Precision and Accuracy of Peripheral Quantitative Computed Tomography (pQCT) in the Mouse Skeleton Compared With Histology and Microcomputed Tomography (μCT)

Abstract

PQCT was evaluated for accuracy of phenotypic characterization of mouse bone in vivo. Bones (tibia, femur, spine) of 27 animals were measured ex vivo with pQCT, microCT, and histomorphometry and of 23 mice in vivo (pQCT). pQCT yielded satisfactory in vivo precision and accuracy in skeletal characterization. Important aspects of modern skeletal research depend on the phenotypic characterization of genetically manipulated mice, with some approaches requiring in vivo measurement. Peripheral quantitative computed tomography (pQCT) is applicable in vivo and provides opportunities to determine a large variety of bone parameters. Here we test the ex vivo and in vivo reproducibility of pQCT, and its accuracy in comparison with histomorphometry and microcomputed tomography (microCT). We examined the tibia, femur, and lumbar spine of 27 mice ex vivo with high-resolution pQCT, using two mouse models (wild-type and ob/ob) with known differences in bone density. Measurements were repeated three times at different days in nine animals. In a second experiment, 23 animals (10 wild-type and 13 bGH transgenic mice) were repeatedly measured in vivo at 12 and 13 weeks of age, respectively. Among metaphyseal sites, the ex vivo precision was highest at the distal femur (RMS CV < 1% for density and < 2% for area). The correlation between density (pQCT) and bone volume fraction (histomorphometry) was r2 = 0.79 (tibia, femur, and spine), and that with microCT was r2 = 0.94 (femur). At the diaphysis, the precision was highest at the femur (< 2% for total and cortical area), and the correlation with microCT was r2 > 0.77. The in vivo precision for bone density (distal femur) was 2.3-5.1%, and that for absolute and relative cortical area (tibia) was 3.1% and 2.2%. The results show that pQCT can yield satisfactory precision and accuracy in skeletal characterization of mouse bones, if properly applied. The potential advantage of pQCT is that it provides a large set of parameters on bone properties and that it can be used in vivo, extending the available methodological repertoire for genetic studies.