- Chinese Institute for Brain Research, Beijing 100005, P.R. China
| | - Fusui Ji
- Department of Cardiology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, P.R. China
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4
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Das N, Dhamija R, Sarkar S. The role of astrocytes in the glymphatic network: a narrative review. Metab Brain Dis 2024; 39:453-465. [PMID: 38008886 DOI: 10.1007/s11011-023-01327-y] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 10/28/2023] [Accepted: 11/17/2023] [Indexed: 11/28/2023]
Abstract
To date, treatment of Central Nervous System (CNS) pathology has largely focused on neuronal structure and function. Yet, revived attention towards fluid circulation within the CNS has exposed the need to further explore the role of glial cells in maintaining homeostasis within neural networks. In the past decade, discovery of the neural glymphatic network has revolutionized traditional understanding of fluid dynamics within the CNS. Advancements in neuroimaging have revealed alternative pathways of cerebrospinal fluid (CSF) generation and efflux. Here, we discuss emerging perspectives on the role of astrocytes in CSF hydrodynamics, with particular focus on the contribution of aquaporin-4 channels to the glymphatic network. Astrocytic structural features and expression patterns are detailed in relation to their function in maintaining integrity of the Blood Brain Barrier (BBB) as part of the neurovascular unit (NVU). This narrative also highlights the potential role of glial dysfunction in pathogenesis of neurodegenerative disease, hydrocephalus, intracranial hemorrhage, ischemic stroke, and traumatic brain injury. The purpose of this literature summary is to provide an update on the changing landscape of scientific theory surrounding production, flow, and absorption of cerebrospinal fluid. The overarching aim of this narrative review is to advance the conception of basic, translational, and clinical research endeavors investigating glia as therapeutic targets for neurological disease.
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Affiliation(s)
- Nikita Das
- Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Ravi Dhamija
- Case Western Reserve University School of Medicine, Cleveland, OH, USA
| | - Sumit Sarkar
- Division of Neurotoxicology, HFT-132, National Center for Toxicological Research, U.S. Food & Drug Administration, Jefferson, AR, 72079, USA.
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5
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Rossinelli D, Fourestey G, Killer HE, Neutzner A, Iaccarino G, Remonda L, Berberat J. Large-scale in-silico analysis of CSF dynamics within the subarachnoid space of the optic nerve. Fluids Barriers CNS 2024; 21:20. [PMID: 38419077 PMCID: PMC10900650 DOI: 10.1186/s12987-024-00518-8] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2023] [Accepted: 01/29/2024] [Indexed: 03/02/2024] Open
Abstract
BACKGROUND Impaired cerebrospinal fluid (CSF) dynamics is involved in the pathophysiology of neurodegenerative diseases of the central nervous system and the optic nerve (ON), including Alzheimer's and Parkinson's disease, as well as frontotemporal dementia. The smallness and intricate architecture of the optic nerve subarachnoid space (ONSAS) hamper accurate measurements of CSF dynamics in this space, and effects of geometrical changes due to pathophysiological processes remain unclear. The aim of this study is to investigate CSF dynamics and its response to structural alterations of the ONSAS, from first principles, with supercomputers. METHODS Large-scale in-silico investigations were performed by means of computational fluid dynamics (CFD) analysis. High-order direct numerical simulations (DNS) have been carried out on ONSAS geometry at a resolution of 1.625 μm/pixel. Morphological changes on the ONSAS microstructure have been examined in relation to CSF pressure gradient (CSFPG) and wall strain rate, a quantitative proxy for mass transfer of solutes. RESULTS A physiological flow speed of 0.5 mm/s is achieved by imposing a hydrostatic pressure gradient of 0.37-0.67 Pa/mm across the ONSAS structure. At constant volumetric rate, the relationship between pressure gradient and CSF-accessible volume is well captured by an exponential curve. The ONSAS microstructure exhibits superior mass transfer compared to other geometrical shapes considered. An ONSAS featuring no microstructure displays a threefold smaller surface area, and a 17-fold decrease in mass transfer rate. Moreover, ONSAS trabeculae seem key players in mass transfer. CONCLUSIONS The present analysis suggests that a pressure drop of 0.1-0.2 mmHg over 4 cm is sufficient to steadily drive CSF through the entire subarachnoid space. Despite low hydraulic resistance, great heterogeneity in flow speeds puts certain areas of the ONSAS at risk of stagnation. Alterations of the ONSAS architecture aimed at mimicking pathological conditions highlight direct relationships between CSF volume and drainage capability. Compared to the morphological manipulations considered herein, the original ONSAS architecture seems optimized towards providing maximum mass transfer across a wide range of pressure gradients and volumetric rates, with emphasis on trabecular structures. This might shed light on pathophysiological processes leading to damage associated with insufficient CSF flow in patients with optic nerve compartment syndrome.
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Affiliation(s)
- Diego Rossinelli
- Institute for Computational and Mathematical Engineering (ICME), Center for Turbulence Research, Stanford University, Stanford, CA, 94305-3024, USA.
| | - Gilles Fourestey
- Scientific IT & Application Support (SCITAS), Swiss Federal Institute of Technology Lausanne (EPFL), Lausanne, Switzerland
| | | | - Albert Neutzner
- Department of Biomedicine, University of Basel, Basel, Switzerland
| | - Gianluca Iaccarino
- Institute for Computational and Mathematical Engineering (ICME), Center for Turbulence Research, Stanford University, Stanford, CA, 94305-3024, USA
| | - Luca Remonda
- Institute of Neuroradiology, Kantonsspital Aarau, 5000, Aarau, Switzerland
| | - Jatta Berberat
- Institute of Neuroradiology, Kantonsspital Aarau, 5000, Aarau, Switzerland
- Geriatric Psychiatry, Department of Psychiatry, University Hospitals of Geneva, University of Geneva, Geneva, Switzerland
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6
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Gjerde IG, Rognes ME, Sánchez AL. The directional flow generated by peristalsis in perivascular networks-Theoretical and numerical reduced-order descriptions. JOURNAL OF APPLIED PHYSICS 2023; 134:174701. [PMID: 37927848 PMCID: PMC10624506 DOI: 10.1063/5.0160334] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Received: 05/31/2023] [Accepted: 10/16/2023] [Indexed: 11/07/2023]
Abstract
Directional fluid flow in perivascular spaces surrounding cerebral arteries is hypothesized to play a key role in brain solute transport and clearance. While various drivers for a pulsatile flow, such as cardiac or respiratory pulsations, are well quantified, the question remains as to which mechanisms could induce a directional flow within physiological regimes. To address this question, we develop theoretical and numerical reduced-order models to quantify the directional (net) flow induceable by peristaltic pumping in periarterial networks. Each periarterial element is modeled as a slender annular space bounded internally by a circular tube supporting a periodic traveling (peristaltic) wave. Under reasonable assumptions of a small Reynolds number flow, small radii, and small-amplitude peristaltic waves, we use lubrication theory and regular perturbation methods to derive theoretical expressions for the directional net flow and pressure distribution in the perivascular network. The reduced model is used to derive closed-form analytical expressions for the net flow for simple network configurations of interest, including single elements, two elements in tandem, and a three element bifurcation, with results compared with numerical predictions. In particular, we provide a computable theoretical estimate of the net flow induced by peristaltic motion in perivascular networks as a function of physiological parameters, notably, wave length, frequency, amplitude, and perivascular dimensions. Quantifying the maximal net flow for specific physiological regimes, we find that vasomotion may induce net pial periarterial flow velocities on the order of a few to tens of μ m/s and that sleep-related changes in vasomotion pulsatility may drive a threefold flow increase.
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Affiliation(s)
- I. G. Gjerde
- Department of Numerical Analysis and Scientific Computing, Simula Research Laboratory, Kristian Augusts gate 23, Oslo 0164, Norway
| | - M. E. Rognes
- Department of Numerical Analysis and Scientific Computing, Simula Research Laboratory, Kristian Augusts gate 23, Oslo 0164, Norway
| | - A. L. Sánchez
- Department of Mechanical and Aerospace Engineering, University of California San Diego, La Jolla, San Diego, California 92093-0411, USA
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7
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Wyart C, Carbo-Tano M, Cantaut-Belarif Y, Orts-Del'Immagine A, Böhm UL. Cerebrospinal fluid-contacting neurons: multimodal cells with diverse roles in the CNS. Nat Rev Neurosci 2023; 24:540-556. [PMID: 37558908 DOI: 10.1038/s41583-023-00723-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 06/26/2023] [Indexed: 08/11/2023]
Abstract
The cerebrospinal fluid (CSF) is a complex solution that circulates around the CNS, and whose composition changes as a function of an animal's physiological state. Ciliated neurons that are bathed in the CSF - and thus referred to as CSF-contacting neurons (CSF-cNs) - are unusual polymodal interoceptive neurons. As chemoreceptors, CSF-cNs respond to variations in pH and osmolarity and to bacterial metabolites in the CSF. Their activation during infections of the CNS results in secretion of compounds to enhance host survival. As mechanosensory neurons, CSF-cNs operate together with an extracellular proteinaceous polymer known as the Reissner fibre to detect compression during spinal curvature. Once activated, CSF-cNs inhibit motor neurons, premotor excitatory neurons and command neurons to enhance movement speed and stabilize posture. At longer timescales, CSF-cNs instruct morphogenesis throughout life via the release of neuropeptides that act over long distances on skeletal muscle. Finally, recent evidence suggests that mouse CSF-cNs may act as neural stem cells in the spinal cord, inspiring new paths of investigation for repair after injury.
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Affiliation(s)
- Claire Wyart
- Institut du Cerveau (ICM), INSERM U1127, UMR CNRS 7225 Paris, Sorbonne Université, Paris, France.
| | - Martin Carbo-Tano
- Institut du Cerveau (ICM), INSERM U1127, UMR CNRS 7225 Paris, Sorbonne Université, Paris, France
| | - Yasmine Cantaut-Belarif
- Institut du Cerveau (ICM), INSERM U1127, UMR CNRS 7225 Paris, Sorbonne Université, Paris, France
| | | | - Urs L Böhm
- NeuroCure Cluster of Excellence, Charité Universitätsmedizin Berlin, Berlin, Germany
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8
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Gan Y, Holstein-Rønsbo S, Nedergaard M, Boster KAS, Thomas JH, Kelley DH. Perivascular pumping of cerebrospinal fluid in the brain with a valve mechanism. J R Soc Interface 2023; 20:20230288. [PMID: 37727070 PMCID: PMC10509587 DOI: 10.1098/rsif.2023.0288] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/17/2023] [Accepted: 08/30/2023] [Indexed: 09/21/2023] Open
Abstract
The flow of cerebrospinal fluid (CSF) along perivascular spaces (PVSs) is an important part of the brain's system for clearing metabolic waste. Experiments reveal that arterial motions from cardiac pulsations and functional hyperaemiadrive CSF in the same direction as the blood flow, but the mechanism producing this directionality is unclear. Astrocyte endfeet bound the PVSs of penetrating arteries, separating them from brain extracellular space (ECS) and potentially regulating flow between the two compartments. Here, we present two models, one based on the full equations of fluid dynamics and the other using lumped parameters, in which the astrocyte endfeet function as valves, regulating flow between the PVS and the ECS. In both models, cardiac pulsations drive a net CSF flow consistent with prior experimental observations. Functional hyperaemia, acting with cardiac pulsation, increases the net flow. We also find, in agreement with experiments, a reduced net flow during wakefulness, due to the known decrease in ECS permeability compared to the sleep state. We present in vivo imaging of penetrating arteries in mice, which we use to measure accurately the amplitude of their constrictions and dilations during both cardiac pulsation and functional hyperaemia, an important input for the models. Our models can be used to explore the effects of changes in other input parameters, such as those caused by ageing or disease, as better measurements of these parameters become available.
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Affiliation(s)
- Yiming Gan
- Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627, USA
| | | | - Maiken Nedergaard
- Center for Translational Neuromedicine, University of Copenhagen, Copenhagen, Denmark
- Center for Translational Neuromedicine and Department of Neuroscience, University of Rochester Medical Center, Rochester, NY 14627, USA
| | - Kimberly A. S. Boster
- Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627, USA
| | - John H. Thomas
- Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627, USA
| | - Douglas H. Kelley
- Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627, USA
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9
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Vinje V, Zapf B, Ringstad G, Eide PK, Rognes ME, Mardal KA. Human brain solute transport quantified by glymphatic MRI-informed biophysics during sleep and sleep deprivation. Fluids Barriers CNS 2023; 20:62. [PMID: 37596635 PMCID: PMC10439559 DOI: 10.1186/s12987-023-00459-8] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/15/2023] [Accepted: 07/21/2023] [Indexed: 08/20/2023] Open
Abstract
Whether you are reading, running or sleeping, your brain and its fluid environment continuously interacts to distribute nutrients and clear metabolic waste. Yet, the precise mechanisms for solute transport within the human brain have remained hard to quantify using imaging techniques alone. From multi-modal human brain MRI data sets in sleeping and sleep-deprived subjects, we identify and quantify CSF tracer transport parameters using forward and inverse subject-specific computational modelling. Our findings support the notion that extracellular diffusion alone is not sufficient as a brain-wide tracer transport mechanism. Instead, we show that human MRI observations align well with transport by either by an effective diffusion coefficent 3.5[Formula: see text] that of extracellular diffusion in combination with local clearance rates corresponding to a tracer half-life of up to 5 h, or by extracellular diffusion augmented by advection with brain-wide average flow speeds on the order of 1-9 [Formula: see text]m/min. Reduced advection fully explains reduced tracer clearance after sleep-deprivation, supporting the role of sleep and sleep deprivation on human brain clearance.
