Versatile and Simple Approach to Determine Astrocyte Territories in Mouse Neocortex and Hippocampus

Abstract

BackgroundBesides 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.MethodsIndividual 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.ResultsThe 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.ConclusionHere 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.

Inflammatory pathology markers (activated microglia and reactive astrocytes) in early and late onset Alzheimer disease: a post mortem study

“…It is worth highlighting that the CA2/3 region is generally considered more resistant to AD pathology, leading us to speculate that the astrocyte reaction may be linked to other underlying mechanisms, which reinforces the importance of possible variations in pathology patterns that are associated with increasing age. Regarding astrocytes, age‐dependent changes in morphology were also reported in rodents, with apparent significant increase volumes in neocortex (primary and secondary somatosensory cortex) and hippocampus (astrocytes from CA3 stratum molecular region) . These findings were also reported to be region‐specific, with GFAP‐positive astroglial profiles increased in the CA1 region and lower in the entorhinal cortex .…”

Probing nano‐organization of astroglia with multi‐color super‐resolution microscopy

“…A, K), glutamine synthetase (Derouiche and Frotscher, ; Volterra et al, 2014b) (Fig. D) and S100β (Grosche et al, ; Nishiyama et al, ) (Fig. N).…”

Astrocytic Process Plasticity and IKKβ/NF-κB in Central Control of Blood Glucose, Blood Pressure, and Body Weight

“…Because conventional approaches, such as immunostaining of glial fibrillary acid protein (GFAP), hardly reveal high-order details of astrocytic processes, we resorted to Golgi staining which has been used to study the detailed branches of neural cells including astrocytes (Alvarez et al, 2015; Grosche et al, 2013; Hama et al, 2004; Marin-Padilla, 1995; Ogata and Kosaka, 2002; Sullivan et al, 2010). In 2012, Ranjan et al modified Golgi staining protocol so that it preferentially stains glial cells, predominantly astrocytes (Ranjan and Mallick, 2012).…”