Mesenchymal stem cells: from the perivascular environment to clinical applications.

Adult stem cells represent a fundamental biological system that has fascinated scientists over the last decades, and are currently the subject of a large number of studies aimed at better defining the properties of these cells, with a prominent focus on improving their application in regenerative medicine. One of the most used adult stem cells in clinical trials are mesenchymal stem cells (MSCs), which are multipotent cells able to differentiate into mature cells of mesodermal lineages. Following the initial studies on MSCs isolated from bone marrow, similar cells were also isolated from a variety of fetal and adult human tissues. Initially considered as identical and equipotent, MSCs from tissues other than bone marrow actually display differences in terms of their plastic abilities, which can be ascribed to the tissue of origin and/or to the procedures used for their isolation. Moreover, results from additional studies suggest that cultured MSCs represent the in vitro version of a subset of in vivo resident cells localized in the perivascular environment. In this review, we will focus our attention on MSCs from tissues other than bone marrow, their in vivo localization and their current applications in clinics.