Corpora amylacea in the brain form highly branched three-dimensional lattices.

Corpora amylacea (CA) are glycoprotein-based depositions that accumulate in the normal aging brain or consecutively to different neuro-degenerative diseases. Although controversies still exists in what it regards their origins and functions, their morphology is described simply as round basophilic entities based on bi-dimensional observations. The aim of the present study was to evaluate the three-dimensional morphology of these bodies in the brain in normal aging. We utilized here brain tissue from six aged patients, and performed an in-depth stereological analysis of CAs based on series of thin serial sections, and 50 μm-thick sections. The thin seriate sections have been counter-stained with Hematoxylin and Eosin, while the thick sections have been immunostained in fluorescence for ubiquitin and GFAP/collagen IV or aquaporin 4. Three-dimensional renderings have been obtained after aligning the serial sections, while high-resolution z-stacks have resulted after deconvolution on the thick sections. More than 70% of all the identified CAs proved to be in fact parts of larger aggregates, where the flattened individual spheroids branched and communicated with other bodies in a complex pattern, and budding of small CAs from larger CAs could be observed. There was a direct correlation between the diameter of the vessels and the number of associated CAs. Astrocyte GFAP and aquaporin 4 signals surrounded CAs, but without any colocalization with the ubiquitin areas, while perivascular CAs were sometimes enclosed in pockets of the basement membranes. In conclusion, as far as we know, this is the first study to describe the three-dimensional branching complexity of corpora amylacea in the brain.