3D MicroCT spatial and temporal characterization of thoracic aorta perivascular adipose tissue and plaque volumes in the ApoE-/- mouse model

Abstract

Perivascular adipose tissue (PVAT) influences vascular function and pathology. We present a protocol using micro-computed tomography (microCT), a novel imaging technique typically used for hard biological tissue, to characterize the temporal and spatial development of aorta PVAT and luminal plaque soft tissue. Apolipoprotein E deficient (ApoE) and C57Bl/6J (control) mice were fed a high fat western diet up to 30 weeks. 3D microCT reconstructions were used to quantify: 1) vascular wall volume, a surrogate measure of remodeling, was greater in ApoE, 2) aorta PVAT volume was reduced in ApoE, 3) plaque volumes increased over time in ApoE, 4) plaque development co-localized with luminal ostia, origins of branching arteries, which traveled through areas of greatest PVAT volume, 5) qualitatively, the same arteries showed evidence of increased tortuosity in ApoE. This study reflects the potential of microCT analyses to assess vascular wall, PVAT and arterial trajectory modifications in relevant animal models. Abbreviations: PVAT: perivascular adipose tissue; ApoE: apolipoprotein E deficient mouse strain; Control: C57Bl/6J mouse strain; PTA: 0.3% phosphotungstic acid; microCT: micro-computed tomography; CV: cardiovascular; CVD: cardiovascular disease; IQR: interquartile range; PPARγ: peroxisome proliferator activated receptor - gamma; VV: vasa vasorum; 3D: three dimensional.

X-ray Micro-Computed Tomography: An Emerging Technology to Analyze Vascular Calcification in Animal Models

“…In contrast, soft tissues such as blood vessels have inherently low X-ray attenuation contrast between the tissue and the supporting material used for sample immobilization. Heavy metal stains such as osmium tetroxide [ 99 ], phosphotungstic acid [ 70 , 100 , 101 , 102 ], and iodine [ 70 , 101 , 102 , 103 ] have been used to overcome this potential limitation. These stains differentially bind to internal regions of a sample, providing increased contrast due to the higher range of X-ray attenuation [ 87 , 101 ].…”

“…During µCT image acquisition, tissue sample movement during sample rotation has the potential to cause the corresponding 2-D projections to be out of the registry, thereby producing poorly reconstructed 3-D volumes. Several protocols for sample immobilization have been developed to overcome this problem for small soft tissues such as blood vessels including: (i) liquid immersion protocols using alcohol [ 89 , 100 , 112 ] or corn oil [ 73 , 94 ]; as well as tissue embedding protocols using (ii) agarose gels [ 90 , 113 , 114 , 115 ], (iii) plastic embedding resins [ 116 ], and (iv) paraffin wax [ 70 , 76 , 88 , 91 , 95 , 96 , 117 ]. The advantages and disadvantages of these different sample immobilization techniques are summarized in Table 3 .…”

“…Sample immobilization in liquids has been utilized for several soft tissues during µCT imaging, including blood vessels [ 73 , 89 , 94 , 100 , 112 ]. Huesa et al [ 73 , 94 ] reported that µCT imaging could be utilized to visualize and quantify arterial medial calcification in formalin-fixed aortae from Ecto-nucleotide pyrophosphatase/phosphodiesterase-1 knock-out (Enpp1 −/− ) mice; a model of generalized arterial calcification of infancy.…”

“…However, the X-ray attenuation of the blood vessel wall and plaque is similar, resulting in a low absorption contrast between the two ( Figure 5 (A)/(ii,iii)) [ 76 , 97 ]. As a result, the plaque and blood vessel wall volumes currently have to be manually segmented in atherosclerotic blood vessels for quantification ( Figure 5 B) [ 97 , 100 ]. Going forward, the ability to interrogate 3-D X-ray data sets of calcified blood vessels into manageable and timely analysis platforms will enable µCT to become a routine partner in the analysis of vascular calcification in animal models of this pathology.…”

Morphometric Characterization of Human Coronary Veins and Subvenous Epicardial Adipose Tissue—Implications for Cardiac Resynchronization Therapy Leads

“…However, even the most modern CT systems are limited in their spatial resolution (16). Therefore, a detailed assessment of small structures such as the SEAT requires an in vitro assessment using, for example, micro computed tomography (mCT) (or X-ray microscopy) or histological approaches (17).…”