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Bouffard MA, Avanaki MA, Ford JN, Jaafar N, Brook A, Abbasi B, Torun N, Alsop D, Comeau DS, Chang YM. MRI Indices of Glymphatic Function Correlate With Disease Duration in Idiopathic Intracranial Hypertension. J Neuroophthalmol 2024:00041327-990000000-00705. [PMID: 39228018 DOI: 10.1097/wno.0000000000002259] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 09/05/2024]
Abstract
BACKGROUND The glymphatic system represents an extravascular network of astrocytic channels responsible for interstitial fluid and solute transit through the brain parenchyma. Its dysfunction has been considered as a possible cause of idiopathic intracranial hypertension (IIH). METHODS We enrolled participants with active IIH, treated or cured IIH, and controls. The active IIH group was divided into untreated participants with recently developed (<6 mo) and chronic (6+ mo) disease. Glymphatic function was assessed using diffusion tensor imaging along the paravascular space (DTI-ALPS) to generate an ALPS-index, hypothesized to measure glymphatic function. Participants were imaged before lumbar puncture (LP) if IIH was suspected and following LP when possible. RESULTS ALPS indices were higher in participants with chronically present, active IIH than in those either with recently developed IIH or control participants. ALPS-indices correlated with papilledema but did not correlate significantly with age, BMI, or intracranial pressure (ICP). CONCLUSIONS Our findings suggest that DTI-ALPS-indices of glymphatic function may be influenced by the chronicity of intracranial hypertension but do not support the hypothesis that glymphatic dysfunction causes IIH. Though these findings are preliminary, glymphatic imaging may be a useful radiographic biomarker in IIH.
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Affiliation(s)
- Marc A Bouffard
- Departments of Neurology (MB, BA), Radiology (MAA, NJ, AB, DA, DSC, Y-MC), and Surgery (NT), Beth Israel Deaconess Medical Center, Boston, Massachusetts; Department of Ophthalmology (MB, BA), Massachusetts Eye and Ear, Boston, Massachusetts; and Department of Radiology (JF), Massachusetts General Hospital, Boston, Massachusetts
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Yuan T, Zhan W, Terzano M, Holzapfel GA, Dini D. A comprehensive review on modeling aspects of infusion-based drug delivery in the brain. Acta Biomater 2024; 185:1-23. [PMID: 39032668 DOI: 10.1016/j.actbio.2024.07.015] [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: 03/21/2024] [Revised: 07/10/2024] [Accepted: 07/11/2024] [Indexed: 07/23/2024]
Abstract
Brain disorders represent an ever-increasing health challenge worldwide. While conventional drug therapies are less effective due to the presence of the blood-brain barrier, infusion-based methods of drug delivery to the brain represent a promising option. Since these methods are mechanically controlled and involve multiple physical phases ranging from the neural and molecular scales to the brain scale, highly efficient and precise delivery procedures can significantly benefit from a comprehensive understanding of drug-brain and device-brain interactions. Behind these interactions are principles of biophysics and biomechanics that can be described and captured using mathematical models. Although biomechanics and biophysics have received considerable attention, a comprehensive mechanistic model for modeling infusion-based drug delivery in the brain has yet to be developed. Therefore, this article reviews the state-of-the-art mechanistic studies that can support the development of next-generation models for infusion-based brain drug delivery from the perspective of fluid mechanics, solid mechanics, and mathematical modeling. The supporting techniques and database are also summarized to provide further insights. Finally, the challenges are highlighted and perspectives on future research directions are provided. STATEMENT OF SIGNIFICANCE: Despite the immense potential of infusion-based drug delivery methods for bypassing the blood-brain barrier and efficiently delivering drugs to the brain, achieving optimal drug distribution remains a significant challenge. This is primarily due to our limited understanding of the complex interactions between drugs and the brain that are governed by principles of biophysics and biomechanics, and can be described using mathematical models. This article provides a comprehensive review of state-of-the-art mechanistic studies that can help to unravel the mechanism of drug transport in the brain across the scales, which underpins the development of next-generation models for infusion-based brain drug delivery. More broadly, this review will serve as a starting point for developing more effective treatments for brain diseases and mechanistic models that can be used to study other soft tissue and biomaterials.
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Affiliation(s)
- Tian Yuan
- Department of Mechanical Engineering, Imperial College London, SW7 2AZ, UK.
| | - Wenbo Zhan
- School of Engineering, University of Aberdeen, Aberdeen, AB24 3UE, UK
| | - Michele Terzano
- Institute of Biomechanics, Graz University of Technology, Austria
| | - Gerhard A Holzapfel
- Institute of Biomechanics, Graz University of Technology, Austria; Department of Structural Engineering, NTNU, Trondheim, Norway
| | - Daniele Dini
- Department of Mechanical Engineering, Imperial College London, SW7 2AZ, UK.
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Janerås L, Breivik H, Lundeland B, Ringstad GA, Stubhaug A. Long-term intrathecal infusion of low-dose morphine effectively relieves symptoms of severe restless legs syndrome/Willis-Ekbom disease without inducing opioid tolerance. Pain 2024:00006396-990000000-00677. [PMID: 39106456 DOI: 10.1097/j.pain.0000000000003311] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 10/19/2023] [Accepted: 05/20/2024] [Indexed: 08/09/2024]
Abstract
ABSTRACT Restless legs syndrome/Willis-Ekbom disease (RLS/WED) causes a strong urge to move legs while resting. Restless legs syndrome/WED is an often-inherited disease occurring in 3% to 10% of adult populations, increasing with age. Severity varies from mild disturbance of sleep to painful restless legs and arms, loss of sleep, fatigue, and risk of suicide. Dopaminergic drugs relieve symptoms, but cause augmentation, ie, initially helpful but later increase the burden of symptoms. Oral gabapentinoids and opioids are often added, but opioid tolerance and adverse effects are common. With the high prevalence and incomplete help from oral drugs, significant unmet needs exist for effective therapy for severe RLS/WED. Ongoing spinal intrathecal infusion of low-dose morphine is effective, but not generally recognized, as only 12 cases have been published since 2002. We report 7 patients suffering from severe RLS/WED, who had no relief from oral dopaminergic, gabapentinoid, or opioid drugs; they all had excellent relief during ongoing spinal intrathecal infusion of morphine at only 1 to 5 μg/h, ongoing for 1 to 21 years without need of higher doses of morphine.. We suggest that morphine may be transported with the cerebrospinal fluid reaching and readjusting malfunctioning dopamine neuronal systems in the brain and spinal cord. The effects last only as long as the infusion continues. A patient with RLS/WED and persistent genital arousal disorder (PGAD) was relieved of both RLS/WED and PGAD symptoms. These case reports suggest that intrathecal infusion of low-dose morphine is an effective treatment of severe RLS.
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Affiliation(s)
- Lars Janerås
- Department of Pain Management and Research, Oslo University Hospital, Oslo, Norway
- Department of Anaesthesia, Karlstad Central Hospital, Karlstad, Sweden
| | - Harald Breivik
- Department of Pain Management and Research, Oslo University Hospital, Oslo, Norway
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Bård Lundeland
- Department of Pain Management and Research, Oslo University Hospital, Oslo, Norway
| | - Geir Andre Ringstad
- Department of Radiology, Oslo University Hospital-Rikshospitalet, Oslo, Norway
- Department of Geriatrics and Internal Medicine, Sørlandet Hospital, Arendal, Norway
| | - Audun Stubhaug
- Department of Pain Management and Research, Oslo University Hospital, Oslo, Norway
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
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4
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Eide PK. Neurosurgery and the glymphatic system. Acta Neurochir (Wien) 2024; 166:274. [PMID: 38904802 PMCID: PMC11192689 DOI: 10.1007/s00701-024-06161-4] [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: 05/02/2024] [Accepted: 06/05/2024] [Indexed: 06/22/2024]
Abstract
The discovery of the glymphatic system has fundamentally altered our comprehension of cerebrospinal fluid transport and the removal of waste from brain metabolism. In the past decade, since its initial characterization, research on the glymphatic system has surged exponentially. Its potential implications for central nervous system disorders have sparked significant interest in the field of neurosurgery. Nonetheless, ongoing discussions and debates persist regarding the concept of the glymphatic system, and our current understanding largely relies on findings from experimental animal studies. This review aims to address several key inquiries: What methodologies exist for evaluating glymphatic function in humans today? What is the current evidence supporting the existence of a human glymphatic system? Can the glymphatic system be considered distinct from the meningeal-lymphatic system? What is the human evidence for glymphatic-meningeal lymphatic system failure in neurosurgical diseases? Existing literature indicates a paucity of techniques available for assessing glymphatic function in humans. Thus far, intrathecal contrast-enhanced magnetic resonance imaging (MRI) has shown the most promising results and have provided evidence for the presence of a glymphatic system in humans, albeit with limitations. It is, however, essential to recognize the interconnection between the glymphatic and meningeal lymphatic systems, as they operate in tandem. There are some human studies demonstrating deteriorations in glymphatic function associated with neurosurgical disorders, enriching our understanding of their pathophysiology. However, the translation of this knowledge into clinical practice is hindered by the constraints of current glymphatic imaging modalities.
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Affiliation(s)
- Per Kristian Eide
- Department of Neurosurgery, Oslo University Hospital - Rikshospitalet, Nydalen, Pb 4950 N-0424, Norway.
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway.
- KG Jebsen Centre for Brain Fluid Research, University of Oslo, Oslo, Norway.
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5
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Bork PAR, Hauglund NL, Mori Y, Møllgård K, Hjorth PG, Nedergaard M. Modeling of brain efflux: Constraints of brain surfaces. Proc Natl Acad Sci U S A 2024; 121:e2318444121. [PMID: 38598340 PMCID: PMC11032467 DOI: 10.1073/pnas.2318444121] [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: 10/23/2023] [Accepted: 03/04/2024] [Indexed: 04/12/2024] Open
Abstract
Fluid efflux from the brain plays an important role in solute waste clearance. Current experimental approaches provide little spatial information, and data collection is limited due to short duration or low frequency of sampling. One approach shows tracer efflux to be independent of molecular size, indicating bulk flow, yet also decelerating like simple membrane diffusion. In an apparent contradiction to this report, other studies point to tracer efflux acceleration. We here develop a one-dimensional advection-diffusion model to gain insight into brain efflux principles. The model is characterized by nine physiological constants and three efflux parameters for which we quantify prior uncertainty. Using Bayes' rule and the two efflux studies, we validate the model and calculate data-informed parameter distributions. The apparent contradictions in the efflux studies are resolved by brain surface boundaries being bottlenecks for efflux. To critically test the model, a custom MRI efflux assay measuring solute dispersion in tissue and release to cerebrospinal fluid was employed. The model passed the test with tissue bulk flow velocities in the range 60 to 190 [Formula: see text]m/h. Dimensional analysis identified three principal determinants of efflux, highlighting brain surfaces as a restricting factor for metabolite solute clearance.
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Affiliation(s)
- Peter A. R. Bork
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen2200Denmark
| | - Natalie L. Hauglund
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen2200Denmark
| | - Yuki Mori
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen2200Denmark
| | - Kjeld Møllgård
- Department of Cellular and Molecular Medicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen2200Denmark
| | - Poul G. Hjorth
- Department of Applied Mathematics and Computer Science, Technical University of Denmark, Lyngby2800Denmark
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen2200Denmark
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Kaur J, Boyd ED, Ding G, Zhang L, Luo H, Li Q, Li L, Wei M, Landschoot-Ward J, Chopp M, Zhang Z, Jiang Q. The Association between Glymphatic System and Perivascular Macrophages in Brain Waste Clearance. Diagnostics (Basel) 2024; 14:731. [PMID: 38611644 PMCID: PMC11011895 DOI: 10.3390/diagnostics14070731] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/17/2024] [Revised: 03/13/2024] [Accepted: 03/14/2024] [Indexed: 04/14/2024] Open
Abstract
The glymphatic system suggests the convective bulk flow of cerebrospinal fluid (CSF) through perivascular spaces and the interstitial spaces of the brain parenchyma for the rapid removal of toxic waste solutes from the brain. However, the presence of convective bulk flow within the brain interstitial spaces is still under debate. We first addressed this argument to determine the involvement of the glymphatic system in brain waste clearance utilizing contrast-enhanced 3D T1-weighted imaging (T1WI), diffusion tensor imaging (DTI), and confocal microscopy imaging. Furthermore, perivascular macrophages (PVMs), which are immune cells located within perivascular spaces, have not been thoroughly explored for their association with the glymphatic system. Therefore, we investigated tracer uptake by PVMs in the perivascular spaces of both the arteries/arterioles and veins/venules and the potential association of PVMs in assisting the glymphatic system for interstitial waste clearance. Our findings demonstrated that both convective bulk flow and diffusion are responsible for the clearance of interstitial waste solutes from the brain parenchyma. Furthermore, our results suggested that PVMs may play an important function in glymphatic system-mediated interstitial waste clearance. The glymphatic system and PVMs could be targeted to enhance interstitial waste clearance in patients with waste-associated neurological conditions and aging.
