Human Anatomy Unit, Department of Public Health, Experimental and Forensic Medicine, University of Pavia, 27100 Pavia, Italy.
Department of Biomedical Sciences, Humanitas University, 20090 Milan, Italy.
Int J Mol Sci. 2021 Feb 16;22(4):1939. doi: 10.3390/ijms22041939.
Muscular regeneration is a complex biological process that occurs during acute injury and chronic degeneration, implicating several cell types. One of the earliest events of muscle regeneration is the inflammatory response, followed by the activation and differentiation of muscle progenitor cells. However, the process of novel neuromuscular junction formation during muscle regeneration is still largely unexplored. Here, we identify by single-cell RNA sequencing and isolate a subset of vessel-associated cells able to improve myogenic differentiation. We termed them 'guide' cells because of their remarkable ability to improve myogenesis without fusing with the newly formed fibers. In vitro, these cells showed a marked mobility and ability to contact the forming myotubes. We found that these cells are characterized by CD44 and CD34 surface markers and the expression of Ng2 and Ncam2. In addition, in a murine model of acute muscle injury and regeneration, injection of guide cells correlated with increased numbers of newly formed neuromuscular junctions. Thus, we propose that guide cells modulate de novo generation of neuromuscular junctions in regenerating myofibers. Further studies are necessary to investigate the origin of those cells and the extent to which they are required for terminal specification of regenerating myofibers.
肌肉再生是一个复杂的生物学过程，发生在急性损伤和慢性退化时，涉及多种细胞类型。肌肉再生的最早事件之一是炎症反应，随后是肌肉祖细胞的激活和分化。然而，肌肉再生过程中新型神经肌肉接头的形成过程在很大程度上仍未被探索。在这里，我们通过单细胞 RNA 测序进行鉴定并分离出一小部分能够改善成肌分化的血管相关细胞。我们称它们为“指导”细胞，因为它们具有显著的改善成肌能力，而不会与新形成的纤维融合。在体外，这些细胞表现出明显的迁移能力，并能够与正在形成的肌管接触。我们发现这些细胞的特征是表面标记物 CD44 和 CD34，以及 Ng2 和 Ncam2 的表达。此外，在急性肌肉损伤和再生的小鼠模型中，注射指导细胞与新形成的神经肌肉接头数量增加相关。因此，我们提出指导细胞调节再生肌纤维中新生神经肌肉接头的生成。需要进一步的研究来探讨这些细胞的来源，以及它们在多大程度上需要用于再生肌纤维的终末特化。
