Astrocytes were historically regarded as a homogeneous cell population, which has been disproved since. Based on both morphological parameters and gene expression profiles, far more astrocytic subtypes can be found than the classic division into fibrillary and protoplasmatic astrocytes. However, fibrillary astrocytes are still far less researched than protoplasmatic astrocytes. Here we investigated if the astrocytes in the corpus callosum (cc) of the mouse, as the largest commissural pathway, show potential differences between the various subregions of the cc (genu, rostral body, anterior midbody, posterior midbody, isthmus and splenium).
The morphological characteristics, such as the properties of the projections, the convex hull, the complexity index and the Sholl analysis of the astrocytes differed only slightly between the different subregions of the cc. Although significant differences in the number of primary processes, the complexity index and the average process length in some subregions existed, there were no significant differences in the other morphological parameters. In comparison with protoplasmic astrocytes from the caudate nucleus, there were significant differences with regard to the analysed characteristics, which confirmed the functionality of the method.
The cell density of astrocytes as well as the area fractions of astrocytes, oligodendrocytes and vessels appeared to correlate with the area occupied by the axons travelling through. In regions with predominantly myelinated fibres with a larger diameter, which presumably require more metabolic support, the proportion of astrocytes was also increased. Accordingly the area occupied by oligodendrocytes and vessels was also increased. This was confirmed above all in the genu and the isthmus. Overall, microglia also seemed to influence the distribution of astrocytes in the various subregions, but not as consistently as axons appeared to do.
In summary, the investigations carried out provided evidence of different subpopulations in the individual subregions of the cc, which need to be investigated further with additional studies.
Schweizer, Pia: Charakterisierung der Astrozyten im Corpus callosum der Maus. : Philipps-Universität Marburg 2025-05-15. DOI: https://doi.org/10.17192/z2025.0199.
