The elusive nature and function of mesenchymal stem cells

Mesenchymal stem cells (MSCs) are a diverse subset of multipotent precursors present in the stromal fraction of many adult tissues and have drawn intense interest from translational and basic investigators. MSCs have been operationally defined by their ability to differentiate into osteoblasts, adipocytes and chondrocytes after in vitro expansion. Nevertheless, their identity in vivo, heterogeneity, anatomical localization and functional roles in adult tissue homeostasis have remained enigmatic and are only just starting to be uncovered.