[On "2015 Guidelines for Prevention and Treatment of Osteoporosis". Cellular mechanism and etiology of osteoporosis].

The bone is continuously renewed throughout adult life by the coordinated action of osteoclastic bone resorption and osteoblastic bone formation in response to various hormones, cytokines, chemokines and biomechanical external stimuli. This process, called bone remodeling, is a prerequisite for the normal bone homeostasis that maintains both bone quality and strength. An imbalance of bone resorption and bone formation is often central to metabolic bone diseases. Aging, various diseases including life-style-related diseases, and loss of mechanical stress lead to an excessive bone resorption, resulting in osteoporosis due to decreased bone mineral density and deterioration of bone quality. Therefore, the activity of both osteoclasts and osteoblasts must be tightly regulated during bone remodeling. Understanding the regulatory mechanisms of bone cells and signal transduction through bone cell communication is important for treating osteoporosis.