Parenchymal border macrophages regulate the flow dynamics of the cerebrospinal fluid
Antoine Drieu, Siling Du, Steffen E. Storck, Justin Rustenhoven, Zachary Papadopoulos, Taitea Dykstra, Fenghe Zhong, Kyungdeok Kim, Susan Blackburn, Tornike Mamuladze, Oscar Harari, Celeste M. Karch, Randall J. Bateman, Richard J. Perrin, Martin R. Farlow, Jasmeer P. Chhatwal, Dominantly Inherited Alzheimer Network, Jared R. Brosch, Jill Buck, Marty Farlow, Bernardino Ghetti, Sarah Adams, Nicolas R. Barthélemy, Tammie L.S. Benzinger, Susan E. Brandon, Virginia Buckles, Lisa Cash, Charlie Chen, Jasmin Chua, Carlos Cruchaga, Darcy Denner, Aylin Dincer, Tamara Donahue, Anne M. Fagan, Becca Feldman, Shaney Flores, Erin Franklin, Nelly Joseph‐Mathurin, Alyssa Gonzalez, Brian A. Gordon, Julia Gray, Emily Gremminger, Alex Groves, Jason Hassenstab, Cortaiga Hellm, Elizabeth Herries, Laura Hoechst-Swisher, David M. Holtzman, Russ C. Hornbeck, Gina Jerome, Sarah Keefe, Deb Koudelis, Yan Li, Jacob I. Marsh, Rita Martinez, Kwasi G. Mawuenyega, Austin McCullough, Eric McDade, John Morris, Joanne Norton, Kristine Shady, Wendy Sigurdson, Jennifer A. Smith, Peter Wang, Qing Wang, Chengjie Xiong, Jinbin Xu, Xu Xiong, Ricardo Allegri, Patricio Chrem Méndez, Noelia Egido, Aki Araki, Takeshi Ikeuchi, Kenji Ishii, Kensaku Kasuga, Jacob Bechara, W. K. Brooks, Peter R. Schofield, Sarah Berman, Sarah B. Goldberg, Snežana Ikonomović, William E. Klunk, Oscar L. López, James M. Mountz, Neelesh K. Nadkarni, Riddhi Patira, Lori Smith, Beth E. Snitz, Sarah Thompson, Elise A. Weamer, Courtney Bodge, Stephen Salloway, Kathleen Carter, Duc M. Duong, Erik C. B. Johnson, Allan I. Levey, Lingyan Ping, Nicholas T. Seyfried, Colleen Fitzpatrick, Helena C. Chui
Abstract
Macrophages are important players in the maintenance of tissue homeostasis1. Perivascular and leptomeningeal macrophages reside near the central nervous system (CNS) parenchyma2, and their role in CNS physiology has not been sufficiently well studied. Given their continuous interaction with the cerebrospinal fluid (CSF) and strategic positioning, we refer to these cells collectively as parenchymal border macrophages (PBMs). Here we demonstrate that PBMs regulate CSF flow dynamics. We identify a subpopulation of PBMs that express high levels of CD163 and LYVE1 (scavenger receptor proteins), closely associated with the brain arterial tree, and show that LYVE1+ PBMs regulate arterial motion that drives CSF flow. Pharmacological or genetic depletion of PBMs led to accumulation of extracellular matrix proteins, obstructing CSF access to perivascular spaces and impairing CNS perfusion and clearance. Ageing-associated alterations in PBMs and impairment of CSF dynamics were restored after intracisternal injection of macrophage colony-stimulating factor. Single-nucleus RNA sequencing data obtained from patients with Alzheimer’s disease (AD) and from non-AD individuals point to changes in phagocytosis, endocytosis and interferon-γ signalling on PBMs, pathways that are corroborated in a mouse model of AD. Collectively, our results identify PBMs as new cellular regulators of CSF flow dynamics, which could be targeted pharmacologically to alleviate brain clearance deficits associated with ageing and AD. Perivascular and leptomeningeal macrophages, collectively termed here parenchymal border macrophages, are shown to regulate flow dynamics of cerebrospinal fluid, implicating this cell population as new therapeutic targets in neurological diseases such as Alzheimer’s.