Mesenchymal stem cells: myths and reality

Mesenchymal stem cells (MSCs; also called mesenchymal stromal cells) have received much attention during the last two decades, at first because of their regeneration capacity and poor immunogenicity and, more recently, because of their proved immunomodulatory function. Consequently, the number of studies addressing MSC biology and their capacity to treat a broad range of human diseases at the preclinical and clinical level has grown exponentially, with often confusing and conflicting results. The use of poorly defined cell preparations and experimental models, many of them in vitro, has added to such confusion. In this review, we identify what in our opinion remain the main open questions on MSC biology and we attempt to distinguish the facts from the myths concerning endogenous and therapeutic MSC.