Cardioprotection by recombinant human erythropoietin following acute experimental myocardial infarction: Dose response and therapeutic window

Background: Recombinant human erythropoietin (rhEPO) protects tissue from ischemic damage, but translation of this finding into useful guidelines with respect to human trials for myocardial infarction (MI) requires a determination of the minimum effective rhEPO dose and the therapeutic window following MI. Method and Results: Serial echocardiography revealed that during four weeks following MI, induced by a permanent coronary ligation in rats, the LV end-diastolic and end-systolic volumes in untreated rats expanded from 0.35 ± 0.01 and 0.14 ± 0.01 ml to 0.84 ± 0.04 and 0.61 ± 0.06 ml, respectively, and ejection fraction (EF) reduced by 50%. A single i.v. injection of rhEPO immediately following MI in a dose of 150 IU/kg was as effective as 3000 IU/kg in causing a 2-fold reduction of the number of apoptotic nuclei in the AAR 24-h later, a 2-fold reduction of the MI size measured 4 weeks later, attenuation of progressive LV dilatation and fall in EF. A 3000 IU/kg dose had similar therapeutic effects when delayed by 4, 8, or 12 h following MI, but was not effective after a 24-h delay. A single dose of 150 IU/kg was effective within 4 h post-MI, but was without effect if administered after an 8-h delay. Conclusion: Cell death, final MI size, myocardial remodeling and functional decline are significantly reduced in rats by a single injection of rhEPO in a dose as low as 150 IU/kg if administered during the first 4 h after the ischemic event. Higher doses extend the therapeutic window up to 12 h.