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Parmaksiz D, Kim Y. Navigating Central Oxytocin Transport: Known Realms and Uncharted Territories. Neuroscientist 2025; 31:234-261. [PMID: 39113465 PMCID: PMC12103645 DOI: 10.1177/10738584241268754] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 01/06/2025]
Abstract
Complex mechanisms govern the transport and action of oxytocin (Oxt), a neuropeptide and hormone that mediates diverse physiologic processes. While Oxt exerts site-specific and rapid effects in the brain via axonal and somatodendritic release, volume transmission via CSF and the neurovascular interface can act as an additional mechanism to distribute Oxt signals across distant brain regions on a slower timescale. This review focuses on modes of Oxt transport and action in the CNS, with particular emphasis on the roles of perivascular spaces, the blood-brain barrier (BBB), and circumventricular organs in coordinating the triadic interaction among circulating blood, CSF, and parenchyma. Perivascular spaces, critical conduits for CSF flow, play a pivotal role in Oxt diffusion and distribution within the CNS and reciprocally undergo Oxt-mediated structural and functional reconstruction. While the BBB modulates the movement of Oxt between systemic and cerebral circulation in a majority of brain regions, circumventricular organs without a functional BBB can allow for diffusion, monitoring, and feedback regulation of bloodborne peripheral signals such as Oxt. Recognition of these additional transport mechanisms provides enhanced insight into the systemic propagation and regulation of Oxt activity.
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Affiliation(s)
- Deniz Parmaksiz
- Department of Neural and Behavioral Sciences, College of Medicine, The Pennsylvania State University, Hershey, PA, USA
- Center for Neural Engineering, The Pennsylvania State University, University Park, PA, USA
| | - Yongsoo Kim
- Department of Neural and Behavioral Sciences, College of Medicine, The Pennsylvania State University, Hershey, PA, USA
- Center for Neural Engineering, The Pennsylvania State University, University Park, PA, USA
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2
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Bellier F, Walter A, Lecoin L, Chauveau F, Rouach N, Rancillac A. Astrocytes at the heart of sleep: from genes to network dynamics. Cell Mol Life Sci 2025; 82:207. [PMID: 40397158 PMCID: PMC12095758 DOI: 10.1007/s00018-025-05671-3] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/14/2024] [Revised: 03/15/2025] [Accepted: 03/18/2025] [Indexed: 05/22/2025]
Abstract
Astrocytes have transcended their role from mere structural scaffolds to pivotal regulators of neural circuitry and sleep-wake dynamics. The strategic proximity of their fine processes to blood vessels and synapses positions them as key players in neurobiology, contributing to the tripartite synapse concept. Gap-junction proteins also enable astrocytes to form an extensive network interacting with neuronal assemblies to influence sleep physiology. Recent advances in genetic engineering, neuroimaging and molecular biology have deepened our understanding of astrocytic functions. This review highlights the different mechanisms by which astrocytes regulate sleep, notably through transcriptomic and morphological changes, as well as gliotransmission, whereby intracellular calcium (Ca2+) dynamics plays a significant role in modulating the sleep-wake cycle. In vivo optogenetic stimulation of astrocytes indeed induces ATP release, which is subsequently degraded into adenosine, modulating neuronal excitability in sleep-wake regulatory brain regions. Astrocytes also participate in synaptic plasticity, potentially modulating sleep-associated downscaling, a process essential for memory consolidation and preventing synaptic saturation. Although astrocytic involvement in synaptic maintenance is well supported, the precise molecular mechanisms linking these processes to sleep regulation remain to be elucidated. By highlighting astrocytes' multiple roles in sleep physiology, these insights deepen our understanding of sleep mechanisms and pave the way for improving sleep quality.
