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Updated: May 4, 2026
A Preclinical Controlled Cortical Impact Model for Traumatic Hemorrhage Contusion and Neuroinflammation
Published on: June 10, 2020
Progressive neurodegeneration after experimental brain trauma: association with chronic microglial activation
David J Loane1, Alok Kumar, Bogdan A Stoica
1From the Department of Anesthesiology and Center for Shock, Trauma and Anesthesiology Research, National Study Center for Trauma and EMS, University of Maryland School of Medicine, Baltimore, Maryland.
Abstract:
Recent clinical studies indicate that traumatic brain injury (TBI) produces chronic and progressive neurodegenerative changes leading to late neurologic dysfunction, but little is known about the mechanisms underlying such changes. Microglial-mediated neuroinflammationis an important secondary injury mechanism after TBI. In human studies, microglial activation has been found to persist for many years after the initial brain trauma, particularly after moderate to severe TBI. In the present study, adult C57Bl/6 mice were subjected to single moderate-level controlled cortical impact and were followed up by longitudinal T2-weighted magnetic resonance imaging in combination with stereologic histologic assessment of lesion volume expansion, neuronal loss, and microglial activation for up to 1 year after TBI. Persistent microglial activation was observed in the injured cortex through 1 year after injury and was associated with progressive lesion expansion, hippocampal neurodegeneration, and loss of myelin. Notably, highly activated microglia that expressed major histocompatibility complex class II (CR3/43), CD68, and NADPH oxidase (NOX2) were detected at the margins of the expanding lesion at 1 year after injury; biochemical markers of neuroinflammation and oxidative stress were significantly elevated at this time point. These data support emerging clinical TBI findings and provide a mechanistic link between TBI-induced chronic microglial activation and progressive neurodegeneration.
Insights
Traumatic brain injury (TBI) triggers persistent microglial activation, a key driver of chronic neuroinflammation and progressive neurodegeneration for up to a year post-injury. This study links microglial activity to ongoing brain damage after TBI.
Area of Science:
- Neuroscience
- Immunology
- Neuropathology
Background:
- Traumatic brain injury (TBI) can lead to chronic neurodegeneration and late-onset neurological deficits.
- Microglial-mediated neuroinflammation is a significant secondary injury mechanism following TBI.
- Microglial activation persists for years after TBI in human studies, especially after moderate to severe injuries.
Purpose of the Study:
- To investigate the long-term mechanisms of neuroinflammation and neurodegeneration after TBI.
- To establish a mechanistic link between chronic microglial activation and progressive brain damage post-TBI.
Main Methods:
- Adult C57Bl/6 mice underwent controlled cortical impact (moderate TBI).
- Longitudinal T2-weighted MRI and stereologic histology were used to assess lesion volume, neuronal loss, and microglial activation up to 1 year post-injury.
- Immunohistochemistry and biochemical assays measured microglial markers, neuroinflammation, and oxidative stress.
Main Results:
- Persistent microglial activation was observed in the injured cortex up to 1 year after TBI.
- This chronic microglial activation correlated with progressive lesion expansion, hippocampal neurodegeneration, and myelin loss.
- Highly activated microglia expressing MHC class II, CD68, and NOX2 were found at lesion margins 1 year post-injury.
- Biochemical markers of neuroinflammation and oxidative stress remained elevated at the 1-year time point.
Conclusions:
- Chronic microglial activation is a persistent consequence of TBI.
- Sustained microglial activation contributes mechanistically to progressive neurodegeneration and lesion expansion after TBI.
- These findings support clinical observations and elucidate the long-term pathological processes following brain trauma.