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Affiliation(s)
- Vegard Vinje
- Simula Research Laboratory, Kristian Augusts gate 23, 0164, Oslo, Norway
- Expert Analytics AS, Møllergata 8, 0179, Oslo, Norway
| | - Bastian Zapf
- Department of Mathematics, University of Oslo, Oslo, Norway
| | - Geir Ringstad
- Department of Radiology, Oslo University Hospital - Rikshospitalet, Oslo, Norway
- Department of Geriatrics and Internal Medicine, Sørlandet Hospital, Arendal, Norway
| | - Per Kristian Eide
- Department of Neurosurgery, Oslo University Hospital - Rikshospitalet, Oslo, Norway
| | - Marie E Rognes
- Simula Research Laboratory, Kristian Augusts gate 23, 0164, Oslo, Norway
| | - Kent-Andre Mardal
- Simula Research Laboratory, Kristian Augusts gate 23, 0164, Oslo, Norway.
- Department of Mathematics, University of Oslo, Oslo, Norway.
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10
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Mukherjee S, Mirzaee M, Tithof J. Quantifying the relationship between spreading depolarization and perivascular cerebrospinal fluid flow. Sci Rep 2023; 13:12405. [PMID: 37524734 PMCID: PMC10390554 DOI: 10.1038/s41598-023-38938-5] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/15/2023] [Accepted: 07/17/2023] [Indexed: 08/02/2023] Open
Abstract
Recent studies have linked spreading depolarization (SD, an electro-chemical wave in the brain following stroke, migraine, traumatic brain injury, and more) with increase in cerebrospinal fluid (CSF) flow through the perivascular spaces (PVSs, annular channels lining the brain vasculature). We develop a novel computational model that couples SD and CSF flow. We first use high order numerical simulations to solve a system of physiologically realistic reaction-diffusion equations which govern the spatiotemporal dynamics of ions in the extracellular and intracellular spaces of the brain cortex during SD. We then couple the SD wave with a 1D CSF flow model that captures the change in cross-sectional area, pressure, and volume flow rate through the PVSs. The coupling is modelled using an empirical relationship between the excess potassium ion concentration in the extracellular space following SD and the vessel radius. We find that the CSF volumetric flow rate depends intricately on the length and width of the PVS, as well as the vessel radius and the angle of incidence of the SD wave. We derive analytical expressions for pressure and volumetric flow rates of CSF through the PVS for a given SD wave and quantify CSF flow variations when two SD waves collide. Our numerical approach is very general and could be extended in the future to obtain novel, quantitative insights into how CSF flow in the brain couples with slow waves, functional hyperemia, seizures, or externally applied neural stimulations.
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Affiliation(s)
- Saikat Mukherjee
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA.
- Department of Mechanical Engineering, Iowa State University, Ames, IA, 50011, USA.
| | - Mahsa Mirzaee
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA
| | - Jeffrey Tithof
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, MN, 55455, USA
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11
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Voumvourakis KI, Sideri E, Papadimitropoulos GN, Tsantzali I, Hewlett P, Kitsos D, Stefanou M, Bonakis A, Giannopoulos S, Tsivgoulis G, Paraskevas GP. The Dynamic Relationship between the Glymphatic System, Aging, Memory, and Sleep. Biomedicines 2023; 11:2092. [PMID: 37626589 PMCID: PMC10452251 DOI: 10.3390/biomedicines11082092] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/22/2023] [Revised: 07/16/2023] [Accepted: 07/19/2023] [Indexed: 08/27/2023] Open
Abstract
The process of memory entails the activation of numerous neural networks and biochemical pathways throughout the brain. The phenomenon of memory decline in relation to aging has been the subject of extensive research for several decades. The correlation between the process of aging and memory is intricate and has various aspects to consider. Throughout the aging process, there are various alterations that take place within the brain and, as expected, affect other functions that have already been linked to memory and its function such as involving microcirculation and sleep. Recent studies provide an understanding of how these mechanisms may be interconnected through the relatively new concept of the glymphatic system. The glymphatic system is strongly correlated to sleep processes. Sleep helps the glymphatic system remove brain waste solutes. Astrocytes expand and contract to form channels for cerebrospinal fluid (CSF) to wash through the brain and eliminate waste. However, the details have not been totally elusive, but the discovery of what we call the glymphatic system enables us to connect many pieces of physiology to understand how such factors are interconnected and the interplay between them. Thus, the purpose of this review is to discuss how the glymphatic system, sleep, memory, and aging are interconnected through a network of complex mechanisms and dynamic interactions.
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Affiliation(s)
- Konstantinos I. Voumvourakis
- 2nd Department of Neurology, School of Medicine, “Attikon” General University Hospital, National and Kapodistrian University of Athens, 12462 Athens, Greece; (K.I.V.); (E.S.); (A.B.)
| | - Eleni Sideri
- 2nd Department of Neurology, School of Medicine, “Attikon” General University Hospital, National and Kapodistrian University of Athens, 12462 Athens, Greece; (K.I.V.); (E.S.); (A.B.)
- Applied Psychology Department, Llandaff Campus, Cardiff Metropolitan University, Western Avenue, Cardiff CF5 2YB, UK
| | - Georgios N. Papadimitropoulos
- 2nd Department of Neurology, School of Medicine, “Attikon” General University Hospital, National and Kapodistrian University of Athens, 12462 Athens, Greece; (K.I.V.); (E.S.); (A.B.)
| | - Ioanna Tsantzali
- 2nd Department of Neurology, School of Medicine, “Attikon” General University Hospital, National and Kapodistrian University of Athens, 12462 Athens, Greece; (K.I.V.); (E.S.); (A.B.)
| | - Paul Hewlett
- Applied Psychology Department, Llandaff Campus, Cardiff Metropolitan University, Western Avenue, Cardiff CF5 2YB, UK
| | - Dimitrios Kitsos
- 2nd Department of Neurology, School of Medicine, “Attikon” General University Hospital, National and Kapodistrian University of Athens, 12462 Athens, Greece; (K.I.V.); (E.S.); (A.B.)
| | - Marianna Stefanou
- 2nd Department of Neurology, School of Medicine, “Attikon” General University Hospital, National and Kapodistrian University of Athens, 12462 Athens, Greece; (K.I.V.); (E.S.); (A.B.)
| | - Anastasios Bonakis
- 2nd Department of Neurology, School of Medicine, “Attikon” General University Hospital, National and Kapodistrian University of Athens, 12462 Athens, Greece; (K.I.V.); (E.S.); (A.B.)
| | - Sotirios Giannopoulos
- 2nd Department of Neurology, School of Medicine, “Attikon” General University Hospital, National and Kapodistrian University of Athens, 12462 Athens, Greece; (K.I.V.); (E.S.); (A.B.)
| | - Georgios Tsivgoulis
- 2nd Department of Neurology, School of Medicine, “Attikon” General University Hospital, National and Kapodistrian University of Athens, 12462 Athens, Greece; (K.I.V.); (E.S.); (A.B.)
| | - George P. Paraskevas
- 2nd Department of Neurology, School of Medicine, “Attikon” General University Hospital, National and Kapodistrian University of Athens, 12462 Athens, Greece; (K.I.V.); (E.S.); (A.B.)
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Raicevic N, Forer JM, Ladrón-de-Guevara A, Du T, Nedergaard M, Kelley DH, Boster K. Sizes and shapes of perivascular spaces surrounding murine pial arteries. Fluids Barriers CNS 2023; 20:56. [PMID: 37461047 PMCID: PMC10351203 DOI: 10.1186/s12987-023-00454-z] [Citation(s) in RCA: 3] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/14/2023] [Accepted: 06/21/2023] [Indexed: 07/20/2023] Open
Abstract
BACKGROUND Flow of cerebrospinal fluid (CSF) through brain perivascular spaces (PVSs) is essential for the clearance of interstitial metabolic waste products whose accumulation and aggregation is a key mechanism of pathogenesis in many diseases. The PVS geometry has important implications for CSF flow as it affects CSF and solute transport rates. Thus, the size and shape of the perivascular spaces are essential parameters for models of CSF transport in the brain and require accurate quantification. METHODS We segmented two-photon images of pial (surface) PVSs and the adjacent arteries and characterized their sizes and shapes of cross sections from 14 PVS segments in 9 mice. Based on the analysis, we propose an idealized model that approximates the cross-sectional size and shape of pial PVSs, closely matching their area ratios and hydraulic resistances. RESULTS The ratio of PVS-to-vessel area varies widely across the cross sections analyzed. The hydraulic resistance per unit length of the PVS scales with the PVS cross-sectional area, and we found a power-law fit that predicts resistance as a function of the area. Three idealized geometric models were compared to PVSs imaged in vivo, and their accuracy in reproducing hydraulic resistances and PVS-to-vessel area ratios were evaluated. The area ratio was obtained across different cross sections, and we found that the distribution peaks for the original PVS and its closest idealized fit (polynomial fit) were 1.12 and 1.21, respectively. The peak of the hydraulic resistance distribution is [Formula: see text] Pa s/m[Formula: see text] and [Formula: see text] Pa s/m[Formula: see text] for the segmentation and its closest idealized fit, respectively. CONCLUSIONS PVS hydraulic resistance can be reasonably predicted as a function of the PVS area. The proposed polynomial-based fit most closely captures the shape of the PVS with respect to area ratio and hydraulic resistance. Idealized PVS shapes are convenient for modeling, which can be used to better understand how anatomical variations affect clearance and drug transport.
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Affiliation(s)
- Nikola Raicevic
- Department of Mechanical Engineering, University of Rochester, Rochester, USA
| | - Jarod M Forer
- Department of Mechanical Engineering, University of Rochester, Rochester, USA
| | - Antonio Ladrón-de-Guevara
- Center for Translational Neuromedicine and Department of Neuroscience, University of Rochester Medical Center, Rochester, USA
- Department of Biomedical Engineering, University of Rochester, Rochester, USA
| | - Ting Du
- Center for Translational Neuromedicine and Department of Neuroscience, University of Rochester Medical Center, Rochester, USA
- School of Pharmacy, China Medical University, Shenyang, Liaoning, China
| | - Maiken Nedergaard
- Center for Translational Neuromedicine and Department of Neuroscience, University of Rochester Medical Center, Rochester, USA
| | - Douglas H Kelley
- Department of Mechanical Engineering, University of Rochester, Rochester, USA
| | - Kimberly Boster
- Department of Mechanical Engineering, University of Rochester, Rochester, USA.
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13
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Sætra MJ, Ellingsrud AJ, Rognes ME. Neural activity induces strongly coupled electro-chemo-mechanical interactions and fluid flow in astrocyte networks and extracellular space-A computational study. PLoS Comput Biol 2023; 19:e1010996. [PMID: 37478153 PMCID: PMC10396022 DOI: 10.1371/journal.pcbi.1010996] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/03/2023] [Revised: 08/02/2023] [Accepted: 06/28/2023] [Indexed: 07/23/2023] Open
Abstract
The complex interplay between chemical, electrical, and mechanical factors is fundamental to the function and homeostasis of the brain, but the effect of electrochemical gradients on brain interstitial fluid flow, solute transport, and clearance remains poorly quantified. Here, via in-silico experiments based on biophysical modeling, we estimate water movement across astrocyte cell membranes, within astrocyte networks, and within the extracellular space (ECS) induced by neuronal activity, and quantify the relative role of different forces (osmotic, hydrostatic, and electrical) on transport and fluid flow under such conditions. We find that neuronal activity alone may induce intracellular fluid velocities in astrocyte networks of up to 14μm/min, and fluid velocities in the ECS of similar magnitude. These velocities are dominated by an osmotic contribution in the intracellular compartment; without it, the estimated fluid velocities drop by a factor of ×34-45. Further, the compartmental fluid flow has a pronounced effect on transport: advection accelerates ionic transport within astrocytic networks by a factor of ×1-5 compared to diffusion alone.
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Affiliation(s)
- Marte J. Sætra
- Department of Numerical Analysis and Scientific Computing, Simula Research Laboratory, Oslo, Norway
| | - Ada J. Ellingsrud
- Department of Numerical Analysis and Scientific Computing, Simula Research Laboratory, Oslo, Norway
| | - Marie E. Rognes
- Department of Numerical Analysis and Scientific Computing, Simula Research Laboratory, Oslo, Norway
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14
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Sharp MK. Pulsatile cerebral paraarterial flow by peristalsis, pressure and directional resistance. Fluids Barriers CNS 2023; 20:41. [PMID: 37291600 DOI: 10.1186/s12987-023-00445-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/17/2022] [Accepted: 05/21/2023] [Indexed: 06/10/2023] Open
Abstract
BACKGROUND A glymphatic system has been proposed that comprises flow that enters along cerebral paraarterial channels between the artery wall and the surrounding glial layer, continues through the parenchyma, and then exits along similar paravenous channels. The mechanism driving flow through this system is unclear. The pulsatile (oscillatory plus mean) flow measured in the space surrounding the middle cerebral artery (MCA) suggests that peristalsis created by intravascular blood pressure pulses is a candidate for the paraarterial flow in the subarachnoid spaces. However, peristalsis is ineffective in driving significant mean flow when the amplitude of channel wall motion is small, as has been observed in the MCA artery wall. In this paper, peristalsis in combination with two additional mechanisms, a longitudinal pressure gradient and directional flow resistance, is evaluated to match the measured MCA paraarterial oscillatory and mean flows. METHODS Two analytical models are used that simplify the paraarterial branched network to a long continuous channel with a traveling wave in order to maximize the potential effect of peristalsis on the mean flow. The two models have parallel-plate and annulus geometries, respectively, with and without an added longitudinal pressure gradient. The effect of directional flow resistors was also evaluated for the parallel-plate geometry. RESULTS For these models, the measured amplitude of arterial wall motion is too large to cause the small measured amplitude of oscillatory velocity, indicating that the outer wall must also move. At a combined motion matching the measured oscillatory velocity, peristalsis is incapable of driving enough mean flow. Directional flow resistance elements augment the mean flow, but not enough to provide a match. With a steady longitudinal pressure gradient, both oscillatory and mean flows can be matched to the measurements. CONCLUSIONS These results suggest that peristalsis drives the oscillatory flow in the subarachnoid paraarterial space, but is incapable of driving the mean flow. The effect of directional flow resistors is insufficient to produce a match, but a small longitudinal pressure gradient is capable of creating the mean flow. Additional experiments are needed to confirm whether the outer wall also moves, as well as to validate the pressure gradient.
