MDSC implanted in the MI area survived after 4 weeks and reduced the apoptotic index, in a process stimulated by sildenafil that also partially counteracted the cardiomyocyte loss. (n = 7/group). Top: representative picture of frozen sections from MI regions that received DAPI-labeled MDSC, visualized with blue (DAPI) and red (Texas red) fluorescence filters for implanted nuclei and troponin-T stained cardiomyocytes, respectively. Arrows: cardiomyocyte/MDSC nuclei overlapping. Middle and lower panels: quantitative image analysis by Troponin T and TUNEL (apoptosis) immuno-histochemistry in paraffin-embedded sections, respectively. Abbreviations as in Figure 4. Statistical differences are stated for untreated versus basal, and MDSC, and MDSC + sildenafil versus untreated; *p < 0.05; **p < 0.01;***p < 0.005.