Mesenchymal stem cells: stealth and suppression.

Human post-natal bone marrow contains mesenchymal stem cells (MSCs), which are capable of giving rise to multiple mesenchymal cell lineages. Large quantities of human MSCs can be readily obtained following a simple bone marrow aspiration procedure and subsequent expansion over a million-fold in culture. This extensive capacity for clinical scale expansion in vitro has facilitated the development of preclinical models as well as clinical studies designed to assess the safety, feasibility, and efficacy of transplanting allogeneic MSCs for a variety of indications. This review focuses on the rationale for performing clinical studies of MSC transplantation and will discuss the potential role that MSCs may have in the field of hematopoietic stem cell transplantation as well as for the repair or regeneration of bone, cartilage, and cardiac tissues.