Background
: Experimental studies showed that application of expanded endothelial progenitor cells (eEPC) after myocardial infarction improves cardiac function by enhancing vasculogenesis and by paracrine effects. Erythropoietin beta (EPO) could further improve myocardial function through its anti-apoptotic properties.
Methods
: Acute myocardial ischemia was induced by ligation of the left anterior descending coronary artery of 23 male athymic nude rats and reperfusion was initiated after 30 minutes. Either 1×10^6 eEPC alone (n=8), 50 IU erythropoietin beta alone (n=7) or eEPC and EPO (n=8) were injected intramyocardially into the border zone of the ischemic area. eEPC were attained by expanding CD34+ cells isolated from cord blood in endothelial medium for 6 –10 passages. A control group did not receive cells or erythropoietin (n=5). After 4 weeks global and regional left ventricular function was measured by MRI in 2- and 4-chamber long-axis series (Philips Achieva MR Scanner). Immunhistology was used to determine vessel densitiy (SMC actin) and infiltrating monocytes (CD68) after 3 days (n=15) and 4 weeks.
Results
: Global left ventricular function after 4 weeks was higher in rats that received eEPC alone (58±3%, p=.02) or eEPC + EPO (58±6%, p=.01) compared to the control group (54±5%). No changes were found for rats treated with EPO alone (52±4%). Analysis of the regional wall movement showed a further improvement of the movement of the antero-lateral segments only in rats that obtained eEPC + EPO. The number of CD68+ mononuclear cells after 3 days was highest in rats that were treated with eEPC + EPO. This was associated with an increase in vessel density after 4 weeks. In vitro experiments revealed a dose-dependent inhibition of apoptosis by EPO in eEPC.
Conclusion:
Intramyocardial transplantation of eEPCs + EPO further improved anterolateral wall motion as compared to EPC alone. Improved eEPC survival, alterations in local inflammatory responses and neovascularization may contribute to this effect.
Exercise training after anterior Q wave myocardial infarction: Importance of regional left ventricular function and topography