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Affiliation(s)
- Jasleen Kaur
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
- Department of Physics, Oakland University, Rochester, MI 48309, USA
| | - Edward D. Boyd
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
- Department of Radiology, Michigan State University, East Lansing, MI 48824, USA
| | - Guangliang Ding
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
- Department of Radiology, Michigan State University, East Lansing, MI 48824, USA
| | - Li Zhang
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
- Department of Physiology, Michigan State University, East Lansing, MI 48824, USA
| | - Hao Luo
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
| | - Qingjiang Li
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
| | - Lian Li
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
| | - Min Wei
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
| | - Julie Landschoot-Ward
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
| | - Michael Chopp
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
- Department of Physics, Oakland University, Rochester, MI 48309, USA
- Department of Physiology, Michigan State University, East Lansing, MI 48824, USA
- Department of Neurology, Wayne State University, Detroit, MI 48202, USA
| | - Zhenggang Zhang
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
- Department of Physiology, Michigan State University, East Lansing, MI 48824, USA
- Department of Neurology, Wayne State University, Detroit, MI 48202, USA
| | - Quan Jiang
- Department of Neurology, Henry Ford Health System, Detroit, MI 48202, USA; (J.K.); (E.D.B.); (G.D.); (L.Z.); (H.L.); (Q.L.); (L.L.); (M.W.); (J.L.-W.); (M.C.); (Z.Z.)
- Department of Physics, Oakland University, Rochester, MI 48309, USA
- Department of Radiology, Michigan State University, East Lansing, MI 48824, USA
- Department of Neurology, Wayne State University, Detroit, MI 48202, USA
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Abstract
The brain is a complex organ, fundamentally changing across the day to perform basic functions like sleep, thought, and regulating whole-body physiology. This requires a complex symphony of nutrients, hormones, ions, neurotransmitters and more to be properly distributed across the brain to maintain homeostasis throughout 24 hours. These solutes are distributed both by the blood and by cerebrospinal fluid. Cerebrospinal fluid contents are distinct from the general circulation because of regulation at brain barriers including the choroid plexus, glymphatic system, and blood-brain barrier. In this review, we discuss the overlapping circadian (≈24-hour) rhythms in brain fluid biology and at the brain barriers. Our goal is for the reader to gain both a fundamental understanding of brain barriers alongside an understanding of the interactions between these fluids and the circadian timing system. Ultimately, this review will provide new insight into how alterations in these finely tuned clocks may lead to pathology.
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Affiliation(s)
- Velia S Vizcarra
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, 14642, USA
| | - Ryann M Fame
- Department of Neurosurgery, Stanford University School of Medicine, Stanford, CA, 94305, USA
| | - Lauren M Hablitz
- Center for Translational Neuromedicine, University of Rochester Medical Center, Rochester, NY, 14642, USA
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8
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Chen Y, He X, Cai J, Li Q. Functional aspects of the brain lymphatic drainage system in aging and neurodegenerative diseases. J Biomed Res 2024; 38:206-221. [PMID: 38430054 PMCID: PMC11144931 DOI: 10.7555/jbr.37.20230264] [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: 10/31/2023] [Revised: 12/30/2023] [Accepted: 02/29/2024] [Indexed: 03/03/2024] Open
Abstract
The phenomenon of an aging population is advancing at a precipitous rate. Alzheimer's disease (AD) and Parkinson's disease (PD) are two of the most common age-associated neurodegenerative diseases, both of which are primarily characterized by the accumulation of toxic proteins and the progressive demise of neuronal structures. Recent discoveries about the brain lymphatic drainage system have precipitated a growing body of investigations substantiating its novel roles, including the clearance of macromolecular waste and the trafficking of immune cells. Notably, aquaporin 4-mediated glymphatic transport, crucial for maintaining neural homeostasis, becomes disrupted during the aging process and is further compromised in the pathogenesis of AD and PD. Functional meningeal lymphatic vessels, which facilitate the drainage of cerebrospinal fluid into the deep cervical lymph nodes, are integral in bridging the central nervous system with peripheral immune responses. Dysfunction in these meningeal lymphatic vessels exacerbates pathological trajectory of the age-related neurodegenerative disease. This review explores modulatory influence of the glymphatic system and meningeal lymphatic vessels on the aging brain and its associated neurodegenerative disorders. It also encapsulates the insights of potential mechanisms and prospects of the targeted non-pharmacological interventions.
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Affiliation(s)
- Yan Chen
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, Jiangsu 211166, China
- Shandong Institute of Brain Science and Brain-inspired Research, Shandong First Medical University & Shandong Academy of Medical Sciences, Jinan, Shandong 250117, China
| | - Xiaoxin He
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, Jiangsu 211166, China
- Center for Global Health, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Jiachen Cai
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, Jiangsu 211166, China
- Center for Global Health, Nanjing Medical University, Nanjing, Jiangsu 211166, China
| | - Qian Li
- Jiangsu Key Laboratory of Neurodegeneration, Nanjing Medical University, Nanjing, Jiangsu 211166, China
- Center for Global Health, Nanjing Medical University, Nanjing, Jiangsu 211166, China
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Xie J, Li H, Su S, Cheng J, Cai Q, Tan H, Zu L, Qu X, Han H. Quantitative analysis of molecular transport in the extracellular space using physics-informed neural network. Comput Biol Med 2024; 171:108133. [PMID: 38364661 DOI: 10.1016/j.compbiomed.2024.108133] [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: 01/23/2024] [Revised: 02/06/2024] [Accepted: 02/12/2024] [Indexed: 02/18/2024]
Abstract
The brain extracellular space (ECS), an irregular, extremely tortuous nanoscale space located between cells or between cells and blood vessels, is crucial for nerve cell survival. It plays a pivotal role in high-level brain functions such as memory, emotion, and sensation. However, the specific form of molecular transport within the ECS remain elusive. To address this challenge, this paper proposes a novel approach to quantitatively analyze the molecular transport within the ECS by solving an inverse problem derived from the advection-diffusion equation (ADE) using a physics-informed neural network (PINN). PINN provides a streamlined solution to the ADE without the need for intricate mathematical formulations or grid settings. Additionally, the optimization of PINN facilitates the automatic computation of the diffusion coefficient governing long-term molecule transport and the velocity of molecules driven by advection. Consequently, the proposed method allows for the quantitative analysis and identification of the specific pattern of molecular transport within the ECS through the calculation of the Péclet number. Experimental validation on two datasets of magnetic resonance images (MRIs) captured at different time points showcases the effectiveness of the proposed method. Notably, our simulations reveal identical molecular transport patterns between datasets representing rats with tracer injected into the same brain region. These findings highlight the potential of PINN as a promising tool for comprehensively exploring molecular transport within the ECS.
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Affiliation(s)
- Jiayi Xie
- Department of Automation, Tsinghua University, Beijing 100084, China; Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China
| | - Hongfeng Li
- Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China
| | - Shaoyi Su
- Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China
| | - Jin Cheng
- School of Mathematical Sciences, Fudan University, Shanghai 200433, China
| | - Qingrui Cai
- National Integrated Circuit Industry Education Integration Innovation Platform, School of Electronic Science and Engineering (National Model Microelectronics College), Xiamen University, Xiamen 361102, China; Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen 361102, China
| | - Hanbo Tan
- Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China
| | - Lingyun Zu
- Department of Endocrinology and Metabolism, Department of Cardiology and Institute of Vascular Medicine, Peking University Third Hospital, Beijing 100191, China
| | - Xiaobo Qu
- National Integrated Circuit Industry Education Integration Innovation Platform, School of Electronic Science and Engineering (National Model Microelectronics College), Xiamen University, Xiamen 361102, China; Department of Electronic Science, Fujian Provincial Key Laboratory of Plasma and Magnetic Resonance, Xiamen University, Xiamen 361102, China
| | - Hongbin Han
- Institute of Medical Technology, Peking University Health Science Center, Beijing 100191, China; Department of Radiology, Peking University Third Hospital, Beijing 100191, China; Peking University Third Hospital, Beijing Key Laboratory of Magnetic Resonance Imaging Devices and Technology, Beijing 100191, China; NMPA key Laboratory of Evaluation of Medical Imaging Equipment and Technique, Beijing 100191, China.
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10
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Cohen I, Hoffmann C, Barash Y, Lekach R, Ben-Zeev B, Zohar-Dayan E, Shrot S. Assessment of glymphatic dysfunction in pediatric idiopathic intracranial hypertension: insights from quantitative diffusivity and perivascular spaces analysis-a case-control study. Quant Imaging Med Surg 2024; 14:653-661. [PMID: 38223125 PMCID: PMC10784093 DOI: 10.21037/qims-23-1043] [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: 07/22/2023] [Accepted: 11/21/2023] [Indexed: 01/16/2024]
Abstract
Background The impaired drainage of cerebrospinal fluid through the glymphatic system is thought to play a role in the idiopathic intracranial hypertension (IIH) pathophysiology. Limited data exist regarding the glymphatic system's involvement in pediatric patients with IIH. Therefore, the study's objective was to quantitatively evaluate alterations in parenchymal diffusivity and magnetic resonance imaging (MRI)-visible dilated perivascular spaces (PVS) as imaging indicators of glymphatic dysfunction in pediatric patients with IIH. Methods Patients diagnosed with IIH in 2017-2022 in a single tertiary center (Sheba Medical Center, Israel) were retrospectively reviewed. Twenty-four pediatric patients were enrolled. All patients underwent clinical 3-T brain MRI. The control group included 24 age- and gender-matched healthy subjects with a normal-appearing brain on imaging. We used automatic atlas-based diffusion-weighted imaging analysis to determine regional diffusivity of the thalamus, caudate, putamen, globus pallidus, hippocampus, amygdala, and brain stem. PVS were evaluated using a semi-quantitative rating scale on T2-weighted images. Variables were compared using the Mann-Whitney test. Multivariate analysis of covariance was used to test for differences between controls and IIH patients. Results No significant differences in regional brain diffusivity were observed between individuals with IIH and healthy controls (P=0.14-0.91 for various brain regions). The number of visible PVS was comparable between patients with IIH and the control group across all evaluated sites (P=0.12-0.74 for various brain regions). Conclusions Pediatric IIH patients exhibited similar patterns of parenchymal diffusivity and PVS compared to age-matched controls. These findings do not support the hypothesis that the glymphatic system may play a role in the pathophysiology of pediatric IIH, although previously postulated. However, employing more sophisticated magnetic resonance (MR) techniques could enhance the sensitivity in uncovering underlying glymphatic dysfunction. Further research is warranted to validate and explore this association in larger cohorts and investigate the underlying mechanisms involved in IIH.
