Summary: The researchers identified a unique biomarker associated only with the chronic or acute stage of TBI.
Font: Arizona State University
New research led by scientists at Arizona State University has revealed some of the first detailed molecular clues associated with a leading cause 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 one of the leading causes of death and disability in children and young adults in industrialized countries, and people with TBI are more likely to develop serious long-term cognitive and behavioral deficits.
“Unfortunately, the molecular and cellular mechanisms of TBI injury progression are multifaceted and have not yet been fully elucidated,” said Sarah Stabenfeldt, an ASU professor and leader and corresponding author of the study, which appears in the journal. Progress of science.
“Consequently, this complexity affects the development of diagnostic and treatment options for TBI; the goal of our research was to address these current limitations.”
Their research focus was to perform a “biopanning” search to reveal several key molecular signatures, called biomarkers, identified immediately after the injury event (the acute phase), and also the long-term consequences (the chronic phase) of TBI.
“For TBI, the pathology evolves and changes over time, meaning that a single protein or receptor may be increased at one stage of injury, but not two weeks later,” said Sarah Stabenfeldt. “This dynamic environment makes developing a successful targeting strategy difficult.”
To overcome these limitations, ASU scientists, led by Sarah Stabenfeldt, use a mouse model for their study to begin studying the root causes of TBI by identifying biomarkers — unique molecular fingerprints found with a lesion or specific 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 efficacy of therapeutic interventions,” said Stabenfeldt.
“Using the established mouse model allowed us to run biomarkers to find out where the complexity and evolution of lesion pathology was progressing.”
Scientists can often begin to design therapeutic agents or diagnostic devices based on biomarker discovery. 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, a recent Ph.D. graduate in Stabenfeldt’s lab. .
“By contrast, a bottom-up method looks at changes in tissue composition and finds a way to connect those changes to the condition. It is a more unbiased approach, but it can be risky because it can potentially identify markers that are not specific to the condition or pathology of interest.”
They then used several state-of-the-art ‘biopanning’ tools and techniques to identify and capture molecules, including a “bait” technique to fish out potential target molecules called the phage display system, in addition to high-speed DNA sequencing to identify protein targets. within the genome and mass spectrometers to sequence the peptide fragments for phase visualization experiments.
Another obstacle to discovery is the unique physiology of a mesh-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 vascular and brain tissue,” explains Stabenfeldt. “In a healthy individual, the BBB tightly regulates the exchange of nutrients and waste from the blood to the brain and back, essentially compartmentalizing the brain/central nervous system.”
‘However, this barrier also complicates drug delivery to the brain, so most molecules/drugs do not passively cross this barrier; therefore, the field of drug delivery has sought ways to modulate both drug entry and delivery mechanisms. Similarly, for blood-based biomarkers for TBI or other neurodegenerative diseases, the specificity of the pathology and the transfer of the molecule (if it originates from the brain) from the brain to the blood is challenging.”
When traumatic brain injury occurs, the initial injury can disrupt the BBB, triggering a cascade of cell death, torn and damaged tissue, and debris.
Long-term injury causes inflammation and swelling, and triggers the immune response to kick in, but it can also lead to a deterioration of the brain’s energy sources, or it can obstruct the blood supply to the brain, leading to more death of neuronal cells and permanent disability.
A key advantage of their phage display system experimental toolset and techniques is that the molecules and potential biomarkers identified are small enough to slip through the tiny holes within the BBB lattice, opening up the way to therapy based on these molecules.
So despite all these obstacles, the team found a way.
“Our study takes advantage of the sensitivity and specificity of phages to discover new targeting motifs,” said Stabenfeldt. “The combination of phage and NGS [next-generation sequencing] has been used previously, thus taking advantage of bioinformatic analysis. The unique contribution of our study is to bring all these tools together specifically for an in vivo model of TBI.”
They found a set of unique biomarkers associated only with the acute or chronic phases of TBI. In the acute phase, the TBI targeting motif recognized targets primarily associated with metabolic and mitochondrial (the cell’s engine) dysfunction, whereas the chronic TBI motif was largely associated with neurodegenerative processes.
“Our method for biomarker discovery was sensitive enough to detect lesions in brains that were collected at different points in the experiments,” said study first author Briana Martinez, a recent Ph.D. Graduated from the Stabenfeldt laboratory.
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“It was really interesting to see that proteins involved in neurodegenerative diseases were detected 7 days after injury, but not at the earlier time point of 1 day post-injury. The fact that we were able to look at these differences really shows how useful this method could be for exploring various aspects of brain injury.”
It may also begin to explain why people who have suffered a traumatic brain injury 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 foundation for next-generation targeted TBI therapy and diagnosis.
Next, the group plans to expand its collaborations with ASU’s clinical partners and expand its studies to begin looking for these same molecules in human samples.
About this TBI investigation news
Author: press office
Font: Arizona State University
Contact: Press Office – Arizona State University
Image: Image is credited to Arizona State University.
original research: Open access.
“Discovery of temporospatial sensitive TBI targeting strategies through phage display in vivo” by Briana I. Martínez et al. Progress of science
Summary
Discovery of temporospatial sensitive TBI targeting strategies through phage display in vivo
The heterogeneous pathophysiology of traumatic brain injury (TBI) is a barrier to advancing diagnosis and therapy, including targeted drug delivery. We use 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 identified targeting motifs based on the structure of the complementarity-determining region 3 of dAbs for acute (1 day post-injury) and subacute (7 days post-injury) time points in a preclinical model of TBI ( controlled cortical impact).
The bioreactivity and temporal sensitivity of the targeting motifs were validated by immunohistochemistry. Immunoprecipitation-mass spectrometry indicated that the acute TBI targeting motif recognized targets associated with metabolic and mitochondrial dysfunction, whereas the subacute TBI motif was largely associated with neurodegenerative processes.
This pipeline successfully uncovered temporally specific TBI-targeting motif/epitope pairs that will serve as the basis for next-generation targeted TBI therapy and diagnosis.