Use of 5-fluorouracil to analyze the effect of macrophage inflammatory protein-1 alpha on long-term reconstituting stem cells in vivo.
A macrophage-derived inhibitor of early hematopoietic progenitors (colony-forming unit-spleen, CFU-A) called stem cell inhibitor was found to be identical to macrophage inflammatory protein-1 alpha (MIP-1 alpha). We investigated the effect of MIP-1 alpha on the earliest stem cells that sustain long-term hematopoiesis in vivo in a competitive bone marrow repopulation assay. Because long-term reconstituting (LTR) stem cells are normally quiescent, an in vivo model was first developed in which they are triggered to cycle. A first 5-fluorouracil (5-FU) injection was used to eliminate later progenitors, causing the LTR stem cells, which are normally resistant to 5-FU, to enter the cell cycle and become sensitive to a second 5-FU injection administered 5 days later. Human MIP-1 alpha administered from day 0 to 7 was unable to prevent the depletion of the LTR stem cells by the second 5-FU treatment, as observed on day 7 in this model, suggesting that the LTR stem cells were not prevented from being triggered into cycle despite the MIP-1 alpha treatment. However, the MIP-1 alpha protocol used here did substantially decrease the number of more mature hematopoietic progenitors (granulocyte-macrophage colony-forming cells [CFC], burst-forming unit-erythroid, CFCmulti, and preCFCmulti) recovered in the bone marrow shortly after a single 5-FU injection. In vitro, MIP-1 alpha had no inhibitory effect on the ability of these progenitors to form colonies. This study confirms the in vivo inhibitory effect of MIP-1 alpha on subpopulations of hematopoietic progenitors that are activated in myelodepressed animals. However, MIP-1 alpha had no effect on the long-term reconstituting stem cells in vivo under conditions in which it effectively reduced all later progenitors.
Quesniaux
V F
VF
Sandoz Pharma Ltd, Basel, Switzerland.
Graham
G J
GJ
Pragnell
I
I
Donaldson
D
D
Wolpe
S D
SD
Iscove
N N
NN
Fagg
B
B
D000818:Animals; D016466:CHO Cells; D002478:Cells, Cultured; D054407:Chemokine CCL4; D006224:Cricetinae; D016207:Cytokines / Q000494:pharmacology*; D005472:Fluorouracil / Q000494:pharmacology*; D006412:Hematopoietic Stem Cells / Q000187:drug effects*; D006801:Humans; D019402:Macrophage Inflammatory Proteins; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D015846:Monokines / Q000494:pharmacology*
D054407:Chemokine CCL4; D016207:Cytokines; D019402:Macrophage Inflammatory Proteins; D015846:Monokines; D005472:Fluorouracil