Scientists discover molecular clues behind the acute and chronic stages of traumatic brain injury

Summary: The researchers identified a unique biomarker associated only with the chronic or acute phase of TBI.

source: Arizona State University

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

TBI is a growing public health concern, 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 for children and young adults in industrialized countries, and people with TBI are more likely to develop severe and long-term cognitive and behavioral deficits.

“Unfortunately, the molecular and cellular mechanisms of TBI development are multifaceted and have not yet been fully elucidated,” said Sarah Stabenfeldt, Arizona State University professor and lead and corresponding author of the study, which appears in the journal. science progress.

Thus, this complexity influences 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 conduct biopanning research to reveal several key molecular signatures, called biomarkers, that were identified immediately after injury (acute phase), as well as long-term outcomes (chronic phase) of TBI.

“For TBI, the disease progresses and changes over time, which means that a single protein or receptor may be upregulated at one stage of the injury, but not after two weeks,” Sarah Stabenfeldt said. “This dynamic environment makes developing a successful targeting strategy complex.”

To get around these limitations, Arizona State University scientists, led by Sarah Stabenfeldt, used a mouse model of their study to begin studying the root causes of TBI by identifying biomarkers — unique molecular fingerprints found with a specific injury or disease.

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

“Using a stationary mouse model enabled us to make biomarker discovery as the complexity and progression of traumatic diseases was advancing.”

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

“Top-down” discovery methods focus on evaluating candidate biomarkers based on their known participation in the state of interest, said study first author Brianna, a recent Ph.D. Graduated from the Stabenfeldt laboratory.

“In contrast, the ‘bottom-up’ method analyzes changes in tissue composition and finds a way to relate these changes to the condition. It is an unbiased approach but it can be risky because you can identify non-specific signs of the condition or pathology of interest.”

Next, they used several modern “bioanalytical” tools and techniques to identify and capture the molecules, including a “bait” technique for catching potential target molecules called the phage display system, as well as high speed. DNA sequencing to identify protein targets within the genome, and mass spectrometry to sequence peptide fragments from phase viewing experiments.

Another barrier to discover is the unique physiology of a network-like 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 blood vessels and brain tissue,” explains Stabenfeldt. “In a healthy individual, the BBB tightly regulates the exchange of nutrients and waste products from the blood to the brain and vice versa, essentially dividing the brain/central nervous system.”

However, this barrier also complicates drug delivery into the brain so that most molecules/drugs do not passively cross this barrier; Therefore, the field of drug delivery has sought ways to modulate entry and delivery mechanisms. Similarly, for blood-based biomarkers of TBI or other neurodegenerative diseases, the specificity of the pathology and transport of the molecule (if it originated in the brain) from the brain to the blood is a challenge.”

When TBI occurs, the initial injury can disrupt the BBB, resulting in a cascade of cell death and tissue rupture and debris.

Long-term injury causes inflammation and swelling, and causes the immune response to kick in, but it can also impair brain energy sources, or can throttle the brain’s blood supply, leading to further neuronal death and permanent disability.

The main advantage of the experimental set of tools and techniques for the phage display system is that the molecules and potential biomarkers identified are small enough to slip through the tiny holes within the BBB network—thus, opening the way for therapies based on these molecules.

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

“Our study enhances the sensitivity and specificity of the phage to discover new targeting motifs,” Stabenfeldt said. “A mixture of phage and NGS [next-generation sequencing] It was used previously, thus benefiting from bioinformatics analysis. The unique contribution of our study is to put all of these tools together specifically for an in vivo model of TBI. “

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

They found a set of unique biomarkers associated only with acute or chronic stages of TBI. In the acute phase, gentle brain injury targeted targets recognized primarily associated with metabolic dysfunction and the mitochondria (the center of cell power), while the chronic form of TBI was largely associated with neurodegenerative processes.

“Our method for detecting biomarkers was sensitive enough to detect injury in brains collected at different points in the experiments,” said study first author Briana Martinez, a recent Ph. Graduated from the Stabenfeldt laboratory.

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“It was really exciting to see that proteins involved in neurodegenerative diseases were detected at 7 days post-injury, but not in the pre-injury time period after one day. The fact that we were able to observe these differences really shows how useful this method is in exploring aspects of different from brain injury.

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

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

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

About this research TBI News

author: press office
source: Arizona State University
Contact: Press Office – Arizona State University
picture: Photo credited to Arizona State University

original search: open access.
“Revealing spatiotemporal sensitive TBI targeting strategies via phage display in vivo” by Briana I. Martinez et al. science progress


Summary

Revealing spatiotemporal sensitive traumatic brain injury targeting strategies via in vivo phage display

The heterogeneous pathophysiology of traumatic brain injury (TBI) is a barrier to the advancement of diagnoses and treatments, including targeted drug delivery. We used a unique discovery pipeline to identify novel targeting motifs that recognize specific time stages of TBI pathology.

This pipeline has been combined for in vivo bioassay with phage display of domain antibody (dAb), next-generation sequencing analysis, and peptide synthesis. We defined targeting models based on the integration-specific 3 region structure of dAbs for the acute (1 day post-injury) and subacute (7 days post-injury) time points in a preclinical TBI (controlled cortical effect) model.

The bioactivity and temporal sensitivity of the targeting motifs were validated via immunohistochemistry. Immunoprecipitation–mass spectrometry indicated that the acute TBI target was recognizing targets associated with metabolic and mitochondrial dysfunction, whereas the subacute ischemic injury motif was largely associated with neurodegenerative processes.

This pipeline has successfully discovered temporally identified TBI pairs that will serve as the basis for the next generation of targeted TBI therapies and diagnostics.

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