Bone Aging and Senile Osteoporosis: Morphological Analyses
Abstract: The human skeleton is a metabolically active organ that undergo continuous bone remodeling throughout life. The old bone is constantly being removed by osteoclasts and new bone is formed by osteoblasts. The activities of osteoclasts and osteoblasts are regulated under a strict balance to ensure normal bone mass. An imbalance in the bone resorption and bone formation results in metabolic skeletal diseases, such as osteoporosis. Osteoporosis is the most common metabolic skeletal disease, with very high fracture risk, especially among the elderly. This review article presents the age-related bone morphological changes in humans and the senile osteoporosis in experimental animals. We describe the trabecular and cortical bone microstructural parameters of the human vertebra, femur and tibia with age. We also discuss morphological and molecular biological alterations in senile osteoporosis model, the senescence-accelerated mouse prone P6 (SAMP6). Osteocyte is an important orchestrator of the bone remodeling. The peroxisome proliferator-activated receptor γ and secreted frizzled-related protein 4 (SFRP4) might be related to the lower bone mass in SAMP6.
Key words: osteoporosis, SAMP6, bone remodeling, micro CT, osteocyte