Institute of Medical Sciences, School of Medicine, Medical Sciences and Nutrition, University of Aberdeen, Foresterhill, Aberdeen, AB25 2ZD, UK.
Euan Macdonald Centre for Motor Neurone Disease Research, University of Edinburgh, Chancellor's Building, Edinburgh, EH16 4SB, UK.
Ann Clin Transl Neurol. 2020 Sep;7(9):1580-1593. doi: 10.1002/acn3.51134. Epub 2020 Aug 13.
The purpose of the study was to determine the extent and role of systemic hypoxia in the pathogenesis of spinal muscular atrophy (SMA).
Hypoxia was assayed in vivo in early-symptomatic (postnatal day 5) SMA-model mice by pimonidazole and [ F]-Fluoroazomycin arabinoside injections, which accumulate in hypoxic cells, followed by immunohistochemistry and tracer biodistribution evaluation. Glucose uptake in hypoxic cells was assayed by [ F]-Fluorodeoxyglucose labeling. In vitro knockdown of Survival Motor Neuron (SMN) was performed on motor neurons and lactate metabolism measured biochemically, whereas cell cycle progression and cell death were assayed by flow cytometry.
All assays found significant levels of hypoxia in multiple organ systems in early symptomatic SMA mouse pups, except aerated tissues such as skin and lungs. This was accompanied by significantly increased glucose uptake in many affected organs, consistent with a metabolic hypoxia response. SMN protein levels were shown to vary widely between motor neuron precursors in vitro, and those with lower levels were most susceptible to cell death. In addition, SMA-model motor neurons were particularly sensitive to hypoxia, with reduced ability to transport lactate out of the cell in hypoxic culture, and a failure in normal cell cycle progression.
Not only is there widespread tissue hypoxia and multi-organ cellular hypoxic response in SMA model mice, but SMA-model motor neurons are especially susceptible to that hypoxia. The data support the hypothesis that vascular defects leading to hypoxia are a significant contributor to disease progression in SMA, and offer a route for combinatorial, non-SMN related therapy.
本研究旨在确定系统性缺氧在脊髓性肌萎缩症（SMA）发病机制中的程度和作用。
通过注射 pimonidazole 和 [F]-氟脱氧阿拉伯糖嘧啶核苷，对早期症状（出生后第 5 天）SMA 模型小鼠进行体内缺氧检测，该方法可使缺氧细胞积累，随后进行免疫组织化学和示踪剂生物分布评估。通过 [F]-氟脱氧葡萄糖标记检测缺氧细胞中的葡萄糖摄取。在体外对运动神经元进行生存运动神经元（SMN）的敲低，并通过生化方法测量乳酸代谢，而通过流式细胞术检测细胞周期进程和细胞死亡。
所有检测均发现早期症状 SMA 小鼠幼仔的多个器官系统存在显著水平的缺氧，除了充气组织如皮肤和肺部。这伴随着许多受影响器官中葡萄糖摄取的显著增加，与代谢性缺氧反应一致。体外运动神经元前体细胞中 SMN 蛋白水平差异很大，水平较低的细胞最容易死亡。此外，SMA 模型运动神经元对缺氧特别敏感，在缺氧培养中，它们将乳酸运出细胞的能力降低，并且正常细胞周期进程失败。
不仅在 SMA 模型小鼠中存在广泛的组织缺氧和多器官细胞缺氧反应，而且 SMA 模型运动神经元尤其容易受到缺氧的影响。这些数据支持血管缺陷导致缺氧是 SMA 疾病进展的一个重要因素的假说，并为组合、非 SMN 相关治疗提供了一种途径。
