Study design. (A) Safety studies: the primary focus of the study was to investigate potential adverse cardiovascular effects of umbilical cord blood mononuclear cells transplantation in the right ventricle of mouse heart. A dose escalation study was carried out to assess the possible side effects and estimate the dosage likely to be the safety margin of UCB-MNCs. (B) Efficacy studies: the second part of the study was designed to explore the possible beneficial effects involved in right ventricular remodeling upon intramyocardial injection of UCB cells in a disease model with pressure overload right heart failure. MNCs, mononuclear cells; UCB, umbilical cord blood.