No detectable risk of cardiovascular toxicity from UCB-MNCs delivered into the myocardium of the right ventricle. (A) Echocardiographic images three weeks after UCB-MNC transplantation indicating normal cardiac function and no signs of tumor formation in any of the doses. A comparison (0.2 million (low dose) to 0.8 million cells (high dose)) of echocardiography was performed in this study. (B) Histo-pathological sections stained with hematoxylin & eosin (H & E) three weeks after RV myocardial injection. Short-axis sections were used to identify the area of injection. Higher magnification images were captured at x100. UCB-MNC transplantations showed no incidence of lesion in the RV and no signs of tumor formation upon histological examination in any animals. (C) Heart sections stained with Masson Trichrome stain (blue) after myocardial injection of UCB-MNCs. The average ratio of fibrosis area per RV area was measured to determine the fibrotic area. N = 4, Scale bars = 200 μm. RV, right ventricle; UCB-MNCs, umbilical cord blood-mononuclear cells.