Growing evidence supports the idea that skeletal stem cells play important roles in bone development. Over the recent years, the identification of skeletal stem cells has evolved from cells simply defined byin vitrobehaviors to cells identified by a combination ofex vivoserial transplantation assays andin vitrolineage-tracing experiments. These approaches have shown better identification of the characteristics of skeletal stem cells residing in multiple tissues, including the perichondrium of the fetal bone, the resting zone of the postnatal growth plate and the adult bone marrow space. Multiple groups of skeletal stem cells seem to collaborate tightly and achieve critical biological functions of mineralized tissue, including not only bone development and growth, but also maintenance and repair. Although recently more studies have been focusing on this topic and collecting numbers of important findings, we are still beginning to understand the diversity and the nature of skeletal stem cells, and how they actually behavein vivo. Accumulating works need to be done to investigate the feature and systemic regulation of skeletal stem cells.
