Hotchkiss Brain Institute and the Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta T2N 4N1, Canada.
Hotchkiss Brain Institute and the Department of Clinical Neurosciences, University of Calgary, Calgary, Alberta T2N 4N1, Canada
J Neurosci. 2018 Feb 21;38(8):1973-1988. doi: 10.1523/JNEUROSCI.2341-17.2018. Epub 2018 Jan 23.
Aging impairs regenerative processes including remyelination, the synthesis of a new myelin sheath. Microglia and other infiltrating myeloid cells such as macrophages are essential for remyelination through mechanisms that include the clearance of inhibitory molecules within the lesion. Prior studies have shown that the quantity of myeloid cells and the clearance of inhibitory myelin debris are deficient in aging, contributing to the decline in remyelination efficiency with senescence. It is unknown, however, whether the impaired clearance of debris is simply the result of the reduced number of phagocytes or if the dynamic activity of myeloid cells within the demyelinating plaque also declines with aging and this question is relevant to the proper design of therapeutics to mobilize myeloid cells for repair. Herein, we describe a high-resolution multiphoton live imaging protocol that visualizes individual myelinated/demyelinated axons and lipid-containing myeloid cells to investigate the demyelinated lesion of aging female mice. We found that aging lesions have fewer myeloid cells and that these have reduced phagocytosis of myelin. Although the myeloid cells are actively migratory within the lesion of young mice and have protrusions that seem to survey the environment, this motility and surveillance is significantly reduced in aging mice. Our results emphasize the necessity of not only increasing the number of phagocytes, but also enhancing their activity once they are within demyelinated lesions. The high-resolution live imaging of demyelinated lesions can serve as a platform with which to discover pharmacological agents that rejuvenate intralesional remodeling that promotes the repair of plaques. The repair of myelin after injury depends on myeloid cells that clear debris and release growth factors. As organisms age, remyelination becomes less efficient correspondent with fewer myeloid cells that populate the lesions. It is unknown whether the dynamic activity of cells within lesions is also altered with age. Herein, using high-resolution multiphoton live imaging with several novel features, we report that myeloid cells within demyelinated lesions of aging mice have reduced motility, surveillance, and phagocytic activity, suggesting an intralesional impairment that may contribute to the age-related decline in remyelination efficiency. Medications to stimulate deficient aging myeloid cells should not only increase their representation, but also enter into lesions to stimulate their activity.
衰老会损害包括髓鞘再生在内的再生过程，即合成新的髓鞘。小胶质细胞和其他浸润性髓样细胞（如巨噬细胞）对于通过清除病变内抑制性分子来促进髓鞘再生至关重要。先前的研究表明，衰老过程中髓样细胞数量减少以及抑制性髓鞘碎片清除不足，导致髓鞘再生效率随衰老而下降。然而，不清楚碎片清除受损是否仅仅是由于吞噬细胞数量减少所致，或者脱髓鞘斑块内髓样细胞的动态活性是否也随衰老而下降，这个问题与适当设计动员髓样细胞进行修复的治疗方法有关。在此，我们描述了一种高分辨率多光子活细胞成像方案，该方案可用于可视化单个髓鞘化/脱髓鞘轴突和含脂质的髓样细胞，以研究衰老雌性小鼠的脱髓鞘病变。我们发现，衰老病变中的髓样细胞较少，并且这些细胞对髓鞘的吞噬作用降低。尽管年轻小鼠的病变中的髓样细胞具有活跃的迁移性，并且有突起似乎可以监测环境，但这种迁移性和监测性在衰老小鼠中显著降低。我们的结果强调了不仅要增加吞噬细胞的数量，还要增强其在脱髓鞘病变中的活性。脱髓鞘病变的高分辨率活细胞成像可以作为一个平台，用于发现能够恢复促进斑块修复的病变内重塑的药理学制剂。损伤后的髓鞘修复依赖于清除碎片并释放生长因子的髓样细胞。随着生物体的衰老，髓鞘再生的效率降低，病变中浸润的髓样细胞减少。尚不清楚病变内细胞的动态活性是否也随年龄而改变。在此，我们使用具有几个新特点的高分辨率多光子活细胞成像技术报告称，衰老小鼠脱髓鞘病变中的髓样细胞迁移性、监测性和吞噬活性降低，提示存在一种病变内损伤，可能导致与年龄相关的髓鞘再生效率下降。刺激有缺陷的衰老髓样细胞的药物不仅应增加其代表性，还应进入病变刺激其活性。
