Delayed and selective motor neuron death after transient spinal cord ischemia: A role of apoptosis?

Objective: The mechanism of spinal cord injury has been thought to be related to tissue ischemia, and spinal motor neuron cells are suggested to be vulnerable to ischemia. We hypothesized that delayed and selective motor neuron death is apoptosis. Methods: Thirty-seven Japanese domesticated white rabbits weighing 2 to 3 kg were used in this study and were divided into two subgroups: a 15-minute ischemia group and a sham control group. Animals were allowed to recover at ambient temperature and were killed at 8 hours, and 1, 2, 4, and 7 days after reperfusion (n = 3 at each time point). By means of this model, cell damage was histologically analyzed. Detection of ladders of oligonucleosomal DNA fragment was investigated with ge electrophoresis up to 7 days of the referfusion. Immunocytochemistry, in situ terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick- end labeling staining was also performed. Results: After 15 minutes of ischemia most of the motor neurons showed selective cell death at 7 days of reperfusion. Typical ladders of oligonucleosomal DNA fragments were detected at 2 days of reperfusion. Immunocytochemistry showed in in situ terminal deoxynucleotidyl transferase-mediated deoxyuridine triphosphate-biotin nick- end staining was detected at 2 days of reperfusion selectively in the nuclei of motor neurons. Conclusion: These results suggest that delayed and selective death of the motor neuron cells after transient ischemia may not be necrotic but rather predominantly apoptotic.