Therapeutic Window for Cardioprotection by Recombinant Human Erythropoietin (rhEPO) in the Rat Model of Ischemia-Reperfusion: Implications for Clinical Trial Design

Abstract

BackgroundProtection of the heart from ischemic damage by rhEPO had been proven in animal myocardial infarction (MI) models. Recent clinical trials testing the effect of rhEPO following PCI have failed to demonstrate either reduction of MI size, or functional improvement. In the US, the time between the onsets of the symptoms and PCI averages about 2 hrs. Legal requirement for informed consent results in further delays of experimental intervention. For instance, in HEBE trial the rhEPO was injected, on average, 3 hrs after successful PCI, in REVEAL trial the time exceeded 4 hrs. We tested the validity of this clinical design in the rat MI model.MethodsIn five groups of 2-month old male Wistar rats, the left descending coronary artery was occluded either by a permanent or by a temporary ligature. After 2 hrs of occlusion, temporary ligatures were released and coronary perfusion was restored. rhEPO (3000U/kg) or saline were injected intraperitoneally either immediately after reperfusion, or 4 hours after reperfusion, or 6 hrs after permanent coronary occlusion. 24 hrs following coronary occlusion rats were euthanized and MI size was measured histologically.ResultsMI size (42 ± 2% of the area at risk in untreated animals) was significantly smaller (19 ± 2% of the area at risk, p<0.0001) in animals treated by rhEPO at the beginning of reperfusion, but was not altered by rhEPO given 4 hrs after beginning of reperfusion or 6 hrs after permanent coronary occlusion.Conclusion BackgroundProtection of the heart from ischemic damage by rhEPO had been proven in animal myocardial infarction (MI) models. Recent clinical trials testing the effect of rhEPO following PCI have failed to demonstrate either reduction of MI size, or functional improvement. In the US, the time between the onsets of the symptoms and PCI averages about 2 hrs. Legal requirement for informed consent results in further delays of experimental intervention. For instance, in HEBE trial the rhEPO was injected, on average, 3 hrs after successful PCI, in REVEAL trial the time exceeded 4 hrs. We tested the validity of this clinical design in the rat MI model. Protection of the heart from ischemic damage by rhEPO had been proven in animal myocardial infarction (MI) models. Recent clinical trials testing the effect of rhEPO following PCI have failed to demonstrate either reduction of MI size, or functional improvement. In the US, the time between the onsets of the symptoms and PCI averages about 2 hrs. Legal requirement for informed consent results in further delays of experimental intervention. For instance, in HEBE trial the rhEPO was injected, on average, 3 hrs after successful PCI, in REVEAL trial the time exceeded 4 hrs. We tested the validity of this clinical design in the rat MI model. MethodsIn five groups of 2-month old male Wistar rats, the left descending coronary artery was occluded either by a permanent or by a temporary ligature. After 2 hrs of occlusion, temporary ligatures were released and coronary perfusion was restored. rhEPO (3000U/kg) or saline were injected intraperitoneally either immediately after reperfusion, or 4 hours after reperfusion, or 6 hrs after permanent coronary occlusion. 24 hrs following coronary occlusion rats were euthanized and MI size was measured histologically. In five groups of 2-month old male Wistar rats, the left descending coronary artery was occluded either by a permanent or by a temporary ligature. After 2 hrs of occlusion, temporary ligatures were released and coronary perfusion was restored. rhEPO (3000U/kg) or saline were injected intraperitoneally either immediately after reperfusion, or 4 hours after reperfusion, or 6 hrs after permanent coronary occlusion. 24 hrs following coronary occlusion rats were euthanized and MI size was measured histologically. ResultsMI size (42 ± 2% of the area at risk in untreated animals) was significantly smaller (19 ± 2% of the area at risk, p<0.0001) in animals treated by rhEPO at the beginning of reperfusion, but was not altered by rhEPO given 4 hrs after beginning of reperfusion or 6 hrs after permanent coronary occlusion. MI size (42 ± 2% of the area at risk in untreated animals) was significantly smaller (19 ± 2% of the area at risk, p<0.0001) in animals treated by rhEPO at the beginning of reperfusion, but was not altered by rhEPO given 4 hrs after beginning of reperfusion or 6 hrs after permanent coronary occlusion. Conclusion