The Effect of Underwater Blast on Aggregating Brain Cell Cultures

Abstract

Although the deleterious effects of primary blast on gas-filled organs are well accepted, the effect of blast-induced shock waves on the brain is less clear because of factors that complicate the interpretation of clinical and experimental data. Brain cell aggregate cultures are comprised of multiple differentiated brain cell types and were used to examine the effects of underwater blast. Suspensions of these cultures encased in dialysis tubing were exposed to explosive-generated underwater blasts of low (∼300 kPa), medium (∼2,700 kPa), or high (∼14,000 kPa) intensities and harvested at 1-28 days post-exposure. No changes in gross morphology were noted immediately or weeks after blast wave exposure, and no increases in either apoptotic (caspase-3) or necrotic (lactate dehydrogenase) cell death were observed. Changes in neuronal (neurofilament H, acetylcholinesterase, and choline acetyltransferase) and glial (glial fibrillary acidic protein, glutamine synthetase) endpoints did not occur. However, significant time- and pressure-related increases in Akt (protein kinase B) phosphorylation were noted, as well as declines in vascular endothelial growth factor levels, implicating pathways involved in cellular survival mechanisms. The free-floating nature of the aggregates during blast wave exposure, coupled with their highly hydrolyzed dialysis tubing containment, results in minimized boundary effects, thus enabling accurate assessment of brain cell response to a simplified shock-induced stress wave. This work shows that, at its simplest, blast-induced shock waves produce subtle changes in brain tissue. This study has mechanistic implications for the study of primary blast-induced traumatic brain injury and supports the thesis that underwater blast may cause subtle changes in the brains of submerged individuals.

A Novel In Vitro Platform Development in the Lab for Modeling Blast Injury to Microglia

“…The microglia viability after pressure loading within 48 h demonstrated that primary microglia showed very strong tolerance to compression pressure, even at an extremely high-pressure level (13.5 MPa) ( Figure 6 ). It coincides with Sawyers research which performed underwater explosives at 14 MPa ( Sawyer et al, 2017a ; Sawyer et al, 2017b ; Sawyer et al, 2018 ). Moreover, a similar phenomenon could be found in neuronal/glial cultures ( Mukhin et al, 1997 ).…”

“…These results suggested that cytokine production was likely to have a linearly time-dependent relation. Another noticeable result was the inducible trend of cytokine expression, which did not exhibit a clearly linearly stress-dependent relation; this may be explained by previous reports that a nonlinear relationship may exist between the pressure intensity and the degree of the cellular inflammatory responses ( Sawyer et al, 2017a ; Sawyer et al, 2017b ; Sawyer et al, 2018 ). In addition, results of acute response also indicate that microglia will rapidly activate the inflammatory response after being loaded by a compression wave and may remain active, thereby prolonging the entire acute inflammatory stress response process.…”

“…simultaneously makes the data recording and analysis complicated. In addition, an open-field underwater blast or shock tube, which is a common method to keep cells exposed to the shock wave, needs special experimental conditions ( Sawyer et al, 2017a ; Sawyer et al, 2018 ). Therefore, generating acute dynamic loadings with physiologically relevant length-scales and time-scales under normal cell culture conditions is a major limitation in understanding the biomechanical mechanism of how cells respond to stress loading ( Shepard et al, 1991 ; Moeendarbary and Harris, 2014 ).…”

The Imbalance of Astrocytic Mitochondrial Dynamics Following Blast-Induced Traumatic Brain Injury

“…Initially starting as a mechanical injury, it is critical to comprehend the mechanical insult characteristics and forces that affect the brain, specifically how they are transferred to the mitochondria. Astrocytes are mechanically sensitive cells that respond to mechanical overpressure insult [21,[72][73][74][75][76][77]. Results from this study indicated that the HOS induced differential remodeling of the astrocytic mitochondrial network, leading to an increase in fragmentation by presenting a higher number of individual mitochondria and a lower number of mitochondrial networks as early as four hours following insult.…”