Different populations and sources of human mesenchymal stem cells (MSC): A comparison of adult and neonatal tissue-derived MSC

The mesenchymal stroma harbors an important population of cells that possess stem cell-like characteristics
including self renewal and differentiation capacities and can be derived from a variety of different sources. These
multipotent mesenchymal stem cells (MSC) can be found in nearly all tissues and are mostly located in perivascular
niches. MSC have migratory abilities and can secrete protective factors and act as a primary matrix for tissue
regeneration during inflammation, tissue injuries and certain cancers.
These functions underlie the important physiological roles of MSC and underscore a significant potential for the
clinical use of distinct populations from the various tissues. MSC derived from different adult (adipose tissue,
peripheral blood, bone marrow) and neonatal tissues (particular parts of the placenta and umbilical cord) are
therefore compared in this mini-review with respect to their cell biological properties, surface marker expression
and proliferative capacities. In addition, several MSC functions including in vitro and in vivo differentiation capacities
within a variety of lineages and immune-modulatory properties are highlighted. Differences in the extracellular
milieu such as the presence of interacting neighbouring cell populations, exposure to proteases or a hypoxic
microenvironment contribute to functional developments within MSC populations originating from different
tissues, and intracellular conditions such as the expression levels of certain micro RNAs can additionally balance
MSC function and fate.