Fortune Favors the Prepared

The intrinsic regenerative capacities of the adult mammalian heart are believed to be limited and insufficient to compensate for major cell loss upon injury. Transplantation of cells bearing regenerative potential emerged as a possible therapeutic strategy more than a decade ago; however, investigators continue searching for the ideal cell and implantation strategy. Mesenchymal stromal cells (MSC) are among the most widely used cell types for regeneration studies. MSC are multipotent, but rigorous in vivo proof of their stem cell identity is still lacking. Residing in the perivascular space of nearly all tissues, MSC are most commonly retrieved from bone marrow or adipose tissue aspirates. MSC are immune evasive and exhibit immunomodulatory properties, essentially making them suitable for possible allogeneic use. MSC are identified by a defined panel of surface markers in the absence of hematopoietic markers and by their in vitro trilineage differentiation potential into osteogenic, adipogenic, and chondrogenic lineages. Irrespective of these criteria, MSC represent a heterogeneous population, and their properties depend on a variety of factors, which include donor and tissue of origin as well as isolation and culturing techniques. In particular, the choice of culturing media, supplements, and oxygen supply may greatly influence their characteristics, which can be exploited to modify their regenerative potential.