Age-Related Changes in Bone Mineral Density, Cross-Sectional Area and Strength at Different Skeletal Sites in Male Rats.

Abstract

ABSTRACT. Age-related changes in bone mineral density (BMD), cross-sectional area and strength strain index (SSI) of the long bones in the limbs and first lumbar vertebra of male Wistar rats were measured by a peripheral quantitative computed tomography (pQCT) method. One hundred and ten rats aged 2-30 months were used. The results indicate that the total (cortical + trabecular), cortical and trabecular BMD values of the metaphysis and cortical BMD values of the diaphysis in the long bones varied for each bone and differed from those of the first lumbar vertebra. The total BMD of long bones showed high values at 6-21 months and then decreased, but these did not always coincide with cortical and trabecular BMD. The values of SSI in the long bones varied. The values of total and cortical BMD and SSI of lumbar vertebra increased for 6-12 months and then decreased, but the trabecular BMD increased after 12 months. The total area in both the long bones and the first lumbar vertebra increased with the decrease in cortical area and the increase in the trabecular area with increasing age. It was concluded that age-related changes in bones, similar to those observed in humans, could be observed in some bones and parameters, although the age in rats when the so-called peak bone mass appears in the whole skeleton could not be clearly determined. KEY WORDS: age change, bone mineral density, male rat, peak bone mass, peripheral quantitative computed tomography (pQCT) J. Vet. Med. Sci. 64(1): 29-34, 2002 Rats are widely used for studies on bone metabolism and diseases such as osteoporosis, although their worth as an animal model has been contested [6,12,16,21] because their bone morphological patterns differ from those of humans. Rats show a modeling pattern from youth to old age, while humans show a modeling pattern in the growth stage which changes to a remodeling pattern after maturity [7]. The length and weight of long bones in rats continue to increase up to the old age due to the fact that both or either of the epiphysial growth plates do not close for a long time [8]. The cortical and trabecular bone components of the femur neck in rats have been found to be higher and lower, respectively, than those in humans [3].The age of peak bone mass, hereafter referred to as bone mineral density, in a human is considered a significant indicator for knowing the state of activity of bone metabolism and age of onset of osteoporosis, because thereafter the bone mass reduces with increasing age. To clarify whether rats show peak bone mass or not is an important matter for considering their worth as a model animal in bone researches and for determining corresponding ages between rats and humans in experimental procedures and assessing experimental results. That is, we are interested to know if rats have age-related changes in bone metabolism throughout their life similar to those in humans. We demonstrated that high values of mineral and organic contents at various skeletal sites are present in rats [11] and a peak of bone volume i...

Vertebral blood perfusion reduction associated with vertebral bone mineral density reduction: A dynamic contrast‐enhanced MRI study in a rat orchiectomy model

“…Under normal conditions, mature male rats at the age of six to seven months maintain a constant spine BMD (20). In this study, in the absence of a control group, we assumed that vertebral perfusion also remains constant in mature male rats aged of six to seven months.…”

Age-Related Changes in Bone Mineral Density, Cross-Sectional Area and the Strength of Long Bones in the Hind Limbs and First Lumbar Vertebra in Female Wistar Rats

“…The strength-strain index (SSI) was also calculated by means of the software described in detail in a previous study [17]. Total (cortical + trabecular) BMD, cortical BMD, and…”

“…We have previously reported the age-related changes in bone mineral density (BMD), cross-sectional area, and strength strain index (SSI), an indicator of bone fragility, in male rats [17], as rats are widely used for experiments regarding bone disease and for pharmacological tests. Female rats are more frequently used than males, for example, as a model of postmenopausal osteoporosis after ovariectomy treatment.…”

“…The measurement of BMD, cross-sectional area, and SSI in the present study was done by the QCT method because this method has merits with regard to simultaneously measuring BMD and morphologic features by separating trabecular and cortical bones, and because it can be carried out in live rats, the same as in clinical use for humans, as described previously [17].…”

Bone loss dynamics result in trabecular alignment in aging and ovariectomized rats

“…8 This initial phase of rapid bone loss is followed by a gradual decrease of bone mass, which is also observed in normally aging rats. 11,12 Many studies showed regional differences in bone loss, even within bones. 13,14 While almost all trabeculae are lost in the metaphyseal bone of the proximal tibia, hardly any changes have been observed in the epiphysis.…”