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Affiliation(s)
- Félix Bellier
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology-CIRB, Collège de France, CNRS UMR 7241/Inserm U1050, Université PSL, PSL-NEURO, 11, Place Marcelin Berthelot, 75005, Paris, France
- IRBA (Institut de Recherche Biomédicale Des Armées), Brétigny-sur-Orge, France
| | - Augustin Walter
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology-CIRB, Collège de France, CNRS UMR 7241/Inserm U1050, Université PSL, PSL-NEURO, 11, Place Marcelin Berthelot, 75005, Paris, France
| | - Laure Lecoin
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology-CIRB, Collège de France, CNRS UMR 7241/Inserm U1050, Université PSL, PSL-NEURO, 11, Place Marcelin Berthelot, 75005, Paris, France
| | - Fréderic Chauveau
- IRBA (Institut de Recherche Biomédicale Des Armées), Brétigny-sur-Orge, France
| | - Nathalie Rouach
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology-CIRB, Collège de France, CNRS UMR 7241/Inserm U1050, Université PSL, PSL-NEURO, 11, Place Marcelin Berthelot, 75005, Paris, France
| | - Armelle Rancillac
- Neuroglial Interactions in Cerebral Physiology and Pathologies, Center for Interdisciplinary Research in Biology-CIRB, Collège de France, CNRS UMR 7241/Inserm U1050, Université PSL, PSL-NEURO, 11, Place Marcelin Berthelot, 75005, Paris, France.
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3
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Guo Y, Quirk K, Kelley DH, Thomas JH. Advection and diffusion in perivascular and extracellular spaces in the brain. J R Soc Interface 2025; 22:20250010. [PMID: 40393523 DOI: 10.1098/rsif.2025.0010] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/04/2025] [Revised: 02/06/2025] [Accepted: 02/25/2025] [Indexed: 05/22/2025] Open
Abstract
Knowledge of the relative importance of advection and diffusion in clearing waste from the brain has been elusive, especially concerning the extracellular space (ECS). With local and global computational models of the mouse brain, we explore how the presence or absence of advection in the ECS affects solute transport. Without advection in the ECS, clearance would occur by diffusion into flowing cerebrospinal fluid in perivascular spaces (PVSs) or elsewhere, but we find this process to be severely limited by build-up of solute in the PVSs. We simulate flow in the ECS driven by a pressure drop between arteriole and venule PVSs, which enhances clearance considerably. To assess the relative importance of advection and diffusion, we introduce a local Péclet number [Formula: see text], a dimensionless scalar field. For our simulations, [Formula: see text] through much of the ECS but [Formula: see text] near PVSs near the brain surface. This local dominance of advection in the ECS establishes a clearance mechanism markedly different from that produced by diffusion alone. In network simulations that explore different parameter values and efflux routes, the pressures needed to drive the PVS flows measured in vivo are unrealistically large for most cases lacking ECS flow. Collectively, our models indicate that a flow in the ECS is necessary to explain experimental measurements and maintain homeostasis.
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Affiliation(s)
- Yisen Guo
- Mechanical Engineering, University of Rochester, Rochester, NY, USA
| | - Keelin Quirk
- Mechanical Engineering, University of Rochester, Rochester, NY, USA
| | - Douglas H Kelley
- Mechanical Engineering, University of Rochester, Rochester, NY, USA
| | - John H Thomas
- Mechanical Engineering, University of Rochester, Rochester, NY, USA
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4
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Koch T, Mardal KA. Estimation of fluid flow velocities in cortical brain tissue driven by the microvasculature. Interface Focus 2025; 15:20240042. [PMID: 40191021 PMCID: PMC11969191 DOI: 10.1098/rsfs.2024.0042] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/26/2024] [Revised: 12/23/2024] [Accepted: 01/21/2025] [Indexed: 04/09/2025] Open
Abstract
We present a modelling framework for describing bulk fluid flow in brain tissue. Within this framework, using computational simulation, we estimate bulk flow velocities in the grey matter parenchyma due to static or slowly varying water potential gradients-hydrostatic pressure gradients and osmotic pressure gradients. Working with the situation that experimental evidence and some model parameter estimates, as we point out, are presently insufficient to estimate velocities precisely, we explore feasible parameter ranges resulting in a range of estimates. We consider the effect of realistic microvascular architecture (extracted from mouse cortical grey matter). Although the estimated velocities are small in magnitude (e.g. in comparison to blood flow velocities), the passive transport of solutes with the bulk fluid can be a relevant process when considering larger molecules transported over larger distances. We compare velocity magnitudes resulting from filtration and pulsations. Filtration can lead to continuous directed fluid flow in the parenchyma, while pulsation-driven flow is (at least partly) reversible. For the first time, we consider the effect of the vascular architecture on the velocity distribution in a tissue sample of ca 1 mm3 cortical grey matter tissue. We conclude that both filtration and pulsations are potentially potent drivers for fluid flow.
