Graded Contusion Model of the Mouse Spinal Cord Using a Pneumatic Impact Device

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Abstract
This study examined the effects of varying magnitudes of controlled spinal cord impact to the mouse spinal cord on neurological and histopathological variables to obtain a mouse model of spinal cord injury (SCI). A laminectomy of the T10 vertebra was performed on anesthetized C57BL/6 mice. A pneumatic pressure-driven impact was performed on the spinal cord through the dura mater. Experimental groups were subdivided according to the energy of impact (0.25-mm-deep deformations): Group 1 (n = 5), impact velocity at 1 m/s; Group 2 (n = 5), impact velocity at 2 m/s; and Group 3 (n = 5), impact velocity at 3 m/s. Functional deficits over time were evaluated up to 28 days after SCI by testing hindlimb reflex and coordinated motor function. The extent of the lesions was analyzed histopathologically and quantified by a morphometric measurement. Mice of all groups exhibited profound functional deficits immediately after injury and subsequent gradual symptomatic recovery. The degrees of recovery were precisely correlated with the magnitudes of impact. The extent of resultant cord lesions was highly reproducible among animals, with little variance: means ± standard deviation, 0.86 ± 0.06/100 mm3 in Group 1; 2.4 ± 0.28/100 mm3 in Group 2; and 11.0 ± 1.0/100 mm3 in Group 3. Our results indicate that this model provides constant functional and histopathological lesions according to impact energy. This new mouse model of SCI opens a new avenue for studies investigating roles and/or effects of specific genes in the recovery process of SCI.