Researchers have discovered the molecular keys behind the acute and chronic phases of traumatic brain injury

Summary: Researchers have identified a unique biomarker associated with the chronic or acute phase of brain injury.

A source: Arizona State University

A new study led by scientists at Arizona State University has revealed the first detailed molecular signatures associated with a condition known as traumatic brain injury (TBI), one of the leading causes of death and disability.

TBI is a public health problem affecting more than 1.7 million Americans with an annual cost of $76.5 billion. It is a leading cause of death and disability in children and youth in industrialized countries, and individuals with TBI are likely to develop severe, long-term cognitive and behavioral deficits.

“Unfortunately, the molecular and cellular mechanisms of TBI injury progression are multifaceted and not yet fully elucidated,” said Sarah Stabenfeldt, ASU professor and lead study author and corresponding author. Science Advances.

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

Their research method was to conduct a “biopanning” search to uncover several key molecular signatures, known as biomarkers, identified immediately after the injury event (acute phase) as well as the long-term effects of TBI (chronic phase).

“The pathology for TBI evolves and changes over time, meaning that a protein or receptor may be elevated during one phase of the 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 beginning to investigate the root causes of TBI by identifying biomarkers—the unique molecular fingerprints found with injury or disease—using a mouse model.

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

“Using an established mouse model allowed us to develop a biomarker to determine where the complexity and evolution of injury pathology develops.”

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

“Top-down discovery methods aim to evaluate candidate biomarkers based on their known involvement in the condition of interest,” said first author Briana Stabenfeldt, a recent Ph.D. in the lab.

The bottom-up approach, on the other hand, “changes the tissue composition and finds a way to associate those changes with the condition. It’s an unbiased approach, but it can be dangerous because you can identify markers that 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 the molecules, including a similar “bait” method to capture potential target molecules called a phage display system, in addition to high speed. DNA sequencing to identify protein targets within the genome and mass spectrometers to sequence peptide fragments from phase display experiments.

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

“The blood-brain barrier (BBB) ​​barrier is the barrier between the blood vessels and the brain tissue,” explains Stabenfeldt. “In a healthy person, the BBB tightly regulates the exchange of nutrients and waste from the blood to the brain and vice versa, which separates the brain/central nervous system.”

‘However, this barrier also makes drug delivery to the brain difficult as most molecules/drugs do not passively cross this barrier; therefore, the drug delivery industry has sought ways to modulate access and delivery mechanisms. Similarly, for blood-based biomarkers of TBI or other neurodegenerative diseases, the pathology is specific and the molecule (if it originates in the brain) is difficult to transfer from the brain to the blood.

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

Long-term injury causes inflammation and swelling, and the immune response springs into action, but can also damage the brain’s energy sources or choke off the brain’s blood supply, leading to neuronal cell death and permanent disability.

A key advantage of the phage display system’s suite of experimental tools and techniques is that identified molecules and potential biomarkers are small enough to slip through the tiny holes in the BBB mesh, thus opening the way to therapeutics. these are molecules.

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

“Our research uses phage sensitivity and specificity to discover new target motifs,” said Stabenfeldt. “Combining phage and NGS [next-generation sequencing] previously used, thereby using bioinformatic analysis. A unique contribution of our study is combining all these tools specifically for an in vivo model of TBI.

Qualitative representation of A2 acute injury-specific TBI biomarker HCDR3 (green) and cell nuclei (blue) in 1-dpi tissue. The region of interest (ROI) is indicated by the white box. Scale bars, 200 μm. Credit: Sarah Stabenfeldt, Arizona State University

They found a unique set of biomarkers associated with the acute or chronic phases of TBI. In the acute phase, the TBI target motif mainly recognizes targets associated with metabolic and mitochondrial (cell power) dysfunction, while the chronic TBI motif is mainly associated with neurodegenerative processes.

“Our biomarker discovery method was sensitive enough to detect brain injuries that were clustered at different points in the experiments,” said the study’s first author, Briana Martinez, a recent Ph.D. Graduated in Stabenfeldt’s laboratory.

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“It was really interesting that proteins involved in neurodegenerative diseases were found 7 days after injury, but not at 1 day post-injury. The fact that we were able to observe these differences really shows how useful this approach is in studying different aspects of brain injury.

It may also begin to explain why people with TBI are more likely to develop neurodegenerative diseases such as Parkinson’s and Alzheimer’s later in life.

This successful discovery pipeline now serves as the foundation for next-generation targeted TBI therapy and diagnostics.

Next, the team plans to continue collaborating with clinical partners at ASU and expand their research to begin looking for these same molecules in human samples.

TBI research news about it

Author: Press service
A source: Arizona State University
The connection: Press Office – Arizona State University
Photo: Image courtesy of Arizona State University

Original research: Open access.
“Discovering temporally spatially sensitive TBI targeting strategies through in vivo phage display” Briana I. Martinez et al. Science Advances


Abstract

Discovering temporally spatially sensitive TBI targeting strategies by in vivo phage display

The heterogeneous pathophysiology of traumatic brain injury (TBI) hampers diagnosis and therapy, including targeted drug delivery. We used a unique discovery pipeline to identify novel targetable motifs that recognize distinct temporal phases of TBI pathology.

This pipeline has been combined with in vivo biopanning and domain antibody (dAb) phage display, next-generation sequencing analysis, and peptide synthesis. We identified target motifs based on complement-determining region 3 structures for acute (1 day post-injury) and subacute (7 days post-injury) post-injury time points in a preclinical TBI model (control cortex exposure).

Bioreactivity and temporal sensitivity of target motifs were tested by immunohistochemistry. Immunoprecipitation-mass spectrometry showed that the acute TBI target motif recognizes targets associated with metabolism and mitochondrial dysfunction, while the subacute TBI motif is mainly associated with neurodegenerative processes.

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

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