Establishing a Mouse Contusion Spinal Cord Injury Model Based on a Minimally Invasive Technique

Minimally invasive techniques reduce the currents of instability, caused by excess physics damage. Cultivating to analyze spinal cord microenvironment precisely. This technique combines Alan's classical withdrawal principle with accuracy operation procedure to establish a reproducible spinal cord injury model.

The main focus of this protocol is to become familiar with the anatomical structure. Which is easier to follow even for sophomore like me. Demonstrating the procedure will be Xiangchuang Fan A postgraduate from Qilu Hospital, Zhongze Yuan and Zimeng Yang.

Both undergraduates from Shandong University Cheeloo College of Medicine. To begin assemble the platform with a surgical operating table over a t-bral stabilizer, and an impactor tip. Put the tip, which allows for accurate spinal cord locating into the sleeve.

Select proper masses of the weight drops for the experiment, which are 1.3, 2.0, and 2.7 grams for the mild, moderate and severe groups respectively. Plug the pull pin into the holes of the weight drop. Assemble the weight drop to the top of the sleeve with the pull pin fitted in the groove on the XYZ arm, so that once the locating is complete the weight is released to strike the impactor tip.

Consequently, contusing the spinal cord, and changes in the spinal cord are observed under the microscope. Lay the mouse in a prone position in a designated part of the operating table. Explore the 13th rib on one side from the bony portion, under the operating microscope.

Explore the spinous process in the midline by lightly touching the area of the costovertebral angle and then toward the rostral to locate the interspinous space between the 12th and 13th thoracic vertebrae. Explore the interspinous space between the 9th and 10th thoracic vertebrae from the space of the 12th and 13th thoracic vertebrae to the rostral side. Dissect the paraspinal muscle along the spinous process of the T9 to the anterior and posterior facet joints of both sides with micro scissors.

Retract the paraspinal muscles with micro retractors and clean the soft tissue on the lamina, and in the inters spinous space of the T8 to T9, and T9 to T10, with micro scissors. To perform T9 laminectomy, clamp the spinous process of T9 with microsurgery forceps. Slightly lifted up insert the micro scissors parallelly, along the right dorsal lateral side of the lamina.

Avoiding damage to the spinal cord, and cut off the lamina with micro scissors. Repeat on the left side and the spinal cord can be exposed. Before fixing the vertebra, loosen the universal arm, and slowly clamp the 9th to 10th facet joints on both sides of the vertebra with the micro mosquito forceps of the vertebral stabilizer.

Tighten the screws on the micro mosquito forceps, and the vertebra is thus stabilized. Adjust the spinal cord to the horizontal plane. Tighten the universal arm and the vertebra is fixed.

Once the T9 level spinal cord is exposed, and the vertebra is fixed, aim at the spinal cord by the tip inside the sleeve under the operating microscopic. After locating the interspinous space of the T12 to T13, lower the sleeve until the end of the impactor is consistent with the mark on the observation window, and the specified height of 22 millimeter is reached. Pull out the pull pin to release the weight.

Remove the impactor when the contusion is done and observe the degree of spinal cord injury under the operating microscope. In the mild group, the light red color alteration can be seen while in the moderate group. The injury sight exhibits dark red in three to four seconds, and possibly eminence can be observed.

In the severe group, the dark red manifestations may appear immediately, and obvious eminence in the dura is manifested, but the dura is still in a consistent shape. The area of lesion, gradually increased significantly from the mild to severe groups on the first day post-injury. Meanwhile, the continuity of white matter on both sides of the spinal cord was better in the mild group.

With observable small round vacuoles, which are the characteristics of interstitial edema. In the moderate group, the white matter displayed poor continuity, and the structure of the ventral white matter was not ordered. In the severe group, the ventral white matter exhibited more severe disruption, and a large area of the cavity appeared in the center of the injury.

Additionally, the surrounding tissue showed obvious filling of the red blood cells, and the red blood cells near the central canal gathered into strips. Overlapping scar forming astrocytes were visible in the center of all three groups of injuries. With the length of the injury area, increasing with the severity of the injury, while the scar diameter decreased.

This, suggests the presence of scar contracture, which may lead to a decrease in spinal cord diameter. Removing the soft tissues in front of and behind the lamina as much as possible facilitates lamina relaxation, and prevents damage to the spinal cord when parallely cutting. The present technique provides an animal model that is simple, reproducible and less invasive.

post-traumatic spinal cord injury especially contusion injury.