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Affiliation(s)
- M Keith Sharp
- Department of Mechanical Engineering, University of Louisville, 200 Sackett Hall, Louisville, KY, 40292, USA.
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15
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Rey JA, Farid UM, Najjoum CM, Brown A, Magdoom KN, Mareci TH, Sarntinoranont M. Perivascular network segmentations derived from high-field MRI and their implications for perivascular and parenchymal mass transport in the rat brain. Sci Rep 2023; 13:9205. [PMID: 37280246 DOI: 10.1038/s41598-023-34850-0] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/31/2022] [Accepted: 05/09/2023] [Indexed: 06/08/2023] Open
Abstract
A custom segmentation workflow was applied to ex vivo high-field MR images of rat brains acquired following in vivo intraventricular contrast agent infusion to generate maps of the perivascular spaces (PVS). The resulting perivascular network segmentations enabled analysis of perivascular connections to the ventricles, parenchymal solute clearance, and dispersive solute transport within PVS. Numerous perivascular connections between the brain surface and the ventricles suggest the ventricles integrate into a PVS-mediated clearance system and raise the possibility of cerebrospinal fluid (CSF) return from the subarachnoid space to the ventricles via PVS. Assuming rapid solute exchange between the PVS and CSF spaces primarily by advection, the extensive perivascular network decreased the mean clearance distance from parenchyma to the nearest CSF compartment resulting in an over 21-fold reduction in the estimated diffusive clearance time scale, irrespective of solute diffusivity. This corresponds to an estimated diffusive clearance time scale under 10 min for amyloid-beta which suggests that the widespread distribution of PVS may render diffusion an effective parenchymal clearance mechanism. Additional analysis of oscillatory solute dispersion within PVS indicates that advection rather than dispersion is likely the primary transport mechanism for dissolved compounds greater than 66 kDa in the long (> 2 mm) perivascular segments identified here, although dispersion may be significant for smaller compounds in shorter perivascular segments.
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Affiliation(s)
- Julian A Rey
- Department of Mechanical and Aerospace Engineering, University of Florida, PO BOX 116250, Gainesville, FL, 32611, USA
| | - Uzair M Farid
- Department of Mechanical and Aerospace Engineering, University of Florida, PO BOX 116250, Gainesville, FL, 32611, USA
| | - Christopher M Najjoum
- Department of Mechanical and Aerospace Engineering, University of Florida, PO BOX 116250, Gainesville, FL, 32611, USA
| | - Alec Brown
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL, USA
| | - Kulam Najmudeen Magdoom
- Department of Mechanical and Aerospace Engineering, University of Florida, PO BOX 116250, Gainesville, FL, 32611, USA
| | - Thomas H Mareci
- Department of Biochemistry and Molecular Biology, University of Florida, Gainesville, FL, USA
| | - Malisa Sarntinoranont
- Department of Mechanical and Aerospace Engineering, University of Florida, PO BOX 116250, Gainesville, FL, 32611, USA.
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16
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Boster KAS, Cai S, Ladrón-de-Guevara A, Sun J, Zheng X, Du T, Thomas JH, Nedergaard M, Karniadakis GE, Kelley DH. Artificial intelligence velocimetry reveals in vivo flow rates, pressure gradients, and shear stresses in murine perivascular flows. Proc Natl Acad Sci U S A 2023; 120:e2217744120. [PMID: 36989300 PMCID: PMC10083563 DOI: 10.1073/pnas.2217744120] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/18/2022] [Accepted: 02/15/2023] [Indexed: 03/30/2023] Open
Abstract
Quantifying the flow of cerebrospinal fluid (CSF) is crucial for understanding brain waste clearance and nutrient delivery, as well as edema in pathological conditions such as stroke. However, existing in vivo techniques are limited to sparse velocity measurements in pial perivascular spaces (PVSs) or low-resolution measurements from brain-wide imaging. Additionally, volume flow rate, pressure, and shear stress variation in PVSs are essentially impossible to measure in vivo. Here, we show that artificial intelligence velocimetry (AIV) can integrate sparse velocity measurements with physics-informed neural networks to quantify CSF flow in PVSs. With AIV, we infer three-dimensional (3D), high-resolution velocity, pressure, and shear stress. Validation comes from training with 70% of PTV measurements and demonstrating close agreement with the remaining 30%. A sensitivity analysis on the AIV inputs shows that the uncertainty in AIV inferred quantities due to uncertainties in the PVS boundary locations inherent to in vivo imaging is less than 30%, and the uncertainty from the neural net initialization is less than 1%. In PVSs of N = 4 wild-type mice we find mean flow speed 16.33 ± 11.09 µm/s, volume flow rate 2.22 ± 1.983 × 103 µm3/s, axial pressure gradient ( - 2.75 ± 2.01)×10-4 Pa/µm (-2.07 ± 1.51 mmHg/m), and wall shear stress (3.00 ± 1.45)×10-3 Pa (all mean ± SE). Pressure gradients, flow rates, and resistances agree with prior predictions. AIV infers in vivo PVS flows in remarkable detail, which will improve fluid dynamic models and potentially clarify how CSF flow changes with aging, Alzheimer's disease, and small vessel disease.
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Affiliation(s)
| | - Shengze Cai
- Institute of Cyber-Systems and Control, College of Control Science and Engineering, Zhejiang University, Hangzhou310027, Zhejiang, China
| | - Antonio Ladrón-de-Guevara
- Center for Translational Neuromedicine and Department of Neuroscience, University of Rochester Medical Center, Rochester, NY14627
| | - Jiatong Sun
- Department of Mechanical Engineering, University of Rochester, Rochester, NY14627
| | - Xiaoning Zheng
- Department of Mathematics, College of Information Science and Technology, Jinan University, Guangzhou510632, China
| | - Ting Du
- Center for Translational Neuromedicine and Department of Neuroscience, University of Rochester Medical Center, Rochester, NY14627
- School of Pharmacy, China Medical University, Shenyang, Liaoning110122, China
| | - John H. Thomas
- Department of Mechanical Engineering, University of Rochester, Rochester, NY14627
| | - Maiken Nedergaard
- Center for Translational Neuromedicine and Department of Neuroscience, University of Rochester Medical Center, Rochester, NY14627
| | - George Em Karniadakis
- Division of Applied Mathematics, Brown University, Providence, RI02912
- School of Engineering, Brown University, Providence, RI02912
| | - Douglas H. Kelley
- Department of Mechanical Engineering, University of Rochester, Rochester, NY14627
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17
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Gholampour S, Balasundaram H, Thiyagarajan P, Droessler J. A mathematical framework for the dynamic interaction of pulsatile blood, brain, and cerebrospinal fluid. COMPUTER METHODS AND PROGRAMS IN BIOMEDICINE 2023; 231:107209. [PMID: 36796166 DOI: 10.1016/j.cmpb.2022.107209] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Subscribe] [Scholar Register] [Received: 08/22/2022] [Revised: 10/07/2022] [Accepted: 10/27/2022] [Indexed: 06/18/2023]
Abstract
BACKGROUND Shedding light on less-known aspects of intracranial fluid dynamics may be helpful to understand the hydrocephalus mechanism. The present study suggests a mathematical framework based on in vivo inputs to compare the dynamic interaction of pulsatile blood, brain, and cerebrospinal fluid (CSF) between the healthy subject and the hydrocephalus patient. METHOD The input data for the mathematical formulations was pulsatile blood velocity, which was measured using cine PC-MRI. Tube law was used to transfer the created deformation by blood pulsation in the vessel circumference to the brain domain. The pulsatile deformation of brain tissue with respect to time was calculated and considered to be inlet velocity in the CSF domain. The governing equations in all three domains were continuity, Navier-Stokes, and concentration. We used Darcy law with defined permeability and diffusivity values to define the material properties in the brain. RESULTS We validated the preciseness of the CSF velocity and pressure through the mathematical formulations with cine PC-MRI velocity, experimental ICP, and FSI simulated velocity and pressure. We used the analysis of dimensionless numbers including Reynolds, Womersley, Hartmann, and Peclet to evaluate the characteristics of the intracranial fluid flow. In the mid-systole phase of a cardiac cycle, CSF velocity had the maximum value and CSF pressure had the minimum value. The maximum and amplitude of CSF pressure, as well as CSF stroke volume, were calculated and compared between the healthy subject and the hydrocephalus patient. CONCLUSION The present in vivo-based mathematical framework has the potential to gain insight into the less-known points in the physiological function of intracranial fluid dynamics and the hydrocephalus mechanism.
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Affiliation(s)
- Seifollah Gholampour
- Department of Neurological Surgery, University of Chicago, 5841 S. Maryland Ave, Chicago, IL 60637, USA
| | - Hemalatha Balasundaram
- Department of Mathematics, Vels Institute of Science, Technology and Advanced Studies, Chennai, Tamilnadu, India
| | - Padmavathi Thiyagarajan
- Department of Mathematics, Vels Institute of Science, Technology and Advanced Studies, Chennai, Tamilnadu, India
| | - Julie Droessler
- Department of Neurological Surgery, University of Chicago, 5841 S. Maryland Ave, Chicago, IL 60637, USA
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18
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Williams SD, Setzer B, Fultz NE, Valdiviezo Z, Tacugue N, Diamandis Z, Lewis LD. Neural activity induced by sensory stimulation can drive large-scale cerebrospinal fluid flow during wakefulness in humans. PLoS Biol 2023; 21:e3002035. [PMID: 36996009 PMCID: PMC10062585 DOI: 10.1371/journal.pbio.3002035] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/08/2022] [Accepted: 02/15/2023] [Indexed: 03/31/2023] Open
Abstract
Cerebrospinal fluid (CSF) flow maintains healthy brain homeostasis, facilitating solute transport and the exchange of brain waste products. CSF flow is thus important for brain health, but the mechanisms that control its large-scale movement through the ventricles are not well understood. While it is well established that CSF flow is modulated by respiratory and cardiovascular dynamics, recent work has also demonstrated that neural activity is coupled to large waves of CSF flow in the ventricles during sleep. To test whether the temporal coupling between neural activity and CSF flow is in part due to a causal relationship, we investigated whether CSF flow could be induced by driving neural activity with intense visual stimulation. We manipulated neural activity with a flickering checkerboard visual stimulus and found that we could drive macroscopic CSF flow in the human brain. The timing and amplitude of CSF flow was matched to the visually evoked hemodynamic responses, suggesting neural activity can modulate CSF flow via neurovascular coupling. These results demonstrate that neural activity can contribute to driving CSF flow in the human brain and that the temporal dynamics of neurovascular coupling can explain this effect.
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Affiliation(s)
- Stephanie D. Williams
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America
- Department of Psychological and Brain Sciences, Boston University, Boston, Massachusetts, United States of America
| | - Beverly Setzer
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America
- Graduate Program in Neuroscience, Boston University, Boston, Massachusetts, United States of America
| | - Nina E. Fultz
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America
| | - Zenia Valdiviezo
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America
| | - Nicole Tacugue
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America
| | - Zachary Diamandis
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America
| | - Laura D. Lewis
- Department of Biomedical Engineering, Boston University, Boston, Massachusetts, United States of America
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19
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Turner KL, Gheres KW, Drew PJ. Relating Pupil Diameter and Blinking to Cortical Activity and Hemodynamics across Arousal States. J Neurosci 2023; 43:949-964. [PMID: 36517240 PMCID: PMC9908322 DOI: 10.1523/jneurosci.1244-22.2022] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/24/2022] [Revised: 12/06/2022] [Accepted: 12/09/2022] [Indexed: 12/23/2022] Open
Abstract
Arousal state affects neural activity and vascular dynamics in the cortex, with sleep associated with large changes in the local field potential and increases in cortical blood flow. We investigated the relationship between pupil diameter and blink rate with neural activity and blood volume in the somatosensory cortex in male and female unanesthetized, head-fixed mice. We monitored these variables while the mice were awake, during periods of rapid eye movement (REM), and non-rapid eye movement (NREM) sleep. Pupil diameter was smaller during sleep than in the awake state. Changes in pupil diameter were coherent with both gamma-band power and blood volume in the somatosensory cortex, but the strength and sign of this relationship varied with arousal state. We observed a strong negative correlation between pupil diameter and both gamma-band power and blood volume during periods of awake rest and NREM sleep, although the correlations between pupil diameter and these signals became positive during periods of alertness, active whisking, and REM. Blinking was associated with increases in arousal and decreases in blood volume when the mouse was asleep. Bilateral coherence in gamma-band power and in blood volume dropped following awake blinking, indicating a reset of neural and vascular activity. Using only eye metrics (pupil diameter and eye motion), we could determine the arousal state of the mouse ('Awake,' 'NREM,' 'REM') with >90% accuracy with a 5 s resolution. There is a strong relationship between pupil diameter and hemodynamics signals in mice, reflecting the pronounced effects of arousal on cerebrovascular dynamics.SIGNIFICANCE STATEMENT Determining arousal state is a critical component of any neuroscience experiment. Pupil diameter and blinking are influenced by arousal state, as are hemodynamics signals in the cortex. We investigated the relationship between cortical hemodynamics and pupil diameter and found that pupil diameter was strongly related to the blood volume in the cortex. Mice were more likely to be awake after blinking than before, and blinking resets neural activity. Pupil diameter and eye motion can be used as a reliable, noninvasive indicator of arousal state. As mice transition from wake to sleep and back again over a timescale of seconds, monitoring pupil diameter and eye motion permits the noninvasive detection of sleep events during behavioral or resting-state experiments.
