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

摘要 帕金森病（PD）是老年人中的一种主要神经退行性疾病，影响约1%的老年人。 65岁以上人口。帕金森病的根本原因是多巴胺能神经元的损失， 黑部（nigra pars），中脑基底神经节的一部分，导致典型的运动症状（震颤， 运动迟缓、僵硬、姿势不稳定、步态问题）和许多非运动症状（例如，抑郁症， 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PD进展是否扩展到肢体骨骼肌的独特表型。我们发现了一个 与年龄相比，PD大腿肌肉中I型（缓慢、氧化）肌纤维的病理分组夸大- 匹配的非PD对等体。PD中更严重的I型分组与夸大的运动单位相关 在负重任务期间的激活（即，从坐到站），表明生理困难增加，沿着 恶化的移动性评分，表明I型肌纤维分组可能有助于或沿着 帕金森病的典型运动症状异常的I型分类表明去神经支配的比率增加- 神经再支配周期，失神经肌纤维的特征是发育的再生表达， 因素[例如，新生儿电压门控钠通道1.5（Nav1.5）和神经细胞粘附分子（NCAM）]。 在我们最近的研究中，PD的I型分型伴随着Nav1.5 mRNA表达的升高和差异表达。 参与调节神经肌肉接头（NMJ）的关键组分的mRNA和/或蛋白质表达 稳定在最近的一项全转录组RNA-Seq研究中，我们进一步证明了， I肌纤维分组与涉及神经肌肉通讯、神经元和神经元的基因表达网络有关。 发育以及细胞粘附和存活。我们之前发现高强度抗阻运动 康复训练（RT）成功地逆转了PD的几种病理，包括I型肌纤维分组。 我们怀疑这种变化可能是由调节NMJ稳定性的分子转换器介导的，如microRNA （miRNAs），其最近作为基因表达的跨组织介质出现。为了进一步支持， 在我们最近的工作中，许多与I型肌纤维分组相关的肌肉表达的miRNA靶向基因 与神经元存活、神经突生长和轴突导向相关。这些综合研究结果提高了 中心假设，在PD中观察到的极端运动单位重塑表型，以及其部分逆转， RT，将与差异表达的miRNA网络联系起来，并与 失神经肌纤维我们将以两个目标来检验这一假设。目的1：我们将鉴定血清外泌体分离 PD特有的miRNAs，并使用小RNA-聚合酶链反应测定16周RT对此miRNAs表达谱的影响。 Seq.目的2：我们将量化我们的PD复制失神经肌纤维的大小和分布 队列，使我们能够确定16周RT的影响。 我们将继续致力于为申请人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.