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Affiliation(s)
- Israel Cohen
- Department of Diagnostic Imaging, Sheba Medical Center, Tel Hashomer, Israel
- Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Chen Hoffmann
- Department of Diagnostic Imaging, Sheba Medical Center, Tel Hashomer, Israel
- Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Yiftach Barash
- Department of Diagnostic Imaging, Sheba Medical Center, Tel Hashomer, Israel
- Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
| | - Ruth Lekach
- Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
- Department of Nuclear Medicine, Tel-Aviv Sourasky Medical Center, Tel Aviv, Israel
| | - Bruria Ben-Zeev
- Department of Diagnostic Imaging, Sheba Medical Center, Tel Hashomer, Israel
- Pediatric Neurology Unit, Edmond and Lily Safra Children’s Hospital, Sheba Medical Center, Ramat Gan, Israel
| | - Efrat Zohar-Dayan
- Department of Diagnostic Imaging, Sheba Medical Center, Tel Hashomer, Israel
- Pediatric Neurology Unit, Edmond and Lily Safra Children’s Hospital, Sheba Medical Center, Ramat Gan, Israel
| | - Shai Shrot
- Department of Diagnostic Imaging, Sheba Medical Center, Tel Hashomer, Israel
- Faculty of Medicine, Tel Aviv University, Tel Aviv, Israel
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Johnson MJ, Abdelmalik MR, Baidoo FA, Badachhape A, Hughes TJ, Hossain SS. Image-guided subject-specific modeling of glymphatic transport and amyloid deposition. COMPUTER METHODS IN APPLIED MECHANICS AND ENGINEERING 2023; 417:116449. [PMID: 38249440 PMCID: PMC10798618 DOI: 10.1016/j.cma.2023.116449] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 01/23/2024]
Abstract
The glymphatic system is a brain-wide system of perivascular networks that facilitate exchange of cerebrospinal fluid (CSF) and interstitial fluid (ISF) to remove waste products from the brain. A greater understanding of the mechanisms for glymphatic transport may provide insight into how amyloid beta (A β ) and tau agglomerates, key biomarkers for Alzheimer's disease and other neurodegenerative diseases, accumulate and drive disease progression. In this study, we develop an image-guided computational model to describe glymphatic transport and A β deposition throughout the brain. A β transport and deposition are modeled using an advection-diffusion equation coupled with an irreversible amyloid accumulation (damage) model. We use immersed isogeometric analysis, stabilized using the streamline upwind Petrov-Galerkin (SUPG) method, where the transport model is constructed using parameters inferred from brain imaging data resulting in a subject-specific model that accounts for anatomical geometry and heterogeneous material properties. Both short-term (30-min) and long-term (12-month) 3D simulations of soluble amyloid transport within a mouse brain model were constructed from diffusion weighted magnetic resonance imaging (DW-MRI) data. In addition to matching short-term patterns of tracer deposition, we found that transport parameters such as CSF flow velocity play a large role in amyloid plaque deposition. The computational tools developed in this work will facilitate investigation of various hypotheses related to glymphatic transport and fundamentally advance our understanding of its role in neurodegeneration, which is crucial for the development of preventive and therapeutic interventions.
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Affiliation(s)
- Michael J. Johnson
- Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, 201 E. 24th St, Austin, Texas 78712, USA
| | - Michael R.A. Abdelmalik
- Department of Mechanical Engineering, Eindhoven University of Technology, Gemini, Building number 15, Groene Loper, 5612 AE Eindhoven, The Netherlands
| | - Frimpong A. Baidoo
- Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, 201 E. 24th St, Austin, Texas 78712, USA
| | - Andrew Badachhape
- Department of Radiology, Baylor College of Medicine, 701 Fannin Street, Suite 47, Houston, Texas 77030, USA
| | - Thomas J.R. Hughes
- Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, 201 E. 24th St, Austin, Texas 78712, USA
| | - Shaolie S. Hossain
- Oden Institute for Computational Engineering and Sciences, The University of Texas at Austin, 201 E. 24th St, Austin, Texas 78712, USA
- Molecular Cardiology Research Laboratories, The Texas Heart Institute, 6770 Bertner Avenue, Houston, Texas 77030, USA
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12
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Eide PK, Lashkarivand A, Pripp AH, Valnes LM, Hovd M, Ringstad G, Blennow K, Zetterberg H. Mechanisms behind changes of neurodegeneration biomarkers in plasma induced by sleep deprivation. Brain Commun 2023; 5:fcad343. [PMID: 38130841 PMCID: PMC10733810 DOI: 10.1093/braincomms/fcad343] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/13/2023] [Revised: 11/08/2023] [Accepted: 12/11/2023] [Indexed: 12/23/2023] Open
Abstract
Acute sleep deprivation has been shown to affect cerebrospinal fluid and plasma concentrations of biomarkers associated with neurodegeneration, though the mechanistic underpinnings remain unknown. This study compared individuals who, for one night, were either subject to total sleep deprivation or free sleep, (i) examining plasma concentrations of neurodegeneration biomarkers the morning after sleep deprivation or free sleep and (ii) determining how overnight changes in biomarkers plasma concentrations correlate with indices of meningeal lymphatic and glymphatic clearance functions. Plasma concentrations of amyloid-β 40 and 42, phosphorylated tau peptide 181, glial fibrillary acid protein and neurofilament light were measured longitudinally in subjects who from Day 1 to Day 2 either underwent total sleep deprivation (n = 7) or were allowed free sleep (n = 21). The magnetic resonance imaging contrast agent gadobutrol was injected intrathecally, serving as a cerebrospinal fluid tracer. Population pharmacokinetic model parameters of gadobutrol cerebrospinal fluid-to-blood clearance were utilized as a proxy of meningeal lymphatic clearance capacity and intrathecal contrast-enhanced magnetic resonance imaging as a proxy of glymphatic function. After one night of acute sleep deprivation, the plasma concentrations of amyloid-β 40 and 42 were reduced, but not the ratio, and concentrations of the other biomarkers were unchanged. The overnight change in amyloid-β 40 and 42 plasma concentrations in the sleep group correlated significantly with indices of meningeal lymphatic clearance capacity, while this was not seen for the other neurodegeneration biomarkers. However, overnight change in plasma concentrations of amyloid-β 40 and 42 did not correlate with the glymphatic marker. On the other hand, the overnight change in plasma concentration of phosphorylated tau peptide 181 correlated significantly with the marker of glymphatic function in the sleep deprivation group but not in the sleep group. The present data add to the evidence of the role of sleep and sleep deprivation on plasma neurodegeneration concentrations; however, the various neurodegeneration biomarkers respond differently with different mechanisms behind sleep-induced alterations in amyloid-β and tau plasma concentrations. Clearance capacity of meningeal lymphatics seems more important for sleep-induced changes in amyloid-β 40 and 42 plasma concentrations, while glymphatic function seems most important for change in plasma concentration of phosphorylated tau peptide 181 during sleep deprivation. Altogether, the present data highlight diverse mechanisms behind sleep-induced effects on concentrations of plasma neurodegeneration biomarkers.
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Affiliation(s)
- Per Kristian Eide
- Department of Neurosurgery, Oslo University Hospital—Rikshospitalet, N-0424 Oslo, Norway
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, N-0316 Oslo, Norway
| | - Aslan Lashkarivand
- Department of Neurosurgery, Oslo University Hospital—Rikshospitalet, N-0424 Oslo, Norway
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, N-0316 Oslo, Norway
| | - Are Hugo Pripp
- Oslo Centre of Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, N-0424 Oslo, Norway
- Faculty of Health Sciences, Oslo Metropolitan University, N-0130 Oslo, Norway
| | - Lars Magnus Valnes
- Department of Neurosurgery, Oslo University Hospital—Rikshospitalet, N-0424 Oslo, Norway
| | - Markus Hovd
- Section for Pharmacology and Pharmaceutical Biosciences, Department of Pharmacy, University of Oslo, N-0316 Oslo, Norway
- Department of Transplantation Medicine, Oslo University Hospital, N-0424 Oslo, Norway
| | - Geir Ringstad
- Department of Radiology, Oslo University Hospital—Rikshospitalet, N-0424 Oslo, Norway
- Department of Geriatrics and Internal medicine, Sorlandet Hospital, N-4836 Arendal, Norway
| | - Kaj Blennow
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, the Sahlgrenska Academy at the University of Gothenburg, S-405 30 Gothenburg, Sweden
- Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, S-405 30 Gothenburg, Sweden
| | - Henrik Zetterberg
- Department of Psychiatry and Neurochemistry, Institute of Neuroscience and Physiology, the Sahlgrenska Academy at the University of Gothenburg, S-405 30 Gothenburg, Sweden
- Clinical Neurochemistry Laboratory, Sahlgrenska University Hospital, S-405 30 Gothenburg, Sweden
- Department of Neurodegenerative Disease, UCL Institute of Neurology, Queen Square, London WC1E 6BT, UK
- UK Dementia Research Institute at UCL, London WC1E 6BT, UK
- Hong Kong Center for Neurodegenerative Diseases, Clear Water Bay, Hong Kong 999077, China
- Department of Medicine, UW School of Medicine and Public Health, Madison, WI 53726, USA
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13
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Kaur J, Boyd E, Ding G, Zhang L, Luo H, Li Q, Li L, Wei M, Landschoot-Ward J, Chopp M, Zhang Z, Jiang Q. The Association between Glymphatic System and Perivascular Macrophages in Brain Waste Clearance. RESEARCH SQUARE 2023:rs.3.rs-3390074. [PMID: 37886481 PMCID: PMC10602168 DOI: 10.21203/rs.3.rs-3390074/v1] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Subscribe] [Scholar Register] [Indexed: 10/28/2023]
Abstract
The glymphatic system suggests the convective bulk flow of cerebrospinal fluid (CSF) through perivascular spaces and the interstitial spaces of the brain parenchyma for the rapid removal of toxic waste solutes from the brain. However, the presence of convective bulk flow within the brain interstitial spaces is still under debate. We first addressed this argument to determine the involvement of the glymphatic system in brain waste clearance utilizing contrast-enhanced 3D T1-weighted imaging (T1WI), diffusion tensor imaging (DTI), and confocal microscopy imaging. Furthermore, perivascular macrophages (PVMs), which are immune cells located within perivascular spaces, have not been thoroughly explored for their association with the glymphatic system. Therefore, we investigated tracer uptake by PVMs in the perivascular spaces of both the arteries/arterioles and veins/venules and the potential association of PVMs in assisting the glymphatic system for interstitial waste clearance. Our findings demonstrated that both convective bulk flow and diffusion are responsible for the clearance of interstitial waste solutes from the brain parenchyma. Furthermore, our results suggested that PVMs play an important function in glymphatic system-mediated interstitial waste clearance. The glymphatic system and PVMs could be targeted to enhance interstitial waste clearance in patients with waste-associated neurological conditions and aging.
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Affiliation(s)
- Jasleen Kaur
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Physics, Oakland University, Rochester, MI, USA
| | - Edward Boyd
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Radiology, Michigan State University, Lasing, MI, USA
| | - Guangliang Ding
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Radiology, Michigan State University, Lasing, MI, USA
| | - Li Zhang
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Physiology, Michigan State University, Lasing, MI, USA
| | - Hao Luo
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
| | - Qingjiang Li
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
| | - Lian Li
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
| | - Min Wei
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
| | | | - Michael Chopp
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Physics, Oakland University, Rochester, MI, USA
- Department of Physiology, Michigan State University, Lasing, MI, USA
- Department of Neurology, Wayne State University, Detroit, MI, USA
| | - Zhenggang Zhang
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Physiology, Michigan State University, Lasing, MI, USA
- Department of Neurology, Wayne State University, Detroit, MI, USA
| | - Quan Jiang
- Department of Neurology, Henry Ford Health System, Detroit, MI, USA
- Department of Physics, Oakland University, Rochester, MI, USA
- Department of Radiology, Michigan State University, Lasing, MI, USA
- Department of Neurology, Wayne State University, Detroit, MI, USA
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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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15
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Zhu W, Deng S, Jiang H, Zhang J, Li B, Jia Q, Meng Z. Assessment of corticospinal tract remodeling based on diffusion tensor imaging in the treatment of motor dysfunction after ischemic stroke by acupuncture: A meta-analysis. Medicine (Baltimore) 2023; 102:e34618. [PMID: 37565876 PMCID: PMC10419801 DOI: 10.1097/md.0000000000034618] [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: 02/15/2023] [Accepted: 07/14/2023] [Indexed: 08/12/2023] Open
Abstract
BACKGROUND To investigate the efficacy of acupuncture in improving motor dysfunction after ischemic stroke (IS) and to investigate the effect of acupuncture on corticospinal tract (CST) remodeling using diffusion tensor imaging. METHODS Published literature on the effect of acupuncture on CST remodeling after IS using diffusion tensor imaging in the form of randomized controlled trials (RCTs) were systematically retrieved and screened from Cochrane Library, Web of Science, PubMed, Embase, CNKI, CBM, VIP, and Wanfang databases from inception to December 2022. The methodological quality of the included studies was critically and independently evaluated by 2 reviewers using the Cochrane Risk of Bias Assessment Tool for RCTs. The correlated data were extracted using the pre-designed form, and all analyses were performed using Reviewer Manager version 5.4. RESULTS Eleven eligible RCTs involving 459 patients were eventually included. The combined evidence results showed that the acupuncture group significantly improved patients' National Institute of Health stroke scale, Fugl-Meyer Assessment Scale, and Barthel index compared with conventional medical treatment. The acupuncture group significantly promoted remodeling of the CST, as reflected by an increase in fractional anisotropy (FA) throughout the CST [MD = 0.04, 95% CI (0.02, 0.07), P = .001], and in addition, subgroup analysis showed that the acupuncture group significantly improved FA in the infarct area compared with conventional medical treatment at around 4 weeks [MD = 0.04, 95% CI (0.02, 0.06), P = .0002] and FA of the affected cerebral peduncle [MD = 0.03, 95% CI (0.00, 0.07), P = .02]. Also, compared with conventional medical treatment, the acupuncture group significantly increased average diffusion coefficient of the affected cerebral peduncle [MD = -0.21, 95% CI (-0.28, -0.13), P < .00001]. CONCLUSION The results of the meta-analysis suggest that acupuncture therapy can improve the clinical manifestations of motor dysfunction in patients after IS and advance a possibly beneficial effect on CST remodeling. However, due to the number and quality of eligible studies, these findings need to be further validated in more standardized, rigorous, high-quality clinical trials.
