Clonal analysis of hematopoietic stem-cell differentiation in vivo.
Previous work has shown that the 0.02-0.05% of adult mouse bone marrow cells that bear the cell surface phenotype Thy-1loLin-Sca-1+ are enriched 1000- to 2000-fold for hematopoietic stem-cell activity in a variety of assays. When 50-100 cells of this phenotype are injected into an irradiated animal, they can permanently repopulate the entire hematopoietic system. In the present study, limiting-dilution and single-cell experiments were used to address the question of how individual Thy-1loLin-Sca-1+ stem cells contribute to repopulation of the hematopoietic system following irradiation. We calculated that 1 of 13 Thy-1loLin-Sca-1+ cells formed a clone comprising greater than 1% of peripheral white blood cells 3-7 weeks after injection. The majority of these clones included both lymphoid and myeloid lineages. Approximately one-third of the clones continued to produce new blood cells for 9 weeks or more, but the remainder disappeared earlier, including many that were multilineage. Thus, while the majority of Thy-1loLin-Sca-1+ bone marrow cells whose progeny are detected in the in vivo repopulation assay are pluripotential, only a subset undergo long-term self-renewal in vivo. Repopulation appears to be oligoclonal when limiting numbers of Thy-1loLin-Sca-1+ cells are injected. However, the number of clones contributing to hematopoiesis increases in proportion to the number of Thy-1loLin-Sca-1+ cells injected, bringing into question the notion that steady-state hematopoiesis in normal individuals is oligoclonal.
Smith
L G
LG
Department of Pathology, Howard Hughes Medical Institute, Stanford University School of Medicine, CA 94305.
Weissman
I L
IL
Heimfeld
S
S
D000818:Animals; D000954:Antigens, Surface / Q000032:analysis; D001853:Bone Marrow / Q000528:radiation effects; D001854:Bone Marrow Cells; D016026:Bone Marrow Transplantation; D002454:Cell Differentiation; D002678:Chimera; D002999:Clone Cells; D003114:Colony-Forming Units Assay; D005434:Flow Cytometry; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology*; D051379:Mice; D008810:Mice, Inbred C57BL; D018800:Thy-1 Antigens
D000954:Antigens, Surface; D018800:Thy-1 Antigens