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Review
. 2021 Jul 7:15:665803.
doi: 10.3389/fnana.2021.665803. eCollection 2021.

Waste Clearance in the Brain

Jasleen Kaur  1   2 , Lara M Fahmy  1   3 , Esmaeil Davoodi-Bojd  1   4 , Li Zhang  1 , Guangliang Ding  1 , Jiani Hu  5 , Zhenggang Zhang  1   6 , Michael Chopp  1   2 , Quan Jiang  1   2   6
Affiliations
Review

Waste Clearance in the Brain

Jasleen Kaur et al. Front Neuroanat. .

Abstract

Waste clearance (WC) is an essential process for brain homeostasis, which is required for the proper and healthy functioning of all cerebrovascular and parenchymal brain cells. This review features our current understanding of brain WC, both within and external to the brain parenchyma. We describe the interplay of the blood-brain barrier (BBB), interstitial fluid (ISF), and perivascular spaces within the brain parenchyma for brain WC directly into the blood and/or cerebrospinal fluid (CSF). We also discuss the relevant role of the CSF and its exit routes in mediating WC. Recent discoveries of the glymphatic system and meningeal lymphatic vessels, and their relevance to brain WC are highlighted. Controversies related to brain WC research and potential future directions are presented.

Keywords: arachnoid villi; cerebrospinal fluid; glymphatic system; interstitial fluid; interstitial waste products; meningeal lymphatics; perineural spaces; perivascular spaces.

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Conflict of interest statement

The authors declare that the research was conducted in the absence of any commercial or financial relationships that could be construed as a potential conflict of interest.

Figures

Figure 1
Figure 1
Schematic illustration of Waste Clearance (WC) in the brain. (A) Schematic model of cerebrospinal fluid (CSF) flow which is involved in brain WC, both within (B) and external to the brain parenchyma (C). Dotted arrows show the movement of CSF from the ventricular compartments to the subarachnoid space, entering the brain parenchyma via periarterial spaces, getting mixed with interstitial waste products as well as interstitial fluid (ISF), entering the perivenous space, and then draining via perineural spaces and lymphatics. The waste products also reach the vascular compartments directly via the blood-brain barrier (BBB) and indirectly via CSF exiting through the arachnoid villi/granulations. (Bi) A magnified schematic image of the glymphatic system and intramural periarterial drainage (IPAD) pathways involved in WC within the brain parenchyma. (Bii) A magnified schematic image of the vascular pathway via the BBB at the capillary level. (C) A schematic image of the CSF pathways involved in brain WC via the arachnoid villi (Ci), and lymphatic pathways [including the nasal lymphatics (Cii), and the meningeal lymphatics (Ciii)].
See this image and copyright information in PMC

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