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Abstract
Cerebrospinal fluid flows around and into the brain, driven by intricate mechanisms, with profound implications for human health. According to the glymphatic hypothesis, in physiological conditions, cerebrospinal fluid flows primarily during sleep and serves to remove metabolic wastes like the amyloid-beta and tau proteins whose accumulation is believed to cause Alzheimer's disease. This paper reviews one research team's recent in vivo experiments and theoretical studies to better understand the fluid dynamics of brain cerebrospinal fluid flow. Driving mechanisms are considered, particularly arterial pulsation. Flow correlates closely with artery motion and changes when artery motion is manipulated. Though there are discrepancies between in vivo observations and predictions from simulations and theoretical studies of the mechanism, realistic boundary conditions bring closer agreement. Vessel shapes are considered, and have elongation that minimizes their hydraulic resistance, perhaps through evolutionary optimization. The pathological condition of stroke is considered. Much tissue damage after stroke is caused by swelling, and there is now strong evidence that early swelling is caused not by fluid from blood, as is commonly thought, but by cerebrospinal fluid. Finally, drug delivery is considered, and demonstrations show the glymphatic system could quickly deliver drugs across the blood-brain barrier. The paper closes with a discussion of future opportunities in the fast-changing field of brain fluid dynamics.
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Affiliation(s)
- Douglas H. Kelley
- Department of Mechanical Engineering, University of Rochester, Rochester, New York 14627, USA
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Munk AS, Wang W, Bèchet NB, Eltanahy AM, Cheng AX, Sigurdsson B, Benraiss A, Mäe MA, Kress BT, Kelley DH, Betsholtz C, Møllgård K, Meissner A, Nedergaard M, Lundgaard I. PDGF-B Is Required for Development of the Glymphatic System. Cell Rep 2019; 26:2955-2969.e3. [PMID: 30865886 PMCID: PMC6447074 DOI: 10.1016/j.celrep.2019.02.050] [Citation(s) in RCA: 82] [Impact Index Per Article: 16.4] [Reference Citation Analysis] [Abstract] [Key Words] [MESH Headings] [Grants] [Track Full Text] [Download PDF] [Figures] [Journal Information] [Subscribe] [Scholar Register] [Received: 07/03/2018] [Revised: 01/07/2019] [Accepted: 02/13/2019] [Indexed: 01/07/2023] Open
Abstract
The glymphatic system is a highly polarized cerebrospinal fluid (CSF) transport system that facilitates the clearance of neurotoxic molecules through a brain-wide network of perivascular pathways. Herein we have mapped the development of the glymphatic system in mice. Perivascular CSF transport first emerges in hippocampus in newborn mice, and a mature glymphatic system is established in the cortex at 2 weeks of age. Formation of astrocytic endfeet and polarized expression of aquaporin 4 (AQP4) consistently coincided with the appearance of perivascular CSF transport. Deficiency of platelet-derived growth factor B (PDGF-B) function in the PDGF retention motif knockout mouse line Pdgfbret/ret suppressed the development of the glymphatic system, whose functions remained suppressed in adulthood compared with wild-type mice. These experiments map the natural development of the glymphatic system in mice and define a critical role of PDGF-B in the development of perivascular CSF transport.
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Affiliation(s)
- Anne Sofie Munk
- Center for Translational Neuromedicine, University of Rochester, Rochester, NY 14642, USA; Center for Basic and Translational Neuroscience, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Wei Wang
- Center for Translational Neuromedicine, University of Rochester, Rochester, NY 14642, USA
| | - Nicholas Burdon Bèchet
- Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden; Wallenberg Center for Molecular Medicine, Lund University, 221 84 Lund, Sweden
| | - Ahmed M Eltanahy
- Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden; Wallenberg Center for Molecular Medicine, Lund University, 221 84 Lund, Sweden; Mansoura University Hospital, Faculty of Medicine, Mansoura University, 35516 Mansoura, Egypt
| | - Anne Xiaoan Cheng
- Center for Translational Neuromedicine, University of Rochester, Rochester, NY 14642, USA
| | - Björn Sigurdsson
- Center for Basic and Translational Neuroscience, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Abdellatif Benraiss
- Center for Translational Neuromedicine, University of Rochester, Rochester, NY 14642, USA
| | - Maarja A Mäe
- Department of Immunology, Genetics and Pathology, Uppsala University, 751 85 Uppsala, Sweden
| | - Benjamin Travis Kress
- Center for Translational Neuromedicine, University of Rochester, Rochester, NY 14642, USA; Center for Basic and Translational Neuroscience, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Douglas H Kelley
- Department of Mechanical Engineering, University of Rochester, Rochester, NY 14627, USA
| | - Christer Betsholtz
- Department of Immunology, Genetics and Pathology, Uppsala University, 751 85 Uppsala, Sweden; Integrated Cardio Metabolic Center (ICMC), Karolinska Institutet, Novum, 141 57 Huddinge, Sweden
| | - Kjeld Møllgård
- Department of Cellular and Molecular Medicine, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Anja Meissner
- Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden; Wallenberg Center for Molecular Medicine, Lund University, 221 84 Lund, Sweden
| | - Maiken Nedergaard
- Center for Translational Neuromedicine, University of Rochester, Rochester, NY 14642, USA; Center for Basic and Translational Neuroscience, University of Copenhagen, 2200 Copenhagen, Denmark
| | - Iben Lundgaard
- Center for Translational Neuromedicine, University of Rochester, Rochester, NY 14642, USA; Department of Experimental Medical Science, Lund University, 221 84 Lund, Sweden; Wallenberg Center for Molecular Medicine, Lund University, 221 84 Lund, Sweden.
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