Mesenchymal stem cells (MSCs), with high self-renewal capacity and muti-potentiality, are mainly differentiated into osteoblasts and adipocytes in adult bone marrow. With aging, MSCs senescence results in the differentiation shift: osteoblasts decline and adipocytes increase, which may account for the osteoporosis. The transplantation of healthy bone MSCs, which can rebuild osteogenesis ability, will provide a new idea for the prevention and treatment of osteoporosis.