Isolation of a highly clonogenic and multipotential subfraction of adult stem cells from bone marrow stroma.

Attempts have been made to develop cell and gene therapies using the adult stem cells from bone marrow referred to as mesenchymal stem cells or marrow stromal cells (MSCs). However, the results have been variable in part because there are no standardized protocols for preparing and characterizing MSCs. In the experiments presented here, we developed a standardized assay by light scattering to measure the content of rapidly self-renewing cells (RS cells) in preparations of MSCs. The assay quickly identifies preparations of MSCs that replicate rapidly in subsequent culture. In addition, the standardized assay enabled us to isolate RS cells that were up to 90% clonogenic and that generated single cell-derived colonies that differentiated into either mineralizing cells or adipocytes with appropriate additions to the medium.