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Affiliation(s)
- Timo Koch
- Department of Mathematics, University of Oslo, Oslo, Norway
| | - Kent-André Mardal
- Department of Mathematics, University of Oslo, Oslo, Norway
- Department of Scientific Computing and Numerical Analysis (SCAN), Simula Research Laboratory, Oslo, Norway
- KG Jebsen Centre for Brain Fluid Research, Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
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5
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Xu Y, Yin H, Li L, Wang X, Hou Q. Covert cerebrospinal fluid dynamics dysfunction: evolution from conventional to innovative therapies. Front Neurol 2025; 16:1554813. [PMID: 40144621 PMCID: PMC11936825 DOI: 10.3389/fneur.2025.1554813] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/10/2025] [Accepted: 02/27/2025] [Indexed: 03/28/2025] Open
Abstract
Cerebrospinal fluid (CSF) dynamics disorders are intricately linked to diverse neurological pathologies, though they usually are mild and covert. Contemporary insights into glymphatic system function, particularly the CSF transport, drainage, and its role in clearing metabolic waste and toxic substances in both normal and pathological states, and the pivotal role of aquaporin-4 (AQP4) in CSF-interstitial fluid (ISF) exchange, have established novel theoretical frameworks of subclinical CSF dynamics dysfunction, and have promoted the development of non-surgical therapeutic approaches for them simultaneously. This review comprehensively analyzes the advancement of non-surgical interventions for CSF dynamics disorders, emphasizing the transition from established methodologies to innovative approaches. Current non-surgical treatment strategies primarily encompass three directions: pharmacological therapy, physical therapy, and biological regulation therapy. In terms of pharmacological interventions, developments from traditional diuretics to novel small-molecule drugs show promising therapeutic potential. In physical therapy, innovative techniques such as lower body negative pressure, transcranial magnetic stimulation, and vagus nerve stimulation have provided new options for clinical practice. Meanwhile, biological regulation therapy, exemplified by recombinant VEGF-C administration, has established novel therapeutic paradigms. These therapeutic strategies have demonstrated potential in improving CSF dynamics and enhancing CSF waste elimination. Future research should focus on developing individualized treatment protocols, elucidating of therapeutic mechanisms, and assessing longitudinal outcomes. This will facilitate the development of more precise therapeutic strategies and exploration of optimized multimodal treatment combinations in handling the so-called convert CSF dynamics dysfunction.
