Bone marrow-derived cells incorporate into the repairing vasculature in the injured brain. Stab injury to the brain was performed on Swiss mice. Zero to 12 days after injury the mice were injected intravenously with FITC-labeled albumin and perfused with PBS 10 minutes after injection. Sections through the area of brain injury show leakage of FITC-labeled albumin from the vasculature that is no longer evident by day 12 (A). Bone marrow transplantations were performed on SCID mice using marrow from FVB/N-TgN (Tie2-LacZ)182 Sato mice that express β-galactosidase specifically in endothelial cells. One month after transplantation, stab injury of the brain was performed. Three to 5 days after the injury the animals were killed and sections through the injured area were stained with anti-β-galactosidase (green) and the endothelial marker CD31 (red). Fluorescence microscopy shows incorporation of β-galactosidase-expressing cells into the repairing vasculature. Scale bars represent 20 mm (B) and 100 mm (C).