X29 - Acute Neuronal Degeneration following Single and Repetitive Blast Traumatic Brain Injuries

Saturday, October 11, 2025

10:00 AM - 11:00 AM PDT

Location: Exhibit Hall F, G & H

Presenting Author(s)

JJ

James John

Undergraduate Researcher
New Jersey Institute of Technology, New Jersey, United States

Co-Author(s)

Tulika Das, Masters

Doctoral Candidate
New Jersey Institute of Technology
Newark, New Jersey, United States
Juan Pablo Bautista, PhD student

PhD student
New Jersey Institute of technology, United States
YL

Ying Li

Research Faculty
New Jersey Institute of Technology, United States

Primary Investigator(s)

BP

Bryan Pfister

Department Chair
New Jersey Institute of Technology, United States

Introduction: : Based on recent data from the Center for Disease Control, there were approximately 214,000 TBI-related hospitalizations and 69,500 TBI-related deaths in 2020 and 2021 respectively. A large portion of those who suffer from TBI are soldiers with over 430,000 service members being exposed since the year 2000. Severe and moderate TBI that soldiers in the field experience have been studied at length but one area of TBI research that has been not been well understood is low-level repeated injuries which military personnel in training and law enforcement are regularly exposed to. This study aims to examine how single and repeated blast TBI impact acute neuronal degeneration. The degeneration of neurons at the acute timepoint could allow us to gain insight into early biomarkers and transient responses that are missed in injury assessments at chronic timepoints. If acute neuronal degeneration were to be detected, it would challenge some of the existing assumptions about mild TBI and show that despite the mild nature of this injury, it can induce immediate neuronal damage. The implications of this potential finding could result in a major change in the way TBI is classified and treated.

Materials and

Methods: : For the experiment, adult male C57/BL6 mice were exposed to single blast (180kPa) and repeated blast injuries (70x3 kPa), and sacrificed at the acute PID1 (Post-Injury Day 1) timepoint. TUNEL (Terminal deoxynucleotidyl transferase dUTP nick end labeling) were used to detect apoptotic cells by identifying DNA fragmentation. Additionally, free-floating immunohistochemistry was applied using Iba1 to stain for microglia and CD68 to stain for activated microglia which show macrophage-like activity in response to injury. Fiji (ImageJ) image analysis software was used to quantify TUNEL+ cells. It was also used to assess the morphological differences in microglia between injured and sham animals. In order to make volumetric estimations and ensure accuracy and unbiased results, stereology techniques using the MBF Biosciences Stereo Investigator were used to quantify microglial activation by counting colocalized Iba1+CD68+ cells in the dentate gyrus (DG) of the hippocampus. The DG was chosen as the region of interest because it is highly vulnerable to injury and is a major site for neurogenesis. TBI impacts neurogenesis and results in the onset of neurodegenerative conditions where microglia are a major contributing factor. Additionally, animals that experienced the repeated blasts were subjected to an Elevated Plus Maze (EPM) and Open Field Test (OFT) to examine anxiety-like behavior and a Novel Object Recognition (NOR) test to look into memory deficits following injury. Both the biochemical and behavior data will illuminate the early impact of blast injuries on neurons and their short-term functional consequences.

Results, Conclusions, and Discussions:: As shown in figure 1, the injured animals had a lower average total branch length compared to the sham animals which shows a morphological change in the microglia, causing their processes to retract. The stereology counts that were performed to evaluate the colocalization of Iba1 and CD68 on single blast animals indicate a significantly higher total number and percentage of activated microglia in injured animals compared to the sham animals. The significantly higher total number and percentage activation of microglia in injured animals shows that there are more microglia exhibiting macrophage-like activity and moving to injured cells to engulf debris and coordinating immune responses. The behavioral deficits associated with these low level injuries can be seen in figure 2. The EPM and OFT showed that mice that experienced the repeated blast injury exhibited anxiety-like behavior when compared to their sham counterparts. In both tests, the injured mice spent significantly less time in the open area and center zone of the EPM and OFT respectively. The NOR also showed that the injured mice were experiencing memory deficits due to their inability to recognize a familiar object, leading to a significantly lower discrimination index. This behavior data shows the functional consequences associated with these low level injuries. The TUNEL staining in figure 3 showed that there was an increased percentage area of TUNEL+ cells in the injured animals compared to the sham. These findings indicate that mild TBI models cause enough stress to cells to begin traveling down regulated cell death pathways and give rise to apoptotic cell death. The combined findings of increased microglial activation, TUNEL+ percentage area, and behavioral deficits in injured animals indicate that neuronal degeneration is already underway at an acute time point. Currently, more samples are being analyzed for the single blast group and analysis on the repeated blast group is still in progress. This study provides a good foundation to further examine acute neuronal degeneration using neuron specific markers to quantify acute neuronal loss.

Acknowledgements and/or References (Optional): : CDC. (2024, April 29). TBI Data. Traumatic Brain Injury & Concussion. https://www.cdc.gov/traumatic-brain-injury/data-research/index.html

Howard, J. T., et al. (2022). "Association of Traumatic Brain Injury With Mortality Among Military Veterans Serving After September 11, 2001." JAMA Netw Open 5(2): e2148150.