Abstract TP125: Temporal Alteration of Infiltrated Macrophage and Resident Microglia Following Focal Cerebral Ischemia Model in Mice

Abstract

Stroke, a devastating brain damage, is the second cause of adult disability and death following the heart disease worldwide. As the blood supply is insufficient to the brain tissue followed by occlusion of the cerebral artery, molecular cues generated by cerebral ischemia activate the components of innate immunity, promote inflammatory signaling and contribute to tissue damage. Microglia known as an immune cell in the central nervous system (CNS) has functions similar to those of macrophages in the periphery. Moreover, blood-brain barrier (BBB) causes the infiltration of blood-derived macrophages. However, the interaction between the microglia and blood-derived macrophage is still unknown. We used CX3CR1::EGFP transgenic mice to visualize the microglia and blood-derived macrophage dynamics on neuroinflammatory responses. Methods: We used CX3CR1::EGFP transcriptional reporter gene mice to visualize the microglia and macrophages to injured brain tissue on neuroinflammatory responses following transient middle cerebral artery occlusion (tMCAO) modeling. Also, we performed two-photon microscopy for intra-vital imaging, time-dependently. Results: Our preliminary data showed that it is morphologically possible to distinguish activated microglia and infiltrated macrophages from the resident microglia specifically in FACS and Immunohistochemistry. In addition, blood-derived macrophages and brain microglia showed different polarization patterns by specific markers (Iba1, Tmem119, CD86, CD206, and CD45) in time-dependent manners (n=5 /sham, 6 hours, 1, 3, 5, 7 days) after tMCAO. Furthermore, we performed the cytokine/chemokine array to evaluate the level of specific cytokine/chemokine on ischemic stroke using the brain tissue. In results, the levels of brain tissue of specific cytokine/chemokine showed different levels in all experimental time courses. Conclusion: Taken together, the overall data demonstrated that dynamics of microglia and blood-derived macrophage using specific type of transgenic mice could be a novel strategy for regulating the M2 anti-inflammatory microglia phenotype rather than M1 pro-inflammatory microglia and finding the optimal time point of drug treatment attenuating ischemic stroke.