[Regenerative medicine of bone and cartilage].

Regenerative medicine, which takes advantage of the unique capacity of stem cells, is a novel medical strategy to cure irreversible organ failure. There are three important elements in regenerative medicine: cells, scaffolds and signals. Although substantial progress regarding each element has been made in the past few years, it still falls short of clinical applications. In the geriatric field, osteoporosis, osteoarthritis and periodontitis are the major targets of regenerative medicine. They are usually not life-threatening, but often severely affect QOL of elderly patients. Since elderly people have already reduced number of stem cells in bone and cartilage, we need to know the sufficient conditions for osteogenesis and chondrogenesis by comprehensively screening various conditions. We developed a marker gene system expressing green fluorescence protein (GFP) under the control of osteoblast- and chondrocyte-specific promoters. This system helps us monitor osteoblast and chondrocyte differentiation easily, precisely and non-invasively. Using this system, we are now trying to find the sufficient conditions for osteogenesis and chondrogenesis, and to discover osteogenic and chondrogenic small compounds.