Quantitativein vivomicro-computed tomography for assessment of age-dependent changes in murine whole-body composition.
Micro-computed tomography (micro-CT) is used routinely to quantify skeletal tissue mass in small animal models. Our goal was to evaluate repeatedin vivomicro-CT imaging for monitoring whole-body composition in studies of growth and aging in mice. Male mice from 2 to 52 weeks of age were anesthetized and imaged using an eXplore Locus Ultra and/or eXplore speCZT scanner. Images were reconstructed into 3D volumes, signal-intensity thresholds were used to classify each voxel as adipose, lean or skeletal tissue, and tissue masses were calculated from known density values. Images revealed specific changes in tissue distribution with growth and aging. Quantification showed biphasic increases in total CT-derived body mass, lean and skeletal tissue masses, consisting of rapid increases to 8 weeks of age, followed by slow linear increases to 52 weeks. In contrast, bone mineral density increased rapidly to a stable plateau at ~ 14 weeks of age. On the other hand, adipose tissue mass increased continuously with age. A micro-CT-derived total mass was calculated for each mouse and compared with gravimetrically measured mass, which differed on average by < 3%. Parameters were highly reproducible for mice of the same age, but variability increased slightly with age. There was also good agreement in parameters for the same group of mice scanned on the eXplore Locus Ultra and eXplore speCZT systems. This study provides reference values for normative comparisons; as well, it demonstrates the usefulness ofin vivosingle-energy micro-CT scans to quantify whole-body composition in high-throughput studies of growth and aging in mice.
Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, and Bone and Joint Institute, The University of Western Ontario, London, Ontario N6A 5C1, Canada.
Kim L
KL
Beaucage
Robarts Research Institute, Schulich School of Medicine & Dentistry, and Bone and Joint Institute, The University of Western Ontario, London, Ontario N6A 5C1, Canada.
Steven I
SI
Pollmann
Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, and Bone and Joint Institute, The University of Western Ontario, London, Ontario N6A 5C1, Canada.
Stephen M
SM
Sims
Department of Physiology and Pharmacology, Schulich School of Medicine & Dentistry, and Bone and Joint Institute, The University of Western Ontario, London, Ontario N6A 5C1, Canada.
S Jeffrey
SJ
Dixon
Robarts Research Institute, Schulich School of Medicine & Dentistry, and Bone and Joint Institute, The University of Western Ontario, London, Ontario N6A 5C1, Canada; Department of Medical Biophysics, Schulich School of Medicine & Dentistry, and Bone and Joint Institute, The University of Western Ontario, London, Ontario N6A 5C1, Canada; Department of Surgery, Schulich School of Medicine & Dentistry, and Bone and Joint Institute, The University of Western Ontario, London, Ontario N6A 5C1, Canada.
David W
DW
Holdsworth
Adipose tissue; Bone mineral content; Bone mineral density; Growth; Lean tissue; Skeletal tissue