Construction and evaluation of a moderate contusion model of thoracic spinal cord injury in mice

English Keywords:Spinal cord injury  Animal model  Mouse  3D gait analysis

English Abstract:

  【Abstract】 Objectives: To establish a bilateral moderate contusion thoracic spinal cord injury mouse model and dynamically assess the pathophysiological functions. Methods: 28 specific pathogen-free(SPF) female C57BL/6 mice aged 8-10 weeks were randomly divided intoⅠ-Ⅳ groups, among which, groupⅠreceived no impact and served as the control, groups Ⅱ-Ⅳ received spinal cord impacts at the T10 level using a trauma impactor-Infinite Horizon(IH) with forces of 60, 80, and 100kdyn, respectively. Body weight measurements and Basso Mouse Scale(BMS) scores were recorded immediately following spinal cord injury and on 3, 7, 14, 21, and 28d post-injury to assess the nutritional status and motor function of the mice. Additionally, the gait analysis system and motor evoked potential(MEP) were used on 28d post-injury to quantitatively evaluate motor patterns and electrophysiological changes, after that, spinal cord tissue sampling was performed for hematoxylin eosin(HE) staining and immunofluorescence tests to observe tissue changes. Results: Except for group Ⅳ, the body weight of mice in other groups increased within 28 days, with group Ⅲ showing significantly better recovery in body weight and BMS scores compared to group Ⅳ. Gait analysis indicated that group Ⅱ had superior motor endurance and speed compared to group Ⅲ, demonstrating better motor coordination, but with no significant difference from the control group. HE staining showed the lesion areas in groups Ⅰ-Ⅳ were 0mm2, 0.27±0.05mm2, 0.44±0.10mm2, and 0.67±0.12mm2, respectively, group Ⅲ′s spinal cord structure displayed morphological characteristics similar to the normal state. Immunofluorescence staining for NeuN, GFAP, and MBP revealed gradient changes reflecting varying degrees of injury. In group I, the NeuN-positive neuron count, glial scar/cavity area, and MBP fluorescence intensity were 115.25±13.04, 0μm2, and 1(normalized); In group Ⅱ, the values were 71.00±7.79, 147.02±11.60μm2, and 0.86±0.05; In group III, the values were 51.50±8.89, 175.01±16.28μm2, and 0.76±0.04; In group IV, the values were 16.00±3.37, 212.65±18.64μm2, and 0.55±0.07. Group Ⅲ exhibited well-preserved spinal cord structure, with the extent of glial scarring cavities, neuronal loss, and demyelination showing a controlled gradient. The motor evoked potential(MEP) latencies in groups Ⅰ-Ⅳ were 1.03±0.21ms, 1.31±0.43ms, 1.58±0.80ms, and 1.99±0.74ms, respectively, while the corresponding amplitudes were 0.83±0.06mV, 0.58±0.19mV, 0.46±0.17mV, and 0.37±0.19mV. The latency exhibited a tendency to prolong post-injury, suggesting a significant reduction in nerve impulse conduction velocity, which maybe associated with myelin sheath damage or axonal dysfunction. The amplitude decreased with increasing contusion force, indicating that the excitatory conduction capacity of nerve fibers was impaired progressively as injury severity increased. Conclusions: The bilateral thoracic moderate contusion model of spinal cord injury in mice established with an 80kdyn contusion parameter is effective and reliable, which better reflects the pathophysiological changes following spinal cord injury.