Concussion, microvascular injury, and early tauopathy in young athletes after impact head injury and an impact concussion mouse model.

Chad A Tagge
Andrew M Fisher
Olga V Minaeva
Amanda Gaudreau-Balderrama
Juliet A Moncaster
Xiao-Lei Zhang
Mark W Wojnarowicz
Noel Casey
Haiyan Lu
Olga N Kokiko-Cochran
Sudad Saman
Maria Ericsson
Kristen D. Onos, The Jackson Laboratory
Ronel Veksler
Vladimir V Senatorov
Asami Kondo
Xiao Z Zhou
Omid Miry
Linnea R Vose
Katisha R Gopaul
Chirag Upreti
Christopher J Nowinski
Robert C Cantu
Victor E Alvarez
Audrey M Hildebrandt
Erich S Franz
Janusz Konrad
James A Hamilton
Ning Hua
Yorghos Tripodis
Andrew T Anderson
Gareth R Howell, The Jackson Laboratory
Daniela Kaufer
Garth F Hall
Kun P Lu
Richard M Ransohoff
Robin O Cleveland
Neil W Kowall
Thor D Stein
Bruce T Lamb
Bertrand R Huber
William C Moss
Alon Friedman
Patric K Stanton
Ann C McKee
Lee E Goldstein


The mechanisms underpinning concussion, traumatic brain injury, and chronic traumatic encephalopathy, and the relationships between these disorders, are poorly understood. We examined post-mortem brains from teenage athletes in the acute-subacute period after mild closed-head impact injury and found astrocytosis, myelinated axonopathy, microvascular injury, perivascular neuroinflammation, and phosphorylated tau protein pathology. To investigate causal mechanisms, we developed a mouse model of lateral closed-head impact injury that uses momentum transfer to induce traumatic head acceleration. Unanaesthetized mice subjected to unilateral impact exhibited abrupt onset, transient course, and rapid resolution of a concussion-like syndrome characterized by altered arousal, contralateral hemiparesis, truncal ataxia, locomotor and balance impairments, and neurobehavioural deficits. Experimental impact injury was associated with axonopathy, blood-brain barrier disruption, astrocytosis, microgliosis (with activation of triggering receptor expressed on myeloid cells, TREM2), monocyte infiltration, and phosphorylated tauopathy in cerebral cortex ipsilateral and subjacent to impact. Phosphorylated tauopathy was detected in ipsilateral axons by 24 h, bilateral axons and soma by 2 weeks, and distant cortex bilaterally at 5.5 months post-injury. Impact pathologies co-localized with serum albumin extravasation in the brain that was diagnostically detectable in living mice by dynamic contrast-enhanced MRI. These pathologies were also accompanied by early, persistent, and bilateral impairment in axonal conduction velocity in the hippocampus and defective long-term potentiation of synaptic neurotransmission in the medial prefrontal cortex, brain regions distant from acute brain injury. Surprisingly, acute neurobehavioural deficits at the time of injury did not correlate with blood-brain barrier disruption, microgliosis, neuroinflammation, phosphorylated tauopathy, or electrophysiological dysfunction. Furthermore, concussion-like deficits were observed after impact injury, but not after blast exposure under experimental conditions matched for head kinematics. Computational modelling showed that impact injury generated focal point loading on the head and seven-fold greater peak shear stress in the brain compared to blast exposure. Moreover, intracerebral shear stress peaked before onset of gross head motion. By comparison, blast induced distributed force loading on the head and diffuse, lower magnitude shear stress in the brain. We conclude that force loading mechanics at the time of injury shape acute neurobehavioural responses, structural brain damage, and neuropathological sequelae triggered by neurotrauma. These results indicate that closed-head impact injuries, independent of concussive signs, can induce traumatic brain injury as well as early pathologies and functional sequelae associated with chronic traumatic encephalopathy. These results also shed light on the origins of concussion and relationship to traumatic brain injury and its aftermath. Brain 2018 Jan 18 [Epub ahead of print]