Lymphangiogenesis near the Cribriform Plate after Cerebral Ischemia

Abstract

Abstract Recently, it has been hypothesized that antigens, antigen-presenting cells (APC), and cerebrospinal fluid (CSF) may drain from the central nervous system (CNS) into lymphatics near the cribriform plate or dura to provide fluid homeostasis and antigen drainage. However, the role of lymphatic vessels during neuroinflammation is not well understood yet. Our lab has previously shown that lymphatic vessels near cribriform plate undergo lymphangiogenesis during experimental autoimmune encephalomyelitis (EAE), a mouse model of Multiple Sclerosis. Here, we looked to see whether lymphangiogenesis also occurs in a stroke mouse model of neuroinflammation. We established the transient middle cerebral artery occlusion (tMCAO) model of stroke by placing a filament for 60 minutes into the middle cerebral artery, that was followed by reperfusion after removing the filament. We show that lymphangiogenesis occurs near the cribriform plate, peaks at day 7 and decreases after 14 days following tMCAO. To confirm that the newly formed lymphoid vessels at the cribriform plate could connect with the CSF, we injected Evans Blue dye through the cisterna magna and confirmed the presence of the dye in these lymphoid vessels. Flow cytometry analysis showed that robust leukocyte infiltration such as microglia (CD45int, CD11b+), macrophage (CD45hi, CD11b+), dendritic cells (CD45hi, CD11b+, CD11c+), CD8 T cells (CD45hi, CD8+), CD4 T cells (CD45hi, CD4+), and B cells (CD45hi, B220+) near the cribriform plate after 7 days of tMCAO correlates with lymphangiogenesis (CD45−, Podoplanin+, CD31+). The manipulation of inflammation-induced lymphangiogenesis may lead to therapeutics for neuroinflammatory diseases.