Fig. 1.

Schematic representation of the lineage potential of multipotent mesenchymal stem cells (MSCs) in the bone marrow. The development of mature cells such as adipocytes and osteoblasts proceeds through intermediate “progenitor” cells, preosteoblasts and preadipocytes. Although not thoroughly characterized, several combinations of surface markers have been utilized to enrich for MSCs, as well as committed but not yet fully differentiated precursor cells. The processes of commitment and differentiation are complex and also not well-characterized, but certain transcription factors such as Runx2 (bone) and PPARγ (fat) have been shown to promote the differentiation of one cell type and suppress the differentiation of the other.