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Affiliation(s)
- Weiming Zhu
- First Teaching Hospital of Tianjin University of Traditional Chinese Medicine, Tianjin, China
- National Clinical Research Center for Chinese Medicine Acupuncture and Moxibustion, Tianjin, China
| | - Shizhe Deng
- First Teaching Hospital of Tianjin University of Traditional Chinese Medicine, Tianjin, China
- National Clinical Research Center for Chinese Medicine Acupuncture and Moxibustion, Tianjin, China
| | - Hailun Jiang
- First Teaching Hospital of Tianjin University of Traditional Chinese Medicine, Tianjin, China
- National Clinical Research Center for Chinese Medicine Acupuncture and Moxibustion, Tianjin, China
| | - Jieying Zhang
- First Teaching Hospital of Tianjin University of Traditional Chinese Medicine, Tianjin, China
- National Clinical Research Center for Chinese Medicine Acupuncture and Moxibustion, Tianjin, China
| | - Boxuan Li
- First Teaching Hospital of Tianjin University of Traditional Chinese Medicine, Tianjin, China
- National Clinical Research Center for Chinese Medicine Acupuncture and Moxibustion, Tianjin, China
| | - Qingqing Jia
- The Second Affiliated Hospital of Shandong University of Traditional Chinese Medicine, Jinan, China
| | - Zhihong Meng
- First Teaching Hospital of Tianjin University of Traditional Chinese Medicine, Tianjin, China
- National Clinical Research Center for Chinese Medicine Acupuncture and Moxibustion, Tianjin, China
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16
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Ajeeb R, Clegg JR. Intrathecal delivery of Macromolecules: Clinical status and emerging technologies. Adv Drug Deliv Rev 2023; 199:114949. [PMID: 37286086 DOI: 10.1016/j.addr.2023.114949] [Citation(s) in RCA: 6] [Impact Index Per Article: 6.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/30/2023] [Revised: 05/31/2023] [Accepted: 06/03/2023] [Indexed: 06/09/2023]
Abstract
The proximity and association of cerebrospinal fluid (CSF) and the intrathecal (IT) space with deep targets in the central nervous system (CNS) parenchyma makes IT injection an attractive route of administration for brain drug delivery. However, the extent to which intrathecally administered macromolecules are effective in treating neurological diseases is a question of both clinical debate and technological interest. We present the biological, chemical, and physical properties of the intrathecal space that are relevant to drug absorption, distribution, metabolism, and elimination from CSF. We then analyze the evolution of IT drug delivery in clinical trials over the last 20 years. Our analysis revealed that the percentage of clinical trials assessing IT delivery for the delivery of biologics (i.e., macromolecules, cells) for treatment of chronic conditions (e.g., neurodegeneration, cancer, and metabolic diseases) has steadily increased. Clinical trials exploring cell or macromolecular delivery within the IT space have not evaluated engineering technologies, such as depots, particles, or other delivery systems. Recent pre-clinical studies have evaluated IT macromolecule delivery in small animals, postulating that delivery efficacy can be assisted by external medical devices, micro- or nanoparticles, bulk biomaterials, and viral vectors. Further studies are necessary to evaluate the extent to which engineering technologies and IT administration improve CNS targeting and therapeutic outcome.
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Affiliation(s)
- Rana Ajeeb
- Stephenson School of Biomedical Engineering, The University of Oklahoma, Norman, OK, United States
| | - John R Clegg
- Stephenson School of Biomedical Engineering, The University of Oklahoma, Norman, OK, United States; Stephenson Cancer Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States; Harold Hamm Diabetes Center, University of Oklahoma Health Sciences Center, Oklahoma City, OK, United States; Institute for Biomedical Engineering, Science, and Technology, University of Oklahoma, Norman, OK, United States.
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17
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Gao Y, Liu K, Zhu J. Glymphatic system: an emerging therapeutic approach for neurological disorders. Front Mol Neurosci 2023; 16:1138769. [PMID: 37485040 PMCID: PMC10359151 DOI: 10.3389/fnmol.2023.1138769] [Citation(s) in RCA: 7] [Impact Index Per Article: 7.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/06/2023] [Accepted: 06/21/2023] [Indexed: 07/25/2023] Open
Abstract
The functions of the glymphatic system include clearance of the metabolic waste and modulation of the water transport in the brain, and it forms a brain-wide fluid network along with cerebrospinal fluid (CSF) and interstitial fluid (ISF). The glymphatic pathway consists of periarterial influx of CSF, astrocyte-mediated interchange between ISF and CSF supported by aquaporin-4 (AQP4) on the endfeet of astrocyte around the periarterioles, and perivenous efflux of CSF. Finally, CSF is absorbed by the arachnoid granules or flows into the cervical lymphatic vessels. There is growing evidence from animal experiments that the glymphatic system dysfunction is involved in many neurological disorders, such as Alzheimer's disease, stroke, epilepsy, traumatic brain injury and meningitis. In this review, we summarize the latest progress on the glymphatic system and its driving factors, as well as changes in the glymphatic pathway in different neurological diseases. We significantly highlight the likely therapeutic approaches for glymphatic pathway in neurological diseases, and the importance of AQP4 and normal sleep architecture in this process.
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Affiliation(s)
- Ying Gao
- Department of Neurology, Neuroscience Centre, The First Hospital of Jilin University, Changchun, China
| | - Kangding Liu
- Department of Neurology, Neuroscience Centre, The First Hospital of Jilin University, Changchun, China
| | - Jie Zhu
- Department of Neurology, Neuroscience Centre, The First Hospital of Jilin University, Changchun, China
- Department of Neurobiology, Care Sciences and Society, Karolinska Institute, Karolinska University Hospital, Solna, Sweden
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18
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Poulain A, Riseth J, Vinje V. Multi-compartmental model of glymphatic clearance of solutes in brain tissue. PLoS One 2023; 18:e0280501. [PMID: 36881576 PMCID: PMC9990927 DOI: 10.1371/journal.pone.0280501] [Citation(s) in RCA: 0] [Impact Index Per Article: 0] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/30/2022] [Accepted: 01/02/2023] [Indexed: 03/08/2023] Open
Abstract
The glymphatic system is the subject of numerous pieces of research in biology. Mathematical modelling plays a considerable role in this field since it can indicate the possible physical effects of this system and validate the biologists' hypotheses. The available mathematical models that describe the system at the scale of the brain (i.e. the macroscopic scale) are often solely based on the diffusion equation and do not consider the fine structures formed by the perivascular spaces. We therefore propose a mathematical model representing the time and space evolution of a mixture flowing through multiple compartments of the brain. We adopt a macroscopic point of view in which the compartments are all present at any point in space. The equations system is composed of two coupled equations for each compartment: One equation for the pressure of a fluid and one for the mass concentration of a solute. The fluid and solute can move from one compartment to another according to certain membrane conditions modelled by transfer functions. We propose to apply this new modelling framework to the clearance of 14C-inulin from the rat brain.
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Affiliation(s)
- Alexandre Poulain
- Laboratoire Paul Painlevé, UMR 8524 CNRS, Université de Lille, Lille, France
- Department for Numerical Analysis and Scientific Computing, Simula Research Laboratory, Oslo, Norway
| | - Jørgen Riseth
- Department of Mathematics, University of Oslo, Oslo, Norway
- Department for Numerical Analysis and Scientific Computing, Simula Research Laboratory, Oslo, Norway
| | - Vegard Vinje
- Department for Numerical Analysis and Scientific Computing, Simula Research Laboratory, Oslo, Norway
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19
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Bah TM, Siler DA, Ibrahim AH, Cetas JS, Alkayed NJ. Fluid dynamics in aging-related dementias. Neurobiol Dis 2023; 177:105986. [PMID: 36603747 DOI: 10.1016/j.nbd.2022.105986] [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: 10/31/2022] [Revised: 12/22/2022] [Accepted: 12/31/2022] [Indexed: 01/03/2023] Open
Abstract
Recent human and animal model experimental studies revealed novel pathways for fluid movement, immune cell trafficking and metabolic waste clearance in CNS. These studies raise the intriguing possibility that the newly discovered pathways, including the glymphatic system, lymphatic meningeal vessels and skull-brain communication channels, are impaired in aging and neurovascular and neurodegenerative diseases associated with dementia, including Alzheimer's disease (AD) and AD-related dementia. We provide an overview of the glymphatic and dural meningeal lymphatic systems, review current methods and approaches used to study glymphatic flow in humans and animals, and discuss current evidence and controversies related to its role in CNS flow homeostasis under physiological and pathophysiological conditions. Non-invasive imaging approaches are needed to fully understand the mechanisms and pathways driving fluid movement in CNS and their roles across lifespan including healthy aging and aging-related dementia.
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Affiliation(s)
- Thierno M Bah
- Department of Anesthesiology and Perioperative Medicine, Oregon Health & Science University, Portland, OR, USA
| | - Dominic A Siler
- Department of Neurological Surgery, Oregon Health & Science University, Portland, OR, USA
| | - Aseel H Ibrahim
- Department of Neurosurgery, University of Arizona, Tucson, AZ, USA
| | - Justin S Cetas
- Department of Neurosurgery, University of Arizona, Tucson, AZ, USA
| | - Nabil J Alkayed
- Department of Anesthesiology and Perioperative Medicine, Oregon Health & Science University, Portland, OR, USA; Knight Cardiovascular Institute, Oregon Health & Science University, Portland, OR, USA.
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20
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Mathematical Optimisation of Magnetic Nanoparticle Diffusion in the Brain White Matter. Int J Mol Sci 2023; 24:ijms24032534. [PMID: 36768857 PMCID: PMC9917052 DOI: 10.3390/ijms24032534] [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: 11/22/2022] [Revised: 01/20/2023] [Accepted: 01/26/2023] [Indexed: 01/31/2023] Open
Abstract
Magnetic nanoparticles (MNPs) are a promising drug delivery system to treat brain diseases, as the particle transport trajectory can be manipulated by an external magnetic field. However, due to the complex microstructure of brain tissues, particularly the arrangement of nerve fibres in the white matter (WM), how to achieve desired drug distribution patterns, e.g., uniform distribution, is largely unknown. In this study, by adopting a mathematical model capable of capturing the diffusion trajectories of MNPs, we conducted a pilot study to investigate the effects of key parameters in the MNP delivery on the particle diffusion behaviours in the brain WM microstructures. The results show that (i) a uniform distribution of MNPs can be achieved in anisotropic tissues by adjusting the particle size and magnetic field; (ii) particle size plays a key role in determining MNPs' diffusion behaviours. The magnitude of MNP equivalent diffusivity is reversely correlated to the particle size. The MNPs with a dimension greater than 90 nm cannot reach a uniform distribution in the brain WM even in an external magnitude field; (iii) axon tortuosity may lead to transversely anisotropic MNP transport in the brain WM; however, this effect can be mitigated by applying an external magnetic field perpendicular to the local axon track. This study not only advances understanding to answer the question of how to optimise MNP delivery, but also demonstrates the potential of mathematical modelling to help achieve desired drug distributions in biological tissues with a complex microstructure.
