Scientists uncover molecular clues behind acute and chronic phases of traumatic brain injury

Summary: The researchers identified a unique biomarker associated only with the chronic or acute stage of traumatic brain injury.

Source: Arizona State University

New research by scientists at Arizona State University has revealed some of the first detailed molecular clues associated with one of the leading causes of death and disability, a condition known as traumatic brain injury (TBI).

TBI is a growing public health problem, affecting more than 1.7 million Americans at an estimated annual cost of $76.5 billion. It is a leading cause of death and disability in children and young adults in industrialized countries, and people who experience TBI are more likely to develop severe, long-term cognitive and behavioral deficits.

“Unfortunately, the molecular and cellular mechanisms of TBI lesion progression are multifaceted and have not yet been fully elucidated,” said Sarah Stabenfeldt, ASU professor and lead and corresponding author of the study, who appears in the review. Scientists progress.

“Therefore, this complexity affects the development of diagnostic and treatment options for TBI; the aim of our research was to address these current limitations.

Their research approach was to perform “biopanning” research to reveal several key molecular signatures, called biomarkers, identified directly after immediately after the traumatic event (the acute phase), as well as the long-term consequences (the chronic phase). of the BIT.

“For TBI, the pathology evolves and changes over time, which means that a single protein or receptor can be upregulated at one phase of injury, but not two weeks later,” said Sarah Stabenfeldt. “This dynamic environment complicates the development of a successful targeting strategy.”

To overcome these limitations, ASU scientists, led by Sarah Stabenfeldt, are using a mouse model for their study to begin investigating the root causes of TBI by identifying biomarkers – unique molecular fingerprints found with an injury or given disease.

“The neurotrauma research community is a well-established field that has developed and characterized preclinical animal models to better understand TBI pathology and assess the effectiveness of therapeutic interventions,” Stabenfeldt said.

“Using the established mouse model allowed us to biomarker discover where the complexity and progression of injury pathology was progressing.”

Scientists can often begin to design therapeutic agents or diagnostic devices based on the discovery of biomarkers. Stabenfeldt’s team used a “bottom-up” approach to biomarker discovery.

“Top-down” discovery methods focus on evaluating candidate biomarkers based on their known involvement in the condition of interest,” said study first author Briana, who recently completed her Ph.D. graduated from the Stabenfeldt laboratory.

“In contrast, a ‘bottom-up’ method analyzes changes in tissue composition and finds a way to relate those changes to condition. It’s a more unbiased approach but can be risky because you may possibly identify markers that don’t are not specific to the condition or pathology of interest.

Next, they used several state-of-the-art “biopanning” tools and techniques to identify and capture molecules, including a “baiting” technique to fish out potential target molecules called a phage display system, in addition to a high-speed display system. DNA sequencing to identify protein targets in the genome and mass spectrometers to sequence peptide fragments for phase display experiments.

Another obstacle to discovery is the unique physiology of a mesh network designed to protect the brain from injury or harmful chemicals, called the blood-brain barrier (BBB).

“The blood-brain barrier (BBB) ​​is a barrier between vascular and brain tissue,” says Stabenfeldt. “In a healthy individual, the BBB tightly regulates the exchange of nutrients and waste from the blood to the brain and vice versa, essentially compartmentalizing the brain/central nervous system.”

“However, this barrier also complicates drug delivery to the brain, so most molecules/drugs do not pass through this barrier passively; therefore, the field of drug delivery has sought ways to modulate both entry and delivery mechanisms. Similarly, for blood-based biomarkers for TBI or other neurodegenerative diseases, specificity to pathology and transfer of the molecule (if from the brain) from brain to blood is a challenge.

When a TBI occurs, the initial injury can disrupt the BBB, triggering a cascade of cell death, torn and disrupted tissue, and debris.

The long-term injury causes inflammation and swelling, and causes the immune response to kick in, but can also lead to impaired brain energy sources, or can stifle the blood supply to the brain, resulting in greater neuronal cell death and permanent disability.

A key advantage of their suite of experimental phage display system tools and techniques is that the molecules and potential biomarkers identified are small enough to slip through the tiny holes in the BBB mesh – paving the way to therapies based on these molecules.

So, despite all these obstacles, the team found a way.

“Our study exploits the sensitivity and specificity of phages to uncover novel targeting motifs,” Stabenfeldt said. “The combination of phage and NGS [next-generation sequencing] was used previously, thereby taking advantage of bioinformatics analysis. The unique contribution of our study is to bring together all these tools specifically for an in vivo model of TBI.

This shows damaged brain tissue
Qualitative representation of the A2 acute injury-specific TBI biomarker HCDR3 (green) and cell nuclei (blue) in tissue at 1 dpi. Region of Interest (ROI) shown in the white box. Scale bars, 200 μm. Credit: Sarah Stabenfeldt, Arizona State University

They found a suite of unique biomarkers associated only with the acute or chronic phases of TBI. In the acute phase, the TBI targeting motif recognized targets associated with primarily metabolic and mitochondrial (the powerhouse of the cell) dysfunction, while the chronic TBI motif was largely associated with neurodegenerative processes.

“Our biomarker discovery method was sensitive enough to detect brain lesions that were collected at different times in the experiments,” said study first author Briana Martinez, who recently completed her Ph.D. graduated from the Stabenfeldt laboratory.

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This shows the eye of an older man

“It was really interesting to see that the proteins implicated in neurodegenerative diseases were detected 7 days post-injury, but not at the earliest, 1 day post-injury. The fact that we were able to observe these differences really shows how this method could be useful for exploring various aspects of brain damage.

It may also begin to explain why people who have had TBI are more likely to develop neurodegenerative diseases like Parkinson’s and Alzheimer’s later in life.

This successful discovery pipeline will now serve as the foundation for next-generation targeted TBI therapies and diagnostics.

Next, the group plans to continue its collaborations with ASU’s clinical partners and expand their studies to begin looking for these same molecules in human samples.

About This TBI Research News

Author: Press office
Source: Arizona State University
Contact: Press Office – Arizona State University
Image: Image is credited to Arizona State University

Original research: Free access.
“Discovery of Temporo-Spatial Sensitive TBI Targeting Strategies via Phage Display in Vivo” by Briana I. Martinez et al. Scientists progress


Uncover Temporo-Spatial Sensitive TBI Targeting Strategies Via Phage Display in Vivo

The heterogeneous pathophysiology of traumatic brain injury (TBI) is an obstacle to the advancement of diagnostics and therapeutics, including targeted drug delivery. We used a unique discovery pipeline to identify novel targeting motifs that recognize specific temporal phases of TBI pathology.

This pipeline combined in vivo biopanning with domain antibody (dAb) phage display, next-generation sequencing analysis, and peptide synthesis. We have identified structure-based targeting motifs of region 3 determining dAb complementarity for acute (1 day post-injury) and subacute (7 days post-injury) post-injury time points in a preclinical model of TBI (controlled cortical impact).

Bioreactivity and temporal sensitivity of targeting motifs were validated by immunohistochemistry. Immunoprecipitation-mass spectrometry indicated that the acute TBI targeting pattern recognized targets associated with metabolic and mitochondrial dysfunction, while the subacute TBI pattern was broadly associated with neurodegenerative processes.

This pipeline successfully uncovered temporally-specific TBI targeting motif/epitope pairs that will serve as the basis for next-generation TBI-targeted therapies and diagnostics.

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