BACKGROUND: Expanded endothelial progenitor cells (eEPC) improve global left 
ventricular function in experimental myocardial infarction (MI). Erythropoietin 
beta (EPO) applied together with eEPC may improve regional myocardial function 
even further by anti-apoptotic and cardioprotective effects. Aim of this study 
was to evaluate intramyocardial application of eEPCs and EPO as compared to 
eEPCs or EPO alone in experimental MI.
METHODS AND RESULTS: In vitro experiments revealed that EPO dosed-dependently 
decreased eEPC and leukocyte apoptosis. Moreover, in the presence of EPO mRNA 
expression in eEPC of proangiogenic and proinflammatory mediators measured by 
TaqMan PCR was enhanced. Experimental MI was induced by ligation and reperfusion 
of the left anterior descending coronary artery of nude rats (n = 8-9). After 
myocardial transplantation of eEPC and EPO CD68+ leukocyte count and vessel 
density were enhanced in the border zone of the infarct area. Moreover, 
apoptosis of transplanted CD31 + TUNEL + eEPC was decreased as compared to 
transplantation of eEPCs alone. Regional wall motion of the left ventricle was 
measured using Magnetic Resonance Imaging. After injection of eEPC in the 
presence of EPO regional wall motion significantly improved as compared to 
injection of eEPCs or EPO alone.
CONCLUSION: Intramyocardial transplantation of eEPC in the presence of EPO 
during experimental MI improves regional wall motion. This was associated with 
an increased local inflammation, vasculogenesis and survival of the transplanted 
cells. Local application of EPO in addition to cell therapy may prove beneficial 
in myocardial remodeling.