Impaired Peripheral Lymphatic Function and Cerebrospinal Fluid Outflow in a Mouse Model of Alzheimer’s Disease

Article type: Research Article

Authors: Kwon, Sunkuk^{a; *} | Moreno-Gonzalez, Ines^b | Taylor-Presse, Kathleen^b | Edwards III, George^b | Gamez, Nazaret^b | Calderon, Olivia^b | Zhu, Banghe^a | Velasquez, Fred Christian^a | Soto, Claudio^b | Sevick-Muraca, Eva M.^a

Affiliations: [a] Center for Molecular Imaging, The Brown Foundation Institute of Molecular Medicine, Houston, TX, USA | [b] Mitchell Center for Alzheimer’s disease and Related Brain Disorders, Department of Neurology, The University of Texas Health Science Center, Houston, TX, USA

Correspondence: [*] Correspondence to: Sunkuk Kwon, Center for Molecular Imaging, The Brown Foundation Institute of Molecular Medicine, 1825 Pressler St, Houston, TX 77030, USA. Tel.: +1 713 500 3393; E-mail: sunkuk.kwon@uth.tmc.edu.

Abstract:  Cerebrospinal fluid (CSF) outflow from the brain occurs through absorption into the arachnoid villi and, more predominantly, through meningeal and olfactory lymphatics that ultimately drain into the peripheral lymphatics. Impaired CSF outflow has been postulated as a contributing mechanism in Alzheimer’s disease (AD). Herein we conducted near-infrared fluorescence imaging of CSF outflow into the peripheral lymph nodes (LNs) and of peripheral lymphatic function in a transgenic mouse model of AD (5XFAD) and wild-type (WT) littermates. CSF outflow was assessed from change in fluorescence intensity in the submandibular LNs as a function of time following bolus, an intrathecal injection of indocyanine green (ICG). Peripheral lymphatic function was measured by assessing lymphangion contractile function in lymphatics draining into the popliteal LN following intradermal ICG injection in the dorsal aspect of the hind paw. The results show 1) significantly impaired CSF outflow into the submandibular LNs of 5XFAD mice and 2) reduced contractile frequency in the peripheral lymphatics as compared to WT mice. Impaired CSF clearance was also evidenced by reduction of fluorescence on ventral surfaces of extracted brains of 5XFAD mice at euthanasia. These results support the hypothesis that lymphatic congestion caused by reduced peripheral lymphatic function could limit CSF outflow and may contribute to the cause and/or progression of AD.

Keywords: Cerebrospinal fluid outflow, fluorescence imaging, intrathecal, lymphatic system

DOI: 10.3233/JAD-190013

Journal: Journal of Alzheimer's Disease, vol. 69, no. 2, pp. 585-593, 2019