Mazzaro Antonio, Vita Veronica, Ronfini Marco, Casola Irene, Klein Arianna, Dobrowolny Gabriella, Sorarù Gianni, Musarò Antonio, Mongillo Marco, Zaglia Tania
Department of Cardiac, Thoracic, Vascular Sciences and Public Health, University of Padua, Padua, Italy.
Veneto Institute of Molecular Medicine, Padua, Italy.
Front Physiol. 2023 May 12;14:1165811. doi: 10.3389/fphys.2023.1165811. eCollection 2023.
The anatomical substrate of skeletal muscle autonomic innervation has remained underappreciated since it was described many decades ago. As such, the structural and functional features of muscle sympathetic innervation are largely undetermined in both physiology and pathology, mainly due to methodological limitations in the histopathological analysis of small neuronal fibers in tissue samples. Amyotrophic lateral sclerosis (ALS) is a fatal neuromuscular disease which mainly targets motor neurons, and despite autonomic symptoms occurring in a significant fraction of patients, peripheral sympathetic neurons (SNs) are generally considered unaffected and, as such, poorly studied. In this research, we compared sympathetic innervation of normal and ALS muscles, through structural analysis of the sympathetic network in human and murine tissue samples. We first refined tissue processing to circumvent methodological limitations interfering with the detection of muscle sympathetic innervation. The optimized "Neuro Detection Protocol" (NDP) was validated in human muscle biopsies, demonstrating that SNs innervate, at high density, both blood vessels and skeletal myofibers, independent of the fiber metabolic type. Subsequently, NDP was exploited to analyze sympathetic innervation in muscles of SOD1 mice, a preclinical ALS model. Our data show that ALS murine muscles display SN denervation, which has already initiated at the early disease stage and worsened during aging. SN degeneration was also observed in muscles of MLC/SOD1 mice, with muscle specific expression of the SOD1 mutant gene. Notably, similar alterations in SNs were observed in muscle biopsies from an ALS patient, carrying the SOD1 mutation. We set up a protocol for the analysis of murine and, more importantly, human muscle sympathetic innervation. Our results indicate that SNs are additional cell types compromised in ALS and suggest that dysfunctional SOD1 muscles affect their sympathetic innervation.
骨骼肌自主神经支配的解剖学基础自几十年前被描述以来一直未得到充分重视。因此，肌肉交感神经支配的结构和功能特征在生理学和病理学上在很大程度上仍未确定，这主要是由于组织样本中小神经元纤维的组织病理学分析存在方法学上的局限性。肌萎缩侧索硬化症（ALS）是一种致命的神经肌肉疾病，主要靶向运动神经元，尽管相当一部分患者出现自主神经症状，但外周交感神经元（SNs）通常被认为未受影响，因此研究较少。在本研究中，我们通过对人和小鼠组织样本中的交感神经网络进行结构分析，比较了正常肌肉和ALS肌肉的交感神经支配情况。我们首先改进了组织处理方法，以规避干扰肌肉交感神经支配检测的方法学局限性。优化后的“神经检测方案”（NDP）在人体肌肉活检中得到验证，表明SNs以高密度支配血管和骨骼肌纤维，与纤维代谢类型无关。随后，利用NDP分析了临床前ALS模型SOD1小鼠肌肉中的交感神经支配情况。我们的数据表明，ALS小鼠肌肉表现出SN去神经支配，这种情况在疾病早期就已开始，并在衰老过程中恶化。在MLC/SOD1小鼠的肌肉中也观察到了SN变性，这些小鼠具有SOD1突变基因的肌肉特异性表达。值得注意的是，在一名携带SOD1突变的ALS患者的肌肉活检中也观察到了SNs的类似改变。我们建立了一种分析小鼠以及更重要的是人体肌肉交感神经支配的方案。我们的结果表明，SNs是ALS中另外一种受损的细胞类型，并提示功能失调的SOD1肌肉会影响其交感神经支配。