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Affiliation(s)
- Yi Xu
- Department of Rehabilitation Medicine, The Seventh Affiliated Hospital, Sun Yat-sen University, Shenzhen, China
| | - Hua Yin
- Class 6, 2020 Clinical Medicine Program, Sun Yat-Sen University, Shenzhen, China
| | - Lingge Li
- Class 2, 2020 Clinical Medicine Program, Sun Yat-Sen University, Shenzhen, China
| | - Xiaodi Wang
- Department of Neurology, Clinical Neuroscience Center, The Seventh Affiliated Hospital, Sun Yat-sen University, Shenzhen, China
| | - Qinghua Hou
- Department of Neurology, Clinical Neuroscience Center, The Seventh Affiliated Hospital, Sun Yat-sen University, Shenzhen, China
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6
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Jones R, Cirovic S, Rusbridge C. A review of cerebrospinal fluid circulation with respect to Chiari-like malformation and syringomyelia in brachycephalic dogs. Fluids Barriers CNS 2025; 22:25. [PMID: 40065427 PMCID: PMC11895204 DOI: 10.1186/s12987-025-00636-x] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/23/2024] [Accepted: 02/19/2025] [Indexed: 03/14/2025] Open
Abstract
Cerebrospinal fluid (CSF) plays a crucial role in maintaining brain homeostasis by facilitating the clearance of metabolic waste and regulating intracranial pressure. Dysregulation of CSF flow can lead to conditions like syringomyelia, and hydrocephalus. This review details the anatomy of CSF flow, examining its contribution to waste clearance within the brain and spinal cord. The review integrates data from human, canine, and other mammalian studies, with a particular focus on brachycephalic dogs. Certain dog breeds exhibit a high prevalence of CSF-related conditions due to artificial selection for neotenous traits, making them valuable models for studying analogous human conditions, such as Chiari-like malformation and syringomyelia associated with craniosynostosis. This review discusses the anatomical features specific to some brachycephalic breeds and the impact of skull and cranial cervical conformation on CSF flow patterns, providing insights into the pathophysiology and potential modelling approaches for these conditions.
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Affiliation(s)
- Ryan Jones
- School of Veterinary Medicine, University of Surrey, Guildford, GU2 7XH, UK.
| | - Srdjan Cirovic
- Department of Mechanical Engineering Sciences, University of Surrey, Guildford, GU2 7XH, UK
| | - Clare Rusbridge
- School of Veterinary Medicine, University of Surrey, Guildford, GU2 7XH, UK
- Wear Referrals Veterinary Specialist & Emergency Hospital, Bradbury, Stockton-On-Tees, UK
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7
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Hauglund NL, Andersen M, Tokarska K, Radovanovic T, Kjaerby C, Sørensen FL, Bojarowska Z, Untiet V, Ballestero SB, Kolmos MG, Weikop P, Hirase H, Nedergaard M. Norepinephrine-mediated slow vasomotion drives glymphatic clearance during sleep. Cell 2025; 188:606-622.e17. [PMID: 39788123 DOI: 10.1016/j.cell.2024.11.027] [Citation(s) in RCA: 30] [Impact Index Per Article: 30.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/01/2023] [Revised: 08/29/2024] [Accepted: 11/18/2024] [Indexed: 01/12/2025]
Abstract
As the brain transitions from wakefulness to sleep, processing of external information diminishes while restorative processes, such as glymphatic removal of waste products, are activated. Yet, it is not known what drives brain clearance during sleep. We here employed an array of technologies and identified tightly synchronized oscillations in norepinephrine, cerebral blood volume, and cerebrospinal fluid (CSF) as the strongest predictors of glymphatic clearance during NREM sleep. Optogenetic stimulation of the locus coeruleus induced anti-correlated changes in vasomotion and CSF signal. Furthermore, stimulation of arterial oscillations enhanced CSF inflow, demonstrating that vasomotion acts as a pump driving CSF into the brain. On the contrary, the sleep aid zolpidem suppressed norepinephrine oscillations and glymphatic flow, highlighting the critical role of norepinephrine-driven vascular dynamics in brain clearance. Thus, the micro-architectural organization of NREM sleep, driven by norepinephrine fluctuations and vascular dynamics, is a key determinant for glymphatic clearance.
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Affiliation(s)
- Natalie L Hauglund
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen N, Denmark; Department of Physiology, Anatomy and Genetics, University of Oxford, Oxford OX1 3PT, UK; Danish Center for Sleep Medicine, Department of Clinical Neurophysiology, Rigshospitalet, 2600 Glostrup, Denmark
| | - Mie Andersen
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Klaudia Tokarska
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Tessa Radovanovic
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Celia Kjaerby
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Frederikke L Sørensen
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Zuzanna Bojarowska
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Verena Untiet
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Sheyla B Ballestero
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Mie G Kolmos
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Pia Weikop
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Hajime Hirase
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen N, Denmark
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, University of Copenhagen, 2200 Copenhagen N, Denmark; Center for Translational Neuromedicine, University of Rochester, Rochester, NY 14627, USA.