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Affiliation(s)
- Kevin L Turner
- Department of Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802
- Center for Neural Engineering, Pennsylvania State University, University Park, Pennsylvania 16802
| | - Kyle W Gheres
- Center for Neural Engineering, Pennsylvania State University, University Park, Pennsylvania 16802
- Departments of Engineering Science and Mechanics
| | - Patrick J Drew
- Department of Biomedical Engineering, Pennsylvania State University, University Park, Pennsylvania 16802
- Center for Neural Engineering, Pennsylvania State University, University Park, Pennsylvania 16802
- Departments of Engineering Science and Mechanics
- Biology and Neurosurgery, Pennsylvania State University, University Park, Pennsylvania 16802
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20
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Semyachkina-Glushkovskaya OV, Postnov DE, Khorovodov AP, Navolokin NA, Kurthz JHG. Lymphatic Drainage System of the Brain: a New Player in Neuroscience. J EVOL BIOCHEM PHYS+ 2023. [DOI: 10.1134/s0022093023010015] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 03/16/2023]
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21
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Olovnikov AM. Planetary Metronome as a Regulator of Lifespan and Aging Rate: The Metronomic Hypothesis. BIOCHEMISTRY. BIOKHIMIIA 2022; 87:1640-1650. [PMID: 36717453 DOI: 10.1134/s0006297922120197] [Citation(s) in RCA: 5] [Impact Index Per Article: 2.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/15/2023]
Abstract
A metronomic mechanism for the duration control of ontogenetic cycle periods of an animal is proposed. The components of the proposed metronomic system include the ventricular system of the brain, planet Earth as a generator of metronomic signals, and temporal DNA (tDNA) as a substrate that is epigenetically marked to measure elapsed time of ontogenesis. The metronomic system generates repetitive signals in the form of hydrodynamic disturbances in the cerebrospinal fluid (CSF). The metronomic effect arises due to the superposition of two processes - the near-wall unidirectional flow of CSF and oscillations in the movement of the planet. Hydrodynamic impacts of the metronome are transformed into nerve impulses that initiate epigenetic modification of tDNA in neurons, changing the content of factors expressed by this DNA for innervated targets of the body. The duration of ontogenetic cycle periods, including duration of the adult life, depends on the rate of addition of epigenetic marks to tDNA. This rate depends mainly on the frequency of the metronomic signals used by each particular species. But epigenetic modifications can also be influenced by factors that modulate metabolism and the rate of chromatin modifications, such as a calorie-restricted diet.
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Affiliation(s)
- Alexey M Olovnikov
- Emanuel Institute of Biochemical Physics, Russian Academy of Sciences, Moscow, 119334, Russia.
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22
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Kong Y, Yu X, Peng G, Wang F, Yin Y. Interstitial Fluid Flows along Perivascular and Adventitial Clearances around Neurovascular Bundles. J Funct Biomater 2022; 13:jfb13040172. [PMID: 36278641 PMCID: PMC9624367 DOI: 10.3390/jfb13040172] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/06/2022] [Revised: 09/11/2022] [Accepted: 09/28/2022] [Indexed: 11/09/2022] Open
Abstract
This study reports new phenomena of the interstitial fluid (ISF) microflow along perivascular and adventitial clearances (PAC) around neurovascular bundles. The fluorescent tracing was used to observe the ISF flow along the PAC of neurovascular bundles in 8-10 week old BALB/c mice. The new results include: (1) the topologic structure of the PAC around the neurovascular bundles is revealed; (2) the heart-orientated ISF flow along the PAC is observed; (3) the double-belt ISF flow along the venous adventitial clearance of the PAC is recorded; (4) the waterfall-like ISF flow induced by the small branching vessel or torn fascia along the PAC is discovered. Based on the above new phenomena, this paper approached the following objectives: (1) the kinematic laws of the ISF flow along the PAC around neurovascular bundles are set up; (2) the applicability of the hypothesis on the PAC and its subspaces by numerical simulations are examined. The findings of this paper not only enriched the image of the ISF flow through the body but also explained the kernel structure of the ISF flow (i.e., the PAC). It helps to lay the foundation for the kinematics and dynamics of the ISF flow along the PAC around neurovascular bundles.
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Affiliation(s)
- Yiya Kong
- Department of Cardiology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, China
- Graduate School, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China
| | - Xiaobin Yu
- Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
| | - Gang Peng
- Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
| | - Fang Wang
- Department of Cardiology, Beijing Hospital, National Center of Gerontology, Institute of Geriatric Medicine, Chinese Academy of Medical Sciences, Beijing 100730, China
- Graduate School, Peking Union Medical College, Chinese Academy of Medical Sciences, Beijing 100730, China
- Correspondence: (F.W.); (Y.Y.)
| | - Yajun Yin
- Department of Engineering Mechanics, Tsinghua University, Beijing 100084, China
- Correspondence: (F.W.); (Y.Y.)
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Investigating molecular transport in the human brain from MRI with physics-informed neural networks. Sci Rep 2022; 12:15475. [PMID: 36104360 PMCID: PMC9474534 DOI: 10.1038/s41598-022-19157-w] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2022] [Accepted: 08/24/2022] [Indexed: 11/23/2022] Open
Abstract
In recent years, a plethora of methods combining neural networks and partial differential equations have been developed. A widely known example are physics-informed neural networks, which solve problems involving partial differential equations by training a neural network. We apply physics-informed neural networks and the finite element method to estimate the diffusion coefficient governing the long term spread of molecules in the human brain from magnetic resonance images. Synthetic testcases are created to demonstrate that the standard formulation of the physics-informed neural network faces challenges with noisy measurements in our application. Our numerical results demonstrate that the residual of the partial differential equation after training needs to be small for accurate parameter recovery. To achieve this, we tune the weights and the norms used in the loss function and use residual based adaptive refinement of training points. We find that the diffusion coefficient estimated from magnetic resonance images with physics-informed neural networks becomes consistent with results from a finite element based approach when the residuum after training becomes small. The observations presented here are an important first step towards solving inverse problems on cohorts of patients in a semi-automated fashion with physics-informed neural networks.
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Abstract
We review theoretical and numerical models of the glymphatic system, which circulates cerebrospinal fluid and interstitial fluid around the brain, facilitating solute transport. Models enable hypothesis development and predictions of transport, with clinical applications including drug delivery, stroke, cardiac arrest, and neurodegenerative disorders like Alzheimer’s disease. We sort existing models into broad categories by anatomical function: Perivascular flow, transport in brain parenchyma, interfaces to perivascular spaces, efflux routes, and links to neuronal activity. Needs and opportunities for future work are highlighted wherever possible; new models, expanded models, and novel experiments to inform models could all have tremendous value for advancing the field.
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25
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Yildiz S, Grinstead J, Hildebrand A, Oshinski J, Rooney WD, Lim MM, Oken B. Immediate impact of yogic breathing on pulsatile cerebrospinal fluid dynamics. Sci Rep 2022; 12:10894. [PMID: 35764793 PMCID: PMC9240010 DOI: 10.1038/s41598-022-15034-8] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/15/2022] [Accepted: 06/16/2022] [Indexed: 01/10/2023] Open
Abstract
Cerebrospinal fluid (CSF), a clear fluid bathing the central nervous system (CNS), undergoes pulsatile movements. Together with interstitial fluid, CSF plays a critical role for the removal of waste products from the brain, and maintenance of the CNS health. As such, understanding the mechanisms driving CSF movement is of high scientific and clinical impact. Since pulsatile CSF dynamics is sensitive and synchronous to respiratory movements, we are interested in identifying potential integrative therapies such as yogic breathing to regulate CSF dynamics, which has not been reported before. Here, we investigated the pre-intervention baseline data from our ongoing randomized controlled trial, and examined the impact of four yogic breathing patterns: (i) slow, (ii) deep abdominal, (iii) deep diaphragmatic, and (iv) deep chest breathing with the last three together forming a yogic breathing called three-part breath. We utilized our previously established non-invasive real-time phase contrast magnetic resonance imaging approach using a 3T MRI instrument, computed and tested differences in single voxel CSF velocities (instantaneous, respiratory, cardiac 1st and 2nd harmonics) at the level of foramen magnum during spontaneous versus yogic breathing. In examinations of 18 healthy participants (eight females, ten males; mean age 34.9 ± 14 (SD) years; age range: 18-61 years), we observed immediate increase in cranially-directed velocities of instantaneous-CSF 16-28% and respiratory-CSF 60-118% during four breathing patterns compared to spontaneous breathing, with the greatest changes during deep abdominal breathing (28%, p = 0.0008, and 118%, p = 0.0001, respectively). Cardiac pulsation was the primary source of pulsatile CSF motion except during deep abdominal breathing, when there was a comparable contribution of respiratory and cardiac 1st harmonic power [0.59 ± 0.78], suggesting respiration can be the primary regulator of CSF depending on the individual differences in breathing techniques. Further work is needed to investigate the impact of sustained training yogic breathing on pulsatile CSF dynamics for CNS health.
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Affiliation(s)
- Selda Yildiz
- Department of Neurology, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA.
| | - John Grinstead
- Siemens Medical Solutions USA, Inc, Portland, OR, 97239, USA
| | - Andrea Hildebrand
- Biostatistics and Design Program, Oregon Health & Science University, Portland, OR, 97239, USA
| | - John Oshinski
- Radiology & Imaging Sciences and Biomedical Engineering, Emory School of Medicine, Emory University, Atlanta, GA, 30322, USA
| | - William D Rooney
- Department of Neurology, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA
- Advanced Imaging Research Center, Oregon Health & Science University, Portland, OR, 97239, USA
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, 97239, USA
- Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR, 97239, USA
- Department of Biomedical Engineering, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Miranda M Lim
- Department of Neurology, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, 97239, USA
- VA Portland Health Care System, Portland, OR, 97239, USA
- Division of Pulmonary and Critical Care Medicine, Department of Medicine, Oregon Health & Science University, Portland, OR, 97239, USA
- Oregon Institute of Occupational Health Sciences, Oregon Health & Science University, Portland, OR, 97239, USA
| | - Barry Oken
- Department of Neurology, Oregon Health & Science University, 3181 SW Sam Jackson Park Road, Portland, OR, 97239, USA
- Department of Behavioral Neuroscience, Oregon Health & Science University, Portland, OR, 97239, USA
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Kedarasetti RT, Drew PJ, Costanzo F. Arterial vasodilation drives convective fluid flow in the brain: a poroelastic model. Fluids Barriers CNS 2022; 19:34. [PMID: 35570287 PMCID: PMC9107702 DOI: 10.1186/s12987-022-00326-y] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/01/2021] [Accepted: 03/29/2022] [Indexed: 01/26/2023] Open
Abstract
The movement of fluid into, through, and out of the brain plays an important role in clearing metabolic waste. However, there is controversy regarding the mechanisms driving fluid movement in the fluid-filled paravascular spaces (PVS), and whether the movement of metabolic waste in the brain extracellular space (ECS) is primarily driven by diffusion or convection. The dilation of penetrating arterioles in the brain in response to increases in neural activity (neurovascular coupling) is an attractive candidate for driving fluid circulation, as it drives deformation of the brain tissue and of the PVS around arteries, resulting in fluid movement. We simulated the effects of vasodilation on fluid movement into and out of the brain ECS using a novel poroelastic model of brain tissue. We found that arteriolar dilations could drive convective flow through the ECS radially outward from the arteriole, and that this flow is sensitive to the dynamics of the dilation. Simulations of sleep-like conditions, with larger vasodilations and increased extracellular volume in the brain showed enhanced movement of fluid from the PVS into the ECS. Our simulations suggest that both sensory-evoked and sleep-related arteriolar dilations can drive convective flow of cerebrospinal fluid not just in the PVS, but also into the ECS through the PVS around arterioles.
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Affiliation(s)
- Ravi Teja Kedarasetti
- grid.29857.310000 0001 2097 4281Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA USA ,grid.29857.310000 0001 2097 4281Center for Neural Engineering, Pennsylvania State University, University Park, PA USA
| | - Patrick J. Drew
- grid.29857.310000 0001 2097 4281Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA USA ,grid.29857.310000 0001 2097 4281Center for Neural Engineering, Pennsylvania State University, University Park, PA USA ,grid.29857.310000 0001 2097 4281Department of Biomedical Engineering, Pennsylvania State University, University Park, PA USA ,grid.29857.310000 0001 2097 4281Department of Neurosurgery, Pennsylvania State University, University Park, PA USA
| | - Francesco Costanzo
- grid.29857.310000 0001 2097 4281Department of Engineering Science and Mechanics, Pennsylvania State University, University Park, PA USA ,grid.29857.310000 0001 2097 4281Center for Neural Engineering, Pennsylvania State University, University Park, PA USA ,grid.29857.310000 0001 2097 4281Department of Biomedical Engineering, Pennsylvania State University, University Park, PA USA ,grid.29857.310000 0001 2097 4281Department of Mathematics, Pennsylvania State University, University Park, PA USA
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Abstract
The brain harbors a unique ability to, figuratively speaking, shift its gears. During wakefulness, the brain is geared fully toward processing information and behaving, while homeostatic functions predominate during sleep. The blood-brain barrier establishes a stable environment that is optimal for neuronal function, yet the barrier imposes a physiological problem; transcapillary filtration that forms extracellular fluid in other organs is reduced to a minimum in brain. Consequently, the brain depends on a special fluid [the cerebrospinal fluid (CSF)] that is flushed into brain along the unique perivascular spaces created by astrocytic vascular endfeet. We describe this pathway, coined the term glymphatic system, based on its dependency on astrocytic vascular endfeet and their adluminal expression of aquaporin-4 water channels facing toward CSF-filled perivascular spaces. Glymphatic clearance of potentially harmful metabolic or protein waste products, such as amyloid-β, is primarily active during sleep, when its physiological drivers, the cardiac cycle, respiration, and slow vasomotion, together efficiently propel CSF inflow along periarterial spaces. The brain's extracellular space contains an abundance of proteoglycans and hyaluronan, which provide a low-resistance hydraulic conduit that rapidly can expand and shrink during the sleep-wake cycle. We describe this unique fluid system of the brain, which meets the brain's requisites to maintain homeostasis similar to peripheral organs, considering the blood-brain-barrier and the paths for formation and egress of the CSF.
