[A review of studies on a subset of rapidly self-renewing marrow stromal cells].

A series of studies have demonstrated that bone marrow mesenchymal stem cells (MSCs) are attractive candidates for cell and gene therapies, because they are readily obtained and multipotentially differentiated. Then homogeneous MSC cultures in vitro with more rapidly self-renewing ability and multipotential differentiation will accelerate and improve their progress in clinical application. Colter et al. found that early colonies contain a third kind of cells very small round cells that rapidly self-renew, besides spindle-shaped cells and large flat cells, called RS cells. RS cells are characterized by their extremely small size, rapid rate of replication, and enhanced potential for multilineage differentiation. Moreover, they can be distinguished from more mature cells in the same cultures by a series of surface epitopes and expressed proteins. Therefore, the results raise the possibility that RS cells may have the greatest potential for long-term engraftment and differentiation in vivo.