Ultrastructure of astrocytes using volume electron microscopy: A scoping review

The morphological features of astrocytes are crucial for brain homeostasis, synaptic activity and structural support, yet remain poorly quantified. As a result of the nanometre-sized cross-section of neuropil astrocytic processes, electron microscopy (EM) is the only technique availabe to date capable of revealing their finest morphologies. Volume EM (vEM) techniques, such as serial block-face or focused ion beam scanning EM, enable high-resolution imaging of large fields and allow more extensive 3-D model analyses, revealing new astrocytic morphological features. This scoping review aims to summarize the state of the art of astrocyte ultrastructural analysis. This review included 45 of 439 non-duplicated articles from a Pubmed search, categorizing studies by research focus, animal models, brain region, vEM techniques and segmentation methods. By answering classical questions such as volume, surface area, branching complexity and synaptic ensheathment reported in the literature, this work is a valuable resource for scientists working on structural biology or computational neuroscience.