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Figure 5 Endogenous Cardiomyocyte Proliferation and Apoptosis

(A and B) Proliferating cardiomyocytes within the peri-infarct region were identified by colocalization of both Ki-67 (purple nuclear stain, arrow) and cardiac troponin I (cTnI) (brown cytoplasmic stain) within the peri-infarct region (arrow). Some of the proliferating cells stained by Ki-67 exist within the infarct zone, but do not colocalize with cTnI (arrowhead). Scale bars = 50 µm. (C) The number of endogenous proliferating cardiomyocytes was higher in the peri-infarct region of the heart injected with CD56⁺CD34⁺CD144⁺ cells compared with that seen in other groups at both 5 days and 6 weeks after cell transplantation (*p < 0.05, CD56⁺CD34⁺CD144⁺ cells vs. CD56⁺CD34^–CD144^– cells, CD56^–CD34⁺CD144⁺ cells, and phosphate-buffered saline [PBS]). (D) The number of apoptotic cardiomyocytes was measured at both 5 days and 6 weeks after myocardial infarction (p < 0.05, CD56⁺CD34⁺CD144⁺ cells vs. PBS). HPF = high-power fields; TUNEL = terminal dUPT nick end-labeling.