Abstract 2838: Bone Marrow Mesenchymal Stem Cells Differentiated into Beating Cardiomyocytes In Vivo and Improved Myocardial Function

Background: In settings of heart failure, infusion of bone marrow mesenchymal stem cells (MSCs) improves myocardial function both in experimental and clinical studies. The mechanism by which MSCs improve myocardial function remains unknown. Hypothesis: MSCs may differentiate into beating myocytes in vivo. The contractility of these cells is comparable with those of myocytes. Methods: A thoracotomy was performed in 10 male Sprague-Dawley rats, weighing 350 – 450g. Myocardial infarction was induced by ligation of the left anterior descending artery (LAD). One week later, animals were randomized to receive 5×10 6 MSCs marked with PKH26 in phosphate buffer solution (PBS) or as a PBS bolus injection into local infarcted myocardium. Six weeks after the MSCs or PBS injection, the hearts were harvested and digested with collagease type II and single cardiomyocytes were obtained. PKH26 labeled myocytes differentiating from MSCs were observed with a microscope Olympus I×71. The contractility of labeled and unlabeled beating cells in MSCs-treated animals was compared. The contractility of unlabeled myocytes was compared between MSCs-treated and control groups. Result: The beating fluorescent labeled myocytes can be found in MSCs-treated animals [(1.2±0.4) ×10 6 ] and contractility of these cells were the same as that of unlabeled beating myocytes (Table 1 ). The contractility of unlabeled myocytes, however, was significantly better in MSCs-treated animals. Conclusion: MSCs could differentiate into the beating myocytes. However, this may not be the sole mechanism of improved myocardial function. Table 1 Cells contractility (%)