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8
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Zhu Y, Zhu J, Ni C, Chen A, Li L, Gao Y, Shoffstall AJ, Yu X. Impact of infusion conditions and anesthesia on CSF tracer dynamics in mouse brain. BIORXIV : THE PREPRINT SERVER FOR BIOLOGY 2025:2025.01.21.634133. [PMID: 39896601 PMCID: PMC11785030 DOI: 10.1101/2025.01.21.634133] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Subscribe] [Scholar Register] [Indexed: 02/04/2025]
Abstract
Tracer imaging has been instrumental in mapping the brain's solute transport pathways facilitated by cerebrospinal fluid (CSF) flow. However, the impact of tracer infusion parameters on CSF flow remains incompletely understood. This study evaluated the influence of infusion location, rate, and anesthetic regimens on tracer transport using dynamic contrast-enhanced MRI with Gd-DTPA as a CSF tracer. Infusion rate effects were assessed by administering Gd-DTPA into the cisterna magna (ICM) at two rates under isoflurane anesthesia. Anesthetic effects were evaluated by comparing transport patterns between isoflurane and ketamine/xylazine (K/X) anesthesia at the slower rate. Gd-DTPA transport was also examined after lateral ventricle (ICV) infusion, the primary site of CSF production. The results demonstrate that, besides anesthesia, both the location and rate of infusion substantially affected solute transport within the brain. ICV infusion led to rapid, extensive transport into deep brain regions, while slower ICM infusion resulted in more pronounced transport to dorsal brain regions. Cross-correlation and hierarchical clustering analyses of region-specific Gd-DTPA signal time courses revealed that ICM infusion facilitated transport along periarterial spaces, while ICV infusion favored transport across the ventricular-parenchymal interface. These findings underscore the importance of experimental conditions in influencing tracer kinetics and spatial distribution in the brain.
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Affiliation(s)
- Yuran Zhu
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA
| | - Junqing Zhu
- Department of Radiology, Case Western Reserve University, Cleveland, Ohio, USA
| | - Chenxin Ni
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA
| | - Anbang Chen
- Department of Electrical, Computer, and Systems Engineering, Case Western Reserve University, Cleveland, Ohio, USA
| | - Longshun Li
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA
| | - Yue Gao
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA
| | - Andrew J. Shoffstall
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA
| | - Xin Yu
- Department of Biomedical Engineering, Case Western Reserve University, Cleveland, Ohio, USA
- Department of Radiology, Case Western Reserve University, Cleveland, Ohio, USA
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9
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Bork PAR, Gianetto M, Newbold E, Hablitz L, Bohr T, Nedergaard M. Blood osmolytes such as sugar can drive brain fluid flows in a poroelastic model. Sci Rep 2024; 14:29017. [PMID: 39578667 PMCID: PMC11584662 DOI: 10.1038/s41598-024-80593-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: 07/05/2024] [Accepted: 11/19/2024] [Indexed: 11/24/2024] Open
Abstract
The glymphatic system of fluid flow through brain tissue may clear amyloid-β during sleep and as such underlie the need for sleep. Dysfunctional glymphatic transport has been implicated in pathological conditions ranging from stroke and dementia to psychiatric illnesses. To date, the fastest observed in-vivo brain flows have been reported after the manipulation of blood osmotic pressures. Surprisingly, the brain seems to shrink while receiving more influx. Though influx of an incompressible fluid might expand the tissue, no physical theory for these observations has been proposed. We here present a minimal mathematical model of brain pressure, deformation, and fluid flows due to vascular osmotic pressures. The model is based on Darcy flow, linear poroelasticity theory and conservation of mass. We propose that a screened Poisson equation holds for interstitial pressure because vascular filtration corresponds to fluid divergence. The model resolves the apparent paradox of combined fluid influx with tissue shrinkage by showing that fluid absorption into the blood can drive both. In this model, small glucose concentration differences between plasma and brain can drive brain flow velocities observed in recent in-vivo assays. Osmosis may therefore drive brain fluid flow under physiological conditions and provide an explanation for the known correlations between diabetes and dementia.
