# Inflammatory Mechanisms of Brain - Lymphatic Signaling in Stroke

> **NIH NIH R01** · MASSACHUSETTS GENERAL HOSPITAL · 2020 · $372,199

## Abstract

Inflammatory Mechanisms of Brain-Lymphatic Signaling in Stroke
After stroke, the peripheral immune system becomes activated, and these systemic inflammatory responses
are known to amplify brain injury and worsen outcomes. But a major gap in knowledge remains. It is unclear
how the stroke-damaged brain sends signals to the periphery.
Recently, it has been suggested that some type of specialized lymphatic drainage system may exist in the
CNS. Back in 1995, we had used CT imaging to show that tracers injected into rabbit brain can directly drain
into the cervical lymph nodes in vivo (Hunter et al, Neuropath Appl Neurobiol 1995). We now propose that this
brain-to-cervical-lymph node connection may provide a potential pathway for inflammatory crosstalk between
brain and systemic responses after stroke.
Based on our pilot data, we propose the hypothesis that after stroke, the injured neurovascular unit releases
signals that drain into the cervical lymph node and activate macrophages thus worsening neuroinflammation
and stroke outcomes: (i) after focal ischemia, brain astrocytes/pericytes/endothelial cells secrete VEGF-C into
CSF; (ii) VEGF-C travels into cervical lymph nodes, enhances pro-inflammatory signals in lymphatic
endothelium, and induces M1-like macrophage polarization and recruitment; (iii) M1-like macrophages then
contribute to further neuroinflammation and brain injury in both gray and white matter. We will test this
hypothesis in three integrated aims, using a combination of molecular tools, cell culture, and in vivo models.
In Aim 1, we assess and compare mechanisms for how astrocytes, pericytes and brain endothelial cells
release VEGF-C after oxygen-glucose deprivation. In Aim 2, we investigate mechanisms that underlie the
ability of VEGF-C to induce inflammation in lymphatic endothelium and activate macrophages. In Aim 3, we will
use mouse models of focal cerebral ischemia to confirm these brain-to-lymphatic signals in vivo, and examine
therapeutic approaches that may interrupt this pathway to improve stroke outcomes. To assess causality in our
pathways, we will conduct gain and loss-of-function experiments using a combination of cell culture, in vivo
mouse models, pharmacologic inhibitors, molecular techniques including siRNA and transgenics, long-term
neurological outcomes, and imaging.
This project should define a novel mechanism wherein the damaged neurovascular unit communicates with
peripheral lymphatics after stroke. Our findings may provide a new conceptual framework for seeking potential
stroke targets and biomarkers in the lymphatic system. Finally, this project may also help open up new
collaborative crosstalk between stroke biology and the well established field of lymphatic vascular biology.

## Key facts

- **NIH application ID:** 9920224
- **Project number:** 5R01NS099620-05
- **Recipient organization:** MASSACHUSETTS GENERAL HOSPITAL
- **Principal Investigator:** Kazuhide Hayakawa
- **Activity code:** R01 (R01, R21, SBIR, etc.)
- **Funding institute:** NIH
- **Fiscal year:** 2020
- **Award amount:** $372,199
- **Award type:** 5
- **Project period:** 2016-09-01 → 2022-05-31

## Primary source

NIH RePORTER: https://reporter.nih.gov/project-details/9920224

## Citation

> US National Institutes of Health, RePORTER application 9920224, Inflammatory Mechanisms of Brain - Lymphatic Signaling in Stroke (5R01NS099620-05). Retrieved via AI Analytics 2026-05-24 from https://api.ai-analytics.org/grant/nih/9920224. Licensed CC0.

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