The cell injury device: A high-throughput platform for traumatic brain injury research

Modeling Central Nervous System Injury In Vitro: Current Status and Promising Future Strategies

The central nervous system (CNS) injury, which occurs because of mechanical trauma or ischemia/hypoxia, is one of the main causes of mortality and morbidity in the modern society. Until know, despite the fact that numerous preclinical and clinical studies have been undertaken, no significant neuroprotective strategies have been discovered that could be used in the brain trauma or ischemia treatment. Although there are many potential explanations for the failure of those studies, it is clear that there are questions regarding the use of experimental models, both in vivo and in vitro, when studying CNS injury and searching new therapeutics. Due to some ethical issues with the use of live animals in biomedical research, implementation of experimental strategies that prioritize the use of cells and tissues in the in vitro environment has been encouraged. In this review, we examined some of the most commonly used in vitro models and the most frequently utilized cellular platforms in the research of traumatic brain injury and cerebral ischemia. We also proposed some future strategies that could improve the usefulness of these studies for better bench-to-bedside translational outcomes.

In Vitro Models of Traumatic Brain Injury: A Systematic Review

Traumatic brain injury (TBI) is a major public health challenge that is also the third leading cause of death worldwide. It is also the leading cause of long-term disability in children and young adults worldwide. Despite a large body of research using predominantly in vivo and in vitro rodent models of brain injury, there is no medication that can reduce brain damage or promote brain repair mainly due to our lack of understanding in the mechanisms and pathophysiology of the TBI. The aim of this review is to examine in vitro TBI studies conducted from 2008-2018 to better understand the TBI in vitro model available in the literature. Specifically, our focus was to perform a detailed analysis of the in vitro experimental protocols used and their subsequent biological findings. Our review showed that the uniaxial stretch is the most frequently used way of load application, accounting for more than two-thirds of the studies reviewed. The rate and magnitude of the loading were varied significantly from study to study but can generally be categorized into mild, moderate, and severe injuries. The in vitro studies reviewed here examined key processes in TBI pathophysiology such as membrane disruptions leading to ionic dysregulation, inflammation, and the subsequent damages to the microtubules and axons, as well as cell death. Overall, the studies examined in this review contributed to the betterment of our understanding of TBI as a disease process. Yet, our review also revealed the areas where more work needs to be done such as: 1) diversification of load application methods that will include complex loading that mimics in vivo head impacts; 2) more widespread use of human brain cells, especially patient-matched human cells in the experimental set-up; and 3) need for building a more high-throughput system to be able to discover effective therapeutic targets for TBI.

Hydrogen improves cell viability partly through inhibition of autophagy and activation of PI3K/Akt/GSK3β signal pathway in a microvascular endothelial cell model of traumatic brain injury

Objective：Traumatic brain injury (TBI) is one of the most serious public health problems in the world. Hydrogen (H₂), a flammable, colorless, and odorless gas, has been observed to have preventive and therapeutic effects on brain trauma and other neurological disorders, but its exact mechanism has not been fully clarified.Methods: To further study the mechanism underlying the role of hydrogen gas in alleviating BBB damage after TBI, we performed the scratch injury model on cultured brain microvascular endothelial cells (bEnd.3), which formed the microvascular endothelial barrier - an integral part of the highly specialized BBB.Results: In the case of TBI, hydrogen was able to improve the decline of cell viability induced by TBI. More importantly, inhibition of PI3 K/Akt/GSK3β signal pathway or activation of autophagy reduced the protective effect of hydrogen on cell viability, indicating that such protective effect was regulated by PI3 K/Akt/GSK3β signal pathway and was related to the inhibition of autophagy.Conclusion: So we concluded that hydrogen improved the cell viability in a microvascular endothelial cell model of TBI partly through inhibition of autophagy, and inhibitory effect of hydrogen on autophagy was exerted by activating PI3 K/Akt/GSK3β signal pathway. These findings enriched our knowledge about the mechanism of hydrogen therapy against TBI.

Stretch and/or oxygen glucose deprivation (OGD) in an in vitro traumatic brain injury (TBI) model induces calcium alteration and inflammatory cascade

The blood-brain barrier (BBB), made up of endothelial cells of capillaries in the brain, maintains the microenvironment of the central nervous system. During ischemia and traumatic brain injury (TBI), cellular disruption leading to mechanical insult results to the BBB being compromised. Oxygen glucose deprivation (OGD) is the most commonly used in vitro model for ischemia. On the other hand, stretch injury is currently being used to model TBI in vitro. In this paper, the two methods are used alone or in combination, to assess their effects on cerebrovascular endothelial cells cEND in the presence or absence of astrocytic factors. Applying severe stretch and/or OGD to cEND cells in our experiments resulted to cell swelling and distortion. Damage to the cells induced release of lactate dehydrogenase enzyme (LDH) and nitric oxide (NO) into the cell culture medium. In addition, mRNA expression of inflammatory markers interleukin (I L)-6, IL-1α, chemokine (C-C motif) ligand 2 (CCL2) and tumor necrosis factor (TNF)-α also increased. These events could lead to the opening of calcium ion channels resulting to excitotoxicity. This could be demonstrated by increased calcium level in OGD-subjected cEND cells incubated with astrocyte-conditioned medium. Furthermore, reduction of cell membrane integrity decreased tight junction proteins claudin-5 and occludin expression. In addition, permeability of the endothelial cell monolayer increased. Also, since cell damage requires an increased uptake of glucose, expression of glucose transporter glut1 was found to increase at the mRNA level after OGD. Overall, the effects of OGD on cEND cells appear to be more prominent than that of stretch with regards to TJ proteins, NO, glut1 expression, and calcium level. Astrocytes potentiate these effects on calcium level in cEND cells. Combining both methods to model TBI in vitro shows a promising improvement to currently available models.

The blood-brain barrier as a target in traumatic brain injury treatment

Traumatic brain injury (TBI) is one of the most frequent causes of death in the young population. Several clinical trials have unsuccessfully focused on direct neuroprotective therapies. Recently immunotherapeutic strategies shifted into focus of translational research in acute CNS diseases. Cross-talk between activated microglia and blood-brain barrier (BBB) could initiate opening of the BBB and subsequent recruitment of systemic immune cells and mediators into the brain. Stabilization of the BBB after TBI could be a promising strategy to limit neuronal inflammation, secondary brain damage and acute neurodegeneration. This review provides an overview on the pathophysiology of TBI and brain edema formation including definitions and classification of TBI, current clinical treatment strategies, as well as current understanding on the underlying cellular processes. A summary of in vivo and in vitro models to study different aspects of TBI is presented. Three mechanisms proposed for stabilization of the BBB, myosin light chain kinases, glucocorticoid receptors and peroxisome proliferator-activated receptors are reviewed for their influence on barrier-integrity and outcome after TBI. In conclusion, the BBB is recommended as a promising target for the treatment of traumatic brain injury, and it is suggested that a combination of BBB stabilization and neuroprotectants may improve therapeutic success.