Hierarchical bioimaging and quantification of vasculature in disease models using corrosion casts and microcomputed tomography

Abstract

A wide range of disorders are associated with alterations of the central and peripheral vascular system. Modified vascular corrosion casting using a newly developed polymer, allows for the first time hierarchical assessment of 3D vessel data in animals down to the level of capillaries. Imaging of large volumes of vasculature at intermediate resolution (16 µm) was performed using a desktop micro-computed tomography system. Subsequently regions of interest were identified for additional high resolution imaging (1.4 µm) at the X-ray Tomographic Microscopy (XTM) station of the Swiss Light Source (SLS). A framework for systematic hierarchical imaging and quantification was developed. Issues addressed included enhanced XTM data acquisition, introduction of local tomography, sample navigation, advanced post processing, and data combination. In addition to visual assessment of qualitative changes, morphometrical and architectural indices were determined using direct 3D morphometry software developed in house. Vessel specific parameters included thickness, surface, connectivity, and vessel length. Reconstructions of cerebral vasculature in mutant mice modeling Alzheimer's disease revealed significant changes in vessel architecture and morphology. In the future, a combination of these techniques may support drug discovery. Additionally, future ultra-high-resolution in vivo systems may even allow non-invasive tracking of temporal alterations in vascular morphology.

Cerebrovascular phenotypes in mouse models of Alzheimer’s disease

“…Using vascular corrosion casts and scanning electron microscopy (SEM), 44 the 3D cerebrovascular architecture of 7-27 mo old APP23 and WT mice were characterized. [45][46][47][48][49] In WT mice vascular casts displayed a dense capillary network where arteries and veins were distinguishable by imprints of either elongated or rounded endothelial cells (ECs), respectively. 46 In contrast, APP23 mice displayed a multitude of vascular malformations including swelling, looping, twisting, and kinking, similar to vascular alterations present in the human AD brains.…”

“…47,[50][51][52] Functionally, flow patterns in WT mice were normal as measured by magnetic resonance angiography (MRA), but in APP23 mice 60 Minogue et al 63 Wang et al 62 Kelly et al 57 70 Giannoni et al 68 (continued) flow disturbances were observed in carotid arteries at 11 mo of age with significant flow voids in the major arteries of the Circle of Willis by 20 mo of age. 45,47,48 Moreover, vascular casts showed areas devoid of vessels that were sites of thioflavin S-positive Ab plaques.…”

“…The size of the voids increased with age and were attributed to smaller voids progressing into a single larger cavity and thought to be sites of angiogenic processes 48,49,53 (Figure 2). Additionally, the cavities appeared to preferentially cluster in the frontal and temporal cortices, 46 mirroring a similar phenotype observed in human AD 50,51 where early depositions of Ab were first detected in the frontal and temporal regions.…”

Deep convolutional neural networks for segmenting 3D in vivo multiphoton images of vasculature in Alzheimer disease mouse models

“…Other studies that compared AD models and WT also found negligible or no difference in capillary diameters. Heinzer et al compared a different mouse model (APP23) using MRA and found no difference between WT and AD mice [57]. The same group also compared the effects of "VEGF overexpression" model and WT using SRµCT and also found little difference [58].…”

Computer-based analysis of microvascular alterations in a mouse model for Alzheimer's disease

“…VCCs were macerated, decalcified and stained with osmium tetroxide for better absorption contrast in the X-ray. 3D images of the full mouse brain vasculature were acquired with a desktop µCT system (µCT40, Scanco Medical, Bassersdorf, Switzerland), complemented by local SRµCT scanning (Materials Science Beamline, Swiss Light Source, PSI, Villigen, Switzerland) [8,10,11] for local regions of interest (ROI), using a nominal voxel size of 16 µm and 1.4 µm, respectively [8]. Tomographic image data was reconstructed using a filtered backprojection algorithm.…”