Mechanisms of Human Skeletal Muscle Motor Unit Remodeling in Parkinson's Disease

摘要 帕金森病(Parkinson‘s Disease，PD)是一种主要的老年神经退行性疾病，影响到约1%的老年人 65岁以上的人口。帕金森病的根本原因是脑实质中多巴胺能神经元的丢失。 黑质致密部，中脑基底节的一部分，导致典型的运动症状(震颤， 运动迟缓、僵硬、姿势不稳、步态问题)和一系列非运动症状(例如，抑郁， 焦虑、睡眠障碍、嗅觉丧失和认知能力下降)。在我们实验室最近的工作之前， 尚不清楚帕金森病进展是否延伸到肢体骨骼肌中的一种独特表型。我们发现了一个 与年龄相比，帕金森病患者大腿肌肉中I型(缓慢的，氧化的)肌纤维的病理分组被夸大。 匹配的非PD对等体。帕金森病患者I型分型越严重，运动单位越夸张 在负重任务(即坐立)中的激活，表明生理难度增加，并伴有 活动能力评分恶化，提示I型肌纤维分组可能有助于或与之一起进展 帕金森病的典型运动症状。异常的I型分组表明失神经的比率升高- 再神经循环，失神经肌纤维的特征是发育的重现表达 因素[例如，新生儿电压门控钠通道1.5(NaV1.5)和神经细胞黏附分子(NCAM)]。 在我们最近的工作中，帕金森病的I型分组伴随着NaV1.5 mRNA的高表达和分化 神经肌肉接头(NMJ)调控关键成分的mRNA和/或蛋白表达 稳定性。在最近的转录组范围的RNA-Seq研究中，我们进一步证明了类型的程度 I肌纤维分组与参与神经肌肉通讯、神经 发育、细胞黏附和存活。我们此前发现，高强度的抗阻运动 康复训练(RT)成功地逆转了帕金森病的几种病理改变，包括I型肌纤维分组。 我们怀疑这种变化可能是由调节NMJ稳定性的分子转导分子所介导的，例如microRNAs (MiRNAs)，它们最近作为基因表达的跨组织中介而出现。在进一步的支持中，a 我们最近工作的靶基因中与I型肌纤维分组相关的肌肉表达的miRNAs的数量 与神经元存活、轴突生长和轴突引导有关。这些综合发现提高了 中枢假说认为帕金森病患者的极端运动单位重塑表型及其部分逆转 RT，将与差异表达的miRNA网络联系在一起，结合发病率的变化 失去神经的肌纤维。我们将通过两个目标来检验这一假设。目的1：我们将鉴定分离的血清外切体 Pd特有的miRNAs，并使用小RNA确定16wk RT对该miRNA表达谱的影响 序列号。目标2：我们将量化我们的PD复制的失神经肌肉纤维的数量和分布 队列，使我们能够确定16周RT的影响。这项研究有望显著推动 同时为申请者提供创新和富有成效的培训和职业发展。

ABSTRACT Parkinson’s disease (PD) is a leading neurodegenerative disease among aging adults, affecting ~1% of the population over age 65. The well-established root cause of PD is loss of dopaminergic neurons in the substantia nigra pars compacta, part of the basal ganglia in the midbrain, leading to the classic motor symptoms (tremor, bradykinesia, rigidity, postural instability, gait problems) and a host of non-motor symptoms (e.g., depression, anxiety, sleep disorders, loss of smell, and cognitive decline). Prior to our laboratory’s recent work, it was unknown whether PD progression extended to a unique phenotype in limb skeletal muscles. We found an exaggerated pathological grouping of type I (slow, oxidative) myofibers in PD thigh muscle compared to age- matched non-PD peers. More severe type I grouping in PD was associated with exaggerated motor unit activation during weight-bearing tasks (i.e., sit-to-stand), indicating increased physiologic difficulty, along with a worsened mobility scores, suggesting that type I myofiber grouping may contribute to or progress along with the classic motor symptoms of PD. Abnormal type I grouping is indicative of heightened rates of denervation- reinnervation cycling, with denervated myofibers characterized by recapitulated expression of developmental factors [e.g., neonatal voltage-gated sodium channel 1.5 (Nav1.5) and neural cell adhesion molecule (NCAM)]. In our recent work, type I grouping in PD was accompanied by elevated Nav1.5 mRNA expression and differential mRNA and/or protein expression of key components involved in regulating neuromuscular junction (NMJ) stability. In a recent transcriptome-wide RNA-Seq investigation, we further demonstrated that the degree of type I myofiber grouping was linked to gene expression networks involved in neuromuscular communication, neural development, and cell adhesion and survival. We previously found that high-intensity resistance exercise rehabilitation training (RT) successfully reversed several pathologies of PD, including type I myofiber grouping. We suspect this change is likely mediated by molecular transducers regulating NMJ stability, such as microRNAs (miRNAs), which have recently emerged as cross-tissue mediators of gene expression. In further support, a number of muscle-expressed miRNAs associated with type I myofiber grouping in our recent work target genes associated with neuronal survival, neurite outgrowth, and axon guidance. These combined findings raise the central hypothesis that the extreme motor unit remodeling phenotype seen in PD, and its partial reversal with RT, will be linked to differentially expressed miRNA networks in conjunction with alterations in the prevalence of denervated myofibers. We will test this hypothesis with two aims. Aim 1: We will identify serum exosome-isolated miRNAs unique to PD and determine the impact of 16 wk RT on this miRNA expression profile using small RNA- Seq. Aim 2: We will quantify the magnitude and distribution of denervated myofibers from our PD replicate cohort, enabling us to determine the impact of 16 wk RT. This research is expected to markedly advance the field, while providing innovative and fruitful training and career development for the applicant.