We previously showed that erythropoietin (EPO) attenuates the morphological signs of spinal cord ischemia/reperfusion (I/R) injury in swine [1] without, however, improving neurological function. The clinical use of EPO has been cautioned most recently due to serious safety concerns arising from an increased mortality in acute strokepatients treated with EPO and simultaneously receiving systemic thrombolysis [2]. Carbamylated EPO (cEPO) is an EPO derivative without erythropoietic activity and devoid of the EPO side effects, but with apparently well maintained cytoprotective qualities [3]. We therefore tested the hypothesis whether cEPO may be equally efficient as EPO in reducing morphological as well as functional aortic occlusion-induced spinal cord I/R injury.
Methods
In a randomized and blinded trial pigs received either vehicle(control, n = 9), EPO or cEPO, respectively (n = 9 each; 5,000 IU/kg over 30 minutes before and during the first 4 hours of reperfusion). Animals underwent 30 minutes of thoracic aortic balloon occlusion with catheters placed immediately downstream of the A. subclavia and upstream of the aortic trifurcation. Spinal cord function was assessed by motor evoked potentials (MEP as percentage of the amplitude before aortic occlusion) and lower limb reflexes (assessed as the subjective strength of response) for a period of 10 hours after reperfusion. Tissue damage was evaluated using Nissl staining.
Results
Both EPO-treated and cEPO-treated animals presented with attenuated spinal cord injury in the Nissl staining (median (quartile) percentage of damaged neurons in the thoracic segments: control 27 (25,44), cEPO 8 (4,10), and EPO 5 (5,7), P < 0.001 vs control group; in the lumbar segments: control 26 (19,32), cEPO 7 (5,13), EPO 8 (5,10), P < 0.001 vs control group). However, while only cEPO treatment was associated with recovery of the MEP amplitude to pre-occlusion values when compared with the control group (P < 0.05), lower limb reflex response was comparably restored stronger in both treatment groups (P < 0.05 vs control).
Conclusions
In a clinically relevant porcine model mimicking aortic cross-clamping during vascular surgery repair of thoracic aortic aneurysm, cEPO protected spinal cord function and integrity as effective as EPO when applied at equipotent doses.