Paul Flechsig Institute of Brain Research, Faculty of Medicine, University of Leipzig, Leipzig, Germany.
PLoS One. 2013 Jul 23;8(7):e69143. doi: 10.1371/journal.pone.0069143. Print 2013.
Besides their neuronal support functions, astrocytes are active partners in neuronal information processing. The typical territorial structure of astrocytes (the volume of neuropil occupied by a single astrocyte) is pivotal for many aspects of glia-neuron interactions.
Individual astrocyte territorial volumes are measured by Golgi impregnation, and astrocyte densities are determined by S100β immunolabeling. These data are compared with results from conventionally applied methods such as dye filling and determination of the density of astrocyte networks by biocytin loading. Finally, we implemented our new approach to investigate age-related changes in astrocyte territories in the cortex and hippocampus of 5- and 21-month-old mice.
The data obtained by our simplified approach based on Golgi impregnation were compared to previously published dye filling experiments, and yielded remarkably comparable results regarding astrocyte territorial volumes. Moreover, we found that almost all coupled astrocytes (as indicated by biocytin loading) were immunopositive for S100β. A first application of this new experimental approach gives insight in age-dependent changes in astrocyte territorial volumes. They increased with age, while cell densities remained stable. In 5-month-old mice, the overlap factor was close to 1, revealing little or no interdigitation of astrocyte territories. However, in 21-month-old mice, the overlap factor was more than 2, suggesting that processes of adjacent astrocytes interdigitate.
Here we verified the usability of a simple, versatile method for assessing astrocyte territories and the overlap factor between adjacent territories. Second, we found that there is an age-related increase in territorial volumes of astrocytes that leads to loss of the strict organization in non-overlapping territories. Future studies should elucidate the physiological relevance of this adaptive reaction of astrocytes in the aging brain and the methods presented in this study might be a powerful tool to do so.
除了神经元支持功能外，星形胶质细胞还是神经元信息处理的活跃伙伴。星形胶质细胞的典型领域结构（单个星形胶质细胞占据的神经突体积）对于神经胶质-神经元相互作用的许多方面都至关重要。
通过高尔基浸渍测量单个星形胶质细胞的领域体积，并通过 S100β免疫标记测定星形胶质细胞密度。将这些数据与传统应用方法（如染料填充和通过生物胞素加载确定星形胶质细胞网络密度）的结果进行比较。最后，我们实施了新方法来研究 5 个月和 21 个月大的小鼠大脑皮层和海马区星形胶质细胞领域的年龄相关变化。
我们基于高尔基浸渍的简化方法获得的数据与以前发表的染料填充实验进行了比较，结果表明星形胶质细胞领域体积的结果非常相似。此外，我们发现几乎所有偶联的星形胶质细胞（如生物胞素加载所指示的）都对 S100β呈免疫阳性。这种新实验方法的首次应用提供了关于星形胶质细胞领域体积随年龄变化的见解。它们随着年龄的增长而增加，而细胞密度保持稳定。在 5 个月大的小鼠中，重叠因子接近 1，表明星形胶质细胞领域之间几乎没有或没有相互交织。然而，在 21 个月大的小鼠中，重叠因子大于 2，表明相邻星形胶质细胞的突起相互交织。
在这里，我们验证了一种简单、多功能的评估星形胶质细胞领域和相邻领域之间重叠因子的方法的可用性。其次，我们发现星形胶质细胞的领域体积随着年龄的增长而增加，导致非重叠领域的严格组织丧失。未来的研究应该阐明这种衰老大脑中星形胶质细胞适应性反应的生理相关性，本研究中提出的方法可能是一种强大的研究工具。
