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Figure 2 Effect of treating mesenchymal stem cells (MSCs) with hypoxia-inducible hHO-1 vector on grafted cell survival in ischemic myocardium. (A and B) Quantification of intramyocardial terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate in situ nick end labeling-positive graft cells two weeks after MSC injection. TUNEL-positive implanted cells were significantly less in MSC_HO-1 group compared with the MSC_LacZ and MSCs group (p < 0.01, n = 6/group). (C) Immunofluorescent staining of hHO-1 to detect the expression of hypoxia-regulated gene in ischemic myocardium four days after implantation. The number of HO-1-positive graft cell was higher in the MSC_HO-1 group than the MSC_LacZ groups. (D) At the peri-infarct area, donor MSC_LacZ stained positively for LacZ marker gene, indicating the ischemia-activated LacZ gene in MSC_LacZ. Arrows indicate the ß-gal nuclei.