Effects of bone marrow mesenchymal stem cells in a rat model of myocardial infarction

Infusion of bone marrow mesenchymal stem cells (MSCs) improves myocardial function following myocardial infarction (MI). The mechanisms, however, remain controversial. This study was to investigate changes of MSCs in vivo after administration into myocardial infarcted rats. Our hypothesis was that MSCs might differentiate into contractile myocytes and improve myocardial function in vivo.

MI was induced in 21 Sprague-Dawley rats by ligation of the left anterior descending artery. One week after ligation, 18 rats were randomized to receive MSCs labeled with PKH26 in a phosphate buffer solution (PBS) by direct injection into the infarcted myocardium. The remaining 3 rats received PBS alone as placebo. An additional 3 non-ligated rats served as a normal group to obtain normal myocytes.

Every week for 6 weeks, hearts from 3 rats injected with MSCs were harvested to observe single cardiomyocytes. Although each week numerous round MSCs were found in the hearts of animals treated with MSCs, beating cardiomyocyte-like cells labeled with PKH26 were observed at the sixth week. The contractility of cardiomyocyte-like cells was the same to that of the unlabeled contractile native cardiomyocytes at the sixth week and that of the normal group (10.71±1.59 vs. 11.09±3.42 vs. 11.21±2.16, p>0.05). The contractility of cardiomyocyte-like cells was greater than cells both from the first week (10.71±1.59 vs. 7.37±3.47, p<0.01) and the second week (10.71±1.59 vs. 8.08±3.11, p<0.05) which was associated with significantly increased ejection fraction.

MSCs can differentiate into beating cardiomyocytes in a rat model of MI and improve myocardial function.