Failure of stem cell factor to ameliorate AZT-induced anemia in immunodeficient mice

Recent attempts to reduce 3' azido-3' deoxythymidine (AZT)-induced anemia in AIDS patients have focused both on AZT dose reduction and on the use of recombinant cytokines. The newly cloned cytokine stem cell factor (SCF) is a potent regulator of hematopoietic progenitor cell proliferation. Therefore, we attempted to ameliorate AZT-induced anemia using stem cell factor (SCF) in the LP-BM5 murine leukemia virus-induced model of AIDS (MAIDS). SCF was administered with oral AZT for up to 1 month, and effects on erythropoiesis examined. SCF alone increased both splenic BFU-E and CFU-E. AZT alone also increased the number of splenic BFU-E and CFU-E. SCF, administered to AZT-treated MAIDS mice, did not further enhance these increases. SCF increased bone marrow cellularity in AZT-treated MAIDS mice. However, the total number of bone marrow BFU-E was unaffected. In contrast, AZT, SCF, and the combination significantly decreased bone marrow CFU-E. SCF alone increased the absolute numbers of peripheral blood reticulocytes in MAIDS mice, but did not increase reticulocyte numbers in AZT-treated mice. SCF did not significantly increase hematocrits in either control or AZT-treated mice. Further studies are needed to maximize the differentiating capacity of the enlarged erythroid progenitor cell pool induced by SCF.