Quantitative and Qualitative Analyses of Low-mineral-diet Ovariectomised Rat Femora Using Microscopic Computed Tomography

Abstract

The aim of this study was to monitor changes in bone density and bone quality (microarchitecture) in the femoral epiphyseal region in rats with bone loss induced by oestrogen deficiency and accelerated by mineral deficiency. Forty-eight Wistar rats were divided into 3 groups (n = 16 per group): Group 1, sham-operated rats on a normal diet; Group 2, ovariectomised rats on a normal diet; and Group 3, ovariectomised rats on a mineraldeficient diet. Observations were conducted 4, 8, 16, and 24 weeks after the operation (sham or ovariectomy), while the rats were on their respective diets. Microscopic computed tomography of the femoral epiphyseal region was used to generate 3-dimensional bone density distribution maps, and to compute bone density values. Densities of cortical and cancellous bone in Groups 2 and 3 were significantly less than densities in Group 1, and densities in Group 3 were significantly less than densities in Group 2 at nearly every post-operative time interval.This study demonstrated that: a) ovariectomy in rats induces bone loss; b) a mineral-deficient diet accelerates bone loss that has been induced by oestrogen deficiency; and c) 3-dimensional bone density distribution maps may be useful in diagnosing osteoporosis and other diseases causing bone loss. Microscopic computed tomography is a powerful analytical tool for measuring spatial variations in bone density, and temporal changes in the patterns of 3-dimensional bone density distribution maps.

Bone Quality of the Femoral Mid-Shaft of Ovariectomized Rats Fed a Low-Mineral Diet

“…Since our present study indicates that osteoclast activity became more dominant than that of osteoblasts, the microstructures on the interior of the cortical bone must have been resorbed. Similar resorption was observed for cancellous bone trabeculae 12) . In the femur, which is a long bone, bone turnover is fast because of fast blood flow in the marrow cavity 25) , suggesting that trabecular resorption was enhanced.…”

“…10). Moreover, since the blood mineral level was reduced in Group 3 because of reduced estrogen secretion and ingestion of a low-mineral diet, homeostasis might have been maintained by trabecular bone resorption 12) resulting in the lower bone density compared with that for Group 2 ( It has been reported that both bone formation and resorption are transiently promoted, and bone metabolic turnover was enhanced after OVX, and bone metabolism more rapidly responded in cancellous bone present in the marrow cavity than in cortical bone in long bones because of fast blood flow 25) .…”

“…The analytical system employing micro-CT and TRI/3D used in this study is capable of 3D visualization of the trabecular structure, qualitative analysis by pseudocolor rendering, and quantitative analysis of bone volume, density, and trabeculae 12) . In conventional micro-CT imaging, black and white images are evaluated because the color intensity representing Xray penetration and non-penetration through materials is judged.…”

“…Micro-CT is particularly useful for determining bone density and microstructural analysis of bone tissue and is widely applied in other fields 12,22,23) . The analytical system employing micro-CT and TRI/3D used in this study is capable of 3D visualization of the trabecular structure, qualitative analysis by pseudocolor rendering, and quantitative analysis of bone volume, density, and trabeculae 12) .…”

“…OVX rats develop bone mutations associated with reduced secretion of estrogen 9) and exhibit subsequent changes in bone metabolism and systemic conditions 10,11) and bone loss 7,9,12) . A low-mineral diet accelerates bone loss in OVX rats [13][14][15] .…”