Age-Related Changes of Bone Mineral Density and Microarchitecture in Miniature Pigs

Abstract

ABSTRACT. Bone mineral density (BMD), distribution of its density and bone histomorphometric parameters were evaluated in lumbar vertebra of normally growing miniature pigs. The fourth lumbar vertebra (L4) of the Göttingen miniature pig were used in this cross-sectional study in vitro. The BMD of the miniature pig was similar to that of humans in tendency of gender differences and some growth patterns during puberty. In these regards this animal appears useful as a model for human bone study. However, the trabecular and cortical BMDs of lumbar spine were extremely high value (399.43 ± 26.36 mg/cm 3 in female trabeculae; 973.06 ± 69.55 mg/cm 3 in female cortical bone; 419.04 ± 34.84 mg/cm 3 in male trabeculae; 1038.81 ± 125.72 mg/cm 3 in male cortical bone in pigs 30 months or more). Furthermore, histomorphometric analysis yielded values that were remarkably different from those found in humans. From these results, it was revealed that miniature pig had a higher bone mass and denser trabecular network than human, indicating that its bone is probably stronger. Therefore, care should be taken in choosing the miniature pig as a bone study model. KEY WORDS: bone mineral density, histomorphometric analyses, lumbar spine, miniature pig.J. Vet. Med. Sci. 66(6): 599-609, 2004 Metabolic bone diseases such as osteoporosis are becoming more important because of an aging society in human medicine. These diseases increase the risk of fragility fracture as bone mineral levels decrease, and also reduces their quality of life. Previous studies have reported that bone strength and fracture risk are closely related to bone mineral density (BMD) [6,9,27]. In contrast, several studies have suggested that changes in bone architecture increase fracture risk [29,31,33,34,43]. Therefore, it is necessary to study the changes in both BMD and architecture for more sensitive investigation of the bone disease.Quantitative computed tomography (QCT) has been widely investigated and applied in recent years as a means of non-invasive quantification of BMD. It has been reported that QCT might be most sensitive to changes in bone density caused by rapid bone turnover, such as in menopausal immobilization or hyperthyroidism [9]. QCT can selectively measure both trabecular and cortical bone [9,13,22,38], and the BMD is expressed in milligrams per cubic centimeter (volumetric density) [9]. Ebbesen et al. showed highly correlation between BMD by QCT and compressive strength in the lumbar vertebrae [9].Several studies have reported that bone disorders such as osteoporosis lead to trabecular and cortical bone alterations in humans. These alterations are characterized not only by a reduction of bone mass but also by structural changes in microarchitecture which is measured by histomorphometry of bone [29,31,33]. Therefore, it has been considered that histomorphometric analysis have an important role as contributor to bone strength, in addition to BMD.Recently, miniature pig has been noticed as for experimental animal of bone study. The pig is an excel...

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