A novel model of trauma-induced cerebellar injury and myelin loss in mouse organotypic cerebellar slice cultures using live imaging

A tuned gelatin methacryloyl (GelMA) hydrogel facilitates myelination of dorsal root ganglia neurons in vitro

Investigating axonal myelination by Schwann cells (SCs) is crucial for understanding mechanisms underlying demyelination and remyelination, which may help gain insights into incurable disorders like neurodegenerative diseases. In this study, a gelatin-based hydrogel, gelatin methacryloyl (GelMA), was optimized to achieve the biocompatibility, porosity, mechanical stability, and degradability needed to provide high cell viability for dorsal root ganglia (DRG) neurons and SCs, and to enable their long-term coculture needed for myelination studies. The results of cell viability, neurite elongation, SC function and maturation, SC-axon interaction, and myelination were compared with two other commonly used substrates, namely collagen and Poly-d Lysine (PDL). The tuned GelMA constructs (Young's modulus of 32.6 ± 1.9 kPa and the median value of pore size of 10.3 μm) enhanced single axon generation (unlike collagen) and promoted the interaction of DRG neurons and SCs (unlike PDL). While DRG cells exhibited relatively higher viability on PDL after 48 h, i.e., 83.8%, the cells had similar survival rate on GelMA and collagen substrates, 66.7% and 61.5%, respectively. Further adjusting the hydrogel properties to achieve two distinct ranges of relatively small and large pores supported SCs to extend their processes freely and enabled physical contact with and wrapping around their corresponding axons. Staining the cells with myelin basic protein (MBA) and myelin-associated glycoprotein (MAG) revealed enhanced myelination on GelMA hydrogel compared to PDL and collagen. Moreover, the engineered porosity enhanced DRGs and SCs attachments and flexibility of movement across the substrate. This engineered hydrogel structure can now be further explored to model demyelination in neurodegenerative diseases, as well as to study the effects of various compounds on myelin regeneration.

Effect of Etazolate upon Cuprizone-induced Demyelination In Vivo: Behavioral and Myelin Gene Analysis

Demyelination is a well-known pathological process in CNS disorders such as multiple sclerosis (MS). It provokes progressive axonal degeneration and functional impairments and no efficient therapy is presently available to combat such insults. Recently, we have shown that etazolate, a pyrazolopyridine compound and an α-secretase activator, was able to promote myelin protection and remyelination after cuprizone (CPZ)-induced acute demyelination in C57Bl/6 mice. In continuation of this work, here we have further investigated the effects of etazolate treatment after acute cuprizone-induced demyelination at the molecular level (expression of myelin genes Plp, Mbp and Mag and inflammatory markers Il-1β, Tnf-α) and at the functional level (locomotor and spatial memory skills) in vivo. To this end, we have employed two protocols which consists of administering etazolate (10 mg/kg/d) for a period of 2 weeks either during (Protocol #1) or after (Protocol #2) 5-weeks of CPZ-induced demyelination. At the molecular level, we observed that CPZ intoxication altered inflammatory and myelin gene expression and it was not restored with either of the etazolate treatment protocols. At the functional level, the locomotor activity was impaired after 3-weeks of CPZ intoxication (Protocol #1) and our data indicates a modest but beneficial effect of etazolate treatment. Spatial memory evaluated was not affected either by CPZ intake or etazolate treatment in both protocols. Altogether, this study shows that the beneficial effect of etazolate upon demyelination does not occur at the gene expression level at the time points studied. Furthermore, our results also highlight the difficulty in revealing functional sequelae following CPZ intoxication.

Current advances in in vitro models of central nervous system trauma

CNS trauma is a prominent cause of mortality and morbidity, and although much effort has focused on developing treatments for CNS trauma-related pathologies, little progress has been made. Pre-clinical models of TBI and SCI suffer from significant drawbacks, which result in substantial failures during clinical translation of promising pre-clinical therapies. Here, we review recent advances made in the development of in vitro models of CNS trauma, the promises and drawbacks of current in vitro CNS injury models, and the attributes necessary for future models to accurately mimic the trauma microenvironment and facilitate CNS trauma drug discovery. The goal is to provide insight for the development of future CNS injury models and to aid researchers in selecting effective models for pre-clinical research of trauma therapeutics.

Mechanical Stretch of High Magnitude Provokes Axonal Injury, Elongation of Paranodal Junctions, and Signaling Alterations in Oligodendrocytes

Increasing findings suggest that demyelination may play an important role in the pathophysiology of brain injury, but the exact mechanisms underlying such damage are not well known. Mechanical tensile strain of brain tissue occurs during traumatic brain injury. Several studies have investigated the cellular and molecular events following a static tensile strain of physiological magnitude on individual cells such as oligodendrocytes. However, the pathobiological impact of high-magnitude mechanical strain on oligodendrocytes and myelinated fibers remains under investigated. In this study, we reported that an applied mechanical tensile strain of 30% on mouse organotypic culture of cerebellar slices induced axonal injury and elongation of paranodal junctions, two hallmarks of brain trauma. It was also able to activate MAPK-ERK1/2 signaling, a stretch-induced responsive pathway. The same tensile strain applied to mouse oligodendrocytes in primary culture induced a profound damage to cell morphology, partial cell loss, and a decrease of myelin protein expression. The lower tensile strain of 20% also caused cell loss and the remaining oligodendrocytes appeared retracted with decreased myelin protein expression. Finally, high-magnitude tensile strain applied to 158N oligodendroglial cells altered myelin protein expression, dampened MAPK-ERK1/2 and MAPK-p38 signaling, and enhanced the production of reactive oxygen species. The latter was accompanied by increased protein oxidation and an alteration of anti-oxidant defense that was strain magnitude-dependent. In conclusion, mechanical stretch of high magnitude provokes axonal injury with significant alterations in oligodendrocyte biology that could initiate demyelination.