Therapeutic neovascularization supports survival of regenerating neurons. (A–C) Animals treated with PBS alone (A), CD34^– cells (B), or CD34⁺ cells (C) were infused with BrdU, killed, and studied immunohistochemically with antibody to BrdU (red), NeuN (green), or both (yellow). (D) The average number of double-positive cells (stained with antibody to BrdU and NeuN) per HPF on day 90 after cell transplantation. Ten fields were evaluated in each animal, and n = 6 per group. *P < 0.05 versus PBS. (E) On day 90 after cell transplantation, brain sections from animals treated with PBS alone, CD34^– cells, or CD34⁺ cells were stained with antibody to NeuN, and the number of total neurons in the left cortex was counted. (E) The average number of total NeuN⁺ cells in the left cortex. n = 6 per group; *P < 0.05 versus PBS. (F and G) On day 90 after cell transplantation, mouse CD31 was visualized immuno-histologically in forebrain sections from poststroke animals. Newly formed vascular networks were observed in the expanded cortex. The vascular pattern displayed by these neovessels on the ipsilateral (F, ischemic side) was different from that observed on the contralateral side (G). (H) On day 90, human CD31 was visualized immunohistologically. Human endothelial cells were observed in the regenerating cortex of animals treated with CD34⁺ cells after stroke. The arrowhead shows a human CD31⁺ endothelial cell. Scale bars: 50 μm (A), 100 μm (F and G), and 20 μm (H).