Hematopoietic stem cell proliferative behavior as revealed by bromodeoxyuridine labeling

Hematopoietic stem cells (CFUS) are thought to represent a heterogeneous population with different probabilities of self-renewal and different rates of proliferation. As an approach to further characterization of this population, we determined the disappearance of bromodeoxyuridine (BrdUrd)-induced CFUS sensitization to ultraviolet light in normal mice infused with BrdUrd for three weeks and in hydroxyurea-pretreated mice regenerating their CFUS pool during a one-week BrdUrd infusion. the same exponential disappearance with a T1/2 of six days was found in each case. From this and from the apparent absence of a secondary slope on the sensitization decay curve for the recovered hydroxyurea-treated bone marrow, we conclude that fewer than 10% of CFUS may be mitotically quiescent for prolonged periods and that the age structure of the CFUS population reflects a relatively short proliferative history.