Research ReportErythropoietin promotes neurovascular remodeling and long-term functional recovery in rats following traumatic brain injury

Erythropoietin (EPO) improves functional recovery after traumatic brain injury (TBI). This study was designed to investigate long-term (3 months) effects of EPO on brain remodeling and functional recovery in rats after TBI. Young male Wistar rats were subjected to unilateral controlled cortical impact injury. TBI rats were divided into the following groups: (1) saline group (n = 7); (2) EPO-6 h group (n = 8); and (3) EPO-24 h group (n = 8). EPO (5000 U/kg in saline) was administered intraperitoneally at 6 h, and 1 and 2 days (EPO-6 h group) or at 1, 2, and 3 days (EPO-24 h group) postinjury. Neurological function was assessed using a modified neurological severity score, footfault and Morris water maze tests. Animals were sacrificed at 3 months after injury and brain sections were stained for immunohistochemical analyses. Compared to the saline, EPO-6 h treatment significantly reduced cortical lesion volume, while EPO-24 h therapy did not affect the lesion volume (P < 0.05). Both the EPO-6 h and EPO-24 h treatments significantly reduced hippocampal cell loss (P < 0.05), promoted angiogenesis (P < 0.05) and increased endogenous cellular proliferation (BrdU-positive cells) in the injury boundary zone and hippocampus (P < 0.05) compared to saline controls. Significantly enhanced neurogenesis (BrdU/NeuN-positive cells) was seen in the dentate gyrus of both EPO groups compared to the saline group. Both EPO treatments significantly improved long-term sensorimotor and cognitive functional recovery after TBI. In conclusion, the beneficial effects of posttraumatic EPO treatment on injured brain persisted for at least 3 months. The long-term improvement in functional outcome may in part be related to the neurovascular remodeling induced by EPO.

Research highlights►Erythropoietin (EPO) provides long-term benefits after traumatic brain injury (TBI). ►EPO treatment significantly promotes neurovascular remodeling in TBI rats. ►Increased neurovascular remodeling may contribute to functional recovery.