Microcavitation as a Neuronal Damage Mechanism in an In Vitro Model of Blast Traumatic Brain Injury

Abstract

tension)-that this clustering of vesicles is heavily influenced by mechanical tension. Recently, evidence has shown that there is a cortical network of actin, among other things, along the conduit of an axon; its contractility, powered by the acto-myosin machinery, gives rise to the axon's intrinsic tension. Here, we employed transgenic drosophila embryos of stage 16 that have green fluorescence protein tagged to synaptotagmin to track vesicles in neurons. Embryos were dissected such that intact single axons could be visualized in vivo. The axons were then imaged under a time-lapse confocal setup where both spatial and temporal quantification of vesicles could be achieved. We targeted the acto-myosin machinery by performing drug incubations that disrupt the ROCK (and MLCK) pathway, which, after 45 minutes, led to a 35% reduction in fluorescence intensity only at the synaptic region and subsequent washout resulted in a 32% (of the 35%-reduction) recovery after 45 minutes. Another transgenic line with non-muscle myosin II expression reduced was also used for comparison purposes. Furthermore, we aim to establish that vesicle declustering is a direct consequence of the loss of tension, but not the disruption of myosin motors. Towards achieving this goal, we designed a microfluidics platform to perfuse drugs at only the axonal region, but not the synaptic region. We also designed a force sensor to measure the rest tension in an axon before and after pharmaceutical treatment. Preliminary results collectively suggest that axonal tension maintained by the acto-myosin network sustains vesicle clustering. Further experimental evidence is required to understand how such is achieved and the functional role of tension in neurons.

Damage and Failure of Axonal Microtubule under Extreme High Strain Rate: An In-Silico Molecular Dynamics Study

“…Under such scenario, the strain rate exerted by the surrounding fluid will be ~10 6 s −1 at 10 μm range and ~10 8 s −1 at 100 nm range. This estimation agrees with the studies focused on possible cavitation damage 15 . From the above equations, we can have a rough idea of how robust the cavitation can be.…”

“…From the above equations, we can have a rough idea of how robust the cavitation can be. Thus, many researchers are now investigating the full mechanism of it during events like traumatic brain injury (TBI) 15 – 19 . In our previous study 17 , we reported that the cavitation bubble collapse can be strong enough to rupture sub-cellular structure, which has led us here to investigate the vulnerability of microtubule.…”

Modeling tissue-selective cavitation damage

“…Recently, interest has grown in cavitation damage to biological materials including tissue (Mancia et al 2017, Pahk et al 2019) and surgical mesh (Bigelow et al 2019) given its relevance to therapeutic ultrasound and traumatic injuries. Cavitation is a potential source of neuron damage in blast traumatic brain injury (Goeller et al 2012, Estrada et al 2017, Franck 2017), and it has also been proposed as a useful context in which to study tissue damage incurred through high-strain-rate injuries (Estrada et al 2018). Laser surgery (Brujan and Vogel 2006) and therapeutic ultrasound (Brujan 2004) also motivate studies of controlled cavitation damage.…”

Acceleration-induced pressure gradients and cavitation in soft biomaterials

“…Our study on how biological soft materials respond to rapid mechanical inputs is an important step to understanding possible underlying injury mechanism(s) in blunt trauma and cavitation-induced brain injury. As an example, cavitation is being conjectured as a possible mechanism for mild to moderate traumatic brain injury (mTBI) 46 – 48 . However, the current understanding of dynamic cavitation in biological materials, e.g., brain tissues, is still very limited and, as a result, a range of mechanical impact that is relevant to cavitation-induced brain injury is still unknown.…”