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21
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Could dexmedetomidine be repurposed as a glymphatic enhancer? Trends Pharmacol Sci 2022; 43:1030-1040. [PMID: 36280451 DOI: 10.1016/j.tips.2022.09.007] [Citation(s) in RCA: 8] [Impact Index Per Article: 4.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/13/2022] [Revised: 09/26/2022] [Accepted: 09/26/2022] [Indexed: 11/06/2022]
Abstract
Cerebrospinal fluid (CSF) flows through the central nervous system (CNS) via the glymphatic pathway to clear the interstitium of metabolic waste. In preclinical studies, glymphatic fluid flow rate increases with low central noradrenergic tone and slow-wave activity during natural sleep and general anesthesia. By contrast, sleep deprivation reduces glymphatic clearance and leads to intracerebral accumulation of metabolic waste, suggesting an underlying mechanism linking sleep disturbances with neurodegenerative diseases. The selective α2-adrenergic agonist dexmedetomidine is a sedative drug that induces slow waves in the electroencephalogram, suppresses central noradrenergic tone, and preserves glymphatic outflow. As recently developed dexmedetomidine formulations enable self-administration, we suggest that dexmedetomidine could serve as a sedative-hypnotic drug to enhance clearance of harmful waste from the brain of those vulnerable to neurodegeneration.
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22
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Bohr T, Hjorth PG, Holst SC, Hrabětová S, Kiviniemi V, Lilius T, Lundgaard I, Mardal KA, Martens EA, Mori Y, Nägerl UV, Nicholson C, Tannenbaum A, Thomas JH, Tithof J, Benveniste H, Iliff JJ, Kelley DH, Nedergaard M. The glymphatic system: Current understanding and modeling. iScience 2022; 25:104987. [PMID: 36093063 PMCID: PMC9460186 DOI: 10.1016/j.isci.2022.104987] [Citation(s) in RCA: 94] [Impact Index Per Article: 47.0] [Reference Citation Analysis] [Abstract] [Key Words] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Indexed: 02/04/2023] Open
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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Affiliation(s)
- Tomas Bohr
- Department of Physics, Technical University of Denmark, 2800 Kgs. Lyngby, Denmark
| | - Poul G. Hjorth
- Department of Applied Mathematics and Computer Science, Technical University of Denmark, Richard Petersens Plads, 2800 Kgs. Lyngby, Denmark
| | - Sebastian C. Holst
- Neuroscience and Rare Diseases Discovery and Translational Area, Roche Pharmaceutical Research and Early Development, Roche Innovation Center Basel, Grenzacherstrasse 124, 4070 Basel, Switzerland
| | - Sabina Hrabětová
- Department of Cell Biology and The Robert Furchgott Center for Neural and Behavioral Science, State University of New York Downstate Medical Center, Brooklyn, NY, USA
| | - Vesa Kiviniemi
- Oulu Functional NeuroImaging, Department of Diagnostic Radiology, MRC, Oulu University Hospital, Oulu, Finland
- Medical Imaging, Physics and Technology, the Faculty of Medicine, University of Oulu, Oulu, Finland
| | - Tuomas Lilius
- Department of Pharmacology, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Individualized Drug Therapy Research Program, Faculty of Medicine, University of Helsinki, Helsinki, Finland
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
- Department of Emergency Medicine and Services, Helsinki University Hospital and University of Helsinki, Helsinki, Finland
| | - Iben Lundgaard
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Kent-Andre Mardal
- Department of Mathematics, University of Oslo, Oslo, Norway
- Simula Research Laboratory, Department of Numerical Analysis and Scientific Computing, Oslo, Norway
| | | | - Yuki Mori
- Center for Translational Neuromedicine, Faculty of Health and Medical Sciences, University of Copenhagen, Copenhagen, Denmark
| | - U. Valentin Nägerl
- Instítut Interdisciplinaire de Neurosciences, Université de Bordeaux / CNRS UMR 5297, Centre Broca Nouvelle-Aquitaine, 146 rue Léo Saignat, CS 61292 Case 130, 33076 Bordeaux Cedex France
| | - Charles Nicholson
- Department of Neuroscience and Physiology, New York University Grossman School of Medicine, New York, NY, USA
- Department of Cell Biology, SUNY Downstate Health Sciences University, Brooklyn, NY, USA
| | - Allen Tannenbaum
- Departments of Computer Science/ Applied Mathematics and Statistics, Stony Brook University, Stony Brook, NY, USA
| | - John H. Thomas
- Department of Mechanical Engineering, University of Rochester, Rochester, 14627 NY, USA
| | - Jeffrey Tithof
- Department of Mechanical Engineering, University of Minnesota, Minneapolis, USA
| | - Helene Benveniste
- Department of Anesthesiology, Yale School of Medicine, New Haven, CT, USA
- Department of Biomedical Engineering, Yale School of Medicine, New Haven, CT, USA
| | - Jeffrey J. Iliff
- VISN 20 Mental Illness Research, Education and Clinical Center, VA Puget Sound Health Care System, Seattle, WA, USA
- Department of Psychiatry and Behavioral Sciences, University of Washington School of Medicine, Seattle, WA, USA
- Department of Neurology, University of Washington School of Medicine, Seattle, WA, USA
| | - Douglas H. Kelley
- Department of Mechanical Engineering, University of Rochester, Rochester, 14627 NY, USA
| | - 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, 14642 NY, USA
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23
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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: 6] [Impact Index Per Article: 3.0] [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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24
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Hornkjøl M, Valnes LM, Ringstad G, Rognes ME, Eide PK, Mardal KA, Vinje V. CSF circulation and dispersion yield rapid clearance from intracranial compartments. Front Bioeng Biotechnol 2022; 10:932469. [PMID: 36172015 PMCID: PMC9510842 DOI: 10.3389/fbioe.2022.932469] [Citation(s) in RCA: 4] [Impact Index Per Article: 2.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/14/2022] [Accepted: 08/17/2022] [Indexed: 11/13/2022] Open
Abstract
In this paper, we used a computational model to estimate the clearance of a tracer driven by the circulation of cerebrospinal fluid (CSF) produced in the choroid plexus (CP) located within the lateral ventricles. CSF was assumed to exit the subarachnoid space (SAS) via different outflow routes such as the parasagittal dura, cribriform plate, and/or meningeal lymphatics. We also modelled a reverse case where fluid was produced within the spinal canal and absorbed in the choroid plexus in line with observations on certain iNPH patients. No directional interstitial fluid flow was assumed within the brain parenchyma. Tracers were injected into the foramen magnum. The models demonstrate that convection in the subarachnoid space yields rapid clearance from both the SAS and the brain interstitial fluid and can speed up intracranial clearance from years, as would be the case for purely diffusive transport, to days.
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Affiliation(s)
- Martin Hornkjøl
- Department of Mathematics, University of Oslo, Blindern, Norway
- *Correspondence: Martin Hornkjøl,
| | - Lars Magnus Valnes
- Department of Neurosurgery, Oslo University Hospital–Rikshospitalet, Oslo, Norway
| | - Geir Ringstad
- Department of Radiology, Oslo University Hospital, Oslo, Norway
- Department of Geriatrics and Internal Medicine, Sorlandet Hospital, Arendal, Norway
| | - Marie E. Rognes
- Department of Numerical Analysis and Scientific Computing, Simula Research Laboratory, Oslo, Norway
- Department of Mathematics, University of Bergen, Bergen, Norway
| | - Per-Kristian Eide
- Department of Neurosurgery, Oslo University Hospital–Rikshospitalet, Oslo, Norway
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Kent-André Mardal
- Department of Mathematics, University of Oslo, Blindern, Norway
- Department of Numerical Analysis and Scientific Computing, Simula Research Laboratory, Oslo, Norway
| | - Vegard Vinje
- Department of Numerical Analysis and Scientific Computing, Simula Research Laboratory, Oslo, Norway
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25
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Eide PK, Pripp AH, Berge B, Hrubos-Strøm H, Ringstad G, Valnes LM. Altered glymphatic enhancement of cerebrospinal fluid tracer in individuals with chronic poor sleep quality. J Cereb Blood Flow Metab 2022; 42:1676-1692. [PMID: 35350917 PMCID: PMC9441729 DOI: 10.1177/0271678x221090747] [Citation(s) in RCA: 27] [Impact Index Per Article: 13.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Indexed: 12/20/2022]
Abstract
Chronic sleep disturbance is a risk factor for dementia disease, possibly due to impaired sleep-dependent clearance of toxic metabolic by-products. We compared enrichment of a cerebrospinal fluid (CSF) tracer within brain of patients reporting good or poor sleep quality, assessed by the Pittsburgh Sleep Quality Index (PSQI) questionnaire. Tracer enrichment in a selection of brain regions was assessed using multiphase magnetic resonance imaging up to 48 hours after intrathecal administration of the contrast agent gadobutrol (0.5 ml of 1 mmol/ml) serving as tracer. Tracer enrichment differed between patients with good (PSQI ≤5) and poor (PSQI >5) sleep quality in a cohort of non-dementia individuals (n = 44; age 42.3 ± 14.5 years), and in patients with the dementia subtype idiopathic normal pressure hydrocephalus (n = 24; age 71.0 ± 4.9 years). Sleep impairment was associated with increased CSF tracer enrichment in several brain regions. Cortical brain volume as well as entorhinal cortex thickness was reduced in the oldest cohort and was correlated with the severity of sleep disturbance and the degree of cortical tracer enrichment. We suggest chronic sleep disturbance is accompanied by altered glymphatic function along enlarged perivascular spaces.
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Affiliation(s)
- Per Kristian Eide
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Neurosurgery, Oslo University Hospital - Rikshospitalet, Oslo, Norway
| | - Are Hugo Pripp
- Oslo Centre of Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, Oslo, Norway.,Faculty of Health Sciences, Oslo Metropolitan University, Oslo, Norway
| | | | - Harald Hrubos-Strøm
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Otorhinolaryngology, Surgical Division, Akershus University Hospital, Nordbyhagen, Norway
| | - Geir Ringstad
- Department of Radiology, Oslo University Hospital-Rikshospitalet, Oslo, Norway
| | - Lars Magnus Valnes
- Department of Neurosurgery, Oslo University Hospital - Rikshospitalet, Oslo, Norway
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26
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The glymphatic system: implications for drugs for central nervous system diseases. Nat Rev Drug Discov 2022; 21:763-779. [PMID: 35948785 DOI: 10.1038/s41573-022-00500-9] [Citation(s) in RCA: 38] [Impact Index Per Article: 19.0] [Reference Citation Analysis] [Abstract] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Accepted: 05/22/2022] [Indexed: 12/14/2022]
Abstract
In the past decade, evidence for a fluid clearance pathway in the central nervous system known as the glymphatic system has grown. According to the glymphatic system concept, cerebrospinal fluid flows directionally through the brain and non-selectively clears the interstitium of metabolic waste. Importantly, the glymphatic system may be modulated by particular drugs such as anaesthetics, as well as by non-pharmacological factors such as sleep, and its dysfunction has been implicated in central nervous system disorders such as Alzheimer disease. Although the glymphatic system is best described in rodents, reports using multiple neuroimaging modalities indicate that a similar transport system exists in the human brain. Here, we overview the evidence for the glymphatic system and its role in disease and discuss opportunities to harness the glymphatic system therapeutically; for example, by improving the effectiveness of intrathecally delivered drugs.
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27
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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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28
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Lee MK, Cho SJ, Bae YJ, Kim JM. MRI-Based Demonstration of the Normal Glymphatic System in a Human Population: A Systematic Review. Front Neurol 2022; 13:827398. [PMID: 35693018 PMCID: PMC9174517 DOI: 10.3389/fneur.2022.827398] [Citation(s) in RCA: 11] [Impact Index Per Article: 5.5] [Reference Citation Analysis] [Abstract] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/02/2021] [Accepted: 04/27/2022] [Indexed: 11/23/2022] Open
Abstract
Background The glymphatic system has been described as one that facilitates the exchange between the cerebrospinal fluid (CSF) and interstitial fluid, and many recent studies have demonstrated glymphatic flow based on magnetic resonance imaging (MRI). We aim to systematically review the studies demonstrating a normal glymphatic flow in a human population using MRI and to propose a detailed glymphatic imaging protocol. Methods We searched the MEDLINE and EMBASE databases to identify studies with human participants involving MRI-based demonstrations of the normal glymphatic flow. We extracted data on the imaging sequence, imaging protocol, and the targeted anatomical structures on each study. Results According to contrast-enhanced MRI studies, peak enhancement was sequentially detected first in the CSF space, followed by the brain parenchyma, the meningeal lymphatic vessel (MLV), and, finally, the cervical lymph nodes, corresponding with glymphatic flow and explaining the drainage into the MLV. Non-contrast flow-sensitive MRI studies revealed similar glymphatic inflow from the CSF space to the brain parenchyma and efflux of exchanged fluid from the brain parenchyma to the MLV. Conclusion We may recommend T1-weighted contrast-enhanced MRI for visualizing glymphatic flow. Our result can increase understanding of the glymphatic system and may lay the groundwork for establishing central nervous system fluid dynamic theories and developing standardized imaging protocols.
