Establishment of hemi-contusive cervical spinal cord injury model in rats and its characters in function and histology

English Keywords:Cervical spinal cord injury  Unilateral contusion  Forelimb motor function  Rat  Histology

English Abstract:

  【Abstract】 Objectives: To establish a unilateral cervical spinal cord contusion injury model in rats, and to evaluate the behavioral and histological changes with different degrees of cervical spinal cord injury. Methods: Thirty-two male adult Sprague-Dawley rats were divided into 1.2mm group(n=12) defined as moderate injury group, 2mm group(n=12) defined as severe injury group and the control group(n=8), which was based on contusive displacement. The left spinal cord of C5 was exposed under anesthesia. The cervical vertebra was held by custom-made vertebral clamps and connected to the stereo positioning frame. Contusion injuries were applied to the left dorsal cord of C5 by using a 1.5mm-diameter impounder at 500mm/s. The maximum impact force and the contusion energy were recorded. Forelimb motor function was evaluated by using the forelimb locomotor scores, the rearing and grooming tests. All outcome measures were estimated weekly prior to and up to 8 weeks following injury. The spared areas of gray and white matter at the epicenter were analyzed on cross-sections of spinal cord. Results: The peak force and contusion energy were 0.99±0.14N and (1.08±0.01)×10-5J in the moderate group, and 1.53±0.22N and (8.56±0.02)×10-5J in the severe group, respectively. Significant difference was observed in the peak force and contusion energy between groups. No obvious neurological dysfunction was observed in the control group after surgery, and the functional score of forelimbs was 16.29±0.49. There was unilateral neurological dysfunction in the rats of the injury group, and the forelimb function score was 1.40±0.52 in the moderate group and 0.83±0.25 in the severe group. The two experimental groups had no statistical difference(P>0.05). At 8 weeks after injury, forelimb motor function score was 12.40±1.15 in the moderate injury group, 8.41±0.83 in the severe group, 17.00±0.00 in the control group. Grooming test score was 3.80±0.60 in the moderate injury group, 2.51±0.54 in the severe group, 5.00±0.00 in the control group. Proportion of ipsilateral forelimb use was (32.31±5.70)% in the moderate injury group, (4.92±1.21)% in severe group, (49.42±1.20)% in the control group. There were statistical differences among the groups(P<0.05). Unilateral structural failure and cavity were presented in spinal cord at 8 weeks after injury. The moderate contusion caused primarily dorsal column, spinal dorsal horn and part of dorsolateral fasciculus damage while the severe contusion produced additional damage to lateral and ventral tissue, while the structure of spinal cord was intact in the control group. The spared areas of gray and white matter in the moderate group at lesion epicenter were 1.45±0.11mm2 and 4.13±0.29mm2, and in the severe group were 1.10±0.05mm2 and 3.84±0.19mm2 respectively. There was significant difference in the spared areas of gray and white matter between groups(P<0.05). Conclusions: This study successfully establishes a different degree of unilateral cervical spinal cord contusion model in rats, which shows persistent unilateral neurological dysfunction and structural destruction of the injured spinal cord and the motor impairment, and it can be used for basic research of spinal cord injury.