Endothelial proliferation in situ after stroke. On days 1, 3, 7, and 14 after stroke, the number of proliferating cells (BrdU⁺) and proliferating endothelial cells (co-staining for BrdU and CD31) was determined in the left cortical area of 1–1.5 mm distal from the midline. (A) Immunohistological analysis of proliferating cells labeled with BrdU (green), anti-mouse CD31 IgG (red), and both (yellow). The number of cells visualized with BrdU (B) and the subpopulation BrdU⁺ cells also displaying mouse CD31 (i.e., double positives) (C) are shown. Ten HPFs were evaluated for each animal (n = 6 per group) by two investigators blinded to the experimental protocol. Note in C, cells displaying mouse CD31 are termed endothelial cells (ECs). Black bars, ipsilateral; white bars, contralateral. *P < 0.05 versus control. Scale bar: 30 μm.