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Affiliation(s)
- Martin Kaag Rasmussen
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - Humberto Mestre
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, New York
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, New York
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28
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Perivascular pumping in the mouse brain: Improved boundary conditions reconcile theory, simulation, and experiment. J Theor Biol 2022; 542:111103. [PMID: 35339513 DOI: 10.1016/j.jtbi.2022.111103] [Citation(s) in RCA: 2] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/30/2021] [Revised: 02/16/2022] [Accepted: 03/17/2022] [Indexed: 01/24/2023]
Abstract
Cerebrospinal fluid (CSF) flows through the perivascular spaces (PVSs) surrounding cerebral arteries. Revealing the mechanisms driving that flow could bring improved understanding of brain waste transport and insights for disorders including Alzheimer's disease and stroke. In vivo velocity measurements of CSF in surface PVSs in mice have been used to argue that flow is driven primarily by the pulsatile motion of artery walls - perivascular pumping. However, fluid dynamics theory and simulation have predicted that perivascular pumping produces flows differing from in vivo observations starkly, particularly in the phase and relative amplitude of flow oscillation. We show that coupling theoretical and simulated flows to more realistic end boundary conditions, using resistance and compliance values measured in mice instead of using periodic boundaries, results in velocities that match observations more closely in phase and relative amplitude of oscillation, while preserving the existing agreement in mean flow speed. This quantitative agreement among theory, simulation, and in vivo measurement further supports the idea that perivascular pumping is an important CSF driver in physiological conditions.
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Zhang J, Zhao H, Xue Y, Liu Y, Fan G, Wang H, Dong Q, Cao W. Impaired Glymphatic Transport Kinetics Following Induced Acute Ischemic Brain Edema in a Mouse pMCAO Model. Front Neurol 2022; 13:860255. [PMID: 35370910 PMCID: PMC8970176 DOI: 10.3389/fneur.2022.860255] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/22/2022] [Accepted: 02/18/2022] [Indexed: 12/20/2022] Open
Abstract
Background Cerebral edema forms immediately after blood flow interruption in ischemic stroke, which largely increased the death and disability. The glymphatic (glial-lymphatic) pathway is a major regulator of the brain liquid dynamics and homeostasis. This study aimed to investigate the transport kinetics of the glymphatic system after the appearance of ischemic edema. Methods In this study, a coated filament was attached to the left middle cerebral artery (MCA) of mice to establish a mouse model of permanent middle cerebral artery occlusion with an intact blood-brain barrier (BBB). The glymphatic function was then quantified using contrast-enhanced MRI (11.7T) by employing an injection of gadobenate dimeglumine (BOPTA-Gd) into the cisterna magna of mice. We then evaluated the expression and polarization of aquaporin-4 (AQP4) as a proxy for the physiological state of the glymphatic system. Results Our results revealed a positive correlation between the signal intensity in T1-weighted images and the corresponding apparent diffusion coefficient (ADC) values in the cortex, striatum, and periventricular zone, suggesting that impaired glymphatic transport kinetics in these regions is correlated to the cytotoxic edema induced by the occlusion of MCA. Furthermore, the increased depolarization of AQP4 in the parenchyma perivascular space (PVS) was consistent with glymphatic failure following the induced early cerebral ischemic edema. Conclusions Glymphatic transport kinetics were suppressed between the onset of cytotoxic edema and the disruption of the BBB, which correlated with the diminishing ADC values that vary based on edema progression, and is associated with depolarization of AQP4 in the parenchyma PVSs.
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Affiliation(s)
- Jianying Zhang
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Hongchen Zhao
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Yang Xue
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Yiqi Liu
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - Guohang Fan
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
| | - He Wang
- The Key Laboratory of Computational Neuroscience and Brain-Inspired Intelligence, Institute of Science and Technology for Brain-Inspired Intelligence, Fudan University, Shanghai, China
- *Correspondence: He Wang
| | - Qiang Dong
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
- State Key Laboratory of Medical Neurobiology, Fudan University, Shanghai, China
- National Clinical Research Center for Aging and Medicine, Huashan Hospital, Fudan University, Shanghai, China
- Qiang Dong
| | - Wenjie Cao
- Department of Neurology, Huashan Hospital, Fudan University, Shanghai, China
- Wenjie Cao
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30
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Hladky SB, Barrand MA. The glymphatic hypothesis: the theory and the evidence. Fluids Barriers CNS 2022; 19:9. [PMID: 35115036 PMCID: PMC8815211 DOI: 10.1186/s12987-021-00282-z] [Citation(s) in RCA: 74] [Impact Index Per Article: 37.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/14/2021] [Accepted: 10/15/2021] [Indexed: 12/13/2022] Open
Abstract
The glymphatic hypothesis proposes a mechanism for extravascular transport into and out of the brain of hydrophilic solutes unable to cross the blood-brain barrier. It suggests that there is a circulation of fluid carrying solutes inwards via periarterial routes, through the interstitium and outwards via perivenous routes. This review critically analyses the evidence surrounding the mechanisms involved in each of these stages. There is good evidence that both influx and efflux of solutes occur along periarterial routes but no evidence that the principal route of outflow is perivenous. Furthermore, periarterial inflow of fluid is unlikely to be adequate to provide the outflow that would be needed to account for solute efflux. A tenet of the hypothesis is that flow sweeps solutes through the parenchyma. However, the velocity of any possible circulatory flow within the interstitium is too small compared to diffusion to provide effective solute movement. By comparison the earlier classical hypothesis describing extravascular transport proposed fluid entry into the parenchyma across the blood-brain barrier, solute movements within the parenchyma by diffusion, and solute efflux partly by diffusion near brain surfaces and partly carried by flow along "preferred routes" including perivascular spaces, white matter tracts and subependymal spaces. It did not suggest fluid entry via periarterial routes. Evidence is still incomplete concerning the routes and fate of solutes leaving the brain. A large proportion of the solutes eliminated from the parenchyma go to lymph nodes before reaching blood but the proportions delivered directly to lymph or indirectly via CSF which then enters lymph are as yet unclear. In addition, still not understood is why and how the absence of AQP4 which is normally highly expressed on glial endfeet lining periarterial and perivenous routes reduces rates of solute elimination from the parenchyma and of solute delivery to it from remote sites of injection. Neither the glymphatic hypothesis nor the earlier classical hypothesis adequately explain how solutes and fluid move into, through and out of the brain parenchyma. Features of a more complete description are discussed. All aspects of extravascular transport require further study.
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Affiliation(s)
- Stephen B. Hladky
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD UK
| | - Margery A. Barrand
- Department of Pharmacology, University of Cambridge, Cambridge, CB2 1PD UK
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31
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Wan J, Zhou S, Mea HJ, Guo Y, Ku H, Urbina BM. Emerging Roles of Microfluidics in Brain Research: From Cerebral Fluids Manipulation to Brain-on-a-Chip and Neuroelectronic Devices Engineering. Chem Rev 2022; 122:7142-7181. [PMID: 35080375 DOI: 10.1021/acs.chemrev.1c00480] [Citation(s) in RCA: 16] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 12/18/2022]
Abstract
Remarkable progress made in the past few decades in brain research enables the manipulation of neuronal activity in single neurons and neural circuits and thus allows the decipherment of relations between nervous systems and behavior. The discovery of glymphatic and lymphatic systems in the brain and the recently unveiled tight relations between the gastrointestinal (GI) tract and the central nervous system (CNS) further revolutionize our understanding of brain structures and functions. Fundamental questions about how neurons conduct two-way communications with the gut to establish the gut-brain axis (GBA) and interact with essential brain components such as glial cells and blood vessels to regulate cerebral blood flow (CBF) and cerebrospinal fluid (CSF) in health and disease, however, remain. Microfluidics with unparalleled advantages in the control of fluids at microscale has emerged recently as an effective approach to address these critical questions in brain research. The dynamics of cerebral fluids (i.e., blood and CSF) and novel in vitro brain-on-a-chip models and microfluidic-integrated multifunctional neuroelectronic devices, for example, have been investigated. This review starts with a critical discussion of the current understanding of several key topics in brain research such as neurovascular coupling (NVC), glymphatic pathway, and GBA and then interrogates a wide range of microfluidic-based approaches that have been developed or can be improved to advance our fundamental understanding of brain functions. Last, emerging technologies for structuring microfluidic devices and their implications and future directions in brain research are discussed.
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Affiliation(s)
- Jiandi Wan
- Department of Chemical Engineering, University of California, Davis, California 95616, United States
| | - Sitong Zhou
- Department of Chemical Engineering, University of California, Davis, California 95616, United States
| | - Hing Jii Mea
- Department of Chemical Engineering, University of California, Davis, California 95616, United States
| | - Yaojun Guo
- Department of Electrical and Computer Engineering, University of California, Davis, California 95616, United States
| | - Hansol Ku
- Department of Electrical and Computer Engineering, University of California, Davis, California 95616, United States
| | - Brianna M Urbina
- Biochemistry, Molecular, Cellular and Developmental Biology Program, University of California, Davis, California 95616, United States
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32
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Wichmann TO, Damkier HH, Pedersen M. A Brief Overview of the Cerebrospinal Fluid System and Its Implications for Brain and Spinal Cord Diseases. Front Hum Neurosci 2022; 15:737217. [PMID: 35126070 PMCID: PMC8813779 DOI: 10.3389/fnhum.2021.737217] [Citation(s) in RCA: 30] [Impact Index Per Article: 15.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/06/2021] [Accepted: 12/29/2021] [Indexed: 12/04/2022] Open
Abstract
A comprehensive understanding of the cerebrospinal fluid (CSF) system is essential for our understanding of health and disease within the central nervous system (CNS). The system of CSF refers to all components involved in CSF production, movement, and absorption. In recent years, extensive research has resulted in vastly improved understanding of the CSF system in health and disease. Yet, several aspects remain to be fully clarified, notably along the spinal cord as the preponderance of research has focused on the brain. This review briefly summarizes the CSF system and its implications for CNS diseases and highlights the knowledge gaps that require further research.
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Affiliation(s)
- Thea Overgaard Wichmann
- Department of Neurosurgery, Aarhus University Hospital, Aarhus, Denmark
- *Correspondence: Thea Overgaard Wichmann
| | | | - Michael Pedersen
- Comparative Medicine Lab, Department of Clinical Medicine, Faculty of Health, Aarhus University, Aarhus, Denmark
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Mehta NH, Sherbansky J, Kamer AR, Carare RO, Butler T, Rusinek H, Chiang GC, Li Y, Strauss S, Saint-Louis LA, Theise ND, Suss RA, Blennow K, Kaplitt M, de Leon MJ. The Brain-Nose Interface: A Potential Cerebrospinal Fluid Clearance Site in Humans. Front Physiol 2022; 12:769948. [PMID: 35058794 PMCID: PMC8764168 DOI: 10.3389/fphys.2021.769948] [Citation(s) in RCA: 14] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/13/2021] [Accepted: 11/26/2021] [Indexed: 12/17/2022] Open
Abstract
The human brain functions at the center of a network of systems aimed at providing a structural and immunological layer of protection. The cerebrospinal fluid (CSF) maintains a physiological homeostasis that is of paramount importance to proper neurological activity. CSF is largely produced in the choroid plexus where it is continuous with the brain extracellular fluid and circulates through the ventricles. CSF movement through the central nervous system has been extensively explored. Across numerous animal species, the involvement of various drainage pathways in CSF, including arachnoid granulations, cranial nerves, perivascular pathways, and meningeal lymphatics, has been studied. Among these, there is a proposed CSF clearance route spanning the olfactory nerve and exiting the brain at the cribriform plate and entering lymphatics. While this pathway has been demonstrated in multiple animal species, evidence of a similar CSF egress mechanism involving the nasal cavity in humans remains poorly consolidated. This review will synthesize contemporary evidence surrounding CSF clearance at the nose-brain interface, examining across species this anatomical pathway, and its possible significance to human neurodegenerative disease. Our discussion of a bidirectional nasal pathway includes examination of the immune surveillance in the olfactory region protecting the brain. Overall, we expect that an expanded discussion of the brain-nose pathway and interactions with the environment will contribute to an improved understanding of neurodegenerative and infectious diseases, and potentially to novel prevention and treatment considerations.