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Affiliation(s)
- Min Kyoung Lee
- Department of Radiology, College of Medicine, Yeouido St. Mary's Hospital, The Catholic University of Korea, Soeul, South Korea
| | - Se Jin Cho
- Department of Radiology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, South Korea
| | - Yun Jung Bae
- Department of Radiology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, South Korea
- *Correspondence: Yun Jung Bae
| | - Jong-Min Kim
- Department of Neurology, Seoul National University Bundang Hospital, Seoul National University College of Medicine, Seongnam, South Korea
- Jong-Min Kim
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29
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Juhler M, Hansen TS, Novrup HVG, MacAulay N, Munch TN. Hydrocephalus Study Design: Testing New Hypotheses in Clinical Studies and Bench-to-Bedside Research. World Neurosurg 2022; 161:424-431. [PMID: 35505563 DOI: 10.1016/j.wneu.2021.12.100] [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: 09/13/2021] [Revised: 12/23/2021] [Accepted: 12/24/2021] [Indexed: 10/18/2022]
Abstract
In this article, we aimed to describe some of the currently most challenging problems in neurosurgical management of hydrocephalus and how these can be reasons for inspiration for and development of research. We chose 4 areas of focus: 2 dedicated to improvement of current treatments (shunt implant surgery and endoscopic hydrocephalus surgery) and 2 dedicated to emerging future treatment principles (molecular mechanisms of cerebrospinal fluid secretion and hydrocephalus genetics).
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Affiliation(s)
- Marianne Juhler
- Department of Neurosurgery, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark; Department of Neurosurgery, Aarhus University Hospital, Aarhus, Denmark; Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark.
| | | | - Hans V G Novrup
- Department of Neurosurgery, Aarhus University Hospital, Aarhus, Denmark
| | - Nanna MacAulay
- Department of Neuroscience, University of Copenhagen, Copenhagen, Denmark
| | - Tina Nørgaard Munch
- Department of Neurosurgery, Copenhagen University Hospital, Rigshospitalet, Copenhagen, Denmark; Department of Clinical Medicine, University of Copenhagen, Copenhagen, Denmark; Department of Epidemiology Research, Statens Serum Institut, Copenhagen, Denmark
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30
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Eide PK, Lashkarivand A, Hagen-Kersten ÅA, Gjertsen Ø, Nedregaard B, Sletteberg R, Løvland G, Vatnehol SAS, Pripp AH, Valnes LM, Ringstad G. Intrathecal Contrast-Enhanced Magnetic Resonance Imaging of Cerebrospinal Fluid Dynamics and Glymphatic Enhancement in Idiopathic Normal Pressure Hydrocephalus. Front Neurol 2022; 13:857328. [PMID: 35463139 PMCID: PMC9019061 DOI: 10.3389/fneur.2022.857328] [Citation(s) in RCA: 10] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 01/18/2022] [Accepted: 03/10/2022] [Indexed: 01/09/2023] Open
Abstract
Idiopathic normal pressure hydrocephalus (iNPH) is a neurodegenerative disease, characterized by cerebrospinal fluid (CSF) flow disturbance. Today, the only available treatment is CSF diversion surgery (shunt surgery). While traditional imaging biomarkers typically assess CSF space anatomy, recently introduced imaging biomarkers of CSF dynamics and glymphatic enhancement, provide imaging of CSF dynamics and thereby more specifically reveal elements of the underlying pathophysiology. The biomarkers address CSF ventricular reflux grade as well as glymphatic enhancement and derive from intrathecal contrast-enhanced MRI. However, the contrast agent serving as CSF tracer is administered off-label. In medicine, the introduction of new diagnostic or therapeutic methods must consider the balance between risk and benefit. To this end, we performed a prospective observational study of 95 patients with iNPH, comparing different intrathecal doses of the MRI contrast agent gadobutrol (0.10, 0.25, and 0.50 mmol, respectively), aiming at the lowest reasonable dose needed to retrieve diagnostic information about the novel MRI biomarkers. The present observations disclosed a dose-dependent enrichment of subarachnoid CSF spaces (cisterna magna, vertex, and velum interpositum) with dose-dependent ventricular reflux of tracer in iNPH, as well as dose-dependent glymphatic tracer enrichment. The association between tracer enrichment in CSF and parenchymal compartments were as well dose-related. Intrathecal gadobutrol in a dose of 0.25 mmol, but not 0.10 mmol, was at 1.5T MRI considered sufficient for imaging altered CSF dynamics and glymphatic enhancement in iNPH, even though 3T MRI provided better sensitivity. Tracer enrichment in CSF at the vertex and within the cerebral cortex and subcortical white matter was deemed too low for maintaining diagnostic information from a dose of 0.10 mmol. We conclude that reducing the intrathecal dose of gadobutrol from 0.50 to 0.25 mmol gadobutrol improves the safety margin while maintaining the necessary diagnostic information about disturbed CSF homeostasis and glymphatic failure in iNPH.
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Affiliation(s)
- Per Kristian Eide
- Department of Neurosurgery, Oslo University Hospital-Rikshospitalet, Oslo, Norway.,Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Aslan Lashkarivand
- Department of Neurosurgery, Oslo University Hospital-Rikshospitalet, Oslo, Norway.,Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | | | - Øivind Gjertsen
- Department of Radiology, Oslo University Hospital-Rikshospitalet, Oslo, Norway
| | - Bård Nedregaard
- Department of Radiology, Oslo University Hospital-Rikshospitalet, Oslo, Norway
| | - Ruth Sletteberg
- Department of Radiology, Oslo University Hospital-Rikshospitalet, Oslo, Norway
| | - Grethe Løvland
- The Intervention Centre, Oslo University Hospital-Rikshospitalet, Oslo, Norway
| | - Svein Are Sirirud Vatnehol
- The Intervention Centre, Oslo University Hospital-Rikshospitalet, Oslo, Norway.,Institute of Optometry Radiography and Lighting Design, Faculty of Health and Social Sciences, University of South Eastern Norway, Drammen, Norway
| | - Are Hugo Pripp
- Oslo Centre of Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, Oslo, Norway.,Faculty of Health Sciences, Oslo Metropolitan University, Oslo, Norway
| | - Lars Magnus Valnes
- Department of Neurosurgery, Oslo University Hospital-Rikshospitalet, Oslo, Norway
| | - Geir Ringstad
- Department of Radiology, Oslo University Hospital-Rikshospitalet, Oslo, Norway.,Department of Geriatrics and Internal Medicine, Sorlandet Hospital, Arendal, Norway
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31
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Töger J, Andersen M, Haglund O, Kylkilahti TM, Lundgaard I, Markenroth Bloch K. Real‐time imaging of respiratory effects on cerebrospinal fluid flow in small diameter passageways. Magn Reson Med 2022; 88:770-786. [PMID: 35403247 PMCID: PMC9324219 DOI: 10.1002/mrm.29248] [Citation(s) in RCA: 3] [Impact Index Per Article: 1.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 08/05/2021] [Revised: 03/01/2022] [Accepted: 03/08/2022] [Indexed: 12/03/2022]
Abstract
Purpose Respiration‐related CSF flow through the cerebral aqueduct may be useful for elucidating physiology and pathophysiology of the glymphatic system, which has been proposed as a mechanism of brain waste clearance. Therefore, we aimed to (1) develop a real‐time (CSF) flow imaging method with high spatial and sufficient temporal resolution to capture respiratory effects, (2) validate the method in a phantom setup and numerical simulations, and (3) apply the method in vivo and quantify its repeatability and correlation with different respiratory conditions. Methods A golden‐angle radial flow sequence (reconstructed temporal resolution 168 ms, spatial resolution 0.6 mm) was implemented on a 7T MRI scanner and reconstructed using compressed sensing. A phantom setup mimicked simultaneous cardiac and respiratory flow oscillations. The effect of temporal resolution and vessel diameter was investigated numerically. Healthy volunteers (n = 10) were scanned at four different respiratory conditions, including repeat scans. Results Phantom data show that the developed sequence accurately quantifies respiratory oscillations (ratio real‐time/reference QR = 0.96 ± 0.02), but underestimates the rapid cardiac oscillations (ratio QC = 0.46 ± 0.14). Simulations suggest that QC can be improved by increasing temporal resolution. In vivo repeatability was moderate to very strong for cranial and caudal flow (intraclass correlation coefficient range: 0.55–0.99) and weak to strong for net flow (intraclass correlation coefficient range: 0.48–0.90). Net flow was influenced by respiratory condition (p < 0.01). Conclusions The presented real‐time flow MRI method can quantify respiratory‐related variations of CSF flow in the cerebral aqueduct, but it underestimates rapid cardiac oscillations. In vivo, the method showed good repeatability and a relationship between flow and respiration.
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Affiliation(s)
- Johannes Töger
- Department of Clinical Sciences Lund, Diagnostic Radiology Lund University, Skåne University Hospital Lund Sweden
| | - Mads Andersen
- Philips Healthcare Copenhagen Denmark
- Lund University, Lund University Bioimaging Center Lund Sweden
| | - Olle Haglund
- Department of Medical Radiation Physics Lund University Lund Sweden
| | - Tekla Maria Kylkilahti
- Department of Experimental Medical Science Lund University Lund Sweden
- Wallenberg Centre for Molecular Medicine Lund University Lund Sweden
| | - Iben Lundgaard
- Department of Experimental Medical Science Lund University Lund Sweden
- Wallenberg Centre for Molecular Medicine Lund University Lund Sweden
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32
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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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33
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Yuan T, Gao L, Zhan W, Dini D. Effect of Particle Size and Surface Charge on Nanoparticles Diffusion in the Brain White Matter. Pharm Res 2022; 39:767-781. [PMID: 35314997 PMCID: PMC9090877 DOI: 10.1007/s11095-022-03222-0] [Citation(s) in RCA: 19] [Impact Index Per Article: 9.5] [Reference Citation Analysis] [Abstract] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 11/04/2021] [Accepted: 03/02/2022] [Indexed: 11/27/2022]
Abstract
Purpose Brain disorders have become a serious problem for healthcare worldwide. Nanoparticle-based drugs are one of the emerging therapies and have shown great promise to treat brain diseases. Modifications on particle size and surface charge are two efficient ways to increase the transport efficiency of nanoparticles through brain-blood barrier; however, partly due to the high complexity of brain microstructure and limited visibility of Nanoparticles (NPs), our understanding of how these two modifications can affect the transport of NPs in the brain is insufficient. Methods In this study, a framework, which contains a stochastic geometric model of brain white matter (WM) and a mathematical particle tracing model, was developed to investigate the relationship between particle size/surface charge of the NPs and their effective diffusion coefficients (D) in WM. Results The predictive capabilities of this method have been validated using published experimental tests. For negatively charged NPs, both particle size and surface charge are positively correlated with D before reaching a size threshold. When Zeta potential (Zp) is less negative than -10 mV, the difference between NPs’ D in WM and pure interstitial fluid (IF) is limited. Conclusion A deeper understanding on the relationships between particle size/surface charge of NPs and their D in WM has been obtained. The results from this study and the developed modelling framework provide important tools for the development of nano-drugs and nano-carriers to cure brain diseases.
