A new approach to evaluate the total reserve of hematopoietic progenitors after acute irradiation.

Based on the capacity of certain hematopoietic growth factors to mobilize the hematopoietic progenitors from bone marrow to peripheral blood, we have investigated whether the number of progenitors that can be mobilized to peripheral blood after irradiation correlates with the radiation dose and reflects the total reserve of bone marrow progenitors that survive the exposure. In three different mouse strains, a close relationship was observed between the number of G-CSF mobilized progenitors and the radiation dose received by the animals. When G-CSF was replaced by one single injection of SD01 plus thrombopoietin, a similar relationship between the two parameters was observed, which fitted to the multitarget theoretical model. This treatment also promoted 50% survival in mice receiving a lethal dose of 9 Gy. The estimation of the total number of CFU-GM progenitors in the irradiated mice also allowed us to establish a good relationship between the number of progenitors that were mobilized to peripheral blood with respect to the global reserve of surviving progenitors. These results suggest that the quantification of mobilized hematopoietic progenitors would predict the severity and reversibility of the hematopoietic syndrome of irradiated victims, based on direct estimations of their global reserve of hematopoietic progenitors and stem cells.