Carbamylated erythropoietin is neuroprotective in an experimental model of traumatic brain injury

Objective: The well-documented neuroprotective effects of re- combinant human erythropoietin (rhEPO) are commonly associ- ated with untoward erythrocyte-stimulating effects (polycythe- mia), with subsequent risk of thromboembolic complications. A carbamylated-rhEPO (CEPO) derivative, which is neuroprotective but lacks hematopoietic activity, has been recently developed. In this study, we evaluated the neuroprotective capability of CEPO in an in vitro model of cerebral trauma in which rhEPO was previ- ously shown to reduce posttraumatic cell death. Design: Prospective, controlled experiment. Setting: Animal, basic science laboratory. Subjects: Wistar rats, 8 days old. Interventions: Organotypic hippocampal slices, obtained from rat brains, were subjected to a well-characterized model of mechanical injury followed by addition of 10 IU/mL rhEPO, 10–100 IU/mL CEPO, or vehicle (injured control) to the incubation medium at different times to assess the temporal window of therapeutic neuroprotection. Measurements and Main Results: Posttraumatic cell death was quantified at 12, 24, or 48 hrs after injury by measuring propidium iodide fluorescence in the selectively vulnerable CA1 hippocampal area. Posttraumatic injury, observed in injured, vehicle-treated hippocampal slices, was significantly attenuated by addition of either 10 IU/mL rhEPO or 10 IU/mL CEPO. The neuroprotective efficacy of 10 IU/mL rhEPO or CEPO remained intact even when administration was delayed 1 hr after trauma. Qualitative micros- copy in semithin sections showed that both rhEPO and CEPO exerted a marked pyramidal neuron-sparing effect. Conclusion: Our study shows that 10 IU/mL CEPO exerts neu- roprotective effects comparable with those of rhEPO in an in vitro model of mechanical cerebral trauma. Because CEPO lacks he- matopoietic effects and seems to possess a prolonged therapeu- tic time window, this erythropoietin derivative may represent an exciting new pharmacologic tool in treating patients with me- chanical injury to the brain.