Impact of mechanical injury on oligodendrocyte myelin homeostasis in adult brain

摘要 由头部撞击引起的加速力是导致整个大脑轴突损伤的原因。 个脑袋当组织被快速拉伸时，白色物质束的长轴突是最脆弱的。 冲击损伤导致髓磷脂的显著损伤。轻度脑外伤后 (TBI)，少突胶质细胞死亡很少观察到。然而，髓鞘异常仍然是 经常观察。超微结构分析表明，完整轴突上的髓鞘丢失（初级 脱髓鞘）以及病变内过量髓鞘形成，两者都强调了 破坏了髓磷脂的体内平衡我们假设对大脑的机械冲击破坏了 成熟少突胶质细胞中的髓鞘稳态。由于髓磷脂稳态是由一系列的 转录因子和基因表达，我们假设TBI启动主动信号事件（S） 在少突胶质细胞中，这种（这些）内在变化破坏了髓鞘稳定性。 为了支持这一假设，我们初步研究的数据显示， 少突胶质细胞激活Erk 1/2途径以诱导髓鞘蛋白损失。其他损伤相关 信号，包括Ca 2+增加，谷氨酸和生长因子刺激，也诱导髓鞘丢失， 依赖Erk 1/2的方式。此外，对啮齿动物脑的轻度TBI诱导Erk 1/2活化， 白色少突胶质细胞。最近的研究表明，在成年人中，Erk 1/2的异常激活 少突胶质细胞破坏髓磷脂稳态。我们将检验TBI诱导的Erk 1/2 少突胶质细胞中的活化导致髓鞘异常（Aim 1）。为了研究，我们将 将联合收割机实验性TBI与Erk 1-/-、Erk 2flox/flox：PLP-CreERT小鼠系结合以确定是否 抑制成熟少突胶质细胞中的Erk 1/2活化可防止TBI诱导的髓鞘丢失或改善 髓鞘稳定性目的2将检验TBI中髓鞘异常是由活动性脑损伤引起的这一假设。 涉及成熟少突胶质细胞转录变化的信号事件。我们将在体内使用 TRAP（翻译核糖体亲和纯化），以分离特异于 成熟的少突胶质细胞。随后的RNA-seq分析将阐明TBI诱导的细胞凋亡。 与髓鞘功能障碍相关的少突胶质细胞转录组谱。

ABSTRACT Acceleration forces induced by impact to the head are the cause of damage to axons throughout the brain. Long axons of white matter tracts are most vulnerable when the tissue is rapidly stretched upon impact. The injury results in significant damage to the myelin. Following mild traumatic brain injury (TBI), oligodendrocyte death is rarely observed. However, myelin abnormalities are nevertheless frequently observed. Ultra-structural analyses have shown myelin loss on intact axons (primary demyelination) as well as excess myelin sheath formation within the lesion, both of which underscore a disruption in myelin homeostasis. We hypothesize that mechanical impact on the brain disrupts myelin homeostasis in the mature oligodendrocyte. As myelin homeostasis is regulated by an array of transcription factors and gene expressions, we hypothesize that TBI initiates active signaling event(s) in oligodendrocytes and that this(these) intrinsic change(s) disrupt(s) myelin stability. In support to this hypothesis, data from our preliminary study show that stretch injury of oligodendrocyte activates the Erk1/2 pathway to induce myelin protein loss. Other injury-associated signals, including Ca2+ increase, glutamate and growth factor stimulation, also induced myelin loss in an Erk1/2-dependent manner. Furthermore, mild TBI on rodent brain induced Erk1/2 activation in white matter oligodendrocytes. Recent studies have shown that aberrant Erk1/2 activation in adult oligodendrocytes disrupts myelin homeostasis. We will test the hypothesis that TBI-induced Erk1/2 activation in oligodendrocytes contributes to myelin abnormalities (Aim 1). For the study, we will combine experimental TBI with the Erk1-/-,Erk2flox/flox:PLP-CreERT mouse line to determine whether inhibiting Erk1/2 activation in mature oligodendrocyte prevents TBI-induced myelin loss or improves myelin stability. Aim 2 will test the hypothesis that myelin abnormalities in TBI results from an active signaling event that involves transcriptional changes in mature oligodendrocytes. We will use in vivo TRAP (translating ribosome affinity purification) to isolate TBI-responsive transcripts specific to mature oligodendrocyte in adult brain. Subsequent RNA-seq analysis will elucidate the TBI-induced oligodendrocyte transcriptome profile associated with myelin dysfunction.