Abstract W MP46: Beyond the Brain: Stroke Induces Vascular Breakdown and Unique Profiles of Peripheral Inflammatory Response in the Eye and Spinal Cord

Abstract

Ischemic stroke, a leading cause of death and long-term disability, has far-reaching effects across the CNS beyond the region of infarct. As extensions of the brain, neural networks of the eye and spinal cord are affected by cerebral ischemia through the transmission of inflammatory and degenerative changes. Although neuropathological effects of MCAO have been reported in both regions, the contribution of the peripheral inflammatory response to the evolution of injury in these CNS regions is unknown. We evaluated local glial responses, vascular integrity, leukocyte infiltration, and cytokine expression after stroke in the eye and spinal cord. Adult male C57Bl/6 WT or GFP+ bone marrow chimeric mice were subjected to 90-min MCAO or sham surgery (n=3-6). Imaging of the retinal vasculature was performed by ophthalmoscopy. At 8h, 24 and/or 36h, 72h and 7d post-stroke mice were perfused with PBS and sacrificed. Organs were harvested for immunohistochemistry, Evans blue extravasation, flow cytometry, and RT-qPCR. Early (8h) after MCAO, over four-fold increases in TNFα and IL-1β gene expression were observed in the ipsilateral eye relative to sham (4.64±1.21, 1±0.17; 11.03±7.75, 1±0.21). Microglial activation indicated by increased CD11b, CD45, and cell granularity at 36h was accompanied by an influx of peripheral leukocytes predominantly comprised of neutrophils (81%). In contrast to BBB breakdown which was highest at 24h, blood-retinal barrier breakdown peaked in the ipsilateral eye at 36h, shown by a twelve-fold increase in Evans blue concentration (sham, 24h, 36h: 0.16, 0.41, 1.95 ug/mg tissue wet weight). Similarly, major blood-spinal cord barrier breakdown occurred at 36h (0.32 vs 0.052 ug/mg). This was followed by a largely monocytic response with corresponding increases in TNFα, IL-1β, and IFNγ gene expression. Together, our data show robust unilateral peripheral inflammatory responses after stroke in CNS regions outside of the brain. In addition, blood-parenchymal barrier permeability peaks later in the eye and spinal cord than in the brain. Given the distinct time course and inflammatory components associated with each region, these findings may have wide implications for treatments attenuating CNS-wide inflammatory damage after stroke.