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A Precise, Controllable in vitro Model for Diffuse Axonal Injury Through Uniaxial Stretch Injury.

ABSTRACT: Regarding the determination of the biomechanical parameters in a reliable in vitro cell model for diffuse axonal injury (DAI), our study aimed to demonstrate connections between those parameters and secondary axotomy through examination of morphological alterations under a variety of traumatic conditions. An in vitro cell model for DAI was established in primary cultured mouse neurons by uniaxial mechanical stretching of non-myelinated axons under various traumatic conditions: strain (?) = 5, 10, 20, and 50%; strain time (t) = 500, 100, and 20 ms; strain rate ranging between 0.1 and 25 s-1. Axonal real strains (strainaxon) were measured as 4.53 ± 0.27, 9.02 ± 0.91, 17.75 ± 1.65, and 41.8 ± 4.4%. Axonal real strain rates (SRaxon) ranged between 0.096 ± 0.0054 and 20.9 ± 2.2 s-1. Results showed there was no obvious abnormality of axons with a lower strain condition (strainaxon < 17.75 ± 1.65%) during the acute phase within 30 min after injury. In contrast, acute axonal degeneration (AAD) was observed in the axons following injury with a higher strain condition (SRaxon > 17.75 ± 1.65%). In addition, the incidence and degree of AAD were closely correlated with strain rate. Specifically, AAD occurred to all axons that were examined, when ? = 50% (strainaxon = 41.8 ± 4.4%) for 20 ms, while no spontaneous rupture was observed in those axons. Besides, the concentration of Ca2+ within the axonal process was significantly increased under such traumatic conditions. Moreover, the continuity of axon cytoskeleton was interrupted, eventually resulting in neuronal death during subacute stage following injury. In this study, we found that there is a minimum strain threshold for the occurrence of AAD in non-myelinated axons of primary cultured mouse neurons, which ranges between 9.02 ± 0.91 and 17.75 ± 1.65%. Basically, the severity of axonal secondary axotomy post DAI is strain rate dependent under a higher strain above the threshold. Hence, a reliable and reproducible in vitro cell model for DAI was established, when ? = 50% (strainaxon = 41.8 ± 4.4%) for 20 ms.

SUBMITTER: Li Y

PROVIDER: S-EPMC6811664 | biostudies-literature | 2019

REPOSITORIES: biostudies-literature

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A Precise, Controllable in vitro Model for Diffuse Axonal Injury Through Uniaxial Stretch Injury.

Li Yu Y Li Chaoxi C Gan Chao C Zhao Kai K Chen Jianbin J Song Jinning J Lei Ting T

Frontiers in neuroscience 20191017

Regarding the determination of the biomechanical parameters in a reliable in vitro cell model for diffuse axonal injury (DAI), our study aimed to demonstrate connections between those parameters and secondary axotomy through examination of morphological alterations under a variety of traumatic conditions. An in vitro cell model for DAI was established in primary cultured mouse neurons by uniaxial mechanical stretching of non-myelinated axons under various traumatic conditions: stra ...[more]

PMID: 31680808

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Project description:Neurobasal®/B27 is a gold standard culture media used to study primary neurons in vitro. An alternative media (BrainPhys®/SM1) was recently developed which robustly enhances neuronal activity vs. Neurobasal® or DMEM. To the best of our knowledge BrainPhys® has not been explored in the setting of neuronal injury. Here we characterized the utility of BrainPhys® in a model of in vitro mechanical-stretch injury. METHODS/RESULTS:Primary rat cortical neurons were maintained in classic Neurobasal®, or sequentially maintained in Neurocult® followed by BrainPhys® (hereafter simply referred to as "BrainPhys® maintained neurons"). The levels of axonal markers and proteins involved in neurotransmission were compared on day in vitro 10 (DIV10). BrainPhys® maintained neurons had higher levels of GluN2B, GluR1, Neurofilament light/heavy chain (NF-L & NF-H), and protein phosphatase 2 A (PP2A) vs. neurons in Neurobasal®. Mechanical stretch-injury (50ms/54% biaxial stretch) to BrainPhys® maintained neurons modestly (albeit significantly) increased 24h lactate dehydrogenase (LDH) levels but markedly decreased axonal NF-L levels post-injury vs. uninjured controls or neurons given a milder 38% stretch-injury. Furthermore, two 54% stretch-injuries (in tandem) exacerbated 24h LDH release, increased ?-spectrin breakdown products (SBDPs), and decreased Tau levels. Also, BrainPhys® maintained cultures had decreased markers of cell damage 24h after a single 54% stretch-injury vs. neurons in Neurobasal®. Finally, we tested the hypothesis that lentivirus mediated overexpression of the pro-death protein RBM5 exacerbates neuronal and/or axonal injury in primary CNS cultures. RBM5 overexpression vs. empty-vector controls increased 24h LDH release, and SBDP levels, after a single 54% stretch-injury but did not affect NF-L levels or Tau. CONCLUSION:BrainPhys® is a promising new reagent which facilities the investigation of molecular targets involved in axonal and/or neuronal injury in vitro.

Project description:Diffuse axonal injury is an extremely common type of traumatic brain injury encountered in motor vehicle crashes, sports injuries, and in combat. Although many cases of diffuse axonal injury result in chronic disability, there are no current treatments for this condition. Its basic lesion, traumatic axonal injury, has been aggressively modeled in primate and rodent animal models. The inexorable axonal and perikaryal degeneration and dysmyelination often encountered in traumatic axonal injury calls for regenerative therapies, including therapies based on stem cells and precursors. Here we explore the proof of concept that treatments based on transplants of human oligodendrocyte progenitor cells can replace or remodel myelin and, eventually, contribute to axonal regeneration in traumatic axonal injury.We derived human oligodendrocyte progenitor cells from the human embryonic stem cell line H9, purified and characterized them. We then transplanted these human oligodendrocyte progenitor cells into the deep sensorimotor cortex next to the corpus callosum of nude rats subjected to traumatic axonal injury based on the impact acceleration model of Marmarou. We explored the time course and spatial distribution of differentiation and structural integration of these cells in rat forebrain.At the time of transplantation, over 90 % of human oligodendrocyte progenitor cells expressed A2B5, PDGFR, NG2, O4, Olig2 and Sox10, a profile consistent with their progenitor or early oligodendrocyte status. After transplantation, these cells survived well and migrated massively via the corpus callosum in both injured and uninjured brains. Human oligodendrocyte progenitor cells displayed a striking preference for white matter tracts and were contained almost exclusively in the corpus callosum and external capsule, the striatopallidal striae, and cortical layer 6. Over 3 months, human oligodendrocyte progenitor cells progressively matured into myelin basic protein(+) and adenomatous polyposis coli protein(+) oligodendrocytes. The injured environment in the corpus callosum of impact acceleration subjects tended to favor maturation of human oligodendrocyte progenitor cells. Electron microscopy revealed that mature transplant-derived oligodendrocytes ensheathed host axons with spiral wraps intimately associated with myelin sheaths.Our findings suggest that, instead of differentiating locally, human oligodendrocyte progenitor cells migrate massively along white matter tracts and differentiate extensively into ensheathing oligodendrocytes. These features make them appealing candidates for cellular therapies of diffuse axonal injury aiming at myelin remodeling and axonal protection or regeneration.

Dataset Information

A Precise, Controllable in vitro Model for Diffuse Axonal Injury Through Uniaxial Stretch Injury.

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A Precise, Controllable <i>in vitro</i> Model for Diffuse Axonal Injury Through Uniaxial Stretch Injury.

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