A Ferret Model of Blast-Induced Traumatic Brain Injury with Biochemical and Neurobehavioral Outcome Measures

Abstract

Although blast-induced traumatic brain injury (bTBI) is considered as the signature injury of recent combat operations such as Operations Iraqi Freedom and Enduring Freedom, no precise biomechanical and biological mechanisms of injury have been identified. Consequently, to date, there are no FDA-approved countermeasures for the treatment of bTBI. Animal models that are highly translatable to humans are required for studying the injury mechanisms underlying bTBI. As a small animal with a gyrencephalic cerebral cortex, the ferret has been increasingly used for studying the mechanisms of neurological disorders in recent years, especially for mechanically induced brain injuries such as traumatic brain injury. In this study, we used a ferret model to understand both biochemical and neurobehavioral outcome measures following closely coupled blast exposure at ∼19 psi. The neurobehavioral battery was used to assess activity and thigmotaxis (open field test), short-term memory (novel object recognition test), motor and gait (CatWalk XT system), and sleep patterns (actigraphy) up to 1 month post-exposure. For biochemical outcome measures, enzyme-linked immunosorbent assays were performed for the estimation of levels of phosphorylated neurofilament heavy chain (pNFH) protein and corticosterone in the serum at 24 h and 1-month post-blast. Western blotting was performed to measure the differential expressions of known biomarkers of brain injury such as pNFH, neurofilament light chain (NFL) protein present in the neurons undergoing degeneration, phosphorylated Tau protein, and glial fibrillary acidic protein at 24-h and 1-month post-blast. The results revealed that blast exposure caused significant anxiety-like behaviors, short-term memory loss, disrupted front and hind limbs movements, and disturbed sleep pattern in a time-dependent manner. Levels of both pNFH and corticosterone increased in the plasma post-blast. Western blotting revealed that blast exposure increased the levels of the biomarker proteins evaluated in different brain regions. Overall, we observed changes in biochemical and neurobehavioral outcomes after blast exposure that together suggest that ferret is a potentially valuable animal model for understanding the mechanism of bTBI and developing effective countermeasures.