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Affiliation(s)
- Peter A R Bork
- Department of Physics, Technical University of Denmark, 2800, Kongens Lyngby, Denmark.
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark.
| | - Michael Gianetto
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, 14642, USA
| | - Evan Newbold
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, 14642, USA
| | - Lauren Hablitz
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, 14642, USA
| | - Tomas Bohr
- Department of Physics, Technical University of Denmark, 2800, Kongens Lyngby, Denmark
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, 14642, USA
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, 2200, Copenhagen, Denmark
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10
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Gjerde IG, Kuchta M, Rognes ME, Wohlmuth B. Directional flow in perivascular networks: mixed finite elements for reduced-dimensional models on graphs. J Math Biol 2024; 89:60. [PMID: 39511029 PMCID: PMC11543763 DOI: 10.1007/s00285-024-02154-0] [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: 12/23/2023] [Revised: 09/29/2024] [Accepted: 10/02/2024] [Indexed: 11/15/2024]
Abstract
Flow of cerebrospinal fluid through perivascular pathways in and around the brain may play a crucial role in brain metabolite clearance. While the driving forces of such flows remain enigmatic, experiments have shown that pulsatility is central. In this work, we present a novel network model for simulating pulsatile fluid flow in perivascular networks, taking the form of a system of Stokes-Brinkman equations posed over a perivascular graph. We apply this model to study physiological questions concerning the mechanisms governing perivascular fluid flow in branching vascular networks. Notably, our findings reveal that even long wavelength arterial pulsations can induce directional flow in asymmetric, branching perivascular networks. In addition, we establish fundamental mathematical and numerical properties of these Stokes-Brinkman network models, with particular attention to increasing graph order and complexity. By introducing weighted norms, we show the well-posedness and stability of primal and dual variational formulations of these equations, and that of mixed finite element discretizations.
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Affiliation(s)
- Ingeborg G Gjerde
- Norwegian Geotechnical Institute, Oslo, Norway.
- Simula Research Laboratory, Oslo, Norway.
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11
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Han G, Jiao B, Zhang Y, Wang Z, Liang C, Li Y, Hsu YC, Bai R. Arterial pulsation dependence of perivascular cerebrospinal fluid flow measured by dynamic diffusion tensor imaging in the human brain. Neuroimage 2024; 297:120653. [PMID: 38795798 DOI: 10.1016/j.neuroimage.2024.120653] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/13/2024] [Revised: 05/14/2024] [Accepted: 05/23/2024] [Indexed: 05/28/2024] Open
Abstract
Perivascular cerebrospinal fluid (pCSF) flow is a key component of the glymphatic system. Arterial pulsation has been proposed as the main driving force of pCSF influx along the superficial and penetrating arteries; however, evidence of this mechanism in humans is limited. We proposed an experimental framework of dynamic diffusion tensor imaging with low b-values and ultra-long echo time (dynDTIlow-b) to capture pCSF flow properties during the cardiac cycle in human brains. Healthy adult volunteers (aged 17-28 years; seven men, one woman) underwent dynDTIlow-b using a 3T scanner (MAGNETOM Prisma, Siemens Healthcare, Erlangen, Germany) with simultaneously recorded cardiac output. The results showed that diffusion tensors reconstructed from pCSF were mainly oriented in the direction of the neighboring arterial flow. When switching from vasoconstriction to vasodilation, the axial and radial diffusivities of the pCSF increased by 5.7 % and 4.94 %, respectively, suggesting that arterial pulsation alters the pCSF flow both parallel and perpendicular to the arterial wall. DynDTIlow-b signal intensity at b=0 s/mm2 (i.e., T2-weighted, [S(b=0 s/mm2)]) decreased in systole, but this change was ∼7.5 % of a cardiac cycle slower than the changes in apparent diffusivity, suggesting that changes in S(b=0 s/mm2) and apparent diffusivity arise from distinct physiological processes and potential biomarkers associated with perivascular space volume and pCSF flow, respectively. Additionally, the mean diffusivities of white matter showed cardiac-cycle dependencies similar to pCSF, although a delay relative to the peak time of apparent diffusivity in pCSF was present, suggesting that dynDTIlow-b could potentially reveal the dynamics of magnetic resonance imaging-invisible pCSF surrounding small arteries and arterioles in white matter; this delay may result from pulse wave propagation along penetrating arteries. In conclusion, the vasodilation-induced increases in axial and radial diffusivities of pCSF and mean diffusivities of white matter are consistent with the notion that arterial pulsation can accelerate pCSF flow in human brain. Furthermore, the proposed dynDTIlow-b technique can capture various pCSF dynamics in artery pulsation.
