Blocking cerebral lymphatic system reduces central and peripheral inflammatory response in ischemic stroke

Abstract

Reduced blood supply to the brain activates the intracranial inflammatory response, a key contributor to secondary brain damage in ischemic stroke. Post-stroke, activation of peripheral immune cells leads to systemic inflammatory responses. Usingin vivo approaches, we investigated meningeal lymphatics' role in central immune cell infiltration and peripheral immune cell activation. The bilateral deep cervical lymph nodes (dCLNs) were removed 7 days before right middle cerebral artery occlusion in Sprague Dawley (SD) rats. At 3, 24, and 72 h post-intervention, brain immune cell infiltration and microglial and astrocyte activation were measured, while immune cells were classified in the spleen and blood. Inflammatory factor levels in peripheral blood were analyzed. Simultaneously, reverse verification was conducted by injecting AAV-vascular endothelial growth factor C (AAV-VEGFC) adenovirus into the lateral ventricle 14 days before middle cerebral artery occlusion (MCAO) induction to enhance meningeal lymph function. Blocking meningeal LVs in MCAO rats significantly reduced infarct area and infiltration, and inhibited microglia and pro-inflammatory astrocytes activation. After removing dCLNs, CD4⁺ T lymphocytes, CD8⁺ T lymphocytes, B lymphocytes, macrophages, and neutrophils in the spleen and blood of MCAO rats decreased significantly at different time points. The levels of inflammatory factors IL-6, IL-10, IL-1β, and TNF-α in plasma decreased significantly. Tests confirmed the results, and AAV-VEGFC-induced MCAO rats provided reverse validation.

Keywords: Acute inflammation; Cerebral lymphatic system; Deep cervical lymph nodes; Meningeal lymphatic vessels; VEGF-C.