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Figure 5 Cardiac stem cells (CSCs) and myocardial regeneration after infarction. The intramyocardial injection of enhanced green fluorescent protein (EGFP)-positive CSCs in syngeneic rats acutely after infarction induced the formation of myocardium. The new myocytes express alpha-sarcomeric actin (A, red) and EGFP in the cytoplasm (B, green). (C) The merged images of A and B. The regenerated myocytes show both -sarcomeric actin and EGFP (yellow-green). Nuclei are labeled by propidium iodide (blue). (D) The formed myocytes are small and carry at most two chromosomes 12 (green dots). Therefore, myocyte regeneration does not involve cell fusion. Laminin is distributed between myocytes (white lines). (E, F) Regenerated coronary arterioles that are positive for alpha-smooth muscle actin and EGFP (yellow-red). *Spared myocytes in the subendocardium. EP = epicardium; EN = endocardium.