EFFECTS OF 2',3'-DIDEOXYNUCLEOSIDES ON PROLIFERATION AND DIFFERENTIATION OF HUMAN PLURIPOTENT PROGENITORS IN LIQUID CULTURE AND THEIR EFFECTS ON MITOCHONDRIAL-DNA SYNTHESIS

2',3'-Dideoxynucleosides (ddNs) including 3'-azido-3'-deoxythymidine ( AZT), 3'-fluoro-3'-deoxythymidine (FLT), 3'-amino-3'-deoxythymidine (A MT), 2',3'-dideoxycytidine (ddC), and 2',3'-didehydro-3'-deoxythymidin e (D4T) were tested for their effects on proliferation and differentia tion of pluripotent progenitor cells (CD34(+)) purified from human bon e marrow cells grown in liquid cultures. These highly purified progeni tor cells undergo extensive proliferation during 14 days, with a marke d differentiation during the last 7 days. These differentiated cells e xhibit normal morphological features in response to specific hematopoi etic growth factors of both erythroid and granulocyte-macrophage linea ges, as demonstrated by Row cytometry cell phenotyping. The potencies of these ddNs in inhibiting proliferation of granulocyte-macrophage li neage cells were in the order FLT > AMT = ddC > AZT >> D4T, and the po tencies in inhibiting proliferation of erythroid lineage cultures were in the order FLT > AMT > AZT > ddC >> D4T. The toxic effects of ddNs assessed in these liquid cultures were in agreement with data obtained by using semisolid cultures, demonstrating the consistency of these t wo in vitro hematopoietic systems toward ddN toxicity. ddC was toxic t o CD34(+) progenitor cells and/or cells in the early stages of differe ntiation, whereas the inhibitory effect of AZT on the erythroid lineag e was predominately observed on a more mature population of erythroid progenitors during the differentiation process. Slot blot analysis of granulocyte-macrophage cultures demonstrated that exposure to ddC and FLT was associated with a decrease in total mitochondrial DNA (mtDNA) content, suggesting that these two ddNs inhibit mtDNA synthesis. In co ntrast, no difference in the ratio of nuclear DNA to mtDNA was observe d in cells exposed to toxic concentrations of AZT and AMT, demonstrati ng that the bone marrow toxicity induced by AZT and its metabolite AMT is not associated with an inhibition of mtDNA synthesis. This human p luripotent progenitor liquid culture system should permit detailed inv estigations of the cellular and molecular events involved in ddN-induc ed hematological toxicity.