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Affiliation(s)
- Tian Yuan
- Department of Mechanical Engineering, Imperial College London, London, SW7 2AZ, UK.
| | - Ling Gao
- School of Biomedical Engineering and Imaging Sciences, King's College London, St. Thomas Hospital, London, SE1 7EH, UK
| | - Wenbo Zhan
- School of Engineering, King's College, University of Aberdeen, Aberdeen, AB24 3UE, UK
| | - Daniele Dini
- Department of Mechanical Engineering, Imperial College London, London, SW7 2AZ, UK
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The Bidirectional Link Between Sleep Disturbances and Traumatic Brain Injury Symptoms: A Role for Glymphatic Dysfunction? Biol Psychiatry 2022; 91:478-487. [PMID: 34481662 PMCID: PMC8758801 DOI: 10.1016/j.biopsych.2021.06.025] [Citation(s) in RCA: 13] [Impact Index Per Article: 6.5] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 03/15/2021] [Revised: 06/28/2021] [Accepted: 06/29/2021] [Indexed: 12/14/2022]
Abstract
Mild traumatic brain injury (mTBI), often referred to as concussion, is a major cause of morbidity and mortality worldwide. Sleep disturbances are common after mTBI. Moreover, subjects who develop subjective sleep complaints after mTBI also report more severe somatic, mental health, and cognitive impairment and take longer to recover from mTBI sequelae. Despite many previous studies addressing the role of sleep in post-mTBI morbidity, the mechanisms linking sleep to recovery after mTBI remain poorly understood. The glymphatic system is a brainwide network that supports fluid movement through the cerebral parenchyma and the clearance of interstitial solutes and wastes from the brain. Notably, the glymphatic system is active primarily during sleep. Clearance of cellular byproducts related to somatic, mental health, and neurodegenerative processes (e.g., amyloid-β and tau, among others) depends in part on intact glymphatic function, which becomes impaired after mTBI. In this viewpoint, we review the current knowledge regarding the association between sleep disturbances and post-mTBI symptoms. We also discuss the role of glymphatic dysfunction as a potential link between mTBI, sleep disruption, and posttraumatic morbidity. We outline a model where glymphatic dysfunction and sleep disruption caused by mTBI may have an additive effect on waste clearance, leading to cerebral dysfunction and impaired recovery. Finally, we review the novel techniques being developed to examine glymphatic function in humans and explore potential interventions to alter glymphatic exchange that may offer a novel therapeutic approach to those experiencing poor sleep and prolonged symptoms after mTBI.
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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: 87] [Impact Index Per Article: 43.5] [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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36
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Elbert DL, Patterson BW, Lucey BP, Benzinger TLS, Bateman RJ. Importance of CSF-based Aβ clearance with age in humans increases with declining efficacy of blood-brain barrier/proteolytic pathways. Commun Biol 2022; 5:98. [PMID: 35087179 PMCID: PMC8795390 DOI: 10.1038/s42003-022-03037-0] [Citation(s) in RCA: 15] [Impact Index Per Article: 7.5] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 03/12/2021] [Accepted: 12/27/2021] [Indexed: 12/21/2022] Open
Abstract
The kinetics of amyloid beta turnover within human brain is still poorly understood. We previously found a dramatic decline in the turnover of Aβ peptides in normal aging. It was not known if brain interstitial fluid/cerebrospinal fluid (ISF/CSF) fluid exchange, CSF turnover, blood-brain barrier function or proteolysis were affected by aging or the presence of β amyloid plaques. Here, we describe a non-steady state physiological model developed to decouple CSF fluid transport from other processes. Kinetic parameters were estimated using: (1) MRI-derived brain volumes, (2) stable isotope labeling kinetics (SILK) of amyloid-β peptide (Aβ), and (3) lumbar CSF Aβ concentration during SILK. Here we show that changes in blood-brain barrier transport and/or proteolysis were largely responsible for the age-related decline in Aβ turnover rates. CSF-based clearance declined modestly in normal aging but became increasingly important due to the slowing of other processes. The magnitude of CSF-based clearance was also lower than that due to blood-brain barrier function plus proteolysis. These results suggest important roles for blood-brain barrier transport and proteolytic degradation of Aβ in the development Alzheimer’s Disease in humans. To understand if brain interstitial fluid/cerebrospinal fluid (ISF/CSF) exchange, CSF turnover, blood-brain barrier function or proteolysis were affected by aging or the presence of β amyloid plaques, Elbert et al. develop a non-steady state physiological model using MRI-derived brain volumes, stable isotope labeling kinetics of Aβ, and lumbar CSF Aβ concentration. Their model suggests an important role for blood-brain barrier transport and proteolytic degradation of Aβ in the development Alzheimer’s Disease in humans.
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Affiliation(s)
- Donald L Elbert
- Department of Neurology, Dell Medical School, University of Texas at Austin, Austin, TX, USA.
| | - Bruce W Patterson
- Department of Medicine, Washington University in St. Louis, St. Louis, MO, USA
| | - Brendan P Lucey
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, USA.,Hope Center for Neurological Disorders, Washington University School of Medicine, St Louis, MO, USA
| | - Tammie L S Benzinger
- Hope Center for Neurological Disorders, Washington University School of Medicine, St Louis, MO, USA.,Department of Radiology, Washington University School of Medicine, St. Louis, MO, USA
| | - Randall J Bateman
- Department of Neurology, Washington University School of Medicine, St. Louis, MO, USA.,Hope Center for Neurological Disorders, Washington University School of Medicine, St Louis, MO, USA
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37
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Liu X, Wu G, Tang N, Li L, Liu C, Wang F, Ke S. Glymphatic Drainage Blocking Aggravates Brain Edema, Neuroinflammation via Modulating TNF-α, IL-10, and AQP4 After Intracerebral Hemorrhage in Rats. Front Cell Neurosci 2022; 15:784154. [PMID: 34975411 PMCID: PMC8718698 DOI: 10.3389/fncel.2021.784154] [Citation(s) in RCA: 18] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 09/27/2021] [Accepted: 12/01/2021] [Indexed: 11/17/2022] Open
Abstract
Objective: The “Glymphatic” system, a network of perivascular tunnels wrapped by astrocyte endfeet, was reported to be closely associated with the diseases of the central nervous system. Here, we investigated the role of the glymphatic system in intracerebral hemorrhage (ICH) and its protective mechanism. Method: Experimental ICH model was induced by type IV collagenase in rats. Cerebral lymphatic blockage was induced by ligation and removal of cervical lymph nodes. The experimental rats were divided into sham-operated (SO) group, ICH group, and cerebral lymphatic blocking and ICH (ICH + CLB) group. Neurological scores were measured using the Garcia scoring system on the third and seventh day after ICH. Active caspase-3 was immunostained to evaluate neuronal apoptosis. Brain water content was calculated using the dry-wet specific gravity method. The expression of inflammatory factors TNF-α, IL-1β, and IL-10 were detected using ELISA. Aquaporins-4 (AQP-4) and glial fibrillary acidic protein (GFAP) were detected using western blot analysis. Results: The neurological scores of rats in the CLB + ICH group were significantly lower than those in the in ICH group. The number of active caspase-3 neurons was significantly higher in the CLB + ICH group compared to the ICH group. CLB significantly aggravated ICH-induced brain edema 3 d after ICH. There was an increase in the expression of TNF-α, IL-1β, IL-10, AQP-4, GFAP after ICH. The expression of TNF-α was significantly higher in the CLB + ICH group compared to ICH group 3 d after ICH while there was no difference 7 d after ICH. There was no statistical difference in the expression of IL-1β between the ICH group and CLB + ICH group. However, the expression of IL-10 in the CLB + ICH group was significantly lower than that in the ICH group. Lastly, AQP-4 expression was significantly lower in the CLB + ICH group compared to the ICH group while the expression of GFAP was higher in the CLB + ICH group compared to the ICH group. Conclusion: CLB exacerbated cerebral edema, neuroinflammation, neuronal apoptosis and caused neurological deficits in rats with ICH via down-regulating AQP-4, up-regulating inflammatory TNF-α and inhibiting IL-10 expression. The glymphatic drainage system protects against neurologic injury after ICH induction in rats under normal physiological conditions.
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Affiliation(s)
- Xichang Liu
- Department of Neurology, First People's Hospital of Yichang, Yichang, China
| | - Gang Wu
- Department of Pharmacy, Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University, Linhai, China
| | - Na Tang
- Department of Neurology, First People's Hospital of Yichang, Yichang, China
| | - Li Li
- Department of Neurology, First People's Hospital of Yichang, Yichang, China
| | - Cuimin Liu
- Department of Pharmacy, Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University, Linhai, China
| | - Feng Wang
- Department of Neurology, Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University, Linhai, China
| | - Shaofa Ke
- Department of Neurology, Taizhou Hospital of Zhejiang Province Affiliated to Wenzhou Medical University, Linhai, China
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38
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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] [MESH Headings] [Grants] [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 ([Formula: see text]), a transport parameter combining all mechanisms of transport, that best represent the experimental data are determined and compared to apparent diffusivity ([Formula: see text]), 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, [Formula: see text] for gadoteridol (550 Da) was over 10,000 times greater than [Formula: see text]. In the brain tissue, constituting interstitial space and the perivascular space of smaller blood vessels, [Formula: see text] was 10-25 times greater than [Formula: see text]. 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.
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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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39
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Ringstad G, Eide PK. Molecular trans-dural efflux to skull bone marrow in humans with cerebrospinal fluid disorders. Brain 2021; 145:1464-1472. [PMID: 34849609 PMCID: PMC9128823 DOI: 10.1093/brain/awab388] [Citation(s) in RCA: 24] [Impact Index Per Article: 8.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 05/24/2021] [Revised: 09/24/2021] [Accepted: 10/05/2021] [Indexed: 11/14/2022] Open
Abstract
Dural sinuses were recently identified as a hub for peripheral immune surveillance of brain-derived antigens cleared through CSF. However, animal studies have also indicated that substances and cells may enter the intracranial compartment directly from bone marrow. We used MRI and a CSF tracer to investigate in vivo whether intracranial molecules can move via dura to skull bone marrow in patients with suspicion of CSF disorders. Tracer enrichment in CSF, dural regions and within skull bone marrow was assessed up to 48 h after intrathecal administration of gadobutrol (0.5 ml, 1 mmol/ml) in 53 patients. In participants diagnosed with disease, tracer enrichment within diploe of skull bone marrow was demonstrated nearby the parasagittal dura, nearby extensions of parasagittal dura into diploe, and in diploe of skull bone remote from the dura extensions. This crossing of meningeal and skull barriers suggests that bone marrow may contribute in brain immune surveillance also in humans.
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Affiliation(s)
- Geir Ringstad
- Deptartment of Radiology, Oslo University Hospital-Rikshospitalet, Pb 4950 Nydalen, N-0424 Oslo, Norway
| | - Per Kristian Eide
- Department of Neurosurgery, Oslo University Hospital-Rikshospitalet, Pb 4950 Nydalen, N-0424 Oslo, Norway.,Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, PB 1072 Blindern, N-0316 Oslo, Norway
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40
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Rau A, Reisert M, Kellner E, Hosp JA, Urbach H, Demerath T. Increased interstitial fluid in periventricular and deep white matter hyperintensities in patients with suspected idiopathic normal pressure hydrocephalus. Sci Rep 2021; 11:19552. [PMID: 34599204 PMCID: PMC8486779 DOI: 10.1038/s41598-021-98054-0] [Citation(s) in RCA: 10] [Impact Index Per Article: 3.3] [Reference Citation Analysis] [Abstract] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 04/19/2021] [Accepted: 08/26/2021] [Indexed: 01/18/2023] Open
Abstract
Periventricular white matter changes are common in patients with idiopathic normal pressure hydrocephalus (iNPH) and considered to represent focally elevated interstitial fluid. We compared diffusion measures in periventricular hyperintensities in patients with imaging features of iNPH to patients without. The hypothesis is that periventricular hyperintensities in patients with presumed iNPH show higher water content than in patients without imaging features of iNPH. 21 patients with iNPH Radscale 7-12 ("high probability of iNPH") and 10 patients with iNPH Radscale 2-4 ("low probability of iNPH") were examined with a neurodegeneration imaging protocol including a diffusion microstructure imaging sequence. Periventricular hyperintensities and deep white matter hyperintensities were segmented and diffusion measures were compared. In patients with imaging features of iNPH, the free water content in periventricular hyperintensities was significantly higher compared to the control group (p = 0.005). This effect was also detectable in deep white matter hyperintensities (p = 0.024). Total brain volumes and total gray or white matter volumes did not differ between the groups. Periventricular cap free water fraction was highly discriminative regarding patients with presumed iNPH and controls with an ROC AUC of 0.933. Quantitative diffusion microstructure imaging shows elevated water content in periventricular hyperintensities in patients with imaging features of iNPH, which could be the imaging correlate for pathologic fluid accumulation and may be used as an imaging biomarker in the future.
