Vascular density in the infarct zone of NOD/SCID β2m null mice with AMI four weeks after transplantation of ALDHlo Lin- or ALDHhi Lin- sorted human UCB cells. NOD/SCID β2m null mice with AMI were transplanted with ALDHloLin- or ALDHhiLin- sorted human UCB cells or PBS. Frozen sections were stained with a mouse specific CD31 antibody and visualized with DAB+ chromagen. Ten high power fields were recorded from each heart (PBS: n = 12; ALDHloLin-: n = 5; ALDHhiLin-: n = 9) in the tissue sub served by the infarct related injury. Representative CD31 labeling from the infarct zone of an ALDHhiLin- or ALDHloLin- transplanted animal are shown in (A) and (B), respectively. Arrows point to representative CD31 stained structures that were excluded (open arrows) or included (solid arrows) in the estimation of vascular density. See text for further explanation. Nuclei: blue, CD31: brown. Scale bar represents 50 μm.