Single high-dose intramyocardial administration of erythropoietin promotes early intracardiac proliferation, proves safety and restores cardiac performance after myocardial infarction in rats☆

Abstract

Various studies demonstrate erythropoietin (EPO) as a cardioprotective growth hormone. Recent findings reveal EPO in addition might induce proliferation cascades inside myocardium. We aimed to evaluate whether a single high-dose intramyocardial EPO administration safely elevates early intracardiac cell proliferation after myocardial infarction (MI). Following permanent MI in rats EPO (3000 U/kg) in MI EPO-treatment group (n=99) or saline in MI control group (n=95) was injected along the infarction border. Intramyocardial EPO injection activated the genes of cyclin D1 and cell division cycle 2 kinase (cdc2) at 24 h after MI (n=6, P<0.05) evaluated by real time-PCR. The number of Ki-67+ intracardiac cells analyzed following immunohistochemistry was significantly enhanced by 45% in the peri-infarction zone at 48 h after EPO treatment (n=6, P<0.001). Capillary density was significantly enhanced by 17% as early as seven days (n=6, P<0.001). After six weeks, left ventricular performance assessed by conductance catheters was restored under baseline and dobutamine induced stress conditions (n=11-14, P<0.05). No thrombus formation was observed in the heart and in distant organs. No deleterious systemic adverse effects were apparent. Single high-dose intramyocardial EPO delivery proved safety and promoted early intracardiac cell proliferation, which might in part have contributed to an attenuated myocardial functional decline.