CHARACTERIZATION OF MEGAKARYOCYTE SPLEEN COLONY-FORMING-UNITS BY RESPONSE TO 5-FLUOROURACIL AND BY UNIT GRAVITY SEDIMENTATION

  • 1 January 1983
    • journal article
    • research article
    • Vol. 62  (4) , 896-901
Abstract
Properties of megakaryocyte progenitor cells in mouse bone marrow have been examined using an in vivo assay system. Perturbation with 5-fluorouracil (F-FU) and separation by unit gravity sedimention was used to characterize the cell. Bone marrow was assayed for the presence of megakaryocyte colony-forming cells (MK CFU-S) by transplantion into lethally irradiated mice and examining spleen sections 10 days later. Donor mice were untreated or injected i.v. with 5-FU (150 mg/kg), 1 (FU-1) or 7 (FU-7) days beforehand. There was a lack of correlation between the numbers of MK CFU-S and cells giving rise to macroscopic spleen surface colonies (CFU-S10). The sedimentation profile of MK CFU-S in normal marrow was similar (modal velocity 4.16 .+-. 0.05 mm/h) to that of CFU-S10. In FU-1 marrow, MK CFU-S exhibited a bimodal sedimentation profile, with peaks at 3.26 .+-. 0.06 mm/h and 4.53 .+-. 0.07 mm/h. The marrow content of CFU-S10 was reduced to 5% of normal, while MK CFU-S numbers were only reduced to 60%. In FU-7 marrow, the sedimentation profile of MK CFU-S (modal velocity 4.86 .+-. 0.16 mm/h) differed from that of CFU-S10 (5.5 .+-. 0.16 mm/h). MK CFU-S and CFU-S10 are different entities. The MK colonies formed from FU-1 marrow contained on average 3.8-fold more cells than those formed from normal marrow. The enhanced megakaryocyte production may be accounted for on the basis of the generation-age model for cell proliferation. It is proposed that MK CFU-S are a heterogeneous population with regard to proliferation potential and that the FU-1 marrow contains cells that survive 5-FU and have a high proliferative potential. These cells may be equivalent among megakaryocytic progenitors to the high proliferative potential colony-forming cells of the granulocyte/macrophage series. They may be responsible for the enhanced megakaryocytopoiesis seen in the marrow of mice 7 days after the injection of 5-FU.