Abstract TMP118: Novel Regulation Of Peripheral Derived Immune Cells In The Remodeling Of Pial Collateral Vessels Following Ischemic Stroke

Abstract

Introduction: Stroke is a leading cause of neurological morbidity and mortality in the United States. Remodeling of pial collateral (PC) vessels (arteriogenesis) is vital to restore blood perfusion into the ischemic penumbra to reduce damage. Previous reports showed perivascular monocyte /macrophage (MM) accumulation in hind limb ischemia and myocardial infarction, suggesting that MM are key regulators of inflammatory milieu following stroke. We reported EphA4 as a negative regulator of PC remodeling. However, the role of EphA4 during peripheral derived immune cell (PDI) mediated arteriogenesis after permanent middle cerebral artery occlusion (pMCAO) remains unknown. This study explores the role of EphA4 in regulating PDI-mediated arteriogenesis after pMCAO and interrogates if MM-specific EphA4 contributes to the neuroinflammatory milieu during remodeling process. Methods: GFP reporter EphA4 bone marrow chimeric knockout (KO BMCs ) and wild-type mice (WT BMCs ) were euthanized 1d post pMCAO. Vessel painted whole brains were used for immunostaining, infarct volume measurement, and confocal histological analysis including PC remodeling and GFP+ perivascular immune cell recruitment. Blood from sham and pMCAO mice was collected for flow cytometry to analyze EphA4 expression on circulating immune cell types. We performed rotarod test to assess behavioral recovery, and used clodronate liposome for MM depletion in both WT BMCs and KO BMCs to further explore the function of EphA4 MM after stroke. Results: This study developed a novel methodology to evaluate MM-specific EphA4 role after pMCAO. EphA4 was highly expressed on Ly6G+ neutrophils, Ly6Chi, and Ly6Clo MM in whole blood 24h after pMCAO. KO BMCs mice had enhanced growth of ipsilateral PC compared to WT BMCs mice after pMCAO. These findings correlate with KO BMCs reduced infarct volume and improved motor function compared to WT BMCs . Finally, WT BMCs displayed a significant increase in GFP+ PDI recruitment to the PC wall in KO BMCs compared to WT BMCs mice. Conclusions: PDI-specific EphA4 expression negatively regulates arteriogenesis and suppresses PDI accumulation on PC. The acute neurovascular inflammation may be dependent on the EphA4 expression of MM in the peripheral circulation after stroke.