Noble Kenyaria V, Liu Ting, Matthews Lois J, Schulte Bradley A, Lang Hainan
Department of Pathology and Laboratory Medicine, Medical University of South Carolina, Charleston, SC, United States.
Department of Otolaryngology-Head and Neck Surgery, Medical University of South Carolina, Charleston, SC, United States.
Front Neurol. 2019 Aug 16;10:895. doi: 10.3389/fneur.2019.00895. eCollection 2019.
Age-related hearing loss is a chronic degenerative disorder affecting one in two individuals above the age of 75. Current population projections predict a steady climb in the number of older individuals making the search for interventions to prevent or reverse this disorder even more critical. There is growing acceptance that aberrant activity of resident or infiltrating immune cells, such as macrophages, is a major factor contributing to the onset and progression of age-related degenerative diseases. However, how macrophage populations and their functionally-driven morphological characteristics change with age in the human cochlea remains largely unknown. In this study, we employed immunohistochemical approaches along with confocal and super-resolution imaging, three-dimensional reconstructions, and quantitative analysis to determine age-related changes in macrophage numbers and morphology as well as interactions with other cell-types and structures of the auditory nerve and lateral wall in the human cochlea. In the cochlea of human ears from young and middle aged adults those macrophages in the auditory nerve assumed a worm-like structure in contrast to those in the spiral ligament or associated with the dense microvascular network in the stria vascularis which exhibited a highly ramified morphology. Macrophages in both the auditory nerve and cochlear lateral wall showed morphological alterations with age. The population of activated macrophages in the auditory nerve increased in cochleas obtained from older donors. Dual-immunohistochemical staining with macrophage, myelin, and neuronal markers revealed increased interactions of macrophages with the glial and neuronal components of the aged auditory nerve. These findings implicate the involvement of abnormal macrophage-glia interactions in age-related physiological and pathological alterations in the human cochlea. There is clearly a need to further investigate the contribution of macrophage-associated inflammatory dysregulation in human presbyacusis.
年龄相关性听力损失是一种慢性退行性疾病,影响着每两名75岁以上的人中的一人。目前的人口预测表明,老年人口数量将稳步攀升,这使得寻找预防或逆转这种疾病的干预措施变得更加关键。越来越多的人认为,常驻或浸润性免疫细胞(如巨噬细胞)的异常活动是导致年龄相关性退行性疾病发生和发展的主要因素。然而,在人类耳蜗中,巨噬细胞群体及其功能驱动的形态特征如何随年龄变化在很大程度上仍不清楚。在本研究中,我们采用免疫组织化学方法,结合共聚焦和超分辨率成像、三维重建以及定量分析,来确定人类耳蜗中巨噬细胞数量和形态的年龄相关性变化,以及它们与听神经和外侧壁其他细胞类型及结构的相互作用。在年轻和中年成年人的人耳耳蜗中,听神经中的巨噬细胞呈蠕虫状结构,而螺旋韧带中的巨噬细胞或与血管纹中密集微血管网络相关的巨噬细胞则呈现高度分支的形态。听神经和耳蜗外侧壁中的巨噬细胞均显示出随年龄的形态改变。在老年供体的耳蜗中,听神经中活化巨噬细胞的数量增加。用巨噬细胞、髓磷脂和神经元标记物进行的双重免疫组织化学染色显示,巨噬细胞与老年听神经的神经胶质和神经元成分之间的相互作用增加。这些发现表明异常的巨噬细胞 - 神经胶质相互作用参与了人类耳蜗中与年龄相关的生理和病理改变。显然有必要进一步研究巨噬细胞相关的炎症失调在人类老年性聋中的作用。