Morphologic analysis of spinal cord ischemia ‐ reperfusion injury caused by aortic cross clamping in a rat model

Abstract

BackgroundSpinal cord ischemia and paralysis of lower extremities are devastating postoperative complications that accompany surgery of aortic aneurysm. Spinal cord ischemia ‐ reperfusion injury (I/R) results in overproduction of reactive species leading to tissue oxidative stress, which impact the neuronal network in spinal cord as well as supporting white matter cells. Here, we report the longitudinal analysis of activity and number of neurologic cells in the area of aortic clamping.MethodsTransient aortic occlusion was produced in rats by cross – clamping of the abdominal aorta for 45 minutes. Animals were sacrificed at several time points after reperfusion; 1, 6 and 48h; to determine time correlated changes in activity and number of neurologic cells in spinal cord. Spinal cord tissue was analyzed by immunofluorescence using specific primary antibodies, glial fibrillary acid protein (GFAP) and NeuN. Also, we wondered whether survival of neurons was related to their expression of nuclear factor erythroid 2‐related factor 2 (Nrf2), an oxidative stress protective protein.ResultsIn the present study, ischemia – reperfusion injury of spinal cord was manifested by moderate loss of neurons in dorsal horn after 6h of reperfusion, and significant loss of neurons in dorsal horn after 48h of reperfusion compared to sham animals. Neurons located ventrally and laterally indicated no change in number. Surviving neuron cells, howerver, showed expression of Nrf2 with its nuclear translocation escpecially pronounced in neurons located in ventral horn. Longitudinal analysis of neuronal number showed that loss of neurons in dorsal horn was limited to lumbar part of spinal cord. Analysis of GFAP positive cells revealed moderate increase in number 6h post reperfusion in lateral part of spinal cord, while 48h post reperfusion this increase was even more pronounced compared to sham animals. Increase of number of GFAP positive cells was followed with astrocyte activation in lateral part of spinal cord presented as increased GFAP positive area in the same part of spinal cord. Longitudinal analysis of spinal cord revealed that astrocyte activation is present even in thoracic parts of spinal cord, higher than segments which were targeted by aortal clamping.ConclusionOur data indicate that I/R spinal cord injury induces changes in number of GFAP and NeuN positive cells and these changes correlate to duration of reperfusion time. The surviving neurons express Nrf2 in their nucleus, which shows the involvement of Nrf2 pathway in neuron survival.Support or Funding InformationGrant approved and financed by Faculty of Medicine University of Rijeka