Journal Article

Repetitive Closed-Skull Traumatic Brain Injury in Mice Causes Persistent Multifocal Axonal Injury and Microglial Reactivity

Dikranian, Krikor, Levy, Marilyn A., Sanchez, Laura, Bennett, Rachel E., Tran, Hien T., Shitaka, Yoshitsugu, Brody, David L.

2011

Overview

Repetitive mild or \"concussive\" traumatic brain injury (TBI) can cause substantial neurologic impairment, but the pathological features of this type of injury are not fully understood. We report an experimental model of TBI in which the closed skulls of anesthetized male C57BL/6J mice are struck with an electromagnetically controlled rubber impactor twice with an interval of 24 hours between impacts. The mice had deficits in Morris water maze performance in the first week after injury that only partially resolved 7 weeks later. By routine histology, there was no apparent bleeding, neuronal cell loss, or tissue disruption, and amyloid precursor protein immunohistochemistry demonstrated very few immunoreactive axonal varicosities. In contrast, silver stainingrevealed extensive abnormalities in the corpus callosum and bilateral external capsule, the ipsilateral cortex and thalamus, and the contralateral hippocampal CA1 stratum radiatum and stratum oriens. Electron microscopy of white matter regions demonstrated axonal cytoskeletal disruption, intra-axonal organelle compaction, and irregularities in axon caliber. Reactive microglia were observed in the same areas as the injured axons by both electron microscopy and Iba1 immunohistochemistry. Quantitative analyses of silver staining and Iba1 immunohistochemistry at multipletime points demonstrated transient cortical and thalamic abnormalities but persistent white matter pathology as late as 7 weeks after injury.Thus, prominent and long-lasting abnormalities in this TBI model were underestimated using conventional approaches. The model may be useful for mechanistic investigations and preclinical assessmentof candidate therapeutics.

• Publisher: American Association of Neuropathologists, Inc,Lippincott Williams & Wilkins,Oxford University Press
• Subject: Amyloid beta-Protein Precursor - metabolism / Animals / Axons - metabolism / Axons - pathology / Axons - ultrastructure / Behavioral Symptoms - etiology / Biological and medical sciences / Brain Injuries - complications / Brain Injuries - etiology / Brain Injuries - pathology / Calcium-Binding Proteins - metabolism / Cerebral Cortex - metabolism / Cerebral Cortex - pathology / Corpus Callosum - pathology / Disease Models, Animal / Electromagnetic Phenomena / Functional Laterality - physiology / Gene Expression Regulation - physiology / Injuries of the nervous system and the skull. Diseases due to physical agents / Male / Maze Learning - physiology / Medical sciences / Mice / Mice, Inbred C57BL / Microfilament Proteins - metabolism / Microglia - metabolism / Microglia - pathology / Microglia - ultrastructure / Microscopy, Electron, Transmission - methods / Nerve Fibers, Myelinated - metabolism / Nerve Fibers, Myelinated - pathology / Nerve Fibers, Myelinated - ultrastructure / Neurology / Silver Staining - methods / Statistics, Nonparametric / Time Factors / Traumas. Diseases due to physical agents