Systems Analysis of the Neuroinflammatory and Hemodynamic Response to Traumatic Brain Injury

Rowan O. Brothers; Sara Bitarafan; Alyssa F. Pybus; Levi  B. Wood; Erin  M. Buckley

doi:10.3791/61504

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Method Article

Systems Analysis of the Neuroinflammatory and Hemodynamic Response to Traumatic Brain Injury

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DOI:

10.3791/61504

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May 27th, 2022

Rowan O. Brothers^*¹ , Sara Bitarafan^*²^,³ , Alyssa F. Pybus¹^,³ , Levi B. Wood^*¹^,²^,³ , Erin M. Buckley^*¹^,⁴^,⁵

¹Wallace H. Coulter Department of Biomedical Engineering, Georgia Institute of Technology and Emory University, ²George W. Woodruff School of Mechanical Engineering, Georgia Institute of Technology, ³Parker H. Petit Institute for Bioengineering and Bioscience, Georgia Institute of Technology, ⁴Department of Pediatrics, Emory University School of Medicine, ⁵Children's Research Scholar, Children's Healthcare of Atlanta

^* These authors contributed equally

Summary

This protocol presents methods to characterize the neuroinflammatory and hemodynamic response to mild traumatic brain injury and to integrate these data as part of a multivariate systems analysis using partial least squares regression.

Abstract

Mild traumatic brain injuries (mTBIs) are a significant public health problem. Repeated exposure to mTBI can lead to cumulative, long-lasting functional deficits. Numerous studies by our group and others have shown that mTBI stimulates cytokine expression and activates microglia, decreases cerebral blood flow and metabolism, and impairs cerebrovascular reactivity. Moreover, several works have reported an association between derangements in these neuroinflammatory and hemodynamic markers and cognitive impairments. Herein we detail methods to characterize the neuroinflammatory and hemodynamic tissue response to mTBI in mice. Specifically, we describe how to perform a weight-drop model of mTBI, how to longitudinally measure cerebral blood flow using a non-invasive optical technique called diffuse correlation spectroscopy, and how to perform a Luminex multiplexed immunoassay on brain tissue samples to quantify cytokines and immunomodulatory phospho-proteins (e.g., within the MAPK and NFκB pathways) that respond to and regulate activity of microglia and other neural immune cells. Finally, we detail how to integrate these data using a multivariate systems analysis approach to understand the relationships between all of these variables. Understanding the relationships between these physiologic and molecular variables will ultimately enable us to identify mechanisms responsible for mTBI.

Introduction

Overview
Mild traumatic brain injuries (mTBIs) impact ~1.6-3.8 million athletes annually¹. These injuries, including sub-concussive and concussive injuries, can leave patients with transient physical, emotional, psychological and cognitive symptoms². Moreover, repetitive mTBI (rmTBI) sustained within a “window of vulnerability” can lead to cumulative severity and duration of cognitive consequences that last longer than the effects of a single mTBI alone³, and ultimately even to permanent loss of function⁴^,