Open pathways for cerebrospinal fluid outflow at the cribriform plate along the olfactory nerves

Irene Spera; Nikola Cousin; Miriam Ries; Anna Kedracka; Alina Castillo; Simone Aleandri; Mykhailo Vladymyrov; Josephine A Mapunda; Britta Engelhardt; Paola Luciani; Michael Detmar; Steven T Proulx

doi:10.1016/j.ebiom.2023.104558

Open pathways for cerebrospinal fluid outflow at the cribriform plate along the olfactory nerves

EBioMedicine. 2023 May:91:104558. doi: 10.1016/j.ebiom.2023.104558. Epub 2023 Apr 10.

Affiliations

¹ Theodor Kocher Institute, University of Bern, Bern, Switzerland.
² Institute of Pharmaceutical Sciences, ETH Zürich, Zürich, Switzerland.
³ Department of Chemistry, Biochemistry and Pharmaceutical Sciences, University of Bern, Bern, Switzerland.
⁴ Theodor Kocher Institute, University of Bern, Bern, Switzerland. Electronic address: steven.proulx@tki.unibe.ch.

Abstract

Background: Routes along the olfactory nerves crossing the cribriform plate that extend to lymphatic vessels within the nasal cavity have been identified as a critical cerebrospinal fluid (CSF) outflow pathway. However, it is still unclear how the efflux pathways along the nerves connect to lymphatic vessels or if any functional barriers are present at this site. The aim of this study was to anatomically define the connections between the subarachnoid space and the lymphatic system at the cribriform plate in mice.

Methods: PEGylated fluorescent microbeads were infused into the CSF space in Prox1-GFP reporter mice and decalcification histology was utilized to investigate the anatomical connections between the subarachnoid space and the lymphatic vessels in the nasal submucosa. A fluorescently-labelled antibody marking vascular endothelium was injected into the cisterna magna to demonstrate the functionality of the lymphatic vessels in the olfactory region. Finally, we performed immunostaining to study the distribution of the arachnoid barrier at the cribriform plate region.

Findings: We identified that there are open and direct connections from the subarachnoid space to lymphatic vessels enwrapping the olfactory nerves as they cross the cribriform plate towards the nasal submucosa. Furthermore, lymphatic vessels adjacent to the olfactory bulbs form a continuous network that is functionally connected to lymphatics in the nasal submucosa. Immunostainings revealed a discontinuous distribution of the arachnoid barrier at the olfactory region of the mouse.

Interpretation: Our data supports a direct bulk flow mechanism through the cribriform plate allowing CSF drainage into nasal submucosal lymphatics in mice.

Funding: This study was supported by the Swiss National Science Foundation (310030_189226), Dementia Research Switzerland-Synapsis Foundation, the Heidi Seiler Stiftung and the Fondation Dr. Corinne Schuler.

Keywords: Arachnoid barrier; Cerebrospinal fluid; Cribriform plate; Lymphatic vessels; Olfactory nerves.

MeSH terms

Animals
Ethmoid Bone
Lymphatic System / metabolism
Lymphatic Vessels*
Mice
Olfactory Nerve*
Subarachnoid Space / metabolism