Objective
Although hypothermia is known to have a neuroprotective effect on brain injuries as well as to decrease intracranial pressure, the neuroprotective effect in spinal cord injury(SCI) has not been proven. The author performed this experiment to evaluate the effect of systemic hypothermia on neurological improvement and histopathological change in traumatic SCI of rat.
Methods
In experiment I, spinal cord contusions were implemented in 35 rats that had been divided into 3 groups. Rats in Group 1(N=12) were kept with normothermia, while Group 2(N=10) received hypothermic treatment for 5 hours and Group 3(N=13) for 20 hours. The experiment was held over two weeks and clinical assessment of locomotor function was made by utilizing the Basso-Beattie-Bresnahan(BBB) locomotor rating scale. Histopathological studies were performed at 2 weeks by hematoxylin & eosin, luxol fast blue and TUNEL staining. To analyze the effect of hypothermia for 20 hours on apoptosis, the author evaluated histopathological findings 3 days after SCI in experiment II. Eighteen rats with SCI in experiment II, were kept with normothermia in Group 4(N=9) and treated by hypothermia for 20 hours in Group 5(N=9). The spinal cords were excised and stained 3 days after SCI.
Results
Fourteen days after SCI, BBB scales in Group 1(N=9), Group 2(N=9), and Group 3(N=13) were 7.9±2.8, 10.0±3.2, 13.9 2.5, respectively, which were statistically significant(ANOVA, p=0.001). The area of spinal cord tissue defect in Group 1, Group 2 and Group 3 after 2 weeks were decreased gradually, which were 4.1 2.0 mm2, 2.9 1.9 mm2, 2.0 1.9 mm2, respectively, but statistically insignificant(ANOVA, p=0.064).
In experiment II, the sizes of necrotic areas in Group 4 and Group 5 were 5.9±2.2 mm2, 3.8±2.3 mm2, respectively, which were not statistically significant(p=0.074). However, the ratio of TUNEL staining positive cells decreased significantly in Group 5(p=0.015). The ratios were 0.30±0.10 in group 4 and 0.16±0.12 in group 5.
Conclusion
In this study, systemic hypothermia for 20 hours improved neurological recovery and decreased the ratio of apoptosis in traumatic SCI of rat. In addition, hypothermic treatment showed a tendency of reducing necrosis and tissue defect after SCI.
