The use of flow cytometry to evaluate temporal changes in inflammatory cells following focal cerebral ischemia in mice

Recent studies indicate that inflammation following cerebral ischemia contributes to neuronal damage. The local activation of resident cells and efficient recruitment of leukocytes into the central nervous system are critical steps in this inflammatory process. Here we describe studies using flow cytometry to examine the temporal pattern of inflammatory cell activation and infiltration following transient middle cerebral artery occlusion (MCAO) in mice. We found an increase in activated microglia/macrophages as early as 18 h post occlusion, which peaked at 48 h and remained abundant at 96 h post occlusion. Neutrophils were significantly increased by 48 h and remained elevated at 96 h post occlusion. T lymphocytes were increased relatively late (72 and 96 h) post occlusion. The flow cytometry data correlate well both quantitatively and qualitatively with immunohistochemistry analysis performed on the same mice. The present study demonstrates the power of flow cytometry in analyzing the inflammatory process following cerebral ischemia and offers temporal information on the cellular changes in mice following transient MCAO.