The influence of recombinant human granulocyte colony-stimulating factor on granulopoiesis in mice recovering from cyclophosphamide treatment.

Abstract

Recombinant human granulocyte colony-stimulating factor (rhG-CSF) was evaluated for its effects on granulopoiesis recovery in mice pretreated with cyclophosphamide. The cytotoxic agent was administered on days 0 and 7. rhG-CSF therapy (injected from days 8 to 28) accelerated the recovery and maintained an increased level of peripheral blood neutrophils. Marrow granuloid precursors depression, due the second dose of cyclophosphamide, was prevented by rhG-CSF, but this hemopoietic growth factor was unable to increase these cells in a similar way to that observed in normal mice. This suggests a decreased granuloid marrow proliferation capacity in cyclophosphamide treated mice. In contrast, in the spleen, rhG-CSF highly increased granuloid precursors. However, the contribution of spleen to granuloid recovery was scarce. Mice receiving rhG-CSF after cyclophosphamide demonstrated a biphasic recovery pattern in bone marrow GM-CFU population. A first rebound of GM-CFUs was followed by a nadir and then a second recovery where GM-CFU progenitor cells were significantly increased was observed. On the other hand, rhG-CSF therapy highly increased the spleen GM-CFU numbers at days 24 to 28. Although rhG-CSF increased splenic granulopoiesis, this result shows that the bulk of granulopoiesis recovery due to rhG-CSF therapy in cyclophosphamide pretreated mice occurred in the marrow.