An alternate method for determining the proliferative status of transplantable murine stem cells

A simple method for determining the fraction of transplantable hematopoietic stem cells (CFUS) in the S-phase of cell cycle is described and evaluated. The method involves the administration of hydroxyurea to the lethally-irradiated assay animal concomitantly with the cell transplant. With this method, S-phase estimates are equivalent to those obtained with other, more traditional, methods. In addition, the method may prove advantageous in situations where the cell yield is too low for in vitro incubation with 3H-TdR or when ex vivo cell manipulations must be avoided.