Traditional bone marrow transplantation models have utilized lethal (myeloablative) doses of radiation to condition the host. In humans, such conditioning is associated with multiple long-term side effects, including secondary malignancies. We have recently demonstrated =50% long-term donor chimerism in C57B1/6 mice transplanted with 20 x 10' fresh B6.SJL marrow cells after irradiation with 160 cGy. Because conditioning with antimetabolite drugs has the potential to further reduce toxicity, we studied 5-fluorouracil (5-FU) as a single conditioning agent. We gave C57B1/6 mice paired doses of 5-FU (150 mg/kg IP) on days 1 and 5, followed by transplantation of 20 x 106 fresh B6.SJL marrow cells on day 6. We observed no apparent toxicity from the conditioning. At 4 months post-transplant, donor chimerism averaged 37.7 ±11.2% (n=9), similar to that seen in 160 cGy conditioned mice. The long-term repopulating ability (LTRA) of paired dose 5-FU treated marrow was estimated using the competitive repopulation assay. Marrow from 5FU treated mice competed only =45% as well as fresh competitor marrow cells. We also examined the phenotype of paired dose 5-FU-treated marrow by flow cytometry. We found that the total marrow cell number and the number of Sea-1 Vlin cells was dramatically decreased by 48-72 hours after the second dose of 5-FU, similar to that observed after 1100 cGy radiation. In the 5-FU treated marrow, 12-25% of the Sca-l /lin cells were undergoing early apoptosis, as evidenced by annexin V and propidium iodide staining. These experiments show that paired dose 5-FU conditioning results in moderate level, stable long-term donor chimerism, and that both stem cell function and stem/progenitor cell number are reduced by paired dose 5-FU treatment. We are currently conducting experiments using paired dose 5-FU as a conditioning regimen for transplantation of retrovirally transduced marrow cells.
|Issue number||11 PART I|
|State||Published - Dec 1 2000|