Plasticity of human adipose-derived stem cells - relevance to tissue repair

In contrast to cold blooded vertebrates, the ability to regenerate morphologically and functionally complex structures is limited in adult mammals. Recruitment of progenitor cells is a key step in the regenerative process. The possibility of repairing missing or diseased tissues in humans has been potentiated by the increasing understanding of somatic stem cells, their plasticity and the possibility of modulating it, that could be harnessed either to stimulate endogenous repair or to engineer the required tissue. Here, we focus on human mesenchymal stem cells (MSCs), important players in tissue homeostasis in healthy organisms, with a particular emphasis on those derived from the adipose tissue (ADSCs). While a mark of MSC identity is the ability to differentiate into osteoblasts, chondrocytes and adipocytes, there is evidence that their potential goes beyond these three mesenchymal lineages. We discuss some differentiation and modulatory properties of MSCs and provide an overview of our recent work on ADSCs from paediatric patients (pADSCs) that has shown their ability to give raise to non-mesenchymal cells, consistent with a significant plasticity. Finally, we present novel data indicating that both mesenchymal lineages (adipogenic, chondrogenic and osteogenic) and neural and epithelial lineages can originate from clonal lines that like the parental line express markers of pluripotency as well as the stromal cell marker, GREM1. Together these data support the existence of pADSC multipotent stem cells.