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Affiliation(s)
- Neel H. Mehta
- Undergraduate Department of Biology, Cornell University, Ithaca, NY, United States
| | | | - Angela R. Kamer
- Department of Periodontology and Implant Dentistry, NYU College of Dentistry, New York, NY, United States
| | - Roxana O. Carare
- Department of Medicine, University of Southampton, Southampton, United Kingdom
| | - Tracy Butler
- Department of Radiology, Brain Health Imaging Institute, Weill Cornell Medicine, New York, NY, United States
| | - Henry Rusinek
- Department of Radiology, NYU Langone Health, New York, NY, United States
| | - Gloria C. Chiang
- Department of Radiology, Weill Cornell Medicine, New York, NY, United States
| | - Yi Li
- Department of Radiology, Brain Health Imaging Institute, Weill Cornell Medicine, New York, NY, United States
| | - Sara Strauss
- Department of Radiology, Weill Cornell Medicine, New York, NY, United States
| | - L. A. Saint-Louis
- Department of Radiology, NYU Langone Health, New York, NY, United States
| | - Neil D. Theise
- Department of Pathology, NYU Grossman School of Medicine, New York, NY, United States
| | - Richard A. Suss
- Division of Neuroradiology, Department of Radiology, University of Texas Southwestern Medical Center, Dallas, TX, United States
| | - Kaj Blennow
- Clinical Neurochemistry Lab, Inst. of Neuroscience and Physiology, University of Gothenburg, Sahlgrenska University Hospital, Göteborg, Sweden
| | - Michael Kaplitt
- Laboratory of Molecular Neurosurgery, Department of Neurological Surgery, Weill Cornell Medical College, New York, NY, United States
| | - Mony J. de Leon
- Department of Radiology, Brain Health Imaging Institute, Weill Cornell Medicine, New York, NY, United States
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Szczygielski J, Kopańska M, Wysocka A, Oertel J. Cerebral Microcirculation, Perivascular Unit, and Glymphatic System: Role of Aquaporin-4 as the Gatekeeper for Water Homeostasis. Front Neurol 2021; 12:767470. [PMID: 34966347 PMCID: PMC8710539 DOI: 10.3389/fneur.2021.767470] [Citation(s) in RCA: 21] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/30/2021] [Accepted: 11/12/2021] [Indexed: 12/13/2022] Open
Abstract
In the past, water homeostasis of the brain was understood as a certain quantitative equilibrium of water content between intravascular, interstitial, and intracellular spaces governed mostly by hydrostatic effects i.e., strictly by physical laws. The recent achievements in molecular bioscience have led to substantial changes in this regard. Some new concepts elaborate the idea that all compartments involved in cerebral fluid homeostasis create a functional continuum with an active and precise regulation of fluid exchange between them rather than only serving as separate fluid receptacles with mere passive diffusion mechanisms, based on hydrostatic pressure. According to these concepts, aquaporin-4 (AQP4) plays the central role in cerebral fluid homeostasis, acting as a water channel protein. The AQP4 not only enables water permeability through the blood-brain barrier but also regulates water exchange between perivascular spaces and the rest of the glymphatic system, described as pan-cerebral fluid pathway interlacing macroscopic cerebrospinal fluid (CSF) spaces with the interstitial fluid of brain tissue. With regards to this, AQP4 makes water shift strongly dependent on active processes including changes in cerebral microcirculation and autoregulation of brain vessels capacity. In this paper, the role of the AQP4 as the gatekeeper, regulating the water exchange between intracellular space, glymphatic system (including the so-called neurovascular units), and intravascular compartment is reviewed. In addition, the new concepts of brain edema as a misbalance in water homeostasis are critically appraised based on the newly described role of AQP4 for fluid permeation. Finally, the relevance of these hypotheses for clinical conditions (including brain trauma and stroke) and for both new and old therapy concepts are analyzed.
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Affiliation(s)
- Jacek Szczygielski
- Department of Neurosurgery, Institute of Medical Sciences, University of Rzeszów, Rzeszów, Poland.,Department of Neurosurgery, Faculty of Medicine and Saarland University Medical Center, Saarland University, Homburg, Germany
| | - Marta Kopańska
- Department of Pathophysiology, Institute of Medical Sciences, University of Rzeszów, Rzeszów, Poland
| | - Anna Wysocka
- Chair of Internal Medicine and Department of Internal Medicine in Nursing, Faculty of Health Sciences, Medical University of Lublin, Lublin, Poland
| | - Joachim Oertel
- Department of Neurosurgery, Faculty of Medicine and Saarland University Medical Center, Saarland University, Homburg, Germany
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35
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Ray LA, Pike M, Simon M, Iliff JJ, Heys JJ. Quantitative analysis of macroscopic solute transport in the murine brain. Fluids Barriers CNS 2021; 18:55. [PMID: 34876169 PMCID: PMC8650464 DOI: 10.1186/s12987-021-00290-z] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2021] [Accepted: 11/21/2021] [Indexed: 12/16/2022] Open
Abstract
Background Understanding molecular transport in the brain is critical to care and prevention of neurological disease and injury. A key question is whether transport occurs primarily by diffusion, or also by convection or dispersion. Dynamic contrast-enhanced (DCE-MRI) experiments have long reported solute transport in the brain that appears to be faster than diffusion alone, but this transport rate has not been quantified to a physically relevant value that can be compared to known diffusive rates of tracers. Methods In this work, DCE-MRI experimental data is analyzed using subject-specific finite-element models to quantify transport in different anatomical regions across the whole mouse brain. The set of regional effective diffusivities (\documentclass[12pt]{minimal}
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\begin{document}$$D_{eff}$$\end{document}Deff), a transport parameter combining all mechanisms of transport, that best represent the experimental data are determined and compared to apparent diffusivity (\documentclass[12pt]{minimal}
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\begin{document}$$D_{app}$$\end{document}Dapp), the known rate of diffusion through brain tissue, to draw conclusions about dominant transport mechanisms in each region. Results In the perivascular regions of major arteries, \documentclass[12pt]{minimal}
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\begin{document}$$D_{eff}$$\end{document}Deff for gadoteridol (550 Da) was over 10,000 times greater than \documentclass[12pt]{minimal}
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\begin{document}$$D_{app}$$\end{document}Dapp. In the brain tissue, constituting interstitial space and the perivascular space of smaller blood vessels, \documentclass[12pt]{minimal}
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\begin{document}$$D_{eff}$$\end{document}Deff was 10–25 times greater than \documentclass[12pt]{minimal}
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\begin{document}$$D_{app}$$\end{document}Dapp. Conclusions The analysis concludes that convection is present throughout the brain. Convection is dominant in the perivascular space of major surface and branching arteries (Pe > 1000) and significant to large molecules (> 1 kDa) in the combined interstitial space and perivascular space of smaller vessels (not resolved by DCE-MRI). Importantly, this work supports perivascular convection along penetrating blood vessels. Supplementary Information The online version contains supplementary material available at 10.1186/s12987-021-00290-z.
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Affiliation(s)
- Lori A Ray
- Department of Chemical and Biological Engineering, Montana State University, Bozeman, USA
| | - Martin Pike
- Advanced Imaging Research Center, Oregon Health and Sciences University, Portland, USA
| | - Matthew Simon
- Department of Anesthesiology and Perioperative Medicine, Oregon Health and Science University, Portland, USA.,Neuroscience Graduate Program, Oregon Health and Science University, Portland, USA.,Denali Therapeutics, San Francisco, USA
| | - Jeffrey J Iliff
- VISN 20 Mental Illness Research, Education and Clinical Center (MIRECC), VA Puget Sound Health Care System, Seattle, USA.,Department of Psychiatry and Behavioral Sciences, University of Washington School of Medicine, Seattle, USA.,Department of Neurology, University of Washington School of Medicine, Seattle, USA
| | - Jeffrey J Heys
- Department of Chemical and Biological Engineering, Montana State University, Bozeman, USA.
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36
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Gama Sosa MA, De Gasperi R, Pryor D, Perez Garcia GS, Perez GM, Abutarboush R, Kawoos U, Hogg S, Ache B, Janssen WG, Sowa A, Tetreault T, Cook DG, Tappan SJ, Gandy S, Hof PR, Ahlers ST, Elder GA. Low-level blast exposure induces chronic vascular remodeling, perivascular astrocytic degeneration and vascular-associated neuroinflammation. Acta Neuropathol Commun 2021; 9:167. [PMID: 34654480 PMCID: PMC8518227 DOI: 10.1186/s40478-021-01269-5] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/25/2021] [Accepted: 09/29/2021] [Indexed: 02/08/2023] Open
Abstract
Cerebral vascular injury as a consequence of blast-induced traumatic brain injury is primarily the result of blast wave-induced mechanical disruptions within the neurovascular unit. In rodent models of blast-induced traumatic brain injury, chronic vascular degenerative processes are associated with the development of an age-dependent post-traumatic stress disorder-like phenotype. To investigate the evolution of blast-induced chronic vascular degenerative changes, Long-Evans rats were blast-exposed (3 × 74.5 kPa) and their brains analyzed at different times post-exposure by X-ray microcomputed tomography, immunohistochemistry and electron microscopy. On microcomputed tomography scans, regional cerebral vascular attenuation or occlusion was observed as early as 48 h post-blast, and cerebral vascular disorganization was visible at 6 weeks and more accentuated at 13 months post-blast. Progression of the late-onset pathology was characterized by detachment of the endothelial and smooth muscle cellular elements from the neuropil due to degeneration and loss of arteriolar perivascular astrocytes. Development of this pathology was associated with vascular remodeling and neuroinflammation as increased levels of matrix metalloproteinases (MMP-2 and MMP-9), collagen type IV loss, and microglial activation were observed in the affected vasculature. Blast-induced chronic alterations within the neurovascular unit should affect cerebral blood circulation, glymphatic flow and intramural periarterial drainage, all of which may contribute to development of the blast-induced behavioral phenotype. Our results also identify astrocytic degeneration as a potential target for the development of therapies to treat blast-induced brain injury.
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Affiliation(s)
- Miguel A Gama Sosa
- General Medical Research Service, James J. Peters Department of Veterans Affairs Medical Center, 130 West Kingsbridge Road, Bronx, NY, 10468, USA.
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA.
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA.
| | - Rita De Gasperi
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Research and Development Service, James J. Peters Department of Veterans Affairs Medical Center, 130 West Kingsbridge Road, Bronx, NY, 10468, USA
| | - Dylan Pryor
- Research and Development Service, James J. Peters Department of Veterans Affairs Medical Center, 130 West Kingsbridge Road, Bronx, NY, 10468, USA
| | - Georgina S Perez Garcia
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Research and Development Service, James J. Peters Department of Veterans Affairs Medical Center, 130 West Kingsbridge Road, Bronx, NY, 10468, USA
- Department of Neurology, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA
| | - Gissel M Perez
- Research and Development Service, James J. Peters Department of Veterans Affairs Medical Center, 130 West Kingsbridge Road, Bronx, NY, 10468, USA
| | - Rania Abutarboush
- Department of Neurotrauma, Operational and Undersea Medicine Directorate, Naval Medical Research Center, 503 Robert Grant Avenue, Silver Spring, MD, 20910, USA
- The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc, Bethesda, MD, USA
| | - Usmah Kawoos
- Department of Neurotrauma, Operational and Undersea Medicine Directorate, Naval Medical Research Center, 503 Robert Grant Avenue, Silver Spring, MD, 20910, USA
- The Henry M. Jackson Foundation for the Advancement of Military Medicine Inc, Bethesda, MD, USA
| | - Seth Hogg
- Micro Photonics, Inc, 1550 Pond Road, Suite 110, Allentown, PA, 18104, USA
| | - Benjamin Ache
- Micro Photonics, Inc, 1550 Pond Road, Suite 110, Allentown, PA, 18104, USA
| | - William G Janssen
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Allison Sowa
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | | | - David G Cook
- Geriatric Research Education and Clinical Center, VA Puget Sound Health Care System, 1660 S Columbian Way, Seattle, WA, 98108, USA
- Department of Medicine, University of Washington, 1959 NE Pacific St, Seattle, WA, 98195, USA
| | - Susan J Tappan
- MBF Bioscience LLC, 185 Allen Brook Lane, Williston, VT, 05495, USA
| | - Sam Gandy
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Research and Development Service, James J. Peters Department of Veterans Affairs Medical Center, 130 West Kingsbridge Road, Bronx, NY, 10468, USA
- Department of Neurology, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA
- Mount Sinai Alzheimer's Disease Research Center and the Ronald M. Loeb Center for Alzheimer's Disease, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- NFL Neurological Care Center, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Patrick R Hof
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Nash Family Department of Neuroscience, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Mount Sinai Alzheimer's Disease Research Center and the Ronald M. Loeb Center for Alzheimer's Disease, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Department of Geriatrics and Palliative Care, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
| | - Stephen T Ahlers
- Department of Neurotrauma, Operational and Undersea Medicine Directorate, Naval Medical Research Center, 503 Robert Grant Avenue, Silver Spring, MD, 20910, USA
| | - Gregory A Elder
- Department of Psychiatry, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA
- Friedman Brain Institute, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Department of Neurology, Icahn School of Medicine at Mount Sinai, One Gustave Levy Place, New York, NY, 10029, USA
- Mount Sinai Alzheimer's Disease Research Center and the Ronald M. Loeb Center for Alzheimer's Disease, Icahn School of Medicine at Mount Sinai, New York, NY, 10029, USA
- Neurology Service, James J. Peters Department of Veterans Affairs Medical Center, 130 West Kingsbridge Road, Bronx, NY, 10468, USA
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Li L, Li H, He Y, Tang H, Dong J, Chen X, Lyu F, Dong Y. Cyclic pulsation stress promotes bone formation of tissue engineered laminae through the F-actin/YAP-1/β-Catenin signaling axis. NPJ Regen Med 2021; 6:51. [PMID: 34489466 PMCID: PMC8421434 DOI: 10.1038/s41536-021-00164-w] [Citation(s) in RCA: 6] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 08/11/2021] [Indexed: 11/09/2022] Open
Abstract
Mechanical loads are fundamental regulators of bone formation and remodeling. However, the molecular regulation of mechanotransduction during vertebral laminae regeneration remains poorly understood. Here, we found that cerebrospinal fluid pulsation (CSFP) stress—cyclic pulsation stress—could promote the osteogenic and angiogenic abilities of rat mesenchymal stromal cells (MSC), thereby promoting tissue-engineered laminae’s bone and blood vessel formation. In the process, F-actin relayed CSFP stress to promote the nuclear translocation of YAP1, which then decreased the degradation and promoted the nuclear translocation of β-Catenin. In turn, the nuclear translocation of β-Catenin promoted the osteogenic differentiation and angiogenic abilities of MSC, thereby promoting tissue-engineered laminae’s bone and blood vessel formation. Thus, we conclude that CSFP promotes the osteogenesis and angiogenesis of tissue-engineered laminae through the F-actin/YAP-1/β-Catenin signaling axis. This study advances our understanding of vertebral laminae regeneration and provides potential therapeutic approaches for spinal degeneration after spinal laminectomy.
