Improved rat spinal cord injury model using spinal cord compression by percutaneous method

Abstract

Here, percutaneous spinal cord injury (SCI) methods using a balloon catheter in adult rats are described. A balloon catheter was inserted into the epidural space through the lumbosacral junction and then inflated between T9-T10 for 10 min under fluoroscopic guidance. Animals were divided into three groups with respect to inflation volume: 20 μL (n = 18), 50 μL (n = 18) and control (Fogarty catheter inserted but not inflated; n = 10). Neurological assessments were then made based on BBB score, magnetic resonance imaging and histopathology. Both inflation volumes produced complete paralysis. Gradual recovery of motor function occurred when 20 μL was used, but not after 50 μL was applied. In the 50 μL group, all gray and white matter was lost from the center of the lesion. In addition, supramaximal damage was noted, which likely prevented spontaneous recovery. This percutaneous spinal cord compression injury model is simple, rapid with high reproducibility and the potential to serve as a useful tool for investigation of pathophysiology and possible protective treatments of SCI in vivo.

Keywords: balloon compression; laminectomy-free; magnetic resonance imaging; percutaneous spinal cord injury; rat.

Fig. 1

Details regarding the SCI procedure. (A) A spinal needle was placed between the lumbosacral junction and a balloon catheter was inserted into the epidural space through a spinal needle. The balloon was inflated to a volume of 20 µL (B) or 50 µL (C) using half-strength iohexol.

Fig. 2

Locomotor function after SCI graded based on modified BBB scores. Data points represent the group mean ± SEM. After 1 week, all intergroups revealed a significant difference (p < 0.05).

Fig. 3

MRI results at 1 week after SCI. Transverse T2-weighted image (A) and T1-weighted images (D) of a control group rat showing normal spinal cord parenchyma, central canal and cerebrospinal fluid. Transverse T2-weighted images of the center of a lesion from a rat in the 20 µL group (B) and the 50 µL group (C) showing a completely hyperintensity signal in spinal cord parenchyma. Transverse T1-weighted images of the center of a lesion in a rat of the 20 µL group (E) and the 50 µL group (F) showing a hyperintense to isointense signal in the spinal cord parenchyma.

Fig. 4

Observations from the 50 µL group of rats. (A) Transversal section of the margin of the lesion of the 50 µL group stained with H&E revealing cavitation and glial scar formation of the dorsal funiculus. Scale bar = 500 µm. (B) Transverse T2-weighted images of the margin of the lesion of the 50 µL group showing a wedge-shaped hyperintensity signal in the dorsal part.

Fig. 5

Histopahological findings for the horizontal section in Control (A), 20 µL (B) and 50 µL (C) groups stained with H&E at 4 weeks after SCI. In the control group there was no lesion, while the 50 µL group showed a more severe lesion than the 20 µL group.

Fig. 6

Histopahological findings at the injured epicenter in 20 µL (A~C) and 50 µL (D~F) groups 4 weeks after SCI. In the 20 µL group, the Luxol Fast blue/Cresyl violet stained section (A) revealed complete loss of gray matter, whereas the white matter remained partially present. The Masson Trichrome stained section (B) showed blue-stained fibrosis containing collagen. (C) Higher-magnification view of the red-outlined area. In the 50 µL group, the Luxol Fast blue/Cresyl violet stained section (D) revealed the complete loss of gray and white matter, while the Masson Trichrome stained section (E) revealed blue-stained fibrosis containing collagen. (F) Higher-magnification view of the red-outlined area. Scale bars = 500 µm.

Fig. 7

Assessed area of a lesion in a 10 mm long section of contused spinal cord. Lesion areas of the 20 µL and 50 µL groups were measured and found to differ significantly. The difference in the first and fourth weeks was not significant. Columns represent the group mean ± SEM. ^*Significant differences (p < 0.05).