Distribution of corpora amylacea in the human midbrain: using synchrotron radiation phase-contrast microtomography, high-field magnetic resonance imaging, and histology

Abstract

Corpora amylacea (CA) are polyglucosan aggregated granules that accumulate in the human body throughout aging. In the cerebrum, CA have been found in proximity to ventricular walls, pial surfaces, and blood vessels. However, studies showing their three-dimensional spatial distribution are sparse. In this study, volumetric images of four human brain stems were obtained with MRI and phase-contrast X-ray microtomography, followed up by Periodic acid Schiff stain for validation. CA appeared as hyperintense spheroid structures with diameters up to 30 μm. An automatic pipeline was developed to segment the CA, and the spatial distribution of over 200,000 individual corpora amylacea could be investigated. A threefold—or higher—density of CA was detected in the dorsomedial column of the periaqueductal gray (860–4,200 CA count/mm3) than in the superior colliculus (150–340 CA count/mm3). We estimated that about 2% of the CA were located in the immediate vicinity of the vessels or in the peri-vascular space. While CA in the ependymal lining of the cerebral aqueduct was rare, the sub-pial tissue of the anterior and posterior midbrain contained several CA. In the sample with the highest CA density, quantitative maps obtained with MRI revealed high R2* values and a diamagnetic shift in a region which spatially coincided with the CA dense region.

Protocol for 3D virtual histology of unstained human brain tissue using synchrotron radiation phase-contrast microtomography

“…After applying a threshold to the image, the resulting image will be a binary image with many connected components. Morphological features of the connected components such as size and sphericity can be used to increase the accuracy of the segmentation [59].…”

“…In SR PhC-µCT, these granules can be identified as hyperintense structures with a spherical shape (Figure 12, Supplementary Figure S4) [28]. Recently, a 3D distribution of CA within the human brain stem was analysed from four subjects with mean age of 76 years old, reporting an increased density in the dorsomedial column of the periaqueductal gray [59]. At the time being, the specificity of our CA detection method must be further investigated, since we anticipate that other densely packed spherical granules encountered in the brain such as Lewy bodies [74] may look similar to CA in SR PhC-µCT measurements.…”

Protocol for 3D Virtual Histology of Unstained Human Brain Tissue using Synchrotron Radiation Phase-Contrast Microtomography

“…Blood vessels (in red) were segmented using an edge-based approach (Lee et al, 2022). Corpora amylacea (yellow) were segmented using an intensity-based approach (Lee et al, 2023) and a similar approach was used to identify neuromelanin (cyan). Corpora amylacea are clustered in the top left corner.…”

“…After applying a threshold to the image, the resulting image will be a binary image with many connected components. Morphological features of the connected components such as size and sphericity can be used to increase the accuracy of the segmentation (Lee et al, 2023).…”

“…In SR PhC-µCT, these granules can be identified as hyperintense structures with a spherical shape (Fig 12, Fig S4) (Hieber et al, 2016). Recently, a 3D distribution of CA within the human brain stem was analysed from four subjects with mean age of 76 years old, reporting an increased density in the dorsomedial column of the periaqueductal gray (Lee et al, 2023). At the time being, the specificity of our CA detection method must be further investigated, since we anticipate that other densely packed spherical granules encountered in the brain such as Lewy bodies (Koh et al, 2006) may look similar to CA in SR PhC-µCT measurements.…”