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Affiliation(s)
- Linli Li
- Department of Orthopedics, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
| | - Hailong Li
- Department of Orthopedics, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
| | - Yiqun He
- Department of Orthopedics, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
| | - Han Tang
- Department of Orthopedics, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
| | - Jian Dong
- Department of Orthopedics, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
| | - Xujun Chen
- Department of Orthopedics, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China
| | - Feizhou Lyu
- Department of Orthopedics, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China. .,Department of Orthopedics, Huashan Hospital, Fudan University, Shanghai, China.
| | - Youhai Dong
- Department of Orthopedics, Shanghai Fifth People's Hospital, Fudan University, Shanghai, China.
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38
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Brain solute transport is more rapid in periarterial than perivenous spaces. Sci Rep 2021; 11:16085. [PMID: 34373476 PMCID: PMC8352970 DOI: 10.1038/s41598-021-95306-x] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/29/2021] [Accepted: 07/23/2021] [Indexed: 11/13/2022] Open
Abstract
Fluid flow in perivascular spaces is recognized as a key component underlying brain transport and clearance. An important open question is how and to what extent differences in vessel type or geometry affect perivascular fluid flow and transport. Using computational modelling in both idealized and image-based geometries, we study and compare fluid flow and solute transport in pial (surface) periarterial and perivenous spaces. Our findings demonstrate that differences in geometry between arterial and venous pial perivascular spaces (PVSs) lead to higher net CSF flow, more rapid tracer transport and earlier arrival times of injected tracers in periarterial spaces compared to perivenous spaces. These findings can explain the experimentally observed rapid appearance of tracers around arteries, and the delayed appearance around veins without the need of a circulation through the parenchyma, but rather by direct transport along the PVSs.
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39
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Smith AJ, Akdemir G, Wadhwa M, Song D, Verkman AS. Application of fluorescent dextrans to the brain surface under constant pressure reveals AQP4-independent solute uptake. J Gen Physiol 2021; 153:212385. [PMID: 34128962 PMCID: PMC8210582 DOI: 10.1085/jgp.202112898] [Citation(s) in RCA: 11] [Impact Index Per Article: 3.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 02/11/2021] [Accepted: 05/11/2021] [Indexed: 12/26/2022] Open
Abstract
Extracellular solutes in the central nervous system are exchanged between the interstitial fluid, the perivascular compartment, and the cerebrospinal fluid (CSF). The "glymphatic" mechanism proposes that the astrocyte water channel aquaporin-4 (AQP4) is a major determinant of solute transport between the CSF and the interstitial space; however, this is controversial in part because of wide variance in experimental data on interstitial uptake of cisternally injected solutes. Here, we investigated the determinants of solute uptake in brain parenchyma following cisternal injection and reexamined the role of AQP4 using a novel constant-pressure method. In mice, increased cisternal injection rate, which modestly increased intracranial pressure, remarkably increased solute dispersion in the subarachnoid space and uptake in the cortical perivascular compartment. To investigate the role of AQP4 in the absence of confounding variations in pressure and CSF solute concentration over time and space, solutes were applied directly onto the brain surface after durotomy under constant external pressure. Pressure elevation increased solute penetration into the perivascular compartment but had little effect on parenchymal solute uptake. Solute penetration and uptake did not differ significantly between wild-type and AQP4 knockout mice. Our results offer an explanation for the variability in cisternal injection studies and indicate AQP4-independent solute transfer from the CSF to the interstitial space in mouse brain.
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Affiliation(s)
- Alex J Smith
- Department of Ophthalmology, University of California San Francisco, San Francisco, CA.,Departments of Medicine and Physiology, University of California San Francisco, San Francisco, CA
| | - Gokhan Akdemir
- Departments of Medicine and Physiology, University of California San Francisco, San Francisco, CA
| | - Meetu Wadhwa
- Department of Ophthalmology, University of California San Francisco, San Francisco, CA
| | - Dan Song
- Departments of Medicine and Physiology, University of California San Francisco, San Francisco, CA
| | - Alan S Verkman
- Departments of Medicine and Physiology, University of California San Francisco, San Francisco, CA
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40
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Martinac AD, Fletcher DF, Bilston LE. Phase offset between arterial pulsations and subarachnoid space pressure fluctuations are unlikely to drive periarterial cerebrospinal fluid flow. Biomech Model Mechanobiol 2021; 20:1751-1766. [PMID: 34275063 DOI: 10.1007/s10237-021-01474-0] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/11/2020] [Accepted: 06/02/2021] [Indexed: 11/24/2022]
Abstract
Circulation of fluid through the central nervous system maintains fluid homeostasis and is involved in solute clearance. The glymphatic system is hypothesised to facilitate waste clearance in the brain, with inflow via periarterial spaces, bulk flow through the parenchyma, and outflow via perivenous spaces. The driving force for this mechanism is unknown. Previous modelling in the spinal cord suggests that timing offsets between arterial and subarachnoid space pressure pulses can enable net inflow in perivascular spaces (PVS). This study adapted the spinal pulse offset mechanism to the brain and simulated movement of tracer particles used in experiments. Both bulk flow and diffusive movement of tracer were simulated. Intracranial pressure pulses were applied to one end of a 300-μm-long perivascular space combined with a moving arterial wall simulating arterial pulsations. The simulations indicate the pulse offset mechanism can enable net inflow via PVS; however, it is unknown whether the temporal offset required is physiologically realistic. Increasing the positive component of the ICP (intracranial pressure) pulse increased net flow. Tracer particles driven by bulk flow reached the outlet of the PVS with a net speed of ~ 16 μm/s when the permeability was two orders of magnitude higher than values in the literature. These particles were unable to penetrate into the parenchyma in the absence of diffusion. Dispersion dominated tracer movement in the parenchyma. Further research is required to reconcile discrepancies between these results, and both experimental and computational studies.
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Affiliation(s)
- Adam D Martinac
- Neuroscience Research Australia and Prince of Wales Clinical School, UNSW, Kensington, Australia.
| | - David F Fletcher
- School of Chemical and Biomolecular Engineering, The University of Sydney, Camperdown, Australia
| | - Lynne E Bilston
- Neuroscience Research Australia and Prince of Wales Clinical School, UNSW, Kensington, Australia
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Miyazaki Y, Usawa M, Kawai S, Yee J, Muto M, Tagawa Y. Dynamic mechanical interaction between injection liquid and human tissue simulant induced by needle-free injection of a highly focused microjet. Sci Rep 2021; 11:14544. [PMID: 34267280 PMCID: PMC8282861 DOI: 10.1038/s41598-021-94018-6] [Citation(s) in RCA: 5] [Impact Index Per Article: 1.7] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/24/2021] [Accepted: 07/01/2021] [Indexed: 12/15/2022] Open
Abstract
This study investigated the fluid-tissue interaction of needle-free injection by evaluating the dynamics of the cavity induced in body-tissue simulant and the resulting unsteady mechanical stress field. Temporal evolution of cavity shape, stress intensity field, and stress vector field during the injection of a conventional injection needle, a proposed highly focused microjet (tip diameter much smaller than capillary nozzle), and a typical non-focused microjet in gelatin were measured using a state-of-the-art high-speed polarization camera, at a frame rate up to 25,000 f.p.s. During the needle injection performed by an experienced nurse, high stress intensity lasted for an order of seconds (from beginning of needle penetration until end of withdrawal), which is much longer than the order of milliseconds during needle-free injections, causing more damage to the body tissue. The cavity induced by focused microjet resembled a funnel which had a narrow tip that penetrated deep into tissue simulant, exerting shear stress in low intensity which diffused through shear stress wave. Whereas the cavity induced by non-focused microjet rebounded elastically (quickly expanded into a sphere and shrank into a small cavity which remained), exerting compressive stress on tissue simulant in high stress intensity. By comparing the distribution of stress intensity, tip shape of the focused microjet contributed to a better performance than non-focused microjet with its ability to penetrate deep while only inducing stress at lower intensity. Dynamic mechanical interaction revealed in this research uncovered the importance of the jet shape for the development of minimally invasive medical devices.
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Affiliation(s)
- Yuta Miyazaki
- Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Japan
| | - Masashi Usawa
- Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Japan
| | - Shuma Kawai
- Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Japan
| | - Jingzu Yee
- Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Japan
| | - Masakazu Muto
- Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Japan
| | - Yoshiyuki Tagawa
- Department of Mechanical Systems Engineering, Tokyo University of Agriculture and Technology, Koganei, Japan.
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Abstract
Cerebrospinal fluid flows around and into the brain, driven by intricate mechanisms, with profound implications for human health. According to the glymphatic hypothesis, in physiological conditions, cerebrospinal fluid flows primarily during sleep and serves to remove metabolic wastes like the amyloid-beta and tau proteins whose accumulation is believed to cause Alzheimer's disease. This paper reviews one research team's recent in vivo experiments and theoretical studies to better understand the fluid dynamics of brain cerebrospinal fluid flow. Driving mechanisms are considered, particularly arterial pulsation. Flow correlates closely with artery motion and changes when artery motion is manipulated. Though there are discrepancies between in vivo observations and predictions from simulations and theoretical studies of the mechanism, realistic boundary conditions bring closer agreement. Vessel shapes are considered, and have elongation that minimizes their hydraulic resistance, perhaps through evolutionary optimization. The pathological condition of stroke is considered. Much tissue damage after stroke is caused by swelling, and there is now strong evidence that early swelling is caused not by fluid from blood, as is commonly thought, but by cerebrospinal fluid. Finally, drug delivery is considered, and demonstrations show the glymphatic system could quickly deliver drugs across the blood-brain barrier. The paper closes with a discussion of future opportunities in the fast-changing field of brain fluid dynamics.
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Affiliation(s)
- Douglas H. Kelley
- Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627, USA
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43
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Carr JB, Thomas JH, Liu J, Shang JK. Peristaltic pumping in thin non-axisymmetric annular tubes. JOURNAL OF FLUID MECHANICS 2021; 917:A10. [PMID: 35310826 PMCID: PMC8932954 DOI: 10.1017/jfm.2021.277] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 05/05/2023]
Abstract
The two-dimensional laminar flow of a viscous fluid induced by peristalsis due to a moving wall wave has been studied previously for a rectangular channel, a circular tube and a concentric circular annulus. Here, we study peristaltic flow in a non-axisymmetric annular tube: in this case, the flow is three-dimensional, with motions in the azimuthal direction. This type of geometry is motivated by experimental observations of the pulsatile flow of cerebrospinal fluid along perivascular spaces surrounding arteries in the brain, which is at least partially driven by peristaltic pumping due to pulsations of the artery. These annular perivascular spaces are often eccentric and the outer boundary is seldom circular: their cross-sections can be well matched by a simple, adjustable model consisting of an inner circle (the outer wall of the artery) and an outer ellipse (the outer edge of the perivascular space), not necessarily concentric. We use this geometric model as a basis for numerical simulations of peristaltic flow: the adjustability of the model makes it suitable for other applications. We concentrate on the general effects of the non-axisymmetric configuration on the flow and do not attempt to specifically model perivascular pumping. We use a finite-element scheme to compute the flow in the annulus driven by a propagating sinusoidal radial displacement of the inner wall. Unlike the peristaltic flow in a concentric circular annulus, the flow is fully three-dimensional: azimuthal pressure variations drive an oscillatory flow in and out of the narrower gaps, inducing an azimuthal wiggle in the streamlines. We examine the dependence of the flow on the elongation of the outer elliptical wall and the eccentricity of the configuration. We find that the time-averaged volumetric flow is always in the same direction as the peristaltic wave and decreases with increasing ellipticity or eccentricity. The additional shearing motion in the azimuthal direction will increase mixing and enhance Taylor dispersion in these flows, effects that might have practical applications.
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Affiliation(s)
- J. Brennen Carr
- Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627, USA
- correspondence:
| | - John H. Thomas
- Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627, USA
| | - Jia Liu
- Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627, USA
| | - Jessica K. Shang
- Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627, USA
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Yokoyama N, Takeishi N, Wada S. Cerebrospinal fluid flow driven by arterial pulsations in axisymmetric perivascular spaces: Analogy with Taylor's swimming sheet. J Theor Biol 2021; 523:110709. [PMID: 33862088 DOI: 10.1016/j.jtbi.2021.110709] [Citation(s) in RCA: 4] [Impact Index Per Article: 1.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/03/2020] [Revised: 03/19/2021] [Accepted: 03/31/2021] [Indexed: 11/30/2022]
Abstract
Cerebrospinal fluid (CSF) flow in the perivascular space (PVS), which surrounds the arteries in the brain, is of paramount importance in the removal of metabolic waste. Despite a number of experimental and numerical studies regarding CSF flow, the underlying mechanics of CSF flow are still debated, especially regarding whether an arterial pulsation can indeed produce net CSF flow velocity. Furthermore, the relationship between CSF flow and arterial wall pulsation has not been fully defined. To clarify these questions, we numerically investigated the CSF flow in the PVS in an axisymmetric channel with a pulsating boundary, where CSF is modeled as an incompressible, Newtonian viscous fluid in non-porous space. Our numerical results show that the net CSF flow velocity driven by the arterial pulsation is consistent with that of previous animal experiments. However, the peak oscillatory velocity is two orders of magnitude larger than the net velocity. Interestingly, the net CSF flow velocity collapses on the analytical solution derived from the lubrication theory in analogy with Taylor's swimming sheet model.
