[Progress and perspectives in bone research].
Structural integrity and strength of bone is maintained by a balance between bone resorption and bone formation. The balance in bone remodeling process is maintained by factors including mechanical stress, calcium-regulating hormones and sex hormones. Changes in physiological regulators of bone remodeling such as reduction in mechanical stress, aging and reduction in sex hormones, or an increase in pathological factors such as glucocorticoid and inflammatory cytokines cause disturbances in bone remodeling process. Disturbances in bone remodeling not only reduce the bone volume but also deteriorate material as well as structural properties of bone, resulting in a reduction in bone strength. Mechanisms of how bone resorption is initiated at the surface of damaged or aged bone, and how bone resorption is coulpled to bone formation are under active investigation. Increasing the understanding of physiological regulation and pathological conditions of bone remodeling should be able to develop new therapeutic approaches to osteoporosis and other metabolic bone diseases.