Short term mild traumatic brain injury mechanisms characterized in an in vivo Göttingen minipig model

Fievisohn, E. M.; Sajja, V. S.; Vaughn, B. M.; VandeVord, P. J.; Hardy, W. N.

Affiliations

¹Virginia Tech-Wake Forest University, Center for Injury Biomechanics

²Salem VA Medical Center, Research & Development Service

Abstract

Traumatic brain injury (TBI) is a recurring problem with an estimated 1.7 million occurrences annually in the United States, accounting for 30.5% of all injury-related deaths (CDC, 2010). This study seeks to answer many of the unknowns surrounding mild TBI (mTBI) regarding the mechanisms and pathogenesis involved over 24 hours by using magnetic resonance spectroscopy (MRS) and immunohistochemistry (IHC). A repeatable rotational injury device was used to induce mTBI in Göttingen minipigs. The minipigs underwent baseline MR scans (7T Bruker) prior to injury and twenty-four hours post injury, at which point the brains were perfused and harvested for IHC. MRS was used to quantify metabolites in a 216 mm3 voxel placed in the genu of the corpus callosum. Metabolites of interest included glutamate (Glu), N-acetylaspartate (NAA), N-acetylaspartylglutamate (NAAG), glutamine (Gln), and the combination of Glu+Gln. IHC was performed on the genu with four antibodies; light neurofilament (LNF), heavy neurofilament (HNF), glial fibrillary acid protein (GFAP), and cleaved caspase-3. ImageJ was used to calculate integrated density for comparison between groups. Two 24 hour sham control and eight 24 hour rotational injury animals have been tested. Three animals have been dropped from an angle of 15° and 25°, one from 35° and one from 40°. Paired Student’s t-tests yielded significant increases in Glu+Gln, Glu/Gln, Glu/NAAG, NAA/NAAG, and Glu+Gln/NAAG between all baseline and 24 hour post injury concentrations (p<0.05). IHC analysis with two tailed Student’s t-tests identified a significant increase in LNF and HNF (p<0.05) build-up between sham and injury animals (p<0.05). GFAP and cleaved caspase-3 stains were not significant between sham and injury animals. In conclusion, there are significant differences that can be seen using MRS and IHC within 24 hours. Next, the staining results will be correlated with the MRS results. This will facilitate interval MRS scanning during a subsequent longitudinal study of the time course development of mTBI.

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