Optimal temporal delivery of bone marrow mesenchymal stem cells in rats with myocardial infarction

Objective: This study was designed to determine the optimal time point for bone marrow mesenchymal stem cell (MSC) transplantation after myocardial infarction (MI). Methods: MSCs from donor rats were labeled with DAPI before transplantation. The animals underwent MI by ligation of left anterior descending coronary artery, and received intramyocardial injection of MSCs at 1 h, 1 week and 2 weeks after MI, respectively. Sham-operated and MI control groups received equal volume phosphate buffered saline. Cardiac function, histological analysis and immunoblot for troponin T were performed 4 weeks after cell transplantation. Results: MSC transplantation attenuated left ventricular chamber dilation, reduced infarct size, and improved cardiac function in rats after MI. The greatest benefit was achieved in rats that received cells 1 week after MI, engrafted MSC survival, angiogenesis and functional cardiomyocytes in the injured hearts were more abundant in these rats than that in other transplantation groups. Conclusions: The optimal functional benefit of MSC transplantation was observed in 1-week transplantation group. At this time point scar formation has not occurred and the inflammation is reduced, which should facilitate integration of transplanted cells and functional recovery. (c) 2007 European Association for Cardio-Thoracic Surgery. Published by Elsevier B.V. All rights reserved.