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Affiliation(s)
- Guangxu Han
- Key Laboratory of Biomedical Engineering of Education Ministry, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, China; Nanhu Brain-computer Interface Institute, Hangzhou, 311100, China; Interdisciplinary Institute of Neuroscience and Technology, Zhejiang University School of Medicine, Hangzhou, China
| | - Bingjie Jiao
- Key Laboratory of Biomedical Engineering of Education Ministry, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, China; Lingang Laboratory, Shanghai, 200031, China; Interdisciplinary Institute of Neuroscience and Technology, Zhejiang University School of Medicine, Hangzhou, China
| | - Yifan Zhang
- Key Laboratory of Biomedical Engineering of Education Ministry, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, China
| | - Zejun Wang
- Key Laboratory of Biomedical Engineering of Education Ministry, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, China
| | - Chunjing Liang
- Key Laboratory of Biomedical Engineering of Education Ministry, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, China
| | - Yong Li
- Key Laboratory of Biomedical Engineering of Education Ministry, College of Biomedical Engineering and Instrument Science, Zhejiang University, Hangzhou, China
| | - Yi-Cheng Hsu
- MR Research Collaboration Team, Siemens Healthineers Ltd., Shanghai, China
| | - Ruiliang Bai
- Interdisciplinary Institute of Neuroscience and Technology, Zhejiang University School of Medicine, Hangzhou, China; Liangzhu Laboratory, MOE Frontier Science Center for Brain Science and Brain-machine Integration, State Key Laboratory of Brain-machine Intelligence, Zhejiang University, Hangzhou, 311121, China; NHC and CAMS Key Laboratory of Medical Neurobiology, Zhejiang University, Hangzhou, 310058, China; Key Laboratory of Novel Targets and Drug Study for Neural Repair of Zhejiang Province, School of Medicine, Hangzhou City University.
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12
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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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Gan Y, Thomas JH, Kelley DH. Gaps in the wall of a perivascular space act as valves to produce a directed flow of cerebrospinal fluid: a hoop-stress model. J R Soc Interface 2024; 21:20230659. [PMID: 38565158 PMCID: PMC10987236 DOI: 10.1098/rsif.2023.0659] [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: 11/08/2023] [Accepted: 03/04/2024] [Indexed: 04/04/2024] 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. Astrocyte endfeet bound the PVSs of penetrating arteries, separating them from brain extracellular space. Gaps between astrocyte endfeet might provide a low-resistance pathway for fluid transport across the wall. Recent studies suggest that the astrocyte endfeet function as valves that rectify the CSF flow, producing the net flow observed in pial PVSs by changing the size of the gaps in response to pressure changes. In this study, we quantify this rectification based on three features of the PVSs: the quasi-circular geometry, the deformable endfoot wall, and the pressure oscillation inside. We provide an analytical model, based on the thin-shell hoop-stress approximation, and predict a pumping efficiency of about 0.4, which would contribute significantly to the observed flow. When we add the flow resistance of the extracellular space (ECS) to the model, we find an increased net flow during sleep, due to the known increase in ECS porosity (decreased flow resistance) compared to that in the awake state. We corroborate our analytical model with three-dimensional fluid-solid interaction simulations.
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Affiliation(s)
- Yiming Gan
- 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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