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Affiliation(s)
- Naoto Yokoyama
- Department of Mechanical Engineering, Tokyo Denki University, 5 Senju-Asahi, Adachi, Tokyo 120-8551, Japan.
| | - Naoki Takeishi
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama Toyonaka, Osaka 560-8531, Japan
| | - Shigeo Wada
- Graduate School of Engineering Science, Osaka University, 1-3 Machikaneyama Toyonaka, Osaka 560-8531, Japan
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45
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Sabayan B, Westendorp RGJ. Neurovascular-glymphatic dysfunction and white matter lesions. GeroScience 2021; 43:1635-1642. [PMID: 33851307 DOI: 10.1007/s11357-021-00361-x] [Citation(s) in RCA: 9] [Impact Index Per Article: 3.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/03/2021] [Accepted: 03/22/2021] [Indexed: 01/09/2023] Open
Abstract
Cerebral white matter lesions (WML) represent a spectrum of age-related structural changes that are identified as areas of white matter high signal intensity on brain magnetic resonance imaging (MRI). Preservation of white matter requires proper functioning of both the cerebrovascular and glymphatic systems. The cerebrovascular safeguards adequate cerebral blood flow to supply oxygen, energy, and nutrients through a dynamic process of cerebral autoregulation and neurovascular coupling to keep up with global and regional demands of the brain. The glymphatic system maintains white matter integrity by preserving flow of interstitial fluid, exchanging metabolic waste and eventually its clearance into the venous circulation. Here, we argue that these two systems should not be considered separate entities but as one single physiologically integrated unit to preserve brain health. Due to the process of aging, damage to the neurovascular-glymphatic system accumulates over the life course. It is an insidious process that ultimately leads to the disruption of cerebral autoregulation, to the neurovascular uncoupling, and to the accumulation of metabolic waste products. As cerebral white matter is particularly vulnerable to hypoxic, inflammatory, and metabolic insults, WML are the first recognized pathologies of neurovascular-glymphatic dysfunction. A better understanding of the underlying pathophysiology will provide starting points for developing effective strategies to prevent a wide range of clinical disorders among which there are gait disturbances, functional dependence, cognitive impairment, and dementia.
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Affiliation(s)
- Behnam Sabayan
- Department of Neurology, Massachusetts General Hospital, Harvard Medical School, 55 Fruit Street, Wang ACC 739B, Boston, MA, 02114, USA.
| | - Rudi G J Westendorp
- Department of Public Health and Center for Healthy Aging, University of Copenhagen, Copenhagen, Denmark
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46
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Raghunandan A, Ladron-de-Guevara A, Tithof J, Mestre H, Du T, Nedergaard M, Thomas JH, Kelley DH. Bulk flow of cerebrospinal fluid observed in periarterial spaces is not an artifact of injection. eLife 2021; 10:65958. [PMID: 33687330 PMCID: PMC7979157 DOI: 10.7554/elife.65958] [Citation(s) in RCA: 35] [Impact Index Per Article: 11.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/20/2020] [Accepted: 03/08/2021] [Indexed: 12/24/2022] Open
Abstract
Cerebrospinal fluid (CSF) flowing through periarterial spaces is integral to the brain’s mechanism for clearing metabolic waste products. Experiments that track tracer particles injected into the cisterna magna (CM) of mouse brains have shown evidence of pulsatile CSF flow in perivascular spaces surrounding pial arteries, with a bulk flow in the same direction as blood flow. However, the driving mechanism remains elusive. Several studies have suggested that the bulk flow might be an artifact, driven by the injection itself. Here, we address this hypothesis with new in vivo experiments where tracer particles are injected into the CM using a dual-syringe system, with simultaneous injection and withdrawal of equal amounts of fluid. This method produces no net increase in CSF volume and no significant increase in intracranial pressure. Yet, particle-tracking reveals flows that are consistent in all respects with the flows observed in earlier experiments with single-syringe injection.
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Affiliation(s)
- Aditya Raghunandan
- Department of Mechanical Engineering, University of Rochester, Rochester, United States
| | - Antonio Ladron-de-Guevara
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, United States
| | - Jeffrey Tithof
- Department of Mechanical Engineering, University of Rochester, Rochester, United States.,Department of Mechanical Engineering, University of Minnesota, Minneapolis, United States
| | - Humberto Mestre
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, United States
| | - Ting Du
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, United States
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, United States.,Center for Translational Neuromedicine, University of Copenhagen, Rochester, United States
| | - John H Thomas
- Department of Mechanical Engineering, University of Rochester, Rochester, United States
| | - Douglas H Kelley
- Department of Mechanical Engineering, University of Rochester, Rochester, United States
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47
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Attarpour A, Ward J, Chen JJ. Vascular origins of low-frequency oscillations in the cerebrospinal fluid signal in resting-state fMRI: Interpretation using photoplethysmography. Hum Brain Mapp 2021; 42:2606-2622. [PMID: 33638224 PMCID: PMC8090775 DOI: 10.1002/hbm.25392] [Citation(s) in RCA: 13] [Impact Index Per Article: 4.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/07/2020] [Revised: 02/09/2021] [Accepted: 02/16/2021] [Indexed: 12/12/2022] Open
Abstract
In vivo mapping of cerebrovascular oscillations in the 0.05–0.15 Hz remains difficult. Oscillations in the cerebrospinal fluid (CSF) represent a possible avenue for noninvasively tracking these oscillations using resting‐state functional MRI (rs‐fMRI), and have been used to correct for vascular oscillations in rs‐fMRI functional connectivity. However, the relationship between low‐frequency CSF and vascular oscillations remains unclear. In this study, we investigate this relationship using fast simultaneous rs‐fMRI and photoplethysmogram (PPG), examining the 0.1 Hz PPG signal, heart‐rate variability (HRV), pulse‐intensity ratio (PIR), and the second derivative of the PPG (SDPPG). The main findings of this study are: (a) signals in different CSF regions are not equivalent in their associations with vascular and tissue rs‐fMRI signals; (b) the PPG signal is maximally coherent with the arterial and CSF signals at the cardiac frequency, but coherent with brain tissue at ~0.2 Hz; (c) PIR is maximally coherent with the CSF signal near 0.03 Hz; and (d) PPG‐related vascular oscillations only contribute to ~15% of the CSF (and arterial) signal in rs‐fMRI. These findings caution against averaging all CSF regions when extracting physiological nuisance regressors in rs‐fMRI applications, and indicate the drivers of the CSF signal are more than simply cardiac. Our study is an initial attempt at the refinement and standardization of how the CSF signal in rs‐fMRI can be used and interpreted. It also paves the way for using rs‐fMRI in the CSF as a potential tool for tracking cerebrovascular health through, for instance, the potential relationship between PIR and the CSF signal.
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Affiliation(s)
- Ahmadreza Attarpour
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada
| | - James Ward
- Rotman Research Institute, Baycrest Health Sciences, Toronto, Ontario, Canada
| | - J Jean Chen
- Department of Medical Biophysics, University of Toronto, Toronto, Ontario, Canada.,Rotman Research Institute, Baycrest Health Sciences, Toronto, Ontario, Canada
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48
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Troyetsky DE, Tithof J, Thomas JH, Kelley DH. Dispersion as a waste-clearance mechanism in flow through penetrating perivascular spaces in the brain. Sci Rep 2021; 11:4595. [PMID: 33633194 PMCID: PMC7907360 DOI: 10.1038/s41598-021-83951-1] [Citation(s) in RCA: 14] [Impact Index Per Article: 4.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/30/2020] [Accepted: 02/10/2021] [Indexed: 01/31/2023] Open
Abstract
Accumulation of metabolic wastes in the brain is correlated with several neurodegenerative disorders, including Alzheimer's disease. Waste transport and clearance occur via dispersion, the combined effect of diffusion and advection by flow of fluid. We examine the relative contributions of diffusion and advection in the perivascular spaces (PVSs) that surround penetrating cortical blood vessels and are filled with cerebrospinal fluid (CSF). To do so, we adapt prior analytic predictions of dispersion to the context of PVSs. We also perform advection-diffusion simulations in PVS-like geometries with parameters relevant to transport of amyloid-[Formula: see text] (associated with Alzheimer's) in a variety of flows, motivated by in vivo measurements. Specifically, we examine solute transport in steady and unsteady Poiseuille flows in an open (not porous) concentric circular annulus. We find that a purely oscillatory flow enhances dispersion only weakly and does not produce significant transport, whereas a steady flow component, even if slow, clears waste more effectively.
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Affiliation(s)
- Daniel E Troyetsky
- Department of Mechanical Engineering, University of Rochester, Rochester, 14627, NY, USA
| | - Jeffrey Tithof
- Department of Mechanical Engineering, University of Rochester, Rochester, 14627, NY, USA
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, 55455, MN, USA
| | - John H Thomas
- Department of Mechanical Engineering, University of Rochester, Rochester, 14627, NY, USA
| | - Douglas H Kelley
- Department of Mechanical Engineering, University of Rochester, Rochester, 14627, NY, USA.
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Faghih MM, Keith Sharp M. Mechanisms of tracer transport in cerebral perivascular spaces. J Biomech 2021; 118:110278. [PMID: 33548658 DOI: 10.1016/j.jbiomech.2021.110278] [Citation(s) in RCA: 15] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/02/2021] [Accepted: 01/16/2021] [Indexed: 02/09/2023]
Abstract
Tracers infused into the brain appear to be transported along channels surrounding cerebral blood vessels. Bulk fluid flow has been hypothesized in paravascular "glymphatic" channels (outer space between the pial membrane and astrocyte endfeet), as well as in the periarterial space (inner space between smooth muscle cells). The plausibility of net flow in these channels due to steady and oscillatory pressures is reviewed, as is that of transport by oscillatory shear-enhanced dispersion in the absence of net flow. Models including 1D branching networks of annular channels and an expanded compartmental model for humans both predict that flow driven by physiologic steady pressure differences is unlikely in both periarterial and paraarterial spaces, whether the spaces are open or filled with porous media. One exception is that a small additional steady pressure difference could drive paraarterial flow if the space is open. The potential that the tracer injection itself could present such a pressure difference is outlined. Oscillatory (peristaltic) wall motion alone has been found to be insufficient to drive significant forward flow. However, a number of hypothesized mechanisms that have yet to be experimentally verified in the brain may create directional flow in combination with wall motion. Shear-augmented dispersion due to oscillatory pressure in channels with a range of porosity has been modeled analytically. Enhancement of axial dispersion is small for periarterial channels. In open paraarterial channels, dispersion enhancement with optimal lateral mixing is large enough that it may explain observed tracer transport without net forward fluid flow.
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Affiliation(s)
- Mohammad M Faghih
- Department of Mechanical Engineering, University of Louisville Louisville, KY 40292, United States
| | - M Keith Sharp
- Department of Mechanical Engineering, University of Louisville Louisville, KY 40292, United States.
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50
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Daversin-Catty C, Vinje V, Mardal KA, Rognes ME. The mechanisms behind perivascular fluid flow. PLoS One 2020; 15:e0244442. [PMID: 33373419 PMCID: PMC7771676 DOI: 10.1371/journal.pone.0244442] [Citation(s) in RCA: 29] [Impact Index Per Article: 7.3] [Reference Citation Analysis] [Abstract] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/19/2020] [Accepted: 12/09/2020] [Indexed: 11/26/2022] Open
Abstract
Flow of cerebrospinal fluid (CSF) in perivascular spaces (PVS) is one of the key concepts involved in theories concerning clearance from the brain. Experimental studies have demonstrated both net and oscillatory movement of microspheres in PVS (Mestre et al. (2018), Bedussi et al. (2018)). The oscillatory particle movement has a clear cardiac component, while the mechanisms involved in net movement remain disputed. Using computational fluid dynamics, we computed the CSF velocity and pressure in a PVS surrounding a cerebral artery subject to different forces, representing arterial wall expansion, systemic CSF pressure changes and rigid motions of the artery. The arterial wall expansion generated velocity amplitudes of 60-260 μm/s, which is in the upper range of previously observed values. In the absence of a static pressure gradient, predicted net flow velocities were small (<0.5 μm/s), though reaching up to 7 μm/s for non-physiological PVS lengths. In realistic geometries, a static systemic pressure increase of physiologically plausible magnitude was sufficient to induce net flow velocities of 20-30 μm/s. Moreover, rigid motions of the artery added to the complexity of flow patterns in the PVS. Our study demonstrates that the combination of arterial wall expansion, rigid motions and a static CSF pressure gradient generates net and oscillatory PVS flow, quantitatively comparable with experimental findings. The static CSF pressure gradient required for net flow is small, suggesting that its origin is yet to be determined.
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Affiliation(s)
- Cécile Daversin-Catty
- Simula Research Laboratory, Department of Numerical Analysis and Scientific Computing, Lysaker, Norway
| | - Vegard Vinje
- Simula Research Laboratory, Department of Numerical Analysis and Scientific Computing, Lysaker, Norway
| | - Kent-André Mardal
- Simula Research Laboratory, Department of Numerical Analysis and Scientific Computing, Lysaker, Norway
- Department of Mathematics, University of Oslo, Oslo, Norway
| | - Marie E. Rognes
- Simula Research Laboratory, Department of Numerical Analysis and Scientific Computing, Lysaker, Norway
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