Significance of up-regulation of HIF-1α and VEGF expression in angiogenesis after spinal cord injury in rats

Objective: To explore changes of HIF-1α and VEGF expression in neurons and their effect on angiogenesis following spinal cord injury.Methods: Adult Sprague-Dawley rats were divided into two groups randomly:(1) Normal control group(n=5);(2) SCI(spinal cord injury) group(n=25),and this group was further randomly subdivided into five subgroups according to the postoperative survival time,i.e.SCI 1d group,SCI 3d group,SCI 7d group,SCI 14d group and SCI 30d group.Those animals of SCI groups suffered from weight-dropping SCI operation on T12 spinal cord.The expression of HIF-1α and VEGF were examined using immunofluorescence.The density of the Laminin immunoreactive positive vessels of six groups was compared. Results: HIF-1α and VEGF were co-expressed in motoneurons.Their fluorescence intensity at SCI lesion was stronger than that at normal spinal cord,and achieved the top level 3 days after SCI operation.Laminin positive vessels were mainly distributed in the periphery regions of spinal cord lesion,and gradually increased and grew into the central necrotic tissue. Conclusion: At SCI lesion,those undamaged motoneurons may produce more VEGF through the induction of over-expressed HIF-1α,which continued to react with the surrounding vascular endothelial cells at the manner of paracrine to promote cell proliferation and angiogenesis.