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Affiliation(s)
- Alexander Rau
- Department of Neuroradiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Marco Reisert
- Medical Physics, Department of Radiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Elias Kellner
- Medical Physics, Department of Radiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Jonas A Hosp
- Department of Neurology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Horst Urbach
- Department of Neuroradiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany
| | - Theo Demerath
- Department of Neuroradiology, Medical Center - University of Freiburg, Faculty of Medicine, University of Freiburg, Freiburg, Germany.
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41
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Bèchet NB, Shanbhag NC, Lundgaard I. Glymphatic pathways in the gyrencephalic brain. J Cereb Blood Flow Metab 2021; 41:2264-2279. [PMID: 33641515 PMCID: PMC8393296 DOI: 10.1177/0271678x21996175] [Citation(s) in RCA: 20] [Impact Index Per Article: 6.7] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/14/2020] [Revised: 01/22/2021] [Accepted: 01/28/2021] [Indexed: 01/11/2023]
Abstract
Identification of the perivascular compartment as the point of exchange between cerebrospinal fluid (CSF) and interstitial fluid mediating solute clearance in the brain, named the glymphatic system, has emerged as an important clearance pathway for neurotoxic peptides such as amyloid-beta. However, the foundational science of the glymphatic system is based on rodent studies. Here we investigated whether the glymphatic system exists in a large mammal with a highly gyrified brain. CSF penetration into the brain via perivascular pathways, a hallmark of glymphatic function, was seen throughout the gyrencephalic cortex and subcortical structures, validating the conservation of the glymphatic system in a large mammal. Macroscopic CSF tracer distribution followed the sulci and fissures showing that these folds enhance CSF dispersion. Three-dimensional renditions from light sheet microscopy showed a PVS influx density 4-fold larger in the pig brain than in mice. This demonstrates the existence of an advanced solute transport system in the gyrencephalic brain that could be utilised therapeutically for enhancing waste clearance.
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Affiliation(s)
- Nicholas Burdon Bèchet
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Nagesh C Shanbhag
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Iben Lundgaard
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
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Kylkilahti TM, Berends E, Ramos M, Shanbhag NC, Töger J, Markenroth Bloch K, Lundgaard I. Achieving brain clearance and preventing neurodegenerative diseases-A glymphatic perspective. J Cereb Blood Flow Metab 2021; 41:2137-2149. [PMID: 33461408 PMCID: PMC8392766 DOI: 10.1177/0271678x20982388] [Citation(s) in RCA: 27] [Impact Index Per Article: 9.0] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Submit a Manuscript] [Subscribe] [Scholar Register] [Received: 09/15/2020] [Revised: 10/28/2020] [Accepted: 11/20/2020] [Indexed: 12/12/2022]
Abstract
Age-related neurodegenerative diseases are a growing burden to society, and many are sporadic, meaning that the environment, diet and lifestyle play significant roles. Cerebrospinal fluid (CSF)-mediated clearing of brain waste products via perivascular pathways, named the glymphatic system, is receiving increasing interest, as it offers unexplored perspectives on understanding neurodegenerative diseases. The glymphatic system is involved in clearance of metabolic by-products such as amyloid-β from the brain, and its function is believed to lower the risk of developing some of the most common neurodegenerative diseases. Here, we present magnetic resonance imaging (MRI) data on the heart cycle's control of CSF flow in humans which corroborates findings from animal studies. We also review the importance of sleep, diet, vascular health for glymphatic clearance and find that these factors are also known players in brain longevity.
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Affiliation(s)
- Tekla Maria Kylkilahti
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Eline Berends
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Marta Ramos
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Nagesh C Shanbhag
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
| | - Johannes Töger
- Diagnostic Radiology, Department of Clinical Sciences, Lund University and Skane University Hospital Lund, Lund, Sweden
| | | | - Iben Lundgaard
- Department of Experimental Medical Science, Lund University, Lund, Sweden
- Wallenberg Centre for Molecular Medicine, Lund University, Lund, Sweden
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43
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Eide PK, Vinje V, Pripp AH, Mardal KA, Ringstad G. Sleep deprivation impairs molecular clearance from the human brain. Brain 2021; 144:863-874. [PMID: 33829232 DOI: 10.1093/brain/awaa443] [Citation(s) in RCA: 139] [Impact Index Per Article: 46.3] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/21/2020] [Revised: 08/24/2020] [Accepted: 10/08/2020] [Indexed: 01/02/2023] Open
Abstract
It remains an enigma why human beings spend one-third of their life asleep. Experimental data suggest that sleep is required for clearance of waste products from brain metabolism. This has, however, never been verified in humans. The primary aim of the present study was to examine in vivo whether one night of total sleep deprivation affects molecular clearance from the human brain. Secondarily, we examined whether clearance was affected by subsequent sleep. Multiphase MRI with standardized T1 sequences was performed up to 48 h after intrathecal administration of the contrast agent gadobutrol (0.5 ml of 1 mmol/ml), which served as a tracer molecule. Using FreeSurfer software, we quantified tracer enrichment within 85 brain regions as percentage change from baseline of normalized T1 signals. The cerebral tracer enrichment was compared between two cohorts of individuals; one cohort (n = 7) underwent total sleep deprivation from Day 1 to Day 2 (sleep deprivation group) while an age and gender-matched control group (n = 17; sleep group) was allowed free sleep from Day 1 to Day 2. From Day 2 to 3 all individuals were allowed free sleep. The tracer enriched the brains of the two groups similarly. Sleep deprivation was the sole intervention. One night of sleep deprivation impaired clearance of the tracer substance from most brain regions, including the cerebral cortex, white matter and limbic structures, as demonstrated on the morning of Day 2 after intervention (sleep deprivation/sleep). Moreover, the impaired cerebral clearance in the sleep deprivation group was not compensated by subsequent sleep from Day 2 to 3. The present results provide in vivo evidence that one night of total sleep deprivation impairs molecular clearance from the human brain, and that humans do not catch up on lost sleep.
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Affiliation(s)
- Per Kristian Eide
- Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway.,Department of Neurosurgery, Oslo University Hospital - Rikshospitalet, Oslo, Norway
| | - Vegard Vinje
- Center for Biomedical Computing, Simula Research Laboratory, Lysaker, Norway
| | - Are Hugo Pripp
- Oslo Centre of Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, Oslo, Norway
| | - Kent-Andre Mardal
- Center for Biomedical Computing, Simula Research Laboratory, Lysaker, Norway.,Department of Mathematics, University of Oslo, Oslo, Norway
| | - Geir Ringstad
- Department of Radiology, Oslo University Hospital - Rikshospitalet, Oslo, Norway
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44
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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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45
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Eide PK, Pripp AH, Ringstad G, Valnes LM. Impaired glymphatic function in idiopathic intracranial hypertension. Brain Commun 2021; 3:fcab043. [PMID: 34235434 PMCID: PMC8253298 DOI: 10.1093/braincomms/fcab043] [Citation(s) in RCA: 29] [Impact Index Per Article: 9.7] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 12/29/2020] [Revised: 01/28/2021] [Indexed: 12/13/2022] Open
Abstract
Idiopathic intracranial hypertension is a brain disease incorporating cerebrospinal fluid disturbance, increased intracranial pressure and visual failure, but with unknown cause. This study examined a hypothesis that glymphatic function is impaired in idiopathic intracranial hypertension patients. The MRI contrast agent gadobutrol was utilized as a cerebrospinal fluid tracer following intrathecal administration. Consecutive standardized T1 MRI acquisitions over 48 h were done to assess tracer distribution within brain of 15 idiopathic intracranial hypertension patients and 15 reference individuals who were comparable in age and gender distribution. Using FreeSurfer software, we semi-quantified tracer level in multiple brain regions as T1 MRI signal change. The tracer enriched the entire brain of idiopathic intracranial hypertension and reference subjects. In idiopathic intracranial hypertension, tracer enrichment was increased and clearance of tracer delayed from a wide range of brain regions, including both grey and white matter. Differences were most evident in frontal and temporal regions. The pulsatile intracranial pressure was measured overnight and tracer propagation in brain compared between individuals with pathological and normal pulsatile intracranial pressure. In individuals with pathological pulsatile intracranial pressure, tracer enrichment was stronger and clearance from brain delayed, particularly in regions nearby large artery trunks at the brain surface. The present in vivo observations provide evidence for impaired glymphatic function in several brain regions of idiopathic intracranial hypertension patients. Glymphatic failure may imply altered clearance of metabolic byproducts, which may precede neurodegeneration. Further studies are needed to characterize glymphatic failure in idiopathic intracranial hypertension.
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Affiliation(s)
- Per Kristian Eide
- Institute of Clinical Medicine, University of Oslo, N-0316 Oslo, Norway.,Department of Neurosurgery, Oslo University Hospital-Rikshospitalet, N-0424 Oslo, Norway
| | - Are Hugo Pripp
- Oslo Centre of Biostatistics and Epidemiology, Research Support Services, Oslo University Hospital, N-0424 Oslo, Norway
| | - Geir Ringstad
- Department of Radiology, Oslo University Hospital-Rikshospitalet, N-0424 Oslo, Norway
| | - Lars Magnus Valnes
- Department of Neurosurgery, Oslo University Hospital-Rikshospitalet, N-0424 Oslo, Norway
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46
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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: 30] [Impact Index Per Article: 7.5] [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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Eide PK, Pripp AH, Ringstad G. Magnetic resonance imaging biomarkers of cerebrospinal fluid tracer dynamics in idiopathic normal pressure hydrocephalus. Brain Commun 2020; 2:fcaa187. [PMID: 33381757 PMCID: PMC7753057 DOI: 10.1093/braincomms/fcaa187] [Citation(s) in RCA: 20] [Impact Index Per Article: 5.0] [Reference Citation Analysis] [Abstract] [Key Words] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 06/13/2020] [Revised: 09/09/2020] [Accepted: 09/22/2020] [Indexed: 12/14/2022] Open
Abstract
Disturbed clearance of toxic metabolites from the brain via cerebrospinal fluid is emerging as an important mechanism behind dementia and neurodegeneration. To this end, magnetic resonance imaging work-up of dementia diseases is largely focused on anatomical derangements of the brain. This study explores magnetic resonance imaging biomarkers of cerebrospinal fluid tracer dynamics in patients with the dementia subtype idiopathic normal pressure hydrocephalus and a cohort of reference subjects. All study participants underwent multi-phase magnetic resonance imaging up to 48 h after intrathecal administration of the contrast agent gadobutrol (0.5 ml, 1 mmol/ml), serving as cerebrospinal fluid tracer. Imaging biomarkers of cerebrospinal fluid tracer dynamics (i.e. ventricular reflux grades 0–4 and clearance) were compared with anatomical magnetic resonance imaging biomarkers of cerebrospinal fluid space anatomy (Evans’ index, callosal angle and disproportional enlargement of subarachnoid spaces hydrocephalus) and neurodegeneration (Schelten’s medial temporal atrophy scores, Fazeka’s scores and entorhinal cortex thickness). The imaging scores were also related to a pulsatile intracranial pressure score indicative of intracranial compliance. In shunt-responsive idiopathic normal pressure hydrocephalus, the imaging biomarkers demonstrated significantly altered cerebrospinal fluid tracer dynamics (ventricular reflux grades 3–4 and reduced clearance of tracer), deranged cerebrospinal fluid space anatomy and pronounced neurodegeneration. The altered MRI biomarkers were accompanied by pressure indices of impaired intracranial compliance. In conclusion, we present novel magnetic resonance imaging biomarkers characterizing idiopathic normal pressure hydrocephalus pathophysiology, namely measures of cerebrospinal fluid molecular redistribution and clearance, which add information to traditional imaging scores of cerebrospinal fluid space anatomy and neurodegeneration.
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Affiliation(s)
- Per Kristian Eide
- Department of Neurosurgery, Oslo University Hospital-Rikshospitalet, Oslo, Norway.,Institute of Clinical Medicine, Faculty of Medicine, University of Oslo, Oslo, Norway
| | - Are H Pripp
- Oslo Centre of Biostatistics and Epidemiology, Oslo University Hospital, Oslo, Norway
| | - Geir Ringstad
- Department of Radiology, Oslo University Hospital- Rikshospitalet, Oslo, Norway
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