Lifelong hematopoiesis in both reconstituted and sublethally irradiated mice is provided by multiple sequentially recruited stem cells.
OBJECTIVE
To evaluate the dynamics of stem cell production to hematopoiesis, the number of active stem cell clones and the lifespan of individual clones were studied.


METHODS
The clonal contribution of primitive hematopoietic stem cells (HSC) responsible for long-term hematopoiesis was determined using two approaches. In one model, irradiated female mice were reconstituted with retrovirally marked male hematopoietic cells. In the second model, mice were irradiated sublethally without hematopoietic cell transplantation. In both models, bone marrow cells were serially sampled from the same mouse throughout a 12- to 20-month period and injected into irradiated recipients for analysis of day 10 colony-forming unit-spleen (CFU-S). The donor origin of CFU-S was determined by the presence of retrovirally marked cells or cells with chromosomal aberrations.


RESULTS
The results of the two essentially different models show that 1) hematopoiesis is mainly the product of small clones of hematopoietic cells; 2) the lifespan of the majority of clones is only 1 to 2 months; 3) the clones usually function locally; and 4) the vast majority of the clones replace one another sequentially. Primitive HSCs capable of producing long-lived clones (about 10% among all clones), which exist during the entire life of a mouse, were detected by the radiation-marker technique only.


CONCLUSIONS
Multiple short-living clones (at least on the level of CFU-S production) comprise the vast majority of the active stem cells in transplanted recipients or after endogenous recovery from sublethal irradiation.
Drize
N J
NJ
Hematological Scientific Center, Moscow, Russia.
Olshanskaya
Y V
YV
Gerasimova
L P
LP
Manakova
T E
TE
Samoylina
N L
NL
Todria
T V
TV
Chertkov
J L
JL
D000818:Animals; D001854:Bone Marrow Cells / Q000166:cytology* / Q000528:radiation effects; D002869:Chromosome Aberrations; D003114:Colony-Forming Units Assay; D003433:Crosses, Genetic; D005260:Female; D006410:Hematopoiesis / Q000528:radiation effects*; D018380:Hematopoietic Stem Cell Transplantation; D006412:Hematopoietic Stem Cells / Q000166:cytology* / Q000528:radiation effects; D007621:Karyotyping; D008297:Male; D051379:Mice; D008810:Mice, Inbred C57BL; D008808:Mice, Inbred CBA; D016133:Polymerase Chain Reaction; D012190:Retroviridae / Q000235:genetics / Q000302:isolation & purification; D013997:Time Factors